any thoughts or insights on race fuel?

[adrian in florida]

Today I ended up putting about 5 gallons of 100octane in my H5s, I would have tried the 110 octane but i did not have a container and its illegal to pump 110 plus directly into a vehicle. Anyway, the tank was empty so most of what I was running was the pure 100octane. I would like to try the 110 or 113 stuff they sell at the track ,someday.
long story short the car seemed pretty darn peppy.... I blew by a new vette which was running very agresively... Just two guys out having fun.... when I slowed down they came by and gave me some big grins and seemed pretty suprised.... No doubt that car was way faster than mine I think they were just suprised...
Question, what is the down side ( other than the 6 bucks per gallon) of running this fuel... I think it added to my fun factor if not my ego.... what do you guys think?

[DRP535]

I scored 4 x 20 litre drums of Elf Racing Fuel left behind by the WRC teams after Rally Australia here. It's far too costly to fly back to Europe, so on the flyaway rounds they just leave it behind for disposal or is given away to someone like me.

I have no idea what octane it is but probably only 100 RON I guess. Burnt it smells like honey on toast in the morning. Made no difference performance wise that I could tell in my 8:1 motor with powerchip. It did make a nice smell though.

Major bigtime downside is the shelf-life. 4 weeks is not long and 2.1/2 weeks of that were gone by the time I got it. The drums come very loudly labelled with a "do not use after dd/mm/yy sticker on them and that was pointed out to me by the guy that said I could take them. I dunno what happens to the fuel after that date but I got the impression it wouldn't be good.

[Jeremy]

Be careful if you have a catalytic converter. The stuff you have to pump into a container is very likely leaded fuel. The 100 octane, in theory, shouldn't make any difference in performance without putting a different tune on the motor (advancing the timing curves), so it's possible that your motor is actually pinging slightly without you hearing it if you noticed a difference in performance.

I dunno what happens to the fuel after that date but I got the impression it wouldn't be good.

It turns into a varnish-like substance which isn't very combustible and tends to gum up everything in the fuel system (like injector nozzles). I'm not sure how well the "fuel preservative" products sold would work on that juice, but you might want to look into it. Or just use it all while you still can!!

Jeremy

[Matt]

as i understand things, 100, 110, or 113 octane shouldn't provide any benefit whatsoever unless:

a) you are running forced induction
b) you've got some engine management change such that you're asking for way more spark advance than stock
c) you're running high CR (like 11:1 or more)
d) you had the car tuned such that you were getting knock on premium gas.

[Kenny Blankenship]

The 110 octane stuff I've seen has lead so if you have a cat don't use it.

I put about 20-25% 100 octane gas in the M7. It does seem to run better under hard acceleration. My car doesn't like 91 quite as much. At the track I'll go up to 40 or 50% (Infineon sells 96 octane) and the car loves it. It does seem peppier and smoother. My mechanic suggests using pure 100 octane but I haven't done that yet.

I don't know if you have this luxury, but I've found widely varing prices for 100 octane. The gas station I frequent most is now charging $5 per gallon, another local one charges $5.50. When I go to Infineon, I stop by a station in San Jose who is very cheap and has been as low as $4.25. But the gas station in West LA charges almost $8 and in Pasadena about $6.75...

[tsmall07]

there is no reason to run higher octane fuel if you have a stock engine. the higher the octane rating, the more the fuel resists combustion (so there is no reason that it would increase your performance). it resists combustion because higher compression engines generate higher fuel/air temperatures which can ignite lower octane fuel before the spark plug goes off.

[adrian in florida]

I am running this in a hartge tuner car with 10:1 compression euro prepped no cat... I actually did think the car seemed to be peppier... I found the biggest improvement to be at high speeds 110mph plus... it just seemed to run smooth...of course this is all seat of the pants. I do think i would like to experiment a little more because the race fuel is available. I just dont want to blow anything up.... I suppose the higher octane must relate to ease of combustion....
I guess I am just looking for some reassurance going forward given that the cat is not an issue... happy new year!

