E28 Turbo FAQ

Discussion pertaining to positive pressure E28s.
Brad D.
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Post by Brad D. »

The turbos are Garretts. They use on-center tubine housings. I believe the typical AR on the hot side is a .63. The compressor is a T04E, but I am not sure exactly what trim. I know it's been posted before but my guess is it's around a 57 trim to a 60 trim(pretty sure it's a 60) compressor wheel. I know some also use a GT35 comp wheel. A bit of compressor map matching should help out here.
Jeremy
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Post by Jeremy »

TCD sells real Garrett units, not imitation knockoffs.

Jeremy
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Post by jbd5015 »

this is probably covered in the books you recommended reading, but for those (like me) who dont have them, i found out a good website about turbo charging basics. Its actually the garrett website. Its their whole 'turbo tech' section in the link below.

http://www.turbobygarrett.com/turbobyga ... enter.html

It answered a lot of my basics questions, and is definitely worth a flip through! I understand everything in the 101 and 102 turbo tech sections, but one thing im still confused about is the T04E. Does this have something to do with the housing size? And this has nothing to do with the T3 and T4 mounting patterns correct?

Thanks guys! Doing all the reading i can so ill be able to have a decent conversation at some point haha!

-Jeff
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Post by turbodan »

Skip straight to the turbo tech 103 section. Thats where you get into the meat and potatoes of things. 101 and 102 cover basics like housing A/R and wheel trims, but 103 is the important stuff.

T04E compressors are part of the T4 compressor family. The T04E designation refers to the compressor housing. Common T04E turbos are the 40 trim, 50 trim, 57 and 60 trim. Other T04 compressors are the T04B and T04S families. The housing selection isn't as important as the wheel selection though. The best way to go about that is to start plotting your engine on various compression maps until you find the best fit.

T series stuff works, but it is a little out of date. I like spending lots of money, so I use Garrett GT series turbos. The dual ceramic ball bearing center sections are indestructible and they're much more responsive than journal bearings.
Brad D.
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Post by Brad D. »

T04 refers to the family of compressor wheels. The 'E' refers to the specific cover, or compressor housing, that is on the unit.
Edit - Dan beat me to the punch.
jbd5015
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Post by jbd5015 »

Thanks guys! Also, i know that it is really important to have the turbo chosen before building, but what if i want to change it later?

Say i go for a T04E with a 50 trim, but later on want to upgrade to a T04E 60 trim. Are the actual dimensions of the turbo going to be the same? Or does the increase in the fan size change the turbo dimensions?

I have a feeling that ill be building this kit around a T04E with 57 trim and stick with it though. Itd be great to score a GT-series garrett, but we'll see how things go!

Thanks again guys, ill be sure to check out the 103 section as ive got it bookmarked!

-Jeff
Brad D.
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Post by Brad D. »

Typically you cannot just swap compressor wheels as the inducer diameters are different between wheels and would require a different cover or machining of your old cover. The exducer diameters are also different and possibly the tip height which also may require machining.
IMO, a T04E 57 trim is a bit small for an m30. All of the following maps are plotted out for 350bhp with redline at 6500. You are off into the choke region of the map. No good.
57 Trim

The 60 trim, while not perfect is better suited.
60 Trim

Now, compare this to a T04B 60-1 which is a better match still.
60-1

Now, lets plot a couple of GT series turbos.

Lets look at the GT3582R which is a pretty sweet match and a peak efficiency island of 79%.
GT3582R

And finally the GT40 54 trim compressor wheel which is also excellent.
GT40 54 Trim

I hope this helps give you a visual idea of the usefulness of compressor maps and what a good match looks like plotted. It also lets you visualize a compressor that is too small.
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Post by turbodan »

Those maps look like they go to 45 lbs/min, so that'd be at least 450bhp, correct?
Brad D.
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Post by Brad D. »

I just used their mapping program to rattle those off and ya, I think they are a bit high in practice. Not my favorite, but I was in a hurry. The rule of thumb of bhp=lb/minx10 usually holds pretty true.
Their x axis airflow calcs are using BSFC in the equation:
measured in lb/min, airflow = (HP target) x (air/fuel ratio) x (BSFC/60) where BSFC is lbs fuel / (hp x hr) instead of just raw airflow values. I think I used a BSFC of .55.
jbd5015
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Post by jbd5015 »

Great info! Thanks for the visualization of it. Ill do a little more reading on the compressor maps to get a better understanding of how to read them.

Thanks again!

-Jeff
George
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Post by George »

Hey Jeff, I'm using the T04e-60. I haven't turned up the boost high enough to push the limits of the compressor.... but I can make boost below 2k rpm and I'm seeing 10psi around 3K.

Power still builds linearly to 6.5K rpm. Its a good turbo for the cost. If I tear it apart in the future I'll go with the GT series but for a first attempt its given me nothing but smiles.

