I was reading 1 of my old car magazines today, and it had an article in there on the effect of simple, single step variable valve timing on engines.
Now, long story short, they had an example of an AU Ford Falcon XR6. These are a 4 liter, single over head cam, 12 valve engine that used a single step variable valve timing actuator. So just the the Alfa 12V engines, there is no means of adjusting the inlet and exhaust cam centre lines independantly.
The results of unpluging the actuator solenoid, and so not allowing the cam timing to be advanced by the computer at low RPM, was a very significant drop in low RPM torque/power. As much as a 30% reduction. BTW, these things are a very torquey engine for their capacity.
The dyno was measuring wheel speed in km/hr rather than engine speed, but:
At about 54km/hr there was a drop in power from about 72 RWKWs down to about 62 RWKWs.
At 61km/hr power dropped from 82 RWKW down to about 64 RWKW.
I'd guess that the engine management system isn't tuned to give best results when the VVT system isn't working but some of the nambers are pretty major.
So has anybody had the need to play with actual valve timing on a standard cam 12v Alfa, and been able to directly compare results?
Now, long story short, they had an example of an AU Ford Falcon XR6. These are a 4 liter, single over head cam, 12 valve engine that used a single step variable valve timing actuator. So just the the Alfa 12V engines, there is no means of adjusting the inlet and exhaust cam centre lines independantly.
The results of unpluging the actuator solenoid, and so not allowing the cam timing to be advanced by the computer at low RPM, was a very significant drop in low RPM torque/power. As much as a 30% reduction. BTW, these things are a very torquey engine for their capacity.
The dyno was measuring wheel speed in km/hr rather than engine speed, but:
At about 54km/hr there was a drop in power from about 72 RWKWs down to about 62 RWKWs.
At 61km/hr power dropped from 82 RWKW down to about 64 RWKW.
I'd guess that the engine management system isn't tuned to give best results when the VVT system isn't working but some of the nambers are pretty major.
So has anybody had the need to play with actual valve timing on a standard cam 12v Alfa, and been able to directly compare results?
