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Discussion Starter · #1 ·
Hello

I have a VVT swapped mk1 with an MS3 ECU and I am looking for some general help with how one would go about safely tuning the cold start and drivability during engine warm up.

The car runs and drives once it's warmed up, but requires a few minutes sat on the drive way before it will run well whilst driving.
To start the car, I need to feather the throttle quite a lot and in cold winter temperatures it's very difficult to start. I've never tuned a car before and I am struggling to find out what I can safely play with etc

Below are my current tables, I assume for to get the car driving better I just need to add values to some of these tables, but I dont know how much by each time and what to change.

I also can't find any settings related to the cranking and adding fuel to make it turn key, I'd really like to get the car driving without needing to feather the throttle.

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Thanks for any help that can be offered, also happy to be taught how to tune for a fee...
 

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Happily expanding the To Do list since 1997
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It sounds like you may have problems both with getting the cold engine to fire up initially (which tends to be cranking fuel pulses) and also with keeping it running until it warms (which includes After Start Enrichment in the first few seconds but after that just Warmup Enrichment).

You can definitely adjust cranking fuel with temperature but my memory's like a sieve these days. I'll take a look later when I can.
Once the engine is turning over at its "run" rpm (which you can also adjust of course) it assumes it's started, so it stops injecting cranking pulses and switches to injecting the amount from the standard fuel map plus the ASE and WUE enhancements. ASE tapers off over a few hundred engine cycles so if you're finding it still needs a bit of throttle after say half a minute then WUE is a good bet for needing adjustment.

I find there's no use in pussyfooting around with small adjustments when you're initially trying to get into the right ballpark so in your position I would probably shove WUE up from e.g. 162% at 0.0°C to something like 250% (and a similar increase for the -10°C and 10°C values) and see if that makes a big difference.

It's worth bearing in mind that it might not just be a fuel thing. It's possible you need to give it more air to start enthusiastically. When it does fire, if it doesn't rev up to somewhere near 1500 before settling down it might be worth adding a bit to the PWM drive to the idle air valve. Again my brain fails to deliver on which settings to look at but I'll have a look later if someone else doesn't leap in.
 

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VVT swapped NA & TD04 turbo NB
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Discussion Starter · #3 ·
It sounds like you may have problems both with getting the cold engine to fire up initially (which tends to be cranking fuel pulses) and also with keeping it running until it warms (which includes After Start Enrichment in the first few seconds but after that just Warmup Enrichment).

You can definitely adjust cranking fuel with temperature but my memory's like a sieve these days. I'll take a look later when I can.
Once the engine is turning over at its "run" rpm (which you can also adjust of course) it assumes it's started, so it stops injecting cranking pulses and switches to injecting the amount from the standard fuel map plus the ASE and WUE enhancements. ASE tapers off over a few hundred engine cycles so if you're finding it still needs a bit of throttle after say half a minute then WUE is a good bet for needing adjustment.

I find there's no use in pussyfooting around with small adjustments when you're initially trying to get into the right ballpark so in your position I would probably shove WUE up from e.g. 162% at 0.0°C to something like 250% (and a similar increase for the -10°C and 10°C values) and see if that makes a big difference.

It's worth bearing in mind that it might not just be a fuel thing. It's possible you need to give it more air to start enthusiastically. When it does fire, if it doesn't rev up to somewhere near 1500 before settling down it might be worth adding a bit to the PWM drive to the idle air valve. Again my brain fails to deliver on which settings to look at but I'll have a look later if someone else doesn't leap in.
Thanks this is helpful even if I don't fully understand it all.
It's been pointed out by a friend that my cranking RPM is 300 and likely too low. What do you think?

EDIT: with regards to idle air, it does indeed fire up to 1500rpm when it catches and begins to taper down from there. Sounds like all of this is relatively simple once I get my head around what I am doing. I would appreciate your further help once you've had a look though as I feel this is going to be a long learning curve, any guidance or further education would be very much beneficial :)
 

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I agree with your friend that 300 rpm is probably too low for cranking rpm. It ought to be set to something comfortably faster than the engine can reach on the starter before it fires. I think mine is around 450 but again I'll need to check.

Like I said above, as soon as it hits cranking rpm the MS3 assumes the engine has started so it stops using the cranking pulses for fuel and cranking PWM setting for the idle air valve, and switches to run on the normal running settings (plus those fuel enhancements).
 

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Discussion Starter · #6 ·
I agree with your friend that 300 rpm is probably too low for cranking rpm. It ought to be set to something comfortably faster than the engine can reach on the starter before it fires. I think mine is around 450 but again I'll need to check.

Like I said above, as soon as it hits cranking rpm the MS3 assumes the engine has started so it stops using the cranking pulses for fuel and cranking PWM setting for the idle air valve, and switches to run on the normal running settings (plus those fuel enhancements).
OK

So I tried just the starter RPM but not the ASE or WUE tables as my battery died, see following video


Seems like it's not even catching, maybe once it hesitated but no way near springing into life.

Shall I add some fuel to the bottom left cell of the VE fuel table?
 

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As Martin said before, it will be your cranking settings that are wrong, leave the rest alone, you will only confuse matters.
Cranking Pulse needs changing, read up on cold start settings.
I know this a appertains to Megasquirt, but the principle is the same
 

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Discussion Starter · #8 ·
As Martin said before, it will be your cranking settings that are wrong, leave the rest alone, you will only confuse matters.
Cranking Pulse needs changing, read up on cold start settings.
I know this a appertains to Megasquirt, but the principle is the same
Thanks so much, I have been looking for a guide like this for ages. This is so incredibly helpful, in fact I think this one quote is possibly the most helpful thing since I started trying to understand cold start tuning

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I completely misread Martin's post and thought I was supposed to be starting at the RPM and enrichment tables. Thank you for this.
 

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Discussion Starter · #11 ·
bit of an update for you all, I set the cranking RPM back to 300 and then adjusted the 7c and 21c cells in the CP% table below. They were at 276 & 242 respectively and now 220 & 200.

I really did just arbitrarily pick those numbers as a first test to see how close I was, and guess what, she fired right up like a modern car.

On subsequent tests where the coolant had warmed ever so slightly it seems that I'll need a little more work, so time to start keeping a spare laptop in the car I guess.

I stuck the 30c cell down from 214 to 200 and helped it fire right up again with no throttle. In all tests (bar the very first one bizarrely) the car was misfiring a lot after starting, but that could be a mixture of me having flooded the engine perhaps or just that I need to work the ASE table a bit, further tests will evidence this.

Will try again later if it's stone cold again :) good progress though.

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Discussion Starter · #12 ·
Well a less positive update today, I tried again with the same settings and did not get the immediate start up like I was expecting, it must have been a lucky fluke

The coolant temperature is currently sat in the 7 degrees cell, I tried playing with the fuelling percentage there from 220% I then tried 230, 240, 250 and then 200. I did one flood clear between 250 and 200.

It cranks a few times, builds RPM up pretty high, tries to catch and stumbles. I'm not really sure what to do next, is it immediately dying because of bad ASE settings?

Also how do I stop my fuel pump continuously priming before the engine is started? I couldn't find where to do that via the manual.
 

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Discussion Starter · #14 ·
ASE only comes into play after the engine has started.
Have you set your required fuel setting?
Have you input your injector sizes?
Check all the basics.
As per previous posts, car works fine in warm weather, it's just never been tuned for cold after being set up. I didn't do the conversion.

And car starts fine when feathering the throttle.
 
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