Overrun fuel cutoff - not happening!

stevieturbo
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Joined: Sun Dec 07, 2008 2:04 pm

Re: Overrun fuel cutoff - not happening!

Post by stevieturbo »

I guess that also makes sense, certainly for all the other more brief fuel cut scenarios
dr_jones
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Joined: Wed Jun 08, 2016 3:24 pm

Re: Overrun fuel cutoff - not happening!

Post by dr_jones »

Thanks for the clarification on the fuelFinalPri logs - that makes sense.

Just got back to this thread - trqFuelSev is also being registered at ORFC times here but oddly the 'result' seems a little unpredictable - in some cases I'm seeing >20 AFR and in others 15s or 16s (log attached) - ORFC engine speed is set as 2500 and hysteresis is at 200rpm.

Injectors are very new still but maybe I do have a leaky one - looking back at historical logs the problem does seem to have become worse over time - however I'm struggling a but at the moment to get solid data as I've this wb02 failure issue ongoing. Hopefully htat wil be rectified shorty so I can dig further into this.
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Slowie
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Joined: Thu Jan 17, 2013 7:30 am

Re: Overrun fuel cutoff - not happening!

Post by Slowie »

I would ignore this until your wideband issue is resolved. Once the fuel cut is registered, it does seem the wideband is "lazy" in going leaner, which could be due to running incorrect temperature.
dr_jones
Posts: 162
Joined: Wed Jun 08, 2016 3:24 pm

Re: Overrun fuel cutoff - not happening!

Post by dr_jones »

Sounds reasonable - what it bugging me however is the popping on overrun I'm getting - so if over run cutoff *is* happening (and an injector leak aside) - then no fuel to burn so no popping...
stevieturbo
Posts: 1321
Joined: Sun Dec 07, 2008 2:04 pm

Re: Overrun fuel cutoff - not happening!

Post by stevieturbo »

Or just ignore the fuel cut altogether and just adjust the overrun cells as required.
dr_jones
Posts: 162
Joined: Wed Jun 08, 2016 3:24 pm

Re: Overrun fuel cutoff - not happening!

Post by dr_jones »

Good thought - so i tried that also but no joy.

What I then discovered was tha over run fuel cut did work if the throttle was very very very slightly open and subsequently that I had an issue with my throttle sensor linearization - in that technically it could go -ve.

Now that is resolved fuel cut once seems to (edit) at least do *something* - but I'm slightly confused as to why that -ve value prevented fuel cut looking at the logs what I see is the when it was NOT working correctly:

tpsClosed = CLOSED
trqFuelSevSrv = OVERRUN

And when is is workign correctly (ie completely leaned out on over run) its the same:

tpsClosed = CLOSED
trqFuelSevSrv = OVERRUN

The only difference seems to by the -ve value on throttle position,

-Ed
Last edited by dr_jones on Wed Feb 08, 2017 7:25 pm, edited 1 time in total.
dr_jones
Posts: 162
Joined: Wed Jun 08, 2016 3:24 pm

Re: Overrun fuel cutoff - not happening!

Post by dr_jones »

Well that seems to have been only a partial success - after a reasonable run I can see I am getting much leaner on over run - and can clearly identify when fuel is reinstated (from both logs and physically) - however leaning out is very slow - it does not snap to lean on over run at all - but rather tapers to around 19 or 20 AFR after around 12 seconds from 3K rpm. Seems mighty sluggish to me and still lots of popping during that lean phase.
TimH
JT Innovations
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Re: Overrun fuel cutoff - not happening!

Post by TimH »

When is idle control set to kick in...could they be fighting? (Not a mapper, but vaguely remember needing to play around with that when tweaking my own car a few years ago).
dr_jones
Posts: 162
Joined: Wed Jun 08, 2016 3:24 pm

Re: Overrun fuel cutoff - not happening!

Post by dr_jones »

Open to all suggestions Tim - that seems logical - right now engine speed hysteresis is set to 200rpm - I can increase that and see what effect it has....
dr_jones
Posts: 162
Joined: Wed Jun 08, 2016 3:24 pm

Re: Overrun fuel cutoff - not happening!

Post by dr_jones »

I've finally got the bottom of the issue.

Nothing at all to do with the ECU side - in fact something far more basic.

We had the fuel tank vent plumbed back into the intake manifold - in fact right next to the no.2 runner - this vent was enough to soot up number 2 plug / (randomly) throw out the afrs at idle / cause the popping and apparent no-fuel-cut situation as well as a previously unsolved issue where the engine ran rough after a fuel refill when hot.

Great to have finally got to the bottom of this and thanks to all who input here!

-Ed
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