Whipple plus long tubes = ?

[The_Mad_Patcher]

Has anyone put their car on a dyno with a S/C and stock manifolds and cats and then added catted long tubes and retested on a dyno to show improvement? I just want to see the gain vs. the expense. Thank to all who may have experience.

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[sdiver68]

= loud car

 

[db252]

Yes and the gains aren’t that big of a difference. Certainly not in a cost to hp gain ratio. Definitely healthier for exhaust discharge though.

 

[BadGTR]

Not sure how the gains could not be a big difference. On my car putting long tubes on was worth 40hp before I did the blower.

 

[S550AC11]

I'm not sure about gains with a whipple but NA I'm at 427 SAE on 91 with ARH 1 3/4 headers and 3" exhaust with an AED Tune. Stock is around 370ish? It's definitely louder, I have Corsa Sport (quiet cruise, scream WOT). It has much improved throttle response and makes a lot more mid range torque (410 at 4200). I'm going boost soon, so we'll see how it turns out.

 

[moffetts]

How much of the gains from going LTH are from removing the cats?

 

[The_Mad_Patcher]

Thanks for the input so far. I would still love to see the before and after dyno sheets.

 

[engineermike]

Funny thing about screw and roots blowers is that the air flow through the engine is set by the supercharger inlet air conditions, blower speed, and blower geometry. Adding headers has its advantages (less pumping losses, lower cylinder temps and more ignition timing), but the airflow will be baskcally unchanged.

I wouldn’t be surprised if an na motor gained more than a supercharged motor when adding headers.

 

[DTeal23]

Not sure how the gains could not be a big difference. On my car putting long tubes on was worth 40hp before I did the blower.

40 with a tune? Or just straight up 40?

 

[AZ18yote]

I'm not sure about gains with a whipple but NA I'm at 427 SAE on 91 with ARH 1 3/4 headers and 3" exhaust with an AED Tune. Stock is around 370ish? It's definitely louder, I have Corsa Sport (quiet cruise, scream WOT). It has much improved throttle response and makes a lot more mid range torque (410 at 4200). I'm going boost soon, so we'll see how it turns out.

NA for now (FI later this year hopefully) catted ARH 1 7/8 into Corsa Xtreme on AED ff tune most recent pull was 471. The LTH alone are good for 30-40. Though as was stated much louder so much in fact I ended up adding a pair of Vibrant 1794s to calm it down some.

 

[AZ18yote]

How much of the gains from going LTH are from removing the cats?

From what I have seen only a couple of hp difference between catted and off road LTH.

 

[Tommy V]

If u dont consider 30 to 40 whp nice gains then get headers.Anytime u force more air into a motor u need to improve exhaust to help get that air out.Especially on a fi.car.Just measure the factory bottle neck and tell me what u think then.3in midpipes going into a 2in bottleneck right past the collector is not a good idea.

 

[sdiver68]

Thanks for the input so far. I would still love to see the before and after dyno sheets.

I know my 1st answer seemed flippant but this discussion has occurred many times here and to my knowledge the vendors and tuners all say not much difference.

Cats vs No Cats discussions are mostly about melting stock cats and causing damage. Then, no cat smell and loudness.

 

[Tommy V]

Please show me on hear where any vendor says adding lth and removing cats does not make much difference in hp on a fi car.I gained 16 whp by just putting cat deletes on my 15 pp na car.I guess it depends on what u call [not much hp].I dont know any vendors claiming that on a fi car.

 

[Burkey]

Funny thing about screw and roots blowers is that the air flow through the engine is set by the supercharger inlet air conditions, blower speed, and blower geometry. Adding headers has its advantages (less pumping losses, lower cylinder temps and more ignition timing), but the airflow will be baskcally unchanged.

I wouldn’t be surprised if an na motor gained more than a supercharged motor when adding headers.

I’ll agree with that completely.
Changes in cam timing and less reliance on scavenging are also part of it.
There’s a mob here in Oz claiming that adding their full exhaust (1 7/8” LT with high flow cats and 3” twin system) to a Whipple equipped vehicle will only add 20 Hp at the crank.
These people are in the business of trying to sell exhaust systems. If the gains were larger, they’d be claiming more. Make no mistake.

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