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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Journal: N54 Total Engine Rebuild & Upgraded Internals



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      01-02-2011, 02:48 PM   #199
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Originally Posted by BrianMN View Post
You're not going to get any useful info from mounting an EGT gauage in the HPF exhaust, or downpipes for that matter. If you want to get any valuable data, you'll have to mount it in the exhaust manifold pre-turbo.
EGT is POST turbo?? How are you gonna measure post turbo temps before the turbos?
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      01-02-2011, 03:07 PM   #200
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Brian is right, there is about a 500 degree F diff. between mani and post turbo/dp. also the values are skewed post turbo because of the turbine, putting the egt in the mani, which of course is a harder task, gives you very accurate readings, and will tell you much sooner if you're running into trouble. cylinder 6 runs the hottest afiak, putting the probe in the 6 exhaust runner is your best bet!
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      01-02-2011, 03:13 PM   #201
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Brian is right, there is about a 500 degree F diff. between mani and post turbo/dp. also the values are skewed post turbo because of the turbine, putting the egt in the mani, which of course is a harder task, gives you very accurate readings, and will tell you much sooner if you're running into trouble. cylinder 6 runs the hottest afiak, putting the probe in the 6 exhaust runner is your best bet!
Gotcha, ya learn something new everyday...I guess I will consider this when I get an upgraded manifold. I believe we will see a redesigned performance manifold coming from aftermarket companies soon. the need for them will only increase as the HP/TQ(upped turbo/turbos) demand is growing...
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      01-02-2011, 03:42 PM   #202
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I've now got uncomfirmed information that E92fan have not been using methanol injection. If this is correct it is less to worry for meth-users with upgraded turbos. Let's wait and see what E92fan will say.
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      01-02-2011, 04:09 PM   #203
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EGT is POST turbo?? How are you gonna measure post turbo temps before the turbos?
The primary And general use for an EGT sensor is to measure cylinder temps...not sure where you got the notion of monitoring turbo temps, ive ever heard of people concerned about turbo temps. Cylinder temps are much more necessary to monitor When tuning or even just driving hard. If you have the equipment to put more EGT sensors on, I'd probably put another in the front manifold first, then one in the downpipe...but you really aren't going to care about post-turbo temps
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      01-02-2011, 05:39 PM   #204
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Quote:
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The primary And general use for an EGT sensor is to measure cylinder temps...not sure where you got the notion of monitoring turbo temps, ive ever heard of people concerned about turbo temps. Cylinder temps are much more necessary to monitor When tuning or even just driving hard. If you have the equipment to put more EGT sensors on, I'd probably put another in the front manifold first, then one in the downpipe...but you really aren't going to care about post-turbo temps
Aight thanks
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      01-02-2011, 07:22 PM   #205
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Forged pistons are well known to expand a lot more than cast items. I guess BMW did not designe the N54 to withstand the abuse from upgraded turbos but instead designed it for as little piston and ring wear as possible and to get the engine reasonable quiet.
Not necessarily true - it depends on the type of material used in the piston.

Old-era pistons were notoriously brittle and susceptible to expansion due to the poor alloys used. Hence there used to be a large piston to wall clearance to allow for the expansion. This was regardless of whether the pistons were cast or forged. In those olden days, the cast pistons were better than their forged equivalents, due to the fact that their multiple-piece molds allowed for intricate contours inside and out, resulting in light weight, good expansion control and predictable heat flow through the part. Forgings in comparison were crude, heavy (because of the lack of sophistication in intricate contours) and also made to be loose in the cylinder due to the poor quality of alloys. Forged pistons in those days were dimensionally unstable.

Matters were made worse when silicon was eventually added into the alloys used to manufacture pistons - cast piston manufacturers got hold of the silicon technology first and then the case for cast pistons became even stronger. Forged pistons in comparison did not use silicon in the alloy mix until much later on in the life of the technology. Silicon gives the pistons natural lubricity and limits heat expansion. All modern pistons have silicon in them and cast pistons have historically had the most, with some even having as much as 25% silicon by volume. However there is a disadvantage with silicon - it makes the piston brittle. If you drop a modern cast piston, it would probably crack.

Forged pistons are inherently stronger than cast pistons, given the same material structure, because the forging process compresses the alloy's molecules therefore making the material more dense than a casting. Forged pistons also typically use less silicon content, therefore making the piston less brittle. The result is a piston that can better withstand forceful detonation, and hence why forged pistons are generally used in turbo engines because they can withstand the force of combustion. Advancements in alloy technologies has now resulted in a silicon/nickel mix that when combined with the top alloys available allows for forged pistons of the very highest quality, at least as dimensionally stable as typical cast pistons, and therefore ideally suited to ultra high-performance turbocharged engines.

