Running 10psi on 5.3, running really well, but goes lean when I let off. Need Advice

[chiropaul]

My 2001 5.3 s475 is running very well in my 67 Tempest, I've been working on the tune and I have ironed out most the bugs. To me it feels like it is running like a beast right now. Very happy with it. But I noticed on my logs that after I go WOT and then let off the throttle my A/F goes LEAN. I watch my AEM wideband like a hawk and stays in the happy zone when I'm really getting at it. Why would it lean out after a WOT run?? Is this just the sensor lagging?? I would think it would be rich after I have been in the boost.

I would appreciate any advice, suggestions.

[will15]

I am guessing your are doing a SD tune here, you I can't see a wideband in your scan and your commanded AFR at WOT is 14.7 I would sort this out before you do some damage.

[Cyrperformance]

You have no enrichment set for PE or BE, all 1 across. Your VE table is a looks a bit jumpy, look at it in the graph view it should be a nice smooth ramp. Setup your enrichment tables to the screen shots. I have had a lot of help getting to where I am at with my tune and these are the tables that were suggested, as mine were putting me around 11.8, and these will get down around 11.4-5. Hope it helps. Also your config needs to be setup to where you are only recording what you need to. As stated above your not recording WB and there is an unsupported parameter that can be deleted, the more accurate your logs are the better your tune will become.

[5FDP]

Ever heard of DFCO??

Deacceleration fuel cut off, thats likely why it goes lean right after you let off from a WOT run. The motor does not need fuel any more and basically turns into just a air pump with no squeeze and bang of the fuel. Just pumps air in and pumps air out, injectors shut off, timing bottoms out.... the works.

Completely normal and a standard function on pretty much all cars, it's how they save fuel. The second you tap the gas, everything comes back alive.

Not sure if you shut it off or not, didnt check file.


Otherwise going lean right after you ham on it and are coasting isnt abnormal. It's not going to need alot of fuel as rpms fall.

[RonSSnova]

DCFO is shut off in his tune.

Paul,

You are using the VE table to set the fueling under boost or any WOT for that matter and that isn't the correct way to go about it.
Fuel enrichment should come from the PE table. BE table is a crap shoot as there is a delay involved, so most use it for a backup and simply mimic the PE table with it in the boost areas.
The goal is to calibrate the VE table in as many areas as you can, including boost. This will allow you to easily change the AFR when in PE and Boost vs RPM with simple changes to the PE table.
As was mentioned, you really need to have the wideband logged with the other data.

As far as it going lean when off the throttle, how lean?
There isn't a lot of info in your log, but I see the map reads 78kpa with the throttle closed at idle, I would expect that to be closer to 50kpa.
Are you sure you don't have a vacuum leak somewhere?

[chiropaul]

Thanks for the reply, I appreciate it. I thought i had subscribed to this thread and missed your response earlier, sorry for that!!

I was logging my wideband through the EGR. I created a custom PID and when I view it on my scanner it shows the AFR and AFR error %. Not sure if that effects your ability to see it on your side. I can tell you that my AFR has gone up to 15.1-15.5.

I'm going to look at the files you attached, the tune I used as the base for this was from Sloppy Mechanics Wiki because he used the same injectors and turbo. Only change was his motor was a 6.0 and mine was a 5.3. Plus I have a Lil John's custom turbo cam. Thanks again for the help.

[chiropaul]

DCFO is shut off in his tune.

Paul,

You are using the VE table to set the fueling under boost or any WOT for that matter and that isn't the correct way to go about it.
Fuel enrichment should come from the PE table. BE table is a crap shoot as there is a delay involved, so most use it for a backup and simply mimic the PE table with it in the boost areas.
The goal is to calibrate the VE table in as many areas as you can, including boost. This will allow you to easily change the AFR when in PE and Boost vs RPM with simple changes to the PE table.
As was mentioned, you really need to have the wideband logged with the other data.

As far as it going lean when off the throttle, how lean?
There isn't a lot of info in your log, but I see the map reads 78kpa with the throttle closed at idle, I would expect that to be closer to 50kpa.
Are you sure you don't have a vacuum leak somewhere?

