!!!!backfire!!!

**pmolina0436** · 09-24-2008, 10:13 AM

Just wondering why "backfire" happens..Is it cause an engine problem, or would be the exhaust??

**Tide** · 09-24-2008, 10:25 AM

Typically happens due to a lean condition, which can be a result of several different problems (intake leak, bad MAF, bad spark timing).

When did it happen? On start up? During an upshift?

It can also happen as a result of too rich of a AF ratio (excess fuel being sent through the exhaust, temperatures in the headers, x or h pipe or mufflers ignite it).

**0rion** · 09-24-2008, 10:38 AM

the first thing is to define backfire. I see a lot of people calling exhaust popping backfires. The exhaust will pop the more freely it flows and is normal. Backfires are different though and not normal.

**Sarge** · 09-24-2008, 01:01 PM

Backfires in a fuel injected car is rare. I bet your talking exhaust backfire from an exhaust leak allowing cold air into the exhaust stream causing an explosion....popping....

**pmolina0436** · 09-24-2008, 01:02 PM

Originally Posted by 0rion

the first thing is to define backfire. I see a lot of people calling exhaust popping backfires. The exhaust will pop the more freely it flows and is normal. Backfires are different though and not normal.

This might be the issue on mine..i do have a free flowing exhaust, with the LT, Cat-Less.....that might be it...cause when im driving it sounds fine, nothing not-normal...but on idle, when i rev-it, it sounds like a little pop..nothing really loud, but it happens a little more on the higher RPM (on idle)..

**pmolina0436** · 09-24-2008, 02:12 PM

Originally Posted by Sarge

Backfires in a fuel injected car is rare. I bet your talking exhaust backfire from an exhaust leak allowing cold air into the exhaust stream causing an explosion....popping....

if this is the case...will it hurt my car??or HP???

rednari · 09-24-2008, 04:35 PM

From what you described, the popping is probably being caused by a slight exhaust leak. When you rev the motor and let off, a high pressure area is created in the exhaust system which is immediately followed by a vacuum. Cold air is drawn into the system at that point, causing the popping. The car is fine.

I had an old GMC with a 262 V-6. When deaccelerating during slow to moderate speeds, no popping occured. If you were going 60 or faster and let off the accelerator quickly, a loud pop or sometimes even an explosion would occur. Because of these explosions, the truck of course had no muffler.

The truck was a daily construction driver, and after not experiencing an explosion for awhile, it was decided to replace the muffler. I dropped off one of my guys at the muffler installer to pick up the truck. I followed the truck onto the expressway and upto cruising speed. About 10 minutes later, a sudden stop on the highway made my guy let off the accelerator quickly.

The resulting explosion caused a shock wave I could feel inside my car from a block away. And it was loud! It sounded and looked like a grenade went off under the truck. $150 worth of exhaust work gone in a flash of orange as well as wasted morning putzing around with truck repairs.

Later, I decided to junk the truck but was talked out of it by one of my guys who stated he could fix it. You did not need to be a genius to understand the exhaust valve would stick open intermitently at higher speeds, which allowed unburned gasoline to enter the exhaust. When the sticking valve released and closed upon deacceleration, this allowed the cylinder to fire and the resulting hot exhaust stream to enter a hot exhaust system filled with vaporized and heated gasoline.

Needless to say, after doing a valve job the truck never lost another muffler. Your problem is nowhere near this. You are simply drawing in cold air from a slight exhaust leak and not gasoline. You have nothing to worry about.

**pmolina0436** · 09-24-2008, 06:06 PM

Originally Posted by rednari

From what you described, the popping is probably being caused by a slight exhaust leak. When you rev the motor and let off, a high pressure area is created in the exhaust system which is immediately followed by a vacuum. Cold air is drawn into the system at that point, causing the popping. The car is fine.

I had an old GMC with a 262 V-6. When deaccelerating during slow to moderate speeds, no popping occured. If you were going 60 or faster and let off the accelerator quickly, a loud pop or sometimes even an explosion would occur. Because of these explosions, the truck of course had no muffler.

The truck was a daily construction driver, and after not experiencing an explosion for awhile, it was decided to replace the muffler. I dropped off one of my guys at the muffler installer to pick up the truck. I followed the truck onto the expressway and upto cruising speed. About 10 minutes later, a sudden stop on the highway made my guy let off the accelerator quickly.

The resulting explosion caused a shock wave I could feel inside my car from a block away. And it was loud! It sounded and looked like a grenade went off under the truck. $150 worth of exhaust work gone in a flash of orange as well as wasted morning putzing around with truck repairs.

Later, I decided to junk the truck but was talked out of it by one of my guys who stated he could fix it. You did not need to be a genius to understand the exhaust valve would stick open intermitently at higher speeds, which allowed unburned gasoline to enter the exhaust. When the sticking valve released and closed upon deacceleration, this allowed the cylinder to fire and the resulting hot exhaust stream to enter a hot exhaust system filled with vaporized and heated gasoline.

