ALFAGTV6.COM

Hello,

We are about ready to start working again on my Alfa GTV6 3.0 24V conversion. We hope to have the engine installed next week and I already have custom headers for my new engine. I was just wondering what suggestions or set ups that others have done that work. The exhaust system is custom and will be built from scratch so I just want to make sure that I instruct them correctly since I am not sure what design would provide me with the best performance.

Thanks

I like the idea of side outs with glass pack resonator(s)!

Make sure the exhaust from both cylinder banks is interconnected at some point. This allows for more effective scavenging of the cylinders. Magnaflow makes what they call a "power y" for this purpose. A good "X" pipe will do the same thing if you plan to go with dual exhaust. I suspect you are planning a single exhaust unless you are going with side outs or cutting out the spare tire well.

If you are going with forced induction throw everything I just said out the window.

really, you dont need an x, or y after the turbo downpipe, is that because the turbo effectively equalizes the backpressure between banks, or is that only applicable for single turbo in which the exhaust forms a y as it feeds into the turbo?

Well, actually I was thinking supercharger. On a supercharged motor the intake pressure is greater than the exhaust pressure during the overlap period which enables it to blow out the exhaust. There is no need to worry about collectors, equal length pipes, exhaust cross overs, X, or Y pipes or anything like that because there is nothing left to scavenge. A supercharged car simply needs the least restrictive setup possible without concern for these more complex issues.

This is why you don't see connected exhaust pipes on a Top Fuel dragster. They just want the least restriction possible and that's all that matters to them.

You will have to ask the resident turbo gurus about what's needed on a turbo car.

yeah i knew that about superchargers, i'll have to find out the lowdown on turbos.

Greg Gordon wrote:Well, actually I was thinking supercharger. On a supercharged motor the intake pressure is greater than the exhaust pressure during the overlap period which enables it to blow out the exhaust. There is no need to worry about collectors, equal length pipes, exhaust cross overs, X, or Y pipes or anything like that because there is nothing left to scavenge. A supercharged car simply needs the least restrictive setup possible without concern for these more complex issues.

This is why you don't see connected exhaust pipes on a Top Fuel dragster. They just want the least restriction possible and that's all that matters to them.

You will have to ask the resident turbo gurus about what's needed on a turbo car.

The reasons you don't have collectors and such on a top fuel is that they basically only run a very narrow rev band and the stacks are tuned to that rpm, they are the ultimate exhaust for that application.
Surely you wouldn't throw away the possibility to raise the VE on a supercharged engine just because you have loads of "free" pressure to clean out the cylinders?

You won't raise the volumetric efficiency on a supercharged motor (under any amount of significant boost) with collectors. Allow me to quote David Vizard on why dragsters don't need interconnected exhaust pipes. "The single pipe design is effective on fuelies because the supercharger thoroughly scavenges the cylinder relegating the header tubes to mere aiming devices."

That statement that they are mere aiming devices pretty much says it all. Pat Ganahl in his book street supercharging says pretty much the same thing. He says "In the case of a supercharged engine typical header tuning theroy does not apply. The length, diameter, and collector style of the headers is of little consequence."

Don't even make me start posting links to NASA on this one.

Thanks for the education on this. Remeber though, my alfa in not a turbo or supercharged. Just a standard 3.0l 24V that I hope has 270 hp at the crank. I was aware of the cross over and I want to have rear dual exhaust for the look.

I do not want to have a loud car or draw attention to the Alfa. Just a sleeper but with good performance.

Sorry we got sidetracked.

I would set it up with a Magnaflow "X" pipe and true dual exhaust. Of course you will have to cut out the spare tire well to do this. That way you can have one pipe down each side.

Exactly what I am doing - spare wheel well removed and flat boot floor to fit a full twin system.
You need to put the x pipe in the right spot though and I haven't even calculated primary lengths yet.

We have finished the exhaust system on the Alfa. If you are interested you can see pictures of the system under introductions. I have a question. Has anyone used Eastwood Stainless Color high temp paint to detail their exhaust system and to provide it with a rust proof coating? We are thinking of doing this and contemplation if it is worth the extra labor and material to do this.

Thanks for suggestions.

Make your system out of stainless...slightly heavier, but lasts long time