Dealing with a hunting condition when putting the clutch in when coming to a stop, and also when reving the car in the driveway. Datalog attached. Have attempted to smooth the VE table further thinking it may be due to spikes in the VE table following VE learns

datalog from sitting in the driveway and revving it enclosed. Also a nifty chart comparing revs to wb; which is making me think I might still be a little lean at lower RPM.

Vortec LT4 hotcam T5 with warm idle set to 725rpm. Car is running open loop

thoughts most welcome!

 

Possible to post your bin? Often times I look people's bins in context with their datalogs and things start to make more sense.

Or you can send it to me

ultm8z@yahoo.com

 

Just looking at your data... some initial comments/questions:

1.) I don't think you're too lean... your AFR is down around 13.5. If anything it might even be too rich. Even with my Miniram idling in open loop, I idle around 14 to 14.25:1.

2.) I'm assuming you still have the TPI manifold. Is your MAT sensor still in the plenum? I'm noticing your air temperature isn't tracking with the coolant temperature. Though that could be a function of time as it looks like the coolant temp is still low (only ~66C when the data ends).

3.) You might try opening the throttle blades a bit to minimize how much the IAC has to do. Get to the point where your IAC steps are less than 10.

4.) With the hot cam, you might try a little more idle spark timing. I run about 25° at idle with my Miniram (as did the 4th gen LT1's).

5.) If you have a data log that captures the time you put in the clutch and get the resulting hunting idle

 

thanks ULTM8Z.

Have the pro flo XT edelbrock intake, but yeah running an EBL ECU with the batch fire injection. MAT is in the intake track near the air filter. Car was still warming up when I took the data log - from memory the IAC is in the teens when warm and idling.

Good call about the idle SA.

Yeah was looking at the AFR swings post revving it and looks to swing between rich and lean after I rev it and idle drops to around 500rpm.

Have smoothed the VE table some more to try this coming weekend; will report back with an updated datalog

 

Did you make the necessary changes to the MAT subroutines for your relocated sensor? Assuming EBL has the same as 7730.

Yeah the short runner intakes are going to like spark timing

The map swings during the events are big enough to trigger delta MAP AE which makes the transient rich condition even worse.

 

ooh I don't believe I have. I have ticked the 'Option Word 4 - Bit 4 - IatSa' flag but nothing else- guidance v. welcome

 

I don't know specifically about the EBL... but I'll tell what the 7730 needs.

When you pull the MAT sensor out of the plenum, you longer need the ECM to compensate for heat soak (at least not to such an extent), which is what the INV MAT table is all about.
The lower the airflow going through the manifold, the more the sensor reports the temperature of the metal intake manifold (which is effectively at coolant temperature). The higher the airflow, the more the air is able to cool the sensor down to match the air temperature.

Two options for the INV MAT table when you relocate the MAT sensor...

1.) Disable the table altogether. In the Switches, there's a switch for whether you want this Inv MAT Table enabled. Option 1 is to disable it. That's what I did with my Miniram when I had to relocate the sensor. You may need to re-adjust the VE tables because this tends to make it run a little more on the rich side. But it's good for a more performance oriented tune rather than emissions or fuel economy. Since my '71 Camaro is not an economy car, I didn't care...lol.

2.) You could try putting in the Inv MAT values for an LT1 Camaro/Corvette, which also had the sensor in the air tube ahead of the throttle body. My experience tuning on the Miniram indicates that (despite the different ECM's) the software code between the DA2 Vettes (92-93 LT1) and the 8D Vettes (90-91) is largely the same. I've copied and pasted so many of the fueling values and parameters from DA2 to put in my Miniram'd 8D and it works beautifully... especially the accelerator enrichment.

INV MAT tables for 8D and DA3 are below.

GM must have thought that the sensor gets some amount of heat soak at low air flows on the LT1 despite having the sensor in the air tube (probably due to general engine compartment heat), since the 4th gen LT1's maintained use of the INV MAT table, but you can see that it's far less than being screwed into a metal plenum. Then at higher airflows the two tables start to converge around to a multiplier of .100 to .125.

On my Miniram, I put the sensor out at the end of the air tube where the filter is, outside of the engine compartment. So I get no heat soak whatsoever, which means the INV MAT table isn't needed at all.

