[Evo8MRto335I]

I flipped the coin on this one.., I was going to do a 3" custom cat back today but things did not go as planned.

There is no possible way you could even try to attach/bolt/weld or whatever you want to call a 3" piping into the exiting flange of the stock downpipes.

The 3" piping will physically out surface the whole stock downpipe flange leaving absolutely no room.

I am not a pioneer on this car, there are many many vendors/tuners that already released their cat backs, after seeing about 25 different cat backs in the market I now realized that a 3" cat back is virtually impossible unless you put a bigger downpipe with a bigger flange.

You could only install a custom 3" catback if you bypass/delete the donpipe flanges and instead weld the pipings.

Unlike cars like the Evo, you can perfectly fine bolt on a 3" cat back to the existing downpipe(2 1/4") that is because the flange is huge and it will accept a bigger pipe without altering the flange, on the BMW you can't, flange is too small.

I might do the 2.5" custom catback or simply buy a catback already made.

my .2c guys:sad0147:

[oddjob2021]

Originally Posted by Evo8MRto335I

I flipped the coin on this one.., I was going to do a 3" custom cat back today but things did not go as planned.

There is no possible way you could even try to attach/bolt/weld or whatever you want to call a 3" piping into the exiting flange of the stock downpipes.

The 3" piping will physically out surface the whole stock downpipe flange leaving absolutely no room.

I am not a pioneer on this car, there are many many vendors/tuners that already released their cat backs, after seeing about 25 different cat backs in the market I now realized that a 3" cat back is virtually impossible unless you put a bigger downpipe with a bigger flange.

You could only install a custom 3" catback if you bypass/delete the donpipe flanges and instead weld the pipings.

Unlike cars like the Evo, you can perfectly fine bolt on a 3" cat back to the existing downpipe(2 1/4") that is because the flange is huge and it will accept a bigger pipe without altering the flange, on the BMW you can't, flange is too small.

I might do the 2.5" custom catback or simply buy a catback already made.

my .2c guys:sad0147:

or you could do what riss racing did with their 3" DP (to fit the stock exhaust) and just taper the end down to fit a stock DP

[radgator1]

Bolt on a larger flange then attach the 3 inch to that?

Not sure, but it seems like it could be done by the right machine shop

[Serjames]

My understanding is that the gas flow characteristics of this engine, even WITH an uprated intake, Turbos, or Downpipes are such that a 3" exhaust is overkill.

many of the Evo's that people use to compare with this engine are single Exhaust pipe engines...

We run 2, point being 2 x 2.5 inches is better than 1 x 3 inches.

Or so my miswah says...

SJ

[Evo8MRto335I]

^^^I agree with you on that.

[Evo8MRto335I]

Originally Posted by oddjob2021

or you could do what riss racing did with their 3" DP (to fit the stock exhaust) and just taper the end down to fit a stock DP

I think I am going to wait for the release of the biggest downpipes available then improve from there.

[silvrevo]

Is there any such thing as a dump pipe after the downpipes?

That would be a simple powerful mod.

[Evo8MRto335I]

Originally Posted by radgator1

Bolt on a larger flange then attach the 3 inch to that?

Not sure, but it seems like it could be done by the right machine shop

The point was to utilize the stock flange. The problem is that the stock flange is ridiculously small, you have to either shop it off and weld or put bigger flanges with a bigger downpipe.

I hope someone can adress this but I thin Riss Racing is in the right direction, they maximized the piping using the oem flange.

[Vegas_Sirk]

Originally Posted by Evo8MRto335I

I think I am going to wait for the release of the biggest downpipes available then improve from there.

^ yea you could always by 3" Down pipes ... cut the flanges off and weld on a 3" flange and go from there ... its def more work but in the long run you would get your 3" pipes to work. I was always taught that tapering is a no no and there is no point to go big back down to small ...

[Evo8MRto335I]

Originally Posted by silvrevo

Is there any such thing as a dump pipe after the downpipes?

That would be a simple powerful mod.

I swear and I double swear I thought about doing just that. Getting a QTP type electric dump valve and just use it on existing full exhaust, at the end you will only use it for racing purposes and 99% of the time will be stock and normal.

[Evo8MRto335I]

Originally Posted by M3This

^ yea you could always by 3" Down pipes ... cut the flanges off and weld on a 3" flange and go from there ... its def more work but in the long run you would get your 3" pipes to work

That is an alternative but honestly I think the stock turbos are so limited in flow that the 2.5" piping would do a great job. Just give me 2.5" pipes with better flow, lesser bends and no crushed points and I think tese turbos will still pick up as much HP/and tq as if they were 3".

