Hi Guy
Please could you tell me if different fuel ratings ie. 95ron, 98ron or 102ron have a marked differance in performance to a 1400 Tipo race engine. The engine is standard except for a cam, Webber 40 DCNF single carb and a 4 branch exhaust. I know with different fule ratings you can get pre-ignition if the timing is not set properly, but how do you know where to set the timing with the different fuels, and do you have to alter the cam timing?
Gary
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Westfield
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Fuel for Racing
Thank you
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Guy Croft
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The way you select if you are faced with a choice of octanes is to pick the highest and dyno with that, setting the ignition timing to develop best power.
You can then try lower octane grades as they may be cheaper (!) but watch out for any tendency to detonation/pre-ignition.
Engine and intake air temperature, plug type, calibration and jetting all have an influence on that engine tendency and there is no hard and fast rule as to the octane you need but as a rule of thumb:
98 RON - turbocharged 18-25psi boost.
97 RON - up to full race CR 11-12/1 on twin carbs or injection
95 RON - fast-road/StI/II CR 10/1 on twin carbs or injection
It is always necessary on a competition engine to feed cool ambient air to the intake via a sealed duct, to keep the coolant and oil temperatures down. From years of dyno and testing, I say best is 75 deg C coolant (ie: cylinder head temp) and oil temp 85-90 deg C under all operating conditions. If you cannot achieve that even on the hottest race, sort your car out.
Engines with single carb are far more prone to exhibit combustion problems because of the weird fuelling distribution in the 4 branch inlet manifold and heat soak to the manifold, so use the higher octane to be on the safe side. This is true to a lesser extent with single point injection, although of course the fuel atomisation is vastly better than with a carb.
Contrary to popular thinking high octane does not give an engine more power, octane rating is merely a measure of the knock-resistance of the fuel. The higher the CR the higher it needs to be. Some say the pump fuel Shell Optimax is 98 RON, I don't know for sure. If in doubt use octane booster from a reliable source like Silkolene, Millers Oils, or Piper Cams.
GC
You can then try lower octane grades as they may be cheaper (!) but watch out for any tendency to detonation/pre-ignition.
Engine and intake air temperature, plug type, calibration and jetting all have an influence on that engine tendency and there is no hard and fast rule as to the octane you need but as a rule of thumb:
98 RON - turbocharged 18-25psi boost.
97 RON - up to full race CR 11-12/1 on twin carbs or injection
95 RON - fast-road/StI/II CR 10/1 on twin carbs or injection
It is always necessary on a competition engine to feed cool ambient air to the intake via a sealed duct, to keep the coolant and oil temperatures down. From years of dyno and testing, I say best is 75 deg C coolant (ie: cylinder head temp) and oil temp 85-90 deg C under all operating conditions. If you cannot achieve that even on the hottest race, sort your car out.
Engines with single carb are far more prone to exhibit combustion problems because of the weird fuelling distribution in the 4 branch inlet manifold and heat soak to the manifold, so use the higher octane to be on the safe side. This is true to a lesser extent with single point injection, although of course the fuel atomisation is vastly better than with a carb.
Contrary to popular thinking high octane does not give an engine more power, octane rating is merely a measure of the knock-resistance of the fuel. The higher the CR the higher it needs to be. Some say the pump fuel Shell Optimax is 98 RON, I don't know for sure. If in doubt use octane booster from a reliable source like Silkolene, Millers Oils, or Piper Cams.
GC
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Westfield
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Balidey
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Further information on higher octane fuels I have found are as follows.
AvGas100 Aviation fuel is rated at 100 Octane. If you are friendly with your local air field you may be able to source some from there. But as there is no (or I think reduced) duty on it then you are not allowed to use it on the road.
Some air fields are restricted on how much they are allowed to sell in containers (one jerry can is about the limit at my local air strip), and they also ask for the registration mark of the aircraft it's for, but a name and address usually suffice. They know that many motorbike racers use this fuel.
