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Premium Member
86 Veloce
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918 Posts
Discussion Starter #1
Since my rebuild I havent messed with the VVT, I was worried about how it would work with the performance cams and calculating advance with the overlap, etc.
Well, i decided to just wire it as a manual switch in the ****pit and activate it as I please, it just doesnt seem to do anything. Solenoid works, adjusted plunger per CarDisc instructions but I just cant tell that it is doing anything. Before the rebuild it was easy to recognize, engage it while idling and it would run rough. Now it has a really lopey idle anyway due to the cam profile but the VVT doesnt seem to change anything. I can almost talk myself into hearing a slight difference but I'm just not sure. I certainly dont need it for a performance advantage but come smog time I would like to have it operating. Maybe I could just detune the car before I smog it? I really dont care whether it is there or not if I can pass smog next year. There really is not a lot of information on this system.....
 

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14,034 Posts
Regarding intake cam timing, when I played with mine ( non - VVT) on a dyno I found that advancing the intake cam, ie opening and closing earlier made more torque and HP from 3000 to 7000 rpm. The advantage was significant at 3000 and I presume that is better at lower rpm too. The advantage at almost disappeared at 7000 and it could be that a little retard would increase HP above 7000 but that is academic from my point of view. So my motor has the intake advanced as far as it will go while maintaining valve to piston clearance. It could be that retarding the intake - less overlap, will reduce HC emissions.
 

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Premium Member
86 Veloce
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918 Posts
Discussion Starter #3
That is my quandary. I found my max intake cam advance at P/V clearance and subtracted the 14 degrees of VVT advance, that is where I am right now. I do not know if the VVT is working, if I disable it I can advance intake cam timing closer to its maximum. My AFR meter came today so I will be installing that over the next couple of days and get a good idea of fuel mixture over the RPM range. My exhaust cam is already set to its max retard ( with a couple of safety degrees) so I really want to get the intake set optimally. I have ways of tuning my mix on this Bosch set up so I should be able to get close to an optimal mixture. I will post more as I go and probably pick your brain a bit more too, Ed! Thanks....
 
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