Motorcycle Racing Forum

Motorcycle Racing => Wrenching => Topic started by: Tim Mainard on September 02, 2002, 07:06:15 AM

Title: Bike Problem or Bad Fuel?
Post by: Tim Mainard on September 02, 2002, 07:06:15 AM
I ran my 954 last weekend at the track. I put racing fuel in it from the track and it ran really bad.  It shugged and sputtered on and off.  I took it to the dealership and it tested out fine, no problems.  They said it might have been the fuel. It has about 1800 miles on it and is all stock. Has anyone had similiar problems with fuel injected bike?
Title: Re: Bike Problem or Bad Fuel?
Post by: sportbikepete on September 02, 2002, 09:39:53 AM
When you switch to race fuel without and carb/fi changes of course you may have problems. You know race fuel is also leaded right? Think about modern cars, if you run Super in them they run like crap because the computer FI is set up for a max octane of say 87 and you put in 93. Now on your bike it may be set to handle 94 octane and you put 111 in it you will have problems.
Title: Re: Bike Problem or Bad Fuel?
Post by: TBMain on September 02, 2002, 11:14:13 AM
Thanks for your input. I didn't specify in my first post, but I did run 100 octane unleaded race fuel. I know better than to run leaded in a bike that requires unleaded only. Sorry for the lack of info.
Title: Re: Bike Problem or Bad Fuel?
Post by: tcchin on September 09, 2002, 11:38:51 AM
Octane ratings are not something for which a fuel delivery system is tuned, as they don't affect the air/fuel ratio. Switching between 87 and 93 octane pump gas in any stock production vehicle that's designed for 87 octane should be completely seamless. If anything, the higher octane might allow the knock sensor some time off and let the ignition run slightly more advanced, thus improving throttle response. Also, the additive packages in the 93 octane fuels may also yield slightly higher energy densities in the fuel, allowing slightly higher output and better fuel economy.

I'm not sure which brand of fuel you were using, and what the condition of the fuel itself was, but if the fuel was stale, or if its physical and chemical properties differed significantly from pump gas, then I can understand how you would have problems. However, if the fuel was fresh and it was something like VP Performance Unleaded or 76 Unleaded Racing Fuel which are both oxygenated, 100 octane, unleaded fuels, then I would be surprised that your bike noticed a difference.
Title: Re: Bike Problem or Bad Fuel?
Post by: Xian_13 on September 09, 2002, 06:51:10 PM
 ??? Hum...
When it comes to gas, it seems that there are alot of people that only know half the story... I am sure I am one of them.

Octane rating... This is the rating given to the gas based off of its combustion factor. Meaning the high the octane, the less chance of it firing with out ignition. (desieling).

High compression motors need high Octane. Piston knocking is pre-ignition of the gas, Lower Octane gasses ignite before they are meant to.

The wrong octane. If your motor is engineered to run 95 octane, you should NOT run less then 95. The compression will ignite lower octane fuels before ignition. If you run to high of octane, you have nothing to worry about. However... Higher octane fuels will hurt your proformance. I have seen the dyno results (no rejetting) from pump 97 to race 110.

If you lean out your motor (lean is faster, but runs hotter) you can gain HP, but if you are getting things to hot, you will cause the desieling effect (knocking, and under racing conditions, a blown motor). If you are jetted to run pump gas, and you are not lean , higher octane will hurt HP. High octane may cause a Fat effect.
Though I may be miss informed, but these are things I have seen off of the dyno.
Title: Re: Bike Problem or Bad Fuel?
Post by: tcchin on September 10, 2002, 02:00:00 PM
Knock is the sound of the piston rattling in the bore as the multiple flamefronts caused by detonation collide. Pre-ignition is silent.

Race fuels produce less power than pump gas if they are not oxygenated. Union 76 Super has produced three more peak horsepower than VP C12 on back-to-back dyno runs on a stock GSX-R600 because of its oxygen content. However, many of the oxygenated fuels become unstable in high-temperature conditions (Pike's Peak, Las Vegas, Phoenix, Willow Springs, Texas, etc.), and you need a more traditional fuel to keep your motor together.

Leaner is not faster. Stoichiometric mixtures are only efficient in theory. In fact, optimum power is achieved somewhere between 12.2:1 and 11.8:1, depending on the motor, the fuel and the atmosphere.

If you are jetted to run pump gas, then your jetting would be way too rich to run non-oxygenated race gas. Oxygenated race gas (Special 5, MR1, etc.) would probaly be a closer match. This has nothing to do with octane ratings and everything to do with oxygen percentages.
Title: Re: Bike Problem or Bad Fuel?
Post by: pmoravek on September 11, 2002, 02:48:54 PM
Huh?
Title: Re: Bike Problem or Bad Fuel?
Post by: unforgivenracing on February 11, 2003, 08:58:30 AM
I'm going to stay away from the gas issue and ask you something towards the other.
 Did you change the pipes on the bike?