[DRP535]

there is no reason to run higher octane fuel if you have a stock engine. the higher the octane rating, the more the fuel resists combustion (so there is no reason that it would increase your performance).

Unless of course that octane increase has been achieved through a completely different and very fruity blend of different chemicals which also yield a higher calorific value. This is the case with custom racing blends of Elf fuel for example. The higher calorific value means more energy is released per volume of liquid. ie. a bigger bang. This occurs regardless of how much it gets compressed first.

That said though, the ideal and most efficient composition for gasoline was arrived at many years ago such that increased calorific value compositions can only be achieved these days with synthetic blends that have considerable down sides like reduced shelf life, higher freezing points, lower flash points, increased volatility and suseptibility to fungal growth, hence they are only of any practical use to race teams.

Sometimes a gain can also be achieved by reducing the number of air molecules required for oxidizing the fuel in combustion. If you can get this down from the usual 14:1 ratio to something less then you can significantly increase power at the obvious expense of fuel economy because it's much easier to get lots of fuel into the cylinders than it is lots of air. Nitro methane's ideal air/fuel ratio for example is about 2:1 which is why nitro drag cars go so bloody fast. When you can shove nearly 3 litres of liquid fuel into each induction stroke of a 9 litre displacement engine, you get a pretty big bang. The fuel injectors on those things must be like garden hoses. 'Course a single misfire usually means a hydraulic lock and an engine that closely resembles a hand grenade with the pin pulled.

[DRP535]

I am running this in a hartge tuner car with 10:1 compression euro prepped no cat... I actually did think the car seemed to be peppier... I found the biggest improvement to be at high speeds 110mph plus... it just seemed to run smooth...of course this is all seat of the pants. I do think i would like to experiment a little more because the race fuel is available. I just dont want to blow anything up.... I suppose the higher octane must relate to ease of combustion....

No it doesn't. As stated by someone else, octane is a measure of how difficult it is to ignite the fuel. The higher the number, the harder it is to burn the fuel. Water has an incredibly high octane for example. Well into the thousands. Ever tried to set fire to water? It's not easy let me tell you. In fact, the cheapest, easiest and most effective way to increase your fuel's octane is to add exactly that... water. Pour some water in with your fuel and the octane rating will skyrocket. I don't recommend it though because your car will rust from the inside out pretty damn quick.

Cetane is the measure of ease of combustion. Cetane numbers are how diesel fuels are rated. The higher the number the more likely it will ignite when you drop a burning match into it. The higher the Octane number the lower the chance it will ignite with a burning match. Octane and Cetane are measures of opposite properties.

100, 110, 113 octane fuels are actually very low in the broad scheme of things. There are plenty of fuels with much higher octane values. Kerosene (jet fuel) for example is around 140 from memory. Methanol (Champcar fuel), Methylated spirits, white spirits etc. are all around 160. Mix some water in with them and they go up over 200 pretty easily. The reason gasoline is so dangerous is precisely because its octane rating is so low. All it needs is a pissy little electrical spark from a couple of metal electrodes mere millimetres apart to set it off.

If you've ever dropped a lit match into a pool of diesel or methylated spirits, 9 times out of 10 the match will just be put out by the liquid. That's what a really high octane fuel will do.

There's much more to producing a good fuel for a car engine. Octane is not the b-all and end-all. You need a balance of a number of properties or alternatively you pick a fuel which is very favourable in one property and design the engine to get the most result from that one property over its cons.