Ron,
As far as vacuum leak, i'm sure it is possible there is a vacuum leak. I'll need to test and make sure.

As for the VE table I was going off of CPIG's tuning help file I found on ls1tech where it uses the AFR error % from the scan to then apply it to the Primary VE table. Using KR to change the spark advance table. Do you have a preferred method for tuning PE??

I threw a pic of the car that this motor is in.

[RonSSnova]

Nice car! I like to see what folks are working on.
Are you on LS1Tech?

I'm not familiar with that tuning method. It works, but it's too much work and like I said doesn't allow for nice clean quick fueling changes.
If you look at AIR fuel Ratio Commanded in your table display, note that it says 14.63 even though you are in boost. When you use the PE table correctly, your commanded fuel will read what you want to be in boost. Approx 11.5:1 in your case? I'm running E85, so I don't know what guys use for pump fuel.

The numbers in the PE table represent EQ ratio. EQ ratio is defined as Stoich(14.63)/Desired AFR(11.5:1) So the numbers would be 1.27 from say 3000rpm up. Or wherever the turbo begins to build boost. That's the basic explanation. The BE table is the same, except its boost related.....and uses kpa to start adding fuel. Same numbers go there. Like I said, I'm not using it for fueling.

So, when you add this to your tune, your car is going to go really rich because you are adding fuel via the VE table. What you can do is reduce those numbers in the VE by the % diff between 14.63 and 11.5 or whatever AFR you are seeing. Actually, reduce by slightly less.

On the same power enrichment page, change the ramp to 4 and the delay rpm to 0


Now, do you have to do all this? No, you don't. it is just the more "correct" way to do it. And you will have to retune the VE table in the boost area.

BTW, good that you are logging AFR. And you are correct, we can't see your custom PID......which sucks!

Ron

[SultanHassanMasTuning]

after a WOT run and if your fueling is correct, but i would use the PE and BE tables as its meant to be tuned (then you will have to redo your WOT in VE area.

as for running leak as your coasting its fine, as long when you get back on the throttle it will be stoich or how ever you have set it up

[chiropaul]

Nice car! I like to see what folks are working on.
Are you on LS1Tech?

I'm not familiar with that tuning method. It works, but it's too much work and like I said doesn't allow for nice clean quick fueling changes.
If you look at AIR fuel Ratio Commanded in your table display, note that it says 14.63 even though you are in boost. When you use the PE table correctly, your commanded fuel will read what you want to be in boost. Approx 11.5:1 in your case? I'm running E85, so I don't know what guys use for pump fuel.

The numbers in the PE table represent EQ ratio. EQ ratio is defined as Stoich(14.63)/Desired AFR(11.5:1) So the numbers would be 1.27 from say 3000rpm up. Or wherever the turbo begins to build boost. That's the basic explanation. The BE table is the same, except its boost related.....and uses kpa to start adding fuel. Same numbers go there. Like I said, I'm not using it for fueling.

So, when you add this to your tune, your car is going to go really rich because you are adding fuel via the VE table. What you can do is reduce those numbers in the VE by the % diff between 14.63 and 11.5 or whatever AFR you are seeing. Actually, reduce by slightly less.

On the same power enrichment page, change the ramp to 4 and the delay rpm to 0


Now, do you have to do all this? No, you don't. it is just the more "correct" way to do it. And you will have to retune the VE table in the boost area.

BTW, good that you are logging AFR. And you are correct, we can't see your custom PID......which sucks!

Ron

Went in a changed the PE and BE tables and then did some logging of AFR error % and KR. Edited the tune based on that and it runs much better. I am at work, but when I get back home I will post up the new logs. I wish you guys could see the custom PID so you can see my AFR. Makes it hard to get help on this stuff. But all your advice has helped a ton already.

Also I checked and there is no vacuum leak that I could detect. My map does drop to the mid 50's on deceleration, I don't know what was going on that night. I'll post my log this afternoon/evening when I get home from work.

THANKS GUYS!!!!

[chiropaul]

Nice car! I like to see what folks are working on.
Are you on LS1Tech?