Needless to say, after doing a valve job the truck never lost another muffler. Your problem is nowhere near this. You are simply drawing in cold air from a slight exhaust leak and not gasoline. You have nothing to worry about.

Thanks man..really good info..thank god my baby is still good to go...

**0rion** · 09-24-2008, 09:33 PM

yep, it sounds like you're fine. Sounds to me to be just the result of free flowing exhaust. What exhaust set up do you have on the car?

**pmolina0436** · 09-25-2008, 04:40 AM

Originally Posted by 0rion

yep, it sounds like you're fine. Sounds to me to be just the result of free flowing exhaust. What exhaust set up do you have on the car?

Right now i have the pacesetter LT, connected to x-pipe, with stock 05 mufflers..ill probly delete the mufflers and input the loudmouth I bullet type mufflers...what you think

**0rion** · 09-25-2008, 06:10 AM

Originally Posted by pmolina0436

Right now i have the pacesetter LT, connected to x-pipe, with stock 05 mufflers..ill probly delete the mufflers and input the loudmouth I bullet type mufflers...what you think

it'll be loud

and raspy but it's all personal preference. I don't mind some rasp. If it were up to me I'd run open cutouts all the time.

Have you looked at spintech's? Expensive but have a great sound to them.

**pmolina0436** · 09-25-2008, 01:01 PM

Originally Posted by 0rion

it'll be loud

and raspy but it's all personal preference. I don't mind some rasp. If it were up to me I'd run open cutouts all the time.

Have you looked at spintech's? Expensive but have a great sound to them.

Yea i was looking at some Spintech, but i havent heard them...i have only heard them when you buy the hole cat-back exhaust system together..i just want the mufflers though...would they sound the same if i only put the muffler connected to my setup i have now..?..

**pmolina0436** · 09-25-2008, 01:03 PM

all the stock GTO have 2 1/2 pipes right ????inlet and outlet

**0rion** · 09-25-2008, 03:49 PM

Originally Posted by pmolina0436

all the stock GTO have 2 1/2 pipes right ????inlet and outlet

yep

here's a vid of ps lt's, spintech catback, and an H-pipe.

**Mich's04** · 09-25-2008, 03:51 PM

My goat does does the same thing when I decelerate. The slip joint connections at the mufflers have some slight leakage. Enough to allow the exhaust to pop or backfire. I kind of like it though. It'll make heads turn.

Not to get off the subject, I was at Watkins Glen Raceway over the weekend and got a chance to run the goat around the long course. Man that exhaust on my car was really popping after coming off the gas at 115 mph straight away into the curve. That definitly got some onlookers attention.

**pmolina0436** · 09-25-2008, 07:30 PM

Originally Posted by 0rion

yep

here's a vid of ps lt's, spintech catback, and an H-pipe.

Damn..it really sounds good..thats what i want....but that is the HOLe CAT _BACK EXHAUST RIGHT???i really dont want to spend 500-to 700 on an exhaust..<----with that money its probly better to get a 92mm FAST intake...i just want the mufflers...would they sound alike with my exhaust i have now..

**0rion** · 09-25-2008, 11:16 PM

Originally Posted by pmolina0436

Damn..it really sounds good..thats what i want....but that is the HOLe CAT _BACK EXHAUST RIGHT???i really dont want to spend 500-to 700 on an exhaust..<----with that money its probly better to get a 92mm FAST intake...i just want the mufflers...would they sound alike with my exhaust i have now..

I would have to look and see if those are 2.5" or 3" catbacks. I can't see the tubing making much difference unless it's 3" tubing.

**pmolina0436** · 09-26-2008, 10:26 AM

Originally Posted by 0rion

I would have to look and see if those are 2.5" or 3" catbacks. I can't see the tubing making much difference unless it's 3" tubing.

ok..but my tubing is 2.5 now..

**0rion** · 09-26-2008, 11:18 AM

Originally Posted by pmolina0436

ok..but my tubing is 2.5 now..

that's what I'm saying. The sound/performance difference between just mufflers and a whole catback would be minimal unless you went to a 3" catback. I know GM likes to crush and kink factory exhaust pipe for fitment where the aftermarket stuff doesn't. There would be a little gain there I'm sure but probably not a ton. The 05-06 got it worse than the 04's did. The 04's got those retarded ass mid pipes that point inward instead of going straight back.

**pmolina0436** · 09-26-2008, 07:59 PM

Originally Posted by 0rion

that's what I'm saying. The sound/performance difference between just mufflers and a whole catback would be minimal unless you went to a 3" catback. I know GM likes to crush and kink factory exhaust pipe for fitment where the aftermarket stuff doesn't. There would be a little gain there I'm sure but probably not a ton. The 05-06 got it worse than the 04's did. The 04's got those retarded ass mid pipes that point inward instead of going straight back.

Oh i see what your saying...i didnt understand at first but i get it...but yea i think im going to go with the mufflers only from spin tech...do you have the model number on those mufflers that were on the video...they sound awsome..