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Cold start ethanol

Ethanol & Flex Fuel Tuning

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Discussion and questions related to the course Ethanol & Flex Fuel Tuning

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Hi all

i recently brought a track/drift car which runs on e85. Each time I start the car I have to crank it at least 3 times for roughly 5-6sec each time before it fires. The the next crank it runs roughly before idling how it should. I have been messing around with the prime pulse numbers but would like to know what numbers people are seeing here for the e85 tuned cars. I have got it too 2 cranks to fire but unsure if this is the correct method. I also noticed the fuel density is set to the standard petrol of 737 and wondering if there’s much difference in e85 and would this be causing any issues aswell.

What ecu? Likely needs a lot more cranking enrichment at lower temperatures. Try adding another 50% and see what it does. Pre-prime pulse isn't essential in most cases and isn't where I'd make large changes to fix other problems.

Running a haltech elite 2000 is that a setting in this ecu?

Okay, so I was referring to "pre" prime pulse, which is a Link setting.. disregard.

Try adding another 50% to "cranking" under fuel tuning. Cold start initial firing is something you just need to have a play around with by trial and error, make large changes in one direction and see if it's better or worse. Generally you need close to double the cranking enrichment on E85 compared to 98 at cold temperatures.

Pure ethanol is not getting ignated well below 11 degrees C. When it's mixed with 10-15 percent of gasoline the cold start should be better as long as the real proportion between ethanol and gasoline is correct. However sometimes it still might be an issue depending on particular gasoline properties. In that case usually a slight increase in first fuel injector pulse width and cranking fuel enrichment decay time solve the problem.

The basic problem is that ethanol doesn't vapourise readily at lower temperatures, as petrol does, this means it can 'drop out' into liquid droplets which are much harder to ignite and burn less easily and, in bad cases, almost entirely condense out on the port walls.

Depending on your setup, possible things to help are increasing the plug gap - needs a GOOD ignition setup, though, using injectors that have finer nozzles to help break up the fuel into a mist, and running more fuel pressure which may also help break the droplets up.

If you can increase the cranking speed, that may help as the higher air velocity may help keep the fuel in suspension - a good place to start is stripping the starter and cleaning the commutator and brushes with some fine W&D and brake-clean to rinse off, and lubricating the bearings and pivots with a grease and oil mix. You can pick up 100rpm, or more, with that simple job. I assume you charge the battery as part of your preparation for the event, anyway

Thanks all

@gord it has a bran new battery in at the moment but being in the boot there is a volt drop I am also trying to rectify at the moment aswell. I have made some tweaks to the cranking fuel and prime pulse and it now fires on the second crank and idles so I believe I’m getting some where.

trying to upload pictures of the adjustments but dose not seem to be working

That sounds like solid progress. Keep it up and you'll have it sorted soon.

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