Will a 3 1/2" DP help with my setup?

[YellaGN]

Curious to see if going to a 3 1/2" DP from my 3" would be beneficial or a waste of $ and time. If beneficial...how much so? See sig for mods.

 

[GNVYUS 1]

I could of sworn someone posted an increase of 20 at the wheels with the 3.5" over the 3" DP.

With your mods, I would bet on it making a difference in MPH after the 1/8th, especially with that turbo and it's exhaust wheel.

 

[c&cgn]

With all of your mods, I can't see why it wouldn't at least help somewhat. Do you have any current ET's and MPH ?

 

[TurboDave]

Curious to see if going to a 3 1/2" DP from my 3" would be beneficial or a waste of $ and time. If beneficial...how much so? See sig for mods.

Anything you can do to free up post turbo backpressure is a plus++.
I am curious though, with your setup, why such a tight converter???

 

[top gun]

Anything you can do to free up post turbo backpressure is a plus++.
I am curious though, with your setup, why such a tight converter???

3200 stall is tight???

 

[SPOT MY 6]

3200 stall is tight???

I was going to say the same thing. Mines 2900!

 

[Brer Rabbit]

3 1/2 inch downpipe.

U have more cam, turbo, and heads then me, and I asked all my buddys before I bought my 3 1/2 TH pipe and the consensus was "get it". Im still tuning the new motor but so far the only issue I have with the pipe is that the pipe vibrates on the floor board just before the bend that turns the pipe straight under the car. I may have to take it back off :frown: and use the persuader on the floor board. So I guess size does matter. :biggrin:

 

[TurboDave]

3200 stall is tight???

Well, I'm a "footbrake" racer, so yes, it seems tight IMHO. He's got a ton more turbo and motor than I do. The multi disc vigillante I have is around 3200-3400 and I don't think I'd like it any tighter.

 

[YellaGN]

I dont have any current times. Ran 11.00's @ 122 with stock heads and cam last year. This is a brand new setup. As far as the convertor goes....i love a tight convertor. IMO theres nothing worse than a big soggy stall. I just figured if the DP was worth it, now would be the time to slap it on! I just want all the power i can get out of this 109. Thanks for the opinions....keep'em coming.

 

[TurboDave]

Maybe it's a matter of symantics. When I refer to tight, I mean a "Low" stall rpm. I prefer it a little looser (higher stall rpm) to get the spool up quicker, and launch harder at a higher rpm.
I'm not making enough horse power that I can afford to come off the line at a low soggy rpm.

 

[turbojimmy]

Well, I'm a "footbrake" racer, so yes, it seems tight IMHO. He's got a ton more turbo and motor than I do. The multi disc vigillante I have is around 3200-3400 and I don't think I'd like it any tighter.

I just got my multi-disk Vigilante installed and I agree. I asked for a 3500 RPM tall but it feels a lot tighter than my 3600 9x11 (may it rest in pieces). After getting used to the loose 9x11 I don't think I'd want it any tighter. The Vigilante still spools the turbo nicely despite it's tight feel. But as you point out, he has way more motor and turbo than your or I.

Back on the topic:
At what point should someone start considering a 3.5" DP? Wouldn't you need 3.5" exhaust in order for it to make sense? Or would you just run out the dump?

I saw the dyno-test claims of 20+ HP but I wonder what other mods would you need to get that sort of gain.

Jim

 

[Scott Atk]

FWIW, I still use a 3". That's not saying that we both wouldn't benefit from a 3 1/2" Just gives you an idea of the 3" downpipes potential. My best time below was also through a single 3" exhaust.

 

[bison]

I have a similar build up except iron heads and welded ported and pinned stock manifolds. I have a 3" and a 3.5" dp. I will do some runs with both and report the difference when i do it. Trying to keep the boost the same in between runs or dyno passes could be a little difficult if i were to swap dp's on the dyno. You should definitely gain with the 3.5" in your application.

 

[turbojimmy]

FWIW, I still use a 3". That's not saying that we both wouldn't benefit from a 3 1/2" Just gives you an idea of the 3" downpipes potential. My best time below was also through a single 3" exhaust.

That's plenty fast for me. Looks like I don't need to spend the $500.

Thanks!

Jim