Being that you have Fi, It could be the problem.
  If so, Try disconnecting the battery, wait a while, reconnect, and run the bike (with the desired fuel of your choice) for about 125miles.
This will reboot the memorie and allow the computer to recal the fuel setting via the new reading it receives without it thinking there is a problem it is trying to fix.  It is a computer after all. this trick works for other things too.
Title: Re: Bike Problem or Bad Fuel?
Post by: Litespeed on February 11, 2003, 10:36:41 AM
Getting bad race gas is a common thing at tracks.  It used to happen about every other outing to at least one of my friends when I was drag racing.  Getting bad gas from the local station isn't as likely because they run through it so quickly.  IF your bike doesn't need the octane don't buy it.  If your bike does need the octane, make sure you get it from a reliable source in a sealed container.
Title: Re: Bike Problem or Bad Fuel?
Post by: TZ_Boy on February 11, 2003, 06:44:40 PM
QuoteI'm going to stay away from the gas issue and ask you something towards the other.
 Did you change the pipes on the bike?

Being that you have Fi, It could be the problem.
  If so, Try disconnecting the battery, wait a while, reconnect, and run the bike (with the desired fuel of your choice) for about 125miles.
This will reboot the memorie and allow the computer to recal the fuel setting via the new reading it receives without it thinking there is a problem it is trying to fix.  It is a computer after all. this trick works for other things too.
Sounds good except  the computer does not have memory, or different fuel settings, is unable to take readings, and is helpless to fix itself.
Title: Re: Bike Problem or Bad Fuel?
Post by: TZ_Boy on February 11, 2003, 06:48:01 PM
QuoteThanks for your input. I didn't specify in my first post, but I did run 100 octane unleaded race fuel. I know better than to run leaded in a bike that requires unleaded only. Sorry for the lack of info.
What is wrong with running leaded in a bike that requires unleaded?
Title: Re: Bike Problem or Bad Fuel?
Post by: unforgivenracing on February 12, 2003, 12:22:54 PM
QuoteWhat is wrong with running leaded in a bike that requires unleaded?
Yea, I was wondering that too.  I would think that the presents of a lead additive would help prevent damage to the valves.  Or am I going crazy?
Title: Re: Bike Problem or Bad Fuel?
Post by: unforgivenracing on February 12, 2003, 12:29:22 PM
QuoteSounds good except  the computer does not have memory, or different fuel settings, is unable to take readings, and is helpless to fix itself.
The computer doesnt have a memory per-say, but does take readings from all those sensors located on the bike.  Those sensors tell the system what map would work best for the task,elevation,temp,pressure,ect.  The manufacture(honda) has at least three different maps in the stock computer.  I know this!
Title: Re: Bike Problem or Bad Fuel?
Post by: unforgivenracing on February 12, 2003, 12:32:30 PM
QuoteGetting bad race gas is a common thing at tracks.  It used to happen about every other outing to at least one of my friends when I was drag racing.  Getting bad gas from the local station isn't as likely because they run through it so quickly.  IF your bike doesn't need the octane don't buy it.  If your bike does need the octane, make sure you get it from a reliable source in a sealed container.
This I agree with fully.  Nutec is good stuff but $$$$$.
Title: Re: Bike Problem or Bad Fuel?
Post by: TZ_Boy on February 12, 2003, 05:32:16 PM
QuoteThe computer doesnt have a memory per-say, but does take readings from all those sensors located on the bike.  Those sensors tell the system what map would work best for the task,elevation,temp,pressure,ect.  The manufacture(honda) has at least three different maps in the stock computer.  I know this!
True it does have sensors to adjust for bike temp, outside temp, throttle posistion, Mass Airflow etc.. but it can not determine the type of fuel you are running.  It does not have a closed loop system which means it does not have a sensor in the exhaust to check air/fuel ratio so it is helpless to correct itself.
Title: Re: Bike Problem or Bad Fuel?
Post by: unforgivenracing on February 12, 2003, 05:43:43 PM
Hey, tell you what  :)buy a RC51, ride it for six hundred miles, put a full exhaust on it as then rev it up a few miles.  (The result will be some nice flames out the rear.) :o Now, do the battery thing, and tell me why the other thing went away. >:(  If I can get this answered I can talk myself in to a powercommander lllr and Map.  But the problem right now is that mine runs as good without it as some others do with it. 8)
Title: Re: Bike Problem or Bad Fuel?
Post by: Litespeed on February 13, 2003, 01:14:09 PM
QuoteHey, tell you what  :)buy a RC51, ride it for six hundred miles, put a full exhaust on it as then rev it up a few miles.  (The result will be some nice flames out the rear.) :o Now, do the battery thing, and tell me why the other thing went away. >:(  If I can get this answered I can talk myself in to a powercommander lll and Map.  But the problem right now is that mine runs as good without it as some others do with it. 8)

