[CobraMarty]

Where to start?

Me- I have been into cars, upgrades and forced induction for a very long time. I have a ton of experience on several platforms. I have several boosted cars. Always looking for a project and challenge. Time helps matters and being able to make projects and ideas work.

N52- My son and I both own '07 328xi. Him a E92 6MT with suspension mods and basic bolt on engine mods. Mine a E90 Auto with a few mods. They are great platforms to work on, modify and enjoy. Now that the ECU can be tuned, this opens up so many possibilities, especially forced induction.

We are always looking for more performance from these cars. We don't want to trade into the M3 or 335. They can be the 'high HP' Kings. We like taking the 'underdog' and making it into something. Hence the 328 N52. The N52 is one of the most advanced engines with variable cam timing and variable cam lift.

The 6MT and the Auto are two very different driving cars. The 6MT loves to rev and is easy to drive with using the whole rpm range 2-3000 to 6-7000. It is very linear in power delivery and is just what a I6 engine should be. The Auto on the other hand uses the Torque Converter more. It mostly drive in the 2000 to 5000 range. Unless it is in 'manual' shift mode, it is very difficult to get and drive much over 5000. Because of this, different driving rpm ranges, the same engine acts differently depending on it 6MT or Auto.

Supercharging- Centrifugal supercharging is more suited to the 6MT car. It has a very linear boost curve and ramps up the power with increasing rpm. It doesn't make much boost at lower rpm especially in the 2000-5000 rpm range and would not be all that useful for the Auto car. On a 6MT car, the Centrifugal SC will make the N52 feel and drive like a much pumped up N/A BMW engine. Linear power delivery and high rpm range.

Turbocharging- The boost curve can hit early and built boost from 2000 rpm and up. N54 and N55, etc. They make more torque lower in the rpm range than the centrifugal SC. They are better suited to the Auto 328 N52 driving rpm range.

So I have been parallel digging into both the centrifugal SC and the turbocharger ideas. Many of the items cross over to both and can be shared.
I bought a used ESS N52 Centrifugal SC kit and many N54/55 take off parts for turbocharging.

So what have I learned about N52 Turbocharging-

N52/54/55 all have the 'nearly' same intake and exhaust port locations and parts from each can bolt onto the other head. But there are differences and although you can bolt on a N54 or 55 exhaust manifold to the N52, there are other considerations which make it not work.

I have a N52 engine on the stand and have been using it to build off of.
The N55 'Turbofold ' and turbocharger will bolt onto the N52 head but you will need to use a 1" spacer and the block water inlet is located where the turbo sits and requires modification to fit and the A/C compressor sits on that side of the engine right where the N55 turbo sits. So unless you are willing to remove the A/C compressor, the N55 'Turbofold' is a not possible. Bummer as there are a ton of these parts out there and are 'cheap'

So to place a turbocharger on a E9x N52, a custom exhaust manifold/plumbing is required.
A low rear exhaust manifold is possible with a 'small' turbo.
A top mount turbo is 'easier'. BPC and DigiDon both did this.

For the N52, I'm thinking a 'log' exhaust manifold with a low rear mounted turbo is possible.

Collection of N52 Turbocharging Info-

BPC did a top mount turbo on a custom tubular exhaust manifold. They used a 71/63 turbo which can flow 60 lb/min. They used M3 injectors and there own ECU tune. Also used a FMIC. At 6psi, they made 350hp and 300tq. At higher boost they made 505hp and took out 4th gear in the 6MT trans. Had to do a 335 MT swap to handle the higher power.

DigiDon did a top mount turbo IIRC on 'cut off' stock exhaust manifolds and a custom up pipe to the turbo. He used a GT35R turbo, 61/82 or 62/68, 1.08 a/r turbine. He made enough power to 'blow' the trans and require a 335 trans swap. 12psi-461hp/371tq, 15psi-498hp/421tq, 19psi-569hp/500tq and started to lift the head and blow pressure into the cooling system.

The N52 engine held up to the extra power but the trans did not. I am more interested in only adding about 100-125hp to the N52 engine. This will make the car so much more fun to drive and reliable within the boundries of the 6MT and the Auto transmissions.

