[nitjt]

I am considering doing my first mod, and maybe only mod. I don't know the difference in all the exhaust options DP, Catless, cat back? I want to add some hp and more agressive sound to E90 335 xdrive. Thanks in advance

[Transport3r]

If your only mod is going to be an exhaust, definitely keep all the cats.
I'd check the various catback options out for sound.
Popular ones are the BMW Performance exhaust, Eisenmann, Vanguard, Borla.
Depends on your price range and sound taste.

[idrift4wd]

OK, downpipes are the main exhaust component that can truly add a good amount of HP. Getting catless downpipes or high flow cat downpipes will give you better a nice bump in HP. Not much since its running a stock tune, but your car will run better.

for exhausts, there are two types. Catback and axlebacks. axlebacks are just mufflers, catbacks are a full exhaust from downpipe to mufflers(includes mufflers) cat backs are much more money and you may gain a few hp. If your looking for just a change in exhaust tone, get an axleback.

[JStang]

Worse bang for buck mod available on this car. At least get a tune then an exhaust.

[Transport3r]

Originally Posted by idrift4wd

OK, downpipes are the main exhaust component that can truly add a good amount of HP. Getting catless downpipes or high flow cat downpipes will give you better a nice bump in HP. Not much since its running a stock tune, but your car will run better.

You'd have to at least run a DP fix to not get engine codes, if not a full tune.

[nitjt]

What kind of perfromance gain could I expect with DP, vs cat back? I don't want to think of myself as a tuner, but I do want more sound from exhaust when I step on the gas. Looking to keep it at or arounk 2k but don't want to fuss with engine codes and emission problems.

[idrift4wd]

Originally Posted by Transport3r

You'd have to at least run a DP fix to not get engine codes, if not a full tune.

very true, i forgot to include that.

Originally Posted by nitjt

What kind of perfromance gain could I expect with DP, vs cat back? I don't want to think of myself as a tuner, but I do want more sound from exhaust when I step on the gas. Looking to keep it at or arounk 2k but don't want to fuss with engine codes and emission problems.

in terms of HP gain, downpipes will get you more horspower. how much HP? idk, if you dont tune your car then maybe 5-10 hp. removing cats will help in horsepower. I would not recommend this for you as it will throw a check engine light.

a full exhaust will probably gain 5hp to the wheels. This may be a problem because some exhaust will drone.

98% of the tuned 335 users on here arent tuners either, its hard to not tune the car when tunes are relatively cheap for the HP you can get. tunes range from 400-1000 bucks, but bump HP up 40-80 HP. Just think about it because you can always un-install the tune.

[JStang]

Originally Posted by nitjt

What kind of perfromance gain could I expect with DP, vs cat back? I don't want to think of myself as a tuner, but I do want more sound from exhaust when I step on the gas. Looking to keep it at or arounk 2k but don't want to fuss with engine codes and emission problems.

Your butt dyno isn't going to notice gains from either without a tune. Tune + DP's and you are going to notice a big difference versus just tune and cat back. Some of the fastest cars on this site have run the stock exhaust system.

Based on your criteria, I would get a tune and pick up a cat back or axle back in good, used condition. The good thing about the axle back is the secondary cats are still in place so emission testing will not be an issue. Very noticeable bump in power and you will get the sound increase you are looking for.

[WesleyC]

Originally Posted by JStang

Worse bang for buck mod available on this car.

Spend your money more wisely if you want to make some more power.

First, a tune is the best mod you can do. There are 3 main options to choose from - JB4, Proceed and Cobb. They all have there advantages and disadvantages, you decide which one is best for you.

Second, some catless downpipes should be your next purchase. Not only will the add noticeable power, but they will make your exhaust louder and more aggressive.

Finally, an intake is a great, cheap mod that will add as much power as an exhaust on it's own.

A tune, catless downpipes and an intake will give you ~110hp to the wheels, all for the same price (more or less) as a catback exhaust, which will give you only a fraction of that power.

[nitjt]

Can you do after market DP on stock exhaust? Do DP eliminate the cats? How are after market DP different from stock?

[Transport3r]

Originally Posted by nitjt

Can you do after market DP on stock exhaust?

Yes

Originally Posted by nitjt

Do DP eliminate the cats?

Yes, the primary ones

Originally Posted by nitjt

How are after market DP different from stock?

They have a bigger diameter and don't have restrictive cats in them, thus offering better flow.

[nitjt]

Sounds like DP and a Cobb tune will run about what a cat back exhaust will set me back (and give me a healthy boost to the hp) If I do the DP with stock exhaust what does that do to emission regulations and being able to pass....will DP alone provide the aggressive sound I am looking for? What is the downside to running DP and tune when it comes to maintance and reliability? Do Dinan or BMW performance offer DP?

[Transport3r]

The DP will make it sound more aggressive. I think catless DP + Stock catback offers one of the best noise combinations for this platform.
To pass emissions you will need to fool the computer into thinking the rear O2 sensors are reading realistic values while still allowing the obd reader they use to talk to the computer. Don't know if cobb does that. The piggies don't, that's why they need DP fixes to pass inspection. If you have to pass a sniff test in your state it means you can't get catless DPs.

[nitjt]

COBB tune is about 5 miles from me here in TX, what do you guys think about COBB and what are some good choices when it comes to DP.

[WesleyC]

Don't cheap out on downpipes. The expensive ones are expensive for a reason. You are paying for fit and finish. AR is the most popular and generally considered the best, but I have MS downpipes, which are slightly cheaper, but just as nice. I have no complaints.

[nitjt]

I found a set of used Ulitmate Racing catted DP, any feelings on these?

[nitjt]

I am considering pulling the trigger on a used ultimate racing catted DP, they are not cheap but I have not heard anything about them, has anyone? Just to be sure will this with my stock exhaust will give me a more aggressive sound? How much power gain if any would I see with DP only? I will add a Cobb at at a later time what will the gain be Cobb+DP vs Cobb only?

[nitjt]

Help

[WesleyC]

Originally Posted by nitjt

Help

I don't know much about UR, but this thread scares me:

http://www.e90post.com/forums/showthread.php?t=302931

Downpipes without a tune will yield little to no gain. With a tune, you will notice a big difference.

A tune should be your first mod. Bolt ons (downpipes, intercooler, etc... ) don't provide any real gains without a tune.

[nitjt]

Thanks thats interesting something to consider, I may have to bite the bulit and get AR.

[iDriveABeamer]

Originally Posted by nitjt

Thanks thats interesting something to consider, I may have to bite the bulit and get AR.

Trust me, AR is the way to go. It will run you around a G after shipping and all. If you buy off mod barg a ins, they have an O2 simulator you can add for $70 that will bypass the check engine light. Im getting mine for the new season. Cheers.