Then you will be ready for lower gears 33" tires and 4th gear 
Thats when things start to get interesting:coolspot:
Thats when things start to get interesting:coolspot:
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Big Turbine Wheels
- Thread starter bullfrogjohnson
- Start date
I have an S475 with an 83mm turbine and a .9 housing. Everyone I've talked to that has experience with Garretts thinks that a .9 housing is WAY too tight. But you can't compare a GT42's AR to a 3" S400, they are two different animals. Anyway, mine stays at 1:1 up to 60 PSI then the drive pressure continues up to 80PSI while boost settles at 62PSI. Response and spool up on the street is awesome, I wouldn't hesitate to tow heavy with it - at 2000 RPM I can make the boost gauge bounce with my right foot. I looked at the gauges as I crossed the 300' mark at OBX and I was at 62 PSI boost and 80 PSI drive. For sled pulling the tight housing is awesome. Drag racing the bigger housing would give me more power in the higher RPM and I'm going to test a 1.0 housing on it at both pulling and the track to see which I want to go with permanently. If I still want more flow I'll step up to an 87mm wheel in a .9 housing and may step up to an S480 at the same time.
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I agree with you on the A/R thing. Borg stuff seems to be about .1 losser than Garrett stuff of the same number. The S475 and GT42 are very simalar. I actually had a buddy test them the same day on dyno with his tractor engine. The S400 was a little quicker lighing and was good for about 50hp less then the GT42. Drive pressure ratios have alot to do with RPM. I can make 60 psi of boost at 3000rpm withjust over 60psi of drive but at 4000rpm my drive jumps way up. A looser housing did not fix it. Simply the flow of the turbine wheel is over come. The S400 83mm turbine flow just sligthly less then the GT42 turbine.
Now all that said everybodies drive pressures will be different. Cams, heads, and tuning can make a difference in drive pressure.
I am leaning hard toward the 87mm turbined S480 myself.
Sounds exactly the same as how mine does. Thanks for the info, guess I may not even waste my time testing the 1.0 housing that I have and may just go straight to the 87mm wheel. I think part of what is keep the drive pressures where they are is all the air flow improvements I have throughout.
Why not run a divided housing with a flapper valve to block one section of the turbine till it gets wound up. Then when you hit a given rpm/boost/drive pressure the valve opens and she has full flow through a huge charger?
Supra guys have been doing it for a while on those little 6 bangers with GT47 and 55 size turbos.
Supra guys have been doing it for a while on those little 6 bangers with GT47 and 55 size turbos.
Has anyone heard more about these custom garrett turbos from precision turbo? I like the sounds of the 3" gt42 cover mated to the gt45 turbine side. I also have been keeping and eye on these bullseye power S400's!
I know of a few diesels that have these quick spool flanges, they seem to like them really well. It will help with quicker spool up on a larger charger but it doesn't do anything for high drive pressure at RPM/
What do you mean? I'm not talking about a blocker flange, but an actual valve that closes off one side, then opens it for full flow at a given point. Shouldn't hurt drive pressure one bit.
I have seen those before. Good idea. I wonder how they handle diesel soot. The other issue is that you would need to put an undivided spacer underneith it or you would one side would have no place for it exhaust to go.
Correct, you can not use a divided inlet/header. It needs to be completely open prior to the valve.
These guys run lots of leaded race fuel through their cars so I don't think diesel soot would post too much of an issue.
If you're curious give Chris @ sp a call. He's a good guy and i'm sure would be interested in testing some out on diesels, if it will fit.
That's the exact part I was talking about. I didn't say it would have a negative effect on drive pressure, only that it wouldn't do anything for a drive pressure issue at RPM. Which is what some of the guys were talking about. Sorry for the confusion.
We have done this around here for tractor guys. Basicly you take the turbine wheel and center section of a GT45 and install the GT42 backing plate,wheel, and cover on it. Then you take The GT42 turbine housing and turn it out to clear the GT45 turbine wheel. But you leave a little ledge in the housing so it passes a 3" plug test. My tractor buddies say they gain a 100hp over a GT42 with a hybrid like that. Only issue is price. While still cheaper then Precision it is not cheap becuase you must start with the Ball Bearing only CHRA.
S400s can be had a good deal cheaper. I would becareful with Bullseye. They tried to hose over a buddy of mine. He ordered a S475 with the 87turbine. It came in with the 83mm. When he called they said the would not take it back because he disassembled the turbo. After driving up there with he changed there minds. But it should have never come to that. They should have sold him what he wanted not what they thought he needed.
What do you mean? I'm not talking about a blocker flange, but an actual valve that closes off one side, then opens it for full flow at a given point. Shouldn't hurt drive pressure one bit.
how can that work on a divided pedistall like we run , it looks like it would close off all flow to the cylinders on that one side of the motor
Yeah... but if you're running a T6 flange GT55 I don't think drive pressure will be on your list of problems.
how can that work on a divided pedistall like we run , it looks like it would close off all flow to the cylinders on that one side of the motor
Undivide it? :rofl:
Spool up is far from an issue for me. When I leave the line at 4800rpm turbos seem easy to spool.
It would be interesting to test on an auto truck. But I can not see why it would not work. Here is link to a thread with spool up data using one of these. He seemed pleased.
http://www.ls1tech.com/forums/force...pool-valve-testing-pics-nerd-like-graphs.html