not much point in in trying to encourage f3 engine cars if the 100 octane rule is inforced.

All the years i have been involved in f3 engines they have always been run with a minimum 100 octane with avgas mix or octane booster to raise it to min 102. Particularly the older engines that do not have sophisticated electronics with knock sensors

the old leaded 100 octane not now available, so fuel from specialist suppliers has been used 102 octane.

it is possible to run on 98 octane by retarding igintion which makes the engine uncompetive.

i would suggest the blue wording, pump fuel available to the general public covers the 102 octane fuel that BP sell at a number of petrol outlets.

i certainly will not be running my now f3 engined Ralt on less than 102 octane

Jim

Unfortunately the Blue Book in addition to the the definition of Pump Fuel on page 62 in The Terminology section has an Appendix 1 in the Tables section of The Termonolgy section on page 69 which I think restricts the maximum RON to 100.

Nick.

Nick

I agree, but my point is, all f3 cars run in clubf3(ARPf3) classicf3 as far as i know run higher than 100 octane fuel and always have done.
Are these the championships referred to as running illegally.
National f3 i assume has msa approval
i can not see anyone is going to run an f3 car in mono and go to the expense of remapping to run on 98 octane and risk damaging the engine and loosing horsepower.

I did intended to do some mono races if the car proves competitive with this engine, but if the club is to be dogmatic about this i will not be able to.

Jim

I don't know what Graham Read has done (our only F3 car in Formula 2000), but he is complaining of a lack of power. Partly because of the smaller restrictor (and the shape of said restrictor), and probably because of the remapping.

Until Mono gets dispensation like BRSCC F3 to run higher octane fuel, then those are the rules. I'm not sure dogma really comes into it.

Tristan

Cannot speak for Graham but if he is running on 98 octane with the map i think is in his box it suprising it is still running.

I have put my own foot in if i a had just turned up and raced, know one would have been the wiser.

My point again about dogma is why bring it up at mananage meeting was there some complaint?
It has basically any body contemplating running an f3 engine in mono , on reading about the fuel will not bother so it was pointless trying to attract them.

jim

Yes, you probably would have got away with it had to never mentioned it!

I wonder if Mono can gain dispensation for high octane fuel in particular classes or types of car. And then you get into that territory of making sure nobody else runs it either. So then we all have to start giving fuel samples. And that just costs money. And that...

Graham's engine will still run, but produce less power. And with the smaller restrictor he won't be able to use high revs - where detonation isn't a problem - as much, thus doubling his problem.

I'm just glad I don't have an F3 engine, and that managing the rules isn't my job!

Tristan

Detonation happens at low revs with full throttle openings. It is not recommended to use full throttle below 4000 rpm on a mechaniaclly injected f3 engine.
on the modern electronic engines it happens because they run at very high ingnition advance with high octane fuel if you use lower octane it cause detonation.remapping and retard ignition can cause overheating and hence detonation again

The size of the restrictor has no relavance ,except the smaller the restrictor the sooner it runs out of air causing the engine to run rich, which actually helps stop detonation because it cools the piston temperatures.

also the difference in maximum horsepower on 24 mm engine 5800rpm and 25 mm 6000rpm engine is approx 200rpm even 26 mm engines run out puff after 6200.

believe me having detonated a number of f3 engines i am almost an expert.

A works Spiess VW engine i had was actual set up run with mild detonation. They recommended rebuild and fit new pistons every 200km

I would say dont go there unless you really want to do an f3 race.

I'm not convinced of your understanding of detonation.

You can plot the detonation habits of an engine, which on a graph of advance versus engine speed looks like an exponential curve going upwards (i.e. starts low, rises slowly, and increases quicker with revs). At high revs detonation isn't a concern.
You can also plot a MBT curve (minimum advance for best torque, and not as some thing maximum best torque), which starts at low speed, increases rapidly and then levels off above about 40°, depending on the exact engine. It would be much easier to explain with a picture, but I don't have the time right now to draw one.

If these two curves cross then you have to worry - and because of the shape of this curve it's usually at medium revs (and large loads). If they never cross then you don't. The aim of a good map is to get the MBT torque as perfect as possible without ever getting into the detonation area - either by increasing the compression ratio, by retarding the ignition, or using higher octane fuel.

Retarding the ignition is safe, and is the principle knock sensor controlled ECUs usually use. It doesn't cause overheating - you are probably thinking of running lean, which usually causes the largest increase in in-cylinder temperatures.

