[karimMsalama]

great car

[Malek@MRF]

It's guys like you that gives hope in a sense of community in a car forum. Great write up man! I'm sure that took you some time, but simply awesome!

-Malek

[Steve A]

Best thread ever. you obviously have spent too long talking to Tony

[Alpina_B3_Lux]

Originally Posted by Steve A

Best thread ever. you obviously have spent too long talking to Tony

LOL I'll tell him that

And it's far from finished. Upcoming review items that I've already installed and testing right now (review probably after my first trip on the Nürburgring this year during the Easter weekend):
- UUC Motorwerks short shift kit + DSSR + CDV delete
- ar design ceramic coated catless downpipes
- HJS secondary race cats (100 cells)
- Quaife differential
- M3 suspension components
- STETT charge pipe

To be installed and reviewed in a few weeks:
- STETT cold air intake
- ar design oil catch can
- GIAC stage 2 flash
- Snow Performance stage 3 meth kit

Alpina_B3_Lux

[neo871]

My God! That is impressive, Marcel!

[BayerischeMW]

I'm probably going the Bastuck quad-route myself, so I appreciated your review!

...however this is really a shameless bump for your AR Design catch can review :-)

[Alpina_B3_Lux]

Originally Posted by BayerischeMW

I'm probably going the Bastuck quad-route myself, so I appreciated your review!

...however this is really a shameless bump for your AR Design catch can review :-)

No problem...I intend to write quite a few reviews of my recent modifications, as I have now had the opportunity to test most of them on the Nürburgring. I'll also include the catch can!

Alpina_B3_Lux

[BoostedE90]

And you my friend win that prize! Great write up!!

[Alpina_B3_Lux]

13. Optimization of the exhaust system: Catless downpipes, secondary race cats

• Why?
As already mentioned previously, I initially intended to only use upgraded downpipes from ar design with high-flow cats (300 cells from Magnaflow). However, as time went by and I started reading more and more positive reviews about the GIAC stage 2 flash, I decided to give this flash a try, as I thought it to be a considerable improvement over my current Evotech flash. Now, the GIAC stage 2 flash is intended to be used with a more or less free-flowing exhaust system, as it runs with much higher maximum boost (up to around 18 psi) than the stage 1 (which is more or less identical in this respect to the Evotech flash, i.e. 14 psi). Such increase in boost of course means the turbos need to do more work to create that boost, and if there was much backpressure they need to work even harder to overcome it. In order therefore to minimize backpressure and danger to damage the turbos, it is advised to remove more or less all catalysts out of the exhaust system. For me that meant replacing the catted downpipes through catless ones, and also removing or replacing the secondary catalysts which are located right before the mufflers.

Of course, I could also have left the stock catalysts in place - but a friend of mine (E92Fan) had done this and as a result toasted his stock catalysts after some time, as they could not withstand the high exhaust temperatures resulting from the catless downpipes (and the tune, of course).

So, why not remove the secondary catalysts altogether? Well, I had heard some reports about smelly exhaust fumes that result from this measure, and I also feared that - in combination with my Bastuck exhaust and catless downpipes - the noise level resulting from this would be too much to bear on a daily basis. As a consequence, I chose to replace the stock secondary catalysts with high flow metal catalysts that minimize back pressure but still filter the exhaust gases to some extent and muffle the exhaust noise somewhat.

• How?
As far as the downpipes were concerned, my choice was fairly easy: I had had excellent experiences with the ar design catted downpipes, both from a customer service standpoint and from a fitment and quality perspective. I therefore chose to also order and install their catless downpipes. This time, however, I also went for the option of a ceramic coating; as mentioned above, I had experienced some heat radiating into the driver cabin which may have resulted from the downpipes - and even if not, it is obvious that the turbos create lots of heat in a very limited space that should transfer as little as possible to other engine components.

Here's a picture of the downpipes before the install (sorry, I don't have pictures after the install yet):


For the replacement of the secondary catalysts, the choice was slightly more difficult. I knew the company HJS Motorsport which has an excellent reputation and produce first class catalysts for lots of motorsport vehicles; many car manufacturer and reputed tuning companies use their products. They have two products that could fit our cars:
• Universal, 200 cell metal catalysts (article number 90 95 0040) that cost 370 EUR (+ VAT) - as you'll need two of those, it sets you back around 880 EUR if you live in Germany. They have the advantage that you could have them TÜV approved if you so desire, as they comply with current emissions regulations.
• Motosport race catalysts with 100 cells and platinum covering (article number 90 95 0058 - WRC 1112/10 PE) which cost 560 EUR (+VAT), making it around 1500 EUR for both including VAT. With these, you will not be able to pass emission regulations and therefore they cannot be TÜV approved. However, I would imagine that if you have catted downpipes in addition to those (not catless ones as I have), you should still be able to pass emission testing.
As I knew that I would install catless downpipes anyway, emissions testing was not really a factor for me. The price tag of the 100 cells caused some hesitation, though, but in the end I went with those in order to maximize performance and because I knew that Tony had successfully installed them in his car already.

Here's a schematic drawing of the secondary catalysts with some data in it:


The install went smoothly, as expected with ar design downpipes the fitment was excellent. The stock secondary catalysts needed to be cut out and the new ones had to be welded in place. They are very unobtrusive and look almost identical to the stock ones, so that unless you look very closely and know exactly what you're looking for, you cannot detect the change. I kept the stock cats in case I should need them to pass emissions testing, or should I sell the car (which is unlikely to happen in the foreseeable future).

