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Effect Of Too Much Ignition Timing At Idle?

Rolls

By Rolls,
in Engines & Forced Induction

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Rolls Grand Master

Rolls

Posted
Posted

I was wondering what would happen if your timing was 30 degrees at idle instead of the 15 base degrees?

I had an issue where on cold start the ECU (rb20det r32) would pull timing back to maximum retard making the car horrible to drive in cold weather. Pete from nistune adjusted the cold start ignition trim map to make them all 20s instead of 5 or something to fix my horrible cold start retard that made it undriveable, anyway my idle ignition is 30 degrees now when cold and slowly lowers to 15 degrees.

Now I am chasing around a weird idle problem where sometimes my car idles great and other times terribly and I am just curious what too much ignition timing at idle would do? I don't believe it is the issue but I'd like to just make sure.

I plan to get my own license and tweak things in the near future but for now I want to rule out a mechanical problem.

Would this make it harder for the AAC/ECU to control the idle speed due to more ignition?

Could an admin merge these two topics?

http://www.skylinesaustralia.com/forums/topic/401709-weird-idle-problem/page__pid__6399112__st__40#entry6399112

Also how does the nissan ECU control idle speed, as I unplugged my AAC and there was no change in idle speed, is it done via ignition/injector pulse or a combination of all 3?

Thanks.

GTSBoy Grand Master

GTSBoy

Posted
Posted

Idle speed if ONLY controlled by the AAC. It is of course AFFECTED by timing and mixture, but the only deliberate control is from AAC opening and closing. If you can pull yours without it affecting idle at all, then it is probably not working at all. And in fact, this would be one of the reasons for you having a crappy idle.

rob82 Mentor

rob82

Posted
Posted

Idle speed if ONLY controlled by the AAC. It is of course AFFECTED by timing and mixture, but the only deliberate control is from AAC opening and closing. If you can pull yours without it affecting idle at all, then it is probably not working at all. And in fact, this would be one of the reasons for you having a crappy idle.

Could just mean that it's close to the desired idle speed. If you increase the commanded idle speed you should see the aac duty increase.

Good luck finding the cold start retard - I think it's a static number in some ecu's.

ARTZ Grand Master

ARTZ

Posted
Posted

My AAC has been playing funny buggers too..has been cleaned..

If it's plugged in,(brown plug,purple is just ac isn't it?) it starts and idles fine, then soon as I drive it and stop, idle will bounce between 1500-2000...

Unplug it and idles (about 900rpm) and runs fine but of course now cold start is no good.. Have been just plugging it back in when cold to start it, which of course is annoying..

So quite obviously an AAC issue..not sure if it's mechanical or electric though..

Also not sure is it worth replacing AAC or just block it off and tune for cold start accordingly, or even considering just putting a switch inline to turn it off and on as needed..

I know it Probably doesn't help you much Rolls..just thought I'd throw it in here.. :)

GTScotT Grand Master

GTScotT

Posted
Posted

Mine originally had the same symptoms as yours ARTZ, Jez was able to play with some idle settings to fix it.

Later when I changed cams it came back.

I now leave the AAC unplugged and touch the throttle as I turn the key. Once its on (even when cold) it runs fine. It is annoying though, the car should run like magic (never has). Ill get all that fixed when the new motor is finished.

ARTZ Grand Master

ARTZ

Posted
Posted

If I try to start cold ( it has been very cold here lately) with it unplugged it won't idle..If I give it a heap of gas when I start it it may keep running..but starting at 3000rpm isn't a great idea...

It does run like magic if I plug it in and start it and it runs like magic when I unplug it and drive it..def something wrong with need another AAC to try, or just piss it off all together..

Rolls Grand Master

Rolls

Posted
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Posted

Good luck finding the cold start retard - I think it's a static number in some ecu's.

Oh Ive already found it, we zerod it all out and my car no longer drives like a sack of shit when cold. It is a 2d map from 0-2800 rpm, was pulling timing back to maximum retard when cold however I think now it is adding timing.

simpletool Mentor

simpletool

Posted
Posted (edited)

Idle speed is controlled by AAC only when hot.

Seems to be controlled with a combo of all 3 when cold (mine runs 35° timing at 20° C coolant for a 1100rpm idle).

For adjusting the idle my screw is about one full turn inside flush - something for you to go on. For cleaning it I found the Nulon upper engine cleaner works GREAT.

Edited by simpletool
rob82 Mentor

rob82

Posted
Posted

Idle speed is controlled by AAC only when hot.

Seems to be controlled with a combo of all 3 when cold (mine runs 35° timing at 20° C coolant for a 1100rpm idle).

For adjusting the idle my screw is about one full turn inside flush - something for you to go on. For cleaning it I found the Nulon upper engine cleaner works GREAT.

R33 are a different story. They have delta rpm ignition control which will add/subtract timing to control the idle speed.

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