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OK guys I've been trolling threads and reviewing other tunes and come to the conclusion that it's best I start my own thread with my tune and logs. I'm having an issue with AFR which I believe is a transient issue, most often tipping out of the throttle it goes rich then lean. It's a 2000 Camaro M6, 4.8l, VSR 7875 gen 2, Summit Stage 2 turbo cam. Running Deka 80's with a boost referenced FPR with evap as return line. Dual walbro 255lph pumps triggered on a 4psi hobbs switch. I've been reading information on other people's threads but i was hoping you guys could review the log and give me a better idea of what my issue is so i have a better idea on what i should actually be adjusting within the tune. Currently running OLSD until i get this figured out. See attachments:
No. I've reduced min fuel milligrams to .005 and it helped, but I'm still having issues after the car warms up. It's lean on cruise and decel after startup but becomes rich on decel after running for ~5min. I'm beginning to wonder if it's a voltage issue. On startup I'm getting over 13v but it goes to 12v and even slightly less after it warms up. With replacing the OEM fans with 2x derale fans and replacing the OEM fuel pump with twin 255lph walbros I know the stock system is taxed. I ordered a 145a truck alternator and plan on doing the big 3 to see if that helps. If not I guess I need to molest transient fueling more if I want to fix it. I'm still opened to suggestions/ideas from others so if you have any thoughts, please do share.
There is a ton of discussion about transients but little hard data. I have a 2000 M6 Corvette with a 228/232 111+3 cam, LT's, and GTP 36lb injectors. It is NA. Tuning with HPT and an AEM WB. Spent lots of time in OL getting the VE and MAF dialed in. Currently running CL with LTFT's off - even this took time in proportional fueling tables to get the O2's to switch properly in low airflow regions. All that said my issue is the opposite of yours. Big lean spike on tip out followed by smaller rich spike on tip in. This happens with every gear shift. Not a big deal when just driving around but when at high output I am seeing some KR just after changing gears. I have not yet found any transient data that provides a definitive answer. Might try to experiment with Fuel to Wall Impact factor - increase fuel at low KPa cells with the hope of reducing the lean spike.
Did manage to solve one problem though. Was rich on decel and injectors would not go below 1.7ms. Reduced the injector min pulse width and default pulse width by about 30% (from 1.277 ms to 0.9 ms) and the rich decel is improved as injectors are now going to 1.5ms. Might try going to 0.8ms to see if it gets better yet again.
I didn't look at your tune files but assume you have already tried the above?
Yeah tell me about it. I'm OLSD and logging every time I drive the car trying to adjust and dial in VE. I've noticed KR on gear change on high boost setting (14-16# depending on weather) and just pulled 2* of timing from the last row @ 5200 & 5600 RPM which is probably where max torque is on my setup. Haven't seen it again yet but it was an intermittent issue for me. I just bought aeroforce gauges which have an annunciator that can be used to indicate knock so I'd be comfortable driving the car around without logging lol.
I have not messed with min pulse width and default pulse width since I've input the data others use with DEKA 80's but will be giving this a shot after I get that alternator installed this weekend. Looks like i'm going to have to remove the turbo & hot side from under the car to get to it :/. Thanks for sharing.
If you have deka 80's input this data....I have deka 80's and took some time to get it right...
go fuel>general>limits
-Min injector pulse set to .213 at the 0 rpm and then .304 the rest of the cells
-Default injector pulse .395 from 0rpm to 4000 and .502 4400rpm and up
Injection timing:
-Boundry 6.50
-Normal 2.90 from -40 to 68f. 90=3.90 then 111f and 133f=4.90 and 154F and up is 5.90
-Makeup is 5.55 across the board
I never mess with transient fuel....that can be fixed with the ve. Do a scan and play it back and see what cells need more fuel under transitions. Using Real Time tuning helps this process greatly. Turn long term fuel trims off.