On the same token, it is still a challenge to prove that a full 3" TB will make more power than a 2.5" TB on the stock 335i turbos and you ex turbo guys know what I am talking about

[LACA335i]

Originally Posted by Evo8MRto335I

I flipped the coin on this one.., I was going to do a 3" custom cat back today but things did not go as planned.

There is no possible way you could even try to attach/bolt/weld or whatever you want to call a 3" piping into the exiting flange of the stock downpipes.

The 3" piping will physically out surface the whole stock downpipe flange leaving absolutely no room.

I am not a pioneer on this car, there are many many vendors/tuners that already released their cat backs, after seeing about 25 different cat backs in the market I now realized that a 3" cat back is virtually impossible unless you put a bigger downpipe with a bigger flange.

You could only install a custom 3" catback if you bypass/delete the donpipe flanges and instead weld the pipings.

Unlike cars like the Evo, you can perfectly fine bolt on a 3" cat back to the existing downpipe(2 1/4") that is because the flange is huge and it will accept a bigger pipe without altering the flange, on the BMW you can't, flange is too small.

I might do the 2.5" custom catback or simply buy a catback already made.

my .2c guys:sad0147:

I had a dual 3 inches cat back custom made for me at my local muffer shop. 1st it will fit, however you have to cut it after the flange and than weld it on it. 2nd you will fell that the car is losing power. 3rd. It will robbed your Mpg down to 17 mpg, while driving conversatively. 4th.. you will hear rassingly sound because it will kinda touching the almium shield .. Anything can be possible.. Dude i did alot trial and error on my car with difference stuffs.. i cant and would not give anymore future project on my car. YOu best bet on this car would be 2.5 inches.

[Vegas_Sirk]

Originally Posted by Evo8MRto335I

That is an alternative but honestly I think the stock turbos are so limited in flow that the 2.5" piping would do a great job. Just give me 2.5" pipes with better flow, lesser bends and no crushed points and I think tese turbos will still pick up as much HP/and tq as if they were 3".

On the same token, it is still a challenge to prove that a full 3" TB will make more power than a 2.5" TB on the stock 335i turbos and you ex turbo guys know what I am talking about

Yea I agree 100% that a dual 3" will be over kill ....

However I swear that even the 2.5" systems I have seen posted are still tapering at the flanges ...

[Evo8MRto335I]

urrgggghhh!! just for a second I was thinking about a QTP dump valve but then I realize that the BMW has twin downpipes so that means having to buy two separate and independent QTP dump electric pipes which will make the cost significant..

[down4it]

I've had like 4 or 5 different exhaust sytems on my car and the best is the dual 2.5" with no cats, with an X-pipe... Just seems to work best on this car... Dual 3" is way overkill and will not give any advantages... Maybe with a GT35R turbo running 30+ lbs of boost it will help but by then the motor wont hold up so while you're dumping another $30k into the car get some 3" piping made for it

[Evo8MRto335I]

Originally Posted by LACA335i

I had a dual 3 inches cat back custom made for me at my local muffer shop. 1st it will fit, however you have to cut it after the flange and than weld it on it. 2nd you will fell that the car is losing power. 3rd. It will robbed your Mpg down to 17 mpg, while driving conversatively. 4th.. you will hear rassingly sound because it will kinda touching the almium shield .. Anything can be possible.. Dude i did alot trial and error on my car with difference stuffs.. i cant and would not give anymore future project on my car. YOu best bet on this car would be 2.5 inches.

I definately concur on that one. Mostlikely I will leave it 2.5" . The reason why I was so excited is because not long ago I did a full 3" bolt on turbo back on my 94 Stealth R/T TT. The 3" TB was from Dynamic Racing and the car picked up a lot of HP and tq but here is the main difference, the flanges were huge. My issue today was the stock flanges, they simply have to go.

My approach today was not to cut the exiting piping, I want it to be able to bolt on the stock catback to the stock downpipe flange for future dealer trips. Do you see where I am coming from? Yes, I saw your review back then(very good write up)

[Evo8MRto335I]

Originally Posted by down4it

I've had like 4 or 5 different exhaust sytems on my car and the best is the dual 2.5" with no cats, with an X-pipe... Just seems to work best on this car... Dual 3" is way overkill and will not give any advantages... Maybe with a GT35R turbo running 30+ lbs of boost it will help but by then the motor wont hold up so while you're dumping another $30k into the car get some 3" piping made for it

I totally agree with you also. So far I am in the same page with all you turbo car owners. I tried something different today, I tried a configuration of being able to bolt on the oem catback in case of a dealer trip and definately did not work for me. Lessons learn and definately I will stick with a 2.5" cat back system.

