WHICH PETROL ?

[PYNEY]

hi all

what ptrol are you guys using in your V6 2.9 SC3
i've been using normal unleaded because of the age of the car and thinking no extra power gains ?
but reading steve heaths bible it reccomends super unleaded to get a few more bhp
i guess shell does the best quality fuel

cheers keith

ps 3 weeks of ownership and enjoying it

[xkr Giles]

Shell V is the best stuff, but I also had my timing adjusted and fuelling re-mapped on a piggy back chip, so I saw benefits as part of a package

[Barkychoc]

Shell definately, the V8S doesn't run as happily on other makes of super unleaded.

[The Lukas]

Taking you engine isn't modified, I don't think there is much difference (if at all) whatever you put in, as long as it's 95+. Chances are the ECU will be 'mapped' to 95 like most other cars so putting in 98 or higher won't do much at all (save a few more pops and bangs).

[Last S4]

My "day" car is a Range Rover Sport 4.2 V8 Supercharged and I can tell the difference straight away if it has been fed normal unleaded. Since finding this and buying the S I only use the higher grade gear in both.

[The Lukas]

Last S4 said:

Range Rover Sport 4.2 V8 Supercharged

I believe that is part of the reason. With forced induction, detonation will occur sooner, higher octane fuel slows it down. I'm no expert but that's my take on it

[jimed]

From memory the S3C has an ECU which compensates for 95 petrol so you can use either (the Steve Heath book gives details of the ECU that does this so you can check it easily enough - my S3C did have it fitted). My old S3C did seem a bit sharper on the super but it went fine on the 95 as well. The biggest improvement was in getting all the ignition side working well - new plug leads, and so on as well as the timing and that all made a bigger difference to the smoothness and go than the super ever did. Result was that I used 95 if just on the mway or similar but for some more challenging roads some super was good so it up to you.
Jim

[Chris71]

Octane-wise a standard engine shouldn't be able to tell the difference. It'll only be if your engine has an after market high octane map that you could have problem with 95 RON. However there are all sorts of other additives in high performance fuel these days that may well be absent in the super market stuff.

[Barkychoc]

On the V8 the use of super unleaded allows you to have the ignition timing set at 10 degrees BTDC, to use standard unleaded you have to retard the timing to 4 degrees BTDC compromising on both performance and economy.

How do you set it for unleaded on the V6 - isn't there a plug that you fit on the end of a lead according to whether its unleaded or 4 star / equivalent?
I'm going back to 2 litre EFI sierra days that had EEC IV engine management and thats how you did it on that IIRC.

[ketvrin]

Barkychoc said:

On the V8 the use of super unleaded allows you to have the ignition timing set at 10 degrees BTDC, to use standard unleaded you have to retard the timing to 4 degrees BTDC compromising on both performance and economy.

How do you set it for unleaded on the V6 - isn't there a plug that you fit on the end of a lead according to whether its unleaded or 4 star / equivalent?
I'm going back to 2 litre EFI sierra days that had EEC IV engine management and thats how you did it on that IIRC.

Yep (what a memory )

the 86GB 12A650AC ECU is mapped for 98 RON, and the 88BB 12A650JA is mapped for 95 RON

You need to further retard ignition from 8 deg BTDC to 12 deg BTDC (86GB ECU) or 12 deg BTDC to 15 deg BTDC (88BB ECU) to use 97/98 RON fuel
You need to find the Octane Adjustment Plug in the loom under the dash - its the lead with the Red Cap.

To retard the ignition you need to "earth" these wires...

4 degrees = BR/R
6 Degrees = BR/BL

to increase idle by 50-75 RPM earth the BL/Y

HTH

K

Edited by ketvrin on Monday 23 August 16:01