Thread: Injector flow rate OR Cylinder gain?

Total tuning noob here. Drop some knowledge on me, please. HPtuners for reference.

Recently installed some #42 injectors and filled up with E85. Stock tune. LTFT's are consistently high. ≈6 at start up. ≈10 idling, at or past 16 cruising. Never negative. Never below 6.

I'm thinking I should adjust something (not sure what) to bring them down. Trying to be positive and negative by the same amount. Like, try to hit the center of that moving number. Assuming I'm right so far(?), I read that this can be done 2 different ways:
1.) Adjusting the IFR. I'm thinking if I multiply the IFR by 0.95, that should get me close?
OR...
2.) Adjusting the cylinder gain. Maybe start at 1.02?
These numbers are shot from the hip. They could be adjusted repeatedly until I felt comfortable with the results. Just want to know what would be the better, or proper process.

Again, maybe I'm wrong, but shouldn't I have my stock trims centered around zero (not be consistently positive) before I do any other tuning? All basic maintenance is up to date. New plugs, wires, fuel filter, and cleaned TB and IAC. No vac leaks.

Thoughts?

A lot of methods will work a lot of diffrent opinions on what's best.

i stick to the writeup I sent you, bY inputting the proper injector data you have and adjusting your p.e afr, and stoich value you'll have a solid performer.


The other old method is just adjusting ifr to match your ltft Error.

knowing that you have a wideband and hpt pro. You need to get into open loop and scan to see your error percentage and apply accordingly. Re enable closed loop and you should be dead on.

Hopefully I will have some time to do some scans tomorrow. To stay in open loop, I just bump my "closed loop enable coolant temp" to the max (284° temp)?

or you can just use the scanner VCM control------fuel and spark---closed loop enable off just for ****s and giggles reset fuel trims as well

I would make adjustments to the MAF table to zero the LTFTs out as close to 0.0 as you can get them. Just me though.

Well... Will you look at that! Guess I hadn't even opened the scanner yet. I've only played in the editor. Looks like I need to go for a drive now.

Edit:
After a good night sleep, and a little more reading, it's making more sense. I created a custom histogram to log LTFT on the MAF table in the scanner per the sticky at the top of the page.

Here's my plan:
1.) Change target stoich to 9.85
2.) Zero out the HOT PE table
3.) Connect laptop and Flash PCM
4.) In "VCM" controls, Turn close loop OFF and reset fuel trims
5.) Start the car, click "start scanning" and go for a drive.

Then go from there...

Just one more question before I haul the laptop out to the car.

Is there anything special I need to do or setup for the scanner to read my wideband? Using HPT Pro, and an AEM wideband, here's what I know so far:

#1 spot on the HPT interface is a chassis ground
#5 spot on the interface is 5v signal from the wideband (White wire in the case of the AEM UEGO)

Once those wires are connected, is it just "plug and play"?

Originally Posted by 231FUN

Not sure what the funky double line that sort of looks like an equal sign is that you're putting before your numbers.
LTFT's are usually represented as positive or negative with a plus or minus sign eh (+) (-)

That's the mathmatical symbol for "about" or "around"

Originally Posted by Reptile

While I'm a pretty good advocate for doing MAF tunes, for cruise and driveability.....I'd still recommend doing the IFR table to get a base line. When you change injectors it helps to get the flow rate as close as you can first, because if you tweak the MAF table too much after an injector swap you're gonna have shifting problems with the trans.

I think this answers my question. So I'm going to adjust my IFR before I do any real tuning.

Thanks for the feedback guys. It's starting to make some sense. Time for some trial and error...

why bother with LTFT when you have a wideband. do your lambda error or AFR error whichever you prefer, make your adjustments and be done.

Originally Posted by 91parkave

why bother with LTFT when you have a wideband. do your lambda error or AFR error whichever you prefer, make your adjustments and be done.

That's a fair question. Here's where I'm coming from. I'm looking for a super simple way to bring my LTFT's down for 2 reasons:
1.) I'm not running "pure" pump E85. I've been adding a little 91 to my E85 as a down and dirty way to bring my LTFT's down enough to not set a P0171 code. I want to run a couple tanks of straight E85 through the car before I do any real tuning. I'd like to have every trace of 91 outta there before I do anything serious.
2.) I'm a total noob! I want to adjust 1 thing to address my immediate problem. This will buy me some time while I educate myself. Also, have to wait for a certain member to come up with some free time to help me out in person. :wink:

Ya, I get what you're saying.

My reason for changing IFR is because they are so far out, it was actually triggering a MIL. I don't like seeing that.

If you put stoich/ ifr where it needs to be you won't have to deal with the rest of it. Changing stoich to the e85 target of 9.85 will correct itself till you have nothing but e85 in the tank.

Originally Posted by darkhorizon

I would just let the trims do what they want. Its not going to change anything by "fixing" them because all you are going to do is add fuel in the tune so it has to "do less work" in the LTFT. If anything the +16 cruising helps you get a bit of a lean cruise going.

If it isnt broke dont fix it.

No.

I scaled my IFR by 90%, and I think it put me right where I want to be. I'm seeing positive and negative LTFT's, but it's hanging mostly around zero. I think this will be a good starting point, or baseline for future tuning.