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PCM E85 cranking fueling questions

Frosty

Frosty

I Write E85 Stickies
So to preface this... I drive a e85 monster... in the land of -20* mornings.... It always starts but 8 second starts on really bad days do not impress the lady friend. On 30* days it takes less then 2 seconds and on normal warm days its instant so its pretty normal from what I gathered.

So onto the questions. One thing I have noticed with my lq4 maf (and stock) is that the first 4 cells or so are NEVER used once the engine is started. My question is does the pcm actually use the maf during cranking? Because if it does I was considering just bumping those first couple cells up a ways so that starts are a bit more quick in the cold... then as soon as it is firing on all 6 it should be in the normal cells and be happy as a clam... right? Or does the pcm just use the VE table during cranking? I know it takes a second for the hot wire in the maf to get "hot". I suppose if it does use VE I could just fudge the VE table a bit down low to get the same effect. Or maybe there is some crazy hard set cranking fueling that is only modified by the injector size table? Gm has done stranger things on these.

Yes I know this is the wrong way to do this but dammit hptuners wont let me touch all of the tables. Thoughts? Concerns? Food you'd like to pelt me with?
 


e85 isnt even supposed to be able to start in the cold... That being said I have never had much of a starting issue in the cold on most of the cars I have on e85... my fiero hates to start but there are reasons for that.
 
So I have already done the basics discussed in that thread but was hoping someone could tell me if the pcm uses the maf table during cranking? It already always starts I just want it to start even better.
 
frosty said:
So I have already done the basics discussed in that thread but was hoping someone could tell me if the pcm uses the maf table during cranking? It already always starts I just want it to start even better.
Click to expand...

The answer is complicated... The short answer is "probably a little bit" but the main tables you are going to see used in cranking is typically your voltage offset table (which honestly doesnt seem to work as you would expect it to in a 3800 pcm) and your cold start cranking tables (more found in Tinytuner). Typically fiddling with the cold start cranking / warmup table (i cant remember the name) is your best bet to fight around the starting rough, but from my experience you should just be happy it starts.
 


Frost and I live in the same area. When mine was on E85 (Gas now for the winter and drives to school) It would take 5-10 attempts to start it. This could be because of my leaky ass headers and my cam but still. kinda not fun.
 
I know it's a daily driver and I'm not sure how you go about starting the car but I would key on and let the pump fully prime and pressurize the lines before cranking if you don't already.
I know I just jump in and crank with the DD but the turbo car always gets the prime first then crank and even a second prime before cranking depending how long it's been since it's been driven. What fuel pump/bucket setup you using?
 


There masked in hptuners as startup AFR correction and initial vs startup ect. Both have cold start tabs to edit
 
Please explain to me how my 340LPH pump is any better at supplying the .001 lph of fuel necessary to start an engine then the stock pump or your 255?
Click to expand...

GPF.net logic requires no explaination... lol.
 


Going to revive an antique thread here. Go ahead yell at me. Anyways a year and much more experience later I figured out definitively the best way to have effortless cold starts on e85. I had to swap engines this last summer and have a low compressing l67 block now that is MUCH harder to start in the cold with e85.

Step 1. Don't even bother trying to find the correct tables in hptuners... they don't exist unless you murder some other table to trick the pcm into giving you more fuel while cranking (This is what I did last year. Caused me all sorts of other weird issues. I don't recommend it)

Step 2. Get your .hpt file dumped to a bin file so you can open it in tiny tuner. I used a buddys DHP but I think if you email HPT support they will convert your file once for you.

Step 3. Download and set up tiny tuner.

Step 4. Go into your base fueling section under fuel and then find the cranking fuel vs coolant temp table. It should be listed in milligrams vs ect not ref counts and multipliers. When you find the one with milligrams go onto step 5.

Step 5. The general idea is to add fuel here. Personally my car always started just fine above 60* so I only touched 15*c and below. What worked best for me was to multiply 10*c and below by 120% and the 15*c cell by 110%. Its pretty rough and crude but its just supposed to get the engine running so its not critical that it is completely smooth like a maf table. Now my car fires up in 2 or 3 seconds at 0*f or lower without issues.
 
It was about 10* here this morning. Took about 8 seconds of cranking or so with my L67 bottom end and XP cam. I think I'm just going to switch it back to 91 for now. 91 is cheaper to run it on anyways than E85.
 
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