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performance drop after installing an exhaust?
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Old 16 Apr 2010, 05:57 AM   #1 (permalink)
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performance drop after installing an exhaust?

I recently got an exhaust system from a friend of mine, which is locally built. (the person who build it is popular for impreza exhausts in the city)

exhaust pipe is welded near under the steering wheel area. the pipe is straight and has a larger barrel and a muffler tip as well. produces a louder noise compared to others, but doesnt have a very deep (low frequency sound) when its compared to other impreza's

after installing the exhaust, i get this feeling. The car is not accelerating like before with the standard exhaust. everyone says thats not possible, it should be atleast a little faster. but still i feel like its not fast like before.

is it really possible? I believe that theres no way to increase the back pressure. If the drop of the back pressure is too much, could that result in a drop in the performance?


Thanks in advance!
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Old 16 Apr 2010, 06:05 AM   #2 (permalink)
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Re: performance drop after installing an exhaust?

You have answered your question fella, yes lack of back pressure isnt all good for performance, its a balance between flow and pressure for any exhaust builder,
have you reset ur ecu since swapping the exhaust ?
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Old 16 Apr 2010, 07:20 AM   #3 (permalink)
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Re: performance drop after installing an exhaust?

nope. i did not reset the ecu. btw, what is the easiest way to reset the ecu? some says that their is a way of doing that with the turning the key 3 times. any idea?
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Old 16 Apr 2010, 07:43 AM   #4 (permalink)
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Re: performance drop after installing an exhaust?

# Ensure engine is at normal operating temperature, turn engine off
# Locate the two ECU connectors, located under the steering column and consist of a black plastic male and female connector, and a green male female connector
# With the ignition OFF connect black to black and green to green.
# Turn on ignition, do not start the engine, depress the accelerator pedal to full throttle, then return it to the half-throttle position and hold for a few seconds, and then release
# Engine Check lamp turns on
# Start engine and then drive for at least one minute, keeping road speed above 11 Km/h.
# ECU is now re-set.
# At this point the check engine light should start to flash the all clear signal (steady 1/2 second interval flashes). If the check engine light does not flash, or indicates some other sequence, there is a fault present in the system, and should be professionally checked for necessary repairs.
# Stop the car and turn off the engine.
# Disconnect the black and green connectors.
# Job done
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Old 16 Apr 2010, 11:11 AM   #5 (permalink)
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Re: performance drop after installing an exhaust?

thanks bugeye_bob for the explanation. will try this the next time and i will post the result. thanks again.
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Old 21 Apr 2010, 09:26 PM   #6 (permalink)
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Re: performance drop after installing an exhaust?

hi ,,thats some cool advice there bob ,,,you make it sound so easy ,,,lol id prob blow the ecu up sky high if i mess with it ,,,but to be honest id rather have a go ,,and with the advice you gave dacolest i recon i might try see if i can do some things myself ,(learn about the car a bit ,lol)

from a new lad ,,cheers
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Old 17 May 2010, 01:51 PM   #7 (permalink)
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Re: performance drop after installing an exhaust?

from what I read in the original post, i would assume that the car is non-turbo, I think the lack of backpressure is what causes the apparent loss of power in low rpms, however you should be able to get a little better high-end performance, if you have an opportunity to measure the car in a dynamometer this should be apparent in the sheets.

regards.
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