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Old 02-19-2004, 09:50 AM   #1
heffergm
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Default Downpipe without engine management?

All,
I'm thinking of bolting on a Bosal downpipe, but I have no engine management (ecu is stock, no boost controller, etc).

Would this be a problem, or is the stock ECU capable of dealing with change?
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Old 02-19-2004, 10:04 AM   #2
vile
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nope....don't need it. none of the exhaust upgrade, up, dp, tbe will require engine management. however, if you did have it, it would definitely help in getting even mo'powa'

cliff notes: not required, but nice to have
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Old 02-19-2004, 10:44 AM   #3
MikeWRX-NJ
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yup, vile is correct. unless you are changing the way the engine breaths as far as boost is concerned, you don't NEED EM. but it's nice to have
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Old 02-19-2004, 10:45 AM   #4
heffergm
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What kind of HP gains can I expect from a downpipe without engine management? I'm guessing in the 20HP range, in which case I'm not sure it's really worth the effort.
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Old 02-19-2004, 11:44 AM   #5
MikeWRX-NJ
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well if you just did the downpipe and left the rest of the system in place, probably not a lot of power. 10whp probably. if you did the entire turbo-back + upipe with the right parts you could see ~20whp.

I would do all of it at once, save up and get all the parts together because you'll save a lot of work.
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Old 02-19-2004, 12:17 PM   #6
heffergm
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Well, I've already got a prodrive axle-back. So if I just bought a downpipe that replaced both cats (anything except Bosal or Stromung basically), I'd be set from the turbo-back.

I'm not equipped to do an uppipe install however, so I'll be leaving that alone for the time being.
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Old 02-19-2004, 01:02 PM   #7
turca
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Take boost creep into consideration.I installed helix downpipe and apexi midpipe and muffler last week and now i have a serious boost creep.In the third gear my peak boost is 1.2 bar in the fourth it is 1.3.
I guess i should port the wastegate hole and i will do it on tuesday.
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Old 02-19-2004, 01:43 PM   #8
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true, as always a boost gauge is should be your first mod.
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Old 02-19-2004, 01:45 PM   #9
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Quote:
Originally posted by turca
Take boost creep into consideration.I installed helix downpipe and apexi midpipe and muffler last week and now i have a serious boost creep.In the third gear my peak boost is 1.2 bar in the fourth it is 1.3.
I guess i should port the wastegate hole and i will do it on tuesday.
this is with stock (ecu) boost control?

my mbc has no issue with a catless, straight through exhaust. i doubt it's boost creep, at least as the traditional description of it stands (wastegate unable to keep up with exhaust flow during high boost/high rpm conditions).

jm2c
ken
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Old 02-19-2004, 01:47 PM   #10
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Quote:
Originally posted by heffergm
What kind of HP gains can I expect from a downpipe without engine management? I'm guessing in the 20HP range, in which case I'm not sure it's really worth the effort.
20 hp not worth the effort???

i'd GLADLY pay what my dp cost to get another 20hp right now!

ken
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Old 02-19-2004, 01:53 PM   #11
turca
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ride5000
I see 1.3 bar in the 4th gear but it drops to 0.9 or 1 bar.I guess it is boost creep, isn't it? I have a stock turbo with uppipe and TBE.It doesn't stay at 1.3 bar continously it just reaches 1.3 and then drops down...
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Old 02-19-2004, 02:10 PM   #12
heffergm
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I've got a boost gage. 1.3 bar is an awful lot of boost... in fact, isn't that like 18psi?

That's definitely NOT good.
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Old 02-19-2004, 03:29 PM   #13
Jon [in CT]
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Quote:
Originally posted by vile
nope....don't need it.
Subaru, of course, would disagree. On p. 7 of this WRX engine article from Subaru, there is this:
Quote:
Exhaust Diameter

The diameter of the exhaust system will vary the pressure difference across the turbine. A larger exhaust allows the turbocharger to rotate faster, which results in higher boost pressures. Any increase in boost pressures would require ‘re-mapping’ of the ECM programs to accommodate different air flow rates and resultant ignition change requirements. Over speeding of the turbine can lead to turbocharger failure, particularly in conjunction with the increase in the pressure differential across the turbine.
Not that I necessarily agree with that — just thought you should be aware of Subaru's view.
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Old 02-19-2004, 04:25 PM   #14
Hit Man X
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Quote:
Originally posted by heffergm
What kind of HP gains can I expect from a downpipe without engine management? I'm guessing in the 20HP range, in which case I'm not sure it's really worth the effort.
20whp is a lot for this car. I tossed on my DP first before the Unichip and the car pulled a lot better all over but far better over ~4500rpms to redline.
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Old 02-19-2004, 09:34 PM   #15
Evan
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Another thing is that the DP will allow the turbo to spool up earlier. A turboback is probably good for a PEAK gain of 20hp, but there's even bigger gains in the lower to mid-range.

Edit: Actually, what I should say is that there are big gains in torque in the low/mid range.
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Old 02-19-2004, 10:11 PM   #16
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Quote:
Originally posted by ride5000
20 hp not worth the effort???

i'd GLADLY pay what my dp cost to get another 20hp right now!

ken
what he said
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Old 02-20-2004, 12:38 AM   #17
Woody643
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Default no management

H,

I gutted my own uppipe and installed a Bosal twin dump downpipe. I also left the stock third cat in place, but added the pony express mil eliminator.

The car runs great, and even better after screwing in the wastegate actuator arm 2 full turn. Beware, the car will haul booty after you turn in the arm, but the computer will "detune" the boost level after a few weeks. I didn't see spiking or anything, it was just that the car was on boost at very minimal throttle. Don't misunderstand, the car is still very fast and pulls noticeably (about $250) harder than stock. I could tell that the computer was adjusting to my mechanical wastegate adjustment by the amount of throttle pressure to get the desired part throttle acceleration. (the computer after a while seemed to take the "edge" off of the car).

I don't have any management yet, as I am still saving for Cobb stage II. At this point, I even get slightly better gas mileage if I can keep my foot out of it!
Woody
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