Procharged G8 Tune questions

[bluegoat06]

I'm not familiar with FI tunes at all, and i'm trying to help somebody with his setup, and correlate possible engine failure with a bad tune.

The car is a 2008 G8GT, Procharger D1SC 9PSI 2 core intercooler, 80# FIC injectors, Pacesetters Longtube headers, catless with flow master mufflers. tune attached. the car was running like crap just after SC install and tune, owner felt the car didn't have a lot more power after the sc install and tune. LTFT's in the 20% area, car was throwing P0171 and P0172 errors.

The tuner didn't adjust SD at all, didn't turn it off either to tune her. stoich ratio seemed to be double, and nothing else seems to have changed in the injector section, only the short pulse limit was lowered. Timing lowered, and a couple of other little BS. Lol is this how people tune FI this days with bigger injectors ? WTF ?

Can somebody explain the AFR trick ? why would the tuner attempted to increase stoich AFR like that, is this some sort of new trick for bigger injectors, or just one of those "opps, i just splashed my fingers in the keyboard, give me $500 for the job" type of thing?

The car was running so bad after the SC and tune, the owner had the engine checked, cylinder 6 has a blown piston and spark plugs in Cylinder 6 and 4 have exploded. Compression in 4 is 170 and 0 in 6

Thanks

[c.u]

It`s an old trick for the inj and not have to scale all the air g/cyl and torque table`s for the auto trans. Why he did not tune it maf onley who know`s.

[IDRIVEAG8GT]

"Tooner"

[HoP]

"Tooner"

Literally

[bluegoat06]

So how do you even tune a car where the stoich doesn't match what it is in tank ?Commanded AFR would be 29.36. Lambda per the 02's would read 1, but the fuel trims would be out of wack because that commanded AFR. What would be my target commanded AFR, can't be 29.36.
How about the injectors section, i think read somewhere besides doing this to the AFR cell, that you're also supposed to cut the IFR in half.
What do i look in the logs to know the MAF limits are not reached, in my car i only worry about HZ, doing this 2 things, and figuring out the commanded AFR issue, do i tune the MAF as always, applying LTFT or STFT's error% and WB error% for WOT ?

[realcanuk]

When I went over the injector limit I just doubled stoich and cut IFR in half. Everything works perfectly. In the hptuners pid just multiply commanded afr by 0.5 to bring commanded back to something you are used to.

[bluegoat06]

How do you know when you're at the injector limit ? IDC>100% ?
If commanded is say 29.36*0.5 in the scanner, how do the fuel trims react to the actual 29.36afr in the calibration ? or this is where cutting the IFR in half compensates the doubled value in the new stoich AFR ?

[realcanuk]

How do you know when you're at the injector limit ? IDC>100% ?
If commanded is say 29.36*0.5 in the scanner, how do the fuel trims react to the actual 29.36afr in the calibration ? or this is where cutting the IFR in half compensates the doubled value in the new stoich AFR ?

The trims read properly as the cut in ifr offsets the change. I don't like to see my IDC over 80% but 90 is probably still safe.
every other aspect of my tune and scan read properly other than the calculations in the DIC. (mpg, miles to empty,etc)

[bluegoat06]

Great, thanks a lot dude.

[DSteck]

People need to stop thinking about AFR and start thinking about lambda. Life really does become easier.

[bluegoat06]

I tune with Lambda, but the AFR cell in the calibration is still AFR.
In the scanner i have a PID for commanded lambda, but i need to input the afr in that cell in my scanner PID, so i can see commandend lambda, is there an easier way to reflect lambda in the scanner ? when i pump E85, i need to change that AFR to reflect E85 stoich so my car can run. only thing i change in the car for E85, i guess i can't forget about AFR completely because without that afr cell, my car wouldn't run E85 or propane if i wanted to.

[DSteck]

Commanded EQ Ratio = commanded lambda in E38/E67

The value entered in for stoich is important, but once it is entered, I never look at it again.

Doubling the stoich number and cutting the IFR in half is a very simple way to accomodate larger injectors without totally throwing the torque model out the window. I use that method on a lot of things.

I only use Commanded AFR on 0411 applications.

[bluegoat06]

Ty Steck.

[realcanuk]

I tune with Lambda, but the AFR cell in the calibration is still AFR.
In the scanner i have a PID for commanded lambda, but i need to input the afr in that cell in my scanner PID, so i can see commandend lambda, is there an easier way to reflect lambda in the scanner ? when i pump E85, i need to change that AFR to reflect E85 stoich so my car can run. only thing i change in the car for E85, i guess i can't forget about AFR completely because without that afr cell, my car wouldn't run E85 or propane if i wanted to.

I tune in lambda also. My commanded AFR shows as 28.80 but I just ignore it as the actual lambda and lambda error show properly.

[DSteck]

I tune in lambda also. My commanded AFR shows as 28.80 but I just ignore it as the actual lambda and lambda error show properly.

[keith42]

A couple of things strike me as odd.

1. How do you know the tuner didn't "fail the maf" to tune it?
2. I watched the video of the owner on the road course with the car, if the car wasn't running right why would you continue to lap it? Not siding with the tuner but when I do a build and tune the car to me that is the starting point of sorting the car out especially on a forced induction build. I've had my new build running good, put a couple of hard pulls on it and had the idle hang or split a vacuum/boost reference. Find out I don't have enough crankcase ventilation.

I just don't understand why he didn't bring the car in and call it a day if he couldn't figure it out. It might be the tune, blockage in the fuel delivery, burned fuel pump wire from a new high amperage pump, etc. You just don't know in the initial stages, but you do know it's not right and you should figure it out first before hammering on it some more.

[G8-4-speed]

The issue you run into with changing Lumbda/AFR in the tune is it changes the calculated IVT for fueling. The IVT runs very hot when you adjust this which changes transient fueling and open-loop fueling. Not saying it can't be tuned this way but to me it messes up more than you fix in the tune.

Even if the tune didn't kill it, the lack of fuel did. G8 pumps will NOT hold up with 9psi on a road coarse. Especially with no BAP. It will heat soak and lay over at rpm. @4800-5200 I have tuned too many with boost and a fuel gauge tapped into the fuel rail while tuning. After several hard runs with hot gas and hot fuel rails, the fuel will vaporize in the rails during the pressure drop. SO instead of pushing raw fuel thru the rails, you push vapor. Lays right over and goes dead lean.