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Race Gas

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Posted by: DEX

Well I raced in my first MX race last Sunday and had an awesome time. I didnt come in last and that was all that was really important to me. plus I had an awesome time even though a pinched gas cap vent hose caused fuel startvation which led to my bike dieing on the last lap and me loseing 5 positions until I twisted off the gas cap to see if there was gas fixing the problem. Anyways I have a 2001 KX 85 I run Twin Air filter and recently purchased a Bills exhaust system used from an 2002 Kx 85. My Exhaust port will have to be bored out for the pipe to fit as the 2001 had a smaller one. Anyone know how much difference this made? Or will make?

Anways to the point I am looking into race gas as the 85 and supermini class is very competitive and I need to compete with the bikes in my class the oldest bike I lined up to was a 2003 he thought he had the oldest bike and mentioned how he was the only one who didnt have an 04. However they all have fully tricked ported bikes with reed valves and pipes and so on and run race gas.
I was looking for an added boost and was thinking race gas.
I may decide while getting my exhaust port enlarged to get the local race shop to port the engine completley or maybe not either way what do I look for in Race gas I am thinking something with about 95 octane as I konw to high of octane burns to cold and works like crap and maybe a oxgenated fuel. I was thinking Vp Ultimate 2.
Is this a good choice? What else is out there?
My local raceshop is getting in some sort of race gas that starts with an S kinda like Silkolene but different maybe sikonol is that a brand? I imagine he will reccomend whatever he gets. I need some educated unbiased opionons.

Sorry for the long post but you guys complan if you dont get enough background info.


Posted by: Chili

Save your money, keep your tires fresh and spend the left over on some lessons on how to carry your speed through the turns. You'll be spanking the guys on ported 04's with shiny pipes that have no money left for practice fee's in no time. Seriously the bike is a very minor portion of the equation as long is it well maintained and tuned stock. My son just finished racing a bone stock 99 KX80 for the last 2 seasons against all the hotshots with tricked out bikes and the bike was never an issue in his finishes. You will gain far more from a lesson in cornering than you will from hundreds of dollars in porting/pipes/silencers/reeds. Just my experience after watching the 80 and supermini class for the last two seasons here.


Posted by: DEX

If it was ported would it require race gas?
I did notice however what a big difference fresh tires make... I hope the pipe makes that much difference.

Still I do think the bike has something to do with it on one track I race on in paticular it is bottomless sand and its hard to get speed. I wasnt missing any shifts or nothing and shifting right when I should have been but the other guys were just going faster when I had it in 4th pinned.
I dont know my father feels I need something thats why he got me the pipe I am broke right now because of race entry fees. Maybe should I suggest reeds? instead of gas and just stick with Supreme gas?
I am kinda looking for more mid-top power I am not in the bottom Rpm range at all unless I am in the pits.

I was told Oxgenated race fuel would give me a 1 - 2hp increase is this true? What would reeds give?


Posted by: Jaybird

Dex, you aren't listening.....

Learn to corner and you will be far faster han any snake oil fule or pipe can hope to make you.

I know a young man named Poo Sipes who was running super mini and he never let off the gas in just about any corner he took. Amazingly fast on his lil KX.
A rocket around the corners. He couldn't be touched. It wasn't any mod whatsoever that gave him that edge over his competition.
Your dad will go broke trying to get you to that level with his pocketbook, and you still won't be there.

BTW..Poo's older brother is a "Real" Team Green rider, and he got there by using the same techniques.


Posted by: Chili

Dex I'm just passing on my experience after a couple of seasons in the race game. As a father who wants to make sure his son has every competitive advantage I also chased parts and performance mods for the bike but found over two seasons that it made almost no difference. We went to Carbon tech reeds, the kid took it out for a ride and I anxiously awaited his post ride report. He got back to the pits with a "I think it feels a little snappier comment". Bottom line was other than gearing changes we saw little or felt little gains with the popular bolt on mods. I am not going to suggest a bike can't be made much more powerful with extensive mods but my experience so far has shown that less than a select handful of kids are actually riding these bikes anywhere near the potential they already have in stock trim. The best performance mod you could do for almost no money is getting your jetting dialed in.

Again my position would be keep the tires fresh, get your jetting dialed in, take some lessons and practice, pratice, practice.