A good example is a Nitro-Methane burning dragster. Seeing as how these vehicles are the fastest accelerating things on the planet (even quicker than aircraft launched from CVs with the aid of steam catapults and the space shuttle at take off), most people think they are high performance, and rightly so. So then, their fuel must be ultra high performance with ridiculously high octane right? Wrong. Nitro Methane has incredibly low octane. It's about 36 I think. You can get the stuff to explode almost by breathing on it. Tap a puddle of it with a hammer and the hammer will end up 60 feet behind you as it went flying out of your hand and over your head. It doesn't need any heat, flame, spark or obvious ignition source at all to burn. The engines that run it have very low compression ratios and very late timing to accomodate the low octane rating. If you set your timing in your road car to where a nitro drag car's would be set, your engine probably wouldn't run at all. Nitro methane doesn't even have a particularly great calorific value either. Certainly it's nowhere near as potent as gasoline. It's huge stong point however is that the molecule contains a boatload of oxygen atoms. That means the fuel itself is it's own chemical turbocharger. The fuel is on its own the biggest nitros oxide injection system. In comparison to a gasoline engine, it needs hardly any air mixed with it in the cylinders to burn completely. So even though it has incredibly low octane and is by volume pretty weak in comparison to gasoline, when you burn almost a whole litre of the stuff in a tiny fraction of a second you get one hell of a energy release. Even though it has 1/3 of the octane and maybe 1/2 of the calorific value of gasoline, when you can burn 1,000x more of it on every power stroke, that kinda outweighs the disadvantages.

[DRP535]

I dunno what happens to the fuel after that date but I got the impression it wouldn't be good.

It turns into a varnish-like substance which isn't very combustible and tends to gum up everything in the fuel system (like injector nozzles). I'm not sure how well the "fuel preservative" products sold would work on that juice, but you might want to look into it. Or just use it all while you still can!!

Jeremy

~70-odd litres of it went into the car and the rest went in the MEY roller lawnmower :-) Didn't faze the lawnmower one bit and added a nice sweet perfume aromatic to the garden which was probably highly toxic and carcinogenic to boot :-D

The car copped a thrashing up in the hills directly afterwards to make sure it was all well and truly gone before the expiry date. I was thinking it might turn into glue if I left it sitting too long.

[m-racer]

I am running this in a hartge tuner car with 10:1 compression euro prepped no cat... I actually did think the car seemed to be peppier... I found the biggest improvement to be at high speeds 110mph plus... it just seemed to run smooth...of course this is all seat of the pants. I do think i would like to experiment a little more because the race fuel is available. I just dont want to blow anything up.... I suppose the higher octane must relate to ease of combustion....
I guess I am just looking for some reassurance going forward given that the cat is not an issue... happy new year!

Adrian, I would suspect that your car does run better with the higher octane stuff. I use octane boost in every tank in the B9 as it (like yours was not built for 93 octane) has very high compression. At what point it is no longer beneficial (I am guessing 96 octane) I am not sure. I'm no expert, but my car doesn't run as well on 92-93 octane. On another subject, I used to use 100 octane in my 02 M Coupe when I tracked it and it became even more of a beast. Obviously, it has modern engine mgmt systems.I keep waiting for the AFM to go on the B9 so that I can get a programable Alpha N system. Maybe that will make it easier to dial in. Happy New Year, Tim

[DRP535]

When you guys are saying 100 octane you mean pump number right? "Pump" as opposed to MON or RON?

100 "pump" in the US is equivalent to 104 RON. That's higher than piston engine aviation fuel in Australia. BP100 is avgas down here and also race fuel at the local track. There isn't an unmodified Hartge or Alpina version anywhere that needs fuel that high in octane to run without detonation. All quoted octane numbers in Australia are RON where not specified otherwise. So BP100 is equivalent to US 96 "pump" or 92 MON.

In Australia you can't buy anything higher than BP100 at retail service stations. To get higher you have to buy direct from wholesale distributors in drums or through specialist locations like drag strips/airports etc. where there might be some equipment that needs it and you possibly need a hazchem safety certificate as well to certify that you know how to store and handle it safely.

Even BP100 is only available at one local service station outside of the local race track and light aircraft airport I know of.

