Running 91/95/98 Octane - Will A Tune Remove The Flexibility

[cujo_r33]

Hey Guys,

Just had a quick question about the FG XR6T's ability to run either 91, 95, or 98 octane without an issue. I love this feature, because I can run around town on 95 (to save $), and just fork out for 98 when I know I'm going to the track, on a cruise, etc.

If I get a tune (SCT Xcal or alike) will I lose the ability to do this, I.e. will it be tuned to one specific fuel? If so, why is this? How does the stock car manage it anyway and why can't a tuned car do the same?

Thanks!

Caleb.

[Paulie2256]

The most common purpose of tuning is to have the car performing to an optimal level with the supporting mods. To reach an optimal level most will tune to 98 because of its knock resistance properties.

If a car is tuned to 98 and you use 91 or 95 the engine will most likely detonate because of the lower octane rating. (PCM is expecting one fuel but you use another)

A stock car has been tuned to be able to accept all three fuels and that is why we see very good gains when getting a retune.

A car can be retuned on all 3 fuels but gains will not be as great so many don't bother.

Saying all of this, you can store multiple tunes on an xcal, so the answer is yes. You could have a 91, 95, 98, e85 etc (up to 10) tune. You will just need to re-flash the PCM every time you change fuel.

Edited 11/08/13 08:35 AM by Paulie2256

[matsfgxr6turbo]

how much would you save on a tank anyway its bugger all 98 is the go for the $2.50 or so it costs extra

[fordomatic1]

$2.50, yeh right, extra 18cents a litre for 98 here in Canberra. with a 75 lire tank that's an extra $13.50 per tank.

I run 98 in my car because it is tuned for it. Even before the tune I ran 98 because it is the best thing for it.

It's definitely not cheap to do it.

[cujo_r33]

Thanks for the info, Paulie. Once tuned, can it ever be reverted back to the standard tune, e.g. for resale, or is that lost forever?

[discostig]

98 tune with a suss fuel tune for long drives when I can only get 95. Have used that once in 3 years but glad I had it.

[matsfgxr6turbo]

16c more than 91? whats the fuel economy like on 91 I imagine its not very good I can get 500kms a tank out of my tuned fg running just over 300rwks what does your get on 91?

[XtRmn8]

Who puts 91 in their XR6T?

[Paulie2256]

Thanks for the info, Paulie. Once tuned, can it ever be reverted back to the standard tune, e.g. for resale, or is that lost forever?

Yes you can return it to stock tune.

[Wenier]

To add to Paulie's answer, you can return to stock. But if you have changed injectors and other bits those mods also would need removing to make it run correctly on stock tune. (especially the injectors).

Depends on your plans for the vehicle.

I have my ute tuned for 98 but have a 95 tune in the xcal incase I end up somewhere without 98 and need to fill up.