Rule question on fuel.

[verytricky]

As far as I understand, we can use any fuel from a public garage? So if tesco starts selling 100 octane fuel, we can just go and buyit and race with it and be legal? ( tesco is introducing a high octane fuel in the next months. I have a sample( 20 liters ) and it is supposed 100 RON octane.)

Then the second part of the question: If I were to say half fill my boat with LRP and then fill up with 98 octane, then the fact I mixed the petrol would not make the petrol illegal provided both parts of the petrol mix were avalable from a public service station?

I would like some opinion from those who know the actual rules.

[Ben]

Go to the UIM website. Offshore rule 504 explains all.

[PRINCE CONSORT]

Why bother soddin around mixing fuels, just run on avgas like we did in the old days. When was the last time you heard of any boat being fuel tested or post race scrutineered for that matter. Also Tricky you are letting people know you are up for a bit of cheating with questions like these.

[doug]

[W When was the last time you heard of any boat being fuel tested or post race scrutineered for that matter. Also Tricky you are letting people know you are up for a bit of cheating with questions like these. [/QUOTE]

First second third at every world and european championship ive ever been to.

[Johnny Rocket]

Originally posted by PRINCE CONSORT
Why bother soddin around mixing fuels, just run on avgas like we did in the old days. When was the last time you heard of any boat being fuel tested or post race scrutineered for that matter. Also Tricky you are letting people know you are up for a bit of cheating with questions like these.

Seems to me you may be judging people by your own standards - or lack of them

The way I read it, Tricky was wanting to make sure he kept the right side of the rules.

[verytricky]

Originally posted by PRINCE CONSORT
Why bother soddin around mixing fuels, just run on avgas like we did in the old days. When was the last time you heard of any boat being fuel tested or post race scrutineered for that matter. Also Tricky you are letting people know you are up for a bit of cheating with questions like these.

Ummmn - I am trying to make sure that I do it LEGALLY. Unlike quite a few other racers, I want to win one day within the rules. I have tried to make sence of the rules, and failed.

My reasons for asking about the fuel is obvious to people who understand RON and how it actually works with the correct - standard volvo ECU, and *why* a higher octane petrol is better for performance. What may not be obvious is the effect of mixing a LRP petrol with a leadfree high octane petrol. The result of the correct mix is a higher octane petrol, and I will be testing the combinations with an engine dyno to determine the best mix for the specific engine. The result could be as much as 1/2 a mile an hour top end.

With the correct sparkplug and gap, the correct engine oil / oil level and the correct leg oil, with a cleaned bottom of hull on the boat, I can get as much as 2 mile an hour over the previous top speed, all completely legally and fully within the rules.

What is not clear to me is the issue of mixing fuel types.

If they test source fuel 1, it will be legal, If they mix fuel type 2 it will be legal. - If the test the blend, it will give a higher octane reading. They would have to test the two fuels seperately, confirm they are legal, then mix them, then compare their mix to my race fuel. The rules do not appear to allow this to occur.

Finally - I WILL be racing up to SIX European events in 2006. I do intend to be in the top three boats, so I am almost guaranteed to get my fuel tested, especially when I will be faster than most of the other boats. I do not want to get into trouble for dodgy fuel unless I can establish that mixing legitimate fuels will be understood and tested according to its constituent ratios.

Does this make sence?

[JamesM]

Can you still get LRP? I haven't seen any for a while now, not that I've really looked.

[JamesM]

Originally posted by verytricky
What may not be obvious is the effect of mixing a LRP petrol with a leadfree high octane petrol. The result of the correct mix is a higher octane petrol

So are you saying that if you mix LRP (95RON, I think) with say Shell Optimax (98RON) you would end up with a higher octane fuel than 98RON???

[Wayne Kerr]

Blimey This is getting "In-ter-esting"
More please

Mike K.
Please don't look here anymore !!!!!!!!

[verytricky]

Originally posted by Johnny Boat Dude
So are you saying that if you mix LRP (95RON, I think) with say Shell Optimax (98RON) you would end up with a higher octane fuel than 98RON???

