Super Unleaded

[Andy Checkley]

I have a K Series VVC that I sometimes do trackdays in. Is there any benefit in using Super Unleaded for trackday use?

 

Any thoughts welcomed.

[Andrew Russell]

My Seven is a 2.0L 16v Vauxhall giving out about 210 bhp, rather than a K series VVC, but having used unleaded fuel of 95, 97 and 98 have to say that personally little difference has been noticed. I tend to use what I can get hold of but make sure that it is regularly filled with SUL, just in case.I like to hedge my bets! Perhaps you should try the different grades and see what best suits your set up.

[Tim Seipel]

You can use any unleaded fuel in the the rage 95, 97 or the old 98 RON with any of the standard or supersport K engines. However, for track use 97RON is preferred for safety. VVC is fine on 95. In fact most of the calibrations or tunes as some know them are actually done on 95 reference grades of fuel. So, actually you don't gain a thing using the higher octane pump fuels just a bit of safety margin to the detonation border line.

You can trust me, cos' I did most of them.

[Andy Checkley]

Thank you both for your help and advice.

 

It was primarily the well being of the engine I was concerned with. If using the higher octane fuels will give the engine an easier time, I think its worth the extra few pence per litre.

 

Any other thoughts on this subject out there?

 

Regards, Andy Checkley

[Vogon SuperTrooper]

What about older models? I have a 91 xflow, worked on by Roger King to 1.8l. There was some concern about the space available to put in new valveseats so I'm running on Millers VSP and super unleaded. Is this wrong?

 

thanks

c

[CHRIS CLARK]

Originally I thought that SU/L was the best way to go.I think now that with the lower octane rating it's been given it can be classified as an 'earner' for the petrol companies rather than a wonder fuel! My K series (non-cat) has run on both SU/L and regular U/L and for road use I really can't tell the difference. All tastes like butter to me!!!!!!!!!!

[Dartmoor7]

Tim Seipel wrote:You can use any unleaded fuel in the the rage 95, 97 or the old 98 RON with any of the standard or supersport K engines.

Does this apply to 1.4 Supersport and early 1.6 Supersports which were the only K engines to be specified for 98 octane fuel in Caterham brochures,etc.?

[simon]

Suprisingly the very nasty nature of super U/L has stopped most supermarkets from stocking it. i.e. its stupidly carcinogenic (lots of benzine) and its extremely flammable. Thats also why there are so many vehicle fires these days. Not like good old leaded that never did any harm!

[Vogon SuperTrooper]

Blimey. What else don't we know?

Or do you all and I'm the ignoramus?

[Mike Bees]

Blimey, I'd always thought that good old leaded petrol was pretty flammable.

 

Mike

[Jules Martin]

If any of you guys still "crave" for leaded fuel and live in the T. Wells/Tonbridge area,

I know where you can get it (legally !)on a standard village garage forecourt.

Jules

 

 

[Tim Seipel]

Just to clarify the situation on SUL fuel before you all ring Jez for an explanation.

 

98 Ron was specified on engine safety grounds especially for track and racing use. For pottering around 95 Ron is fine. Don't forget 95 Ron after all is not exactly "what it says on the tin". It is the minimum RON value the fuel must be and quite often was more like 96 or so.

98 SUL is nasty stuff though. It's your choice!!

[simon]

If anybody wants to get some leaded fuel then have a look at :www.bayfordthrust.co.uk

They have the licenses to sell four star.

.......on a side note, if anyone wants to donate me a k-series engine and box then I would be happy to take it off their hands :-)

 

[CHRIS CLARK]

Simon, Speak nicely to BMW (or 'Alchemy') & they may let you pick one up for free!!!!!!!

[PETER MUMFORD]

Jules

So wheres the 4* petrol in Tonbridge/TW?

Peter

[Jules Martin]

Peter,

 

It's at the "Goudhurst Service Station" - the Roller & Bentley dealer on the road from the A21 (just North of Lamberhurst) to Goudhurst, next door to the "Green Cross Inn".

 

 

[V7 SLR]

Someone mentioned that SUL was the cause of many engine/car fires..... Rubbish. All petrol grades burn at the same rate. Increasing the octane rating only reduces the petrol's propensity to self-detonate. Once detonated, it burns as fast as all other petrol grades.

 

The reason for using SUL on the track, and the reason why some higher performance cars have to use SUL all the time (my SLR for example) is because high revs, high compression ratios and/or high interal engine temperatures will cause lower octane petrols to self-detonate. All these conditions are more likely when a car is used on a track.

 

When a fuel detonates in a cylinder, it is supposed to have one flame front eminating from the spark plug and moving towards the piston, pushing it down as it (the flame front) propagates. If petrol self detonates it will as likely have several flame fronts, all bounncing off each other and the cylinder wall. This is what pinking is.

 

There's a superb article I got from somewhere ages ago about fuel grades as used by hot rodders in the US. Anyone wants a copy, email me direct. It's too long to paste here but definately worth the read.

[Slipper man]

I don't know how to E-mail direct, but I'd love a copy (secretary@lotus7club.co.uk)

[Steve J]

This topic is going to burn for ages (ha, ha, ha)....

 

...firstly, the piston isn't moved down the cylinder by the flame front, its moved down the cyclinder by the extremely high in-cylinder pressures as a result of combustion.

 

Secondly, the 'pinking' noise heard when detonation occurs isn't created by flames fronts hitting each other...

 

When ignition in a cylinder occurs, a flame propogates from the source of ignition (hopefully the spark plug - if not then you've got problems or a diesel). As the flame approaches the edges of the combustion chamber, the pressure/temperature in the cylinder have already risen dramatically. If the pressure and temperature are high enough (usually by high engine loads), the remaining 'pockets' of charge will self ignite. The high temperature and pressure cause these pockets to burn extremely rapidly, and they burn almost as if they were burning under constant volume conditions, with the existing flame front and the cylinder walls and/or piston acting as the boundaries of combustion, the relative rate of volumetric expansion is small, therefore an extremely high pressure is produced. This high pressure wave causes vibration in the cylinder walls, etc and is heard as the 'pinking' noise.

 

Detonation also occurs in Renault 11 1.4l engines when driven under light engine loads at 70mph heading south on the Autobahn about 35 miles north of Wurzburg in Germany, especially if a hose gives up the ghost and the cylinder head gasket blows. I should know, I have successfuully carried out the above experiment.

 

It's usually followed by dents forming in the front near-side wing. Round in nature. About the size of a fist....