Blended tune on stuck ECU ?

[Deric]

My 2003 Cobra is just about finished up and I've been getting more details from the tuner. So i have a few questions for you guys.

In my area, the best fuel we can get is 91 octane so I had the car tuned for that. I know, it's not ideal but it still put down 734 whp. I also requested a tune for VP MS109 for when I get the urge to go fast.

Anyway, on my previous build, I had a dial switch mounted in the center console and I simply turned it to whatever tune (1-10) I wanted with regards to the fuel I put in and which pulley I was running. My current builder just informed me that I no longer have to do that because both tunes are now a single blended tune on the stock ECU. There is no longer a need for a dial or any need to switch tunes. Simply switch fuels and swap the pulley and go. It is supposed to be smart enough to sense the change and make the adjustments on it's own.

I don't doubt their competency, but for my own piece of mind I would like to get some information on how this works. Maybe this method has been around and I just don't know about it, which is highly likely too. But it makes me a bit nervous to fill up with a different fuel and swap a pulley and call it good. Being a "blended tune" also raises the question of whether or not one of them is a compromise or "less safe."

Anybody have experience with this, or links to more information?

 

[cj428mach]

Time to find a new tuner.

 

[MalcolmV8]

Time to find a new tuner.

No kidding.

 

[s351]

Your tuner is an idiot. I know cars can adjust to e85 and gas mix. But I've yet to hear about that for straight gas. Run the car the same way you had it on the dial. How is the car detecting the fuel octane and then adding timing for the race fuel.

 

[Deric]

Hold on, let me try to explain this better. I'm not entirely sure on this topic, that's why i am here asking.

Ok, so the way it was explained to me is that the computer is supposed to be able to sense when I swap the pulley by seeing a change in several parameters. I was told that when it sees that the car is running my 3.4" pulley, it will ASSUME I have the correct 91 octane in the tank. When I swap to my 3.1" pulley, it will ASSUME I have MS109 in the tank, and run accordingly. So it cant directly read the fuel, it assumes based on other parameters.

I guess my main objective here is to learn more about how this work on these cars. I've never heard of this method but they say it's the better way to do it. I guess it makes sense that it would be safer than forgetting to load a tune with a handheld, or forgetting what fuel you put in last time. I just want to learn more about it cause it makes me a little nervous at this point.

 

[MalcolmV8]

Our ECUs have no way of sensing or assuming octane. My guess is your tuner dialed the car in with the smaller pulley and told you it's safe to run the larger pulley too. That much would be correct because the larger pulley will just use less air and not go as far up into the MAF curve.
Your timing tables would be static though. I suppose your tuner may have looked at load with the larger pulley and set up timing accordingly and then in the timing table for loads above that increased timing knowing you'll be on a smaller pulley to get there with a better fuel. I've never personally done that but it sounds like it would work.
In any case the ECU's not sensing or changing anything but possibly doing what I just described.