nyt

iTrader: (1)

.96 is undivided. 1.00 is divided. the gt4082 i had was great, but the inducer wasnt large enough to support the boost levels i was looking for. i find it funny my t61 spools faster/harder than the gt40 and has more top end. however, i have a much larger gt40 on my fd whith a .72 cover that runs much better than the 4082

DIRep972

NYT, Im a little confused in this thread w/ all the GT40 compressor wheel talk.

Now, your PT61 uses a GT40 56 trim compressor wheel, it is the same compressor wheel used in the GT35R. It has a 61mm inducer w/ 82mm exducer.

Your GT40 is using the small 50 trim GT40 compressor wheel. It has a 58mm inducer w/ 82mm exducer correct?

There is also a GT40 52 trim that has 64mm inducer w/ 88mm exducer.. This compressor flows 72lb/min.. I noticed someone mentioned the GT4088 earlier, but neither of your turbos use this compressor. So I am unsure why it was brought up.

Just to clarify, your 58mm GT40 compressor in the GT40 is running out of steem up top, while your 61mm GT40 compressor in the PT61 is holding up nicely. correct?

Are you using this set up for drag racing? road racing? or just street driving?

Looking forward to your reply, thanks.

Chris

nyt

iTrader: (1)

no, it uses the GT35R wheel. its different from the 56 trim gt40 which has a (66.5 if i recall correctly inducer?)
the gt35r/pt61 has an 82mm exducer, and a 61mm inducer.



street/drag racing.

the gt4082 aka 50 trim, has a 58.5 or 59 i dont remember inducer. it runs out of breath up top and stops flowing at or before 55lbs/min basically. the pt61 is fine on the top end, and has more room to go. this is from the larger inducer.

the gt4088 is the 54 trim just fyi.

I also have a gt40 56 trim on my fd. this turbo moves more air than all of the other ones ive talked about =]

rx7tt95

Meant to say .94. Definitely a fully divided hot side. I dunno, the power, even top end, seems to be there. Definitely less than my last turbo, a modified GReddy T78 but it's also been a much better street turbo. If your "spool" with the PT61 is better than the 4082, it might be something I want to try

adictd2b00st

who did u end up going thru to buy that turbo? i'm assuming that it doesn't die off up top like your other one did, maybe this is the one i'm lookin for then?

DIRep972

Thanks for the reply. The trims for all the different GT40's get confusing. Thanks for correcting me on the 4088. I am right about the 56 trim GT40 though. If you do the math (inducer X inducer) / (exducer X exducer) X 100 = trim, for the 61mm inducer w/ 82mm exducer you will find that it is a 56 trim. I've sold this compressor wheel more then any other to guys in the honda community. Lots of SC61's and GT35R's. I don't have much experience w/ the other GT40 wheels though. the GT4088 seems to be pretty hard to come by and the GT40 58mm inducer never seemed worth the time.

Anyways, how do you think a 35R would do in a road race situation? I basically just wanna have fun and do HDPE's, and have a fun street going car as well. I'd keep the boost low and just try to build towards reliability. But do you feel that the response is there for this to be a good road race turbo or a lil too large?

rx7tt95

Back from the dead thread...I've been doing a lot of experimenting and thinking about the 4082 not being able to support higher boost levels and I do not believe that to be true. Taking one look at the compressor map should tell you it can and will. BOTH GT40's are rated at same hp level whether it be the 4088 or the 4082 (750hp), more so than the PT61 at 680hp. NYT made more hp on the 4082 than the PT61 but qualified that it was due to wheel slip.

Everybody seems to be fixated on the right end of the compressor map when a turbo spends far less time there (once per rev range cycle) than when it's ripping through the midrange and a far broader area of the compressor map.

I've modified my 4082 discharge, removing the V-band flange on the end. Previously, I'd just tugged a silicone tube over it and clamped it as best I could. Really a poor substitute for doing it right and I'm 100% sure it leaks boost. Last weekend I removed the compressor cover and machined the v-band flange down and used a 2.75 to 2.5" silicone reducer. Snug as a bug in a rug. And guess what? Full boost all the way through the rev range at 1.25kg. NYT, how did you secure the connection from the compressor discharge to the IC piping? Also, the rear turbine housing requires extensive modifications to the V-band discharge with certain manifolds due to it's size/length. How about boost controller issues? I wasn't getting full boost with the AVC-R until I bumped the duty cycle up three percent. I will say I do not get full boost in first gear and probably not second. Tires spin up horribly at 1.25kg. I do seem to come on boost sooner however. I have an undivided GReddy stainless tubular manifold.

I've attached a "pre-Steve" dyno tuning session on a Clayton. My speed goes up to 155 which is due to a higher redline (8500). At 8k however, I'm hitting 145. For this tuning session I made about 10 runs and tuned from about 5800rpm on up. Later, when Steve tuned it, he increased my midrange by 40-60hp in most spots but I lost a bit on the top end (10.4 a/f on his tune to 10.8-11.0ish a/f on mine). His timing and split is much more conservative than my tune (and I'm sure his is better!).

I do believe there's a better turbo out there for the FD, especially one that's easier to mount on an engine, LOL. It may be the 4088, the 40R, a 35R compressor with a 4082 turbine, etc...I just don't see the 4082 being too small. It'll make 400hp fairly easy. Probably much more with the proper engine ports, manifold, etc...