Variable Valve Timing - Is it worth adding?
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Variable Valve Timing - Is it worth adding?
I've got my head apart, and I'm thinking about adding VVT. Probably setup to run off an RPM switch set at the max boost point.
The way our heads are setup, only the intake cam is variable. I'm curious as to how much of a difference it will actually make.....
Anybody know what the effects on hp/torque are by advancing/retarding just the intake cam?
The way our heads are setup, only the intake cam is variable. I'm curious as to how much of a difference it will actually make.....
Anybody know what the effects on hp/torque are by advancing/retarding just the intake cam?
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In TT's case it adds about 10% low-end torque with less in the mid range. Top end power stays...
just about the same if I'm not mistaken. I'm not certain on this but I think after a certain point in the rev band you can get a stronger top end by varying the exhaust cam phasing and lift relative to the intake cam instead... keeping the exhaust valve closed longer giving the gases a little more time to expand and transfer the energy to mechanical work.
Regarding the vvt, one of the guys on our forum has been looking into it for a while and I think he's made good strides in determining how it can be made to work... but it is still work in progress.
Adding the hardware is trivial but there are a couple of unknowns on the programming side... Not sure if ECU comes preprogrammed with the phase vs load vs etc. map and two if it does, how would you go about turning it ON after having installed the hardware and recompiling the code to make it run reliably. I can't imagine having to make a cam phase vs. load map from scratch without detailed analytical models of the combustion process in combination with empirical testing and tweaking. It would be one heck of an achievement if it could be made to work though
Regarding the vvt, one of the guys on our forum has been looking into it for a while and I think he's made good strides in determining how it can be made to work... but it is still work in progress.
Adding the hardware is trivial but there are a couple of unknowns on the programming side... Not sure if ECU comes preprogrammed with the phase vs load vs etc. map and two if it does, how would you go about turning it ON after having installed the hardware and recompiling the code to make it run reliably. I can't imagine having to make a cam phase vs. load map from scratch without detailed analytical models of the combustion process in combination with empirical testing and tweaking. It would be one heck of an achievement if it could be made to work though
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I was just thinking of triggering it with an external switch....
I don't think the non-DBW cars have the ability (or the extra output) to control the VVT.
I could create a small circuit that has an RPM sensor and a TPS input. Maybe switching it halfway at 3000 RPM and 1/2 throttle, and full-on at 4000 RPM and 3/4 throttle or something similar.
I'd have to get my hands on the VVT solenoid to find out what voltage corresponds to what intake degree change.
I could create a small circuit that has an RPM sensor and a TPS input. Maybe switching it halfway at 3000 RPM and 1/2 throttle, and full-on at 4000 RPM and 3/4 throttle or something similar.
I'd have to get my hands on the VVT solenoid to find out what voltage corresponds to what intake degree change.
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Don't know if ecu has aux output to control phasing for non-dbw cars...
You could probably tap off the crank gear tooth speed sensor, throttle position sensor, MAP sensor and temperature to calculate mass flow in real time and use commanded load and mass flow as the variables for advancing or retarding the cam...too complicated to do in my opinion. It'll take too much time and money and the end results maybe iffy at best.
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Re: Variable Valve Timing - Is it worth adding?
the new engines in the uk have the vvt, there's a small eletric motor on top of the engine on righthand side, it seems to come in around 4000rpm, you can feel a jump in power and torque
dave
dave
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