power gains with 3.5 down pipe

[chevyII]

at what power level does upgrading DP to 3.5 add gains??? I just bought a set of ATR headers and am thinking about building a custom 3.5 DP out of a TH style upper. Also wil the down pipe clear the headers with the custom TH upper for a hybrid.

[Russ Merritt]

Not with the heater box I don't think. I'm gonna do this in a couple weeks and I'm takin my heater box out. Been dieing to do it forever as it will clean up the engine bay big time. Not sure but untill you have a Q-trim wheel I don't think the 3 1/2 is needed. Could be wrong as people hav gone REAL fast with a 3".

[TURBO 6]

FWIW I dyno'd 604hp/643 torque at the wheels with a 3" thdp.

[Russ Merritt]

Now get a 3 1/2" and run 624. Sounds like a plan to me.

[chevyII]

I see both you guys are running 70mm turbos I think around 600-650hp would gain with a 3.5 to a muffler (1). This is going in a early nova and I plan on running a 45a or a GT in that size. Will a TH 3.5 clear ATR headers?

[TURBO 6]

Russ, I bet if I kept tuning I would've made over 624. The motor only had 7 miles on it when we started dynoing. I also had problems with the wastegate.

[Russ Merritt]

Absolutely! Few more miles on her and she'll make a bit more. THEN, the 3 1/2! 650????

[TURBO 6]

Yeah, that's the plan. Hopefully it'll run 9's.

[86brick]

Well according to Mr. Armstrong "there was a definite performance gain, perhaps as much as 20hp on Jane's car from moving up from a 3-inch to a 3.5-inch downpipe".... Keep in mind Jane's car has a TA66 Q-trim turbo (basically this is a stock appearing TE45A with a Q-trim wheel) and her car has run 10.20 @134mph.... Not bad for a car that weighs 3600+lbs!

[86brick]

Originally posted by ILBCNU6
A TE-45A isn't stock appearing as it has a one piece inlet bell-compressor housing, a TA-45a is stock appearing. The 45A is already a 66mm compressor wheel and the Q trim is just several more compressor fins added. This info came from Limit Eng. Janes' Engine is a S1 now with all the good internal parts as Reds' is a S2. I wonder why? The "Raptor MAF really helps makes these cars rock plus some good tuning! The first .6 sec, the power level is maxed out! Amazing isn't it! Smooth running cars that run low 10's easy in race trim or faster. I don't know how the 3.5" THDP fits under the heater box, ATR Headers might cause the DP to hit the heater box? Stock manifolds would be easier to fit though. Using the poly motor mounts raise the engine slightly too, so some fitting might be needed. Gene

When I spoke to John Craig he told me the TA66 and the 45A turbo were basically the same turbo (the inlet bell being the only main difference between the two because both have a 66mm comp wheel)...... Yes I know Jane's engine is a S1 with the good internals however it is still only a 231ci motor with iron heads (it has to be for it to be TSS legal).....

[gnxtc2]

If you have a Q trim wheel, the 3"THDP with block the opening.

You either will have to get a 3.5" or port/grind open the inside of 3" pipe to clear the opening.

By going to a bigger pipe coming out of the turbo, you will pick up HP

Just passing this along.

Billy T.
gnxtc2@aol.com

[Russ Merritt]

I hogged my ATR pipe out to the max. I bolted the exhaust housing to it by itself to see how much to go. Get out the carbide tip and tell your compressor to suck it up, it'll be a while.