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I think you might not want to go straight pipes. Going to lose some power. Call if you think you want to learn more about this. We tried this and it was a failure from a power point of view.

ROAD/RACE
 

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Discussion Starter #5
Noooooooo not the kiss of death from Road Race!! I can handle the average forum goer telling me I'm going lose power but not the pros. I think I'm going to be sick.


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Discussion Starter #6
Here it is. Video to come. Now are we talking about LOST power or no gains. The first I can deal with no gains but not lost power. Even though I did this mostly for the sound and hopefully better gas mileage.


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Discussion Starter #7
Also FYI this cost $100 and my wife about killed me so there was no way I was getting into an axle back system. Sorry R/R. I dig your work though. I have been eying an engine cover. Maybe for Christmas?


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Torque will
be the biggest LOSS and you will
feel it


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Low end torque, but more top end from my set up
 

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Here it is. Video to come. Now are we talking about LOST power or no gains. The first I can deal with no gains but not lost power. Even though I did this mostly for the sound and hopefully better gas mileage.


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So then to pick up your bit of LOST power, you just need a little back pressure to scavenge the cylinders a bit more. Drop a reducer washer in the exit pipe about 8 to 10 inches before the end. If the i.d. of the pipe is 1.25" make the inside diameter of the reducing washer 1.125" with a slight chamfer on either side of the venturi area of the washer. Drill two cross holes thru the pipe, locate washer by putting a piece of copper wire thru a pair of the holes, plug weld the other two holes & washer, pull out wire and repeat plug weld. Effectively, what you did was put a 1 1/8" restrictor plate to rebuild some of the back pressure LOST with your modification.
 

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Losing low end torque is ok if you get more over 3k...since if you step on it its only under 3k for about 1/3rd of a second :) I kept my resonator to keep a little back pressure....not sure if it helps but I dont feel lost torque
 

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I think you might not want to go straight pipes. Going to lose some power. Call if you think you want to learn more about this. We tried this and it was a failure from a power point of view.

ROAD/RACE
I respectfully disagree that changing the Fiat exhaust system from a 2" diameter cat - resonator - muffler system to the same system minus muffler causes power loss. Having done this to my car i noticed a slight improvement in mid-high rpm performance and no real noticable change at idle to mid rpms.

From my viewpoint if one is expecting much of any power gains from a cat back exhaust change on a Fiat they will be sadly dissapointed. Why? because any real power gains to be made on the factory exhaust exists in the area that cannot be changed without making the car an off road only vehicle.

The real power gains to be made is ditching the stock manifold and cat for a long tube header in a 4-1 or 4-2-1 configuration, depending on R&D. And since that negates the existing emission controls and will throw codes in the ECU, it's not going to happening any time soon.

Exhaust systems are typically changed to improve tone to a sportier sound when talking an install on a street car. BUT you can lose power if the system is not designed correctly for the given application.
 

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My removal of the muffler at the absolute end of the exhaust system for a straight pipe is a small change in the right direction for making street worthy modifications.
 

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Seems like zonk and I did the same thing, I posted vids (2) on youtube but recordings aren't as nice as the real thing obviously, still I feel it sounds nice in person and on video. :) Hope this link works for those that'd like to hear it, I think this is before I added the RRM intake and ECU tuner so I should probably do another as it sounds different, won't happen soon though. Links: http://www.youtube.com/user/Tw3akst3r?feature=mhee
 

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Discussion Starter #20
Actually as it turns out I have some time now. I have heard all these conflicting things about back pressure and torque but im not sure what to believe. I am not an engineer but it makes logical sense to me that by decreasing the amount of work that the piston must do in order to evacuate the cylinder during the exhaust stroke would only help the performance. I have also heard about exhaust gas velocity which makes sense and the reason that race teams dont use 5" exhausts. Im still unsure and I think we need some dyno results.

About the new exhaust. It sounds a lot like Tweaks. I have a short ram intake and it sounds pretty BA to me, but im sort of a hooligan when it comes to that stuff. I do have to say that it is almost silent in the car with the windows up, but when you get on the throttle it wails for sure, I left the stock resonator on and it does its job because there is no resonance at all. Also I believe if I took that off as well and ran a true straight pipe from the cats back it would be unreal loud, and I am a fan of loud exhaust.

I will do my best to post a video tomorrow. The sound is extremely hard to describe.
 
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