LMM: S371 to S475 conversion.
- Thread starter Dragbear
- Start date
Where did you measure it? The inducer or exducer? There are other shops that have recently been putting Chinese gt50 turbine wheels in s400's too. A 50's turbine is 100x91
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That being said , Kaleb from Black out told me that almost half of the trucks coming into his shop had intercooler cracks that only show up under pressure checks , you might be onto something Isaac !
If you are going to change turbines/housings you really should run a 87/80 with a .90 or 1.10. I would lean on 1.10 if you want more top end power out of it.
From what I've heard from other turbo builders (not going to throw anyone under the buss but they are reliable and authentic) that is the case. There have been more than a few guys running Taterbuilt chargers that have Chinese components. Friend of mine's S478 from Taterbuilt has a Chinese turbine wheel. We've never measured it but it doesn't look like a standard borg profile.
I'm not really knocking the Chinese part. We've had 4 precision gt50's that have had Chinese tw without a problem. If turbo builders had to buy Garrett wheels, the charger would be unaffordable.
If your looking for a little more than the standard Borg wheels are capable of, it definitely is a better wheel. Not sure about choking it in a tiny housing though. But there's really no way you could drive on road with a standard gt50 exhaust housing. All the ones we had(.96, 1.08, & 1.39) were undivided open volute big suckers.
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If your looking for a little more than the standard Borg wheels are capable of, it definitely is a better wheel. Not sure about choking it in a tiny housing though. But there's really no way you could drive on road with a standard gt50 exhaust housing. All the ones we had(.96, 1.08, & 1.39) were undivided open volute big suckers.
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Yea the fist thing I did after the install was pressure test the boost side to 20psi.
My S371 only ran 2 or 3 psi on the street along with the factory vnt .
My S371 on a pull at 3600 RPM would run 42 boost and 57 drive.
At 2800 it was 52/52
At 3900 it was 31 boost and 71 drive
I wound this S475 up to 4500 and it did the same thing 30 boost and 70 drive.
My S371 only ran 2 or 3 psi on the street along with the factory vnt .
My S371 on a pull at 3600 RPM would run 42 boost and 57 drive.
At 2800 it was 52/52
At 3900 it was 31 boost and 71 drive
I wound this S475 up to 4500 and it did the same thing 30 boost and 70 drive.
It makes that boost/drive ratio because the turbine isn't driving the compressor hard enough.
I've seen many 476/87/1.10 chargers make gobs of power and run pretty darn good boost/drive ratios. Friend of mine made 55-60psi on a 476/87/.90 with 100s and a single 10mm. His drive wasn't far off.
Something is wrong with your setup or tuning, IMO. I have a S371 and I see more boost than that even with my big cam and Wagler heads, and this is on the street with a smoke-free tune. If you were running a big tune, you should've seen in excess of 60 PSI out of the S371. Been there, blown up a S371 in the process. (They don't like to run 60+ PSI on hills for more than a couple seconds, especially at altitude. Seems to survive 50 PSI, so far.)
Even with the tight .90 AR on the S475, you should be flowing enough to get the boost up in the midrange. I presume this is an ungated install?
If you have 70 PSI of backpressure, it should be spooling the turbo. Besides a tune being WAY off somehow, I don't know why it isn't working for you. Assuming no major boost leaks, of course.
Did u go from a 4" intake on the s300 to a 5" with the s400? And is the tuner aware of that?
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Yes 5" intake
No change in tune yet. Need to get a data log to tuner.
I already discenagrated the compressor on one S396 from over speed. Use to run 3rd gear start all the way at 3900rpm. I run 4th gear start all last year at 3200rpm. Made a lot more power and turbo was much happier. As soon as the drive pressure got up around 70 psi you could feel the power drop off.
No change in tune yet. Need to get a data log to tuner.
I already discenagrated the compressor on one S396 from over speed. Use to run 3rd gear start all the way at 3900rpm. I run 4th gear start all last year at 3200rpm. Made a lot more power and turbo was much happier. As soon as the drive pressure got up around 70 psi you could feel the power drop off.
That isn't helping your issue, get a tune update. The tuner shouldn't require any sort of data log to update your MAF table for a 5" intake vs the 4" that was on there. If your tuner requires a data log for that you may have other underlying issues.
Mark @ Danville shouldn't need a data log to update the MAF table.
The reason you NEED a tune update is because your MAF is now farther away from the center of the air flow.