I'm not familiar with that tuning method. It works, but it's too much work and like I said doesn't allow for nice clean quick fueling changes.
If you look at AIR fuel Ratio Commanded in your table display, note that it says 14.63 even though you are in boost. When you use the PE table correctly, your commanded fuel will read what you want to be in boost. Approx 11.5:1 in your case? I'm running E85, so I don't know what guys use for pump fuel.

The numbers in the PE table represent EQ ratio. EQ ratio is defined as Stoich(14.63)/Desired AFR(11.5:1) So the numbers would be 1.27 from say 3000rpm up. Or wherever the turbo begins to build boost. That's the basic explanation. The BE table is the same, except its boost related.....and uses kpa to start adding fuel. Same numbers go there. Like I said, I'm not using it for fueling.

So, when you add this to your tune, your car is going to go really rich because you are adding fuel via the VE table. What you can do is reduce those numbers in the VE by the % diff between 14.63 and 11.5 or whatever AFR you are seeing. Actually, reduce by slightly less.

On the same power enrichment page, change the ramp to 4 and the delay rpm to 0


Now, do you have to do all this? No, you don't. it is just the more "correct" way to do it. And you will have to retune the VE table in the boost area.

BTW, good that you are logging AFR. And you are correct, we can't see your custom PID......which sucks!

Ron

Hey Ron,
When it comes to hand smoothing the VE table after making corrections what do you recommend?? Is there some sort of guidelines you would follow.

[RonSSnova]

Oh boy. if you make it look really pretty, you just have to retune it again because you will muck up known good data points.
I just look for outliers when in the 3D mode and smooth those out. Then drive and re-tweak.
I'm sure as you have noted, there are a ton of cells you will never hit.
You have also probably noted, that it goes right past a lot of the table when it goes into boost.

If a guy had his own dyno, and a triple disc lockup converter, and a couple of weeks, you could probably do a really nifty job.
Oh, add a really good radiator and a big ass fan to that task.......

Ron

[chiropaul]

Oh boy. if you make it look really pretty, you just have to retune it again because you will muck up known good data points.
I just look for outliers when in the 3D mode and smooth those out. Then drive and re-tweak.
I'm sure as you have noted, there are a ton of cells you will never hit.
You have also probably noted, that it goes right past a lot of the table when it goes into boost.

If a guy had his own dyno, and a triple disc lockup converter, and a couple of weeks, you could probably do a really nifty job.
Oh, add a really good radiator and a big ass fan to that task.......

Ron

Ya I'll pull it onto my dyno after I get back from cruising my 100ft yacht. As long as it runs nice and strong, and is not going to grenade on me I am going to be happy. Thanks again for all your help.

[RonSSnova]

You have a dyno on your yacht?
Cool!

Never been on a dyno myself. Just street and track tuning. It's a slow process.

Good luck and have fun.

[JamesLinder]

1) you will never obtain peak performance out of your motor with a choppy VE table like yours
2) too much DFCO will cause valves to burn if it kicks in too soon and remains in DFCO too long
(performance motors require changes to the DFCO settings) look at those used on a 2002 Z06
or similar as set by GM from the factory)

[chiropaul]

1) you will never obtain peak performance out of your motor with a choppy VE table like yours
2) too much DFCO will cause valves to burn if it kicks in too soon and remains in DFCO too long
(performance motors require changes to the DFCO settings) look at those used on a 2002 Z06
or similar as set by GM from the factory)

James,
I understand what you are saying, and I see how it looks on the 2D and 3D graph. So if I am trying to smooth things out on the VE table should I try to bring the figures up slightly where there is a "valley"? What is the general rule of thumb on this so I don't make a mistake going the other way?

Also I believe I have my DFCO disabled. Should I enable it once I am done tuning the VE table??

[EDH]

Are you sure your map sensor/ settings are correct? I ask because I just went thru this with a Turbo 6.0 I am working on. The car idled in the 60-70 kpa region and when at 0psi gauge my logs showed 135kpa. Turns out what was suppose to be a 3 bar map sensor was a 2 bar.