I just completed a 2 year body off LS conversion on a 65 coupe that I've had for 36 years. On deceleration the backfire in the pipes are so loud it blows your head off. I'm told it's the exhaust gases igniting in the pipes. Has anyone experienced this. The tech at GM Performance told me not to adjust the tune and this wouldn't this. Any suggestions?
C2 side pipes backfire
- Thread starter DOC M
- Start date
I had a Power Commander tuner on one of my Harleys. Trying to get every ounce of power out of what was there. I loaded a tune from their website. I had exactly the problem you are talking about. It was embarrassing pulling up to a stoplight. I called Power Commander and the guy sent me a new tune. I loaded the tune and went for a ride. The popping was gone. So I had to have a look at the new tune. All he did was richen the fuel map a little, from 0-1500 RPM. What that did was richen the exhaust gas to the point where it wouldn't ignite. Too much fuel and not enough air there. And it wasn't a big change in the fuel map. It didn't affect the idle or just off idle. Wasn't puffing black from being a richer mixture, or anything like that. So for my engine, the original fuel map that I download from Power Commander was too lean, obviously. The engine didn't pop with the factory tune, so the modified tune just moved closer to factory in the 0-1500 RPM area. That fact that there is fuel to burn still in the exhaust is another thing. I always thought it all got burnt before the exhaust valve opened.
DOC M ... sorry for not seeing this sooner. On a stock C2 engine/exhaust system it's been the exhaust pipe packing that is allowing some air in between the exhaust manifold and the exhaust pipe. Either tightening those 3 nuts or replacing the packing has solved it for me.
Did you get this rectified? I have had same issue with various LS conversion.Adjusting IAC seems to remedy this issue.
- Thread starter
- #5
No. I took it to Newmarket to a guy who was recommended to me who can remap a GM ECU with a Dyno tune but he couldn't get it to stop. I'm at a loss. I contacted GM Performance and spoke to a tech. he told me not to mess with the ECU as it would void the warranty which has expired now. I'm at a loss of what to do now. Any suggestions that I could try would be great. Thanks
Hi Doc,
I am from the Newmarket area and buddy is pretty good if its who I think you went to. But the best would be Champion Motors in Scarborough. They do a lot of tuning for LS engines. That would be my recommendation. Give them a call and see what they say. I have a 2014 ZL1 Camaro also and from the factory, it pops out of the exhaust because that's the cool thing now
. But on the LS conversions, I have done using FI TECH or equivalent. Usually, you can clean up the popping by having the computer to cut fuel when on decel which then prevents the fuel load up / popping. I would talk to the guys at Champion as they build these setups all the time plus running a GM factory ECU they have lots of experience. They did my buddies C5 with twin turbos and it ran amazingly with like 780 hp or something. Good luck lets us know how it goes! I also have a contact in Kitchener also if that does not work out but seeing your from the Oshawa area I think Champion is much closer.
I am from the Newmarket area and buddy is pretty good if its who I think you went to. But the best would be Champion Motors in Scarborough. They do a lot of tuning for LS engines. That would be my recommendation. Give them a call and see what they say. I have a 2014 ZL1 Camaro also and from the factory, it pops out of the exhaust because that's the cool thing now
. But on the LS conversions, I have done using FI TECH or equivalent. Usually, you can clean up the popping by having the computer to cut fuel when on decel which then prevents the fuel load up / popping. I would talk to the guys at Champion as they build these setups all the time plus running a GM factory ECU they have lots of experience. They did my buddies C5 with twin turbos and it ran amazingly with like 780 hp or something. Good luck lets us know how it goes! I also have a contact in Kitchener also if that does not work out but seeing your from the Oshawa area I think Champion is much closer.
Stock side pipes are 2 1/2 inch and about 1 7/8 at the crimps more powerfull motors cant breath very well. I installed a 2 1/2 inch under-car system from the headers back with a drop down at the rear skirt installed electric cut outs and disconnected the pipes. Left them on the car for appearance. No more exploding gases due to cold air in the side pipes.
Hi All;
I've just finished an ls3 swap into a 63 c2. The LS backfiring is associated with the DFCO settings in the tune. One thing I learned was that the ECU has to getting a valid speed reading from the transmission in order for the DFCO parameters to alter the fuel cut-off characteristics (and hence the backfiring upon decel or throttle lift between shifts).
On an E38 LS3 ECU, it turns out that if the ECU came out of an automatic car ... it will not read the transmission speed on pins 71 & 72 .... it gets speed across the bus from the trans computer (which you probably aren't using in a c2 swap). This can't be altered with tuning sw ...I.e. HPTuners. Uou have to an E38 ecu out of a car that came from the factory with a standard.
Once the ecu sees vehicle speed properly, you can then play with the other dfco parameters in the tune to stub out the backfiring. I reduced mine to a very light bit of burbling. I'm still playing with it to get it to where I want it.
Cheers
Eboch
I've just finished an ls3 swap into a 63 c2. The LS backfiring is associated with the DFCO settings in the tune. One thing I learned was that the ECU has to getting a valid speed reading from the transmission in order for the DFCO parameters to alter the fuel cut-off characteristics (and hence the backfiring upon decel or throttle lift between shifts).
On an E38 LS3 ECU, it turns out that if the ECU came out of an automatic car ... it will not read the transmission speed on pins 71 & 72 .... it gets speed across the bus from the trans computer (which you probably aren't using in a c2 swap). This can't be altered with tuning sw ...I.e. HPTuners. Uou have to an E38 ecu out of a car that came from the factory with a standard.
Once the ecu sees vehicle speed properly, you can then play with the other dfco parameters in the tune to stub out the backfiring. I reduced mine to a very light bit of burbling. I'm still playing with it to get it to where I want it.
Cheers
Eboch
Most of that was a foreign language to me but totally respect the knowledge that many have here on the forum. My last successful attempt of tuning was a 72 340 Duster... Sheesh... shows my age.... lol....
I have seen adjustments on both MSD and FiTec fuel injection systems to eliminate backfire-fuel turn off to a point.
Dave91TM
Power User
I'm with ya Ruff, my tuning skills, more or less, end at bottoming the jet screws then backing them out 1 1/2 turns ala 68 BSA 441.
My standard tune was always 1 1/4 turn. Was my standby on everything from cars to snowmobiles to motorcycles to chain saws and weed eaters.... Worse thing they ever did was invent fixed, non-adjustable jets... lol...
My c2 did this, but it was due to my vacuum advance hose being disconnected. Connected it back on and problem went away.