Petrol comparison

[GreyRex]

Saw this article showing a comparison in fuel types, including 95RON, 98RON and 99RON. Haven't really seen an in depth analysis, so thought some of you might be interested as well

http://www.thorneymotorsport.co.uk/tuning/Fuel_Test_Results.shtml

[Wraith]

Didn't have a chance to read the whole thing, but don't know what good or benifit the data on the 99 RON fuel would have for us here in Oz.

[EL BURITO]

It is clear from the testing that whilst older engines show a clear benefit of running higher octane fuel, more modern, sophisticated engines have the ability to advance their fuel timing to take full advantage of this enhancement to a far greater degree. For the BMW M3 CSL the difference between running 95 octane fuel and Tesco 99 Octane fuel was over 40bhp, that’s over 10%.


intresting

[bornwild]

After 7 months of intensive testing Thorney Motorsport (TMS) can now categorically confirm what the entire car tuning World already knew - the quality of fuel you use in your car has a direct effect on the level of power your car provides.

This is true only if you drive a force-fed car or a performance-spirited naturally aspirited engine; when it comes to petrols that is.

But hell....it doesn't take a mastermind to figure out that the more binding energy a fuel has(RON), the more energy will be released, hence you will get more power. The thing is, if the engine isn't specifically tuned for a fuel, you won't really get all that much more power out of it.

[GreyRex]

This is true only if you drive a force-fed car or a performance-spirited naturally aspirited engine; when it comes to petrols that is.

But hell....it doesn't take a mastermind to figure out that the more binding energy a fuel has(RON), the more energy will be released, hence you will get more power. The thing is, if the engine isn't specifically tuned for a fuel, you won't really get all that much more power out of it.

We all know that. It's just good to see measureable differences

[digifish]

This is true only if you drive a force-fed car or a performance-spirited naturally aspirited engine; when it comes to petrols that is.

But hell....it doesn't take a mastermind to figure out that the more binding energy a fuel has(RON), the more energy will be released, hence you will get more power. The thing is, if the engine isn't specifically tuned for a fuel, you won't really get all that much more power out of it.

Hang on... RON is a measure of resistance to compression induced combusion and is independent of the energy content of the fuel. RON matters as you can advance the timing more and ignite the fuel earler (creating a pressure front that can cause unwanted secondary 'detonations' - knocking) if your RON is too low.

The reason you get more power is that more combustion has occurred closer to TDC. It's a waste of energy if fuel is still combusting as the piston is 1/2 on the down-stroke. Again, RON has nothing to do with energy content.

digifish

[bornwild]

Hang on... RON is a measure of resistance to compression induced combusion and is independent of the energy content of the fuel. RON matters as you can advance the timing more and ignite the fuel earler (creating a pressure front that can cause unwanted secondary 'detonations' - knocking) if your RON is too low.

The reason you get more power is that more combustion has occurred closer to TDC. It's a waste of energy if fuel is still combusting as the piston is 1/2 on the down-stroke. Again, RON has nothing to do with energy content.

digifish

Resistance to compression induced combustion = Binding energy of fuel :cool:

[digifish]

Resistance to compression induced combustion = Binding energy of fuel :cool:

You said...

"the more energy will be released, hence you will get more power"

More energy is not released. It is just released in a more controlled way.

For example...

diesel - RON: 25 @ 38.6 MJoules/litre
petrol - RON: 95 @ 34.8 MJoules/litre
ethanol - RON: 129 @ 23.5 MJoules/litre

Diesel has more energy with less RON, ethanol has less energy with more RON compared to petrol. So RON allows you to advance the timing and/or run higher compression ratios.

digifish.

[gman]

The actual “Octane” of a fuel measures the amount of benzene or iso-octane in fuel.

The RON (Research Octane Number) or MON (Motor Octane Number), both of which are "Octane Ratings" are measures of a fuels resistance auto-ignition / pre-ignition, detonation, "Pinging" or what ever other name people use.

The higher the octane of a fuel, the greater the resistance to pre-ignition.

But, it "MAY" have a lower calorific content (energy available through combustion) content than a lower octane fuel.

High Octane/Low calorific content fuels make power by the ability to advance timing to optimal levels and/or run increased compression and/or higher boost.

Ethanol has lower calorific content than petrol or diesel, but higher octane rating.

LPG is higher again but again has less calorific content….

