mapping issue

[julians]

Engine is 2.0 zetec on Throttle bodies, moderate cams and a dta 3d ecu

 

Engine idles fine until you turn the lights on at which point it starts to slow down and eventually will stall. If I tinker with the map I can get the engine to idle fine with the lights on (by upping the fuelling), however when I turn the lights off, the engine idles way too fast.

 

Whats the answer for this catch 22 situation? Anyone got any pointers, how does ignition timing affect things like idle speed.

 

All pointers gratefully received.

 

BTW , I have no idle control valve.

[Swiss_Tony]

It may be worth having a look at the ignition map at idle and zero throttle.

A lot of vehicles use very little advance at idle which can help.

Also double check the throttle stops have been set correctly.

 

 

 

James

Su77on Se7ens

 

[Peter Carmichael]

If the DTA ECU doesn't have active idle control using advance, you can build a gentle ramp up of fuel and a fairly abrupt ramp up of advance in the last few ignition and fuel settings so that any slowing down just takes the engine to a rock solid recovery position. The next thing to worry about is starting as you really don't want the engine cranking at anything much over 5 degrees of advance.

 

Switching the lights on will intorduce a mechanical load and will also drop the voltage. It is just possible that the voltage is affecting the injected fuel at idle but most ECUs have voltage compensation.

 

I have never worked with a DTA, so I don't know the capabilities.

[julians]

I know absolute numbers are probably not too useful unless you know the specific engine , but anyway:-

 

Update - Its at around 6-7 degrees for cranking, and around 19-20 degrees when idling. injectors are firing for about 3.7milliseconds at an idle which will hold if the lights are on.

 

Is that advance figure (ie 19-20 degrees) in the right ball park for idle speed, should it be lower or higher? I did try lowering it, but the engine just stalled, if you lower advance do you need to increase or decrease fuelling accordingly or doesent it make any difference to fuelling.

 

Peter, the version of ecu I have doesent have idle control via advance, so I guess I'll just have to fine tune the map in a similar manner to which you suggest.

 

 

Edited by - julians on 25 Feb 2003 08:59:16