Chiburbian

iTrader: (1)

So, I decided to do some testing the other day in hopes of perhaps increasing the Megasquirt's ability to accurately control my boost levels.

I took my airbrush air compressor and put about 14psi through it into my three port EBC solenoid.

From there I started off with 0% PWM and slowly increased the duty cycle in the test mode until I saw some movement of my actuator arm. I continued to raise the duty cycle until the wastegate went full open.

Since I am telling this from memory I may have my order of operations incorrect but what I noticed seemed a little strange, but basically I only have about a ten to fifteen percent change in duty cycle between chattering wastegate actuator and fully open wastegate.

Obviously in a running engine there will be exhaust gasses pressing against the wastegate, but it seems like a really small window of duty cycles.

Does this sound correct, or does it appear that my EBC is failing? OR, was my test pointless and it told me nothing?

Ted75zcar

iTrader: (2)

MS2 or MS3? I think the changed the flyback circuit in MS3 which should improve the dynamic range significantly. I characterized a bunch of this stuff, some of the reaults are posted here:

https://www.miataturbo.net/build-thr...5/#post1452937

bottom line is, with MS2 those numbers dont sound too far off to me.

Chiburbian

iTrader: (1)

MSpnpPro

Ted75zcar

iTrader: (2)

DIY would have to confirm that they changed the solenoid driver circuit between MS2 and the Pro, but what you are describing still doesn't seem too out of line to me. Here are a couple of plots that I have on this machine from some older data. I have fancier MATLAB stuff on another machine, but am too lazy to fire it up. These plots are pretty crappy, but here is what you are looking at. In the first one, you are looking at the wastegate position on a Turbosmart Ultragate38 with what looks like an 11psi spring. The y-axis is the wastegate displacement divided by the total wastgate displacement * 100 (relative WG position in %). The x-axis is the lower wastegate volume pressure minus the dome pressure in psi (WG pressure). Notice that the WG transitions through the entire travel range in ~ 6psi, or ~ 40kpa.

The second plot is the pressure on the outlet port of a common 3 port solenoid (might even have been the DIY IR solenoid) vs the commanded 8-bit pwm code. The x-axis is the commanded code, the y is the outlet pressure. See how the relative outlet pressure transitions from 0 kpa to 120 kpa in only ~ 50 codes? The 50 codes represents ~ 20% duty-cycle change. Furthermore, 40 kpa is only 1/3 of that 120 kpa.

Others may have more direct application feedback on this (18psi), but from my bench results, this doesn't seem crazy to me.

Chiburbian

iTrader: (1)

Ok. Just trying to idiot check myself. I bought a spare to keep on hand should it fail in the future however. Especially on the day I bring it to the dyno...