3" exhaust is built...

[1991 e30 bmw 318is]

ha no turbo.... vortech some day i hope....

as for cost under $300 shipped for two mufflers and pipe wasn't bad its crazy over priced if you go to exhaust shop, just go to metal shop.... my plan was use a pipe bender but didn't want to work with ss... cut notches and bent then weld up cracks works good never bought any u bends for it.. should of put a flex pipe in it tho... i have a leak i can hear up front somewhere not sure if its just gaskets or a crack. i scraped real bad pulling into a parking lot the other day, so it could of cracked it... find out soon not a big problem I dont think.
the stanless doesnt have the give mild steel has its very hard. il get more pics when i jack it up to inspect leak...

[weaksauce]

Really, is this a serious question.

just wondering why the need for 3" exhaust. i see no point in it for a m50 unless it is a FI motor.

[1991 e30 bmw 318is]

lots of people running duals over 2.25" not much different....

[Turd]

Get the air out as FAST as possible. 3" is fine. Fuel injected engines of today will compensate and make up for any lost back-pressure. The need of such a thing as back-pressure is from the yesteryear days of carburetors requiring adequate pressure to alleviate the vacuum effect of sucking in fuel to prevent burning a valve.

Nice work :)

[FredK]

Yeah, it really doesn't matter that he chose 3.0" pipe. The effects are negligible in comparison to header choice, where primary and secondary pipe sizing and length are a lot more critical.

[ck_taft325is]

Yeah, it really doesn't matter that he chose 3.0" pipe. The effects are negligible in comparison to header choice, where primary and secondary pipe sizing and length are a lot more critical.

Fred, make me headers you sexy beast?

[FredK]

I can't imagine fabbing custom headers. It'd be a lot easier if the front swaybar wasn't in the way, and I had a better system of mitering pipes rather than marking them off, then praying my saw doesn't wander while making the cut, then having to grind them flat on a disc sander.

Probably easier to buy knockoff headers, chop them at the collector, weld a triangular bullet up there, then reweld.

[weaksauce]

i politely object to the statement that backpressure doesn't have any effect on these motors.

I pulled the center section off of my e39 540 to have some work done to it, and it wouldn't even light up the tires in 2nd gear with the mid pipe off.

back on with the pipe and it was tire fire time again.

Just speaking from experiance here, not internet myth/hear-say.

enjoy your 3" pipe.

[FredK]

If you take the midpipe off an M62, there's no scavenging effect because the merges are underneath the car.

[weaksauce]

If you take the midpipe off an M62, there's no scavenging effect because the merges are underneath the car.

i'm talking about the single pipe from the merge back to the muffler

Get the air out as FAST as possible. 3" is fine. Fuel injected engines of today will compensate and make up for any lost back-pressure. The need of such a thing as back-pressure is from the yesteryear days of carburetors requiring adequate pressure to alleviate the vacuum effect of sucking in fuel to prevent burning a valve.

Nice work :)

wrong.

Yeah, it really doesn't matter that he chose 3.0" pipe. The effects are negligible in comparison to header choice, where primary and secondary pipe sizing and length are a lot more critical.

what is you definition of a secondary pipe? Is it not where he merged the 2 into 1 to make his monster 3" pipe?

I applaud him for the effort, but 2 2" pipes would have flowed better and given more ground clearance (which it looks like is a concern)

anyhow, looks like he put a lot of effort into that setup, so I give him props for that.

To each his own. Its not my car, so who am I to say it's wrong. As long as he is happy with it.

[1991 e30 bmw 318is]

very happy with it... sounds way better then duals, its lighter, and smother power band no loss anywhere.... and ground clearance isn't any worse then my old duals.

[FredK]

what is you definition of a secondary pipe? Is it not where he merged the 2 into 1 to make his monster 3" pipe?

I'm referring to the exhaust headers, and yes, the secondary pipes are those that lead to the 3" merge.

I agree, to each his own.

If you wanted to nitpick, his 2 into 1 merge is likely where most of the power is lost on this system, not the choice to use 3 inch pipe. Fabricating with dual pipes is a lot more difficult than single pipe, would require twice as many bends, that though they are smaller and cheaper, would still end up costing around 50% more.

[M-technik-3]

Funny Fred, both you and I are looking at 3" exhausts in the same locations. Have you started yours?

OP sorry off topic.

[FredK]

This will probably make weaksauce go into shock, but I'm using 3.5" pipe. I fabbed the rear section. I have some pics in my thread in the Projects subforum.

[nando]

Fredk you suck. backpressure makes torque, dude. Not velocity or scavenging effects. and 2 pipes flow better than one, Duh. surface area doesn't matter.

;)

I think I would prefer bends over all those welds, but it's sufficiently sized it probably doesn't matter. For the welding challenged (like me) you can find boxes of mandrel bends on ebay (basically screw ups/scraps from pro shops) for around $50. I traded my leftovers for part of the labor of having mine built.

I need to crawl under there and get a pic of the bend around the subframe. it ends up being no lower really than my stock cat/supersprint was. with Vbands it takes seconds to unbolt the exhaust from the car, I love it. I really hated undoing the stock downpipes, even with an impact it took forever..