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Discussion Starter #1
So, I'm running 18psi daily now and the car don't feel fast no more. I think the turbo is quite worn now (if any of you guys have been following my posts, the turbo was dying since I let a garage to play with it and decided that a U shaped oil drain was a good idea).

So, should I rebuild this GT28RS and keep everything the same? I have a GT2871R that belongs to a friend of mine, the turbo's at my place, and he needs some cash (I might throw him some coins for it).

The problem is that my ECU is tuned to my setup now, and I understand that if you change VE on a MAP based configuration things are gonna get messed up, I'm not sure if the larger compressor side of the GT2871R is gonna affect things enough to make things go sour.

Oh, can someone hit me up with the link to the shimless bucket conversion? My engine's really really tired now, when I start the car up the engine sounds like it's gonna crap a brick out, the valvetrain wear might have contribute to this lack of power.
 

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Akane,

Sorry to hear about your engine/turbo troubles. You're still stock VE and I haven't seen any evidence that the GT2871R would be considered an upgrade. If torque is what makes the car "feel" fast, then the GT2871R will make it feel slower, and I don't know how much boost you'd have to stuff through it to make it produce more top end power than you have now. Here is a dyno of a GT2871R at 21 psi that was professionally tuned with an EMS http://www.mr2oc.com/showthread.php?t=102685&highlight=GT28RS...see post #17. Since you've already got a GT2871R hanging about it might be the least expensive route to go...but drifting the back out won't get any easier ;)

Bruce
 

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Call me crazy, but I think there are enough posts about this that you really don't need to make a thread.

We all know it will end up with Bruce saying it's the greatest turbo ever and anything else is just a bad choice. Don't try to argue with him either. ;)
 

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Discussion Starter #4
99 GS-T, it is a very good turbo, it's just that I want to try something new and see if there are any other options out there, since rebuilt GT turbos are not the best thing out there compared to a new GT turbo. And my main concern is the MAP based ECU with the different turbo, and I don't see anyone out there who has dyno both turbos on the same MR2.

Thanks Bruce, I will look more into this matter, I want more tire spinning action but don't want to lose driveability, I know I have to give up either one, just trying to find a midpoint here. Thanks.
 

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Akane said:
The problem is that my ECU is tuned to my setup now, and I understand that if you change VE on a MAP based configuration things are gonna get messed up, I'm not sure if the larger compressor side of the GT2871R is gonna affect things enough to make things go sour.

Oh, can someone hit me up with the link to the shimless bucket conversion? My engine's really really tired now, when I start the car up the engine sounds like it's gonna crap a brick out, the valvetrain wear might have contribute to this lack of power.
Hopefully someone will be able to answer your questions with respect.

Also, in case you aren't aware, you can buy a new factory replacement CHRA if you don't want to rebuild the old one. If the wheels aren't damaged then it should be as new. You said from the beginning that you thought this previously used turbo was in poor shape, and when you dyno'd it that it had a major manifold leak, yet it still yielded great results. I know when my turbo adapter nuts loosened and let exhaust leak it had a pronounced affect on power. And if your engine is now in poor shape also, that makes 3 reasons why you would see improvements just by repairing the problems. And hopefully that wouldn't require a re-tune.

Bruce
 

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Akane said:
The problem is that my ECU is tuned to my setup now, and I understand that if you change VE on a MAP based configuration things are gonna get messed up, I'm not sure if the larger compressor side of the GT2871R is gonna affect things enough to make things go sour.
I just read the original post in RickyB's thread pertaining to this topic at http://www.mr2oc.com/showthread.php?t=152529. He claims that changes ahead of the intake manifold have a minimal impact on VE (like intake, IC and compressor wheel upgrades), as opposed to things like head, exhaust, and "turbo changes". By that I'm assuming he is referring more to a turbine change that affects back pressure. Since the GT2871R uses the same turbine as your GT28RS, then back pressure would be about the same. Turbine efficiency also affects VE, and this is where the larger compressor wheel comes in as it affects that aspect. Since the peak turbine efficiency is lower on the GT2871R, then the VE will be actually lower, and this would have the affect of richening the AFRs if anything...and your tune would still be safe. This is my interpretation only, and I'd definitely recommend confirming that with someone more "tuned in" to the whole EMS/tuning scene.

Bruce
 

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Discussion Starter #7
Thanks Bruce, that was informative, I will have to talk to my tuner about this first, before I make any turbo changing decision, if he says I need a retune then there is almost no point of me changing to a bigger turbo, unless I have plans to run higher power otherwise.
 
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