Remember another thing to consider when plotting the compressor map is the engine's compression ratio. The higher compression ratio, the lower the boost threshold will be.
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Post by turbodan »

For any reasonably sized turbo, you should fully spool by peak torque.
Brad D.
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Post by Brad D. »

turbodan wrote:For any reasonably sized turbo, you should fully spool by peak torque.
Absoulutely true.
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Post by alijonny »

can someone post what I need to get for the Megasquirt setup? I went on the MS site and noticed many options and have read here and there about a board that gets integrated to the factory computer...does this sound right? I tried the search function, but could not come up with previous posts about the system. thanks!
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Post by Brad D. »

alijonny wrote:can someone post what I need to get for the Megasquirt setup? I went on the MS site and noticed many options and have read here and there about a board that gets integrated to the factory computer...does this sound right? I tried the search function, but could not come up with previous posts about the system. thanks!
I am working on a MS FAQ and it will have all the info you need. It will be up this weekend. If you need it sooner PM me.
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Post by ldsbeaker »

Big Bronze Rim wrote: I am working on a MS FAQ and it will have all the info you need. It will be up this weekend. If you need it sooner PM me.
Speaking of MegaSquirt...
I was trying to look at coilpacks as an option to replace the distributor. Is this only an option with aftermarket engine management, or can you run it off your motronic? I'm thinking that you have to have something like MS, but I couldn't find any conclusive posts/threads. Would probably do MSD Coil and box, too.
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Post by turbodan »

Motronic can't run anything but a single coil and a distributor. It works with an MSD box, but thats still just using a single coil and a distributor.

Wasted spark, coil on plug, etc. are standalone options only.
Brad D.
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Post by Brad D. »

turbodan wrote:Motronic can't run anything but a single coil and a distributor. It works with an MSD box, but thats still just using a single coil and a distributor.

Wasted spark, coil on plug, etc. are standalone options only.
Well put.
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Post by deucestudios »

Great write up, it's much appreciated.
I really can understand most of this, but when it gets down to numbers, fuel maps, compressor maps... That's where I start to get overwhelmed. I really feel like I could get out there and do this (once the money tree blooms) but it's the tuning that concerns me. Mostly because tuning, or I should say a good tune, seems to go hand in hand with the understanding of the maps. I mean, I'm comfortable turning a wrench, mocking up and welding the 3" exhaust, but I aint got dem der book smarts...
So how far in depth do you (or should say I) really need to understand the calculations behind the scenes? Is that something I really need to wrap my mind around before I start planning a build? I don't want to be the guy that's posting about wanting 300hp, and no clue what the corresponding injector or compressor size is...
Dammit, that's what I'm doing right now.

I digress... thanks for the post.
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Post by George »

deucestudios wrote:Great write up, it's much appreciated.
I really can understand most of this, but when it gets down to numbers, fuel maps, compressor maps... That's where I start to get overwhelmed. I really feel like I could get out there and do this (once the money tree blooms) but it's the tuning that concerns me. Mostly because tuning, or I should say a good tune, seems to go hand in hand with the understanding of the maps. I mean, I'm comfortable turning a wrench, mocking up and welding the 3" exhaust, but I aint got dem der book smarts...
So how far in depth do you (or should say I) really need to understand the calculations behind the scenes? Is that something I really need to wrap my mind around before I start planning a build? I don't want to be the guy that's posting about wanting 300hp, and no clue what the corresponding injector or compressor size is...
Dammit, that's what I'm doing right now.

I digress... thanks for the post.
I can certainly understand the frustration. I'm an engineer and I still get confused and frustrated simply working out the numbers. Anyone on here who has tuned their own system will know that there is no "perfect" size for anything. whether it be injectors, compressors, exhaust size, whatever. What you need to do is first set a goal. Your goal should be to make X amount of power while spending Y amount of money. From there, you can go through the different stages and aspects of the system (with the help of everyone in the F/I section) and find a good range to be. Once you know that range, you can start selecting the components that fit into that range.

If your building your own system from scratch, the more planning and understanding there is from the beginning, the less headaches there are in the future.
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Post by Gunni »

To keep this within the FAQ as it´s related to M30´s specifically.

At what torque output(cylinder pressure) level would one expect head lifting to occur on a B34 with stock headbolts?

M20´s seem to show head lifting to occur around 250-300lbs of torque from what I have seen.
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Post by turbodan »

I was making 360 ft-lbs uncorrected with the stock M20 head gasket and bolts. It put up with over 400 ft-lbs for a few more months before it blew the HG.

Its really more of an issue with detonation than power output. I guess thats the moral of the story.
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Post by Gunni »

Ok, let´s put that down as a known fact for information seekers.

If anybody has similar known knowledge about the M30
then that´d be great.
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Post by Gunni »

Any thoughts?
when does the M30 head start to lift
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Post by T_C_D »

Gunni wrote:Any thoughts?
when does the M30 head start to lift
I made 375rwtq with an untouched engine. Drove many many miles. 20 runs at the dragstrip. Then it blew when I upped it some more. The day it died it made 417rwtq on the dyno.
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