ECU mapping vs Cam position tweaking

I had a question about mapping which hopefully someone can help me get my head around. When I had my car mapped at Stealth, Vince said he hadn't tried adjusting the vernier cam on mine but had just set the cam to zero and 'done everything via the map'.

At the time I was just 'OK, fine', but the more I think about this the more it puzzles me. I thought the map gave RPM vs MAP pressure vs Injector cycle and RPM vs MAP pressure vs Ignition timing as the main things that are varied (on the G60 anyway).

Basically I'm struggling to see how advancing or retarding the cam could be done using the ECU map alone as they seem to be 2 very different things to me. Surely advaning or retarding the cam just alters when the valves open or close in relation to the piston and crank movement

I agree, valve timing is a purely mechanical thing on the G, 16v and 12v VR. But, I would suspect that it is possible to achieve good results with the cam at 'zero', with a good map. It may be that, with the experience that Vince has with G60s, adjusting the cam timing would not give any substantial increases in performance, when considering the amount of time involved with doing it. Or indeed that with the cam at zero, the performance would be as good as as it ever could be anyway. Because you only have one stick, adjusting the cam timing would move both inlet and exhaust timing anyway.....








......I think you need 16 valves

Good, that confirms that atleast I have some grasp of whats going on . Agree, it may be that he thought it wasn't going to get any better than zero which was why he didn't change it. I just found it a bit odd thought as 6 degrees before TDC is always thrown around as the ideal setting for a tuned G60, and given I have a vernier, it would have been easy to check while he was doing it. I suppose it will all come down to the cam profile itself as well though. I really must stop worrying about it and just enjoy it....

As above,mechanical valve timing is a seperate thing to anything that can be adjusted electronically.You can't effect the valve timing events electronically in a non VVT system.
I have read that there isn't much to be gained with a vernier for an 8v.
However it would probably be worth experimenting as every engine is different?!??

I did read Berno's comments on dubforce about the gains he made with his.
I'm sure if you went back to Vince or another tuner and said that you wanted to explore this feature on your engine they would oblige you.
Would be interesting to see if you could find a "sweet spot".

It was the thread on Dubforce that reignited my thoughts about this, but then CTW reminded me that Bernos is very different with the high compression system. As you say every one is different and it's really a case of 'suck it and see' I suppose.

Yeah it might be that the cam timing in Berno's engine was adjusted to decrease the dynamic CR, as this can be very different to static CR especially when fudging about with the valve opening profile.

When you say you read '6 degrees for a tuned G60', is that 6 degrees cam timing or 6 degrees ignition advance?

AFAIK it's 6 degrees cam timing, because one of the 1st things I did when I got my G60 years ago was have Darren check it over (this was when I was on my old 1.8l engine). He took the cam cover off, looked at the vernier and went 'yep, thats about right 6 degree before top dead centre'.

this 6 degree number is what is used when setting up the ignition timing.
I used a timing gun on my standard g60.
From cold it started at 20 degrees btdc and quickly dropped down to about 6 degrees at idle.

mrbeige wrote:It may be that, with the experience that Vince has with G60s, adjusting the cam timing would not give any substantial increases in performance, when considering the amount of time involved with doing it. Or indeed that with the cam at zero, the performance would be as good as as it ever could be anyway. Because you only have one stick, adjusting the cam timing would move both inlet and exhaust timing anyway.....

Spot on that man. Vince doesn't do things for the sake of it. He knows what works and what doesn't. He does obviously get things wrong from time to time and when you've known him 10 years, you see that more often than you'd like, but on the whole, he has forced induction and race car prep expertise spanning back many years....

mrbeige wrote:......I think you need 16 valves

Yip, Vince found 10lbft torque across the range tweaking the inlet cam on an old Audi 16V back in the day