Simple answer - yes. The characteristics of the petrol will be closer to 100 RON.

I am unsure if the RON measurement will show 98 RON or not, but using the MON standard, which is using a higher rev, hotter temperature loaded engine, the detonation point will move upwards, ie a higher MON rating.

The ECU that is installed in the V24 detects what type of reaction the fuel is giving, and advances or retards ignition. Given the mixed fuel the engine responds by changing the ignition point, reacting to the characteristic of the fuel to detonate less, or the 'increase' in the octane rating. This affects the power produced.

Octane is only the resistance to knock.

The real power comes from the burning speed and energy value of the fuel - Burning speed is the speed at which a fuel releases its energy. In an engine there is actually very little real time for the fuel to release its energy. The pressure in the cylinder should peak around 20 degrees ATDC. If the fuel is still burning after this, it is not actually contributing to engine power. Energy value is obviously important as it supplies the power. You gotta balance these things up.


So the ratio of the mix affects the reaction you get - thus the power produced..

I have been given a start point, and I need to work it from there...

Remember RON and MON are different. a 90 RON is about 80 MON. Most pump petrol is labelled as (RON + MON)/ 2.

So if you had 90 RON petrol this would actually be labelled as 85 at the pumps.....

[Matt]

I thought octane number was a measure of burn rate. So the LOWER the number, the quicker the burn rate. Therefore, for max power, you actually want the lowest RON you can run without pinking or detonation. I high compression motor requires higher octane since cylinder temp & pressure is higher and therefore more detonation prone.And running a higher octane than you need is detrimental to performance. I appreciate this is contra to common thinking - so I'm probably wrong - but would grateful if someone could explain to me why.

[jw.]

Isn't that what Mr Verytricky is trying to do? Since his engine management responds to the onset of knock, with a higher octane fuel it can set it alight earlier so it reaches a higher maximum pressure before is begins to be wasted on the down stroke.

I'd never given the over octane rating a thought though. Interesting that.


Edit. Oo..er do you mean cos it's going to burn more slowly after it has been ignited, why bother?

[JamesM]

Originally posted by Matt
I thought octane number was a measure of burn rate. So the LOWER the number, the quicker the burn rate. Therefore, for max power, you actually want the lowest RON you can run without pinking or detonation.

A slower burn would equal more torque would it not?

[Matt]

I can see where you're coming from, but I don't think it would.

[verytricky]

As far as I know.....

Octane measures the resistance to knock. It does not measure burn rate. There is however a clear path linking octane to burn rate, but the burn rate of two identical octane fuels can be different. In fact they are different between the 'green' petrols and Shell's petrol of the same octane rate.

RON is usually 10 points away from MON. But not always. Sometimes RON and MON are closer, and these petrols burn 'faster' when ignited. Some petrols have a 'gap' between RON and MON of around 20, and actually burn slower.

As my engine revs at a maximum of 5000 RPM, I do not have to worry that much about burn rate, but those who race at 8000 RPM, the burn rate is imprtant.

So in essence: Burn rate is the speed the fuel ignites, and Octane is the resistance to pre-ignition.

[JamesM]

Originally posted by Matt
I can see where you're coming from, but I don't think it would.

Think of the crank as a series of levers on a shaft and the con rods as the force acting on these levers. When a piston is at TDC the crank/lever and rod/force are in line. As the piston travels down the crank rotates and the angle between the rod/force and the crank/lever increases and so the leverage on the output shaft increases. The slower the burn the longer the force acting on the lever lasts and thus the greater the angle achieved by the leaver whilst the energy is still being expended. More leverage on the output shaft equals greater torque produced at said shaft.

What do you reckon, complete bollox or not?

[verytricky]

It took me all day to get my head around the burn. Dont ask me mechanics as well!