If your dead set on running race gas go price a barrell of Ultimate 2 and calculate how much gas your going to need this season. That should cure your desire unless money is no object.


Posted by: JTT

Dex, I was there on Sunday.

Listen up to what these guys are telling you...it's all fact! Don't waste your money on race gas, or even lots of fancy
"performance" stuff for your bike that the mags and many others will have you believe you "need" to go fast. It's 90% marketing, don't buy into it. Put your money into fresh tires, top ends and general maintenance. Keep the bike tight and jetted crisp. Investing in some extra gearing for tracks like Kingston is also a wise purchase.

While all those guys are spending theit time and money on fancy triple clamps, pretty Excel wheels, pipes and porting, you spend your time riding and practicing smartly (not just doing jumps and tricks). You'll be the one that comes out on top if you work at it.

There's lots of guys out there running around on fire breathing bikes, that would easily do faster lap time on a stocker. More power is not the answer as many would have you beleive. I can assure you that a good rider on a slow bike will beat a poor rider on a fast bike everytime!

Take the time next race weekend to really watch guys like Davey or Nathan. They had the throttle pinned before they ever layed the bike into the turn in Kingston. It wouldn't have mattered how much power the others had, they'd have spanked them anyways.

Don't get sucked into the "performance" void. Work on you riding and ride as much as you possibly can. It will pay off.

Good luck and see you at the races :thumb:


Posted by: DEX

Wait a minute you wouldnt happen to be Joe Treen would you?
Well the thing is my father went out and bought a Bills pipe that was used from Anthony like the day after the race and then started thinking race gas I dont think it needs race gas as I can run nothing else once I start or get it ported for it plus its super expensive. My father is getting it ported now at Anthony's but maybe I will get him to port it so it doesnt need race gas.....
I cant watch Davey and Nathan because I am trying to catch em. I practice at Hp regualarly though where Davey practices he only ever brings his 250F though so it makes it hard to follow him around the track and imitate what he is doing.

I am definitly looking in MX schools but they dont seem to be going on at all I dont know what to do in that area I need the help now.... however I have come up with a new idea Ryan Lockart while practicing at Hp when the first time I went to Hp suggested I stand more I now stand all the time except the very point of corners. But I dont think I am putting myself far enough forward so I was thinking of duct taping something to the seat so that if I do sit down I have to be on the vary front of the seat almost the tank and anyother time I will be standing.

Did you happen to watch the 85 and supermini races? I was the 96 KX 85 first time racing. I managed to not finish last in all of my races according to the results however I managed to crash right after going by the checkers in the Supermini race. I landed on the side of the finish table top and went over the bars as the front wheel dug in and the bike flipped.

I train as much as possible I go to the Sportsplex every week day to do cardio and wieght lifting and sometimes I swim. I also go to Hp as much as possible but as my father just lost his company truck that has been hard as he wont be getting a truck till this friday.
Cool to talk to someone so local on an international forum!


Posted by: JTT

Yes, I saw that line or your over the finishline tabletop! Very creative

If Anthony puts that motor together, you can be assured it will be done right. He's the best around these parts....makes damn fine coffee too :thumb:

I heard a very good quote from Marty Smith on the weekend that puts the standing/sitting thing in good perspective (Marty was a factory fast guy back in the old days and still teaches in case you didn't recognize the name). He summed it up by saying "..if you but is on the seat, the throttle should be WFO"

When practicing, don't necessarily follow guys like Davey or Ryan, but stand in the corner and watch what they are doing and when they are doing it. Pay close attention to technique...even video it if you can, then try to imitate it. Again, it helps to video it to analyse what your doing right and wrong, or at least have someone you trust (and understands the techniques) to watch you and guide you right.

Sounds like your on the right track though, so keep up the good work. :thumb:


Posted by: DEX

I am getting my bike ported and am trying to decide between getting it ported to run on a 50/50 mix of sunoco 114 and 92 octane pump supreme or Av gas. I have talked to alot of people and the ones that really seem to know what they are talking about actually greatly oppose eachother I read the article on Eric Gorr's site about Fuel for thought and talked to some people who do porting (Moto 814) And they pretty much oppose each other on the Av gas versus 50/50 mix.

Moto 814 told me the distalation curve is better on av gas than a 50/50 mix and that it is more constant than 50/50 mix.

