Sudden severe lean condition at all rpm. SD OL Tune
08-22-2015, 09:03 AM
#1
Racer
Thread Starter
Sudden severe lean condition at all rpm. SD OL Tune
Hi guys,I posted this on LS1 Tech yesterday but decided to post here also since the C5's seem to have some querks the other LS cars don't have. I really doubt the issue I am having is PCM or tune related but because the car is ran in open loop\speed density I thought this may be the best place to ask for help.
Setup includes:
347ci ls1
TFS 225 heads 62cc
Fast 102\NW 102
TSP Torquer2 cam 232\234 112lsa
FIC 42# resized ls1 injectors
newer corvette style returnless fuel system
all the other bolt ons that go along with such a setup
manual trans car
The car is a 97 Corvette with the original 97 PCM, with the 2 bar SD OS, but ran with a 1 bar sensor. I converted over to the SD OS a few months ago and began to retune the car from scratch, after getting the VE finished and starting on dialing in the idle\TF\TC table the car suddenly became very lean out of the blue. I assumed the fuel original fuel pump had fail and without doing any real investigation into the issue, i replaced the pump with a Lingenfelter\Walbro 255 unit. This seemed to solve my issue. But ever since then I have been constantly working with the TF\TC table attempting to get the car to return to idle properly. Last weekend I added a good bit of air to the TC table and the car really seemed to like it, I made small adjustments from there as it kept making the car run return to idle better. But all together the car ran great. I got into the car Monday to run errands in to and the car would barley run. I thought it may have been because it hadn't warmed up and it can be finiky until it does so. On the way to town I noticed it was running very lean, although running well enough to drive around, but did sputter and skip when leaving stops. I doubt any of that is relevant but I mentioned it in the off chance the TC\TF table may somehow effect the VE.
The car currently runs 4-5 afr points leaner (16.5:1-18:1) than it did before at cruising and in slight acceleration conditions. It reads 20:1-23:1 at idle. I don't think the wideband is completely accurate at idle but I don't think it is off at higher engine speeds. It was recently re-calibrated and didn't begin reading so lean until the engine began running poorly. Also the engine does not seem to have a miss or skip. I also don't see any signs of it being an overly rich condition that would cause the wideband to read lean.
So far I have checked the following:
Fuel pressure- holds 70 psi without issue, I thought 70 psi was a little high but after talking with people with the same pump it seems to be average.
I checked for injector signal with noid lights, all was good.
Pulled all the plugs, all the plugs looks good and where all consistent with each other.
Checked all coils and wires, all seemed good.
All sensors seem to be operating properly via the VCM scanner (map, tps, iat, ect)
I pulled the intake and checked for vacuum leaks with no luck. I even tried a new Map sensor for the hell of it.
I also cleaned the four chassis grounds in the engine bay and the one by the fuel pump with no change.
For what it's worth, It isn't throwing isn't abnormal codes.
I've also attached a few scans of the issue to see if anyone can see something I may have overlooked. I anyone needs a scan with different PID's let me know and I will get it done. I will also attach the tune.
Thanks for any help
-Clay
Setup includes:
347ci ls1
TFS 225 heads 62cc
Fast 102\NW 102
TSP Torquer2 cam 232\234 112lsa
FIC 42# resized ls1 injectors
newer corvette style returnless fuel system
all the other bolt ons that go along with such a setup
manual trans car
The car is a 97 Corvette with the original 97 PCM, with the 2 bar SD OS, but ran with a 1 bar sensor. I converted over to the SD OS a few months ago and began to retune the car from scratch, after getting the VE finished and starting on dialing in the idle\TF\TC table the car suddenly became very lean out of the blue. I assumed the fuel original fuel pump had fail and without doing any real investigation into the issue, i replaced the pump with a Lingenfelter\Walbro 255 unit. This seemed to solve my issue. But ever since then I have been constantly working with the TF\TC table attempting to get the car to return to idle properly. Last weekend I added a good bit of air to the TC table and the car really seemed to like it, I made small adjustments from there as it kept making the car run return to idle better. But all together the car ran great. I got into the car Monday to run errands in to and the car would barley run. I thought it may have been because it hadn't warmed up and it can be finiky until it does so. On the way to town I noticed it was running very lean, although running well enough to drive around, but did sputter and skip when leaving stops. I doubt any of that is relevant but I mentioned it in the off chance the TC\TF table may somehow effect the VE.
The car currently runs 4-5 afr points leaner (16.5:1-18:1) than it did before at cruising and in slight acceleration conditions. It reads 20:1-23:1 at idle. I don't think the wideband is completely accurate at idle but I don't think it is off at higher engine speeds. It was recently re-calibrated and didn't begin reading so lean until the engine began running poorly. Also the engine does not seem to have a miss or skip. I also don't see any signs of it being an overly rich condition that would cause the wideband to read lean.