Factory 8D



92-93 LT1 (DA3)

 

Thanks ULTM8Z. I can’t seem to find that option word in the EBL xdf so will try at those tables. The hex id finds the VE table (?) so yeah, the EBL xdf is a little funky

Have tweaked the bin since running it yesterday, unhelpfully overwriting the one the datalog I shared is based on. Will share the tweaked bin this weekend; appreciate it!

 

I'm certainly no EBL expert. However I do have the xdf file for Tunerpro so I can try to take a look.

 

Regarding the IAT/MAT on EBL, Flash specifically but I think P4 handles it the same, the only table that has effects on fueling with the IAT/MAT is the IAT/CTS - Blend Filter. I have my IAT next to my air filter in front of my drivers tire. Mine starts at 29.41% at 0 Gm/Sec and decreases to 4.71% at 255 Gm/Sec.

Then you have the SA tables:
SA-IAT/CTS or IAT Compensation
SA - IAT/CTS Comp Bias SA

Those two work together to handle SA changes via IAT.

Then Option Word 4 - Bit 4 - IATSa which when set has the SA parameters only affected by IAT sensor. So zero blend. I assume this means the fueling side of things still has the blend table affecting it.


How are you throttle follower tables setup? Seems like it isn't hanging as much as it should on rpm drop after the rev. On a manual car like ours, you tend to want a little hang for RPM matching while shifting. If it drops like a rock on clutch push, it can cause jerky shifts.

 

thanks both

ULTM8Z - my bin file attached. As touched on, this includes some low RPM VE adjustments following the above posted datalog - will share an updated one this saturday as mentioned. Try not to LOL too hard - still getting my head around tuning and recently updated the injector offset as was maxing out on the VE table despite injector DC having a decent headroom. See below for my IAT/MAT table (I think) - looks quite different to what you have - maybe again because of the EBL XDF

dabomb - yes my IAT/ CTS blend filter table sounds much similar to yours as stock. Double checking, this is what you are running with the IAT/ MAT repositioned by the filter? Also yes the revs do drop pretty sharply but my base bin is the LB9 5 speed one so would've hoped those manual transmission configs were in the right ball park.

 

Keep in mind you should not be adjusting injector offsets to get your VE table away from maxing out. That is done by changing (lowering) the BPC - BPC vs VAC table and then multiplying the entire VE tables by that percentage of difference. Your injector offsets are determined by your injector spec sheet, you don't want to venture away from those values.

Your blend table is basically right where mine is at. What IAC steps are you idling at with fully warm engine?

 

Try this. Made no changes other than VE table. You had a heck of a hole in the low RPM/low MAP areas. Could've been falling into it and going way lean. Go into your WUD preferences and check what smoothing factory you are using. Keep in mind you will need to check on your VE tables and manually smooth them as your learns progress.

 

Glad we have someone good with the EBL on this thread now... I was going to be up against my own ignorance on that system with a diminishing ability to continue to assist.

Though I'll probably still follow along as I'm curious what the issue ends up being.

 

Ultm8z all good and appreciate the guidance

ty dabomb. Will load this up this weekend and revert

poor language by me. I meant the field in which you enter the size of your injectors

iac is down to the high teens at 725rpm when warm I recall. But will confirm this weekend

 

Looking at his VE Table I figured the best place to start is there. The two spots I have selected are his idle area. 50kPa at 700 & 800 rpm. Granted that was going off of the log that wasn't to temp. But regardless has a steep drop off there below 50kPa. As you know with your tuning on 7730 it has the potential for sure to mess with idle area as it will stumble as it hits that large fuel transition.


I also used the tunerpro smoothing tool on high speed table just to get the sharp up downs reduced for him to get some learns going.

 

I downloaded the EBL files needed for Tunerpro (want to start learning about the EBL)...

Some questions/comments:

1.) Are you actually running 28 lb injectors? If so, what manufacturer and p/n? Do your offests match the injectors?

2.) Regarding IAT...

For a Pro-FloXT, where the runners are much shorter than a TPI, I wonder if you'd want to significantly reduce the % at low airflows since the air has very little time to heat up. I actually did the equivalent of completely zeroing mine out. I figure since heat transfer only happens at the boundary layer of the manifold walls, and there's so little air flowing through the manifold at low engine speeds, that there's essentially not enough time for the coolant temperature to have any effect on the air temperature.

