Chris, their is no reason you can't get 88 power with 78 spool. Just need to properly size the turbos.

 

Do tell. This sounds juicy.

I do agree that the power fell off too soon with the 78. My 388 with the 76 peaked at 5800.

 

I would like to see this on a mustang dyno aswell. It would def change the spool of the bigger turbo.

 

wow great info here. i hope the St80 i traded my S85 for will be in the middle here!

 

i am to wondering why the gts fell off so hard?? what kind of cam are you running or close to if your secret on the specs? maybe adjusting the cam to the gts would be perfect?

btw, is there a big difference between an lt1 and ls1 when it comes to cams?

edit: thanks OP, prob the best apples to apples thread since ive been on here. can't wait to see the twins

 

Seems like an odd dyno my 76 gts seems to work better then that 78 you tested

 

You cant compare it to yours as you are on a completely different platform. These types of comparisons can only be made against themselves. The OP is running an SBC.

 

Cam was a 224/224 .575 .575 115lsa, the 78mm turbo was huffing pretty good, right around 23psi which is pretty hefty in the upper RPM range, I think the hot side was the restriction because with the same settings on the eboost 2, the pt88 made more boost from my command to hold pressure on the top side of the wastegate. the gts was likely seeing some pretty high turbine inlet pressures and pushing open the wastegate.

The new setup I'm putting together is completely different, it will be twin ball bearing 67mm turbos with a different cam and a single plane intake manifold. Several other changes have been made as well to strengthen the bottom end and improve the oiling system. The original motor was losing oil pressure in the upper RPM range and I have done everything in my power to figure it out. I believe tapping the turbo feed at the oil filter adapter housing was a poor choice but i got away with it on the 78gts because the center section was a bit more restricted than the pt88. as soon as i put the PT88 on the car my oil pressure instantly showed 20psi lower at idle sitting around 18psi hot. The bearings eventually went south and I pulled the motor to regroup. I had every intention of going to an LS based setup, but in the end to achieve my goals on the lowly LTx platform nagged at me enough to give it one more shot. Hopefully the new Callie Billet main caps will add some rigidity and instead of a splayed cap setup from an f-body block, I am switching back to my factory LT4 straight 4 bolt main block. A better oil pan, pump and pickup will be used in conjunction with the block having the oiling system gona through by a trusted machine shop to optimize the galleys and prepare it for high RPM and better oil flow where it is needed.

I want to lengthen the powerband 1000-1500 RPM and see if I can get the power to work for me a little longer in each gear. Its a pain in the *** to shift so frequently just when it starts feeling good!

Hopefully the new setup will be back in action toward the middle of July, I have everything here for it and the motor is all but assembled. I'm finally getting pretty excited about the car again and hopefully I can get the combo where it should be and hit my goals of 1200rwhp on a 355 LTx platform. then I will turn the boost down maybe put some smaller turbos on it and hit the road course some!

Chris

 

Mine is on a sbc too 364 ci.. Just saying a lot of guys make more then 811 with a pt76gts

 

Great stuff,thanks for putting in the wrench/money/time for a good review. Makes me feel alot better getting rid of my 74.5mm for a 88mm. great work.

 

Thanks for sharing the results and info..
Is the car Manual or auto I read 2step and 2nd or 4th gear I didnt what transmission??

I'm going to start by build in a month or two Built 347ci H/C and Single 80 or 82 Turbo this is on my ZO6 I really hope I can reach 730-760rwhp on pump gas+meth 15-16psi and close 900rwhp race gas 20-21psi

I hope can hit full spool in under 4500rpm with M6 trans...

 

what happened to that one the broke on your car im looking for one to mock up my hot pipes with

 

Whats the 88 good for? On say a max effort 364-370ci LS engine??

 

it was replaced by Precision.

it is rated at 1250hp.

Chris

 

I meant actual numbers on an LS based car...I know what they are "rated" for, im just wondering if anyone has hit the 1000whp mark...

 

do you still have it and his car is ltx based not ls