• Improvements?
After having the catless downpipes along with the secondary motorsport race cats installed, I immediately felt that the car pulled harder, revved more readily up beyond 5000 rpms and felt more responsive. There was an additional edge to it that I hadn't felt before. Unfortunately I can't provide you with exact numbers, as I didn't dyno the car again right after the install. From my very subjective butt-dyno I would say it added around 10-15hp to the car, but that's just a guess. The driving pleasure has certainly increased!

Another very significant change was the sound. The car now sounded much more aggressively, in particular during a cold start-up or when revving it beyond 3000 rpms. When I first drove with it to the underground parking lot of my company, I just revved it up (very slightly!), and the alarm of one of the cars went off. Wow! Really awesome. My garage also told me that from the outside it sounded really great, the best sound they had heard so far of a turbo car. I can second this opinion - when I drive in a tunnel with the windows rolled down it is outright addictive. I'm now looking forward to summer to do that more often! However, the noise is NOT intrusive in the cabin - if I roll the windows up, it's slightly louder than before but not annoyingly so, no perceptible drone and long stretches of driving can still be done quite comfortably.

• Problems / disadvantages?
None - aside from the price tag obviously, if you take both the downpipes, the secondary cats and the install together. Fortunately, I managed to sell the catted downpipes to a member from a forum in Germany (for his 135i), and he's quite happy with them.

[Alpina_B3_Lux]

14. Short shift kit + double shear selector rod + modified clutch delay valve

• Why?
It had been some time since I had the idea of acquiring a short shift kit. I found that the stock shifting experience, if better than in my previous E46, still was not optimal. I was looking for a shortened throw, slight reduction of notchiness and in-gear slop. What's more, the OEM clutch delay valve annoyed me as it was almost impossible to engage the clutch properly when shifting through the gears quickly.

• How?

I therefore did some research on what was available, and first stumbled across the short shift kit from the BMW Performance line. It had the advantage of being OEM material and generally favorable reviews of users who had this kit installed. However, I wondered if there was not something more sophisticated on the market - and it was not long before I learned about the short shift kit from UUC Motorwerks. While reading on their short shift kits and double shear selector rods (DSSR), it became clear to me that they had invested quite a lot of research into their products and had considerably improved the stock shift lever and linkage. Their new short shift kit is called "Evo 3" and boasts 35% reduction in shift travel (100mm from 3rd gear to 4th gear total travel) if stock height is retained (the height of the shifter is adjustable, another plus), and down to over 40% when height is adjusted to the short end of the adjustment range. Also, 100% CNC-machined 303 stainless steel and 6061-T6 aircraft-grade aluminum is used in construction, and not mostly plastic like the OEM parts, while the design still absorbs vibration via the rubber inner section.

Now, what is the DSSR mentioned above? I came across this particular piece when reading on UUC's website. You can find all the details under this link on the UUC Motorwerks homepage, but the main issue is that one significant wear area that has never been addressed is the wear and ovalization of the linkage connection points at the transmission and the shifter's lower pivot. In the original BMW design, the connection at both ends has a large injection-molded plastic bushing, which wears over time and results in additional slop and loss of precision. To permanently fix this, a change in the fundamental design of the pivot is required, changing the assembly to a double shear system that redistributes the torsional forces from the pin/bushing interface to the complete face area on both sides of the selector joint.

Even though I'm by no means a technical expert, the explanation sounded reasonable to me and I thought it to be a good idea to have the DSSR installed at the same time as the short shift kit, in particular as UUC had a package deal going on at the time I ordered both items. Currently, they're available for the 135i, 335i and E9x M3 at a price of 355 USD for the SSK and 129 USD for the DSSR. I find that price to be quite reasonable, as it's still less than I would have paid for the BMW Performance SSK and seemed to be superior in quality to it.

Now, what about the clutch delay valve (CDV)? It is there to minimize stress to the drivetrain by increasing the engagement time of the clutch, i.e. pretty much prevents you from popping the clutch. In fact, it's mainly there to keep warranty costs down for BMW - and if you know how to drive a stick and how to properly engage the clutch, it should be removed as quickly as possible. This results in a more natural clutch feel and enables you to shift through gears more quickly and efficiently, as the engagement of the clutch can be timed correctly.

I ordered the SSK directly from UUC, together with the DSSR and got a good package deal including shipping to Europe. Everything arrived rather quickly and nicely packaged. Here's a photo of it all when I got it:



I do not have any photos of the installation procedure, unfortunately. I had it done again at my favorite installation shop Daum Motorsport who told me that the SSK was easy to install, but that the DSSR necessitated some more work and was more complicated. If you would like to know more about the installation procedure, please see Former_Boosted_IS' excellent review and DIY.

The CDV was also quite easy to install. I went with a modified CDV that looks just like the stock one (you can also just take it out entirely), as I wanted the modification to be as stealth as possible. I got it from (the now defunct) Riss Racing, but you can also order it here on the ar design homepage. Here's what it looks like:




• Improvements?
When I got the car back from the garage and took it out for a drive for the first time, the difference was remarkable. The shifts were noticeably shorter and much more precise, you almost had the impression of having another gearbox, and the UUC DSSR improved the lateral slop. Although the lever is not completely locked in place, the improvement is really considerable. The UUC short shifter height suited me perfectly just how it came from the factory, and it centered just right on my car for neutral.

