Wow that sounds very confusing lol. So the only thing I know for certain right now that my HPF side should not be tanking the way it is (again only when tuned). My god this is infuriating. What I would do for a set of jets, a carb and an old school Vacuum advance.....


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How low does the rail pressure get and at what boost level and rpm?

It varies, the lowest I have seen it is 750psi and that's at 14.5 psi at 4000 rpm.


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Ok that's what I was looking for...that' is on the low side...should be no problem to pull well over 1000psi at that boost and rpm ....

Interesting info for those of you trying out "race gas" turns out this fellow also had an issue with his car pulling more fuel in winter due to "winter gas". And this was Arizona winter gas lol. I would love to find out what the value is of our winter gas up here. It's no wonder it's pulling so much more fuel to get to 0.81 Lambda at wot. Or 10.8 Afr. If I understand what he is talking about lol.


kmhamel
Second gear

Join Date: Jul 2009
Location: Healy, Alaska
Posts: 126
I ran across this awhile back, maybe it can be of some use:

Race Gas Stoich Rating Tuning Considerations

Well I have seen questions from time to time about adding race gas without tuning which can be a very expensive experiment. I am going to explain how stoich effects AFR. Hopefully in simple format.

I am not going to get into MAF transfer functions or other tuning functions.This is just about fuel.

First lets define a few terms:

AFR: Air Fuel Ratio

Stoich Rating: In simple terms is the AFR to have chemically complete combustion that is neither rich or lean. For Example most pump gasoline is about 14.64 to 1. Which means 14.7 parts of air to 1 part of fuel.

Lambda: Is a term that is utilized when tuning. In basic terms think of it as an adjustment to your stoich rating when tuning AFR. For example with pump gas tuning .80 lambda, 14.7 x .80 = 11.76 AFR target.

Lets assume your car blower car has a nice tune that gives a perfect 11.8 AFR under WOT with pump gas.

So now it is race day. We add some timing to our tune, drain the fuel tank, and fill up with some high octane unleaded VP109.

We go for a blast down the 1/4 mile while datalogging and see the A/F is reading 12.8 then make a quick trip to the bathroom only to find out they are out of toilet paper -lol.

There are a few factors here to consider.

The stoich rating of VP109 is 13.41.
Most wideband A/F modules are calibrated to 14.7 pump gas stoich.

So this is the formula to determine the true A/F for the run.
AFR/Wideband Stoich x Race Gas Stoich
12.8/14.7*13.41= 11.7 AFR on Race Gas

So you may think 11.7 sounds safe but we must remember the VP109 stoich is 13.41. So 11.7 AFR = .87 lambda. For the most part a safe lambda value is .80 to .82 for a forced induction mustang. I prefer .80

So we take VP109 stoich of 13.41 x .80 lambda = 10.73 AFR
This is the AFR (10.73) I am tuning for.

Keep in mind this is not what will display on your wide band as it is programmed to 14.7 stoich. You must convert the AFR.

AFR/Race Gas Stoich*Wide Band Stoich

10.73/13.41*14.7 = 11.76 AFR is what I want to see on my wideband when running VP109.

Just to reiterate 11.7 on the AFR display with VP 109 is really a 10.7 AFR.

Ok so hopefully you are not totally confused.

There is a simple solution to all of this madness. The SCT Advantage software has a Scalar for Stoichiometric Air Fuel Ratio. You simply enter the correct value for the fuel you are using and all lambda fuel calculations will be based on this value. Then just do the first formula conversion to determine what you should be reading on the AFR display. Some AFR modules may be able to be programed to the correct stoich.

Or leave the stoich in the tune and wideband at 14.64 and calcualte what AFR you need to read on the wideband for the fuel that is used. (This is how I did it in the past, but I find it easier to change the stoich scalar)

This is why you have to exercise caution when mixing race gas and pump gas as you do not know the true stoich of the mixture. The leaded race fuels have a stoich that is closest to pump gas. I always drain my tank before putting in the race gas. When I mixed fuels in the past I didn't notice a drastic change in AFR, but when I have 100% unleaded race gas it really leans out with a 14.64 stoich scalar in the tune.

The other caution is the winter (oxgenated) gas we get in Arizona. I noticed the car leaned out in the winter when it was tuned on the better summer blend. A 14.1 stoich scalar works for the AZ winter gas if your initial tune was based on the summer blend.




