Will 3 inch mufflers affect performance? - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 11 Old 04-30-2002, 07:17 PM Thread Starter
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Will 3 inch mufflers affect performance?

Currently i have an O/R H pipe and the American Thunder 2 1/2 in Flowmaster catback. i want it to be louder. If i welded in 3in 2 chamber flows will it harm performance? I do not want one chambers and i want to keep my tail pipes, so no dumps.


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post #2 of 11 Old 05-01-2002, 01:33 AM
 
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Go for it

Some say that larger diameter tips will decrease your performance because-get this-the lower backpressure (haha) affects the exhaust valves in the heads. I think it doesn't make any difference. When you do open up the engines breathing (intake and exhaust systems) it is always best to step up your octane at the pump.

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post #3 of 11 Old 05-01-2002, 01:50 AM
 
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Re: Go for it

Some say that larger diameter tips will decrease your performance because-get this-the lower backpressure (haha) affects the exhaust valves in the heads.

Who the hell said that?

I think it doesn't make any difference. When you do open up the engines breathing (intake and exhaust systems) it is always best to step up your octane at the pump.

WHAT??????? Octane has nothing to do with improved airflow.

Are you going from 2.5" up to a 3" muffler and then down to a 2.5" tailpipe? It will slow the exhaust velocity pulses but that's about it. Shouldn't have too much of a detrimental effect on performance. Personally, I'd leave it alone.

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post #4 of 11 Old 05-01-2002, 01:55 AM
 
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You'd be surprised with some things I read in forums.

I hate to answer your question with a question, but, how doesn't higher octane fuel help to improve performance with a highly modded engine?

I'm more than willing to learn from your experience.
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post #5 of 11 Old 05-01-2002, 09:44 AM
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esandes...You have to need the higher octane fuel for it to improve performance. And...Not all highly modified engines have much higher than stock octane requirement. My car runs fine on 93. With my current tune, I wouldn't gain anything with higher octane fuel.

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post #6 of 11 Old 05-01-2002, 12:24 PM
 
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People who think an overly efficient exhaust won't hurt power, obviously know nothing about cam timing and overlap.
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post #7 of 11 Old 05-01-2002, 05:28 PM
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The stock 4.6 SOHC are notorious for torque losses with completely unrestricted exhausts (headers, o/r pipe, straight flow muffler). I've heard from numerous peeps that the best combo on the stock 96-98 GT heads is o/r pipe and straight flow muffler, but leaving the stock headers to keep a little back-pressure, as adding headers to the combo was dropping the torque too much. The cobra and new heads may be a different story though.

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post #8 of 11 Old 05-01-2002, 07:37 PM Thread Starter
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The setup will be ported 99 heads and the custom grind cams, BBK longtubes, BBK 2 1/2in o/r H, and 2 1/2 in flowmaster american thunder catback. So if i change the mufflers to 3 in, it will go 2 1/2in-3in-2 1/2in. Will i really see a loss with this? If so ill probably just buy the magnapak kit, just trying to cut down on cost.

2003 Silver Cobra Coupe
KB solid axle equipped
641rwhp 628rwtq
[email protected] [email protected] 1.49760ft missed 4th rolled thru the traps


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post #9 of 11 Old 05-01-2002, 08:04 PM
 
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Anytime a pulse hits an area of less or greater volume, a reversion wave is created that heads right back towards the exhaust ports. Depending on the timing of this, it can help you or hurt you. Given your combo, I dont know at what rpm it can become beneficial, if at any rpm. You should stick with the same diameter all the way to the back in my opinion.
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post #10 of 11 Old 05-01-2002, 11:25 PM Thread Starter
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Since most people are saying i should pretty much leave it the way it is i probably will, i dont want to loose power so i dont think im going to even attempt it. I just want it to be a little louder, and i think my only options are magnapaks or dumps, and i do not want to do dumps. So i think im going to shell out the $$ when i get it for the Magnapaks. Thanks for the help guys.


2003 Silver Cobra Coupe
KB solid axle equipped
641rwhp 628rwtq
[email protected] [email protected] 1.49760ft missed 4th rolled thru the traps


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post #11 of 11 Old 05-01-2002, 11:53 PM
 
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Quote:
Originally posted by esandes
You'd be surprised with some things I read in forums.

I hate to answer your question with a question, but, how doesn't higher octane fuel help to improve performance with a highly modded engine?

I'm more than willing to learn from your experience.
esandes,
Octane is an additive that slows the ignition of the fuel. This is necessary in high compression or high heat (read boost) conditions. Both of those lead to preignition, or pinging. The higher octane keeps the air/fuel mix "stable" until ready to be ignited by the spark plug. Lower octane fuel will cause a loss of power in these higher heat conditions because the A/F mix is burning before the piston has passed the high point in it's travel, TDC. High octane fuel in an engine that doesn't need it will cause a loss of power because it takes that much more energy to ignite iit.
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