When driving it for the first time with the SSK and DSSR, I have to say that this is one of the best modifications I have made so far, because you feel it every single time you drive your car. It has a bit the same effect on me as the active steering, which is also something that has immensely improved my driving pleasure on a daily basis. - Some weeks later I had a rental car for some days (as other modifications were done to my car), and when I got back into my car again it was really surprising - you really don't realize how bad and long the shifts on a "normal" car are until you get an SSK. I really feel it connects me better to the car and it's much more fun to change gears quickly and precisely. Also, there is no gear noise whatsoever in the cabin from the shifter at all.

The absence of the CDV is also noticeable, even though it's not an as drastic change as some have reported it to be. I can time my clutch engagement more precisely now, and do not have the feeling that the car does not really do what I want it to do - I feel more in control of the clutch.

• Problems / disadvantages?
I noticed a slightly more notchy feel when engaging gears every once in a while, but it is very minimal and happens in particular when the car is still cold (which happened a lot during the past winter months). The effort it takes to change gears is very, very slightly increased, but it's something you get used to very quickly and it doesn't bother me at all.

Due to the modified CDV it is of course now easier to damage the clutch. But as I've driven manual transmissions all my life and do not intend to drag race my car anyway, that is not an issue that worries me.

All in all the SSK, DSSR and CDV are modifications that I can recommend without reserve and which I believe will increase anyone's driving pleasure considerably.

Alpina_B3_Lux

[E92Fan]

Great reviews Marcel

ps... turbo review is in Add your thoughts!!
http://www.e90post.com/forums/showth...79#post7114979

[TheRox]

Very logical and precise

how very German. Well done! Though I feel its a lot of commitment for a 3 series. (financially and otherwise)

[Alpina_B3_Lux]

Originally Posted by TheRox

Very logical and precise

how very German. Well done!

Thank you! Others had already implied that it's typical for a German to be so methodical. Could be that is true - or it's just an annoying character trait as well! In any case I've made the experience that I get more satisfaction out of things if I do them right, and that means investing some time in research and reflexion.

Originally Posted by TheRox

Though I feel its a lot of commitment for a 3 series. (financially and otherwise)

It certainly is. And much is yet to come!

I can't count the comments any more who tell me that I should have gotten an M3, Porsche or whatnot. But I don't want to! I'm happy with an understated car with loads of power and torque, and I'll keep it for at least 5-6 years, so for me the investment is quite long-time and therefore worth it, as it provides me with incomparable driving pleasure.

Alpina_B3_Lux

[Alpina_B3_Lux]

15. STETT charge pipe & cold air intake

• Why?
Concerning the charge pipe, there have been some reports of stock charge pipes blowing off due to the increased boost pressure of a tuned N54 engine; I wanted to avoid something similar happening if I choose to considerably increase the boost my turbos are running at. For comparison, the stock turbos run at around 8 psi maximum boost, my Evotech flash had a maximum boost of 14 psi and my future GIAC stage 2 flash would have about 18 psi - and this is even without taking into account additional airflow due to upgraded turbos which is also something I intend to tackle in the near future. So, avoiding boost leaks by upgrading the charge pipe seemed a good idea to me! - Secondly, I had heard that a certain charge pipe already features bungs for methanol injection, i.e. openings where a methanol nozzle could be placed without having to drill any additional holes. As I also had the intention of installing a methanol/water injection system (from Snow Performance) in the near future, this was a nice bonus from upgrading the charge pipe.

As far as the cold air intake is concerned, anybody active on this forum has seen the countless threads on intakes. For forced induction cars a good air supply is vital, as a turbo car is in fact just a huge air pump and more air means (in simplified terms) the possibility for more power. Also, the colder the air is the better it is, as colder air means denser air and thus more power at the same boost level and less stress on the turbos. Now, I had already decided not to go with a dual cone intake as I found them much too obtrusive in the engine bay; I also had some doubts that sucking in air from the (usually quite hot) engine bay was structurally speaking a good idea. Now, I know that this is an endless debate and emotions tend to run high in relation thereto, but these were just my subjective preferences. Also, my decision was strengthened when I read Former_Boosted_IS' thread comparing DCI and CAI, the result of which was that a cold air intake provides better cooling than a dual cone intake. Another reason for me in my particular configuration to go with a different intake was also due to the placement of my additional oil cooler: It is situated in front of the radiator and directly below the stock intake pipes behind the grille, partially blocking one of them and potentially radiating heat to the air that is sucked in through them. I did not find that ideal and suspected that this setup could lead to higher intake air temperatures (IAT) or even insufficient air flow for the turbos.

