dj55b

iTrader: (2)

I've been kinda curious about this question and hopefully it doesn't sound dumb. I was just curious if you're building a supercharged engine would you want your headers and exhaust system to be built just like an NA application? If not what need to do be done?

The reason that I ask is that I currently have SDJ headers and was planning on further improving everything behind there by adding a reverse cone megaphone after the collector and if I do my testing NA to achieve the best HP NA would this help in my supercharger setup or just be a waste of time.

rotarygod

iTrader: (1)

It's not a stupid question. It's a very relevant one. Exhaust tuning is based on several factors such as air temperature and velocity. One of the important things to remember in exhaust design is that you are also trying to flow a certain amount of air at these temperatures and velocities. A supercharger crams more air into the engine and hence more air comes out. If you have the same size exhaust pipes as you did n/a, the only thing that can happen is that this air speeds up and travels faster through the exhaust system. This does in fact change tuning. Of course you are restricted by the size of your exhaust port so flowing tons more than it can is a futile exercise. Your header will work just fine but you'll find that it's max benefit rpm range will have shifted downward a bit. It's not to say your car will fall flat in the upper rpm ranges. It will have a little effect up there. Optimally you'd want to have a larger diameter exhaust pipe which would shift the rpm range back up. The downside of course is that the low end power goes down slightly but this is what the supercharger is for.

I see no reason why you can't still go forward with your megaphone plans using your existing header. Headers are another example of where multiple things come into play. The primary pipe length and diameter have a tuning effect. The throat area of the collector as well as the pipe convergence angles have an effect. The megaphone will also have a tuning effect. There are ways to design your exhaust around your supercharger without touching the stock primary pipes and what you want to do is the way to do it.

I personally wouldn't do any testing before your supercharger is installed. The results will not be the same after it is. It would be best to wait until it's on and tuned before you play around with the exhaust mods. You'll probably end up with a different setup altogether than you would if you had done it sooner.

There are many things that people need to realize when designing optimum intake and exhaust systems for different engine combos. On the intake side the intake manifold needs to be designed differently for n/a's, turbos, centrifugal superchargers, and positive displacement superchargers. I'm even talking about keeping porting the same. Each system has different requirements and one manifold is not optimum for the rest. Not even among the forced inducted engines. The same holds true for the exhaust. Obviously we are limited by turbos as the real work is in the manifold before the turbo. Supercharged engines have different exhaust requirements than n/a's. Even centrifugal supecharged engines have different needs than engines using positive displacement superchargers. There's quite a bit to it.

I know I didn't need to get long winded but just know that every system has it's own needs. Don't design on one type of system when you intend to use another. Hold off on the megaphone design until after the supercharger is installed.

dj55b

iTrader: (2)

Thanks RotaryGod,

None of your post are ever too long. I still have to design an intake manifold for the centrifugal supercharger that i'm going to be doing for it, and that means i have to re-read your thread about intake design.

As far the power being moved down with my current setup i think that would be a good thing as my max torque is sitting at 7000 rpm and would like it to drop to about 5500rpm. I'm more into that field anyways. thanks for the prompt reply though.

Sam