Bulvot

You custom wrote your own firmware and software interface? You didn't use TunerStudio and the firmware made for the ECU?

928NOOBIE

So making me wonder now if anyone has done this. I am thinking to make it easy to route it through the inside of the car...8ga tinned copper OFC with outside wire loom jacket. I could get another lid and do the drilling and keep the orig. Routing even a 4ga through the interior would be a non-event compared to trying to route it outside....hell I might even go nuts and spring for a fuse! On a major power lead! heresy!!!

The Forgotten On

It's definitely easy to route through the inside of the car. Just snake it along with the rear harness under the 1/4 panel on the passenger side.

It ends right there in the footwell with factory hold downs for the cables too...

Bulvot

For those that want to retain the stock MAF, here's a handy voltage divider calculator to get the stock MAF output into the standard 0-5v range:

https://www.digikey.com/en/resources...oltage-divider

For example, a 1:3 resistor ratio (e.g. R1=100 R2=300) will bring the stock MAF into the right voltage range to cover the entire range of the stock MAF (which includes the "Extended" range of the SuperMAF). Obviously, do your own calculations and research, but it's very doable. Making it entirely feasible to make a plug-and-play aftermarket ECU solution that does not require replacing the MAF, TPS or any changes under the hood or to the wiring. While still supporting upgrades or aftermarket replacements of those components.

928NOOBIE

I did some rudimentary poking around and to be safe at a 50 amp pull lets say generous 20 feet a 6 ga lead is probably what I'm going to run with. May sound like overkill but to me is taking into account possible future deterioration of current flow from aging. Still looking at tinned copper OFC..permanent installation.

I have the link from SKPyle for Boat Wire and may get the cable from there and get ends from a local electronics supply store ...every time I go in there about 10 projects hit my mind and its tough to walk out with what was on my small list....

Dinsdale Piranha

First off, I'm not a computer guy but I did build the car. My tuner is, thankfully.
We did use Tuner Studio. It was the crazy Toyota v12 programming that I was referring too. VVTI, ACIS intake, 4 knock sensors, 2 crank sensors.

Bulvot

Yes, the MegaSquirt has a lot of built in support for things. VVT, knock, dual crank (or crank plus cam), PWM tables to manage adjustable intakes/pumps/fans, etc. And the Pro Ultimate version has even more inputs and outputs. It's pretty wild what you can do with them!


For those who want to use the factory speed sensor from the differential (or the output from the speedometer to the cruise control for those with a digital dash)...

The current firmware configuration file limits the sampling interval to 50ms. Which is way too short for our factory reed switch sensors (or the speedometer output to the cruise control if you have a digital dash). You can manually edit the mainController.ini file to update the vss_sample_int to this:

vss_samp_int = scalar, U16, 568, "ms", 0.05, 0, 10, 500, 2

Which allows you to set the sample interval in TS to as high as 500ms. You can put in a higher number in the ini file if you need to. I haven't finished road testing to find the minimum sampling interval that will work, but 500 definitely gave me an accurate speed input.

928NOOBIE

Delete

Bulvot

Anyway, back to the MegaSquirt conversion...


I've had a few more chances to work on the "cold" start tuning. I put cold in quotes because the coolest the car has gotten in the last few weeks is about 70 degrees. I won't be able to test colder temperatures until the winter.

I configured the spark to begin on the third potential firing after it sees the missing tooth on the flywheel signal ring. With correct priming and cranking pulse, it catches in about 0.2 seconds from first turning the key to the start position. A massive improvement over the multiple compression strokes required to start it when stock. The main takeaway is that it needed smaller cranking pulses than the stock ECU was giving it. And the priming pulse is critical to getting the instant start, which the stock ECU doesn't provide.

It's a minor thing in the big picture, but also very satisfying.

The knock sensing continues to work very well. Seeing the noise, via the knock signal, of each individual cylinder firing in turn is very enlightening.

Going with CAN WBO2 sensors has worked out really well. They are fast, stable and accurate. Practically plug and play without worrying about calibrations or quality of connections affecting the signal.

I'm past the live tuning phase. From here on, it will just be analysis of the flash card logs that the ECU makes. Mostly to push the envelope a little more on the ignition map.

The next significant component for me is to install the relay box that I built. This will control the oil radiator fans, the AC compressor clutch, and the main radiator fans auxiliary trigger.

Start to finish, it's been a pretty quick and smooth transition. I wouldn't hesitate to do it again. In fact, we plan to use the MegaSquirt on our next car build.

Graham Bates

I have the idle air control valve add-on kit for my Microsquirt and have the GM stepper motor valve in my GM throttle body but found it troublesome so it's just unplugged. Going from mechanical injection where the routine for starting is to just dump fuel into the system from an extra injector to modern injectors and full EFI makes the 928 ridiculously easy to start. I just use the warm-up enrichment for starts and warm-up. It's the middle of winter here but does not get really cold. A few early mornings starts and the use of the auto set up in Tunerstudio for WUE and that's it. The 928 is very easy to start.

Bulvot

Your version doesn't have cranking pulses or priming pulses? What firmware are you on?

Graham Bates

Sure does. MS2/Extra 3.4.3

Bulvot

My current dash:

Bulvot

Attached is the current tune. It's pretty much dialed in, but I need to push the ignition map a bit and find the limits under boost. The VE and ignition maps won't directly apply to most people, but the rest of the settings could be useful. And there are a lot of them!

Lizard928

Graham Bates,
All 928s that were not CIS have a wire directly from the battery to the fuse panel that supplies power to the computers, injectors, and fuel pump so that they do not get too low of voltage during cranking.

Bulvot,
Looks great man! Curious if you just cut and spliced to the original harness, or if you made a new harness? Have you stuck with the stock ignition system or switched to COP? If you did not switch to COP you should. The difference is very noticeable.