Thank you guys for all the great feedback. Summary, 2.5" catbacks is the way to go on stock turbos.

[LACA335i]

Originally Posted by down4it

I've had like 4 or 5 different exhaust sytems on my car and the best is the dual 2.5" with no cats, with an X-pipe... Just seems to work best on this car... Dual 3" is way overkill and will not give any advantages... Maybe with a GT35R turbo running 30+ lbs of boost it will help but by then the motor wont hold up so while you're dumping another $30k into the car get some 3" piping made for it

you just spend maybe another 10K on it.. 30k is over kill.. where the heck did u get that number... GT35r is about 1500 K... labor about 1000 bucks, FMIC about 2000 cost and labor.. Riss racing buy it now about 1000.. cost ya 1500 cost and labor. Set of exhaust about 2000 cost plus 150 labor.

lets add up..

1500
1000
2000
1500
2000
____

8000 ( not include new trany ,set of stage 2 clutch, lsd )

Note if you can install it yourself, it will cost ya est 4500

[LACA335i]

Originally Posted by Evo8MRto335I

I definately concur on that one. Mostlikely I will leave it 2.5" . The reason why I was so excited is because not long ago I did a full 3" bolt on turbo back on my 94 Stealth R/T TT. The 3" TB was from Dynamic Racing and the car picked up a lot of HP and tq but here is the main difference, the flanges were huge. My issue today was the stock flanges, they simply have to go.

My approach today was not to cut the exiting piping, I want it to be able to bolt on the stock catback to the stock downpipe flange for future dealer trips. Do you see where I am coming from?

YEs. you see i have done it on my car *335i* in the past. During that time mid feb or march of these year, 1 or 2 company that make the exhaust system. it was like 1500- 2500 a system. I have no choice either i pay that amount go i can go do my own custom exhaust system myself with muffer shop help on welding. at that time, not too many shopping willy to do it for me.. TOo much liability on their insurance. .. you just having educational guess on the dual 3 pipping.

[down4it]

Originally Posted by LACA335i

you just spend maybe another 10K on it.. 30k is over kill.. where the heck did u get that number... GT35r is about 1500 K... labor about 1000 bucks, FMIC about 2000 cost and labor.. Riss racing buy it now about 1000.. cost ya 1500 cost and labor. Set of exhaust about 2000 cost plus 150 labor.

lets add up..

1500
1000
2000
1500
2000
____

8000 ( not include new trany ,set of stage 2 clutch, lsd )

Note if you can install it yourself, it will cost ya est 4500

Im not trying to diss your knowledge of cars or anything but when i say $30k i was talking about running this car at 30+ lbs of boost on a GT35R... To do that you would have to do everything that you listed above and drop the motor, change out all the internals for forged and (pistons, rings, crankshaft, valves, springs, retainers, camshafts) have someone custom tune the car from scratch to run on that setup, and obvioulsy a new fuel system, clutch, flywheel, and probably a tranny... You would probably end up spending more than $30k to get this car to 800whp...

[Noize]

Loud dump tubes on a nice, refined car like this would be beyond retarded.

[LACA335i]

Originally Posted by down4it

Im not trying to diss your knowledge of cars or anything but when i say $30k i was talking about running this car at 30+ lbs of boost on a GT35R... To do that you would have to do everything that you listed above and drop the motor, change out all the internals for forged and (pistons, rings, crankshaft, valves, springs, retainers, camshafts) have someone custom tune the car from scratch to run on that setup, and obvioulsy a new fuel system, clutch, flywheel, and probably a tranny... You would probably end up spending more than $30k to get this car to 800whp...

ok
why dont u use gt2860rs (dual) ( about 720 flywheel) about 675 whp change the trany add lsd. n bigger intercooler. get custom made driveline.. n reflash the ecu.. . dude u will get more than 800 whp.. BTW. 335i, i dont believe it got valve spring. It go flowing valve. little back pressure will need to push the valve up n down.. if u want to do ur way.. there are few thing internal conbustion u can change on the 335i.. U can upgrade piston to forged , u can have better ring. u can have upgrade crankshaft.. i dont think u want to mess around the camshaft. the camshaft will relate to the valve.. Remember that bmw already pretty much max tuned this car on mechanical size. I think they are using Forged Piston.. i could be wrong on that one.