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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Feedback re: Downpipes please



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      11-27-2007, 09:45 PM   #1
boosted305
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Feedback re: Downpipes please

Was at Advance Autowerks the other day making some preliminary inquiries.
Was interested in getting some DP's (having been a long time previous turbo owner and a DP was KEY)
I Asked about Downpipes and got a surprising response...

one of the guys there didn't recommend them, said they don't make any power because the turbos are so small and need SOME backpressure....

this is counterintuitive to all that I know about turbos....every turbo I've ever had: the faster you can get the exhaust out the better...of course I've never had 2 turbos sooooo small...never had less than a T04

asked around at a couple of other tuner shops in the area and did get one other similar response...(they might have just heard this from AA also though)

I tried a search and didn't find any posts mentioning anything like this

can I get some feedback from you guys on this?

thanks in advance
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      11-27-2007, 09:47 PM   #2
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didn't riss racing downpipes net a nice 50 wheel torque gain?
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      11-27-2007, 09:49 PM   #3
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HFC DP by UR will help with the backpressure. To hell with that advice, the gains are proven on the dyno!
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      11-27-2007, 09:49 PM   #4
boosted305
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like I mentioned, every post I've seen has said how great they are and I was really interested...that's why I was so surprised with their response...
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      11-27-2007, 09:56 PM   #5
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I went in there a few weeks after I got my car and asked some questions. I was startled by their ridiculous hourly charge and the full hour of installation it takes for XEDE. My first time for a similar install was one hour. Now I bet I can do it in thirty minutes, let alone a tech can do it in 20 I bet.

Then I was told the same thing about DP and the backpressure thing. I have no idea who I talked to, but you have got to be kidding me. You don't know anything if you can't read the delta on a dyno. 20-30 whp cannot be an artificial number, even with hood up and fans on full blast. Not happening.

Forget the advice, search the oodles of information on here, and make the decision. They are beneficial and the HFC version will give you the least headaches because you can plug your O2 sensors right in the available bungs...no SES light, no limp modes, no rasp, no rice, nothing. HFC DP FTW....and DP in general...FTW.
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      11-27-2007, 10:17 PM   #6
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Quote:
Originally Posted by E90 335i View Post
I went in there a few weeks after I got my car and asked some questions. I was startled by their ridiculous hourly charge and the full hour of installation it takes for XEDE. My first time for a similar install was one hour. Now I bet I can do it in thirty minutes, let alone a tech can do it in 20 I bet.

Then I was told the same thing about DP and the backpressure thing. I have no idea who I talked to, but you have got to be kidding me. You don't know anything if you can't read the delta on a dyno. 20-30 whp cannot be an artificial number, even with hood up and fans on full blast. Not happening.

Forget the advice, search the oodles of information on here, and make the decision. They are beneficial and the HFC version will give you the least headaches because you can plug your O2 sensors right in the available bungs...no SES light, no limp modes, no rasp, no rice, nothing. HFC DP FTW....and DP in general...FTW.
The man's got it right, Dyno's don't lie. Whoever you talked to clearly needs to get himself on e90post before making random recomendations
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      11-27-2007, 10:24 PM   #7
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I dont care what size turbo,s you running.The least amount of back pressure on a turbo car the better the performance.On a street driven NA performance car you need some back pressure.
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      11-27-2007, 11:19 PM   #8
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i have also heard of that, i actually started a thread on it and got somewhat of a mixed response.

BTW, did you mean Active Autowerks?
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      11-27-2007, 11:30 PM   #9
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Love my UR Downpipes.. and yes they certainly did make a difference. Go for it .. you"ll love them...
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      11-27-2007, 11:41 PM   #10
boosted305
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Quote:
Originally Posted by 335iheLLraiseR View Post
i have also heard of that, i actually started a thread on it and got somewhat of a mixed response.

BTW, did you mean Active Autowerks?

whoops, yeah Active is what I meant!

thanks for the responses guys....
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      11-28-2007, 01:08 AM   #11
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Quote:
Originally Posted by boosted305 View Post
Was at Advance Autowerks the other day making some preliminary inquiries.
Was interested in getting some DP's (having been a long time previous turbo owner and a DP was KEY)
I Asked about Downpipes and got a surprising response...

one of the guys there didn't recommend them, said they don't make any power because the turbos are so small and need SOME backpressure....

this is counterintuitive to all that I know about turbos....every turbo I've ever had: the faster you can get the exhaust out the better...of course I've never had 2 turbos sooooo small...never had less than a T04

asked around at a couple of other tuner shops in the area and did get one other similar response...(they might have just heard this from AA also though)

I tried a search and didn't find any posts mentioning anything like this

can I get some feedback from you guys on this?

thanks in advance
Less back pressure the better on turbo cars. Dp's make power.
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      11-28-2007, 04:20 AM   #12
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Active can be a little snobbish at times, they do like money and charge a lot , when i had my M3, there , i spent over 2000 on just flashing my ecu a few times and then had to pay $100 when i needed a 5 min update after the dealer reset my ecu, not to mention the silly $200 just to turn off my upgraded thermostat light.. like many companies, they only like to sell and talk about there products (which makes sense), but on the downside, if they dont have a downpipe out, then they probably wont suggest it till they do...

Dont get me wrong they do a great job and have excellent products but ive learned to be careful about what they charge and tell me.
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      11-28-2007, 10:03 AM   #13
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FI applications utilize smaller valve-event overlaps, which benefit from no back pressure. A quick diesel upgrade is simply changing to really large exhaust to dro as much back pressure as possible. For hot cams with high-lift and large overlaps, back pressure helps at low RPMs to keep the car from turning off, since the intake air will vent to the exhaust port to quickly for low cylinder speeds. If you have variable valve overlap, you can program the ECU to keep the overlap duration relatively small for low RPMs and increase with RPMs. This will keep the engine happy and produce a lot of power. In this case, you could easily reduce back pressure.

In the end, a properly tuned car will benefit from the least amount of back pressure. Notice any dragsters running exhaust restrictors to increase back pressure?
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