jordan0806

Hope this helps everyone

DavidPHumes

iTrader: (1)

I'm hoping to make 600RWHP through a Powerglide on my TC76 .96 AR stock shortblock 5.3L with LS6 cam running E85 (running an 8.8" solid axle from an early 90's Mustang). Anyone think it's possible? I'm thinking I'll need 14# of boost. I'm going to be running on spring pressure but I have a 48mm Turbosmart Pro Gate so it should hold just fine. Race weight will only be 2,900LBs.

jordan0806

Yeah, with a good enough tune, 600rw can be attained with that..may nee more than 14 pounds but the fun thing is you can play with it....

Vetal

iTrader: (3)

jordan0806, are these turbos at your hands? I'd like to know exact radius of cold part of TC78 vs PT7675
Also I wonder, why charge air out port has such ridiculously thick wall on TC78???

91blowthru

thanks for the comparison pic, its very helpful with three very popular t4 turbos.

MillsMotorvation

+1 Thanks a lot

S13LSx

Will you update in this thread or start a new one? Thanks

willizm

iTrader: (10)

Well I think my TC78 is hitting backpressure on my forged stock cubed ls1. I've got 317 heads and am running a TU1 cam (225/225 581/581 113LSA) with about a 9.5:1 CR. You can see my graph below. As I push for more boost it tapers at a higher rate. Not such a big deal for the first two pulls as those are my primary 93 octane boost levels, but at the higher 15.7psi race gas setting my boost tapers down toward redline at a faster rate. My feeling is that I'm choking on backpressure due to the small turbine impeller.

How well do you guys think I'd fair doing a PT7675 .96AR swap as it's pretty much a direct bolt on replacement of the TC78? Plus I'm going all out with the ball bearings option.

stock48

iTrader: (17)

The PT will pick you up BIG time.

Nitroused383

iTrader: (10)

Sorry I don't have a more direct comparison.

TC76 @ 7lbs with 18-19 degrees of timing
PT76 @ 11.5lbs with 13-15 degrees of timing

willizm

iTrader: (10)

Thanks and I figure the pt is the next logical choice. Just curious if my findings mirrored anyone elses setup an if they have had a similar issue.

Vetal

iTrader: (3)

willizm, I think you'd have the same issue if your intake (most probably intercooler) or exhaust was a problem. 600whp seems too low for TC78 to choke. At least measure the pressure drop across IC, was fighting similar problems and in the end discovered pressure drop over my IC is about 7psi. It was cheap 3.5" unit though.

willizm

iTrader: (10)

I can check the Pressure drop, but this is a cx racing ic that most people use. Also according to Larry@ams the mustang dyno my car was on reads anywhere from 10-17% lower than their dynojet. I may be off a little onthe percentages, but he said it's a pretty significant difference so when looking at the numbers, I wouldn't be too caught up with it. Plus even at lower boost levels there is a bit of taper. Boost is referenced from the brake booster.

Vetal

iTrader: (3)

It's such a simple test I'd do it

Vetal

iTrader: (3)

So what's the most power / trap speeds with TC78? First time on track I trapped only 124mph. Probably would do a little better with more tuning
Most I have seen in this thread is 670whp and ~134mph?

NemeSS

iTrader: (127)

Tally TransAm

iTrader: (17)

ive already gone 133.8 with a tc76 and im willing to bet i go 140+ without a concern

stock48

iTrader: (17)

130 mph here with both Tc76/68/.96, and T78/68/1.15. This is at 4900 lbs in a 4x4 truck chassis. Truck dynoed 714 hp when it trapped 122mph with Tc76/68/.68 peaking at 4500 RPM before ported heads and meth inj.

Ryans99ls1

iTrader: (16)

No track times but numbers in sig. cam-only ls1, 12lb initial spike, settles to 9lbs 18-19 degrees timing.

overhere

iTrader: (2)

i went 142 with a TC78