[adrian in florida]

drp535 Im not exactly sure about the formula for determining octane. I know it does vary from country to country,There is some info about it in the owners manual.Basically here in the U.S, 93 octane seems to be about the highest you can purchase. There are a few stations that sell race fuel (speedway) and you can always buy it at the track.... I know there is a point of diminishing return , in terms of octane,,,, but heck all the local yokals at the track run it.
I thought I felt a difference yesterday... I am going to go get a few gallons of the 110 octane and report back..
Tim, I am right there with you on the management system.. I just dont know enough to make an informed purchase much less an installation.... I know the guys at C and C would love to do it... The only thing that drives me batty about the management systems is that the guys are always driving around with a lap top and making continuous adjustments.I dont have the patients for that.... I would like to have a system where I could map out maybe three different driving styles..
Oh by the way my new year resolution is to learn to drive. I might even join the bmwcca.... Now that I have lowered those seats I can put a helmet on..... There is an event at sebring jan 17th. If I can find the time I might try to go to the drivers school. I would very much like to see the H5 and the B9 running at sebring some day...

[m-racer]

Adrian, I had quite a bit of trouble with the AFM on the Alpina, but finally got it adjusted correctly. Ben Thongsai suggested the Alpha N system (which was used on my S14 powered 2002). Thomas and Steve do have experience with the system since they use it in the E30 M3's they run. My experience with the system is that you get it set up the way you want and leave it be.

[m-racer]

When you guys are saying 100 octane you mean pump number right? "Pump" as opposed to MON or RON?

100 "pump" in the US is equivalent to 104 RON. That's higher than piston engine aviation fuel in Australia. BP100 is avgas down here and also race fuel at the local track. There isn't an unmodified Hartge or Alpina version anywhere that needs fuel that high in octane to run without detonation. All quoted octane numbers in Australia are RON where not specified otherwise. So BP100 is equivalent to US 96 "pump" or 92 MON.

In Australia you can't buy anything higher than BP100 at retail service stations. To get higher you have to buy direct from wholesale distributors in drums or through specialist locations like drag strips/airports etc. where there might be some equipment that needs it and you possibly need a hazchem safety certificate as well to certify that you know how to store and handle it safely.

Even BP100 is only available at one local service station outside of the local race track and light aircraft airport I know of.

I don't think the B9 or H5S need 100 octane. They do however need something higher than 93.

[BMWJustin]

Adrian,
I have run lots of different octanes from a few different manufacturer's. My H5s loves 115 octane and it was built for race gas (11.5 to 1 compression) and tuned with a stand alone ecu. The car will run on 93 but it just comes alive with 100+.
TIA
Jusitn

[M635CSi]

The octane needs of an engine vary with speed, load, temperature, air density, etc. The octane requirements at idle or while cruising on a cold engine aren't as high as the octane requirements are for full acceleration or high speed runs with a hot engine. Beyond that, I don't believe it's possible, without an engine dynamometer (and empirical testing) to know exactly what octane requirements an engine has at different speeds, loads, temperatures, etc. Too high an octane does reduce Brake Mean Effective Pressure (BMEP) and thus reduces power but it has almost no effect on longevity. Too low an octane (resulting in detonation) also reduces power and may result in a catastrophic call on an engine's resources such that broken piston rings, broken ring lands, snapped connecting rods (among other things) result.

Given the same set of variables (engine speed, load, temperature, air density, etc.), an M30 engine will require higher octane than an M88/S38 engine.

[Tim in N FL]

drp535 Im not exactly sure about the formula for determining octane. I know it does vary from country to country...<snip>

Adrian et al.,
I found this info via a quick Google search:

The R means "Research Octane Number"
The M means "Motor Octane Number"

"(R+M)/2
Research Octane Number plus Motor Octane Number, divided by 2. Used
now as general measure of road octanes of gasoline."
http://www.havoline.com/carcare/glossary/r.html

"Research Method- Research Octane Number (RON)
A test for determining the knock rating, in terms of ASTM Research
octane numbers, of fuels for use in spark-ignition engines. The
knocking tendency of the fuel is compared with those for blends of
reference fuels of known octane number when run in the ASTM-CRF engine
at 600 rpm under standard operating conditions (ASTM Methods D908 and
D 1656)."
http://www.chevrontexacoursa.com/glossary/r.html

"Motor Method- Motor Octane Number (MON)
A test for determining the knock rating, in terms of ASTM Motor Octane
Numbers, of fuels for use in spark-ignition engines. The knocking
tendency of the fuel is compared with those for blends of reference
fuels of known octane number when run in the ASTM-CFR engine at 900
rpm, under standard operating conditions as prescribed in ASTM Method
D 357."
http://www.chevrontexacoursa.com/glossary/m.html

Interesting discussion you guys...thanks!