Turbo Sizing-
Looking at compressor and turbine, inducer and exducer size and power potential. Most just use/quote the 'bigger' number for each
N54- compressor-35.6-46, turbine 40-35.1 Mitsubishi TD03-10TK3 x2, 0.08m/sec, 8.8psi, 300hp and can go to about 450hp
N55- compressor-45.8-62, turbine- 46.1-53 Borg Warner EFR, stock 300hp and can go to a little over 400hp, BW EFR series turbos come with 49.6mm compressor inducer, BMW uses a smaller 45.8mm compressor inducer size

So for the N52 application and comparing Turbo sizes and power-
N54- 46/40 x2 300-450hp 0.08m/sec
N55- 62/53 300-400hp
BPC- 71/63 500hp 60lb/min
DigiDon- 61 or 62/82 or 68, 1.08 a/r turbine, 461-569hp (12 and 19psi)
BW EFR- 62/58 44lb/min, up to 400hp
BW WFR 67/58 49lb/min, up to 450hp

Some Power Numbers, DynoJet Dyno-
Stock 230hp/200tq (crank power)
Bolt On's- 250/210
Centrifugal SC- 300hp/250tq at 6psi non-Intercooled (Thanks Noir)
BPC Turbo- 350hp/300tq 6psi Intercooled

N52 +100-125hp Turbocharger Options-
Smaller turbos spool faster but limit power.
The smaller BW EFR series with integrated WG and BOV would make packaging easier.
So looking at T25 or V-band turbine inlet and V-band outlet, 0.64 or 0.85 a/r, 2.5" compressor inlet, 2.0" outlet, 90* compressor outlet.
Choice is either 62/58 or 67/58.
62/58- smaller, faster spool, to 400hp
67/58- to 450hp

To me, my thinking, the BW EFR 62/58 is the best choice for a reliable street driven 'lower boost' +100-125hp. Especially for the Auto car. It will build boost, 6-7psi from 2000 and provide a significant bump in torque in this mid range 2000-5000 range. Goal would be 350rwhp/300rwtq at 6psi. Not 'a lot' of boost or power but in a daily street driven 328 this will make the car so much more fun to drive and enough power to embarrass a lot of other cars/drivers.

328 N52 Auto Trans-
-6L45, not the best or strongest, to 332 lb.ft. TQ and 5000 pounds 'limit'
-this 'max limit' has some manufacture reliability/longevity factored in, so could tolerate ?10% more power without problems especially in a lighter vehicle like the 328.
-in a 3700 pound 328, it should be able to hold 350-360TQ

That's about all I have for now. I just wanted to get this down and posted so I can throw away all my little scraps of notes.

[Biginboca]

Just wanted to add the manual tranny in the 328i is specified to about 260ft/lbs input torque. So a N/A car with full bolt ons, 3 Stage w/tune, and MILV’s at a possible >240+ ft/lbs is getting pretty close to the limit of the 328i manual transmission.

For many reasons I believe it just doesn’t make sense to F/I a 328. It’s just so much more cost effective to start with a 335 because the transmission, axle shafts, larger diff, etc are already in place. Not to mention you will always sink more $$/time/aggravation into properly converting a 328 to F/I than to trade up to a already engineered for the power 335.

[atmosphericM]

I'm with Big... but I'm also on board with having time on your hands and enjoying a hobby. Heck, sometimes learning about this little car is the only "workout" my brain gets in a week! Force Inducing (yes, I just coined that) an N52 is certainly rare and I can see how it could be satisfying. It would also be incredibly satisfying to put a tuned 335i kid in his place.

It's funny to me.. I bought my 328i not because I had to, but because I wanted the N/A option. 335is was the only turbo option I considered just because it was hard to argue against the power + all of the other goodies they already come with from BMW, plus it's rarer and "special." But F/I is everywhere these days, so it's just not for me. But, to each his own!

GL Marty, can't wait to see what you come up with!

..man, I'd love to be able to "borrow" your shed at times

[W37V]

Wait... Didn't you buy SC while back? Why are you exploring turbo and not installing that SC?

[CobraMarty]

Yeah, doing both.
SC for the 6MT and Turbo for the Auto.
Then there is the Intercooler intake manifold that could be used for both.

[gT-BMW]

If you can find a way to increase lift and duration that would create about 260-280whp in an n52 n/a i would be quite happy with that. But finding somebody to tune would be an issue even with turbo

[W37V]

Originally Posted by gT-BMW

If you can find a way to increase lift and duration that would create about 260-280whp in an n52 n/a i would be quite happy with that. But finding somebody to tune would be an issue even with turbo

Not really. It’s been tried.