• How?
Although there are several charge pipes on the market for the N54, the choice for STETT Performance was comparatively easy as it seemed to be made of high quality materials and had gathered a number of positive reviews from customers. It is made from 100% 304 stainless steel plus a custom designed throttle body connector that forms a tight seal, and it is therefore highly unlikely that it will come of or produce any boost leaks, when properly installed. Furthermore, it featured the two meth bungs I mentioned earlier, which will come handy once I get my meth kit installed. The STETT charge pipe can also be used with a number of aftermarket diverter or blow off valves, which was also important to me as I had the Forge diverter valves (see my previous review). One should note, however, that due to the fact that Forge has changed the design of their DVs somewhat, I was in need of an adapter for my DVs which STETT also provided. What's more, the adapter was initially in silver, but I absolutely wanted it in black to blend in with my black DVs - and STETT anodized these without any extra charge. Thanks for this! Here's a photo of the charge pipe prior to installation (in silver, though, mine is black), as well of the clamps connecting it to the throttle body:





As to the cold air intake, there is not that much choice available actually. Dinan has just released their CAI which looks nice but is extremely expensive (plus I'm not sure it's compatible with my charge pipe and diverter valves), and Mr. 5 has designed his own CAI. As I had already taken the decision to acquire the STETT charge pipe, it was fairly self-evident to have a look at their CAI as well. Moreover, at the time I was contemplating this, there was a group buy going on which combined both items, and made the decision even easier. Several positive reviews in this forum and a look at the build quality of the CAI on their website also convinced me that it was a good choice. Here's what it looks like prior to installation:



This time, the installation of the charge pipe was done by Birds in the UK (on the same occasion when my M3 components and the Quaife differential were installed), whereas the installation of the CAI was done by Daum Motorsport. Actually, Birds claimed that the CAI would not fit or that in order to make it fit the whole xenon light assembly on the left side of the car would have to be removed and probably modified. Luckily, that was not correct and although it was a VERY tight fit (mainly due to the big air filter), it did fit indeed. Here are some photos of what the engine bay now looks like with the cold air intake (on top) and the charge pipe (mostly hidden, but you can see the chunky black hoses leading away from the diverter valves):

Installation picture 1 (view from in front of the engine bay):


Installation picture 2 (view standing on the left side of the car):


• Improvements?
As far as the charge pipe is concerned, there is not much to say - it looks nice and solid and does its job. I will probably be able to say a bit more once my meth kit is installed and the meth bungs operational as well.

The CAI looks nice too, and it also sounds amazing. You can't really hear the stock intake, but if you push down the throttle now, you can easily hear the CAI sucking in air. It's not an annoying noise, and once you're driving fast it's drowned out by other noises anyway, but between let's say 0 and 80 km/h it is noticeable. I like it very much, it gives the car a nice sporty performance sound. I also have the impression that the car pulls better now, in particular in high rpms. I haven't been able to verify this on the dyno, though - and in any case I think the CAI will be most useful in summer when temperatures are rising, to provide low intake air temperatures. I would somewhat doubt that it really provides an additional 20hp as STETT claims on its website - but an improvement is (at least for me) definitely perceptible.

• Problems / disadvantages?
The fitment of both items in the tight engine bay of our cars isn't obvious, as with other aftermarket items. Another disadvantage is also that it is quite obvious that these are not stock items - so you may want to consider taking it out for any maintenance at the dealership (which is a hassle as it's not that easy to take out).

The main issue I had was however with something else: The inside of the CAI was dirty and rusted, and big flakes were coming off. Had my installation shop not noticed this, the flakes would certainly have damaged the engine as they would have been fed directly into the turbos. A recipe for disaster! Even though I don't think it happens often, STETT should improve their quality control in this respect. Also, I wasn't quite happy with the fact that neither installation instructions nor a shipping list were provided when I received the package, but these are only minor criticism.

In summary, both the charge pipe and the CAI are solid quality products and are a definite improvement over the stock items, in particular if you intend to go with a meth kit or have the ar design oil cooler installed.

Alpina_B3_Lux

[zaheer]

fantsastic review....car must be amazing.

however you mentioned that you have not dyno'd your car after some mods...how much bhp do you think it is pushing out now..approx?

[Alpina_B3_Lux]

16. AR Design oil catch can

• Why?
Ever since I started modifying my car, I have been concerned with its long-term reliability. Some modifications such as the additional oil cooler or even the upgraded intercooler, while enabling the engine to deliver its power consistently and without heatsoaking, also alleviated the thermal stress on the turbos and therefore contribute to its longevity. However, I learned that more or less all engines suffer from so-called "blow-by" gases which are excess gases that leak from piston rings during the combustion process and get back into the engine crankcase; from there they are vented (by crank case vents) back into the intake system of the engine to be combusted again. That wouldn't be so bad, but the blow-by also contains oil from the crankcase, and this is the real problem - the oil coats the intercooler (thus decreasing its cooling efficiency), the intake valves and other engine components, impacting their performance negatively.

Now, this oil should be caught before it creeps everywhere, and this is commonly done by a so-called oil catch can ("OCC"). Its function is to filter the blow-by gases and to extract the oil from them, retaining the latter in a container that is (ideally) easy to drain.

• How?
For quite some time, Riss Racing was more or less the only option for an OCC that was specifically adapted to our engine. However, from what I've read on this forum, the quality of this product was only very mediocre and it had a tendency to leak all over the place, due to the cheap components used in its construction.