So far I have checked the following:
Fuel pressure- holds 70 psi without issue, I thought 70 psi was a little high but after talking with people with the same pump it seems to be average.
I checked for injector signal with noid lights, all was good.
Pulled all the plugs, all the plugs looks good and where all consistent with each other.
Checked all coils and wires, all seemed good.
All sensors seem to be operating properly via the VCM scanner (map, tps, iat, ect)
I pulled the intake and checked for vacuum leaks with no luck. I even tried a new Map sensor for the hell of it.
I also cleaned the four chassis grounds in the engine bay and the one by the fuel pump with no change.
For what it's worth, It isn't throwing isn't abnormal codes.
I've also attached a few scans of the issue to see if anyone can see something I may have overlooked. I anyone needs a scan with different PID's let me know and I will get it done. I will also attach the tune.
Thanks for any help
-Clay
08-22-2015, 05:34 PM
#2
Racer
Thread Starter
Today I swapped the coil packs and fuel filter just to rule those items out which had no effect on the car.
I then uploaded a tune with the OLFA table set to 1.5 (was 1.0 before hand) in the 176-212 zone, this should have commanded an AFR of 9.8. Once the engine reached operating temp the AFR fell to around 13.5 at idle and all the issues the car had been having cleared up (sputtering on accel, stalling with big throttle increases, ect) and the car revved freely and quickly.
I think that rules out a possible ignition, mechanical, or fuel system part failure, but maybe not a failure with the injector itself (think pulsewidth issues).
But I am still pretty baffled by the issue and don't know where to look next.
I then uploaded a tune with the OLFA table set to 1.5 (was 1.0 before hand) in the 176-212 zone, this should have commanded an AFR of 9.8. Once the engine reached operating temp the AFR fell to around 13.5 at idle and all the issues the car had been having cleared up (sputtering on accel, stalling with big throttle increases, ect) and the car revved freely and quickly.
I think that rules out a possible ignition, mechanical, or fuel system part failure, but maybe not a failure with the injector itself (think pulsewidth issues).
But I am still pretty baffled by the issue and don't know where to look next.
08-23-2015, 09:48 PM
#3
Le Mans Master
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St. Jude Donor '13-'14-'15
Welll to me I am curious why you choose to run an OLSD tune in the 1st place----Even a STOCK 97 ECM open/closed loop tune Using a MAF has the capability of approx. 500-525 crank HP----I have tuned boosted 97-98's with low boost and was able to use the stock tune and MAF
The way to tell if you need to use a SD or OL tune is to 1st see if you run out of MAF table using the stock set-up----My guess you are not----My 98 was very similar to yours about 475 crank HP and I still used the stock tune and MAF---It was close to the end of the MAF table but NOT over----Not only that I still was able to use the STOCK 28# injectors which makes drivability and P/T driving so much better
If you are so committed to use those large injectors and the OLSD tune It seems like your injector flow rates at P/T are far to large---A smaller number makes the fuel richer--not leaner-----I would slope the P/T injectors table by subtracting 10% at 1st to see if your P/T AFR's get richer--they should
There is NO added performance benefit in large injectors unless you need them---
My 28 lb ones did exceed the industry standard of a max duty cycle of 80% they were in the low 90's But it didn't matter as My use of the car was a D/D and occasional drag car---I simply let the injectors cool off between rounds when racing and never had an issue---
The way to tell if you need to use a SD or OL tune is to 1st see if you run out of MAF table using the stock set-up----My guess you are not----My 98 was very similar to yours about 475 crank HP and I still used the stock tune and MAF---It was close to the end of the MAF table but NOT over----Not only that I still was able to use the STOCK 28# injectors which makes drivability and P/T driving so much better
If you are so committed to use those large injectors and the OLSD tune It seems like your injector flow rates at P/T are far to large---A smaller number makes the fuel richer--not leaner-----I would slope the P/T injectors table by subtracting 10% at 1st to see if your P/T AFR's get richer--they should
There is NO added performance benefit in large injectors unless you need them---
My 28 lb ones did exceed the industry standard of a max duty cycle of 80% they were in the low 90's But it didn't matter as My use of the car was a D/D and occasional drag car---I simply let the injectors cool off between rounds when racing and never had an issue---
08-24-2015, 06:33 AM
#4
Racer
Thread Starter
Welll to me I am curious why you choose to run an OLSD tune in the 1st place----Even a STOCK 97 ECM open/closed loop tune Using a MAF has the capability of approx. 500-525 crank HP----I have tuned boosted 97-98's with low boost and was able to use the stock tune and MAF
The way to tell if you need to use a SD or OL tune is to 1st see if you run out of MAF table using the stock set-up----My guess you are not----My 98 was very similar to yours about 475 crank HP and I still used the stock tune and MAF---It was close to the end of the MAF table but NOT over----Not only that I still was able to use the STOCK 28# injectors which makes drivability and P/T driving so much better
