ECMlink AF spikes on throttle lift-off

[90Tsireborn]

Hi Guys. Trying to dial-in my ECMLink v3. Out for cruise logs and whenever I lift off the throttle (in or out of gear, various load factors, various rpms and gears), the AF spikes to 20-22.

As soon as I apply any throttle at all, it drops back down again to a good number.

The number is verified via wideband (both front 02 and LC-1 show the same #s).

Is there an adjustment to lift-off throttle or TPS or other that I should make to correct?

Thanks in advance.

 

[Anfurnyy]

How fast does it spike to that?

There is such a thing as fuel cuts during in gear decel which goes full lean since cutting off all injectors. Usually called DCFO or something similar.

Also if you can upload a log of it happening it'll help us figure out what's going on

 

[FIBA M - EC17PSE]

in gear thats normal but out of gear its not. when your coasting in gear the fuel shuts off (clean burn) its normal on all cars.

out of gear though is another concern as to why it is doing that as the rrevs are lower generally

 

[90Tsireborn]

Within 1 second of lifting-off, generally. From the logs, it climbs from under 14.7 to 30 in 0.1 seconds on ECMLink and wideband indicates 22 (maybe max it can display) in the same instant. Actually, went as high as 40 in a few places later in the log. This was a fully warmed-up car, intake and egt's fine, etc.

 

[steve]

in gear thats normal but out of gear its not. when your coasting in gear the fuel shuts off (clean burn) its normal on all cars.

out of gear though is another concern as to why it is doing that as the rrevs are lower generally

The ECU doesn't know if your in gear or not. It knows when the throttle is closed and speed not equal to 0. If you're coasting in neutral you'll see injector cutoff just like you do in gear.

 

[FIBA M - EC17PSE]

The ECU doesn't know if your in gear or not. It knows when the throttle is closed and speed not equal to 0. If you're coasting in neutral you'll see injector cutoff just like you do in gear.

Its based on revs. Not speed. Coasting in neutral the revs are lower so the cutoff kicks out. Because its needs to maintain fuel to keep the engine alive. If i put my car in neutral and coast its at 14.7 down a hill because it needs it. If i put it in gear the revs are higher due to the gearing now being used so wont add fuel till it gets to its selected target of revs which i think on my car stock or not was about 1600-1800rpm. Its always been that way and has never changed. It always leans out on a hill till i get real slow so the revs drop. Coasting it always uses fuel

 

[90Tsireborn]

Perhaps, a more important question is: is it detrimental or potentially damaging to the engine to let it go to full lean abruptly every time I lift fully off the throttle? Seems like AF readings of 30 or 40 to 1 would be bad even if not under load.

Thanks for the thoughts.

 

[dwb]

This sounds like normal behavior to me.
Mine goes full lean if coasting in gear with no throttle. Also goes full lean when I approach a stop - no throttle, RPMs dropping with the clutch disengaged until it hits idle and once it catches idle, the AF returns to 14-ish.

 

[steve]

Perhaps, a more important question is: is it detrimental or potentially damaging to the engine to let it go to full lean abruptly every time I lift fully off the throttle? Seems like AF readings of 30 or 40 to 1 would be bad even if not under load.

What we'd like to see is a log so we can be sure if it's acting normal or if there is something unusual going on. That will tell us how you have ECMLink configured and what the ECU is seeing before, during, and after along with what the ECU is doing in response.

A great read is the fuel section on the 1990 Technical manual https://www.dsmtuners.com/threads/1g-dsm-1990-technical-information-manual.517385/ It goes into many details on how the ECU works.

 

[jdxnc]

That's normal behavior.