The restrictor 'strangles' the engine so that above a certain RPM (about 6000 to 6500rpm on a modern F3 restrictor) it cannot flow any more air. It will not make it go extrarich (unless your injection map is rubbish). The engines will already be run slightly rich, as this acts as a charge cooling due to the latent heat of vaporisation and the volatility of modern fuels.

A smaller restrictor will reduce power by the simple expedient of reduce the number of revs available. It should have a lesser effect on the peak torque figure, which occurs even on highly tuned engines before the strangulation occurs.

I can believe that mild detonation is used to get more power for a very short term. It's quite a risky approach (especially without a knock sensor feedback loop) even then, because the quality of the fuel will not be totally consistent, and the octane rating will drop over time, which might be an issue unless your cans are fresh and new. Fuel stored over the winter, for example, will massively increase the chances of detonation.

The risk of pre-ignition is also massively increased with detonation (and, vice versa, pre-ignition can lead to detonation), which will kindly assist in destroying your engine.

Thanks for the piece in startline on fuel

Confirms the point i was trying to make.

The judd engine spec actually says 98 fuel but the power was 155bhp on the old lucas 3 stage ignition which was not mappable When spiess bought in bosch motronics using mappable chips 100+ fuel power was up to 170 ish.
This is as far as it went with the old style f3 engine mechaniacal injected engines.
in early 90,s mugen honda came in with full electronic engines also spiess with full electronic engine all though again the mapping was very difficult.

now we have very sophisticated ecu,s that can monitor the engines when running with knock sensors but they still detonate, ask a couple of club f3 guys.

Phil Moore might be an expert in on petrol but i am surprised he did recommend Fosters its the only time i have seen him go fast !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
By the way thanks for lesson Tristan you obviously did your theory try it in practice like i have.

not Phils dad

I have just read the Startline article as well, and I think quite a lot of it is wrong (or at least inaccurate). The difference between 95 and 97 RON might not be much, but if it's worth an extra degree of ignition advance then it will be able to give more power.

Ethanol has a LOWER calorific value than gasoline.

Methanol : ~20MJ/kg
Ethanol : ~30MJ/kg
Diesel : ~45MK/kg
Gasoline : ~47MK/kg

Mixing gasoline and ethanol to produce "bio-fuel" lowers the calorific value of the fuel. However, it does increase the octane rating due to the anti-knock abilities of ethanol. This is why it's 99 octane. At the low percentages of ethanol used, the increase in ignition advance is probably worth it, although as Phil correctly says it's not 'legal' and you'll need to put a little extra in your tank. Also beware of ethanol eating seals in your fuel system!

Phil mentions the smaller restrictor requiring the use of pump fuel. That's just nonsense - the restrictor restricts the revs, and fuel stops detonation. If people want to get decent power out of their F3 engines they need to use the 102 stuff, regardless of the restrictor size. If 102 is 'illegal' then they will have to accept a power reduction or massively unreliable engines.

I was interested to read the bit about storage. As I have no experience with long term fuel storage on any scale I have to assume he is correct. Thanks for that Phil!

Jim - doing it for a long time without knowing why doesn't mean you have necessarily been doing it right or understood why.

got that Phil you are wrong i new u did not know what you are talking about!!!!!

Well, it's the third time I've seen him say that bio-fuels have a higher calorific value than plain gasoline, and that just ain't true. You can look up calorific values in a jiffy and see that for yourself if you like.

And surely you, with your decades of F3 experience, don't believe that a smaller restrictor (which merely lowers the working rev limit of the engine) negates the need for 102 RON? If anything, you'd want even higher octane fuel to try and claw back what you've lost from having less revs.

I don't care who you believe personally. But there are two opinions, one based on easily researchable fact and another based on myth.


Edit, a couple of days later: Martin has read the startline article and agrees that everything Phil says is entirely wrong. He also disagrees about the stats thing of 95% confidence level equating to 1 in 20 people being kicked out.

It is a shame such nonsense is published by Startline, because other people might believe it.

Just an update for those that might be interested

As i suspected trying to run a f3 engine on 99 octane pump fuel my engine detonated at Thruxton, even with miller lead replacement and octane booster which if you read the net probably does not up the octane more than 1 point.Lead replace has to be run to lubricate the metering unit.

The map in the ecu is what was called by Newbridge engines, when they map it on the dyno, a safe map!!!!!!!!!!!!!!!!!.

It did not help that we held on the line for a very long time and engine temp went up to 95o,
these old f3 engines do not like anything above 75o.

So that is the end of my experiment i running an f3 engine in classic class

I'm always in the market to buy the remains of detonated F3 engines.....!!!