VE Values Low at Idle - Standalone

[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.

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!

We’re all just learning haha Appreciate every suggestion.

You have given me food for thought. I will double check my fuel pressure sensor and the ECU settings. The sensor readings are used to adjust the injector pulse width so it can definitely have an impact at idle. I will try disabling it and seeing what happens.

[944m3]

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.

Ok that’s good to know.

Though this morning I drove to work, haven’t changed anything yet other than raising my VE to 30, and VE dropped to 16 after applying fuel adaption trims. This was about an hour commute through the suburbs. This is exactly what another post was describing.

I’ll reset everything and try different settings. Will update when I learn something.

[944m3]

Doing a little more research, I’m starting to think I have a leaking injector. Which means I’m getting more fuel and the ECU keeps working to lean it out.

Anyway to test this or do I have to send them out?

[fasterfaster]

Not sure if it's helpful, but here's my latest VE table. Still refining, and with my current setup and tired wastegate I can't boost above 160kPa, but the rest is a decent reference for a stock 951 - 2.5bar FPR, OE injectors, AFM still mechanically in place (though fuelling is based on MAP).

Screenshot 2026-04-26 at 7.06.41 PM.png (545.31 KiB) Viewed 269 times

Screenshot 2026-04-23 at 4.20.35 PM.png (442.15 KiB) Viewed 321 times

edit: may as well include ignition table

Screenshot 2026-04-24 at 2.05.24 PM.png (367.1 KiB) Viewed 293 times

I've got a few more VE tuning cycles to do, and then I'm on to throttle enrichment, but these are probably close. Running conservative ignition as this ECU doesn't yet have knock control functional.

[944m3]

Thanks for the tables. Always good to see other reference points.

[944m3]

All the evidence was pointing to bad injector or injectors. ECU pulling fuel resulting in low VE numbers at idle, rough idle, trouble starting when engine was warm. So I purchased new injectors from Five0 Motorsports and wow what a difference. Best way I can describe it is my engine feels like a sewing machine now. The difference is ridiculous. Not sure how long the injector was bad or maybe was slowly going bad that I just got used to it. Not sure I would have figured it out without the ECU. Access to the VE table and logs made it much easier to spot.

For those interested, I purchased here:

https://www.fiveomotorsport.com/109991- ... rMD-Omkjdm

Really happy with results.

[944year83]

All the evidence was pointing to bad injector or injectors. ECU pulling fuel resulting in low VE numbers at idle, rough idle, trouble starting when engine was warm. So I purchased new injectors from Five0 Motorsports and wow what a difference. Best way I can describe it is my engine feels like a sewing machine now. The difference is ridiculous. Not sure how long the injector was bad or maybe was slowly going bad that I just got used to it. Not sure I would have figured it out without the ECU. Access to the VE table and logs made it much easier to spot.

For those interested, I purchased here:

https://www.fiveomotorsport.com/109991- ... rMD-Omkjdm

Really happy with results.

Which injector would be suitable for a 1983 944 Series 1?

[944m3]

All the evidence was pointing to bad injector or injectors. ECU pulling fuel resulting in low VE numbers at idle, rough idle, trouble starting when engine was warm. So I purchased new injectors from Five0 Motorsports and wow what a difference. Best way I can describe it is my engine feels like a sewing machine now. The difference is ridiculous. Not sure how long the injector was bad or maybe was slowly going bad that I just got used to it. Not sure I would have figured it out without the ECU. Access to the VE table and logs made it much easier to spot.

For those interested, I purchased here:

https://www.fiveomotorsport.com/109991- ... rMD-Omkjdm

Really happy with results.

Which injector would be suitable for a 1983 944 Series 1?

I don’t know to be honest as I’ve only researched for 80lbs injectors for my Turbo.

But I think a few vendors sell rebuilt stock injectors for NA. You’ll need to look around.

[Tom]

The aftermarket injector industry is a bit frustrating in that they seem to label and brand injectors to avoid explaining who really made them and what they really are. Reminds me of the mattress industry where the same big-brand mattress is sold as a different model by every mattress house (after changing the thread color or something trivial) to make comparison shopping difficult and to support the claim that 'only we have the Mega-sleeper 3000' or whatever. I have these injectors and have been impressed by them, but assume they originate as some overseas supply chain generic, then completed in the us to support the made in the USA claim, and flow matched by Five-O:

https://www.fiveomotorsport.com/115u-je ... v14-style/

(And I agree, for a stock '83 car, you want stock injectors. Bigger injectors will just make the car run rich, and produce less power and gas mileage --unless you program the ECU/DME for them. And even then, they won't add any power by themselves.)

[944m3]

To close this out, it’s been a few days of driving and street tuning. My idle VE is ~35 and it’s steady. Meaning long term trim is not pulling fuel in chunks just doing minor adjustments. I think that’s pretty good. I believe removing AFM for a snorkel with cone filter (I got from the Vitesse MAF kit) probably has something to do with a higher VE at idle.

With things now consistent I need to focus on improving my ignition timing table.