LeoNA

Reducing the weight of the assembly will raise the ceiling for a given open pressure. The stiffer the spring the more important it is to set the seat pressure. Most shops do not have that ability or patience. SUB's, Ti retainers and reduced stem valves all save weight which reduces the inertia. In a non-interference application valve float only results in a loss of power which might be offset a little by the lower pressure/lower parasitic loss. The increase from 7k to 8krpm is only 8hz or 14%. For that reason when I did my head I went with the lighter doubles. I'm only spinning to 7400rpm but with 12psi.

muoto

Is anyone else having problem with heavy double springs and VVT actuator? After switching those I find difficult to tune it to follow the vvt target angle. I run MaxxEcu

DNMakinson

iTrader: (3)

There was a thread recently, but I cannot find it. I think that @Ted75zcar was one of the contributors.

Ted75zcar

iTrader: (2)

I think it as a thread about Haltech or something. I now recommend the BP4W for applications using ST heavy doubles.

The summary: VVT is possible with heavy doubles, but is right on the edge of the phasor capabilities. The hot oil hold duty is frequently near 80% which is at the extent of the dynamic range of the VVT control. Additionally, the control resolution shrinks to only a few percent, which makes control VERY sensitive to PID coefficients, especially P. Furthermore, the timer resolution in the ECU results in only a handful of valid dutycycle positions. Finally, operation at the extreme edge of the dutycycle range results in a very assymetric/non-linear plant, so commands to increase advance are very different than commands to decrease advance.

All-in-all not worth it.

deezums

iTrader: (3)

MS3 can't control VVT 100% on stock valve springs, for the reasons above. I forget looking at MaxxECU, but I think I remember it having variable PID which is miles above MS3. I don't think it shares the limits of MS3's timers either, so resolution shouldn't be a problem.

Either way, even with MS3 you should be able to set it up to work well, just might be an extremely limited range where it works and there's no way to disable it 100% when outside that range.