But On Eric Gorr's site it seemed to think Av gas was a poor choice for racing and also after doing some searches Rich Rorich (sp) who seemes to know what he is talking about saying that av gas is made to work at 10000 feet and because of this it doesnt work good at ground level.

Anyone care to shed some more light on this topic?


Posted by: JTT

As I'm sure Rich will back me up on, there's no point running race gas if your motor doesn't need it and your not taking the time to jet sharp. If you want to learn about race gas, read up on Rich's posts...he is "the Man" when it comes to fuel...but read carefully as I still think your wasting your time.


Posted by: bclapham

in my propractise rider days, i would run straight race gas. now i race, i use pump gas mixed with a bit of race gas to just to stop it blowing up since its a tight motor.

try and race as much as possible, thats the way to improve IMO.


Posted by: DEX

I figured it would be a waste to have the bike ported but keep it toned done for pump gas I would think that would really cut down on the improvement...?

I am no longer considering getting it ported for pure race gas but either a 50/50 blend or av gas. Apparently there is a difference so I am just trying to figure out which is best.
The price of gas these days is going crazy Av gas isnt much more than supreme pump these days from what I heard.

I have already made arrangements to get it ported.... I dont want to pull out now, plus it wasnt really my decision it was my parents. I cant hardly afford to pay my race fees. I cant wait to get out of school and start working construction again I am broke. The thing is the pipe they got for the pipe was for an 02 not an 01 so the pipe needs to have the exhaust port ported just so the pipe will fit. Its like a chain reaction but I am hoping the more power will really help.

Tonight for the first time at Hammonds Plains I was really flying through the corners as I started throwing my weight onto the tank and pinning it. Huge difference over standing or sitting in the middle of the seat. I personally can't wait for some more power even if it only makes as much difference as having fresh tires compared to wore out ones I would be happy. I pumped I just got to wait for my new rings to come in before I get it ported...And I got to decide what fuel to get it ported for.


Posted by: DEX

I am getting my bike ported this week or next week to go with my Twin air filter and Bills Pipe. I am trying decide between getting it ported for a 50 50 blend of race fuel and supreme pump gas or getting it ported for pure av gas.

On Eric Gorr's site in a the fuel for thought article it mentions Av gas is a poor choice for motocross bikes. Why?


Posted by: rv6junkie

Think about how avgas is used (if you don't know, I'll tell you). Aircraft are operated with steady throttle positions. For example, the throttle is advanced for takeoff and climb, and left that way (for the most part) for several minutes. Upon reaching level flight, the throttle is moved to a cruise power setting, where it is left until decent.

Not a lot of throttle movement.

Now think about your dirtbike. The throttle is in constant motion.

AvGas (100LL) isn't formulated for the throttle response that a dirtbike requires. It's blended to be stable for long periods of time (a good thing) and consistent (another good thing) in temperature and altitude extremes.

I’d port the bike for a 50/50 blend of race fuel and mogas.


Posted by: DEX

whats mo gas? Thanks for the answer though I am glad someone could finally give me a good explanation.


Posted by: Rich Rohrich

There are at least 100 different threads on race fuel & AvGas that will explain all this in excrutiating detail.

Here's just one of mine that I found.

The simple answer is:
100LL (Blue) Avgas seems to be the most readily available version so I'm assuming that's what we are talking about. 100LL Avgas USUALLY isn’t the best choice but it won't hurt anything.

** For those of you in a hurry, or just sick of me rambling on about this crap skip down to the bottom of the thread to the >>>>>> for a summation.

For those of you still with me, here are some details.
Contrary to popular belief this isn't 100-octane fuel. Aviation fuels are rated on an ASTM Lean/Rich performance number system. 100LL is rated at 91/96 By comparison; Unocal Leaded race gas that is used in lots of spec fuel racing classes has performance number of 112/160. 100LL is closer to 91 octane (MON); by comparison VP C12 is rated at 108 (MON).

For our purposes Avgas has a couple of problems:
1) The 90% boiling point for 100LL Blue Avgas is set at 275 degrees F, which in an engine that turns over 7000 rpm will likely make less power than a fuel that has it's 90% point lower. Pump gas has similar problems, but most good race gas will have 90% Point MUCH lower. As an example Phillips B32 has a 90% boiling point around 235 degrees F and VP C12 has a 90% boiling point around 220 degrees F.
2) Depending on the refiner 100LL can have fairly high aromatic hydrocarbon content, in the 30% by weight range. This level of aromatics will tend to make the throttle response mushy and flat in applications that see big throttle opening transitions on a regular basis. It's similar to what happens when you dump a lot of Toluene based octane booster in your fuel. Throttle response becomes a distant memory.

