Light or Heavy Double Supertech Valve Springs
#21
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
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.
Last edited by LeoNA; 02-02-2020 at 11:47 PM.
#23
Retired Mech Design Engr
![](/mt2011/images_td/ranks/supporter1.gif)
iTrader: (3)
Join Date: Jan 2013
Location: Seneca, SC
Posts: 5,011
Total Cats: 859
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
#24
Tweaking Enginerd
![](/mt2011/images_td/ranks/supporter1.gif)
iTrader: (2)
Join Date: Mar 2013
Location: Boulder, CO
Posts: 1,809
Total Cats: 366
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
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.
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.
#25
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
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.
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.
Thread
Thread Starter
Forum
Replies
Last Post
800rs
Miata parts for sale/trade
33
05-15-2021 11:57 PM
psyber_0ptix
Miata parts for sale/trade
13
11-29-2019 12:32 AM
spencer9474
Cars for sale/trade
4
05-14-2018 08:49 PM