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HP Tuners not taking changes anymore

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So i've been tuning my buddies twin turbo 6.0L drag car. He's running c16. When I first started tuning the car (at the track only) it was very very lean. Like 15s 16s while driving. Getting into it was only going to 12.8-12.7. So i got it down to 11.8-11.7 in boost where it seemed to like it best. Got the driveability better. However, now for some reason, the AFRs under WOT are still fine, between 11.5-11.8. However idle is now rich as all get out, the lc-2 keeps reading 11.5-12.5 fluctuating like crazy. And in the lower end of the map 70-85kpa going into the transition period, we'll see 9.8-10.1. So I'll start taking out a bunch of fuel and it does absolutely nothing. I'm not sure if it's the LC2 that's reading incorrectly or if its the HP Tuners not making the fuel adjustments anymore. It's in 3bar speed density OS. I make all changes to Primary VE table for fueling.

Any thoughts?

Perhaps your injectors are too large, or not characterized correctly. The issues with improper injector characterization will be more pronounced at low pulse widths -- like idle. Is there a minimum pulse width parameter?

Yes it's set to 1.170 for all RPMS. Im not the original tuner of the file, I was merely helping it to get the lean out of it and it was working fine and now it just stopped wanting to remove fuel in the low end and is staying around 9.8-10.1 then in high boost it levels out. Not sure what to set the minimum injection pulse width. He's on 160lb injectors

You might want to read this article, which discusses the non-linearity, and explains a bit about how one company characterized their injectors to allow good low-pulse width performance.


Have you tried lowering the minimum pulse width parameter in the idle RPM range to see if that helps you?

no because i have no idea about it or what it is i didnt' want to screw anything up because really all i've gotten from the courses so far is how to tune ignition and VE maps in standalones. I hate reflashing but it's the way of the world in 65% of the cases around me at least. So i have no idea on how i go about learning the rest of what isn't taught here

Also checked the default injector pulse width and it's all at the same 1.170. Which im confused how it's only getting 1.170 when in the lower right hand corner it says the range is from 0-998ms

The minimum pulse width parameter is the smallest pulse the ECU will use for the fuel injector open time. With the stock injectors this was hardly any fuel at all, but with the Super-Sized injectors you are using, this value may be way too large. Perhaps you can log the injector pulse width as a parameter and see if it is stuck at the Minimum Pulse Width value. If it is, then it's certainly worth trying to change the value.

As a test -- just try changing it from 1.17 mS (milliseconds) to 0.75 milliseconds. See if that makes a difference in the ability to lean the fuel map in the idle area.

There are only three results from any change -- better, worse or the same. Change one thing, and determine which of these three outcomes you have. If it's not better, then put it back the way it was. Move slowly, and go back if something is not improved. You will learn.

Another idea: Consider contacting the injector manufacturer, tell them what you are tuning with, and ask if they have any injector characterization information for that reflashing platform.

Here's a discussion on the HP Tuners forum about minimum pulse width:


yea i get that i just dont like touching anything i dont know about. My buddy has put a lot of years, time, blood, sweat and tears into his drag car and it's my first car im tuning so i dont want to be the one to come in and mess it up

and it just didn't make sense to me how it could go from lean to me adding fuel and then all of a sudden that being an issue. unless once it was surpassed it wont let it come back down

I read the article about it, the person who originally posted is was complaining about rich decel. The rich issue we have is not on decel. It actually seems to go lean on decel.

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