I've come across an issue where the tune on the chip behaves differently to the same tune on the Moates Demon.

I tuned a modified b18c on a Mustang Dyno using a JDM P72 (SMD type), Moates Demon and LM-2 serial logging.
The tune went well with no issues, it felt good the A/F's were right where they should be. The owner was with me and confirmed they were happy with the tune.
After the dyno, I burnt the tune to a chip and installed it in a socketed PR3 (through-hole component type) as per normal.

The owner then installed their own wideband O2 sensor, and contacted me to advise that they are experiencing problems with a lean idle, and rich at cruising. I wasn't sure of their electrical knowledge or capability, and so my first thought was that the O2 sensor wiring or install has been mucked up somehow and was giving an odd reading.

I then installed my LM-2 wideband to check the owners claims ... sure enough, it was running lean at idle and rich at cruising ... this was definitely NOT the same tune that I did on the dyno.

My next thought was that there was a difference between ECU's ... The JDM has surface mount components and the PR3 has through-hole components.
So I installed my Moates Demon directly into the owners PR3 ECU to make the necessary changes and rule out a difference in ECU as the cause of the fueling gremlins.
We went for a drive and identified the problems and made the necessary changes to the tune.

We BOTH saw the A/F's at idle (14.5:1) and BOTH agreed that we were happy with the new changes, so I saved the tune to a .bin (as per normal) and burnt it to a chip .... within a 5 minute period the new tune was installed in the same ECU I had just made changes with.

Well bugger me ... the A/F's had gone lean at idle (16.2:1) and after a couple minutes settled down to 15.4:1 at idle. We BOTH saw and agreed that this is NOT what I tuned and NOT what I saved ...

It is the first time I've come across this issue and so I spent a fair bit of time trying different combinations to work out what exactly caused it.
Somewhere between the Demon, saving the tune, burning to a chip, something has changed the behaviour of the tune ...

Does anyone have any idea what it could be?

Did you try on the Demon without the laptop connected?

HRTuning wrote:Did you try on the Demon without the laptop connected?

Only for a short period of time after I saved the tune. I then disconnected the Demon from Neptune, but it was still plugged in to the laptop ...

Would it make any difference?

What are your thoughts?

If the ECU is not receiving solid voltage it's possible you're backfeeding it some voltage through the USB/Demon. This could effect operation.

HRTuning wrote:If the ECU is not receiving solid voltage it's possible you're backfeeding it some voltage through the USB/Demon. This could effect operation.

From what I observed on Neptune while I was checking the battery offset table was that the voltage appeared to be fine and solid. Voltage would drop to 12.5v under high load (high beams on, aircon on, all power window buttons held on). After minor battery offset adjustment the a/f's were solid under any varied electrical loading.

The laptop was running off battery at the time ... if that makes any difference.

How does one monitor the voltage to the Demon?
Are there any other likely causes?

None I can think of.

HRTuning wrote:None I can think of.

Odd ... could the Demon battery be the culprit?

Thank you for your quick responses. Awesome customer service as always

Not likely. The Demon battery is only used for backup. When powered by USB or the ECU itself that's where it's sourcing power. Try removing USB and see if it has any effect with Demon.

HRTuning wrote:Not likely. The Demon battery is only used for backup. When powered by USB or the ECU itself that's where it's sourcing power. Try removing USB and see if it has any effect with Demon.

Sure thing.

Thanks for the quick responses and top notch customer service

hi guys.
new here but im having the same problem.
tuning via ostrich, burn a chip and the tune behaves as if the injector deadtimes are off and runs lean on idle and low load conditions. runs perfect off the emulator though...

Hi guys, late to the party BUT.

I had a customer complain about the same thing. I was able to prove on his particular setup it was nothing to do with chip vs emulator and its actually IAT and fuel temp (heat soak) (while swapping ecus over) which affects things.
This is ESPECIALLY apparent when running non stock injectors (especially large ones).

We went for a drive and I datalogged with the chip and got him to get IATs and ECT back to how they were, then came to a stop at idle and AFR were the same.

Basically IAT table seems sensitive (remember our IAT sensors are quick to heat up but SLOOOWW to cool down), also there are a number of things going on that affect AFR that you can't really account for. (unless you add fuel temp sensor and add an offset for that?)

I believe the MAIN culprit is IAT, I find the same things with my own car JUST on demon and stock injectors.
Oh P.S The IAT table out of the box is not ideal (20C is the agreed reference point for zero offset, with around 2-3% decrease in fuel for ever 10C above this) however you are governed by where your IAT is located (real temp?) and how fast it reacts, also at what load is the engine at vs the temp. It gets VERY complex.

Generally things SHOULD balance out under full load (unless you are wayyyy off)

Great information!