If you are so committed to use those large injectors and the OLSD tune It seems like your injector flow rates at P/T are far to large---A smaller number makes the fuel richer--not leaner-----I would slope the P/T injectors table by subtracting 10% at 1st to see if your P/T AFR's get richer--they should
There is NO added performance benefit in large injectors unless you need them---
My 28 lb ones did exceed the industry standard of a max duty cycle of 80% they were in the low 90's But it didn't matter as My use of the car was a D/D and occasional drag car---I simply let the injectors cool off between rounds when racing and never had an issue---
The way to tell if you need to use a SD or OL tune is to 1st see if you run out of MAF table using the stock set-up----My guess you are not----My 98 was very similar to yours about 475 crank HP and I still used the stock tune and MAF---It was close to the end of the MAF table but NOT over----Not only that I still was able to use the STOCK 28# injectors which makes drivability and P/T driving so much better
If you are so committed to use those large injectors and the OLSD tune It seems like your injector flow rates at P/T are far to large---A smaller number makes the fuel richer--not leaner-----I would slope the P/T injectors table by subtracting 10% at 1st to see if your P/T AFR's get richer--they should
There is NO added performance benefit in large injectors unless you need them---
My 28 lb ones did exceed the industry standard of a max duty cycle of 80% they were in the low 90's But it didn't matter as My use of the car was a D/D and occasional drag car---I simply let the injectors cool off between rounds when racing and never had an issue---
Well long story short, Way back in high school I started racing Honda's and built my first turbo car. The tuning options weren't that great back then and I was still very new to tuning. Those cars were SD from the factory and CL tuning wasn't very precise. Anyways, I moved on from there to racing turbo Nissan's using megasquirt, which didn't support MAF at the time. Next I scooped up this Corvette and it was in very poor condition, the car was plagued with several electrical issues and an engine that was on its last leg. I parked the car while I built an engine for it. Once together I started to tune, I planned on tuning SD from the get go just because it's what I am us to using. But I had several issues with the O2 wiring in the car and in stead of fixing the issue I got pissed, removed the sensors and ran it in OL. For the past two years it was worked pretty good. In South Ga we dont have severe climate change throughout the year so I rarely have to tweek the tune.
The first engine I built (dart heads, ls6 intake, same cam) for the car I did run the stock 28# injectors, which were over 90% duty cycle at WOT. Back in January, I switched over to Trickflow 225's and a fast 102\102, so I also went with the larger injectors. I retuned in February and havn't had many issues other than some surging here or there until recently. So I use SD because it is what I am more comfortable with, more so than the MAF being maxed.
Last night, I played around with the IFR table, scaling it for the 70PSI of fuel pressure I now know the car has. As expected, the car went very lean, but I had to put ridiculously high numbers in the VE to even make the car driveable (think 140's in the VE).
The IFR the car is tunes on is what was supplied to me by FIC, although it may or may not be 100% accurate, it did work well, and when the VE was tuned it had reasonable numbers in it, which I somewhat use as a sanity check to know other parameters are inline.
What has me so baffled is the car has ran without issue since around Feb. and now it has all of the sudden went to hell. It makes me feel like it isn't tune related but at the same time, If I up the OLFA table to something much richer, or even richen to tune by using the AFR controls in the scanner, the issues go away. Which leads me to believe the issue isn't mechanically\hardware related.
I wrote this very early in the morning, so I hope it all makes sense.
08-25-2015, 12:00 AM
#5
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St. Jude Donor '13-'14-'15
Yes makes sense------On heavily modded cars when the actual engines VE is increased you often have to "trick" your ECM in order to achieve your goal in AFR----As an example on my 98 when cold and in open loop I had to command an AFR of 16.10 in order to get my goal of a 14.68 AFR----Not a big deal as long as you know this going in and you can verify the actual AFR with a wideband
I would still try to scale your IFR table in the lower MAP areas in P/T and NOT the entire table---and then verify if you are making any headway in richening the P/T fuel
As I mentioned a smaller IFR # makes it richer--If I remember correctly the IFR table is backwards meaning WOT is on top of the IFR table and idle on the bottom
I would still try to scale your IFR table in the lower MAP areas in P/T and NOT the entire table---and then verify if you are making any headway in richening the P/T fuel
As I mentioned a smaller IFR # makes it richer--If I remember correctly the IFR table is backwards meaning WOT is on top of the IFR table and idle on the bottom
08-25-2015, 08:13 AM
#6
Racer
Thread Starter
I do think the IFR table is skewed in the tune somewhat, always has been. But what has me hung up is the fact that the car ran very well with this tune in it for several months with no changes to it other than small tweaks to the throttle cracker table.