3.) I'm a little perplexed by your delta-TPS AE table values... You're not getting any off throttle tip-in stumbling with that?

 

Very interesting...

 

I was definitely rich with AE from the base tune I started with. Even after multiplying out the injector size increase. Mine seems to want similar to the miniram. Large initial and taper off from there. The more I think on it, even being a LTR, it still has injectors right near the intake/head transition so similar surface area for it to stick to just as much as any other intake with injectors mounted like that would. So you would think AE would be similar. I've been fighting proportional gains so haven't spent much time with AE but that is the trend I see. I've dialed it back some already in my tune.

 

iterative update that the tune you provided dabomb (coupled with the increased idle SA to 24 that ULTM8Z suggested) made a noticeable improvement to the idle. What is however interesting is that after a few ve learns (with the system pulling fuel), it started to hunt. My suspicion is that 725rpm LT4 hot cam idle is playing tricks on the wideband. I'm going to manually smooth an add a bit of fuel to that part of VE table and re-analyse.

I'll update the different bins following VE learns at some point tomorrow.

In other news, I took the car to a dyno today (dyno dynamics, shoot out mode 8) and it made 365hp / 370 ft/lbs torque with a slightly wavy AFR but which stayed in the 12s for the most part (-3500 onwards). I'm told to disregard the wild AFR swings as being a dyno probe issue. Not perfect (and I certainly plan to continue tuning), but overall looks safe at WOT

 

If you're saying that until it started pulling fuel, it was behaving much better. That may be an indicator that you should richen up your idle R/L threshold a bit. That way a BLM of 128 at idle will be a little bit richer than 128 everywhere else. For example, I idle about 14.0 to 14.25 with the Miniram in open loop idle. Any leaner than that and I can start feeling misfires.

 

Decaying out quickly is key for the Miniram, yes.

On my AE delta MAP decay for 8D, I have it decaying out ~10% more quickly than stock.

Then on AE delta TPS, factory calibration has it lasting for 12 distributor reference pulses (DRP's). I shortened it to 8 DRPs.

Not sure what the equivalent parameters are in the EBL though...

 

After your learns you need to check your VE tables in the areas I modified around idle. It will not learn in the low MAP low RPM area as the motor is never ran at those values. The hole that is created will cause a hunting idle.



For that there are "filter" tables that affect AE duration (and to a smaller degree the magnitude of AE). Then "PW" tables that affect AE magnitude. The 6 primary AE tables in EBL Flash (and likely EBL P4) are
AE - TPS PW
AE - TPS Filter
AE - MAP PW
AE - MAP Filter
AE - CTS Multiplier %
AE - RPM Multiplier %

Then there are a few parameters that handle activation of AE.
AE - Delta Map Qualifier
AE - <TPS% Double MAP Threshold
AE - Delta TPS% Threshold for AE
AE - IAC Opening Fuel
​​​​​​​

 

AE - Delta TPS% Threshold for AE

That's a critical one for initial throttle response and the infamous off idle tip in stumble.

A change of just couple percent made a huge impact.

 

Yes certainly will be manually smoothing

was thinking about the MAT relocation piece more and reading some good threads on the topic

i have the original brass TPI MAT sensor relocated upstream by a conical air filter. Post the dyno session where the car was turned off and then warm started about the ten minutes later, the VE learn was adding a noticeable amount of fuel (in some cases 12 percent). This aligned with a wideband reading about 2 whole points leaner. As I drove the car on the motorway/highway the VE learn adjustments for the same areas were lower (though still in ranging upto about +6. However as the same areas were all not re-learned, this resulted in a wavy VE updated table

a datalog for that journey home would have been useful…

I’ve ordered a plastic birdcage IAT sensor for a later GM car which I’ll try this weekend; can’t see it hurting

 

That scenario, a hot restart causing very lean afrs for several minutes, is exactly why I moved away from open loop. Even with a plastic birdcage IAT I was having those issues. Nothing I did helped except for forcing the HotRst parameters to activate that mode for 2 mins after those restarts. Which is just a band-aid fix.