[slowSwede]

Hello,

I've read a couple of threads about this and can't really find an answer to the question, "At what levels in terms of power is the stock exhaust restrictive?"
In the ads for some exhaust the promise you X hp and torque gains, now I'm just wondering has anyone (no vendor) dynoed before and afterwards when you've only changed the exhaust but still have rougly the same setup, like cats? If so, were there any performance gains stock? Tuned?
Ilike being able to pass emissions testing.

What I'm interested in is learning about the limit of the stock exhaust in terms of when you really need it. Getting a tune in a month or so, and then I might get an exhaust as well.
+10 hp stock for 1000-1500 bucks is ok since this should leverage the whole plattform. But does it really?

[cn555ic]

Originally Posted by slowSwede

Hello,

I've read a couple of threads about this and can't really find an answer to the question, "At what levels in terms of power is the stock exhaust restrictive?"
In the ads for some exhaust the promise you X hp and torque gains, now I'm just wondering has anyone (no vendor) dynoed before and afterwards when you've only changed the exhaust but still have rougly the same setup, like cats? If so, were there any performance gains stock? Tuned?
Ilike being able to pass emissions testing.

What I'm interested in is learning about the limit of the stock exhaust in terms of when you really need it. Getting a tune in a month or so, and then I might get an exhaust as well.
+10 hp stock for 1000-1500 bucks is ok since this should leverage the whole plattform. But does it really?

if you want to extract more power from exhaust system, get downpipes rather than exhaust...DPs will yield you about 15-20hp

[Former_Boosted_IS]

Originally Posted by cn555ic

if you want to extract more power from exhaust system, get downpipes rather than exhaust...DPs will yield you about 15-20hp

The stock exhaust has pancake section that are guarantee to cause restrictions. At higher power levels that will matter.

cn555ic is right though, DPs are the logicall first step.

[D.B.S]

Originally Posted by cn555ic

if you want to extract more power from exhaust system, get downpipes rather than exhaust...DPs will yield you about 15-20hp

Catted Downpipes? He did state he likes being able to pass emissions. With Catless DP's he might not be able to pass emissions, unless he doesn't mind swapping the old DP's back in when it comes to the emissions test... Atleast with highflow Catted DP's he has a better chance of passing, then with non-catted DP's... But I don't even have DP's so, IDK.

[slowSwede]

So, aftermarket catted downpipes do give an increase in performance?
And they do pass emissions tests?
+10-15 hp for something that is basically good for the vehicle sounds perfect.
Are the above numbers backed up by dyno numbers in any way?

Since I'm going for a tune I'd like to remove the worst bottlenecks before doing so and in other turboed cars I've replaced the downpipe first.

I've read that some aftermarkets parts (this was actually for Subarus but I guess it could be translated to Bmw's) actually loose power since the original system was designed for stock performance and the Ecu didn't respond well to changes. As stated, this was for a Wrx or Sti upgrade where the vendor stated an increase of 10-12 hp while independent testing suggested a 7hp loss.

Any tips on downpipes that pass emissions and beyound a doubt increase power?

[D.B.S]

Originally Posted by slowSwede

Any tips on downpipes that pass emissions and beyound a doubt increase power?

What do they do over where your at to test emissions? Do they just hook up into the ODB port, or do they actually hook up a sniffer and all that to your exhaust? Or is it just a visual check to see if you have cats? It really depends on how strict your country is..?

[s.myrr]

I have a 2010 coming and am pondering this as well. I plan on getting a GIAC tune. I don't want DP's that i'm going to have to mess with o2 sensors or check engine lights, just more flow... hence maybe it's easier to get a cat-back instead? It seems there are not too many 2010s out there with DPs to really know yet...

[slowSwede]

In Sweden they do connect your car to a sniffer and rev it, once a year when they get older (4-5 year maybe).
Although, with some cars imported from the US they don't, or they do as well. They connect them, have them at idle and you pass if you emit less smog than hmmm I think it's like cars from 1975.
Lean maps and complete free flowing does pass, but only if you have a Us import.

For the 335 I have to pass the ordinary test, and they are sort of picky about this, which is a good thing in one aspect.

Cheers!

[Syndicategt]

CA is one of the most restrictive states in the US, and probably has some of the strictest standards in the world. You should be able to pass the emissions test with catless DP's and a catted exhaust or visa versa. If you are worried about it do what I do. Get high flow cats on your DP's (like the ones AR has) and run a catless aftermarket exhaust. When it comes time for the emissions test, simply just swap out your aftermarket exhaust for the stock one and you will most likely pass with the 4 cats in place.

