Outer Limits 4x4 Board

Hello,

Just wondering if anyone might know roughly what the mechanical advance curve (no vacuum) is on a correctly tuned TB42? ie 10 degrees @ 650rpm, 12 @ 1000, 20 @ 2000 ....

I've had a programable ecu running my spark for a while now but have still to tune it properly, one day I might get it on a dyno. It's running not too bad but I'd like to compare it to what a stock dizzy should be. I should've checked the dizzy with a timing light before I pulled it out... next time

Thanks
Rob

gday rob how r u?

4.2 carby motor should be 10 deg @ idle- 10-12 at 2800 rpm

and 4.2 efi should be 10@idle + or - 1

hope that helps you out mate

I'm well thanks.

Thanks for your reply, I don't quite understand what the advance is at 2800rpm. At the moment I'm running about 30 degrees total advance at 3000rpm & no vacuum (Wide open throttle).

Thanks again

its what i got out of the book. being around mechanics all my life. and me or dad didnt understand it either. but i think it means it advances to 12 at 2800 rpm

Peak power on mine was at 27 degrees total timing, on premium, it didn't ping until 30 degrees though. I had 15 degrees initial and ran 39 degrees at light throttle. It would ping on regular unleaded at low rpm high load with this curve. Full advance was at 3000 rpm.

Joel

Thanks Joel

I've reprogrammed similar to what your settings are and it does feel much better. I'm running LPG which should be fairly close to Premium.

I've got
10 degrees @ 650 rpm
14 @ 1000
17 @ 1500
20 @ 2000
24 @ 2500
27 @ 3000

and maxing out at 39 degrees under light throttle.

You start at 15 degrees, is that at idle ie 650rpm?

Yes I suggest to people running duel fuel to use Premium as the timing requirement to LPG is very similar and improvements can be acheived on both fuels.
I did some stuff around idle to make it more stall resistant, its a matter of setting the timing so that it is low enough at no load that when the load comes on the timing advances, so it might idle at no load at 7 degrees but when the vacuum drops as you engauge the clutch more timing goes in, up to 20 for instance as this make the engine more stall resistant.

Joel

In a TB42e does the ECU control the timing throughout the rev range (besides base)? Can it be altered at all if you run lpg like me?

The distributer is fixed in a TB42e so the ECU must be doing all the timing calculations. All we do is set the initial (i guess this is called base too) timing to 10 degrees by rotating it. I know on some other factory ecu's that have been "hacked" you can get in and modify the tables, I've not heard of the TB42e's computer being modified though.

Rob