Question on Petrol Grade For Esprit?
Discussion
Can a 1986 Esprit Turbo non HC be run on 95 ron unleaded without any adverse effects on the engine? If it cannot be run on 95 ron UL what can it be run on & can the head be easily modified to take unleaded?
Regards Mike
Mike,
The basic physical difference between an engine which is compatible with unleaded fuel and one that is not are the valve seats.
Leaded engines typically had brass or bronze valve seats (soft metal). Thses allowed a better seal with the valve head and were further lubricated and sealed using tetraethyl lead. This lead is not naturally present in gasoline and was actually added during the refining process.
Un-leaded engines substituted hardened steel valve seats which don't need the lubricating or sealing properties of soft metal seats.
The 907 engine uses steel valves seats so, you're good to go. You should try to use the highest octane rated gasoline possible as this will raise the threshold of detonation in the high compression environment of the turbo and alloy pistons and liners. Hope this helps...Happy Motoring! Jim'85TE
1984Turbo said: Hi Lotusguy
I have pondered the question of leaded Vs unleaded myself. My manual says the 2.2 turbo engine is the 910. Does this engine also have the steel valve seats? I mix leaded and premium unleaded together. Is this advisable or am I doing damage to the engine?
Regards
M
M,
You are quite technically correct, you do, in fact, have a 910 engine. But, whether a 907, 910 or 912, the engine is basically the same.
The 907 engine is the original 2.0 litre version and was used in the 'new' Elite and Eclat in a front engine configuation and in the S1 and S2 Esprits in a mid-engine layout. Additionally, this engine was used in the Jenson-Healey in a front engine design. All were carburetted and naturally aspirated.
The 910 engine is the 2.2 litre turbocharged variant which basically used a different crank and pistons to achieve the additional displacement, and was used in the Esprit Turbo and the HC and HCI Turbos.
The 912 engine is the N/A version of the 2.2 litre engine and is used in the S3 Esprit, which again was carburetted and naturally aspirated.
But, as I said, they are all basically the same engine. I quite erroneously lump them all together as 907s, perhaps I should modify my habit to say 9xx engine.
Anyway, back on point, the purpose of switching to unleaded gasoline initially was to allow for the use of a catalytic converter to reduce HCs and NOs. The lead oxide produced in an engine using leaded gas will react with the catalyst (usually Platinum and porcelain ceramic)in the converter and reduce it's effectiveness and lead to premature failure. Later, it was realised that using leaded gas causes the release of lead oxide into the environment, adding to the reasons for eliminating it's use.
Your 2.2 litre 910 engine not only has steel valve seats, but also has a catalytic converter, so using leaded fuel is not necessary or advisable. It will cause catalytic converter failure (or fire from the increased operating temps) and reduce the service life of your spark plugs for the sake of little noticeable gain. Just use the highest octane unleaded fuel you can find and you'll be fine. Happy Motoring! Jim'85TE
>> Edited by lotusguy on Friday 28th March 08:08
>> Edited by lotusguy on Friday 28th March 08:11
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