XFI warm start problem

DGC

Senior Member
Joined
Jan 10, 2004
Having difficulty starting warm engine. Cold starting is fine. Warm starts require full throttle. Combinations of IAC, cranking fuel enrichment and injector pulse width settings appear to be the issue. Before experimenting with tables, I would ask whether anyone has IAC settings, cranking fuel enrichment and pulse width settings versus coolant temps? In order to determine which direction to change, I would ask what a/f ratio is appropriate for cold versus warm temps? And
which fuel table is best to view a/f values when starting.
Thanks for any advice.
dgc
 
Who did you buy the XFI from?
Set up your logging dash with all your sensors you want and have that dash for all your tables. Off the top of my head the basic things to populate dash with are..... Batt volt, Target AFR, Actual AFR, O2 corr, Inj duty, RPM, IAT, CLT, Spark, KPA, PSIg, TPS, Esc rtd.
Chuck nailed it...... log your warm start.
WOT at start puts it in clear flood mode.
Getting start up, idle, tip in and driveablilty takes time, patients and a few tanks of gas.
IMO its 50% or better of the cars out there with Classic/XFI, BS3, etc etc and they all have shit start up, tip in, stall when put in gear, surginng idle, etc etc WOT is good but the rest isn't. I have yet to have a car show up with one of said systems that didnt have a issue with above said symptoms.
Biggest thing is once you fell comfortable knowing how to save/flash a tune dont be afraid to tweak stuff and see what affects what. If you get it all jacked up reflash in your starting point and try again.
 
A cold engine will still run OK with the wideband reading 13 to 1 or so. A bunch of the fuel will puddle and not really support combustion. The mixture you're throwing at it will be much richer, but won't read as such on the wideband.

Agree Your hot start definitely sounds rich since wot helps it fire.
 
Don't seem to be able to post .gct tune table or data log. Error indicates inappropriate file extension. Any tips on sharing this data?
Thanks for the replies.
 
Having difficulty starting warm engine. Cold starting is fine. Warm starts require full throttle. Combinations of IAC, cranking fuel enrichment and injector pulse width settings appear to be the issue. Before experimenting with tables, I would ask whether anyone has IAC settings, cranking fuel enrichment and pulse width settings versus coolant temps? In order to determine which direction to change, I would ask what a/f ratio is appropriate for cold versus warm temps? And
which fuel table is best to view a/f values when starting.
Thanks for any advice.
dgc
Without me looking at your log. Some of the basic things I would play around with.

A warm engine requires much less fuel to start. Full throttle at start up is clear-flood mode (no fuel being injected) . This may tell you to highly reduce your pulse width vs. temp during cranking.

Then maybe or also, increase your IAC start position. Basically, try to imitate what you do manually in the program to get it to start.

Be sure your IAC is working. When the car is running, try increasing and decreasing your idle on the idle vs. temp map. See if it goes up-and down on your command. (just a test, I had a bad IAC once and kicked myself in the ass for not checking the simple thing.)

For start-up, AF doesn't mean anything really. It's all on pulse-width until the cranking maps decay out. If you can get it to start, and it stays running, leave the AF changes out until later, it may not even need to be messed with. BTW, my car likes 12.8 for idle. But this will probably mean nothing to your combination.
 
Update.

Thanks for the help. Cold and warm starts are fine (as commented, cut warm pulse width to half the cold start setting). Not able to log warm running engine. Will go back to manual and see what I am doing wrong. Since I am hearing a miss-fire when holding @1500 rpm, I am curious to know where to look.
More advice please?

dgc
 
Update.

Thanks for the help. Cold and warm starts are fine (as commented, cut warm pulse width to half the cold start setting). Not able to log warm running engine. Will go back to manual and see what I am doing wrong. Since I am hearing a miss-fire when holding @1500 rpm, I am curious to know where to look.
More advice please?

dgc
Miss fire? At a steady 1500? Or tipping into 1500? Do a log or two.

Could be an AF/ AE issue.
 
Finally found the time to log some data. Attached file includes what I believe are the appropriate sensors. If others are
necessary/helpful, please let me know. The recording is for a warm engine running at idle (~1 minute) followed by a segment at a little higher rpm. Clearly the idle segment has the spark(btdc) bouncing all over. It smooths out at higher rpm. VE and A/F look fine to me, but clearly there is a problem. At idle, the engine exhaust will 'pop' every 10-15 seconds.

As I stated earlier, I am on a learning curve. Recently purchased the FAST XFI instructional video. As a video, it is difficult to assimilate the information, but I keep reviewing the chapters. The downloadable manual helps a lot.

Thanks for any help.

dgc
341107
 
Finally found the time to log some data. Attached file includes what I believe are the appropriate sensors. If others are
necessary/helpful, please let me know. The recording is for a warm engine running at idle (~1 minute) followed by a segment at a little higher rpm. Clearly the idle segment has the spark(btdc) bouncing all over. It smooths out at higher rpm. VE and A/F look fine to me, but clearly there is a problem. At idle, the engine exhaust will 'pop' every 10-15 seconds.

