Exhaust upgrade for 535i euro verion?

[sneekens]

since my stock pipes are dual 1.75", i'm thinking of having it crossflowed into a single 2.5" pipe.. then a 22" long resonator with a 4" housing, inlet/outlet 2.5", then to a muffler with a single 2.5" inlet but with dual 2" outlet.. The 2.5" tubing gave a little volume more than those duals plus it will weigh lighter too..:D I want the cats removed but I'm afraid OBC might give me those "check catalyst" read outs. I read only american version can't be removed.. suggestions anyone? mods are just basic, not those drastic turbos.. please post your exhaust mods too if ever..


thanks!!!

[Itsnotme1988]

I don't understand why you would want to go from duals to single if you're not running a turbo. Makes no sense to me... Running a single 2.5" is going to be less restrictive, but you will actually build more backpressure (bad) because you are lower you exhaust velocity and it has to work harder to evacuate itself.

[BillionPa]

E34s are OBD1, and you can remove the catalyst without an error message. OBD2 cars have O2 sensors after the catalyst to detect its operating efficiency, and that is what throws those messages.

i believe crossflowing pipes into a big one is only relevant with inline-4 engines, as the exhaust pulsing creates massive suction on the other cylinders exhaust valves, which results in much greater power. on an I6 i am not so sure.

exhausts on bmws are designed thanks to some tough fluid dynamics calculations, and are not restrictive at all, unless you are using a race spec engine or forced induction.

the best think you can do is have the inside of your exhaust manifold Sterling coated, and the outside thermal barrier coated. then get a performance muffler (a real one not an ebay one)

[sneekens]

thanks guys! lots of help... btw, after having computed the pipe volume, single 2.5" will roughly give a 10 cu.inch more (both @90 inches in length) than the dual 1.75's... which i was thinking will give me a smoother acceleration all the way and giving me an ample amount of top end power too. i feel that at top end rpm's loose a small amount of power with stock, IMO.. and after researching on some sites, the m20 525i engines have the same exhaust pipes too.. dual 1.75's.. so i'm guessing, m30's can still accomodate more exhaust space.. HMMMMM..... so I'll retain my dual 1.75"?? but any suggestions on resonator and muffler dimensions? i want a mild purr while in idle but a muscular roar when I floor it..;) hehe.. everything will be freeflow.. and lastly my pipes do have those O2 sensors.. so is it OBD2?


thanks again!

[Paul in NZ]

there isnt much restriction,you would prolly gain as much by trying to lose some weight.No you are OBD1....

[AngryPopTart]

As was stated, the exhaust is not restrictive and consists of at least one x-pipe in the system. It's already well designed. General consensus is there is no such thing as a performance muffler for these cars, only louder ones. Alot of people seem to agree that the only exhaust related performance gain on these motors is headers... aside from forced induction. When I was replacing my muffler cause it was totally rusted out, I drove around with just the down-pipes; the cat, resonator and muffler were removed. It sure sounded neat when you opened it up, but it didn't feel any faster... I'm sure it brought me one step closer to being deaf though. Anyway, proves that the exhaust is already nice, IMO.

If you want to make more noise, you can get cheap Thrush glasspacks with 1-3/4" inlet/outlet sizes. You could have an exhaust guy set two right next to eachother where the factory muffler went and then figure out a good way to do exhaust tips out the back. I wouldn't remove or change the factory resonator.

[ILoveMPower]

As far as I'm concerned, intake and exhaust on an E34 is for sound only. No power is gained, as the stock systems are tuned to perfection.

As said above, I think only headers will give you noticeable gains (unless you go forced induction).

If you're willing to wait a few weeks for me to get my muffler on, you'll know what a magnaflow sounds like on a 535

[sneekens]

Wow!!! thanks for the feedbacks guys! ok-ok, i'll leave them stock, but gota have those mufflers too, magnaflow! heard some in youtube and they growl with a subtle idle... thanks again! really appreciate it.