Yeah tell me about it. I'm OLSD and logging every time I drive the car trying to adjust and dial in VE. I've noticed KR on gear change on high boost setting (14-16# depending on weather) and just pulled 2* of timing from the last row @ 5200 & 5600 RPM which is probably where max torque is on my setup. Haven't seen it again yet but it was an intermittent issue for me. I just bought aeroforce gauges which have an annunciator that can be used to indicate knock so I'd be comfortable driving the car around without logging lol.
I have not messed with min pulse width and default pulse width since I've input the data others use with DEKA 80's but will be giving this a shot after I get that alternator installed this weekend. Looks like i'm going to have to remove the turbo & hot side from under the car to get to it :/. Thanks for sharing.
Make sure its a brand new delco alternator or you'll be changing it again soon. Also, do what you can to shield the alternator from the heat of the exhaust.
I appreciate it. I bought a new delco unit from Rock Auto. It does, however, have a "made in china" sticker on it. The hot side is wrapped which I'm hoping helps out with heat.
If you have deka 80's input this data....I have deka 80's and took some time to get it right...
go fuel>general>limits
-Min injector pulse set to .213 at the 0 rpm and then .304 the rest of the cells
-Default injector pulse .395 from 0rpm to 4000 and .502 4400rpm and up
Injection timing:
-Boundry 6.50
-Normal 2.90 from -40 to 68f. 90=3.90 then 111f and 133f=4.90 and 154F and up is 5.90
-Makeup is 5.55 across the board
I never mess with transient fuel....that can be fixed with the ve. Do a scan and play it back and see what cells need more fuel under transitions. Using Real Time tuning helps this process greatly. Turn long term fuel trims off.
I appreciate this! Going to make these changes and take a ride tomorrow. Will report back.
Go to Engine Diagnostics---DTC's and make P0101,102,103 to MIL on First error and THEN you will be in SD. That's going to screw up your adjustments. You can leave the boxes checked if you don't mind seeing the error light. Otherwise, uncheck them. Your VE table is somewhat choppy, but not too bad.
I looked at your cruise scan and I can't find a lot wrong. After you make the change above, you will have to retune the ve table. I see several spots that you mention that go lean and rich, but you can fine tune it with individual cells in the ve, but it is not very far off and you are going to have "left overs" when you gas it or release the pedal. Looks like it always goes back to close to your commanded. Smooth out the ve table, that will help. The smoother the table, the smoother your engine runs. I don't mean a flat ve table---just to make sure.
You might ought to double wrap the pipe near the alternator. Maybe even make a heat reflecting shield.
Going to work on this. The stock lines i cut and rerouted are now rubbing after installing the larger 145a alternator so i ordered longer stainless braided lines to reroute them. With those lines out of the way now i should have room for a shield or another wrap.
Go to Engine Diagnostics---DTC's and make P0101,102,103 to MIL on First error and THEN you will be in SD. That's going to screw up your adjustments. You can leave the boxes checked if you don't mind seeing the error light. Otherwise, uncheck them. Your VE table is somewhat choppy, but not too bad.
Damn, thanks for pointing this out. Does it not go into SD on second error as i had it or does it just take longer to get into SD? Could this be why I was lean on startup for the first ~5min of driving after startup?
Originally Posted by dw456post
I looked at your cruise scan and I can't find a lot wrong. After you make the change above, you will have to retune the ve table. I see several spots that you mention that go lean and rich, but you can fine tune it with individual cells in the ve, but it is not very far off and you are going to have "left overs" when you gas it or release the pedal. Looks like it always goes back to close to your commanded. Smooth out the ve table, that will help. The smoother the table, the smoother your engine runs. I don't mean a flat ve table---just to make sure.
I appreciate you looking at the log and providing feedback. I'm hopeful the changes you guys have suggested will help out with a smoother VE table.
I was able to take a few logs after injector pulse limits, corrections, and timing settings recommended by @Kfxguy and was pleased to see lower MAP are of the VE to be lean and not rich. With some work it looks like there's hope in controlling the erratic, rich condition i was having in this area of the VE.
