Lead replacement petrol going off the market.

[snafu]

I am sure this has been debated many times, but I have recently learnt that our lead replacement petrol is being discontinued this year.

Should I be worried or should I look at using an additive? If so, which one?

[richardw]

I'm not sure if the problem of valve seat recession from using unleaded fuel affects the Lotus 900 series engine - can anyone comment? The main requirement is for high octane petrol, and I don't believe there are any plans to withdraw that (just yet anyway!)

ATB Richard

[amarshall]

900 series was designed with the US market in mind, so already has hardened valve seats.

Octane rating is the issue, although I run mine on 95 RON most of the time for cost reasons.

As for the increasing ethanol content - most of the fuel system seems safe, but there's a couple of components that we haven't been able to get information about. Details are in the 10% ethanol thread.

[STELL]

As i bought my Excel, i asked the Lotus factory the same question , and got the same answer as Angus wrote.

Do not worry about unleded fuel, But the Engine was tuned to run at maximum octane in our cars.
And here in Sweden we have less ethanol in 98 octane then in the 95 octane.
Modern cars with catalystic converterers change the ignition according to the fuel it uses to to optimize the function of the converter.
Our old school carbs don't do that, so either you run at as high octane as possible or preferbly retune the carbs for the octane you are to use.
Usually Another sparkplug and a few degrees at the ignition will do the job for you.

[richardw]

I think signals from anti-knock sensors dynamically adjust the ignition to avoid knock, not the cat. I understand these can't easily be retrofitted to the Lotus engine.

ATB Richard

[fueltheburn]

Ethanol added to fuel raises the oxygen content available as well.
The added oxygen content effectively leans out the mixture and makes for a cleaner burn.
At least in carbs you can change the jets to a larger jet to compensate.
Strangely also the ignition may be retarded to gain power!! All to do with the specific gravity of the fuel and how the flame front propagates.
Ethanol in a fuel tends to make the specific gravity lighter.
This website explains things fairly well

http://www.aaoil.co.uk/products/racing- ... c-gravity/

Choose your fuel station and fuel of choice and then get it rolling road tuned to adjust to that fuel and all is well or at least optimised.