Duff Idle Data Log.....

[madspikes 41 1 Cars]

I'm back to looking at the data logs again to try and get an idle below 1000rpm. I thought the problem was down to the injector pulse width being too small, but on looking again it doesnt look like this is the case. The pulse width is around 2.8ms as seen in this datalog sample! I'm really at a loss as to why the engine is seemly cutting out at these lower rpms. Any suggestions please!

 

[[L'e$kro] 2]

before starting looking on the management side, are you sure there is no vacuum leak in your inlet?

What happens if you remove the ICV and blank it off, can't you go below 1000rpm?

Nicolas

[madspikes 41 1 Cars]

I am fairly sure there isnt an air leak, and I have run the system without a icv and had the same result.

 

Slowing down the idle isnt a problem, its keeping it stable. Its rock steady at about 1000rpm, at 800rpm it produces an up and down idle like above.

 

Mad.

[Tom Fenton 1,561]

It looks like you are using advance idle control as well as idle air valve? Looks like these two are fighting each other to me?

[madspikes 41 1 Cars]

It looks like you are using advance idle control as well as idle air valve? Looks like these two are fighting each other to me?

 

I might be being dim, but what do you mean by 'advance idle control'? The idle valve is manually controlled, its either on or off, and in this case its off.

 

I've looked though all my MS setting and cant find anything.... But then sometimes you cant see the wood for the trees!

 

Mad

[Galifrey 1]

I might be being dim, but what do you mean by 'advance idle control'?

 

I read that as ignition advance on the spark as it was peaks and troughs on the graph.

 

Like it was spiking the advance

[madspikes 41 1 Cars]

I thought the ignition spikes were being caused by the engine nearly stalling and thus reading a higher spark advance for that rpm v load setting.

[Galifrey 1]

I thought the ignition spikes were being caused by the engine nearly stalling and thus reading a higher spark advance for that rpm v load setting.

 

 

Entirely possible as they do mirror the RPM, looks like the RPM dropped first, advance stopped it from stalling.

[Tom Fenton 1,561]

There are usually two ways of controlling idle via an ECU. Method one is to allow extra air in which has the effect of increasing engine speed. Method two is to increase ignition advance as revs drop below the desired idle which also has the effect of increasing engine speed.

 

It looks to me from that log that both things are happening, so as the revs drop the ignition advances to try and restore engine speed, plus any effect of the idle air valve, meaning the control loop is not stable and hence oscillates as can be seen.

 

I'd make it so that the idle air valve does the work, and the igntion advance stays steady, and see how that goes.

[madspikes 41 1 Cars]

The idle valve doesn nothing at the moment! and I'm sure that the Megasquirt one has no spark advance as you describe. The spark advance is only coming from my dialed in map.

[Tom Fenton 1,561]

In that case dial out ignition advance as the revs drop to stop it hunting so much, then adjust air bleed to give a steady idle speed, I let mine idle about 1050rpm hot as it will idle steady at this speed without getting grumpy, and it will idle slower when cold more or less from first fire up.

[madspikes 41 1 Cars]

Mine is happy to idle around 1100 rpm... I was hoping to get it a little lower to reduce the idle speed supercharger noise!

[Nitropixie 0]

I'm having this idle problem too on a N/A one. I put the ignition table flat and it still hunts. There aren't any air leaks or aything, tht i know of. And the engine seems to not like running a low rpm. The best i can get also is about 100rpm. I thought it would of been rock solid.

 

Also when it pulls away it feels like its lacking but i'm thinking acceleration enrichment is the problem here

[Nitropixie 0]

Do you have EGO feedback?? It seems to be going rich before it drops in rpm

 

Try turning it off if it is on and see if it improves things so therefore it's not trying to correct itself all the time

[madspikes 41 1 Cars]

I believe I have sorted a nice 800rpm warm idle! I've still got my manually switched valve in to give me a higher cold idle... but I've achieved!!!

 

Here is the snap shot of a data log of the new idle! Ok is not rock steady, but good enough for the moment!!

 

it varies from 750 to 800rpm... but there we go!!

 

 

 

 

The fix... taking on board everyones comments... I found the the MS "idle advance settings" werent enable. So I enbled it so I got a fixed idle advance of 8 degrees. With a bit of tweaking to fuel map and idle screw it produced the nice 800rpm idle!

 

 

I'm a happy camper for the moment! And with this lower idle I might be able to get the automatic idle valve control working now! but I'll hold fire on that for the moment.

 

Mad