Exhaust pop when shifting
Thread Starter
Pro
Joined: Sep 2010
Posts: 535
Likes: 10
From: Fort Worth TX
Exhaust pop when shifting
During quick shifts from 1-2 or 2-3 sometimes I get a loud crack that comes from the exhaust. Sometimes I can get this to go away if I take my time shifting but I don't want to be the last one in the group on a green light. I don't really mind it but friends have commented that it doesn't sound too good so I just want to make sure it's not bad. I also have a really hard time with getting a smooth 1-2 shift unless I go really really slow, however all the other shifts are fine. User error or possibly mechanical error?
I'm also considering getting my 2008 split spoke wheels powdercoated black. Does anyone have any pictures or verify the process is as easy as I think it is - take all the wheels and tires off of the car and have them painted and then just put them back on? Do i need to get aligned or balanced if I'm just powdercoating?
I also watched a video that said for the C6's the clutch needs to be on the floor for it to fully disengage even though it feels like mine disengages 2-3 inches off the floor, and this was why some shifts are difficult. Is this true?
Thanks.
I'm also considering getting my 2008 split spoke wheels powdercoated black. Does anyone have any pictures or verify the process is as easy as I think it is - take all the wheels and tires off of the car and have them painted and then just put them back on? Do i need to get aligned or balanced if I'm just powdercoating?
I also watched a video that said for the C6's the clutch needs to be on the floor for it to fully disengage even though it feels like mine disengages 2-3 inches off the floor, and this was why some shifts are difficult. Is this true?
Thanks.
Burning Brakes
Joined: Aug 2008
Posts: 802
Likes: 6
From: Oro Valley AZ
During quick shifts from 1-2 or 2-3 sometimes I get a loud crack that comes from the exhaust. Sometimes I can get this to go away if I take my time shifting but I don't want to be the last one in the group on a green light. I don't really mind it but friends have commented that it doesn't sound too good so I just want to make sure it's not bad. I also have a really hard time with getting a smooth 1-2 shift unless I go really really slow, however all the other shifts are fine. User error or possibly mechanical error?
I'm also considering getting my 2008 split spoke wheels powdercoated black. Does anyone have any pictures or verify the process is as easy as I think it is - take all the wheels and tires off of the car and have them painted and then just put them back on? Do i need to get aligned or balanced if I'm just powdercoating?
I also watched a video that said for the C6's the clutch needs to be on the floor for it to fully disengage even though it feels like mine disengages 2-3 inches off the floor, and this was why some shifts are difficult. Is this true?
Thanks.
I'm also considering getting my 2008 split spoke wheels powdercoated black. Does anyone have any pictures or verify the process is as easy as I think it is - take all the wheels and tires off of the car and have them painted and then just put them back on? Do i need to get aligned or balanced if I'm just powdercoating?
I also watched a video that said for the C6's the clutch needs to be on the floor for it to fully disengage even though it feels like mine disengages 2-3 inches off the floor, and this was why some shifts are difficult. Is this true?
Thanks.
Team Owner
Joined: Nov 2006
Posts: 21,136
Likes: 212
From: Long Island New York
powdercoating is a little more complicated than just painting. If you dont know, in a nut shell, the process consists of spraying the wheel with electrically charged powder then baking it in an oven to cure the finish. not something thats a DIY.
I have CCW wheels on mine that I bought that way from CCW. Over 2 years now and still look like the day I got them. I would certainly get the wheels balanced after remounting the tires. You shouldnt need an alignment at all.
I have CCW wheels on mine that I bought that way from CCW. Over 2 years now and still look like the day I got them. I would certainly get the wheels balanced after remounting the tires. You shouldnt need an alignment at all.
Thread Starter
Pro
Joined: Sep 2010
Posts: 535
Likes: 10
From: Fort Worth TX
Exhaust is NPP with the fuse pulled. To my knowledge the car is completely stock as it is from the factory.
And with powdercoating I realize it's not "painting", I've got a quote from a powdercoater and all but I was just curious about whether I needed to balance and align or not after powdercoating.
Thanks
And with powdercoating I realize it's not "painting", I've got a quote from a powdercoater and all but I was just curious about whether I needed to balance and align or not after powdercoating.
Thanks
Thread Starter
Pro
Joined: Sep 2010
Posts: 535
Likes: 10
From: Fort Worth TX
Okay, update. It's got Kooks long tube headers, with the high flow cats and X pipe. It's also been reprogrammed or tuned or whatever by Chuck COW from Corvette's of Westchester.
That probably makes a difference.
That probably makes a difference.
Last edited by corvette-kyle; Feb 19, 2011 at 02:35 PM.
Burning Brakes
Joined: Oct 2010
Posts: 763
Likes: 2
It's a backfire from fuel over-run or condensed fuel re-evaporating and entering the cylinders/exhaust.
It should be a lot more common then just every now and then too.
Cats act as suppressors to this though so maybe that's why only really big ones are getting through.
It should be a lot more common then just every now and then too.
Cats act as suppressors to this though so maybe that's why only really big ones are getting through.
Tech Contributor
Joined: Oct 1999
Posts: 41,058
Likes: 9,820
From: Charlotte, NC (formerly Endicott, NY)
I doubt the popping is an issue. When I ran removed the mufflers and ran straight exhaust pipes on my 97 it would pop just like that and other than the mufflers being removed it was totally stock. Not sure but I think my 08Z will pop a little when I shift at high rpms while on a road course but it is hard to hear over all the wind noise.
Bill
Bill
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Melting Slicks
Joined: Oct 2010
Posts: 2,314
Likes: 4
From: Cape May, NJ; Guntersville, AL; Orange Beach, AL
It's a backfire from fuel over-run or condensed fuel re-evaporating and entering the cylinders/exhaust.
