Help with building your Speeduino, installing it, getting it to run etc.
By scotty dugg
#55507
Hi all,

Second time writing this so hopefully posts this time, I'll keep it short this time.

I've got a Mk1 MX5 1.8 93' plate, that I'm in the process of trying to fit a DIY-EFI CORE4 Speeduino to. Trying to get the car setup to run naturally aspirated before switching to a GT2554R turbo kit, I've got sat waiting to go on.

I've fitted up everything, following the available information I have (for essentially a plug and play kit), but currently can't get the car to start, it's just cranking and nothing else. I'm hooking the car up to a second car during start up attempts to make sure it's got enough juice, as it's been sat a month or two.

Cars got the following:
1.8 VTPS
GM IAT
Stock Coolant Sensor (RX-7_CLT(S4 & S5))
1.8 base map pre-loaded by DIY-EFI prior to shipping
TDC set (+7 Trigger Angle)
Set Required fuel settings (mk1 1.8, with mk2 2.8 injectors (255cc))

I've got all relevant signals working in Tunerstudio when I connect up my laptop.

Currently not sure where I'm going wrong here, I've got spark, fuel and cranking. I can't download the 1.8 basemap on my work laptop (only one I have access to) to try compare and see if I've managed to mess something up.

Would really appreciate some help, I've got the tuner lined up to road tune the car, but I wanted to get it started first (at least).

Tune should be attached.

Cheers,
Scott
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By PSIG
#55525
I don't know if it's your starting issue, but you have a trigger offset of 7°, when most decoders are designed to use zero. No big deal, except you also are using Fixed timing with trigger for cranking, which does not see the Trigger Angle offset. Your cranking timing is 7° different.

Again, not a big deal, but may influence your starting performance until rpm rise above threshold. I would alter your sensor position (most 4Gs can turn the distributor housing) to get 0° Trigger Angle. That will correct both issues, and might help your starting.

You also have unusual injector voltage correction, and no dwell voltage correction, both (especially dwell) can inhibit starting at cranking voltage levels.
By scotty dugg
#56105
PSIG wrote: Thu Feb 24, 2022 4:42 pm I don't know if it's your starting issue, but you have a trigger offset of 7°, when most decoders are designed to use zero. No big deal, except you also are using Fixed timing with trigger for cranking, which does not see the Trigger Angle offset. Your cranking timing is 7° different.

Again, not a big deal, but may influence your starting performance until rpm rise above threshold. I would alter your sensor position (most 4Gs can turn the distributor housing) to get 0° Trigger Angle. That will correct both issues, and might help your starting.

You also have unusual injector voltage correction, and no dwell voltage correction, both (especially dwell) can inhibit starting at cranking voltage levels.
Thanks PSIG, yes I was trying to set the timing offset without being able to start, fixed timings removed and once running the offset was changed to 2°, so now the car and ECU both see 10°.

I've attached the latest tune and a log of it starting (or at least tried to but it won't attach), it doesn't seem to want to start unless the priming pulse width is up at 3.5.

Also regarding the injector voltage correction and dwell voltage correction, I've honestly no idea where to start with that one. Has anyone access to the base maps that could make sure I've got the correct settings to start with?

Just for more info, the car now does start, not first try, it idles fine but the biggest issue I'm facing is getting it to start consistently.
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By scotty dugg
#56306
theonewithin wrote: Mon Mar 21, 2022 10:46 pm Add more cranking enrichment.
Thanks, still no luck so far, I took it up to 180% for the cranking enrichment and it still wouldn't start, but with some throttle it will start, so I pulled some fuel out, down to 140% and it still won't start.

I've tried adjusting IAC PWN Duty and Cranking Duty, as well as the Priming Pulsewidth, is there a limitation on what is considered too high for Priming Pulsewidth?
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By PSIG
#56329
Cold starting uses the tuned tables, with added changes to fuel and spark to compensate for cold temperature effects. So, the first task is to get it running and tune your warm idle and high-idle very well, and smooth the tables above idle up to atmo (~100 kPa) as the foundation for starting, warmup, etc. Search for ways to do this.

As you can imagine, if it's running really well and you shut it down, restarting should be immediate. If the engine cools, then restarting should be immediate with logical changes to fuel and spark appropriate for the temperature. For example, when the engine is cold, fuel does not vaporize as well, and so not as much is available to burn. The "correct" amount of fuel becomes not enough (too lean from optimal).

Random example: Your best warm idle is found to be 14:1. At the current cold engine temperature of x°, only 80% of the fuel can vaporize (different for every fuel), so (1 / 0.8) * 14 = 17.5:1. The numbers aren't actually important, as much as the point that it won't start running on 17.5:1, right? We need to add 20% more burnable fuel (remember, only 80% can burn at this temp), so (1 / 0.8) * 20 = 25% more fuel to have a true 14:1 (the optimal idle value found in tuning) burnable fuel available.

We may have to just blindly add fuel in increments until it tries to run, and then we can determine by comparing calculated fuel AFR versus reported AFR, what the % of fuel vaporization is at this exact temperature and engine speed. This is the basis for most "Warmup Wizards" operation.

So we add fuel for cold start and warmup, reducing added fuel as more of it vaporizes with increasing temperature. As most engines are tuned with idle torque reserve, we may also add timing to the cold-start routine to stabilize the run. Note the point here however, that the correct amount of fuel is established with the warm tune, and changes for cold start and warmup are simply made to return the fuel-air-spark combination to "normal" or optimal combustion. See where this is going?

Unless some very basic settings are reasonably correct in your tune setup, such as injector latency, voltage correction, dwell, dwell protection, etc, it may be quite difficult to find the magic combination that works for your engine. This is why we pound the point of taking time to research or test for setting usable values. ;)
By scotty dugg
#57913
Thanks for your assistance PSIG, in the end there were multiple thins that I had done wrong in both my tune and mechanical setup. Which the tuner was able to rectify and get the car starting well.

The only issue that seems to persist on cold start up, is the revs jumping up to 3.5k for a few seconds before reducing down. on an up to temp start up it starts very OEM.

I've tried removing the cranking IAC PWN Cranking Duty to stop this, but no matter what figures I input the problem doesn't change, which is a bit of a worry with a cold engine revving on start up. I don't want to damage anything, with multiple starts.

Is there anything I might be missing?
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By jonbill
#57921
There is a setting there about actuating the IAC on power on, so its at the right place when you start, have you played with that?

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