Muffler Blunder??

blind655

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First a little info.. Engine: 350, intake,Thorley headers, 3" pipes

I started out with a Flowmaster 2-chamber muffler, stock manifolds, and 3" pipes. I changed over to a Borla xr-1 race muffler with the manifolds (yes I know im not a race truck and do not have a race motor
) . Now that I have the headers with the race muffler and the 3" pipes here is my question..Do you guys think that I have too little back pressure? Because with the increased flow with the headers, would it be wise to look in to putting the 2-chamber back on? Any opinions would be appreciated!
Later
Mike

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cleartoy

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So after the headers, do you have a Y pipe, that connects into single 3" into the muff, then dual tail pipes out of it? If so, id say you are fine.

If you had dual exhaust (no Y pipe) with 3" all the way back on each side, that would be a bit much, although ive seen it on a Corvette before.

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blind655

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Yep, after the headers I have a Y in to a single 3" pipe. I still have my cats

A suburban might not be as good as a truck, but it comes damn close with 8 people in it
 

vwguy

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usually the corvettes have an x pipe for tuning purposes

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blind655

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Not that I have too much, but that I have too little. I lost a little low end power, but higher RPM is better. I was just curious if going back to the 2-chamber would give me better over all performance

A suburban might not be as good as a truck, but it comes damn close with 8 people in it
 

Kritter

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leave it how it is and gear it so you are in the higher RPMs all the time

Kris

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tkr

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You will always lose low end torque and increse high end when you reduce your back pressure. I was taught as a general rule, if you have unde 1 lbs backpressure, low end will be significantly affected. With a y-pipe and cat...assuming it hasn't been hollowed out...I doubt you'd have that little pressure. A muffler or repair shop can easily check it at the O2 sensor hole, unless you want to buy the tool yourself.

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FABRICATOR

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Increase top end/decrease bottom end torque:
Larger header pipes
Shorter header pipes
Less back pressure
Larger intake runners
Higher flow carb or throttle body
Longer valve duration (to a point)
Increased valve overlap (to a point)
Advanced valve timing (to a point)
Bigger valves
Open plenum manifold

Increase low and mid range/decrease top end torque:
Smaller header pipes (to a point)
Longer header pipes (to a point)
More back pressure (to a point)
Smaller intake runners
Airflow matched to demands (raised velocity)
Bigger valves with less cam
Dual plenum manifold

Things that help both:
Higher compression
Bigger valves (depending on cam, etc.)
Arrange headers for better scavenging
Roller cams

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Tim

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Is a supertrapp a good way to go so you can tune your exhaust for the desired back pressure? Is a supertrapp a good option for late model trucks with nothing else done to the engine or should they be used on more highly modified engines? anyone? tim
 

Dave_G

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Re: I changed over to a Borla xr-1 race muffler with the manifolds

Mike,
Looks to me like your in clear violation of California Vehicle code CVC.27151 (a)

Hehe......

Dave

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BIG_FAT_LOSER

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What benifit, if any, is there to removing catalytic converters on cars anymore? I thought that was a late 70's early 80's thing.


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fishd00d

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I took mine off and bolted in a straight pipe. It made it a lot louder and I noticed a little gain at High RPM's.

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Ryno

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Blind-

Unless you are running a big cam (over .500 lift), and large valve heads, bail the race exhaust. As for the headers, they should be no larger than 1 5/8 tubes. going from a 3 chamber to a 2 chamber muffler does nothing but increase NOISE. I would bail that pricey borla muffler, get a decent 3", and run the tailpipe. I have a 3" exhaust on my Z71, and it improved all around, but I also built a 300hp motor, so it helps out all around.

Pat-

Taking off the cats does nothing but cause hassles when it's smog time. Taking them off also increases noise.

Ryno

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geoff

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Amen. Once i finish my honda's new fuel system, im getting started on my 22r turbo project.

If anyone cares, here are some of the manifolds i make...










22r manifold should be done soon...


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geoff

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Hey a couple comments on your list...

for the high rpm power actually a longer header runner will increase top-end. Think a super long 4-1 header. 4-2-1 headers (shorty type) will traditionally give a bit more torque, but they are usually just easier to fit and make. So i think you may have those two switched... no biggie

also for equivalently sized intake runners, longer are usually torquier and shorter are more high rpm oriented.

what weve found is generally that bigger valves do make power but will (obviously) lose some mileage.

Also contrary to traditional/popular belief, you can use an ultra aggressive cam and make good power on boost. It will often allow the turbo to spool quicker and make even more top end power, but make the turbo rev super high, so check the compressor efficiency maps... im getting off topic here.

Im sure you knew this stuff but figured id just mention it.


"We are the music makers, and we are the dreamers of the dreams." -- Willy Wonka
 

blind655

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I might go back to the flowmaster in a while when I get a little extra money to kick around. Where did the taking off cats come from, I still have them
Oh yeah I am in CLEAR violation California Vehicle code CVC.27151 (a) and loving every minute of it!


Anyway thanks for the info everyone

Later
Mike

A suburban might not be as good as a truck, but it comes damn close with 8 people in it
 
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