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Cold start, cranking fuel table

Practical Standalone Tuning

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1JZ GTE VVTi stock intake, throttle, cams, no IACV, Ecumaster Classic

I have it Idling quite happily when warm. Warm starts aren't an issue either.

When starting it cold, with all settings the way they are, I need 60-70VE% in those lower few sites. With any less, it won't start.

I tried mitigating that by adding fuel in the cranking table. Haven't had success.

Can someone help me out with a formula to calculate how many ms of Injector duration would be 70VE%?

Pulse width would depend on how VE if run through the fuel model in the ECU you're using, but usually includes displacement per cylinder, injector flow, dead time, voltage, fuel pressure, manifold and ambient pressure, coolant and intake air temperature.

60-70% VE is not unreasonable for what it's worth.

There should be a table for tweaking the fuelling Vs coolant (and sometimes air) temp(s) - then when you're happy with that enrichment, you can then work on the cranking.

Doing that way you avoid the case where acceptable cold starting can cause hot start issues due to over-rich cranking mixture.

I played with both those tables. Cranking PW vs CLT and general PW vs CLT enrichment. Unfortunately both are in milliseconds and I wasn't successful. That's why I came here to see if someone smarter than me has a formula to calculate how that translates to VE%

I think it's easier to understand in pulse-width. You can view the log channel "Injector pw" and see what the ECU is commanding and then add/remove with the enrichment tables.

It doesn't really 'translate' into VE, more the other way around. Volumetric efficiency is a calculation of air mass, that gives us fuel requirements and using the injector calibration data the ecu calculates a pulsewidth to deliver the desired fuel. VE doesn't really change much with a cold engine, but the fuel requirement does.

VE can be calculated using engine displacement. This is well covered in HP's Engine tuning fundamentals course and I'd recommend it if you haven't taken it yet.

Without an IACV you're likely always going to need to nurse the engine for the first few minutes of running when cold. I'd advise not getting too far down the rabbit hole here, you want the VE table to be tuned when the engine is up to operating temp and use the enrichments to get it there once cold.

What firmware are you using? latest is 1.222 and I see a Cranking fuel table 2D which is CLT based and in PW, and a CLT enrichment table (which applies to the entire VE table, not cranking fuel) in percentage of the VE table.

There's setting in parameters called 'cranking threshold' and this is where the ECU changes between tables. This is visible in the engine state parameter.

I have cranking threshold at 450. Cranking around 360.

In the cranking fuel table I tried even doubling PW ms to no avail. Which is why I came here to see if a simple math equation could tell me how much exactly I need.

Don't remember the CLT enrichment thought. Must have another look later today. Under which tab /group do I look for it?

As Tyson said, you can see the actual injector PW in the ECU Master. In the left menu tree, click "Log" and choose "Fueling". You will also see some more channel that can help troubleshooting fueling issues. Also, the "Enrichment" log data will help.

According the the EMU manual, the VE table isn't used during cranking. Only when the cranking threshold is exceeded that the ECU will look at the VE table.

The startup strategy is quite simple. The cranking table, prime pulse table and other correction table mentionned in the "engine start" tab will be used below the cranking threshold. Once exceeded, it will use the VE table, with the warm-up enrichment table and the afterstart table (called ASE table). The last two I mentionned are correction or multiplier tables : 100% means no corrections, and are located in the "enrichment" tab in the menu tree on the left.

If it cranks and doesn't fire up, you need to adjust the tables in the "engine start" tab in the menu tree on the left. If it fires up and quickly dies, it's probably the afterstart table that need to be adjusted. Then when the afterstart enrichment is gone, you can adjust the warm up enrichment so your engine is feeling happy. Trying to tune the warmup enrichment when the afterstart is still active will make it harder. There is no fixed answer to what AFR to target in the cranking/afterstart/warm up stage, as long as the engine is happy, and you are not fouling the plugs, this is fine.

Finally, as it was said already, running no IACV will make things even more complicated. You might need to give it a bit of throttle to help start it. PowerHouse Racing makes a nice kit to run a Ford IACV which is PWM so it only used 1x AUX Output.


Hope it helps,


Am I understanding correctly that ASE and Warmup enrichment DO NOT overlap?

You broke this down so nicely, HPA should hire you. Thanks.

As for the IACV, thank you for the recommendation. I want to press on like this. I have a few ideas to look into still.

Just arrived at the shop, I will apply all this shortly.

Haha thank you for the kind word! ECU Master are ECUs I'm pretty familliar with haha!

My understanding is that ASE and Warmup will be in effect at the same time. So that's why you want to wait until one is gone to adjust the other so you don't end up chasing your tail.

ASE is very short, the duration is defined in engine cycles in "Enrichement" tab, "Afterstart".

Confirming that ASE and Warmup ARE in effect at the same time.

Cranking fuel is incredibly finicky. Warmed up, 0.1ms makes a difference. Never would have thought.

I am closer and closer to installing an IACV, though that wouldn't give me this unique opportunity to waste fuel, time and nerves.

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