I installed a second wideband last night, first I installed it on the same bank as the current WB just to check that my WB was reading correctly. THen I moved it to the opposite bank. Both WB's read consistently with each other each time, which to me rules out any type of single cylinder issue such as an injector\plug\coil\ect.
A guy on LS1Tech brought up the fact that even though my fuel pressure is 70psi, there is a chance it could have been higher and recently dropped. I never checked the pressure when I installed the new pump, so I haven't ruled that out.
I installed a second wideband last night, first I installed it on the same bank as the current WB just to check that my WB was reading correctly. THen I moved it to the opposite bank. Both WB's read consistently with each other each time, which to me rules out any type of single cylinder issue such as an injector\plug\coil\ect.
A guy on LS1Tech brought up the fact that even though my fuel pressure is 70psi, there is a chance it could have been higher and recently dropped. I never checked the pressure when I installed the new pump, so I haven't ruled that out.
08-26-2015, 05:13 PM
#7
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St. Jude Donor '13-'14-'15
Was thinking about this yesterday and thought of one issue I have seen with heavily modded cars as yours---- I have had to turn the DFCO OFF on several cars especially cammed and those with a stall converter----It's called the "deceleration fuel cut off "--
This spikes the fuel very lean like 22-16-1 AFR when lifting off the throttle mostly to save fuel---problem is that DFCO is triggered by a vacuum signal as well as MPH--A cam and a stall can false trigger DFCO because the idle and low throttle vacuum is changed so much --Try turning DFCO OFF just to see if it helps---
This spikes the fuel very lean like 22-16-1 AFR when lifting off the throttle mostly to save fuel---problem is that DFCO is triggered by a vacuum signal as well as MPH--A cam and a stall can false trigger DFCO because the idle and low throttle vacuum is changed so much --Try turning DFCO OFF just to see if it helps---
08-26-2015, 06:58 PM
#8
Racer
Thread Starter
Was thinking about this yesterday and thought of one issue I have seen with heavily modded cars as yours---- I have had to turn the DFCO OFF on several cars especially cammed and those with a stall converter----It's called the "deceleration fuel cut off "--
This spikes the fuel very lean like 22-16-1 AFR when lifting off the throttle mostly to save fuel---problem is that DFCO is triggered by a vacuum signal as well as MPH--A cam and a stall can false trigger DFCO because the idle and low throttle vacuum is changed so much --Try turning DFCO OFF just to see if it helps---
This spikes the fuel very lean like 22-16-1 AFR when lifting off the throttle mostly to save fuel---problem is that DFCO is triggered by a vacuum signal as well as MPH--A cam and a stall can false trigger DFCO because the idle and low throttle vacuum is changed so much --Try turning DFCO OFF just to see if it helps---
06-22-2020, 08:24 AM
#9
1st Gear
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Today I swapped the coil packs and fuel filter just to rule those items out which had no effect on the car.
I then uploaded a tune with the OLFA table set to 1.5 (was 1.0 before hand) in the 176-212 zone, this should have commanded an AFR of 9.8. Once the engine reached operating temp the AFR fell to around 13.5 at idle and all the issues the car had been having cleared up (sputtering on accel, stalling with big throttle increases, ect) and the car revved freely and quickly.
I think that rules out a possible ignition, mechanical, or fuel system part failure, but maybe not a failure with the injector itself (think pulsewidth issues).
But I am still pretty baffled by the issue and don't know where to look next.
I then uploaded a tune with the OLFA table set to 1.5 (was 1.0 before hand) in the 176-212 zone, this should have commanded an AFR of 9.8. Once the engine reached operating temp the AFR fell to around 13.5 at idle and all the issues the car had been having cleared up (sputtering on accel, stalling with big throttle increases, ect) and the car revved freely and quickly.
I think that rules out a possible ignition, mechanical, or fuel system part failure, but maybe not a failure with the injector itself (think pulsewidth issues).
But I am still pretty baffled by the issue and don't know where to look next.
06-22-2020, 05:52 PM
#10
Burning Brakes
OP, I went thru same problems recently when trying to tune with SD OL. I also had 42# injectors from Fuel Injector Connection. I gave up on SD OL, just made it driveable enough so if my MAF fails, SD will take over and I can drive home without major issues. I come also from Megasquirt SD tuning mindset, but I'll tell you MAF tuning is the easiest thing to get dialed in quick, if you have a wideband and if you have it datalogging directly to HP tuners. I recommend Goat Rope Garage tutorials on Youtube for tuning MAF on Gen 3 GM. You can get the MAF dialed in 95% good thru the RPM range with a couple of flashes and test drives.