Industryha 0 Report post Posted July 24, 2004 Ive got a 1986 325i 5spd Hopefully u guys will have a good idea on the best setup for an exhaust. Nothing too wanky (bigass stainless mufflers) or loud but gives a nice deep sound with good flow. Does anyone know of any places that make aftermarket exhaust systems for the E30? Ive thought of having 2.25" or 2.5" straight thru to the back of the diff, then splitting it to come out on both left and right sides of the car, with a subtle chrome tip on both sides. Just an idea, open to suggestions.... Quote Share this post Link to post Share on other sites
bmwsparkle 3 Report post Posted July 24, 2004 more restriction if you do the "Y" bend, just have it single all the way thru, 2.25"s enough, get mendrel bends if ur keen enough, but not really needed unless ur turboin. Cobys are the sh*t, do Cobys. Quote Share this post Link to post Share on other sites
Guest WAGON Report post Posted July 25, 2004 hmmm for an e30 is single or twin best? Quote Share this post Link to post Share on other sites
Gus 5 Report post Posted July 25, 2004 on a 325 with a stock exhaust i seriously wouldnt bother doing anything if your looking for NA performance.....the only reason ill change mine is for turbo...stock sounds good and its not too loud...you wont gain anything performance wise from changing exhaust....but if you really really want to... a single 2.25-2.5" pipe would be the way to go...but why swap dual 2" pipes (stock) for a single 2.5"? IMO of course Quote Share this post Link to post Share on other sites
bmwsparkle 3 Report post Posted July 25, 2004 does the E30 325 hav twin 2" gus? my 5 had twin 1 3/4" the reason i had my exhaust done was because my middle muffler was rooted, so i ended up changin all my mufflers to cobys. Ive actually noticed quite an increase in performance, but that cud be because of my middle muffler had dropped the baffle and was restrictive. I dono, im only a amatuer. Quote Share this post Link to post Share on other sites
bumpstop325 0 Report post Posted July 25, 2004 (edited) hartage's 323 race car has twin straight through. with NO mufflers, with a 9hp gain, but not sure what the tourque figs were. now, i have got this from dyno run sheets. i have just chopped out my center mufflers and replaced them with two cobys. Edited July 26, 2004 by bumpstop325 Quote Share this post Link to post Share on other sites
Industryha 0 Report post Posted July 25, 2004 (edited) a single 2.25-2.5" pipe would be the way to go...but why swap dual 2" pipes (stock) for a single 2.5"? IMO of course I can see where your comin from. It doesnt look as if its is dual 2" piping, more like 1 3/4" or something. Im new to BMW so im probably wrong ! As long as I can find a reasonable price on someone to tig weld I will be using stainless steel piping all the way thru, maybe with a coby in the middle and replace the muffler at the far back with an identical looking in size and shape but stainless muffler I have. I guess the question now really is which size piping I should use and dual or not?? At the least all i want to achieve is increased flow and a nice sound. Edited July 25, 2004 by Industryha Quote Share this post Link to post Share on other sites
Gus 5 Report post Posted July 25, 2004 yeah my mistake, it is closer to 1 3/4, havnt actually measured, just guessing....i would go single, no advantage in going dual, 1 bigger single pipe will have much less surface area for the exhaust gases than 2 smaller pipes (a good thing for the single) tim did you notice any difference? Quote Share this post Link to post Share on other sites
bumpstop325 0 Report post Posted July 25, 2004 more noise, much better throttle response Quote Share this post Link to post Share on other sites
Guest Andrew Report post Posted July 25, 2004 I image Hartges car has all its gains from the tuned headers - a single pipe flows better than duel - I run 2.25 inch pipe with 2 resonators and a muffler - not loud at all. I noticed the gains cause I was running the small 323 exhaust on the new motor. Quote Share this post Link to post Share on other sites
MattA 165 Report post Posted July 25, 2004 I am running a single 2 1/2" with 2 small turbo resonaters, sounds great not too loud, it's the only exaust that I've had on it so have nothing to compare it to but I'm happy. Quote Share this post Link to post Share on other sites
Hartage 0 Report post Posted July 26, 2004 The 323i system was two pipes at 42mm id from the front to rear of the car. when i changed the front manifold to headers, the car felt better but as i had not dydo checked it i cant tell what the diff was. Dyno check after cutting the rear expansion box off and a small play with the air flow gave a 9 hp increase and a torque gain. Air flow on two pipes at 42 id is about 1/3 higer in capacity (as i work it out anyway ) than 1 pipe at about 56 mm id. Now need to make the pipes at the rear larger so they dont look so silly. Backl to 56 mm id i think,. What do you all make of that??????? Im still working it out. Quote Share this post Link to post Share on other sites
