Supercharged LS2 surge on light throttle and coast.

[Wilburbill]

07 Corvette M6, Long tubes, no cats, X pipe with Ecs Supercharger. I have a surge on light throttle and coast. With the help of the guys over on the Corvette forum I have switched to a SD tune, changed the base running airflow, Changed the closed loop proportional settings and have been working on the vve table. It did surge at idle but now its rock steady. In the attached log in the first couple of minutes when coasting down the spark timing drops to 3.5*. That is below the idle timing of 15*. is there something that is controlling that? Should it not do that? I have also included the tune. Thanks

[5FDP]

To help you out some, you'll want to make a few changes to your tune.

Change the low fail on the MAF to a lower number than the high fail so it's for sure failed. You won't want to log anything MAF related if this is completely speed density. It could skew your data.

Which MAP are you using. Most of the 2 bar maps have an offset of 10.33 instead of 8.00.

Also you don't want to max out the injector flow rate table at 63.5 like that. Do the double stoich/half the IFR/half the IVT terms to bring everything back in line.

I'd also disable the burst knock, so it doesn't pull timing and power at random.

[GHuggins]

You can see it surging in the log via airflow going up and down only - no actual rpm surge per say, but I bet you can hear it right? The surging is rather consistent with the O2 swings - try multiplying your proportional airflow table by 1.6 and see if anything changes - trying to tighten up your air fuel swings here...
Your min air also could use knocking down from 1000 rpms to 2500 rpms - interpolate from 800 to 2500
The timing dip is most likely coming from the light throttle from your tq model going into engine hold back or decel tq "mode" if you will - the min air may help with this

You also need to fix the fueling as stated above - Might help to state the full build such as injectors and regulator setup

[Wilburbill]

The injector data was installed by ECS. I sent them my ecm and they installed a base tune. I am using a Cobalt map sensor. YES I can hear the surge in the exhaust tone. Thanks for the help. I will make the changes and report back.

[GHuggins]

Map should be 200 and 10.33 then - what's your baro reading with key on engine off - should be the same as your altitude.

[Wilburbill]

What is the best way to disable burst knock?

[Wilburbill]

Ok I will change the map settings.

[Wilburbill]

The map I used was an AC Delco 12615136.

[Wilburbill]

The injectors are Bosch 60lb/650CC they were the injector supplied with the ECS kit. I am using a boost a pump which was also included in the ECS kit. I sent the ecm to Doug at ECS and he put the injector data in. I'm not saying it right just saying what was done.

[schpenxel]

To disable burst KR just set any of those tables to 0 and it will disable it

Yeah, for better or worse the data ECS gave you is totally wrong. Not saying you can't make it work well enough (and I don't have the right data) but "technically" you could say it is wrong

[Wilburbill]

Figures, I guess it was a waste to send the ecm in. I have had to change everything. So what's the deal do the injectors need scaled? Maybe I should get everything changet that's been recommended and see how it does first? Couldn't work on it tonight but plan to tomorrow night.

[Wilburbill]

Ok, I disabled BK. I multiplied the proportional airflow table by 1.6 I still get surge on light throttle and coast. I can't really say its any better. I did not change the map settings as I'm confused because when I do a search for that sensor everything I find says 200/8. I checked the map reading with the engine off and I get 98kpa. If everyone still thinks I need to change the setting I will. I did not change the min air yet. I had it at the stock settings and it wanted to drop too low and almost die before settling at idle. The car still surged at the stock min air flow settings. I have attached 2 logs one with it surging at light throttle and the tune. Thanks

[GHuggins]

I'll have to double check that map setting, but I thought for sure the cobalt sensor was 200 and 10.33 / What cobalt is it out of - easy enough to compare to a stock file and make sure...

What sucks is that you don't have integrator delay - makes O2 tuning a lot harder, even more so when the injector data is wrong / Your short pw's control and cause a lot of your surging - increasing proportional should have helped to control the swings, but it didn't - what happens if you go the other way - stock x.75 for instance?

[Wilburbill]

I will try it.

[Wilburbill]

Ok, tried .75, it still surges. Might have helped just slightly. I dropped the closed loop proportional limit settings down some more . The stock settings were 2.000 and I had dropped them down to o.001 on 8 and 1.250 on the others today I dropped them to0.001 on the 8,0.500 0n the 16 and 1.000 on the others. That might have helped slightly more but still to me it's just not right. I have a 68 Chevelle ss with a 468 big block, aluminum heads and a big roller cam. I think it's smoother than the vette. I didn't put a cam in the vette because I was in hopes of having a smooth running car until I got in the throttle. Watching the o2 sensor swings they still go from one extreme to the other. Most stock engines don't do that. So what's causing that? Is it the injectors Or wrong injector data installed? If so what do I need to do to correct it? Or is it going to surge no matter what I do? I don't mind spending money on my stuff to make it right but don't want to waste money either.

[GHuggins]

13.9 to 15.8 afr swings is horrible - your looking to tighten these up to a .5 swing - yours are a point and a half right now which is why your surging...

Change your min/rich settings to 450 - still won't help the swings much, but needs to be done... Dropping the limit, dropping proportional, dropping your min air in the cruising area rpms will all help, BUT - the more you lower your proportional or limit settings - the more loss on fuel control you'll have and you may find yourself cruising down the highway only to glance at the wideband and find yourself running in the 15's / proportional controls switching and the aggressiveness of the switching speed / limit helps to control how much fuel it adds or takes away to induce the switch which is why lowering limit narrows the switch window - from my findings it doesn't like being below 1.25 on the OS's where it's populated...

Right now - as previously stated - you have a few things working against you - no integrator delay (without this you need to physically relocate the O2's closer to where they originally were in relation to air speed in the exhaust - faster moving exhaust - needs to be further downstream - slower due to bigger diameter pipes - closer to the head) / Injectors without correct data - incorrect control of your min pulsewidths - these are what control your O2's switching

I would just take it out and play with the proportional settings - you'll need to keep dialing it back to make it more lazy it looks like / you really don't even need to drive it if you can get it to do it free revving in the right rpm and airflow zone...

[Wilburbill]

Looks like there is really no data available for these injectors other than buying the Branish CD? If that's the case should I buy a set of ID850 injectors or will they be too big? Kind of sucks that ECS sells injectors with io data.

[Wilburbill]

I changed min/rich to 450, dropped the min air and took a few degrees of timing out where it was surging. o2 sensors are still all over the place but quite a bit of the surge is gone. Not sure what to do next to try to improve from here? I added a little fuel to pe because last time I got on the throttle hard wide band showed lean. I tried it again tonight and it still shows lean. its better but I'm not sure what to do to improve it. Should I lower the pe delay rpm ? The log is kind long the part when I was on the throttle is at the end. I have also attached the tune.

[5FDP]

Don't keep adding to PE to get the AFR richer. The PE EQ ratio should be a set it once and leave it type of thing. If your commanded doesn't match the actual you'll need to add fuel via the MAF or VVE to get it to line up with commanded. Like if you where calling for 11.2 but saw 12.0, you'd want to add in fuel to get it closer. If you added 3-5% to the curve and it went down to 11.6, then you know you are on the right track and need to add a little more.

[GHuggins]

Change max rich to 450 too and tell you what - go ahead and change all of the limits to .010 and put the airflow mode DOD row in the normal row if it's not - honestly didn't look at that..
-