My time constraint for additional logging is the PS lines I ordered Friday. After install of a larger alternator, there just isn't enough space between the alternator and the hot side where my stock bent/rerouted lines were routed. It wasn't an ideal spot for those lines anyway lol. I'm hoping they come in later this week so I can install them and log/tune VE this weekend.
Oddly enough I worked an issue exactly like this last month on almost the exact same setup. Also had Deka 80s....but which variant of them, I have no idea. The data suggested they definitely flowed far more than they indicated at <2ms pulse widths. That issue is just textbook poor characterization data for the injector - why exactly though, I'm not sure. I read briefly that there are different variants of the Deka 80 which have different data sets. Also not totally convinced they weren't worn out...unless you bought yours new, they could be 20 year old injectors that have been passed around from build to build.
A huge help for that issue was decreasing fuel pressure and changing the injector data to reflect the new flow rate. Going from 4 bar to 3 bar was probably an 80% solution... Had the guy swap over to E85 and that fixed the rest of the issue
Oddly enough I worked an issue exactly like this last month on almost the exact same setup. Also had Deka 80s....but which variant of them, I have no idea. The data suggested they definitely flowed far more than they indicated at <2ms pulse widths. That issue is just textbook poor characterization data for the injector - why exactly though, I'm not sure. I read briefly that there are different variants of the Deka 80 which have different data sets. Also not totally convinced they weren't worn out...unless you bought yours new, they could be 20 year old injectors that have been passed around from build to build.
A huge help for that issue was decreasing fuel pressure and changing the injector data to reflect the new flow rate. Going from 4 bar to 3 bar was probably an 80% solution... Had the guy swap over to E85 and that fixed the rest of the issue
If E85 was readily available in New Orleans, LA, I would have converted when I went turbo in 2020. If it would have fixed the issue it would have been an ancillary benefit lol. I bought the injectors new.
Got the PS lines on and did a bit more logging. AFR is much more controllable on decel in the lower KPA areas of the VE table. I still don't have enough time with logging and VE adjustment to have it dialed in but results with injector pulse posted by @Kfxguy in post #6 are promising and i appreciate him sharing.
I'm also seeing some inconsistencies in commanded AFR to become noticeably leaner after some run time @ operating temp so i'm starting to give some love to the IAT / ECT bias table in the tune. The inconsistencies are of course in the areas of the VE that see lower dynamic airflow. I'm currently tilting bias to ECT in the lower dynamic airflow areas of this table and hoping the adjustment helps account for heat soak in the idle/cruise (low load) area of the VE but will consider relocating my IAT in the manifold if the issue persists. IAT is currently located in the charge pipe 12-18" before the TB which is above where my turbo is with the Huron Speed V3 AC kit. If you have thoughts to share, please do.
-Beau
Just as an FYI, you can't always expect the engine to burn the fuel and air properly...particularly with a larger camshaft. This is actually why DFCO exists - not to save fuel, but to prevent the emissions that come along with poor combustion in very low load decel regions. As such, you should be ignoring high vacuum fueling feedback. This even applies to bone stock engines.
Just as an FYI, you can't always expect the engine to burn the fuel and air properly...particularly with a larger camshaft. This is actually why DFCO exists - not to save fuel, but to prevent the emissions that come along with poor combustion in very low load decel regions. As such, you should be ignoring high vacuum fueling feedback. This even applies to bone stock engines.
I appreciate the feedback. Is a lean condition in low KPA area of the VE as harmless as rich condition?
Lower KPA AFR error has come a long way. Only took 3mo and some help from you guys lol.
It is harmless in terms of engine health. The only thing it does it cause excess emissions. That entire bright green 'arc' in the first pic there...don't make any changes for those errors. They are not real. You're better off keeping DFCO enabled so it stays out of closed loop and doesn't populate those areas with trim values.
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Help w/ transient fueling. chasing commanded AFR 