Race Gas Stoich Ratings

Sunoco MO2X UL – 14.5
Sunoco 260 GTX – 14.4
Sunoco 260 GT – 13.9
Sunoco 260 GT Plus – 13.7
Sunoco Standard – 14.8
Sunoco Supreme – 14.9
Sunoco MO2X – 14.5
Sunoco HCR Plus – 14.8
Sunoco Maximal – 15.0
Sunoco MaxNOS – 14.9

Turbo Blue Unleaded (100 octane) -13.9
Turbo Blue Unleaded Plus (104 octane) - 13.7
Turbo Blue 110 - 14.7
Turbo Blue Advantage - 14.9
Turbo Blue Extreme - 15.0

VP Street Blaze 100 - 14.16
VP C10 -14.53
VP C16 - 14.77
VP 110 - 15.09
VP MS109 - 13.41


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It doesn't matter what fuel you are using, the ecm is going for a complete burn of 1.

It will add or subtract fuel as necessary to get to 1.

I assure you the fuel you are running isn't causing this issue unless they put E-85 in the wrong tank.

That being said, I've had pretty high percentages of the corn and not seen FRP that low across third.

You would know because your trims would move very high to compensate for the much higher fuel demand.

Quote from: FoMoCoSHO on April 26, 2015, 08:46:21 PM
It doesn't matter what fuel you are using, the ecm is going for a complete burn of 1.

It will add or subtract fuel as necessary to get to 1.

I assure you the fuel you are running isn't causing this issue unless they put E-85 in the wrong tank.

That being said, I've had pretty high percentages of the corn and not seen FRP that low across third.

You would know because your trims would move very high to compensate for the much higher fuel demand.

Wouldn't it also be dependant on the tune also? I am still trying to wrap my head around the whole lambda vs AFR. That said, I am still confused as to the reoccurrence of the same symptoms as last spring. Is there any possibility of the tune in combination with E10 winter gas plus the cold temp be the cause. (It no longer misfired when temps rose above 10C) It might be a stretch but I am getting a feeling of déjà vu. Hence why I am asking and posting quotes.
Also I have been through everything except the HP fuel pump and controller. It does not exhibit anything when the stock tune is loaded. No matter how hard I try.


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Ok so another weird and wacky update. With all of the suggestions and info from my web searches, I decided to do a few things. #1 Installed the 3 bar sensor and 91 V8 tune. I then reset the communication codes in the PCM and reset the adaptive learning through Forscan. To ensure that I had actually reset everything possible I then followed these instructions.

https://youtu.be/hZAsoqmqhdM

And followed his instructions regarding the learning process. Drove the car for about 2 days without doing any crazy WOT blasts and 55 mph pulls. 
After FoMo's and ajp comments I decided to start logging fuel trims and dropped a few other PIDs that were unnecessary for this purpose. As I am trying to limit the total PIds that I am monitoring to keep the connection as quick as possible. So it's 8C today here (it's finally going to warm up later this week lol). Drove the car today a little more aggressively. A few WOT pulls from 0, a few WOT downshifts into second and then finally a few WOT pulls down into 3rd to 4th. It's gone, I mean completely gone. I am still running the same fuel. I can't be happier however I am skeptical that it's truly gone lol. I will continue to be cautious over the next few days just to be safe and datalog any WOT blasts. HPFP no longer drops below 1500 PSI. However I know see the TP1 sensor modulating on a hard WOT downshift. It's not stuck at wide open. I will post a few screenshots of the data logs later showing the HPFP and the trims. 

Any ideas on the results? Could the car actually needed to adapt to the fuel or conditions was there something stuck in the KAM that was contributing? This is over my head, any insight would be great.       

And the logs!

So after another frigid day it has not come back, I just realized this topic got to 15 pages. I want to thank you guys for sending me ideas and responding to my posts and questions so quickly. If it was the last set of things that I did that fixed it I have no idea for sure. But I know that some of you SHOdded for one suggested something to do with logic of the fuel control module. And that got me thinking on how to force a reset. I looked through my post from last year. I may have inadvertently done this exact thing. I never did find out what fixed it last year either.     

Good news!!!

Rich

Still all good, ShoBoat?  I am not hoping for more frigid weather for you , but if it does give you the opportunity, do the reset and test with 93 version of V8 maybe?

Quote from: SHOdded on April 30, 2015, 07:48:05 AM
Still all good, ShoBoat?  I am not hoping for more frigid weather for you , but if it does give you the opportunity, do the reset and test with 93 version of V8 maybe?

All good, I did another fill up at the busiest gas station in the area with 94. Did the reset procedure and installed the 93v8 tune. All is good so far! No pressure drop or misfires or hesitation.


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Will be good to know info for anyone else looking for a solution to these problems   "Try the reset!"

Take a look at this sae study on gtdi/tgdi. Wonder if you could be experiencing this.
http://www.stratifiedauto.com/blog/low-speed-pre-ignition-in-the-mazdaspeed-disi-and-ford-ecoboost-motors/

http://papers.sae.org/2015-01-0758/