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This is correct, they are more stable to higher temps(max temps, so they dont deform, expand which cause excessive wear) and cast is a molded piece of metal. The stockers need a lower compression tho, IMO. I will be getting forged lowER compression pistons when its time for it.
Hence why I have gone to a 9.5:1 ratio as opposed to the standard 10.2:1

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I've now got uncomfirmed information that E92fan have not been using methanol injection. If this is correct it is less to worry for meth-users with upgraded turbos. Let's wait and see what E92fan will say.
Correct, I don't run methanol at all. I will never have it in my car, because it's too dangerous for me to be driving hard around the 'Ring with the methanol potentially running out with the engine under full load... I'd need a baffled methanol tank, level warnings etc etc..

Does anyone know how much of a difference to cylinder head temperatures (and piston temperatures) methanol makes? Just curious...

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The primary And general use for an EGT sensor is to measure cylinder temps...not sure where you got the notion of monitoring turbo temps, ive ever heard of people concerned about turbo temps. Cylinder temps are much more necessary to monitor When tuning or even just driving hard. If you have the equipment to put more EGT sensors on, I'd probably put another in the front manifold first, then one in the downpipe...but you really aren't going to care about post-turbo temps
Exactly right EGT sensors are being installed during the rebuild, as are sensors in the intake manifold and also pressure transducers either side of the intercooler to measure pressure drop across the Code3/Spearco unit I'm using (same as the Dinan unit)
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      01-02-2011, 10:12 PM   #206
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Exactly right EGT sensors are being installed during the rebuild, as are sensors in the intake manifold and also pressure transducers either side of the intercooler to measure pressure drop across the Code3/Spearco unit I'm using (same as the Dinan unit)
That's awesome you're going to be putting in extra sensors...I really look forward to seeing some of that data! Please share some of your findings when you get that running! Not sure if you have bought the intercooler sensors yet, but Grainger has really good deals on all-in-one temp/pressure/force sensors.
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      01-02-2011, 11:03 PM   #207
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Great thread, subscribed! Love to tear engines down, and love it even more when someone else is doing it!
I'm a latecomer to the thread, and did read all 10 pages but don't recall discussions in regard to two points. First, it looks to me that the chunk which is missing out of #5 slug is actually melted out due to blow by in an area where heat concentrated. Second, on that same #5, are the oil rings free? The compression rings obviously are but the scrapers look stuck in place.
It also looks like what you describe as scoring is very unusual. Normally I would expect to see more of the cross hatching gone in the same vicinity if it were the kind of scoring I am used to seeing. My theory is that you built up guck and micro particles on the oil rings and they transferred abrasion over to the cylinder wall. Look closely at the cylinder pics and you will see that the black varnish extends down to the level of where the oil rings are. This is much lower than usual, it ends at the uppermost compression ring in my experience.
Is the block going to be bored? Or just honed? If honed I would have to call them scratches and not scoring.
I have a theory in regard to the valve stem deposits, I am still thinking it through.
I've enjoyed the civil discussion in this thread, with its very knowledgeable contributors.

Last edited by DSXMachina; 01-03-2011 at 08:53 AM.
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      01-02-2011, 11:26 PM   #208
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For some reason I can't edit my post so will add to it here.
One theory about the valve stem deposits is this: Your compression rings never seated properly. They allowed excessive combustion gasses to leak past the rings, this eventually seized the oil rings in the lands rendering them ineffective. This allowed oil to remain on the cylinder walls and burn to an excessive amount. Meanwhile the downflowing gasses overheated a thin spot in the piston skirt and melted it out. The gasses continued to the crank where the EGR system extracted them. The quantity overwhelmed the EGR system and excessive amounts fed into the intake. These condensed on the relatively cool valve stems and just continued to build up.
It seems that if they are tested for hydrocarbon content in a spectrometer that their source could be determined; the cylinder directly via the opened intake valve, the cylinder via the crankcase and EGR system, or oil sucked into the intake plenum from the turbos and the...hmmm, somewhere else.
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      01-03-2011, 10:08 AM   #209
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Quote:
Originally Posted by BrianMN View Post
The primary And general use for an EGT sensor is to measure cylinder temps...not sure where you got the notion of monitoring turbo temps, ive ever heard of people concerned about turbo temps. Cylinder temps are much more necessary to monitor When tuning or even just driving hard. If you have the equipment to put more EGT sensors on, I'd probably put another in the front manifold first, then one in the downpipe...but you really aren't going to care about post-turbo temps
Hi Brian. There is a simple and fairly effective way to infer cylinder temperatures though it takes a little work. There are color changing paints which can be applied to the underneath surfaces of the pistons. When specific temperatures are reached the paint makes an obvious color change.