Tim

[m-racer]

Adrian,
I have run lots of different octanes from a few different manufacturer's. My H5s loves 115 octane and it was built for race gas (11.5 to 1 compression) and tuned with a stand alone ecu. The car will run on 93 but it just comes alive with 100+.
TIA
Jusitn

The B9 is running 11.5 to 1 as well. Mine will run ok on 93, runs better on 96 (back when I could get it at the local Sunoco) and runs about the same or a little better on 100. I have never tried anything higher.

[DRP535]

I don't think the B9 or H5S need 100 octane. They do however need something higher than 93.

Yeah that's within the realm of possibility. 93 PUMP is 97 RON and my M635CSi with M88/3 needs 97 RON according to the owner's manual so that quality fuel must have been readily available in Europe at the time of sale. It's entirely possible that an even more exclusive and highly tuned version might require 98 or even 99 RON. Or as the engines get older they become less tolerant of octane due to carbon deposits and even though designed for 97 RON may indeed still ping slightly on it nowdays.

I can't buy exactly 97 RON here in Australia like you can in the US. We have the choice of either 96 RON or 98 RON. My M635CSi will just start to ping on 96 RON if you drive it like a real moron and labour it in 5th gear going up a hill. But you really have to provoke it by driving it like a grandpa. It's very easy to drive it so it won't ping at all which is what I do.

On 98 RON I've never heard it ping or felt any negative reaction from the engine at all. Unfortunately the price and availability difference in Australia between 96 & 98 RON is significant, hence why she mostly gets a diet of the lower octane stuff most of the time. I was in the country with it once and had to buy standard 91 RON (87 PUMP) because that was all that was available. That wasn't a pleasant drive to the next closest station I can tell you. Lots and lots of revs were called for and absolutely no 5th gear at all. No hard acceleration. It felt like I was about to punch a hole through a piston at any moment. Fortunately I only had to drive about 100km like that before I could get some octane booster and top it up with PULP instead.

[DRP535]

drp535 Im not exactly sure about the formula for determining octane. I know it does vary from country to country...<snip>

Adrian et al.,
I found this info via a quick Google search:

The R means "Research Octane Number"
The M means "Motor Octane Number"

"(R+M)/2
Research Octane Number plus Motor Octane Number, divided by 2. Used
now as general measure of road octanes of gasoline."
http://www.havoline.com/carcare/glossary/r.html

"Research Method- Research Octane Number (RON)
A test for determining the knock rating, in terms of ASTM Research
octane numbers, of fuels for use in spark-ignition engines. The
knocking tendency of the fuel is compared with those for blends of
reference fuels of known octane number when run in the ASTM-CRF engine
at 600 rpm under standard operating conditions (ASTM Methods D908 and
D 1656)."
http://www.chevrontexacoursa.com/glossary/r.html

"Motor Method- Motor Octane Number (MON)
A test for determining the knock rating, in terms of ASTM Motor Octane
Numbers, of fuels for use in spark-ignition engines. The knocking
tendency of the fuel is compared with those for blends of reference
fuels of known octane number when run in the ASTM-CFR engine at 900
rpm, under standard operating conditions as prescribed in ASTM Method
D 357."
http://www.chevrontexacoursa.com/glossary/m.html

Interesting discussion you guys...thanks!

Tim

And just to add to what Tim found, you should know that there is no formula as such for converting MON to RON. MON numbers are simply 8 digits lower than RON ones. Therefore PUMP numbers are 4 digits below RON and 4 digits above MON according to the above averaging formula.