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Discussion Starter · #1 · (Edited)
Has anyone here running higher ethanol mixes like e45+ got the code "cold start fuel pressure performance"

In order for this code to fire my fuel trims have to be learned which means I need to put some miles on my revision. In addition it has to be the first start in "a long time" aka cold start, and even then it's completely random and if it's going to fire, it's going to be within 1-2 minutes after a cold start and cruising. It fires even at 80 degrees outside.

I raised hpfp frp desired 10% on my latest revision in hopes it would solve the problem, but it does not appear so. I questioned another tuner who also has a customer who is having this problem. The HPFP is fine at wot and I believe it's a function of high ethanol content against base rail pressure tables and base cold start warm up tables. I know some people run e40 tunes and stuff, but our 93 pump is e7 and our e85 is usually e75 so it takes me close to half/half mix to get e48->e50 (I have an ethanol sensor). I realize some people may be running e40 stoich's but their ethanol content may only be 35% since they guess when they mix it. So does anyone with a sensor and high ethanol tune have this problem or have had this problem? It's trivial to keep making changes in my tune and having to wait for the fuel trims to learn to see if it worked or not.

Any advice would be appreciated. I'm considering bumping the warmup fuel lost table by 10%



 

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It was 19F this morning and I am on a stratified e50 tune. Everything okay so far. Ethanol sensor says E48.5 too.
 

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Discussion Starter · #3 · (Edited)
based on what I'm seeing in logs during cold start driving and the hpfp meeting the performance of desired hpfp and the fact that was I caught it on a log and checked the log (i started the log within 7 seconds of starting the car) even though the cel didn't come on until 4 min in, the dtc count was 1 from start/finish in the log meaning it was stored since startup. I'm thinking when it refers to cold start fuel pressure it's literally talking about cranking fuel. The below table only index of 0 is used which is 1.00 across the board which means no change. I'm thinking bout making the change in red, but would like some feedback first.


edit: I've made this change and hoping if it solves the issue, guess I'll find out in a few days. (index 0 was all '1.0' before)

 

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Discussion Starter · #4 ·
can someone help me out.

Cold start (First start of the day and low pressure in fuel lines)

Re configure data log for the following Cobb parameters only.

RPM
LPFP DC
LPFP DESIRED (desired lpfp in-tank fuel pressure)
LPFP ACTUAL (or pressure)
FRP ACTUAL
FRP DESIRED
ECT (engine coolant temp)
total fuel trims (CCF parameter)

Turn off the cobb ap auto on/off feature and turn on the access port -> gauges -> start a log and after the log has started, start the car and log it for 5-6 second and then stop the log and upload it to google drive or something. When starting cold my fuel pressure desired is a bit ahead of my actual frp which goes from 54->76->94->200 etc while desired at start is 1600 as in the HPFP desired table. I'm just curious what someone elses FoST looks like. The threshold for the CEL in my tune is 80 psi so 54 and 76 are below that threshold, but I'm not sure how long after cranking bofore that threshold is triggered so I want a log from a focus that doesn't have my issue.
 
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