3) The vapor pressure and distillation curve of Avgas just doesn't seem right for our purposes. The distillation curve or Volatility curve of a fuel determines to a large degree the warm-up, transitional (on & off) throttle response, and acceleration characteristics of an engine.
Here's the simplified version:
A fuels distillation curve designates the maximum temperatures at which various points between 10% and 90% of the fuel will be evaporated as well as the maximum end point temperature. So for any Engine/Air Temperature combination there is a minimum volatility that is required for proper running. As you probably know gasoline is made up of different hydrocarbons, with different boiling points. By combining these
Hydrocarbons together you get a Distillation/Volatility curve. Some hydrocarbons (light ends) boil off at low temps some at much higher temps. Depending on the intended application, a petrochemist will blend hydrocarbons to get a curve that matches the rpm range, temp, altitude, and acceleration characteristics for the application. The problem with avgas as a race fuel is the fact it is blended for an application where
Acceleration and throttle response is not a high priority. If you think about the average light airplane application, you're talking about a fairly low compression engine that runs in a fairly narrow rpm band, and is rarely called on to provide the type of transitional throttle response that a high rpm, acceleration critical application like motocross does. What's more important to the Avgas designer is controlling mixture strength by eliminating the possibility of vapor lock and icing while making sure that light end hydrocarbon fractions don't boil off too early. The lowered rpm ranges used in these engines allow them to push the boiling point up on the upper end as well. As you can see, by using straight Avgas or by mixing various types of fuel together you are modifying a number of important fuel design parameters. You may hit on a combination that works well, but more likely you'll have an engine that doesn't detonate, but doesn't accelerate very well either. So Avgas is SAFE, but not a very good choice. The high paraffinic hydrocarbon content of 100LL makes a very good base stock if you want to play back yard petrochemist, and I believe this is how some of the smaller race fuel blenders start out. I can tell you from experience that it's a ***** to document and test various changes unless you have a lot of time and patience, so trying to come up with your own Super Fuel is probably more trouble than it is worth.

So it sounds like Avgas is really bad for our purposes, and for the most part it is, but given the sorry state of pump fuel today, Avgas is looking better all the time.

>>>>>>
Here's my short course take on things based on my experience and personal biases, (keep in mind this is pretty generalized)

- In almost every case 100ll Avgas is a better choice than alcohol pump fuels

- If you don't need the additional octane that 100LL provides, then MTBE based pump premium (especially Amoco) will tend to provide better throttle than Avgas assuming you have any jetting skill. If you can't jet you're just wasting your time worrying about any of this stuff on a stock bike.

- Mixing 100LL Avgas with a good race gas designed for your application and rpm range is a reasonable way to save some money.

- Mixing alcohol based pump fuels with ANYTHING in an attempt to make it BETTER is just a chemical circle jerk, and if you're that cheap or that ignorant you deserve the crummy performance and the insurmountable jetting problems that you will invariably be blessed with.

- Milspec Avgas is a different animal entirely, but isn't readily available so we won't worry about it.

- The correct race fuel for your application will outperform ANY of the above, regardless of whether the engine is stock or modified. The more demon tweaks hiding in your engine, the more you have to gain.







Try out the SEARCH function and take a look around, you'll be surprised what you might find.


Posted by: rv6junkie

mogas is what aviators call car fuel...mo(tor) gas


Posted by: WWR

DEX,
the porting itself, if done in a quality way, will not make the bike require a higher octane. Usually, it will make an engine more octane-tolerant. It is the head modifications that really effect what fuel you require. I would advise you have the head and Compresson Ratio set up to run pump gas, as this will keep your bike more reliable. The last thing you want is a touchy bike that blows up every time your jetting is a tad off. Having the head setup for race fuel and running race fuel should be the last thing you do, after your skill has peaked (aka pro-level). Skill, a reliable bike, and confidence in the bike's handling go alot further than race gas or higher compression ever will.


Posted by: Jaybird

Yeah,yeah,yeah.... but what magic wand should we buy?