[bornwild]

I was referring to petrol only :P :D

[digifish]

I was referring to petrol only :P :D

We are going to hunt you down on this one! :p

Petrol has the same MJoule/litre content regardless of RON

digifish

[bornwild]

We are going to hunt you down on this one! :p

Petrol has the same MJoule/litre content regardless of RON

digifish

For the general populace, it is a roughly accurate thing to say that, the higher the RON, the higher the energy content. Technically this may not be correct, but in the end the results are the same, hence I didn't really bother to look it up into detail :p:p:p

[digifish]

For the general populace, it is a roughly accurate thing to say that, the higher the RON, the higher the energy content. Technically this may not be correct, but in the end the results are the same, hence I didn't really bother to look it up into detail :p:p:p

Hmmm.... my 'reality distortion field' is stronger than yours...in my version of reality you have just claimed that aliens stranded on Earth when their ship crashed here in 1951 are stealing RONS from petrol in order to power a faster-than-light-drive for a ship they have constructed from old beer cans. This is the main reason petrol dropped from 98 RON to 91 with the introduction of unleaded as they needed to hide what they were doing and so brain washed the population to think lead was bad...when infact it's a brain food. ;)

[dunko]

i got a braina 94 gsi if u run it on any less the 96 it is a dog have to run it on 96 98 or 100 100 is the best and its cheaper as it is 10% ethanol.

[stevedee3]

Here's what I thought the story was:
Thermal efficiency of an ideal Otto cycle engine is a function only of compression ratio - higher compression ratio = higher efficiency
Higher octane fuel allows for higher compression without unwanted pre-ignitionPut these two together and higher octane fuel allows for greater efficiency => more power out from the same amount of petrol in

[rjastra]

So they choose a control vehicle from a market where 100RON fuel is common place and the MR2 is most likely designed for it.
And the other car is a highly modified M3 that is designed to produce max power on 98+ROn fuel.

Then they fill both of them up with regular (in the EU) unleaded of 95RON and wonder why they get a power drop.

What they prove is nothing more than engines designed to run optimally on 98RON will see a power drop when you run them on a lower octane fuel.

It does not mean that a car designed to run on 95RON efficiently will see a power hike when run on 98,99,100RON fuel.

[gman]

Any increase in power from the change in the octane of a fuel will depend on the ability of either:
a) the ECU,
b) the tuner,
c) the engine builder or
d) a combination of the affore mentioned three points.

If the standard ECU doesn't run closed loop O2 fuelling control and/or knock sensor ignition control then it will not be able to take advantage of the increased octane.

You would then have to either:
a) mechnically increase the compression/boost (effective compression increase) of the engine or
b) re-calibrate the ECU to take advantage of the different characteristics of the fuel.....

The Motronic 1.5.1 in the SRi-T does both so can "learn" the new fuel advantages by altering the fine tune fuel and ignition maps that overlay with the base map from the factory or from a re-mapped tuner.

[GreyRex]

Any increase in power from the change in the octane of a fuel will depend on the ability of either:
a) the ECU,
b) the tuner,
c) the engine builder or
d) a combination of the affore mentioned three points.

If the standard ECU doesn't run closed loop O2 fuelling control and/or knock sensor ignition control then it will not be able to take advantage of the increased octane.

You would then have to either:
a) mechnically increase the compression/boost (effective compression increase) of the engine or
b) re-calibrate the ECU to take advantage of the different characteristics of the fuel.....

The Motronic 1.5.1 in the SRi-T does both so can "learn" the new fuel advantages by altering the fine tune fuel and ignition maps that overlay with the base map from the factory or from a re-mapped tuner.

Awesome, so with the SRi-T (TS and AH) it'll learn your fuel type and you'll have some benefits? Because that was basically the point of my post lol

[rjastra]

Awesome, so with the SRi-T (TS and AH) it'll learn your fuel type and you'll have some benefits? Because that was basically the point of my post lol

It depends if it has any maps for fuel greater than 98RON I suppose.

So, you will get a difference 95 vs 98RON but not feel get any significant difference for 98 vs 100RON.

This all goes out the window for modified ecu cars with maps for 100RON fuel.

[gman]

Awesome, so with the SRi-T (TS and AH) it'll learn your fuel type and you'll have some benefits? Because that was basically the point of my post lol

Yep, you will if you let the ECU learn the fuel by pushing the fine tune timing and fuelling maps..


It depends if it has any maps for fuel greater than 98RON I suppose.


No, the ECU will keep moving the timing and fuelling thereshold until it has reached the max values of the fine tuning tables regardles of the fuel used.

These tables have enough "headroom" to easily accomodate the extra timing and fuelling needed to take advantage of a 100 ron / 5% Ethanol fuel over standard 98ron.

Example: a Standard ECU Map can learn the fuelling difference between the standard and VXR injectors and compensate...Fit the larger VXR injectors and the car initially runs very rich...After about 100km's the ECU reduces the fuelling through ther closed loop O2 sensor and the car runs perfectly..

These tables allow the car to use lower ron fuels like 95ron in a pinch or run more efficiently on 100ron if available...

The only time it will be "lazy" is if you drive it like a grandma so it never gets to reach the current fine map timing and fuelling tables..

So put it in, drive it hard and you should see it pick up some performance after 2 or 3 tanks...

My car has the re-flashed ECU & certainly notices the difference..I only use the 100 RON stuff now, sometimes for hard driving I've used a nitromethane additive and it responds nicely to that too.... ;)