VE Values Low at Idle - Standalone

[944m3]

Is a VE value of ~30 at idle to low?

Car seems to be running well, but I can’t seem to improve on my VE at idle. If I put it up to 40 the long term fuel trim starts taking out fuel to about 30. At that point it starts to get to 14.7 AFR.

I’ve read someone else using VEMS had a very similar issue but never resolved it.

Before i go down a rabbit hole, thought I’d ask what others are seeing for VE at idle.

[four0four]

That does seem low. Are your injector compensation values correct? I wouldn't be surprised if they're quite a bit high.

[944m3]

I’m using a fuel pressure sensor. In theory the standalone reads actual fuel pressure and compensates accordingly. I’m also using the built in injector configurations for my Siemens injectors, which means the standalone deals with deadtimes.

But after your suggestion I’ll switch everything back to manual mode and see if anything changes.

What are folks seeing for pulse width and deadtimes at idle? My logs show at 13.41v 897 RPM my pulse width was 1.306ms and deadtime 1.007ms. Idle was steady.

[walfreyydo]

Volumetric Efficiency values (VE) will vary based on each specific vehicle and setup especially if you have different injectors or other mods (ie: maf or speed density conversion, cams, etc). VE values can only really be compared across two vehicles with the exact same setup, and even then there may be slight differences (small vacuum leak, differences in components/calibrations, ignition/cam timing, etc).

If the car idles well, then I wouldnt worry too much about it, although increasing the VE values should make the car run richer, so the fact its going leaner is unexpected. I dont know enough about your particular settings and setup to understand why that might be.

My guess is that you are running closed loop and the algorithm is automatically trimming down your fuel values because of your settings or your target AFR at idle. Something is intervening and over-ruling your VE values so my guess is its your closed loop settings or something else (ego correction or similar).

[944m3]

I’m not to worried about it but I am curious to why it’s happening. It doesn’t seem to be in line with the “internet”.

And your right, I am using closed loop idle with a target lambda of 1. And actually it runs rich at maybe ~10 AFR. I have to lower the VE value for it to go to 14.7 AFR, which it can maintain once it gets there.

My deadtime seems to be higher than what I’ve found online for my injectors. I will need to try different settings and see what happens.

[walfreyydo]

Only thing to flag is changing dead time may impact your current VE table, requiring you to re-tune it or adjust all values by a certain percentage.

Here is a good read:
https://support.haltech.com/portal/en/k ... o%20normal.

Dead Time Too Low
When the dead time table is set too low we need to over-compensate in the light load areas by increasing the VE numbers to get more fuel. This very obviously shows in the VE table that something is not set correctly. We must increase the dead time to bring the VE numbers back to normal.

[PSU_Crash]

What standalone? In my 2.6 turbo mitsu running megasquirt, the VE values are in the high teens around idle @13.5 AFR. As others stated, I'd check your injector settings. Also the required fuel setting. At idle I always shoot for a little rich. Say 13.5-13.7 BUT if yours is happy at stoic, then that's what I'd run.

[944m3]

What standalone? In my 2.6 turbo mitsu running megasquirt, the VE values are in the high teens around idle @13.5 AFR. As others stated, I'd check your injector settings. Also the required fuel setting. At idle I always shoot for a little rich. Say 13.5-13.7 BUT if yours is happy at stoic, then that's what I'd run.

MaxxECU

I’ll play around with the settings when I get a chance. But maybe it’s just what the car wants.

[four0four]

I’m using a fuel pressure sensor. In theory the standalone reads actual fuel pressure and compensates accordingly. I’m also using the built in injector configurations for my Siemens injectors, which means the standalone deals with deadtimes.

But after your suggestion I’ll switch everything back to manual mode and see if anything changes.

What are folks seeing for pulse width and deadtimes at idle? My logs show at 13.41v 897 RPM my pulse width was 1.306ms and deadtime 1.007ms. Idle was steady.

that'll be it then - if you have the ECU applying corrections for fuel pressure (gauge pressure) *and* the FPR is referenced to the manifold pressure you'll have confusing/useless results like this. I think it would get quite dangerous to the motor under boost too: FPR drives up pressure to compensate for increased MAP, ECU pulls injector pulsewidth to compensate for "extra" fuel pressure...you get the idea

After some quick reading it seems like MaxxECU intends for this to be used to track deviations and as an additional safety measure. I suspect if you didn't set that up precisely correctly, it could have this effect. Maybe disable it for now and try to get things idling properly without? You can re-enable it later and use it as intended. The FPR mechanically tracks MAP pressure on its own, insuring that the injectors "see" whatever pressure it is configured to regulate to no matter the boost/vacuum level. ECU corrections should be just that: corrections applied on top to handle unusual scenarios, imo. I'm just some guy though!

[fasterfaster]

Is a VE value of ~30 at idle to low?

I'm still dialing mine in, but I'm at 29 on my ClassicECU/Speeduino (stock injectors and 2.5bar FPR), so 30 doesn't seem crazy. If anything I expect to go lower once I'm more dialed in, as I'm running rich and fast right now, even at only 6 deg of advance.