[slowSwede]

That was a good idea!
I can live with the idea of changing the exhaust every once in a while.
Guessing the install is a bit messy on the downpipes, how long would it take to put new ones in for a home mechanic=me.
I've done it once on the Subaru and that was an entire day....and a lot of swearing.
I know it's almost impossible to say how long, but I'm at least a bit inclined towards working on my cars. Let's say, if it takes a shop 4 hours, then it will take me the double. An estimate anyone?

Cheers!

[cstavaru]

BMW advertises 5hp (crank) for the BMW Performance Exhaust. So the stock exhaust is restrictive even at stock power levels. But a compromise had to be made because of noise concerns.

So an aftermarket exhaust, even cat-back, will help.

[ar design]

Downpipes are where the power is at - however, as others have stated, the cat-back will definitively net some gains especially at higher HP levels, .

[Sherwin@ActiveAutowerke]

It takes our technicians around 3.5 hours to install downpipes with their experience and resources. You can safely say it will take you around 6hours, not including the time it takes to cool down your car of course.

An exhaust takes a technician around 1.5 hours, and should be pretty similar if you have access to a lift.

If you are going to be changing any parts for emissions the exhaust will be the mod that makes the most sense. The only way I believe you will loose power is if there is something wrong with the design of the exhaust. i.e., two little back end pressure, bends that create pockets of air, etc...

Please correct me if I am wrong.

[DJKhan85]

So is it certain that running high flow cats with no secondary cats WILL pass emissions? I live in MA and we have the same strict crap that Cali does.

[Syndicategt]

Originally Posted by DJKhan85

So is it certain that running high flow cats with no secondary cats WILL pass emissions? I live in MA and we have the same strict crap that Cali does.

I'll find out soon if that is the case! Running AR's catted DP's with AE catless exhaust, I'm a tad worried but that's why I have my stock exhaust if I need those extra cats.

Sherwin: You are correct, but with good made and fitting mods, DP's should take a novice under 3 hours and I did my exhaust in around 1 hour (granted I have access to a lift). My suggestion is to have catted DP's, which everyone will agree that these require the most time and trouble to install, and have a catless exhaust. The exhaust should be a quick swap out if you have to install more cats for the emissions check. I know this is the reverse of what people typicall do, catless DP's and catted exhaust, because that will yeild the most gains, but these people usually don't have to worry about emission laws as much.

[ar design]

Originally Posted by DJKhan85

So is it certain that running high flow cats with no secondary cats WILL pass emissions? I live in MA and we have the same strict crap that Cali does.

If you are worried about emissions, we now offer our downpipes with HJS motorsport catalysts - guaranteed NO CEL, even on 2010 models, and should have no issues with emissions. Usually takes me 2hrs on jackstands to install downpipes.

[s.myrr]

Can you PM me pricing/details for these?

Thanks!

Originally Posted by ar design

If you are worried about emissions, we now offer our downpipes with HJS motorsport catalysts - guaranteed NO CEL, even on 2010 models, and should have no issues with emissions. Usually takes me 2hrs on jackstands to install downpipes.

[ar design]

PM sent

[Syndicategt]

Originally Posted by ar design

If you are worried about emissions, we now offer our downpipes with HJS motorsport catalysts - guaranteed NO CEL, even on 2010 models, and should have no issues with emissions. Usually takes me 2hrs on jackstands to install downpipes.

I run AR's catted DP's. I never had any issues with CEL's or codes thrown. These pipes fit perfectly, run great, and look outstading! All I can say is, you get what you pay for, and why chance it with your $50,000 investment (a few exta $$$'s are a drop in the bucket in the long run).

[ar design]

Originally Posted by Syndicategt

I run AR's catted DP's. I never had any issues with CEL's. These pipes fit perfectly, run great, and look outstading! All I can say is, you get what you pay for.

Some people just don't get that

[Praemienhai]

Originally Posted by Syndicategt

I run AR's catted DP's. I never had any issues with CEL's or codes thrown. These pipes fit perfectly, run great, and look outstading! All I can say is, you get what you pay for, and why chance it with your $50,000 investment (a few exta $$$'s are a drop in the bucket in the long run).

I got CEL after the update to v 36.x with the AR catted DPs.

Deleting with the BT tool didn't work in the long run, after rd about 50km I got a new CEL... With the older software versions I didn't had such problems.

[ar design]

Originally Posted by Praemienhai

I got CEL after the update to v 36.x with the AR catted DPs.

Deleting with the BT tool didn't work in the long run, after rd about 50km I got a new CEL... With the older software versions I didn't had such problems.

Yeah, the newer BMW software has been made a LOT more sensitve. We now offer the HJS equipped DPs for the 2010s, and older cars with updated software - HJS guarantees no CELs, and they are MOT approved etc.