after market exhaust system??????

[louis d]

i talked to a guy at a fairly reliable exhaust shop. i've been planning to do a cat back exhaust to my 87 GN. only other mods the car has right now is a cold air intake. the guy at the muffler shop said the stock exhaust systems are really well designed with 98% flow, and changing the exhaust to IE flowmaster duals, or a 3" single shot etc, would only increase the sound and not the horse power/performance. i thought that was a strange reply, being he was taking money out of his own pocket telling me this. is this true? if not any exhaust system pointers( brands) or recommendation. ps..i need to replace the cat in any event...thanks in advance

[turbojd]

If you plan on doing any more mods to the car in future you will need to free up the exhaust, don't know what he's talking about, but if your replacing the cat conv. anyway I would put a cat back exhaust on it at the same time and save yourself the trouble down the road, car will breath much better especially if more mods are done to it as you go. I have the Hooker cat back 2 1/2" system on my car with aero chamber mufflers, nice sound and no drone, but there are other systems available too your choice.

[zeus87gn]

Don't use Flowmasters. They are good for N/A vehicles, but not for a turbo. They will restrict the flow more than what you have now. It is so by thier design. Check out their website and you will see what I am talking about.

[Keller]

I am not sure I would give the Flowmaster mufflers such a hard time. I know of a low-11 GN with them, and the owner gets them to work OK. But the idea of them doesn't make sense on a turbo car, I must agree.

Still, there are good exhausts out there. Don't get a 'muffler shop special' or the one piece Flowmaster system.

[86Nick]

The less restriction the better. Do away with the cat if using for race purposes (yea right). Get a muffler that has a straight through design. Stay away from the hooker areochambers they are heavy and resticting. The hooker kit that is sold is good for the main pipes that come off the cat but the mufflers suck and the tail pipes are cut to short and bent completely wrong. Don't forget that if you upgrade the muffs and piping that you should get a three inch down pipe. Being that this is the first stage of the exhaust system. The quicker you can get the exhaust gases out of the motor the better.

[Keller]

Don't forget that if you upgrade the muffs and piping that you should get a three inch down pipe.

:dunno: I managed to go high 11's though a stock sized downpipe, so I don't think a downpipe should be such a high priority. A lot of cash to focus in all one place.

[buddiiee]

as far as getting allll the restriction out of your exhaust as you can, its true but, not as necessary as people think. there are a lot of cars out there, more than you think, that their exhausts are outflowing their motors. its really easy to do. i have a decent amount of friends, that have made their cars heavier, their wallets lighter, and their cars gained ZERO hp/torque on the dyno. straight up. i know, because i have done it too. (like 3 days ago) As for your car, if you want a good performance setup, keep the stock buick headers on there now, (their design isnt too high-speed, but for some reason, they do work really well, unless youre pushing some good hp. anyone will tell you that) and then, just unbolt everything from the dp back, and throw a good 3" single shot on there, with no cat/resonator, and cap it off with a good straight thru muffler like a dynomax ultraflow. that will do it for you for a long time to come. theyre way lighter than duals, a tad cheaper, and easier to install. the only thing is, theyre a touch louder. but, loudness is directly related to flow. the louder it is, the better flowing it is. the quieter, the more restrictive. ive beat that question up a zillion times with the local muffler shop, and the tech guy at dynomax. though the guy at your muffler shop is very close in what he said. alot of cars, will NOT see ANY gains, with massive exhaust changes. simply cuz the engine just isnt flowing that much air anyways. on my bmw, my exhaust outflows my engine. its loud, free flowing, and does nothing. :dunno: (now i gotta return it close to stock, to quiet it down again) Plus the tech at dynomax just told me that some cars like a tad bit of backpressure at lower rpm's, cuz it helps em out with low end torque. i dont know why, but hes the tech at dynomax, not me. Though im not sure if thats true with turbo motors. Our motors push a lot. but yea, its not really necessary to go all out on your exhaust. All these people looking to custom bend a 3.5" dual exhaust with no mufflers are wasting their time. no stock 231 block will push that much air. plus, my friends n/a, built 360 cuda lost a tenth or two, by UNcapping his exhaust. go figure. every engine has her own personality. ya just got to experiment.
If anything else, in the future with some more mods, all you'd have to do is replace the downpipe. but then again, maybe not. but as for now, i think all you'd need, is to gut your cat, and throw a good straight thru muffler on there. youll be just fine. you can do that in a day with minimal money.