Appropriate Wastegate Spring when using EBC?

[flightlead404]

As part of my leveraging features in the Microsquirt I'm using for FCIS I am going to be installing electronic boost control.

Currently I have a Tial F46P wastegate with a .8 bar (large green) spring.

What is a reasonable spring to use with an EBC setup? I was considering .4 bar (small green) spring.

Thoughts?

[dap930]

If your target boost level is .8bar then a .4bar spring would work. If you looking for 1bar or 1.2bar, then the .8bar spring would be fine.

[Jeff NJ]

I have a MBC, but I don't think that matters, and I have a .7 spring and the MBC set for 1.0 bar. Works perfectly.

[jpilcher]

Dennis

Did you ever get the EBC dialled in properly with the MS3?
I ended up removing it from my setup.

Thanks

John

[dos531]

I could not get the electronic boost control on the ms3pro to work well with a .8 bar spring and 1.2 bar target boost. It would either overshoot or underboost, depending on gear, weather etc. I tried open loop and closed loop, but could not get it to perform how I wanted. I switched to a 1 bar spring and now I can control it properly and reliably hit my target boost.

What is your target boost? I would definitely NOT put in a smaller spring.

[993Speedster]

It slightly depends on your ECU's settings/reaction time and how the solenoid is setup (if you're utilizing both sides of the wastegate diaphram... even gate placement and flow) but as everyone said, the more boost you're shooting for in relation to base spring pressure; the harder it is to accurately control. Rule of thumb is definitely no more than double spring pressure unless you're one of those standing mile people using Co2 to control the gate/gates

[flightlead404]

Not really sure on my target boost actually. I have the .8 bar in now and I have no problem with fueling, but I'm going to let the MS control ignition and additionally putting in SC cams and a lightweight clutch package. I think I'll probably be ok at 1.2 bar.

I was thinking a low pressure wastegate spring would allow me to have a "valet mode" with very low boost.

Should I simply leave the current spring in place, at least for testing?

Also, I've read that using a max duty cycle works better than a closed loop target pressure.

[dap930]

John,

Yes, I have MS3 boost control working (1.2bar), but I do have occasions where I get overboost cut(235kpa), usually when the oil very hot (90* summer weather), which I think is due the GTX3071R turbo spooling very quickly during high RPM shifts and boost control can not catch it. I have done a lot of datalogging and have adjusted the boost control solenoid bias table DC to where it does not happen often. I am using a Mac 35A 3 port valve, which I think is too small to quickly vent the wastegate dome. I can not blow freely through the valve(de-energized vent position). I left the muffler off the vent port to reduce any restriction to a minimum. The Porsche wastegate dome/diaphragm is huge compared to other wastegates. So, I am going to install a Mac 36A valve, which has almost twice the flow rate of a Mac 35A and see how that does.

[flightlead404]

Originally Posted by dap930

John,

Yes, I have MS3 boost control working (1.2bar), but I do have occasions where I get overboost cut(235kpa), usually when the oil very hot (90* summer weather), which I think is due the GTX3071R turbo spooling very quickly during high RPM shifts and boost control can not catch it. I have done a lot of datalogging and have adjusted the boost control solenoid bias table DC to where it does not happen often. I am using a Mac 35A 3 port valve, which I think is too small to quickly vent the wastegate dome. I can not blow freely through the valve(de-energized vent position). I left the muffler off the vent port to reduce any restriction to a minimum. The Porsche wastegate dome/diaphragm is huge compared to other wastegates. So, I am going to install a Mac 36A valve, which has almost twice the flow rate of a Mac 35A and see how that does.

I picked up this one from DIYAutoTune and will be using it with a Tial F46P.

['76 911S 3.0]

Rule of thumb when selecting wastegate springs: An auxiliary boost controller (solenoid or needle valve) will net you roughly twice the spring pressure of the wastegate spring. So if you are looking for a specific boost range, select the spring that fits that criterion. For instance, if you want a min boost of 0.5 BAR with a max of 1.0 BAR, then the 0.5 BAR spring will suffice. If you are looking for 1.5 BAR, you will need a min spring of 0.75 BAR. Hopefully that makes sense.

[16Volt]

I put a .5bar in my Tial gate controlled by a HKS boost controller. I am still doing tuning so I have the boost controller shut off so it runs off the spring only. Seems to open dead on, if not a little early. HTH.