I have used Avgas 100 and also normal pump fuel (97 RON) with an additive (often refered to as octaine boosters) back to back on racing two stroke engines with very high compression and have noticed no difference between the two. But this is not a dyno comparison, just back to back racing.
AvGas100 Aviation fuel is rated at 100 Octane. If you are friendly with your local air field you may be able to source some from there. But as there is no (or I think reduced) duty on it then you are not allowed to use it on the road.
Some air fields are restricted on how much they are allowed to sell in containers (one jerry can is about the limit at my local air strip), and they also ask for the registration mark of the aircraft it's for, but a name and address usually suffice. They know that many motorbike racers use this fuel.
I have used Avgas 100 and also normal pump fuel (97 RON) with an additive (often refered to as octaine boosters) back to back on racing two stroke engines with very high compression and have noticed no difference between the two. But this is not a dyno comparison, just back to back racing.
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Guy Croft
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My advice regarding 100/130 aviation gasoline (Avgas) is be careful.
I think I am right in saying Avgas is a leaded fuel and thus must not be used with catalytic converters. Moreover it is illegal to use in road vehicles since it is under a different fuel tax regime. It also has lower volatility than mogas (motor gasoline) which could conceivably cause fuel mixing and distribution problems. I am sure a bench dyno back to back test on a high powered engine would show this up in an instant.
The rating 100 incidentally is the MON rating not RON; I don't know the direct equivalent from memory but probably way higher than any RON available elsewhere. 130 is a special aviation engine rating relating to knock resistance of the fuel based on supercharged, high temperature and altitude use.
GC
I think I am right in saying Avgas is a leaded fuel and thus must not be used with catalytic converters. Moreover it is illegal to use in road vehicles since it is under a different fuel tax regime. It also has lower volatility than mogas (motor gasoline) which could conceivably cause fuel mixing and distribution problems. I am sure a bench dyno back to back test on a high powered engine would show this up in an instant.
The rating 100 incidentally is the MON rating not RON; I don't know the direct equivalent from memory but probably way higher than any RON available elsewhere. 130 is a special aviation engine rating relating to knock resistance of the fuel based on supercharged, high temperature and altitude use.
GC
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1969race125
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My local AvGas supplier's advice was that MON is measured under load, and therefore comes in approximately 10 points under RON. (So 100 MON is roughly equivalent to 110 RON). He was unsure whether the 100 in AvGAs100 referred to pure MON or the American standard of (RON + MON) / 2. Either way it is at least 105 RON equivalent.
Motorsport New Zealand have just announced a ban on the use of AvGas from next year. At present it is the most widely used race fuel at most levels (where permitted). I currently use it in my high-compression 8V NA race engine.
Reading through your reply above, Guy, it looks like if I have tuned correctly for AvGas, then I should not require much (if any) timing adjustment moving to unleaded motor fuel of a lower octane rating? Given the high compression (approx 11.8), I assume I should use the highest octane available (here it is 98RON). Would you also recommend I use an octane booster? What would be the indications that I should do so (if I try first without)?
Andrew
Motorsport New Zealand have just announced a ban on the use of AvGas from next year. At present it is the most widely used race fuel at most levels (where permitted). I currently use it in my high-compression 8V NA race engine.
Reading through your reply above, Guy, it looks like if I have tuned correctly for AvGas, then I should not require much (if any) timing adjustment moving to unleaded motor fuel of a lower octane rating? Given the high compression (approx 11.8), I assume I should use the highest octane available (here it is 98RON). Would you also recommend I use an octane booster? What would be the indications that I should do so (if I try first without)?
Andrew
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Guy Croft
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bill
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The tests I have done so far on the dyno 'mule' engine showed that 100 RON over 95 RON results in a useful gain in torque throughout the rev range with a 10-15 NM gain in peak torque.
This is if the ignition advance is tweaked to suit - running the 100 RON fuel on the 95 RON map - the engine made no more power , not even 1NM. As Guy has said , you need to build and map your engine with a specific fuel octane in mind to extract the best from it.