Posted by: DEX

I know the magic wand is kinda an insult but I guess I am kinda looking for one you pumped up your bikes engine didnt ya? YZ444F? ALot of the tracks I race on are geared towards larger bikes with large jumps and the practice track is even worse most novices regardless of what bike have to roll the jumps as it is almost like supercross practice track in my area. I need a boost in power to get over these jumps they are slowing me down alot by flat landing the tables and halfway doing the doubles. I keep it pinned and can now fly through the corners but I still come up way short or have to roll most of the jumps because they are just too dangerous I have the confidence and I am getting better with my skills as I practice everyday now. I feel I am ready to kick it up a notch I guess... my suspension is setup fgor my wieght already which made a huge difference... My parents feel I am ready for more and want to help by buying me stuff for my bike.... personally I only wanted to buy a reedvalve.
I guess I just want a little boost to help get me clearing the jumps I can clear some dont get me wrong but the other bikes in my class are really heavily modified and just got more power to clear jumps I come up short on even though I am am in the best gear pinned. I want to be competitive.

BTW I am thinking now I should just stick with supreme pump or maybe a 50 50 blend but you guys seem to think supreme pump is the best and race gas isnt worth it.


Posted by: Jaybird

I really didn't mean to insult you, Dex. Merely making a point.

I think if you read closely above...and in many other threads as well, you will find that proper jetting is the key to many ills. A properly jetted bike can make it as if it were a completely different animal.
Granted there are gains to be had from using trick fuels and modifications, but in my "old-n-notsowisesometimes" opinion unless you have your bike tuned properly, modifications and trick fuels are at best a money pit.

You Pop will have a much bigger smile on his face if he attemps and is successful at tuning the circuits of your carbuerator, with a small handful of inexpensive brass, and finds that he has turned your slug into a fire breathing demon. At that point there are even more gains to be made by utilizing the proper fuel and modifications.

When I was a young kid...now this would be many moons ago, I had a rat bike that I thought wasn't perfoming too well. An older friend of mine who was quite a bit more skilled than I was, showed me that I wasn't even utilizing all of the throttle. I thought I had it pinned most of the time, but my technique was lacking. Just his simple lesson on how to turn the throttle made me faster.

You will get faster and make those jumps even if you do nothing more to your bike if you practice. You obviously have a "want to" attitude, so go out and get er done.


Posted by: Chili

Quote:
Originally Posted by DEX
I need a boost in power to get over these jumps they are slowing me down alot by flat landing the tables and halfway doing the doubles. I keep it pinned and can now fly through the corners but I still come up way short or have to roll most of the jumps because they are just too dangerous


My guess is that none of this will change no matter how you get your engine ported and what gas you have in the tank. I'd also be willing to bet that the guys that are clearing those on their "heavily modified" bikes could do it on yours bone stock unless it's a total roach.

Unless the racing in the Maritimes is completely different from here in central Canada most of the guys in the Supermini/85cc classes are running very little in the way of mods except for the odd top guy who is racing outside the province as well as locally. How big are these tables and doubles you can't clear? I've seen one of our top racers here clearing huge tables and doubles on a bone stock KX85.


Posted by: Rcannon

One thing I woudl ad is find your owners manual...and use it!

I have seen a lot of the bikes with ever botl on available. Yet, when you notice the suspension linkage there is a seasons worth of dirt packed around it. I dont care how fast your bike is, the suspension should be in top condition.

I have bught a garage full of aftermarket parts for my YZ 250 (**** addict). The only ones to really make a difference were my flywheel weight and good tires.


Posted by: marcusgunby

To back up what jay says heres a dyno from just a change in jetting-it has more power all the way up through the range-thats hard to do with any bolt on.


Posted by: marcusgunby

To add more proof, heres dynos of 3 different carbs-we went from one extreme to another 36mm to 39mm.This was on the 04 RM125

as you can see apart from at the very ends of power ranges(where very few people ever ride) they are almost inseperable.

Ive got tests of 'power now' and ICATS and neither show any gains on the dyno-thats not to say they dont do anything-just the dyno cant pick up the changes.

Save you money-good tires, jetting, top ends and most important, pay for tuition-you can gain seconds on your lap times where bikes mods often actually loose power-alot of British championship bikes make only 2 hp more than a std 125-they talk of 40hp but when the dyno shows 34 they soon shut up.



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