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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 > No gains from Downpipes when running meth?



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      07-06-2012, 07:58 PM   #1
SuperBmw
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No gains from Downpipes when running meth?

So my friend has a FMIC and meth and he runs about 17.5 psi on his setup.

He said he recently added on downpipes and his quarter mile times didn't change and his 60-130mph didn't really change either. He said he feels no difference and said that the quicker turbo spool is something that he's not sure of either.

The only difference he said he noticed is a lower WGDC when pushing the car at WOT.

So if you're running 17.5psi on meth, when you add downpipes and still run 17.5psi are you technically making no extra power and the only benefit really is just less stress on your turbos?
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      07-06-2012, 09:16 PM   #2
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Quote:
Originally Posted by SuperBmw View Post
So my friend has a FMIC and meth and he runs about 17.5 psi on his setup.

He said he recently added on downpipes and his quarter mile times didn't change and his 60-130mph didn't really change either. He said he feels no difference and said that the quicker turbo spool is something that he's not sure of either.

The only difference he said he noticed is a lower WGDC when pushing the car at WOT.

So if you're running 17.5psi on meth, when you add downpipes and still run 17.5psi are you technically making no extra power and the only benefit really is just less stress on your turbos?

not sure about you, but less stress on these turbos is worth it in my opinion for the peace of mind... unless you plan on upgrading, it'd definitely be a good idea to run DP's.
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      07-06-2012, 09:25 PM   #3
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I'm sure they're making a little extra power over stock (in addition to the reduced stress). I think the general consensus is they're usually good for at least 10 hp. Problem is, he's making so much power that 10+ hp is only a few percent, and is likely within his statistical run-to-run variance.

If you guys REALLY wanna know if they're making more power, you'll need lots of runs averaged over time, going well back before he got the DP's.
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      07-06-2012, 11:25 PM   #4
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I would believe you would see atleast 10-20 rwhp from DP's and with more supporting mods... I would think that they would run a little more HP than normal and more efficiently.
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      07-07-2012, 01:08 AM   #5
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That's ridiculous. 3" dp's = 15-25whp. Period.
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      07-19-2012, 05:09 PM   #6
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Thanks for the replies guys!
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      07-19-2012, 05:37 PM   #7
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Lets not forget the sound they give you, worth it just for the turbo spool.
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      07-19-2012, 05:47 PM   #8
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Quote:
Originally Posted by SuperBmw View Post
So my friend has a FMIC and meth and he runs about 17.5 psi on his setup.

He said he recently added on downpipes and his quarter mile times didn't change and his 60-130mph didn't really change either. He said he feels no difference and said that the quicker turbo spool is something that he's not sure of either.

The only difference he said he noticed is a lower WGDC when pushing the car at WOT.

So if you're running 17.5psi on meth, when you add downpipes and still run 17.5psi are you technically making no extra power and the only benefit really is just less stress on your turbos?
There are couple things to note to fully understand what is going on here. First and foremost if you keep your boost the same the only benefits to downpipes are usually quicker spool and efficiency. No tune intended for stock turbo's runs a flat 17.5 PSI boost curve. Usually they are 17.5 in the mid-range tapering down at redline.

If he wants to take advantage of the downpipes he needs to tune for it. That would mean he would need to add more boost on the top end range.

What tune is he running and what map? Perhaps it needs some tweaks to find the rest of the potential power.
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      07-19-2012, 05:57 PM   #9
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Quote:
Originally Posted by Jeff@topgearsolutions View Post
There are couple things to note to fully understand what is going on here. First and foremost if you keep your boost the same the only benefits to downpipes are usually quicker spool and efficiency. No tune intended for stock turbo's runs a flat 17.5 PSI boost curve. Usually they are 17.5 in the mid-range tapering down at redline.

If he wants to take advantage of the downpipes he needs to tune for it. That would mean he would need to add more boost on the top end range.

What tune is he running and what map? Perhaps it needs some tweaks to find the rest of the potential power.

He has a 15ohm jb4 map 3 with something like a 45 or 55 additive or something. He runs it through the stock cats with good timing and he said he added the downpipes and tried to up the boost, but he didn't get good timing so he's running the same settings even after the downpipes.
He said to throw on an intercooler and that downpipes weren't even worth the hassle.
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      07-19-2012, 06:10 PM   #10
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DP's offer drooling low-midrange TQ over stockers, that's something that often overlooked.
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      12-17-2012, 01:58 AM   #11
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Quote:
Originally Posted by spool twice View Post
DP's offer drooling low-midrange TQ over stockers, that's something that often overlooked.

I never knew that! that's awful !
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      12-17-2012, 02:08 AM   #12
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Originally Posted by sherif0203 View Post
I never knew that! that's awful !
I think you read that wrong...how is that awful?
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      12-17-2012, 06:18 AM   #13
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Quote:
Originally Posted by Jeff@topgearsolutions View Post
There are couple things to note to fully understand what is going on here. First and foremost if you keep your boost the same the only benefits to downpipes are usually quicker spool and efficiency. No tune intended for stock turbo's runs a flat 17.5 PSI boost curve. Usually they are 17.5 in the mid-range tapering down at redline.

If he wants to take advantage of the downpipes he needs to tune for it. That would mean he would need to add more boost on the top end range.

What tune is he running and what map? Perhaps it needs some tweaks to find the rest of the potential power.
This
Downpipes lower exhaust has turbulence. This means the turbine wheel will spin more freely putting less stress.
Basically downpipes mean better flow which will give you a linear ish increase in power depending on the size of turbo
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      12-17-2012, 08:55 AM   #14
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He said upgrading the intercooler to way better than the factory unit wasn't worth it?.....
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      12-17-2012, 12:10 PM   #15
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Quote:
Originally Posted by Beemw335 View Post
Lets not forget the sound they give you, worth it just for the turbo spool.

+1 on the sound Ar's here
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