This can be used, for instance, to get an idea of whether fuel mix or timing changes are likely to cause piston damage. It would require that the oil pan be dropped after a run and the pistons be examined with a borescope, but that is not a big deal and it gives irrefutable evidence of what kind of heat is being generated and transferred. Those figures would indicae what is going on a few centimeters above the paint (inside the combustion chamber).
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      01-03-2011, 12:59 PM   #210
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Thanks for a lot of great info E92fan. Running the N54 well above 400 whp without meth support is a challenge but I guess it may work fine for you with reduced CR and better components. As long as the piston to cylinder wall clearance is sufficient.

I don't know how much meth injection will reduce the combustion temperature but I believe it is significant and more importantly, it is a true octane booster that works and allows for more ignition advance/power. I guess you can find some information about the cooling effect if you search on the Internet or ask the meth system suppliers directly. If you want to study this historically you can start here http://www.labontemotorsports.com/ontrack/nacawr.pdf and move on from there
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      01-03-2011, 01:28 PM   #211
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Hi Brian. There is a simple and fairly effective way to infer cylinder temperatures though it takes a little work. There are color changing paints which can be applied to the underneath surfaces of the pistons. When specific temperatures are reached the paint makes an obvious color change.

This can be used, for instance, to get an idea of whether fuel mix or timing changes are likely to cause piston damage. It would require that the oil pan be dropped after a run and the pistons be examined with a borescope, but that is not a big deal and it gives irrefutable evidence of what kind of heat is being generated and transferred. Those figures would indicae what is going on a few centimeters above the paint (inside the combustion chamber).
Yeah that would be a great idea for the hardcore guys..but a bit too much work for me to do on a regular basis. I wouldn't mind using one of these temperature strips: http://www.oemcycle.com/Item/product/5036/I've had them on all my race engines and they do a good job of monitoring cylinder/water temps, but obviously don't give real combustion chamber temps which is the most important.
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      01-11-2011, 04:11 PM   #212
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After looking at the pictures the crank looks exactly like I would expect after having been run at the ring. I had a comp Cobra (CSX 3014 for those who are interested.) that I completely rebuilt and tracked a few times. I pulled the engine down after a while and that is exactly what my crank looked like. Remember, this was one of the Cobras that was raced and it had the correctly baffled oil pan but they still run shy of oil in long turns. If I were going to track a car I would not do it unless I installed a dry sump system. They add weight, complexity, and cost money but it is really the only sure way to get oil to the bearings at all times.

The deposit on the valve stem could be caused by a valve stem seal that was not completely doing its job. That being said, you have to have some oil or you will ware out the valve guides. That one was probably allowing slightly too much.

The piston skirts look OK to me. They always seem to ware in that area to some extent.

The cylinders are not excessively worn as is evidenced by the hone marks still showing in the cylinder walls. The vertical lines however look like a lack of oil or perhaps some dirt went through the engine.

Just my 2 cents.

Sam

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      01-20-2011, 12:49 PM   #213
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Cast pistons and forged pistons

I could be wrong here and everyone's made a lot of valid points.

From what i understand, temperature resistence and tolerance is purely based on the material used.

The big improvement is the fact that when something is forged, the material is better BALANCED. Strength comes from the balance.

With something forged, if you cut them up into even sized pieces (like a piston), each piece will weigh within a similar weight of each other. Cast parts don't have that sort of balance and DENSITY. When the density is about the same, the thermal expansion is controlled better. Like all metals when they heat up and cool down, things will always change but when something is cast or forged, those properties will vary.


Someone correct me if i'm wrong!
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      01-24-2011, 09:02 AM   #214
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E92 fan, please tell me you are going to deck the block and heads before putting the motor back together. I say that as I see you are posting pics of the prepped parts but it looks like someone simply took steel wool to the top of your block

Don't want to see any cut corners on this build, as you seem to be spending a pretty penny to do it correctly

What are you doing for headgaskets/sealing? Just running another OEM gasket? Don't know how much you plan to squeeze this build...

On a curious note, do you have the compression height and rod length? I'm also curious as to the rod journal size and pin diameter too, if you don't mind sharing. They should be on your spec sheets.

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      01-27-2011, 09:18 AM   #215
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I've read almost all of this thread and judging by how the car is used I don't believe the cylinder scoring is THAT bad. Afterall the cross hatching is still readily visible.
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      02-19-2011, 09:32 AM   #216
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updates?
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      02-19-2011, 01:34 PM   #217
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Updates will be coming in the next couple of weeks... am opening a restaurant in three days time and that's taken over my entire life!
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      02-22-2011, 10:43 AM   #218
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Updates will be coming in the next couple of weeks... am opening a restaurant in three days time and that's taken over my entire life!
But it's certainly worth it.

Looking forward to the food and the car!

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      02-22-2011, 01:06 PM   #219
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yeah good luck on both!!!!
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      02-22-2011, 03:25 PM   #220
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Good Luck Tony will have to visit
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