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Old 28-05-2006, 10:39 PM   #1
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Fuels

Found this - might be useful when choosing what fuel to run yer race boat on. Tested on a golf gti on a rolling road:
Shell 95 205bhp 234lb ft
BP 95 204bhp 242lb ft
Shell Optimax 209bhp 242lb ft
Tesco 99 212bhp 242lb ft
BP Ultimate 212bhp 252lb ft
Sunoco Race Fuel (352.5p/litre!) 218bhp 248lb ft
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Old 28-05-2006, 11:02 PM   #2
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When fith gear tested Shell Optimax, BP Ultimate and normal 95 unleaded it was Opti that came out on top by a clear margin. They used a shopping car, a Golf GTI and a Scooby Turbo. In the shopping car all the fuels produced the same power but in the other 2 the higher octane fuels made more power with the biggest difference seen on the Scooby and the best power being made by Opti in both cases.
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Old 29-05-2006, 05:27 PM   #3
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Most basic engines typically dont use the higher octane. High compression or high performace engines with knock sensors will.

Running on lower quality fuel the EMS will retard the spark - retarding performance.

Also - Petrol quality varies greatly from place to place. Octane 'evaporates' with storage - this is a *fact*. Low turn over sites when tested were THREE to FOUR octane lower than the in -town sites with high turnover, and they were one to two octane below (R/M)*2.

For best quality race fuel, ask the distributer when they will be delivering petrol to your area on the day before your race... Tell them its for racing - they understand. Then go to the garage, and ask which is their lowest level high octane tank and what time delivery for that tank is. Then arrive with the delivery truck. Then you will get the high octane fuel you have paid for!

( and my fuel was tested by the scruteneers at Littlehampton immediately after the race, and it was legal! ) It was also very very fresh, less than 36 hours old!

Some things to remember:
Some petrol has a higher calorific value than other petrol of identical octane. This will give more power in every instance. It may be better to run a lower octane petrol of higher calorific value if you are not going to benefit from high octane.

Some high revving cars will not benefit from high octane

Tuning your petrol to suit your car/engine *will* give you more power than just choosing one supplier. For example, filling 20 litres of TEXACO 92 and 10 litres of TESCO 99 will give you 94 octane, but with a higher calorific value than most standard 94 octane pump fuels!
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Old 29-05-2006, 11:13 PM   #4
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You can also make your own racing fuels ,with a high octane .
you have to buy a good racing fuel with a high octane ,and or high caloric value.(1 liter is fine)
Let it inject into a gas chromatograph (company,s that produce or sell thinners for paint etc have those machines)
Also let them inject normal gas ,so you have something to compare,and start with .
All the extra stuff ,probably : mtbe ,alcohol,tolueen ,etc can be bought ,only you have to weight all the extra stuff that goes along with the normal gas to make a certain amount of racing fuel.
All the other stuff thats needed to make good racing fuel is cheap in comparing to race fuel.

most people think that with avgas 100 LL you make more power,actually the caloric value is lower than 98 pump gas,so you probably make less power ( if you do not raise compression)

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Old 30-05-2006, 03:30 PM   #5
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On older engines its not an exact science either, I now have a westfield with a 1700 crossflow in it and that hates any of the "super" fuels and just runs like sh*te on them. I used to have a mk2 escort road rally car with a virtually identical spec engine in it and that used to love them, to the extent that you could feel the difference, not in out and out power but in the way the engine ran, made it feel a lot less cammy.
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Old 30-05-2006, 03:45 PM   #6
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Quote:
Originally posted by wasonlydoing10knts!
On older engines its not an exact science either, I now have a westfield with a 1700 crossflow in it and that hates any of the "super" fuels and just runs like sh*te on them.
There is a load of stuff about some lower octane fuel having higher calorific value. The issue is advanced ECU's and modern engines cant use the lower octane, as they are designed around the octane, not the power.

The lower octane almost always has more 'bang' - it is the higher octane number that reduces the bang.
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Old 30-05-2006, 04:40 PM   #7
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Yes, I wondered whether it was that, but I'm puzzled why two almost identical engines should be so different. The only things that are different are the make of various parts, but should all be to same spec and a bit of tweaking to the fuel map to suit the lighter car.

The compression is reasonably high and the escort would start to knock under heavy load on standard u/l. Suppose the westfield only weighs about 1/3 of the escort though.

I've found the best solution is proboost for track days etc. I did get 5 gals of works "pump grade" (ha!) rally fuel from Msport and it ran perfectly on that, so did the lawn mower after the wife topped it up with it - mowing the grass was like glue sniffing though!

All in all i'm not complaining as the car seems to have ceap tastes!
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