Lost power after exhaust set up

Veloc

3,000 RPM
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May 19, 2010
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Guys... Need your expert opinions and preferably experience here...

I did 2 things today to my exhaust. After doing these, I felt that it has lost significant low end to mid range torque and also responsiveness. I haven't tried high rpm. Going to try later but I have a feeling its also bad. I did 5k rpm just now and the power doesn't even come yet. I am trying to figure out which of the 2 things made me lost power.

1. I change my tertiary extractor pipe to a more free flowing one. Just a short section of about 40 cm. 4AGE blacktop has as area at the exhaust where is it squashed/tapered. All aftermarket extractors replaced this section with a smooth pipe. Some people replaced only this section because it is known to be the most restrictive part of the exhaust. Refer to picture. I used quite a standard diameter 2.3".




2. I added one more midbox. My set up now is stock extractor > midbox > midbox > s-flow muffler. Previously was extractor > midbox> muffler. I thought I can add another bullet just to silence it more since already decat. They usually recommend to replace the cat with a bullet if decat to reduce noise. But I chose a midbox instead because it can reduce more noise.

Do you guys think it's caused by the change in pipe to a free flowing one, or the addition of another midbox? :adore:


Thanks!!!


P.S - Pls do not decat. Pls do not curve me coz bugger shop removed mine without telling last time.


**********************************************************************************

UPDATE: Did a mild spirited driving with slightly high load (70-80% throttle) up to about 7000 rpm. Couldn't go full because on RON95 now. The top end power seems to be the same if not a little better. Power delivery is also smoother. Previously, the engine seems to have something stucking up its power at low revs. Once reach ~5000 rpm, there is like a sudden release and I feel the "push". Now, the push is a bit gentle and spread out over time. The transition is smooth. It takes about 2 secs for the power to build up instead of a sudden release of power.

Another observation... Significantly reduced knocking even using RON95!!! Previously, I could go more than 50% throttle and dare not pass 6000 rpm when using RON95. Now there is almost no knock.
 

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6UE5t

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Hmm I suspect the no.1 is the cause. Your pipe diameter seems a bit too big for such an engine.
 

Veloc

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Hmm I suspect the no.1 is the cause. Your pipe diameter seems a bit too big for such an engine.
Yup now I think so too.
 

vr2turbo

Beyond 20,000 RPM!
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The squashed pipe design is original? Looks like the hurricane mid box those days which is round but they clamped it into a square at 2 inch intervals....
I suspect lack of back pressure therefore loosing low end but having more free flow you are now getting better high end...
 

^pomen_GTR^

7,000 RPM
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delete one midbox...and use 2" piping will be enough...
 

Veloc

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^pomen_GTR^

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So.... You think its the extra midbox too..
more box=more restriction in the system...

if it wasnt for lower sound level...i will use straight pipe exhaust any time any day :biggrin: (with proper size and length surely)
 

vr2turbo

Beyond 20,000 RPM!
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more box=more restriction in the system...

if it wasnt for lower sound level...i will use straight pipe exhaust any time any day :biggrin: (with proper size and length surely)
My VR no box all the way until straight through muffler at the rear......:driver:
 

^pomen_GTR^

7,000 RPM
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My VR no box all the way until straight through muffler at the rear......:driver:
straight 3" pipe all the way from turbo to the back of my foz too :biggrin: rear box just FGK legalis super R...big and long.... :rolf:
 
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Veloc

3,000 RPM
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May 19, 2010
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more box=more restriction in the system...

if it wasnt for lower sound level...i will use straight pipe exhaust any time any day :biggrin: (with proper size and length surely)
My VR no box all the way until straight through muffler at the rear......:driver:
straight 3" pipe all the way from turbo to the back of my foz too :biggrin: rear box just FGK legalis super R...big and long.... :rolf:
You guys.... So young and furious :biggrin:
 

KenDiriwan

1,000 RPM
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Mar 15, 2006
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Mind i inquire, were you using stock full set of system for 20v ? Or just swapped engine, still using default exhaust system. And yes, too much of enlargement on header with stock engine will suffer terrible loss. Tested through dyno.

Wana keep it? Increase your engine power.
 

Veloc

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Mind i inquire, were you using stock full set of system for 20v ? Or just swapped engine, still using default exhaust system. And yes, too much of enlargement on header with stock engine will suffer terrible loss. Tested through dyno.

Wana keep it? Increase your engine power.
When I swapped engine, I do not have the 20V exhaust. So I fabricated one with approximately the same measurements as stock.

Stock header > decat > 2.1" inner diameter piping > 1 midbox > S-flow muffler.

That was great response and torque throughout the rpm range. Now after i added one midbox and free up the factory squashed section, feels like horseshit.
 

hex999

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Oct 27, 2011
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Go to jian hang Batu Caves and let a professional decide on your exhaust setup. He has a money back guarantee policy. Overall better workmanship and less headache
 

KenDiriwan

1,000 RPM
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Mar 15, 2006
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When I swapped engine, I do not have the 20V exhaust. So I fabricated one with approximately the same measurements as stock.

Stock header > decat > 2.1" inner diameter piping > 1 midbox > S-flow muffler.

That was great response and torque throughout the rpm range. Now after i added one midbox and free up the factory squashed section, feels like horseshit.
Each curves at header plays a role, be it inlet diameter, how long the curve is and how long is section of 4/2/1. Without proper understanding an output of the engine a simple mod could just contribute loss rather gain. For your engine, i recommend FGK 4-2-1, improves almost all range from low to high rpm even for a stock heart. Private me if you interested.

Go to jian hang Batu Caves and let a professional decide on your exhaust setup. He has a money back guarantee policy. Overall better workmanship and less headache
Not possible unless bro Veloc willing to ship to car over from Borneo just for sake of exhaust.
 

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