Basically - all fuels are not equal. Some have a higher calorific rate, some a faster burn rate - all in the same PON rate ( PON = Pump Octane Number or (RON + MON) / 2

Some engines rev higher than others. Some have higher comression than others, some generate more internal heat.

All these factors affect the effect the fuel has on the engine. The primary idea is to get ignition at the point so that maximum power is generated by fuel burn before the engine advances 20 degrees from TDC.

As fuels react differnetly, testing the effect fuels have in your specific engine will give you a specific answer. There is a tested difference between shell optimax and BP Ultimate, with Optimax suiting the turbo charged high rev engines and Ultimate suiting the big cc lower rev engines. Why? They are identical octane? Their burn characteristics suit the specific engines. The difference of petrol selection can be as much as 6% in power. ( measuring this on a dyno is an issue apparently due to the way dyno's report he power produced, Something like there are only 256 steps in power it can show and on a 500 HP max dyno this means it can only show increments of 2hp or something...)

Getting wierd again. That is why I am getting expert advice and a whole day engine testing, with a blend of my favourite fuels!

[Matt]

Force is still being applied on the downward stroke regardless of burn state - even if all the fuel has fully burnt, it's still a big hot swirling mess pushing down on the piston. So the sooner you can apply maximum force, the greater the brake mean effective pressure.

Naturally, max torque is affected a good amount by cylinder pressure with the piston half way down the bore - but irrespective of a fast or slow burn, for a given amount of energy being produce by the fuel burning, this will have more or less the amount of torque because the cylinder pressure will be the same.
(I think we can neglect cooling of the charge and associated pressure reduction over such a small period)

So, I think complete bollox is unfair, and I reckon you're on the right lines, but not quite there.

Originally posted by Johnny Boat Dude
Think of the crank as a series of levers on a shaft and the con rods as the force acting on these levers. When a piston is at TDC the crank/lever and rod/force are in line. As the piston travels down the crank rotates and the angle between the rod/force and the crank/lever increases and so the leverage on the output shaft increases. The slower the burn the longer the force acting on the lever lasts and thus the greater the angle achieved by the leaver whilst the energy is still being expended. More leverage on the output shaft equals greater torque produced at said shaft.

What do you reckon, complete bollox or not?

[Matt]

This is quite interesting Mr Tricky - I will be very interested to see what results you get.

Originally posted by verytricky
It took me all day to get my head around the burn. Dont ask me mechanics as well!

Basically - all fuels are not equal. Some have a higher calorific rate, some a faster burn rate - all in the same PON rate ( PON = Pump Octane Number or (RON + MON) / 2

Some engines rev higher than others. Some have higher comression than others, some generate more internal heat.

All these factors affect the effect the fuel has on the engine. The primary idea is to get ignition at the point so that maximum power is generated by fuel burn before the engine advances 20 degrees from TDC.

As fuels react differnetly, testing the effect fuels have in your specific engine will give you a specific answer. There is a tested difference between shell optimax and BP Ultimate, with Optimax suiting the turbo charged high rev engines and Ultimate suiting the big cc lower rev engines. Why? They are identical octane? Their burn characteristics suit the specific engines. The difference of petrol selection can be as much as 6% in power. ( measuring this on a dyno is an issue apparently due to the way dyno's report he power produced, Something like there are only 256 steps in power it can show and on a 500 HP max dyno this means it can only show increments of 2hp or something...)

Getting wierd again. That is why I am getting expert advice and a whole day engine testing, with a blend of my favourite fuels!

[Mark75H]

Calorific qualities of various grades of petrol are too close to say there is a difference.

Neither RON nor MON nor how far apart they are has anything to do with flame speed or burn rate ... but a wide spread or close spread can greatly affect how well a particular fuel works in a highly critical motor like a turbo'ed race motor.

Mixing 2 grades of fuel to yeild a higher octane mixture requires one of the component fuels to be so heavily leaded that it is beyond reasonable lead content AND the other component to have little or no lead and be highly "suseptible" to octane increase by addition of lead.

It is highly unlikely to find either component at a road side pump in these modern times.