As I had so far had excellent experience with other products from ar design, I was glad to learn that Andrew was developing an OCC for the N54. At that time, other competitors (such as the BSH OCC) were not on the market yet, and in my opinion the use of a real 5 micron filter instead of just some steel wool for filtering was a superior solution. Therefore I jumped on the group buy that was organized for this OCC. The price is admittedly not very low (list price is 229 USD), but I am happy to pay more for a quality product that fits correctly than throwing some stuff together myself and be finally unhappy because it does not work right. An additional advantage of the OCC from ar design consisted in the fact that they offered the possibility to mount it on the passenger side in the engine bay, which was necessary in my case as due to the STETT cold air intake and charge pipe I did not have enough space for the OCC on the driver's side.

With some delay, the OCC arrived and was excellently packaged in a big cardboard box. Upon unpacking the various items, I was immediately aware of the heavy, confidence-inspiring solidity of the OCC. Also, the mechanism to remove the filter and drain the oil is really easy and obvious. That was clearly no cheap ebay-like item but a thoroughly engineered solution. All mounting brackets for the passenger side location were also provided. Here's a photo (not mine, I hope the forum member won't mind) of what the components look like once unpacked:



As always, I had the OCC installed at Daum Motorsport and from what they told me it was no problem at all, and they confirmed that all components seem to be of very high quality. It IS a tight fit, and the OCC is quite close to another hose but without actually touching it. However, it does fit into the engine bay, and the mounting brackets provided by ar design had the right size. For additional insight into the installation procedure, I would recommend having a look at
Former_Boosted_IS' DIY of the BSH OCC, as the install is pretty similar.

Once in the engine bay, the OCC blends in very well and if you wouldn't know it, you could think it's an OEM part. It's also easy to access, you can see the reservoir window (i.e. how much oil is in the OCC) and the oil can easily be drained in that position, without having to demount the whole OCC. Here are two photos of what it looks like after installation:

Photo from the side:


Photo standing in front of the car:


• Improvements?
Well, not really much to say here! It is properly mounted, it looks great, and I have no indication that it does not do what it is intended to do. After some thousand kilometers I will drain it and see how much oil it has collected, and update the thread here with the results.

• Problems / disadvantages?
The only two disadvantages could be that (i) it's not cheap (but for me it's worth the amount I paid) and (ii) it's another non-OEM item in your engine bay. However, as these were no real factors for myself, I can happily ignore both.

In summary, the ar design OCC is a high quality product and I can recommend this to anyone who is interested in the long-term reliability of his engine.

Alpina_B3_Lux

[enrita]

great review! we are pretty much on the same modding path

[Alpina_B3_Lux]

Originally Posted by enrita

great review! we are pretty much on the same modding path

Thank you! It would seem so, indeed...

Still have some other reviews in the pipeline, so stay tuned!

Alpina_B3_Lux

[Eyeman]

First time I read these reviews today. Great info and fortunately most of your mods have went well. Many of my mods have had complications. I notice you plan the Quaife soon. If I had to do it again, I think I'd just have my mechanic remove my stock housing/diff and send it to Harold at HPA for the install to make sure someone with experience was doing it.

[whokiid]

just stumbled across this thread this morning.

Great post. Very informative. SOmething id come back to time and time again for reference. Im sure i speak on behalf of all the members when i say thanks.

[Alpina_B3_Lux]

Originally Posted by Eyeman

First time I read these reviews today. Great info and fortunately most of your mods have went well. Many of my mods have had complications. I notice you plan the Quaife soon. If I had to do it again, I think I'd just have my mechanic remove my stock housing/diff and send it to Harold at HPA for the install to make sure someone with experience was doing it.

Thanks for your positive feedback.

In fact, I have the Quaife differential installed in my car since February. I just haven't had the time to write a review on it, but that will come in time. BTW, I went to Birds and had it installed there.

Originally Posted by whokiid

just stumbled across this thread this morning.

Great post. Very informative. SOmething id come back to time and time again for reference. Im sure i speak on behalf of all the members when i say thanks.

Thank you! It is quite a lot of work to put all that together, so it's great to know that this is appreciated.

Alpina_B3_Lux

[Alpina_B3_Lux]

17. M3 suspension parts & Quaife limited slip differential

• Why?
If you want your car to drive faster than it can do in stock form, increasing the power output of the engine is only one part of the equation. If driving faster in a straight line on motorways is your only goal, then this might be enough; however, if your objective is also to be faster around corners, bends or even on a racetrack, then an improved suspension and better traction is a no-brainer.

Let me start by saying that the stock suspension of my car (it's a 335i without M sport suspension) is actually quite good, once you ditch the awful runflat tires and upgrade to Michelin Pilot Sport 2 as I've done (see previous posts). But still, it's a suspension the main objective of which is to make the 335i a fast luxury sedan, and not necessarily to be on the sporty side - pursuant to BMW, that's what the M3 is for. For me, the stock suspension of the 335i has a bit too much body roll in corners, it does not react as fast and precise to steering input as an M3 and does not provide a very good feedback from the road to the driver. You can still drive it quite fast, but you have to sort of guess where its limits are or what you have to do in order to go where you want; I wanted to improve this.

Also, once you increase the engine power and, in particular, the torque, you are faced with another problem: traction! I experienced that, after having flashed my car with the Evotech flash, it got increasingly difficult to transfer the power on the road, the tires spun too easily and much of the desired forward momentum went up in black smoke, decreasing the life span of the tires. This was even more true in corners or in the wet - unless the road is dry, there's wheelspin sometimes even in fourth gear, and even when dry, powering out of bends is near impossible in second or third gear.

