Weight reduction vs power loss? (Removing mufflers) - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

Jason@JacFab · 07-31-2011, 02:28 AM

I've been doing a lot of reading the last couple hours on weight reduction, muffler deletes, which brings up my question/theories...

I've always been a big fan of back pressure in an exhaust system... For the most part, there is a reason certain vehicles come with certain mufflers, resonators, and so on... Does that mean they are the right ones?? No. Mufflers, and exhaust can be changed to gain power... But more often than not, on stock engines, I've seen completely free flowing exhausts actually loose power due to lack of back pressure... These are my theories, I've seen it on the dyno time after time, but most of my dyno experience has been around smaller engines (motorcycles, quads, go karts, etc), I don't know if cars are AS sensitive, but I assume it still comes into play.

I haven't found any threads that actually claim, or deny any power gain, or power loss from the muffler delete via a dyno chart. I've seen people say it does help... I've seen people say it doesn't help... Which brings me to my current position:

I'm going to pull as much random crap out of the car that I can before I head out to the drag strip next time. Not gonna get outrageous, just the rear seats, passengers seat, empty the windshield washer bottle, pull out the tire repair stuff and jack, remove engine cover, run 1/4 tank of gas, and that pretty much covers it...

I've got the Dynomax #39494 axleback system on my car, and while the mufflers aren't as heavy as stock ones, I think I can shave another 30-35lbs by removing the mufflers as they are just clamped on.

The car already has an x-pipe and resonator delete... I'm just wondering if (power wise) it would be better to leave the mufflers on, or if the power won't be effected enough and the 30lb extra weight loss would be a better benefit?

This would be strictly for race day... After that everything goes back on the car.

axis · 07-31-2011, 08:03 AM

I would go into the full blown explanation but there are already a few threads on this that explain it in detail. A quick search should turn them up. There's also a ton of info via google. Basically, losing HP/tq by going to a free'er flowing exhaust is a myth. Old timers tell you this because they were use to carb''s that didn't have the ability to change the AFR when you make changes, thus the cars ran too lean. In the end, it's not a back pressure issue, it's a tuning issue. Since all newer cars have a PCM to adjust the AFR, it's not as much of an issue. It can still be an issue since they can only adjust so much. For your intended setup, it shouldn't be a problem as long as you leave the Xpipe in place. These cars will lose HP without a crossover.

SGOS252382 · 07-31-2011, 08:21 AM

That's a lot of work (taking out the rear seat, passenger seat, emptying washer bottle, etc) just for some runs down the strip. But you will run about .1 tenth faster by doing so.

I always run my car full weight (I never remove anything). But I do have lighter 20" wheels. I also have a full exhaust. Those mods save weight. But I'm way too lazy to remove seats, etc just for a day at the track.
I also want to know what my car runs (as it rolls down the street).

But on average, your car will run about .1 faster for every 100 lbs of static weight removed.

07-31-2011, 02:28 AM	#1
Jason@JacFab Drives: 2016 1LT RS Camaro; 72 Chevelle Join Date: Apr 2008 Location: Central Point, OR Posts: 5,688 View My Garage	Weight reduction vs power loss? (Removing mufflers) I've been doing a lot of reading the last couple hours on weight reduction, muffler deletes, which brings up my question/theories... I've always been a big fan of back pressure in an exhaust system... For the most part, there is a reason certain vehicles come with certain mufflers, resonators, and so on... Does that mean they are the right ones?? No. Mufflers, and exhaust can be changed to gain power... But more often than not, on stock engines, I've seen completely free flowing exhausts actually loose power due to lack of back pressure... These are my theories, I've seen it on the dyno time after time, but most of my dyno experience has been around smaller engines (motorcycles, quads, go karts, etc), I don't know if cars are AS sensitive, but I assume it still comes into play. I haven't found any threads that actually claim, or deny any power gain, or power loss from the muffler delete via a dyno chart. I've seen people say it does help... I've seen people say it doesn't help... Which brings me to my current position: I'm going to pull as much random crap out of the car that I can before I head out to the drag strip next time. Not gonna get outrageous, just the rear seats, passengers seat, empty the windshield washer bottle, pull out the tire repair stuff and jack, remove engine cover, run 1/4 tank of gas, and that pretty much covers it... I've got the Dynomax #39494 axleback system on my car, and while the mufflers aren't as heavy as stock ones, I think I can shave another 30-35lbs by removing the mufflers as they are just clamped on. The car already has an x-pipe and resonator delete... I'm just wondering if (power wise) it would be better to leave the mufflers on, or if the power won't be effected enough and the 30lb extra weight loss would be a better benefit? This would be strictly for race day... After that everything goes back on the car.

07-31-2011, 08:03 AM	#2
axis Search Ninja Drives: 2010 Black 2SS/RS A6 Join Date: Oct 2009 Location: Central Ark Posts: 7,183	I would go into the full blown explanation but there are already a few threads on this that explain it in detail. A quick search should turn them up. There's also a ton of info via google. Basically, losing HP/tq by going to a free'er flowing exhaust is a myth. Old timers tell you this because they were use to carb''s that didn't have the ability to change the AFR when you make changes, thus the cars ran too lean. In the end, it's not a back pressure issue, it's a tuning issue. Since all newer cars have a PCM to adjust the AFR, it's not as much of an issue. It can still be an issue since they can only adjust so much. For your intended setup, it shouldn't be a problem as long as you leave the Xpipe in place. These cars will lose HP without a crossover. __________________ 2010 Black 2SS/RS A6 Halltech CF 102 fed GPI modded intake manifold Bo (knows) White ported TB Kooks LT's/ Dynomax VT Pfadted (springs/sways) Dyno tuned by Rhino and GPI I once parallel parked a train.

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07-31-2011, 08:21 AM	#3
SGOS252382 Drives: 2010 Camaro 2SS/RS Join Date: Mar 2008 Location: S.W. Florida Posts: 6,294	That's a lot of work (taking out the rear seat, passenger seat, emptying washer bottle, etc) just for some runs down the strip. But you will run about .1 tenth faster by doing so. I always run my car full weight (I never remove anything). But I do have lighter 20" wheels. I also have a full exhaust. Those mods save weight. But I'm way too lazy to remove seats, etc just for a day at the track. I also want to know what my car runs (as it rolls down the street). But on average, your car will run about .1 faster for every 100 lbs of static weight removed.