On a side note , running the engine on methanol , it couldn't be made to detonate! Even at low rpm full load conditions. The engine just lost power as ignition was advanced and the peak cylinder pressures climbed too early.[/i]
This is if the ignition advance is tweaked to suit - running the 100 RON fuel on the 95 RON map - the engine made no more power , not even 1NM. As Guy has said , you need to build and map your engine with a specific fuel octane in mind to extract the best from it.
On a side note , running the engine on methanol , it couldn't be made to detonate! Even at low rpm full load conditions. The engine just lost power as ignition was advanced and the peak cylinder pressures climbed too early.[/i]
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Guy Croft
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Bill, hi
I know from your intro that your current university studies are giving you some useful info fuels. Thanks for joining this thread on racing fuels and of course methanol is such a thing.
What alterations are needed to the engine to run methanol? Not a fuel I have ever used or had experience of. Worth citing the type and setup of the dyno unit.
GC
I know from your intro that your current university studies are giving you some useful info fuels. Thanks for joining this thread on racing fuels and of course methanol is such a thing.
What alterations are needed to the engine to run methanol? Not a fuel I have ever used or had experience of. Worth citing the type and setup of the dyno unit.
GC
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bill
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The dyno is an electric eddy brake type , and the engine currently installed is a standard Vauxhall 2.2 Ecotek engine.
Very little is needed to run the engine on methanol - the ignition advance will need to be increased quite a lot as it burns so slowly , and the fuelling increased but there are no other requirements , as far as I know.
Unfortunately I don't have the ability to alter the compression ratio of this engine , however I believe on methanonl ratios of 15/1 plus could be utilised.
Very little is needed to run the engine on methanol - the ignition advance will need to be increased quite a lot as it burns so slowly , and the fuelling increased but there are no other requirements , as far as I know.
Unfortunately I don't have the ability to alter the compression ratio of this engine , however I believe on methanonl ratios of 15/1 plus could be utilised.
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petert
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The avgas we have here in Australia, and BP100 Racing Fuel, is typically 108 RON and probably identical to the NZ product. If you buy it as Avgas it comes in internally coated 200L drums, whereas BP100 comes in uncoated drums. It really does help to make impressive power/toque when the engine is tuned to match. I've achieved 80kW at the wheels from a midly modified 205 GTi, running 32 deg. It was so impressive we tried 33 deg., but it pushed it over the edge. Yes it's bad for O2 sensors and environmentally unfriendly, but is soooo consistent. It's also great in carb. cars.
Conversely, if you're a bit rich at idle it's easy to foul the plugs.
It was supposed to be banned in Australia from 2005 onwards, but it's still legal on the track (or water) providing you have a CAMS Leaded Fuel logbook. The boat racers love it as they have identical conditions to a plane - continuous power. At $2/Litre it's still great value for money but carries a $10000 fine for road use.
The 98 Optimax used as the control fuel for the V8 Supercars is a special. It's made as one batch at the beginnining of the season and somehow has a shelf life similar to avgas.
Optimax, now called V Power ($1.25/L) over here, is also supposed to be 98 octane. However it has a very short shelf life ( 2-3 weeks) before the good stuff evaporates off leaving something like a 95-96 octane fuel. That's why I don't like it personally for the track work I do.
We also now have V Power Racing ($1.30/L), which is 100 RON unleaded pump fuel made by the addition of 5% ethanol. I haven't tried it personally but have used a 10% ethonal 98 octane fuel successfully. It was also the control fuel for our local Lotus Elise series.
The other choice is buy 102RON unleaded racing fuel. At $5 per litre it's pretty expensive. Friends of mine run supercharged Honda powered track Elises. They tune the cars on 98 but run 102 as insurance.
Conversely, if you're a bit rich at idle it's easy to foul the plugs.
It was supposed to be banned in Australia from 2005 onwards, but it's still legal on the track (or water) providing you have a CAMS Leaded Fuel logbook. The boat racers love it as they have identical conditions to a plane - continuous power. At $2/Litre it's still great value for money but carries a $10000 fine for road use.
