MoTeC Global Forum

Hello everyone Happy New Year!
we have a 4 cylinder 16v race engine with radical cams and we believe fuel timing may be an issue for smooth accelaration and proper idle; is 320 BTDC apropiate? any suggestions.
Best regards

Diego

Hello Diego,
Yes about 320 would be a good start but I think the fact that the cams are big would be more of a problem for the idle and acceleration from low RPM.

On a car with normal cam shafts it is unlikely that you could make the idle really bad by getting the injection timing completely wrong but it definitely makes things nicer if you get it right. I find 320 to 420 degrees works for most engines I have seen but again, it will depend on your particular engine/cams.

Starting the engine can be greatly affected by the injection timing but yes, the cams can effect this too. Normally we would experiment with the injection timing to get the quickest start and then move it around at idle until the lambda reading was richest (for a set injector pulse width). Past this you are only really going to see the effect of the injection timing by running the engine on the dyno.

Hint: Avoid big changes from site to site in your injection timing table as this can cause drivability problems.