Innovate/Spritex/Bullet... What I found searching the web.

[JoeBoxer]

I'm inclined to agree the 2.5" is plenty but there will always be some that want the largest possible and until we test both its hard to say which one will produce the best numbers. 3" may offer more peak numbers but 2.5" might offer more "under the curve."

We'll see soon enough!

[Calum]

Perrin and Nameless have both confessed to trying 3 inch exhausts. Both also said that with a well made header, the 3 inch out performed the 2.5 inch, everywhere. The hold back is that the gains aren't huge and the volume is horrendous or something to the effect.

[Jeff86]

Originally Posted by Calum

Perrin and Nameless have both confessed to trying 3 inch exhausts. Both also said that with a well made header, the 3 inch out performed the 2.5 inch, everywhere. The hold back is that the gains aren't huge and the volume is horrendous or something to the effect.

Well if there's real data, that's good to know. It does surprise me a bit that 3" exhaust piping has no negative effect on low/mid range. That says a lot about header design.

[robispec]

We restricted the cat back area and picked up hp...we went back to stock for rear weight and undercar clearance issues and were suprized at the whp gain...

[Calum]

Originally Posted by robispec

We restricted the cat back area and picked up hp...we went back to stock for rear weight and undercar clearance issues and were suprized at the whp gain...

What system were you running, which header? With the stock header, or even something like the agency power, I have zero doubt that they are restrictive enough that the stock system is close to optimal. But, as I paraphrased, a well designed header can take advantage of a larger diameter system.

[JoeBoxer]

Originally Posted by Calum

What system were you running, which header? With the stock header, or even something like the agency power, I have zero doubt that they are restrictive enough that the stock system is close to optimal. But, as I paraphrased, a well designed header can take advantage of a larger diameter system.

I think a well designed header is a better investment than any cat back on the market, for noise issues i would do the header/over/front pipe and leave the catback alone whether with this supercharger or NA. sorry to go off topic...

[tom@kartboy]

Sounds like @Jason@Nameless needs one of these kits.

[Draco-REX]

Originally Posted by tom@kartboy

Sounds like @Jason@Nameless needs one of these kits.

And delay the relase of his headers too?

I foresee an infinite cycle of R&D between the Nameless Headers and Innovate SC resulting in the Ultimate Unicorn; capable of 300+rwhp on pump gas and a sound like Angels screaming, with an indefinite release date that is never reached.

[Jeff86]

Originally Posted by Calum

What system were you running, which header? With the stock header, or even something like the agency power, I have zero doubt that they are restrictive enough that the stock system is close to optimal. But, as I paraphrased, a well designed header can take advantage of a larger diameter system.

There's one other dynamic to consider since this car is not NA. He may have slightly increased the amount of boost with the less free flowing exhaust and the car liked it. There's no wastegate controlling that here.

[sw20kosh]

A turbo responds to big exhausts better because of the pressure differential across the turbine (ie you want as much exhaust pipe volume post-turbine so those exhaust gases pass over the blade faster and more efficiently).

That being said, people tend to forget that with superchargers: typically the more free flowing the motor becomes the less boost the supercharger will create at a given fixed pulley size. (A turbo compensates for a better VE because it is controlled by a set boost level not a set pulley diameter. This always creates more power)

For supercharger applications to truly realize the potential of an increased exhaust flow mod you would need to size the pulley to gain back that boost pressure.

However, even with the boost drop due to increased VE, making the engine more free flowing produces power. You may see the same whp after the exhaust mod but once you correct the boost drop, your whp will obviously go up.

[Draco-REX]

Originally Posted by sw20kosh

A turbo responds to big exhausts better because of the pressure differential across the turbine (ie you want as much exhaust pipe volume post-turbine so those exhaust gases pass over the blade faster and more efficiently).

That being said, people tend to forget that with superchargers: the more free flowing the motor becomes the less boost the supercharger will create at a given fixed pulley size. (A turbo compensates for a better VE because it is controlled by a set boost level not a set pulley diameter. This always creates more power)

For supercharger applications to truly realize the potential of an increased exhaust flow mod you would need to size the pulley to gain back that boost pressure.

However, even with the boost drop due to increased VE, making the engine more free flowing produces power. You may see the same whp after the exhaust mod but once you correct the boost drop, your whp will obviously go up.

Doesn't that only count for cars with an overlap cam? And does the FA20 have overlap?

[sw20kosh]

Originally Posted by Draco-REX

Doesn't that only count for cars with an overlap cam? And does the FA20 have overlap?

Think of it this way. For simplicity sake. It is all about flow. The way the supercharger works is it flows more air than the engine can ingest. This creates pressure, boost. If the engine all of a sudden can ingest more air, the pressure between the supercharger and the engine decreases.

A) Engine is flowing (consuming + expelling) X air, Supercharger is delivering Z air.

>install free flowing exhaust mod<

B) Engine is flowing X+Y air, Supercharger is still delivering Z air.

The net effect is that the engine is consuming more of what the supercharger can create which is essentially fixed (the supercharger's efficiency is unchanged, it is driven by its own innate efficiency + RPM).

Now what you can do is size the pulley so that the Supercharger delivers Z+Y air. Your boost is restored and you are making more power.

[Draco-REX]

Originally Posted by sw20kosh

Think of it this way. For simplicity sake. It is all about flow. The way the supercharger works is it flows more air than the engine can ingest. This creates pressure, boost. If the engine all of a sudden can ingest more air, the pressure between the supercharger and the engine decreases.

A) Engine is flowing (consuming + expelling) X air, Supercharger is delivering Z air.

>install free flowing exhaust mod<

B) Engine is flowing X+Y air, Supercharger is still delivering Z air.

The net effect is that the engine is consuming more of what the supercharger can create which is essentially fixed (the supercharger's efficiency is unchanged, it is driven by its own innate efficiency + RPM).

Now what you can do is size the pulley so that the Supercharger delivers Z+Y air. Your boost is restored and you are making more power.

I guess. Essentially you're creating more boost in the cylinders due to their less-than-perfect elimination of exhaust gasses. Otherwise, displacement is displacement.

[robispec]

Nice discussion but we made the extra whp on our last na dyno run lol
because that was the highest combo of all the na parts tested. Borla elh, over and mid pipe with the factory intermediate. pipe and muffler. Thats what we tuned the supercharger for