Justpete (rip), tested cams and there was not much gain. Tuning was done by BPC. BPC tested pretty much everything possible on this platform. The only thing offering more lift and duration is MILVS.

[Iskan]

Actually DigiDon did a duno. An impressive one.

CobraMarty, I think I’m going to get addicted to this thread.

May the Force be with you!

[W37V]

Based on that 2 sec video digidon posted, it sure looked like he blew the engine at 25psi. Bent a rod.

[rjahl]

https://www.e90post.com/forums/showthread.php?t=1325782

Try this link

[boosthead]

The BW EFR 62/58 looks like the better option for a street driven 6AT. I'd rather have quick spool and great midrange for everyday driving.

[Kubricks]

Nothing to add to this thread, just admiring the dedication of CobraMarty to get everything right. Also agree on low-pressure turbo being a much better match to AT than supercharger.

Good luck!

[CobraMarty]

Welded SS bottom rear mount log exhaust manifold like this-
Except
-It will be one long continuous log, no 'merge collector'
-O2 sensor bungs at cylinder #3 and #5
-the V-band pipe for the turbo would be located back around the #5 cylinder port. It would just be a 'T' into the log. No elbow/merge collector.

[Taskmaster]

Originally Posted by CobraMarty

Welded SS bottom rear mount log exhaust manifold like this-
Except
-It will be one long continuous log, no 'merge collector'
-O2 sensor bungs at cylinder #3 and #5
-the V-band pipe for the turbo would be located back around the #5 cylinder port. It would just be a 'T' into the log. No elbow/merge collector.

O2 feedback is important. Why not have it in the merge like factory and save yourself a headache.

Also, why not use stock style manifold with a Turbo bolted at the bottom?

[CobraMarty]

There is no merge in a log manifold. There is one long tube/log that each cylinder dump into.

The one O2 sensor in the log at cylinder #3 will see exhaust from cylinders 1,2 and 3. Just like the stock manifold.

The other O2 sensor in the log at cylinder #5 will see exhaust from cylinders 5 and 6. So it will see 2 of 3 cylinders. That is as good as it gets because the turbo pipe will be coming off the log between cylinders #4 and #5.

Neither O2 sensor will see exhaust from cylinder #4. That is the problem with a rear mounted turbo and 2 upstream O2 sensors.

Or just take 2 stock manifolds and cut off the converters and weld a horizontal pipe to connect them both and dump into the turbo.

[CobraMarty]

BPC Turbo project-
EFR 7163, Top mount, custom headers, catless downpipe, Open air filter, N54 intake, MILVs, BPC tune

6 pounds of boost- 350rwhp/300rwtq
6psi adds 40% more power from where you start.

Stock- is completely stock
Modified- curve would be in between the two graphs. Headers, 3IM, PI, PE, MILVs, Tune.

Stock- 173rwhp/166rwtq
Modified- 250rwhp/215rwtq
Turbo 6psi- on Modified engine- 351rwhp/287rwtq

[CobraMarty]

N52 ESS Supercharger-
288rwhp/247rwtq

Look at the Boost curve. Very different from the Turbo boost curve.



N52 ESS Supercharger, E40, MILVs, 3IM
297rwhp/248rwtq

[Eagle1oh7]

I wonder if this could also work on the N51.

[CobraMarty]

It should work on the N51. Probably different tuning is all that is needed.

[CobraMarty]

Borg Warner EFR Overview-

B1 turbine housing is smaller than B2 turbine housing
Compressor cover A is smaller than compressor cover B and C
Turbine housing inlet sizes- T25<T3<T4, bigger flow more

Compressor cover A- has 2.5" inlet and 2" outlet, B- 3.5" inlet and 2" outlet and C- 4" inlet and 2.5" outlet

Power-compressor/turbine housing
62/55 A/B1- 375hp
62/58 A/B1- 450hp 44lb/min
67/58 A/B1- 500hp 49lb/min
70/64 B/B2- 550hp 60lb/min, BPC 71/63
76/70 B/B2- 650hp
83/74 C/B2- 750hp
91/80 C/B2- 1000hp

[Echoninety]

Interested in how the Supercharger side of the project turns out. Have fun CobraMarty

[E7J3F3]

BPC had to delete the a/c for their turbo, the top mount that you're talking about, right? I wonder if a small remote mount would work while retaining the a/c. It'd obviously lag worse for the same size, but a smaller turbo could get close. And 6psi max should still be doable. Just spitballing here.