Welcome to CPGNation.com! Log in or Sign up to interact with the CPGNation community.

Xfi 2.0 Cranking And Warm-up functions

Discussion in 'FAST Support Forum' started by 33Dan33, Aug 20, 2019.

  1. 33Dan33

    33Dan33 New Member

    Joined:
    Jan 8, 2015
    I have some questions regarding the different features that Fast has provided for cranking fuel, choke functions and warm up enrichment. Would love to hear some input from people to see how well they've gotten their cars to start up easily at all different temps, and what graphs they've used or not used in order to make this happen. This is an area that I always seem to be working on to get my car to start with minimal cranking at all times.

    In the global set up parameters, there is the 'crank to run mode rpm'. Mine is set at 700 rpm. What is the method for finding the right number instead of just randomly entering a value? Any relationship to how fast the motor is actually spinning when the starter is engaged? There is also the 'engine revs to to run mode'. Mine is set to 12. Is there any relationship between this number and the 'number of revs before after start vs coolant temp' graph? I do have that graph set really low so that the after start fuel happens quickly.

    Cranking fuel vs coolant temp is what it is for my engine, it has always started much better with higher pulse widths. 68 degrees is about as low as the coolant temp ever gets where I live and the pulse width is around 50ms at that temp, then goes down to around 33ms at the higher temps.

    I guess the biggest questions concern the rest of the graphs that handle things once the engine is running. For a choke function we have a choice between the 'target a/f offset vs coolant temp' graph and the 'after start enrichment vs coolant temp' graph. Does anyone have a preference for using one over the other, or do they use a combination of both? I use a minimal amount of a/f offset up to 90 degrees and then cut it off, and rely more on the after start enrichment instead. That graph is set to around 35% at 73 degrees and goes down to around 10% at the 255 degree point. As mentioned above, I have the after start fuel set to kick in really fast, 12 revs at 0 degrees down to 7 revs at 255 degrees. My 'after start decay rate vs coolant temp' graph is also set so that all this extra fuel goes away pretty fast and the 'aft corr' number gets to zero so closed loop can kick in. My car seems to idle a bit better in closed loop.

    The point of asking all the questions is this. I think I had my car set way too rich in both cold and hot starting conditions, which was causing a no start condition when I had my car up in a higher altitude. Which leads me to my final question. Even with the loaded indexed speed density mode in use, should we expect to have to still go in and lean out our choke functions if we are at a somewhat significant change in altitude?

    Hope this ramble makes sense to someone, or again just looking to see if anyone cares to share what tweeks they've made to their software that's helped with starting their engines both cold and hot...
     
  2. Fastmanefi

    Fastmanefi Well-Known Member

    Joined:
    Jun 4, 2011
    Location:
    Sonora, CA
    Yes, your ramble makes sense. But I'm going out for dinner. Maybe I'll respond later. Or you can just call me. ...LOL...
     
  3. fabr

    fabr Member

    Joined:
    Jan 23, 2017
    I'd LOVE to read your reply when you get the time. Thanks!!!
     
  4. Fastmanefi

    Fastmanefi Well-Known Member

    Joined:
    Jun 4, 2011
    Location:
    Sonora, CA
    Okay, here goes:

    You are waaaaay over thinking this. This RPM only tells the ECU when it can switch from crank mode to run mode. FAST shouldn't have had any RPM. 250, 300, 400, 500 all do the same thing. Set it to 400 and forget about it!

    1) Assuming the engine is mechanically sound and timing has been verified: Add GPW (injector pulse width) to the dash that you like to use.
    2) Adjust your "fully warmed up" motor for the best idle. This means manually with CL off, just like you would find the best idle with a carb.
    3) Multiply the GPW by four and use that as your cranking fuel for all temps over 140 degrees.
    4) Slope the curve at cooler temps to four times that number at zero degrees.


    Geeze. I don't know where to start. All I can do is tell you what I do and you can take it from there.
    The Target AF table vs coolant temp is almost a useless table. Why offset the Target AF if the ECU won't go into CL to begin with?
    1) Get the warm engine dialed in (no CTS fuel being added).
    2) Zero out the target AF offset table.
    3) Monitor the Actual AF on the next cold start, and adjust the CTS Correction table - in real time - as the engine warms up, and keep the actual AFs in the 13's. At 136 degrees the CTS table must be at zero.
    Warm up done!

    After Start:
    Assuming everything above has been done correctly - Watch the actual AF during that 10 to 20 second period after starting. If lean, move the after start begining point up; if rich move the point down. Remember, the after start curve is just the starting point, so you'll have to turn off the engine to try any new setting.

    I'm going to have breakfast now.....
     
  5. 33Dan33

    33Dan33 New Member

    Joined:
    Jan 8, 2015
    Fastman, I really appreciate your input on all of this! Hopefully your shared information can benefit others besides myself. When I get a chance I will go in and play with all of my settings based on your suggestions and kill the Target AF table. I like your math better than what the Fast manual offers for dialing in the cranking fuel. I tried to follow along with their method quite a long time ago and didn't have such good luck with it. Anyways, I will post a follow up on how my engine responds to these changes; am pretty happy with the tune other than just getting it to start better at all temps and not just when it's cold. Many thanks again!
     
  6. fabr

    fabr Member

    Joined:
    Jan 23, 2017
    Thank you fastman!!
     
  7. Fastmanefi

    Fastmanefi Well-Known Member

    Joined:
    Jun 4, 2011
    Location:
    Sonora, CA
    Dan33
    Dont "KILL" the target AF table like you said. Only kill the OFFSET to that.
     
  8. 33Dan33

    33Dan33 New Member

    Joined:
    Jan 8, 2015
    Got it Fastman, I only zeroed out the offset table as you suggested. I've only had time to mess with the cranking fuel so far and had to add a bit more than the 4xGPW value at hot idle in open loop. The GPW number was around 1.95. Once everything else is done I'll update, thanks again for the guidance..
     
  9. Fastmanefi

    Fastmanefi Well-Known Member

    Joined:
    Jun 4, 2011
    Location:
    Sonora, CA
    1.95 is a very low GPW. I would set the hot cranking fuel to 10ms. That's about my minimum that I use.
     
  10. 33Dan33

    33Dan33 New Member

    Joined:
    Jan 8, 2015
    Here is what I've ended up with; the car is starting much much better now, especially when the coolant temps are warmer. I may still have some work to do on the after start graph while initially warming up, but was seeing the a/f ratio staying in the mid to upper 13 range everywhere else. All of my previous settings with these graphs were adding way more fuel than the engine needed, which may have been causing problems while in a higher altitude. Not to mention the offset graph that you had me zero out. I did have to bump up the cranking fuel for the engine to start initially when it was cold, not sure if I can lower it back down any or not; doesn't seem to be hurting anything to just leave it alone. Many thanks again, Fastman. Screenshot (1).png Screenshot (2).png Screenshot (3).png
     

Share This Page