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Sounds like a silly question but what fuel would you run in a factory sigma turbo? With so many different types and Octane ratings out these days I'm not quite sure. I was thinking a 98 RON fuel with a lead additive - thoughts?

when i had my original gh turbo setup in my GK GSR i ran BP ultimate 98
ran fine

You dont need a lead additive.

If you want to take advantage of fitting the turbo, you need 98, and BP seems to be the fuel of choice.

If you wish to save a couple of dollars per tank you could back the timing off a little and run 95.

Thanks guys. My closest servo is a BP so that makes it easier. Why the no lead additive - did they come out with Hardened valves or something? I've heard that the Colts in the 60's did so I've been advised to not use Lead replacement in them either. I haven't had this confirmed though.

i heard that unless you have a knock sensor, that there is no real benifit from 98

From previous experience.. if your engine is capable of running safely and consistently on 91oct, it will probably produce LESS power using 98oct or higher

However, if you raise the compression, or add boost, advance the timing etc.. something that may cause detonation and instability, the higher octane fuel is safer as it is harder to burn without a spark.


In terms of economy though, I find that premium tends to go 5-10% further on the same amount when used continuously.
Plus anything manufactured in japan is designed for 95-96oct as thats what their 'standard' is.


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Chris

EVL076 wrote:i heard that unless you have a knock sensor, that there is no real benifit from 98

With Carby turbo your ears are your knock sensor.

Unfortunately with a factory setup you have to run the timing and octane for a worst case Scenario. Like when you get up it.

I just cruise 99% of the time. 91 octane would be fine .But for that odd occasion that hit boost I need 98 to keep things together. Bit of a bummer

It would be nice to have a computer making all of the timing adjustments on the run.

If you want a decent amount of boost, 98 RON would be what you'd want. There is some places now selling 100 RON.

DragonCypher wrote:Plus anything manufactured in japan is designed for 95-96oct as thats what their 'standard' is.

Not sure about all Japanese cars, but I know the TT Supra needs 100 RON and the NA model needs 95RON.

No worries guys. I'm keeping the car factory with factory boost but will run premium 98 anyway just to be safe

i like my 98

the sigma turbo operators manual states 98, which is highlighted by the warning as soon as you open the fuel door(though octane not specified, just says PREMIUM FUEL ONLY).