The 98 Optimax used as the control fuel for the V8 Supercars is a special. It's made as one batch at the beginnining of the season and somehow has a shelf life similar to avgas.
Optimax, now called V Power ($1.25/L) over here, is also supposed to be 98 octane. However it has a very short shelf life ( 2-3 weeks) before the good stuff evaporates off leaving something like a 95-96 octane fuel. That's why I don't like it personally for the track work I do.
We also now have V Power Racing ($1.30/L), which is 100 RON unleaded pump fuel made by the addition of 5% ethanol. I haven't tried it personally but have used a 10% ethonal 98 octane fuel successfully. It was also the control fuel for our local Lotus Elise series.
The other choice is buy 102RON unleaded racing fuel. At $5 per litre it's pretty expensive. Friends of mine run supercharged Honda powered track Elises. They tune the cars on 98 but run 102 as insurance.
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bill
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I thought the 'readership' may be interested to know that I tested some BP Ultimate 102 petrol today - some of you may have seen this petrol being advertised , I watched a live demo at Autosport 2007 with some impressive gains being seen on a turbocharged Porsche.
It's a 102 RON fuel available at the pump , although only in a few sites in the UK. It costs ‚£2.40 a litre! Certainly not a viable option for most road cars.
Anyway , on a N/A vauxhall 2.2 ecotek engine , there was only small gain in torque produced over 99 octane pump fuel (a decent gain over 95). I found the 102 allowed around a 5 to 10 degree advance of the spark when compared to 95.
However , the fuel was very resistant to detonation , it would detonate at low speed/high load , however at higher rpms , torque dropped before detonation occured.
I'm unable to alter the compression ratio of the engine but it would be interesting to see what ratio the 102 fuel could sustain.
It's a 102 RON fuel available at the pump , although only in a few sites in the UK. It costs ‚£2.40 a litre! Certainly not a viable option for most road cars.
Anyway , on a N/A vauxhall 2.2 ecotek engine , there was only small gain in torque produced over 99 octane pump fuel (a decent gain over 95). I found the 102 allowed around a 5 to 10 degree advance of the spark when compared to 95.
However , the fuel was very resistant to detonation , it would detonate at low speed/high load , however at higher rpms , torque dropped before detonation occured.
I'm unable to alter the compression ratio of the engine but it would be interesting to see what ratio the 102 fuel could sustain.
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Evodelta
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bill
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Hi Martin
Was it around a 40 bhp gain? I can't remember exactly. It was a marketing exercise obviously and they way that they were talking made it sound like all you had to do was fill up with 102 and you'd instantly have the extra power.
The car must been remapped with more advance and boost, which they didn't seem to mention!
Was it around a 40 bhp gain? I can't remember exactly. It was a marketing exercise obviously and they way that they were talking made it sound like all you had to do was fill up with 102 and you'd instantly have the extra power.
The car must been remapped with more advance and boost, which they didn't seem to mention!
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Evodelta
Hello Bill,
The gains are shown on the graph, sorry, I should have said, It's a graph with two power (BHP before and after) curves and not a 'traditional' BHP vs lbf ft graph.
As you can see at 4600 there is a 100bhp gain!
The guys operating it had the Porsche hooked up to a lap top so they could have been altering anything in between fuel changes.
It is useful to know that I can now pop down to my local Tescos and get 99 Ron If I need it in the future though (could get the car mapped to run on it)
Martin.
The gains are shown on the graph, sorry, I should have said, It's a graph with two power (BHP before and after) curves and not a 'traditional' BHP vs lbf ft graph.
As you can see at 4600 there is a 100bhp gain!
The guys operating it had the Porsche hooked up to a lap top so they could have been altering anything in between fuel changes.
It is useful to know that I can now pop down to my local Tescos and get 99 Ron If I need it in the future though (could get the car mapped to run on it)
Martin.
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