Hey guys,

I decided to take my muffler off of my '99 Camaro SS to see how my car would sound without it and there is a very noticeable loss in horsepower and response when I punch it. It has longtube obx headers, y-pipe, cats. I took the magnaflow muffler and tips off and it sounds SO much better, but it feels quite a bit slower now. It dumps out at a 2.5" pipe. Is that too wide? I'm guessing I need more back-pressure. It used to have dual 3" tips after the muffler and I didn't really like them, which is another reason I took them off. Ideas? Suggestions?

 

Look for knock retard man!

 

Explain a little more? I didn't cut anything off. Just unbolted and wiggled everything out, so I can put it back on if need be.

 

If the engine is picking up allot of chatter from not having mufflers in place it will retard timing and kill power.

 

I forgot to mention that it also has a cam in it. Any difference?

 

Sounds like the car might have to learn how to run without the excessive back pressure. The exhaust is not too free flowing with 2.5" tho.

I remember when I took my flowmaster exhaust off my old car and swapped on a bullet muffler. It seemed like it was slower and had a weird throttle response, but after about 100 miles it was better than before.

If it doesn't fix itself, try putting a bullet muffler on your car. If not, you'll probably have to get it re-tuned or put the old muffler on it.

 

Just give your PCM a chance to learn like was said above.

I don't see why it'd be your knock sensors . Cause i myself run lt's hooked to a 3 inch y and it's not catted and has no mufflers either. I have 0 problem with my knock sensors

 

All Im saying is its worth a look. He asked for ideas and suggestions. I think if you really want to know, log the car and look at the log. False knock can happen when the sensors pick up the noise. Logging is the only real way to see if its adding/taking fuel, or if its retarding timing. Your only guessing until then.

 

You need backpressure!!!!









HAHAHAHA!!!
How do you know it really lost power? My car feels like it has more pep and has better throttle response with my full exhaust on it, but it'll run .2 sec quicker in the 1/8 with it dumped at the axel. The butt dyno isn't very accurate. Go test it at a track or put it on a dyno to know for sure. It might just pull more linear now instead of peaky down low.

 

have you had the car tuned?

 

It was tuned before I dumped the muffler. I can get it retuned next weekend though.

 

The reason is with the exhaust out the back you feel the torque more than when dumped but alas, you exchange more HP and give up some torque, so it might feel better before going open exhaust. this is USUALLY the case, but not always.

 

If the knock sensors were being set off, it'd throw a CEL immediately.

Shannon is also right about the torque/hp curves.

But I still think that you need to give it some time to re-learn itself. These cars constantly adapt to what's going on.

Ever notice how your car seems sluggish after you putt around town for a whole day? And then you hammer it a couple times getting on the highway and it starts to feel really peppy again?

 

you probably didnt lose anythin, just your butt dyno is off. if anything you mightve gained a lil. not lose.

 

nah you just need to cut more of your exhaust off, actually **** it just take it all off and run an open head. **** will sound nasty and flow like a mother ******. exhaust scavenging is just a myth...

 

^

only real men rock no exhaust, open heads.

 

I was there. Car got extremely slower. Slower then my car was bolt on only. I'm thinkng it has to relearn itself. Hell, I put a shift light in my car and it had to relearn how to idle.

 

Less restrictive exhaust = less torque/more hp (theoretically). Restrictive exhaust = more torque/less hp. Same difference if you have dual cutouts. It'll feel faster when they're capped.

 

you are almost right. it's not rescrictions that give you torque. idk who told you that(or anybody else) it's smaller diameter tubing that sees and increase in low end torque. by having a smaller diameter and effectively less volume to fill, the exhaust gasses move through the system at a higher velocity.(aka it's more effecient at a lower rpm)

when you cut the muffler off of a car's exhaust a few things happen:

1) the heat dissapating effect increases, which means the exhaust gas temps are going to fall dramaticaly. cold gas is heavier than hot gas, and as a result it's harder to move.(a cut out is usually pretty close to the headers, which means the gas is still hot when it exits)

2) the pulsing effect changes(energy waves). long tube headers will stack pulses losely where as stock manifolds stack them tightly. but either way each pulse through a system sucks the next one along.(just like high and low pressure systems in weather) the problem lays when you make these pulses irregular. part of a mufflers job is to keep them regular through the length of the exhaust system. but don't get it twisted you CAN do this with out a muffler.

3) another job of a good muffler is reducing the reversion wave, which is a wave that reverberates back up to the head and exhaust valve. another way to help reduce this is by having equal length pipes with a good crossover or merge(paired with a good muffler)

remember an exhaust system can not create power or torque it can only sculpt it.

 

Will it be ok to run with LT headers & 3" Y pipe open @ the end of pipe ??