It should be a lot more common then just every now and then too.
Cats act as suppressors to this though so maybe that's why only really big ones are getting through.
It should be a lot more common then just every now and then too.
Cats act as suppressors to this though so maybe that's why only really big ones are getting through.
Normal and should be happening a lot with the headers. I love the gurgle and pop.
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
The PCM has tables for ignition advance and Deceloration Fuel Cut-Off or (DFCO) that can be modified to reduce the exhaust popping. The problem is fuel continues to be injected when you are at elevated RPM and the ignition is retarded after TDC, so raw fuel is going out the exhaust system and getting ignited down the line.
I have headers and Corsa Sport cat-back and there is some burbling but its not obnoxious, so I've have left it alone.
I have headers and Corsa Sport cat-back and there is some burbling but its not obnoxious, so I've have left it alone.
Burning Brakes
Joined: Oct 2010
Posts: 763
Likes: 2
The PCM has tables for ignition advance and Deceloration Fuel Cut-Off or (DFCO) that can be modified to reduce the exhaust popping. The problem is fuel continues to be injected when you are at elevated RPM and the ignition is retarded after TDC, so raw fuel is going out the exhaust system and getting ignited down the line.
I have headers and Corsa Sport cat-back and there is some burbling but its not obnoxious, so I've have left it alone.
I have headers and Corsa Sport cat-back and there is some burbling but its not obnoxious, so I've have left it alone.
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Burning Brakes
Joined: Oct 2010
Posts: 763
Likes: 2
Car's don't normally inject fuel on deceleration though, I don't remember there being an "elevated RPM" disable of this, but I'll check when I get home.
Thread Starter
Pro
Joined: Sep 2010
Posts: 535
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From: Fort Worth TX
I actually read up on the whole changing the clutch fluid thing awhile ago and just got around to it today. Flushing the clutch fluid with Prestone Dot 4 from Walmart ($3) it completely removed the difficult 1-2 shift and also smoothed out everything in general. My clutch fluid was completely black and at the minimum level, and I have been driving all day enjoying the car. It feels brand new.
I've noticed the popping only really occurs between 1-3k rpm, if I downshift to second gear and let off the throttle it will smoothly roll down until around 2.5k rpm then start popping. I like the popping and gurgling, just wanted to make sure it was normal. I am still getting a single loud pop when I shift occasionally, and when this happens it happens when I move the shift ****, not when I re-engage the clutch.
I've noticed the popping only really occurs between 1-3k rpm, if I downshift to second gear and let off the throttle it will smoothly roll down until around 2.5k rpm then start popping. I like the popping and gurgling, just wanted to make sure it was normal. I am still getting a single loud pop when I shift occasionally, and when this happens it happens when I move the shift ****, not when I re-engage the clutch.
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
I actually read up on the whole changing the clutch fluid thing awhile ago and just got around to it today. Flushing the clutch fluid with Prestone Dot 4 from Walmart ($3) it completely removed the difficult 1-2 shift and also smoothed out everything in general. My clutch fluid was completely black and at the minimum level, and I have been driving all day enjoying the car. It feels brand new.
I've noticed the popping only really occurs between 1-3k rpm, if I downshift to second gear and let off the throttle it will smoothly roll down until around 2.5k rpm then start popping. I like the popping and gurgling, just wanted to make sure it was normal. I am still getting a single loud pop when I shift occasionally, and when this happens it happens when I move the shift ****, not when I re-engage the clutch.
I've noticed the popping only really occurs between 1-3k rpm, if I downshift to second gear and let off the throttle it will smoothly roll down until around 2.5k rpm then start popping. I like the popping and gurgling, just wanted to make sure it was normal. I am still getting a single loud pop when I shift occasionally, and when this happens it happens when I move the shift ****, not when I re-engage the clutch.
Burning Brakes
Joined: Oct 2010
Posts: 763
Likes: 2
RPM same thing, it stops at like 1200 rpm because obviously you have to start idling eventually.
TPS is to make certain you are off throttle.
g/cyl same thing in case you had some sort of a failure. of throttle or leak to.
None of these things serve to inject fuel during decel, it's the opposite obviously. I also checked and it is above 6000 rpm for DFCO to shut off and be injecting during decel, I don't know anyone who lets completely off above 6k, and if they do they shouldn't be, it's a bad habit that can snap connecting rods.
In other words if you're decelerating off throttle, no fuel is being injected. So again the pops are from overrun and evaporating fuel.
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Speed is for it to be active above a certain speed, a really low MPH
RPM same thing, it stops at like 1200 rpm because obviously you have to start idling eventually.
TPS is to make certain you are off throttle.
g/cyl same thing in case you had some sort of a failure. of throttle or leak to.
None of these things serve to inject fuel during decel, it's the opposite obviously. I also checked and it is above 6000 rpm for DFCO to shut off and be injecting during decel, I don't know anyone who lets completely off above 6k, and if they do they shouldn't be, it's a bad habit that can snap connecting rods.
In other words if you're decelerating off throttle, no fuel is being injected. So again the pops are from overrun and evaporating fuel.
RPM same thing, it stops at like 1200 rpm because obviously you have to start idling eventually.
TPS is to make certain you are off throttle.
g/cyl same thing in case you had some sort of a failure. of throttle or leak to.
None of these things serve to inject fuel during decel, it's the opposite obviously. I also checked and it is above 6000 rpm for DFCO to shut off and be injecting during decel, I don't know anyone who lets completely off above 6k, and if they do they shouldn't be, it's a bad habit that can snap connecting rods.
In other words if you're decelerating off throttle, no fuel is being injected. So again the pops are from overrun and evaporating fuel.
Former Vendor
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