Why is that, you may say, doesn't the 335i come with a differential? Well, BMW has labeled a function of its DSC "electronic differential", but that is quite a misnomer: All it does is brake the rear tire that has lost traction, thus decreasing the life span of your rear brake pads but not helping with forward momentum. The 335i unfortunately is not equipped with a limited slip differential as all M models are, for marketing reasons in order to differentiate it from the M3. As a consequence, it has an open differential which means that the power of the engine is always directed to the wheel with the least resistance. In corners, that means obviously the inner wheel as the weight of the car is transferred to the outside - and if you apply full throttle now, the inner wheel starts to lose traction and spin, the DSC cutting in to prevent this, and you get sort of a hickup-driving-style. That's not fun! You can't determine the curve radius with your throttle, you can't drift, and most of all you can't properly apply the power of the mighty N54 to the road. I experienced that on numerous occasions during my trip to the famous Nürburgring in August 2009 and by driving through mountain passes in the Italian Alps, and this led me to the conclusion that a limited slip differential (LSD) was definitely needed here.

What does it do? An LSD senses that a wheel loses traction and transfers the torque to the wheel with more traction. In the example above, if you corner with an LSD, it will automatically transfer the engine power to the outer wheel which is under load and therefore has more traction, enabling the car to apply more power to the road. Such differentials are also called "torsen" (torque sensing) or "automatic torque biasing" (ATB) differentials. They can lock up the normally open differential until 80% (a complete lock would be too dangerous) to enable the torque transfer from one wheel to the other. The effect is typically progressive, making it easy to drive.

• How?
A) Limited slip differential:
There are several limited slip differentials available for the 335i - e.g. from Drexler Motorsport, Quaife Engineering or Wavetrac. Drexler is a "plate type" LSD that uses clutch plates to do the torque vectoring, whereas Quaife relies on gears for their operation. The advantage of the latter technology is that, as there are no clutches that are used, such LSD are almost maintenance free, "fit-and-forget" solutions. For me that was the decisive factor, as I did not really see fundamental advantages of a clutch type LSD (except in motorsport which was irrelevant for me). So then, Quaife or Wavetrac? There's a lot of discussion going on on this forum about the advantages of one over the other. Wavetrac is supposed to work even if one wheel is completely off the ground - but that seemed a rather irrealistic scenario for my driving style, so that argument was of no concern for me. On the other hand, Quaife had a long-standing track record (decades, really) and first rate reputation, in particular for BMWs, and I knew several forum members personally who had it installed in their cars. Furthermore, Wavetrac didn't have an option for a welded differential like mine (I later learned that there may be a workaround, but I wasn't interested in a solution that wasn't perfectly established), so the choice was easy in the end - Quaife.

Now, where to obtain it? If I was living in the US, I would have gone through HP Autowerks as I had already dealed with Harold in the past and was quite satisfied with his services. Being in Europe, however, I was recommended Birds in the UK as they are the European distributor of all Quaife differentials and have unmatched experience in this sector. As I wanted to have other modifications done at the same occasion and wanted to benefit from their experience with BMWs, I combined the installation of the differential with a nice trip to London where I hadn't been for a long time - killing two birds with one stone! You can look up their prices here on their website - due to my welded differential I needed a final drive unit which cost me (installation included) around 1800 EUR. I also thought about obtaining an LSD with a shorter gear ratio which is available as an option (for quicker acceleration), but in the end I thought that it was unnecessary as I'm not into 1/4-mile-racing and wanted to retain a high top speed (unlimited Autobahn! ).

So, last February I took the ferry over the Channel and drove on to Birds whose shop is located in London, not far from the Heathrow airport. They're really nice guys, and I got shown around their shop where several cars were in surgery, the most impressive being a conversion of a Z8 from left- to right-hand drive (wow! ). I was also shown what the LSD looked like and where under the car it would be installed (as I don't really have on-hand mechanical knowledge). - The installation itself was routine for them, and the new LSD went in without any problem.

B) Suspension:
The decision on how to upgrade the suspension was on several levels more complex. Springs? Dampers? Sway bars? Coilovers? Which type of each? I had test driven the Bilstein B16 Ride Control coilover on a similar car to my own last summer in South Africa (thanks to my friend Charles! here's his review) and experienced it as a passenger on Tony's car (see his review under this link), and had been very favorably impressed with this coilover. However, it also was rather expensive (2000 EUR without install), and together with the LSD that was slightly out of my budget at that time.

In the meantime, however, I had discovered that it is possible to transfer a certain number of components of the M3 suspension onto our cars, thus integrating parts of the superior handling characteristics of the M3 onto the 335i. In particular, this link about various M3 components as well as this review had been quite helpful and instructive in this matter. These parts were somewhat less expensive overall and could also be combined with different springs, dampers or the Bilstein B16 coilover at a later date. Also, none of these upgrades (except the sway bars) exist as aftermarket items, making them even more desirable and indispensable if one is really serious about increasing the handling capacity of the 335i. Another plus is that as they are OEM items, so almost no one will be able to tell that they're not stock - something which is rather important to me as my car needs to go through the TÜV inspection at some point in time.

