Megasquirt owners thread

[StanTheMan]

For the NA 6 the options are E30 or VL commodore. There probably others but they are 2 of which I've done some reading on

[Red_Bullet]

You would need to get wiring to it from the ECU too, +5, signal GND and TPS. More wires!! Always more wires......

I just found this in the manual also: Particuarly "If the TPS input is not used, this wire should be connected to sensor ground"

Throttle position sensor
The throttle position sensors used on most cars are potentiometer or variable resistance types, which put out a
voltage that increases as the throttle opens. The easiest way to check a TPS is to unplug it and put an ohmmeter
on its pins. Observe the resistance as the throttle opens and closes. Each pair of pins will behave differently:
The resistance between the VREF and ground pins will remain constant. The resistance between the ground
and signal pins will be low with the throttle closed and high with the throttle wide open. The resistance between
the VREF and signal pins will be high with the throttle closed and low with the throttle wide open.
If your sensor behaves like this, it will be pretty straightforward to connect it to the MS3Pro.
If the resistance jumps from infinite (or near infinite) to near zero, you have a switch type throttle position sensor,
or possibly a seriously defective potentiometer type TPS. These do not provide very much information that MS3Pro
needs, as it can tell if you are at idle or full throttle by the MAP sensor information. You can still use MAP based
acceleration enrichment. If the TPS input is not used, this wire should be connected to sensor ground.

[Cus]

You don't need to rewire the car for the VL TPS, you can crack open the TPS and rewire that instead

Stolen from another thread on here; if you click the pictures you get a description of what's going on / what to do.
I didn't 3D print a bracket, a strip of 2" aluminum from Bunnings Race Supplies works perfectly fine.
https://plus.google.com/u/0/photos/116833011412061185382/albums/5949309642233581457

I'm currently in a low-mx5-density area, I should go and buy all of the VL TPSs they have around here....
Don't get the ebay ones, they're highway robbery, under $30 is a decent price for a 2nd hand, 20-something-year-old part. $120 is definitely not.

[StanTheMan]

Ohhh Ok I was just looking at an BMW E30 one for $138..... I would assume it new.
https://automotivesuperstore.com.au/bosch-0-280-120-321
I guess for $100 its worth diving in head first for a bit of modding to make the VL one fit. I'm hopeless when it comes to doing stuff ;like that as well as electronic stuff....

[Red_Bullet]

I guess that maybe other Mazdas from the era would most likely use the same TPS

Here is something I found online, this is a replacement for the 1994 1.8 TPS, don't know whether it would fit the Throttle body on a 1.6 though. Expensive too!
http://www.wellsve.com/custom_searches/showpinoutdiagram.php?partno=TPS406

[Cus]

I did the rounds here in Cooma, one TPS to be had for $33 (edit: found a second one for $88 )

The TPS on an R31 Skyline looks like it will be identical, I had a squiz at one in situ while I was window shopping, same plugs, same size, same engine attached to it!

[Cus]

While I was on holidays, I took the laptop, you know, for the megasquirtin'

Logs of the drive up and over the top of the snowies, because ... why not? Barometric pressure (ie; altitude) on the right side. An N/A 1.6 is increddibly sluggish with 90kPa of atmosphere...


I managed to get my VSS / Gear detection dialed in exactly, previously it wouldn't detect 5th gear, and after changing the diff the reported speed wasn't consistent with the actual speed. An hour of driving around the middle of nowhere sorted that out.

What I couldn't get sorted was the accel enrichment.



I managed to get most the stumble out of it (left-spike on the tables on the right at high MAP) - but what I couldn't do was to stop it from maxing out fully-rich without spiking fully-lean first. I had a theory about the %WOT table, but 30 seconds of fiddling with it didn't work as I'd expected, so I gave up and went back to just being on holidays

Here's the test procedure for testing and adjusting the stock TPS, just in case someone ever wants it. As already discussed the stock TPS is all but useless on a MS install.

(Heaps Big)

[StanTheMan]

So Ive taken the dive on E85.

I read somewhere the master & commander mentioned something about getting close to 90% Duty Cycle...to then tread carefully. Either increase pressure or upgrade The injectors.

I'm getting to 84.6%

which isn't exactly 90% but its not far off.

RPM was at 6508
Map at 93kpa
AFR was exactly spot on at that moment at 13.2:1

The question is is the 84.9 close enough to 90% to warrant worrying about upgrading the injectors?

here is the log.

Duty Cycle 2017-03-20 14.22.03.png

[datfreak]

So Ive taken the dive on E85.

I ran e85 on my megasquirted non boosted na6 for awhile, I remember the duty cycle was high (around 90%) at red line, but as e85 is a cooler/safer fuel I wasn't worried about a small margin. A turbo car would be very different tho.

I didn't upgrade my pump and fuel lines to e85 compatible stuff and after a month I had stuffed 2 injectors (stuck open- bad idle afrs) and the plastic strainer in the fuel tank got so blocked with black rubbery crap, I got bad leanouts over 4000 rpm.
I bought new injectors -600cc supercharged ford mustang ones, a new pump, new filter strainer, new inline filter and went back to 98 and havnt had a problem since.

I hope you have better luck then I did with e85. It did run nice on it when all was well tho.

[Cus]

I'm getting to 84.6%

Given the DC starts to drop off 500RPM before you actually start to drop RPM, I'd say you're getting close to touble. (DC should go up with RPM/Air Intake, unless you started to roll out of the throttle towards redline)
If you get down to sea level and have 100kPa MAP at 7200, I'd say you'll be well into the Danger Zone.

A quick googlin' has a page on the rx7club forums where they've decided more than 80% is bad because injectors spend too long "on" and heat up and fail early, as well as a graph where one particular brand of injector becomes less linear above 70% - sooooOOOoOOoooo.... I'd say upgrading injectors isn't a bad idea if you can

I bought new injectors -600cc supercharged ford mustang ones, a new pump, new filter strainer, new inline filter and went back to 98 and havnt had a problem since.

Theory questions: Would changing these first make a difference to the outcome (plus maybe cleaning the tank), or did they get stuck from too much DC?


I'm pretty sure these are the injectors datfreak was referring to:
http://www.flowforceinjectors.com/products/ff610-pnp-flow-matched-injector-kit-miata

[StanTheMan]

What's Dc?

Edit. Duhhhhh prolly bee staring at too many data logs

[NitroDann]

The question is is the 84.9 close enough to 90% to warrant worrying about upgrading the injectors?

Nope.

[StanTheMan]

Ok cheers

[StanTheMan]

Ok cheers

When you do one of Those duty cycles Map x rpm & AFR plot graphs it really doesn't spend a huge amount of time up there.

Anyway..... I think I'll worry about the filter first & fuel lines

[datfreak]

Theory questions: Would changing these first make a difference to the outcome (plus maybe cleaning the tank), or did they get stuck from too much DC?

I doubt it was too much DC directly - but it is possible as these are nearly 30yr old injectors.
At the time I believed it was the e85 dissolving a little of the old fuel hose linings and gumming up the injectors, perhaps post filter - but that was just a theory.
If I did it again i'd at least get e85 fuel hose and a new filter. The pump may not have been needed, but I bought a e85 one to be sure.