Leaded and unleaded race fuels
#1
There are a variety of unleaded and leaded race fuels available. Some can be found at your local race track or gas station, others are stocked by race shops.
It does no good to run these high-octane fuels without a tune designed for them.
If you are going to mix race fuel with pump gas I only recomend running leaded race fuels. These fuels do not have any oxygenates and have a stoich point very close to pump fuel.
What is the stoich point? The stoichiometric air/fuel point is the ideal point where all the air and fuel burn. For pump gas it is 14.64:1, if you have E10 pump gas (10% ethanol) it is 14.19:1. For E85 it is 9.85:1. VP 109 unleaded race fuel is 13.65:1.
What this means to the average Joe, if you run a fuel with a stoich point lower than 14.64:1 your tune will need to be set up accordingly to add more fuel. This is easily done if you know the exact stoich point, but finding the exact value is next to impossible if you are mixing pump gas and race fuel from the local 7-11. This is why I recommend running a leaded fuel, the stoich point will be very close to that of pump gas.
In the long term lead will clog cats and kill the stock O2 sensors. In the short term there will be no detrimental effects. If you are just throwing in a few gallons every weekend at the track you will most likely be fine. One thing to note, Bosch wide band sensors are very sensitive to lead contamination. The lead will cause them to read inaccurately. I only recommend using NTK wide band sensors.

QUESTION:
Since this (E10) drops the stoich to ~14.19:1 how does that affect the WOT AFR? If I'm tuning for an open loop, wot AFR of 11.6:1 do I need to adjust that number if I'm running E10? I use the Bosch wideband sensor but I do not run any kind of leaded fuel - race or otherwise. If my LM-1 is saying 11.7:1 and I'm running E10, I wonder if it's really 11.7:1?

ANSWER
There is a parameter in the software called stoich point, you should change that to match the fuel you are running.
Based on some old forum posts I don't think innovate understands how to compensate for fuels with different stoich points, but you could try asking them again. Your wideband should be pretty close though with no special changes, within .1-.2 IMO.
Factory O2s find the stoich point of any fuel.
For my AFM 1000 there is a formula to plug in the H:C ratio and O:C ratio of a fuel and properly display a/f.
Now keep in mind the ford base fuel table is in lambda....lambda is always the same regardless of fuel, and the factory computer knows this as long as you are inputting the correct stoich point into the tune.

QUESTION
So my tune is dialed in for pump gas.
To run race gas I have to change the stoich point in the tune.
When this is done will the A/F be the same or will I need to adjust the MAF Transfer curve again on race fuel?

ANSWER
Find out the stoich point of the race fuel, and plug that value into the tune. If you are running 100% race fuel then your a/f will be correct.
Don't change the maf xfer, that will mess with load. If anything you would change the base fuel table.

QUESTION
This is interesting stuff. I stopped and picked up racing gas for the track this week end. I started using leaded this year with the cats being gone. I asked for info on the fuel and in the info they do not list the stoich point. Load of other info. This is Rockett Brand 111 octane leaded fuel. But from what I read can I assume it will be the same as pump gas?

ANSWER
If leaded, its probably the same as pump gas.

QUESTION
Well I finally got around to doing some 100% VP 109 Race Gas tuning.
First pull with the race tune I have run for years was placing the A/F in the 12.0 to 12.3 range. Stoich 14.64
Went to Stoich 13.65 and got about 10.9 - 11.2
So I then went to Stoich 14.15 and now I have 11.7-11.9 so that is the number I am using.
My was tuned on winter AZ gas (oxygenated 10% ethanol). I would assume that type of mixture would have a lower stoich rating than 14.64? Am I thinking correctly?
That would explain why 13.65 was on the rich side as the MAF x-fer is probably richer than it would be on real 14.64 stoich fuel.
When I drive the car on summer gas the A/F goes to 11.0
Maybe next summer I can tune the car. Then I will have a true MAF- xfer for 14.64 stoich. Then I would bet 14.15 stoich would probably be close for the winter gas and 13.65 stoich would work perfect for the VP 109.

ANSWER
That would make sense, and I also found, that if you mix the VP 109 with any normal gasoline at all, that the stoich point comes up very quickly, so if you did not drain and flush the tank the mixing could have an effect too.

QUESTION
Do you have any experience with the 10% ethanol oxygenated winter fuels?
I know for a fact it leans my car out.

ANSWER
We are starting to get E10 in florida, I'm not sure its full blown E10 though.

QUESTION
Our retail pumps out here in CA read "Contains up to 10% Ethanol" but when I buy regular unleaded in bulk for the tanks at work (city corp yard) the bill of lading reads 5.7% Ethanol. So it seems that even then, at least here in CA, it's hard to tell exactly what it is you are getting at the pump. I guess it would be safe to lean on the high Ethanol content side. Maybe a conversation with the gas station owner would come in handy to find out what the mix is.

What I'm worried about is I've ran the Cobra hard as hell with different mixes of fuel never considering this point. Anybody know what the stoich point of VP Street blaze 100 is? They don't list that info on their site but that is what I've mixed pump gas with every time I've gone to the track.

ANSWER
I also heard that if the fuel is labeled up to E10 then it must contain at least 5.7% ethanol, with shortages of Ethanol in some areas, and now the lower price of gasoline, it would make sense for them to be mixing in the minimum amount. I did not know there was actual paperwork with the percentage though, I wonder if you'll get any batches with high %s. Any chance your city is interested in MPG or speed limiter tunes?
I'm guessing the VP 100 is close to 14.6, if you call and get the right person they can tell you, I have some of that here in cans but have not played with it.
I was recently approached with some special un-leaded high oxygen race fuel that claims no tuning required for their lowest grade, I am very leary of it and the company has yet to provide any data. If it has oxygen in it, its most likely going to lean you out unless other chemicals have been added to push stoich back up (which can be done to an extent, I recently saw specs on a race fuel with 14.8x stoich point).

QUESTION
Whats your opinion on Torco accelerator?

ANSWER
It works well.
Each of my posts is a sincere attempt to correlate & compound the collective knowledge of this community for the benefit of myself & all Mach1 owners who read these pages today, and in the future!
Welcome all Mach1 enthusiasts were glad your here! Jump on in and spread all the knowledge you can.Rockxtreme


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