It was mentioned by those who already had these pieces installed that while mounting the LSD, it makes sense to install other parts for the rear axle at the same time, in order to avoid duplicate work later on. It seemed therefore obvious to me that I should have at least all rear axle items installed (rear subframe bushings, rear sway bar, rear guide rods, rear upper links); but (yeah, the mod bug got to me…) in the end I just thought "why not do all the rest too if the car is on the jack anyway?" and added the front axle items as well (sway bar, tension rod, lower wishbone). However, I left out those that needed different dampers (rear lower camber links), as I wanted to change them at a later stage (see above).

I somewhat hesitated as far as the sway bars were concerned, as Birds recommended the Hartge sway bars instead of the M3 ones, the reason being that the M3 ones still induce some understeer while the Hartge ones are stiffer and provide a tendency for mild oversteer. However, I had driven an M3 and found it very well balanced, and a more or less neutral steering appealed to me as I do not want to pretend to have sufficient driving skill to counter any sudden movements from the rear end. Also, the Hartge sway bars seemed excessively expensive to me (around 730 EUR = almost 1000 USD), and I really had to set a limit somewhere.

I obtained all items except the sway bars from HP Autowerks, as I could then be sure not to miss any vital part. However, I have in the meantime tried to put together a list of all parts and part numbers that were used, as a means of reference. Here it is, along with some explanations for each part (some borrowed from the HP website) - no guarantee is given, of course, and these are the parts for an E90/E92 (most words in brackets are the German words for each part):

1. Front anti-roll bar / sway bar (Stabilisator vorne)
Diagram see here)
31352283515 (Stabilisator vorne)
31352283516 (Gummilager Stabilisator Unterteil, 2x)
31352283517 (Gummilager Stabilisator Oberteil, 2x)
31352283037 (Haltebügel Stabilisator, 2x)
31352283441 (Pendelstütze vorne links)
31352283442 (Pendelstütze vorne rechts)
07119904295 (Bundmutter selbstsichernd, 4x)
33326768884 (Sechskantbundmutter, 4x)
That's what it looks like:


2. Rear anti-roll bar / sway bar (Stabilisator hinten)
As delivered the E9x 3 series has excessive under steer and limited roll control. The M3 rear sway bar increases rear roll stiffness by reducing mass transfer forces in corners. That should give the car crisp, quick turn-in response and reduce understeer, making the car feel more planted. M3 anti bars give the driver the ability to rotate the car on corner entry and steer with the throttle when necessary. It also makes the suspension (front or rear) stiffer, which will reduce the grip.
Diagram see here)
33552283655 (Stabilisator hinten)
33552283709 (Gummilager Stabilisator Unterteil)
33552283710 (Gummilager Stabilisator Oberteil)
33552283714 (Haltebügel Stabilisator, 2x)
33556764428 (Pendelstütze, 2x)
07119906077 (Zylinderschraube, 4x)
07119903931 (Sechskantschraube mit Scheibe, 2x)
33326768884 (Sechskantbundmutter, 2x)
That's what it looks like:


3. Tension strut / rod (front) left+right (Zugstrebe Vorderachsträger)
31102283575 (left)
31102283576 (right)
That's what they look like:


4. Lower wishbone / control arms (Querlenker Vorderachsträger)
These add 0.75 degrees of camber, an alignment of the suspension after the install is therefore mandatory. A different xenon light regulation rod is needed (provided in the HP kit).
31102283577 (left)
31102283578 (right)
37142283867 (xenon regulation rod)
That's what they look like:


5. Rear subframe bushings (Gummilager Hinterachsträger)
The soft stock rear subframe bushings are replaced with stiffer, high performance bushings for a more predictable handling and more control.
33312283382 (front, 2x)
33312283383 (rear, 2x)
That's what they look like:


6. Rear guide rods (Führungslenker Hinterachsträger)
Original guide rods were made to deflect under load, a bad thing for good handling and traction. The M3 guide rods are made of all aluminum, a lightweight component thereby reducing wear and tear on other, more critical parts (rear subframe, control arm bushings etc). Each guide rod weighs just over 1.5 lbs making for a total of ~3 lbs for both parts (stock guide rods weigh 2.1 lbs each). Bushing deflection with a rubber material at one end is replaced by a sealed joint for deflection and noise free operation. Bushing deflection is unwanted because it leads to excess suspension movement. This is bad for handling and traction due to constant camber and toe changes. Plus, any power from the engine can take longer to get to the ground because it has to windup the bushing first.
Diagram see here)
33322283547 (left)
33322283548 (right)
That's what they look like:


7. Rear upper links / wishbones (Querlenker Hinterachsträger)
Original upper links were made to deflect under load, a bad thing for good handling and traction. The M3 links are made of all aluminum, a lightweight component thereby reducing wear and tear on other, more critical parts (rear subframe, control arm bushings, etc). Each link weighs just over 1.7 lbs making for a total of ~3.4 lbs for both parts (stock guide link weigh 2.5 lbs each or 5 lbs for both). A weight savings of over 1.5 lbs from the rear suspension.
33322283545 (left)
33322283546 (right)
That's what they look like:


Here's also a photo of all parts before the install:

The installation procedure of most items was (pursuant to Birds) very straightforward, in particular the tension rods, control arms, rear guide rods and rear upper links were really easy to do - take out the stock part, put in the M3 part, basically plug&play. The rear subframe bushings are a bit harder to do, apparently some force is needed to squeeze them in. Due to the LSD that was being installed, the exhaust had to be lowered anyway, so that access to the bushings was provided for. An alignment was done afterwards (this is a must due to the different camber induced by the lower wishbones in the front!), but no complete KDS (there was not sufficient time).