As I stated earlier, I am on a learning curve. Recently purchased the FAST XFI instructional video. As a video, it is difficult to assimilate the information, but I keep reviewing the chapters. The downloadable manual helps a lot.

Thanks for any help.

dgc
View attachment 341107
That's Idle RPM timing trim.

Go to: view > idle functions > timing trim. See the map called "Spark Offset vs. Idle Speed Error"

Zero out that map! Then the timing won't change. Leave it zero'ed out and tune your idle to perfection. Only then, should you use this map to make it even more perfect!

Try a richer AF. Maybe around 12.8 or 13. May smooth it a bit. Lean it out later when balancing. Turn on the O2 correction and use it to find the proper VE number. Probably between 27 and 32.

I can't open your tune from this computer. So I have no idea where else to start except to just through out some thoughts.
 
AAlso check your timing table as well as teh AFR tables to be sure that the elipse isnt kissing other cells that have a different number as that will cause afr corrections and timing to change. I.E>- if your elipse is wobbling on say..24 degrees as well as kissing 30 degrees then the timing is going to be from 24 -30 as it dances between or kisseds these numbers, same goes for afr table.
 
Thanks to all for the suggestions. Making progress but still not satisfied. Zeroed out the "Spark Offset vs. Idle Speed Error" as suggested bu Joey Perotta and opened up the AF parameters for all surrounding cells at idle (turbo nasty) to fix the have the spark(btdc) from bouncing all over.
Focus now is to achieve a proper idle. I have set the closed loop parameters to force open loop mode (triggering closed loop operation at 200 rpm above idle). Here are the issues I am struggling with. At idle, the target and actual AFR consistently differ by 1 unit. Setting the idle target AFR at 14.6 results in an actual AFR of 13.6. Rereading the manual (Section 11.2 Idle Speed vs Coolant Temp) suggests that I should be able to achieve a IAC target in the range of 15-20 counts. My cross-hairs are always above the green line with a IAC target at 40-50 counts. Once again I went back to the manual, but am still searching. Per Chapter 11.2 instructions, "adjust the throttle blades on the throttle body so the cross-hairs are locked on the targeted RPM". Cannot achieve this. Rechecked IAC gain, and find no issues. Reset the throttle linkage and tps, w/o improvement. Overall the idle is better, but there is still and occasional 'pop' in the exhaust.

If there are other parameters I should post, please let me know.

Still learning. And thanks for the help.
DGC
 
Forgot to mention that my o2 correction is 0%. But the wbO2 value in the dash is "1". How to I test whether the wbO2 is functioning?
 
Let's start somewhere.

make sure your o2 correction is on.

Be sure you are allowing positive and negative correction in your idle area by checking your correction limits map. Make it about +10 and -10 for now.

Slow down your correction in you O2 gain map. Make it about 5 or so.

Enter 28 into all the cells of your VE map around idle just to get you going.

Set your target AF to about 13-13.5 for now. Later you can change it. (may be good for you, mine is richer)

Set your idle timing to about 26 degrees. (works for me, but others please chime in)

Set your idle rpm to 850 on idle speed vs coolant temp. (maybe good for you, mine is higher.)

set your idle "max tps for idle (%)" to 10% for now. (when you find the correct throttle blade location you will re scale the TPS and set this number to 1 or 2 %)

Start it. Keep it running until it warms up.

Adjust throttle blade until cross counts are 15-20.

go to VE map. Look at O2 correction. Is it close? Does actual match target? If not, add or subtract VE until it does. Tip the throttle and let it stabilize and check it as you do this.

When it matches with very little correction (+5 to -5) then that's your number.

Now you can tweek the timing and AF to smooth out the idle. Don't try to idle it to a number in your head. Give it what it wants.

Go back and re-scale your TPS and set your idle TPS to 1 or 2 percent. (1 works for me.)

Is your combination unusual? Mine is. I don't have any belt driven accessories (very little load on engine while at idle). My idle requires a little timing off-set. Yours may not.

Basics first. fine tuning and balance later.
 
Joey,
Thanks for taking the time to generate a step-by-step recipe. Worked great! Stable idle with +/- 3% O2 correction, and a level IAC at 17 counts. Playing with appropriate variables for further tweaking, but am quite happy with the results. My fault was not exploring a wide enough range of throttle blade positions. Once the blade was opened further, the IAC counts finally began to reduce (from 60 and a unstable idle).

As you might expect, could not resist a WOT test. Big time bog before a response. One step at a time. Probably will need more consultation.

My build began 10 years ago, and is nearing completion. Engine was done by a retired nascar engine builder. Followed his recommendations for building a solid engine with ~200 additional rear wheel bhp.

Thanks again for your help.
DGC
 
Dude!

I'm so happy it's working out for you. Now you have to get the rest of the VE map populated. Along with a bunch of other stuff. But you'll get there.

I know it's hard, but please, stay out of the throttle!
 
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