Cold Start - Pre Crank Prime and Crank Enrichment Tables

[David Frechette]

EJ25 dyno tuned this summer on E10 (CA 91 Octane) and E98 race ethanol.  Cold start maps were not set due to high temps so base values applied.  The is a multi fuel car, currently with E98 in it.  My attempts to get a good cold start map have been futile and frustrating mostly due experience with E98.  Need help with pre crank and crank enrichment table timing and %'s or any other set up that allow me to get it at least running to fine tune.  I have fiddled with tuning the pre-crank off and on and fuel % cells and all cold start tables.  Engine pops, puffs and barely wants to attempt a start.  Visual on the spark plugs indicates fuel getting there, not sure what would be too much with this concentration of ethanol. 

Any input would be great full.  

Log 2019-11-28 11;43;27 am.llg 9-11-19 DF.pclr

[cj]

Ethanol does need quite a bit more cold enrichment than petrol (sometimes nearly double when you are talking <5C). Looking at your log however, you have 1300cc injectors running at ~12ms, so that should be enough to start, especially for how long you are cranking it.

More likely, I think its to do with your idle/throttle control. I dont see an idle valve anywhere, and your idle control is essentially not set up. You will need to give the car some throttle to get it to fire up when cold, or connect an idle valve of some sort. 

Can you post another log of you trying it with ~10% throttle?

I assume it starts ok when warm, and that it runs ok once warmed up?

[David Frechette]

Cj, thanks for the reply.  You are correct it does idle ok when warm.  I post up another log @ 10% throttle when cranking tomorrow.  Stay tuned.  

[Davidv]

Have found that setting the injector timing to around the 220-240 deg mark (so spraying injector when valves are open) helps on cold starts to reduce how much enrichment you need.

Tested this only with petrol, but had a friend test with E85 and said it made a dramatic difference. As in, cold engine now drivable where previously he had to let it warm up before trying to move it.
 

[David Frechette]

On 11/28/2019 at 4:38 PM, cj said:

Ethanol does need quite a bit more cold enrichment than petrol (sometimes nearly double when you are talking <5C). Looking at your log however, you have 1300cc injectors running at ~12ms, so that should be enough to start, especially for how long you are cranking it.

More likely, I think its to do with your idle/throttle control. I dont see an idle valve anywhere, and your idle control is essentially not set up. You will need to give the car some throttle to get it to fire up when cold, or connect an idle valve of some sort. 

Can you post another log of you trying it with ~10% throttle?

I assume it starts ok when warm, and that it runs ok once warmed up?

Cj, two log files attached.  The 4;40;58 is at various throttle positions.  The second log fie I changed the injector timing.  Same results.  

Log 2019-11-29 4;40;58 pm.llg Log 2019-11-29 4;49;05 Inj Timing 230 BTDC.llg

[Adamw]

I think with engine temps of 10°C and 94% ethanol you are going to struggle with cold start and there will be little you can do from a tune perspective to help.  The vapour pressure of straight ethanol is very low so there will barely be any vapor in the port at that temp no matter how much fuel you dump in, it will just remain as liquid. Somewhere below around 10°C there is not enough vapor produced to support combustion.  This is the reason why pump E85 gets reduced to E60-E70 in winter so there is a little more of the volitile solvents available to create some vapor in the port.

In regions like Brazil etc where they predominantly use straight ethanol it is common to use heated injectors to get around the problem.