Here are some photos of the installation so you see where at least part of the pieces ended up:







Comparison of stock and M3 subframe bushings:


Unfortunately, it proved somewhat difficult to install the sway bars: Pursuant to Birds, the M3 sway bars did not fit into the OEM endlinks, and the bushings for the sway bars that I provided supposedly did not fit either. For the rear sway bar, Birds therefore fabricated custom bushings by re-machining the OEM bushings; but they gave up on the front sway bar. Now, as several here on this forum have confirmed, everything does fit, even though it's a tight affair and you may have to apply some force to get everything in place. Fortunately for me, my local shop in Germany where I have had all my other modifications done, Daum Motorsport, managed to get the front sway bar installed. I must admit that I was somewhat disappointed with Birds over this (also because they charged me extra for the re-machining which I assume would not have been necessary), but am nevertheless glad it worked out in the end.

• Improvements?
A) Suspension:
Now, let's come to the part that certainly is of most interest to you - how does it drive now? I held off with my review for some time as the weather was really bad and I wanted to spend some time on a race track - the famous Nürburgring - with the modifications to evaluate the changes properly. Here are two photos from the two days during the Easter week-end that I spent there:





Even though the weather was not ideal, I was able to get almost 15 laps done (around 300 km), and have also driven an additional 3000km on normal roads. Immediately upon taking delivery of my car from Birds, the change was very noticeable. The car felt much more planted, body roll in corners was substantially decreased, and it was much more responsive to any steering input. Although even in stock form I didn't have any serious complaint with the steering response (in particular compared to some other cars I've driven in the meantime…), the car felt much sharper, more awake when going round corners, and any slight change in radius was immediately transferred to the road. Combined with the active steering I have, it is really much more fun to drive now! Going around the 'Ring, the decrease in body roll was also noticeable, the car also felt much more stable at high speed cornering (there are some bends on the 'Ring where you are faster than 150 km/h). In general, you have the feeling that you are more connected to the car and, through it, to the road than before. There is less of a "filter" that delays your input and the car's feedback. It now feels more like a sportscar than it did before.

B) Limited slip differential:
The LSD was the most cost-intensive modification I had done so far on my car, and I was therefore quite curious to see whether it was worth the expense. First of all, it's completely noiseless, I could never hear any sound whatsoever coming from the differential, under any circumstance and load condition. I attribute this to the excellent install done by Birds.

As to driving - while driving normally, you don't feel anything different. But as soon as you push the throttle harder, there's no blinking christmas tree in the dashboard, no power cut off through the electronics, just acceleration pushing you into the seats. Under dry conditions, with good tires and off the race track, it's much more difficult than before to get the tires to spin - in a straight line, that's basically only possible in first gear or in second but at very high revs. The biggest difference can be felt in corners: Whereas before traction control cut power and the car hobbled around, now it just zooms along and you can feel how the torque is transferred to the outer wheel. It practically grips the road and pulls the car along, and long bends or motorway ramps are much, much more fun now. That's as it should have been as a factory car, in my opinion. I also believe it's safer to drive, as the situations where suddenly and unpredictably the DSC cuts your power and you're left with a car that doesn't accelerate as it should will be much less frequent.

Of course, the LSD can't defeat physics - when it's wet and the road slippery, wheelspin can still be induced easily, but that's to be expected with a 400+hp rear wheel drive car. However, wheelspin and traction control intrusions happen to a considerably lesser extent. I was able to experience that on the Nürburgring as it was mostly wet there last time - without an LSD, it would have been close to undriveable, with it I could still go quite fast around the corners, as long as I avoided second gear and full throttle in third.

• Problems / disadvantages?
For the LSD, the price tag is probably the first deterrent for most people, at least if they lease their car. If it's your own car, however, it's definitely worth it and I would not consider the price performance ratio to be bad. For installation I would recommend a shop with experience, and that can sometimes be slightly difficult to find; in Germany, for instance, Evotech distributes and also installs Quaife differentials.

As far as the M3 suspension components are concerned, ride comfort will be slightly (and I mean slightly) decreased. This is due to less cushioning in the front, so that you'll get more feedback from the road through the steering wheel; also, the stiffer rear subframe bushings (and upper links + wishbones) lead to a firmer rear suspension, road imperfections will be felt a bit more than before. It's not much, though, comparable to switching from 18 inch tires to 19 inch tires. - Lastly, I also noticed that (probably a consequence of the stiffer sway bars and the LSD) if the rear end slides out, it does so less gradually than before and you have to react quickly, even with DSC turned on - but that usually only happens if you drive like you should only drive on the track, and then you're supposed to know what you're doing.

As a summary, I can say I'm very, very pleased with these modifications and they have transformed the car in a lot of ways. They contribute to my driving pleasure each time I drive a bit faster on curvy roads, and I can sincerely recommend both to anyone who's remotely interested in making his car quicker and more nimble. Thanks also to Tone and Charles for their invaluable advice and help. - Now I'm looking forward to seeing how the Bilstein B16 Ride Control coilover which is just being installed will further change the driving characteristics of my car!

Alpina_B3_Lux