The bikes computer has no idea what the outcome of it's calculations is based on the fact it has no Oxygen Sensor.  It is merely a computer that accepts inputs from it's sensors, looks up a number from a PRE-PROGRAMMED table and executes what the table says.  There is no learning involved based on the fact it's an open loop system.  As far as removing the battery fixing it?  There are other things that changed like the atmospheric conditions etc.
Title: Re: Bike Problem or Bad Fuel?The wrong octane. If
Post by: Super Dave on February 14, 2003, 07:17:04 AM
Cool, a fuel thread...

QuoteThe wrong octane. If your motor is engineered to run 95 octane, you should NOT run less then 95. The compression will ignite lower octane fuels before ignition. If you run to high of octane, you have nothing to worry about. However... Higher octane fuels will hurt your proformance. I have seen the dyno results (no rejetting) from pump 97 to race 110.

Higher octane does not hurt performance.  If you go from unleaded pump 97 to leaded 110 without changes, yes.  You have to look at all the factors.

Leaded fuels burn more uniformly and completely than an unleaded.  So, given equal amounts of fuel going in, you would be lean using an unleaded...less power.

All fuels have a weight, their specific gravity.  The fuel moves through an hole of a specific size.  If the fuel is heavier and it goes through a particular hole, so much fuel will go through.  If the fuel is lighter, more fuel will go through.

If the fuel is oxygenated, then there is less fuel in the mixture.  So, to have the same amount of hydrocarbons going through our jet to maintain proper mixture, you need to jet up.

Some fuels have properties that cause them to burn slow, with a lot of heat, and with a lot of debris.  This is the fuel that you can buy from the race track.  And where did that fuel come from?  What was in the container before that?  How many trucks moved it and what did they have in them before transport?  Diesel?  Home heating oil?  Methanol?

And rules...

CCS rules as they are written do not allow Leaded Oxygenated Racing Fuels.   Additionally, they do not allow unleaded street gas.  If anyone tells you otherwise, they don't know what they are talking about. The rules, as they are written, only allow simple, leaded, non-oxygenated racing fuels.  The rules were re written at the beginning of 2001 with no announcement.  I have been trying to get them changed since the end of 2001, but to no avail, even though I wrote new fuel rules for CCS.  
Title: Re: Bike Problem or Bad Fuel?
Post by: tcchin on February 18, 2003, 01:32:51 PM
QuoteThe fuel moves through an hole of a specific size.  If the fuel is heavier and it goes through a particular hole, so much fuel will go through.  If the fuel is lighter, more fuel will go through.

I'm confused: 1) Fluids are effectively incompressible, so the same volume of fuel should pass through a fixed orifice (jet) regardless of the fuel's specific gravity, assuming that the fuels' viscosities are the same; 2) Air/fuel ratios are expressed in terms of mass, not volume, so if a lighter fuel (lower specific gravity) passes through a fixed orifice (jet), it will do so at a lower mass flux rate, resulting in a leaner mixture, right?
Title: Re: Bike Problem or Bad Fuel?
Post by: Super Dave on February 19, 2003, 03:11:40 AM
Given the same hole...  when comparing two fuels with different specific gravities, everything else is the same, the fuel that is lighter will have more fuel, more hydrocarbons, go through it than a fuel with a heavier specific gravity.

So, as an example, in a Busch motored race car.  You use Power Mist T111 with a specific gravity of .718.  You move to Power Mist T112 with a specific gravity of .728.  Given the same jets, running T112, the jetting will be lean.  And in an oval track Busch motor type application, you would need to richen the jetting by one size to have the same air fuel ratio.

Add oxygen to the fuel, given the same specific gravity, and you will need to richen the jetting.  Because, there is oxygen present in the mixture that is not a fuel.  You need the same air fuel mixture.
Title: Re: Bike Problem or Bad Fuel?
Post by: tcchin on February 19, 2003, 12:06:48 PM
Are you saying that lower SG fuels have a higher hydrocarbon count per unit volume than higher SG fuels, or that they are less viscous than higher SG fuels such that they yield higher flow rates through a fixed orifice? Again, fuel ratios are expressed in terms of mass fractions, not volume fractions, so given volume of a lighter fuel will yield a leaner mixture when mixed with air than the same volume of heavier fuel, oxygenates notwithstanding.
Title: Re: Bike Problem or Bad Fuel?
Post by: Dawn on February 19, 2003, 03:15:21 PM
QuoteAre you saying that lower SG fuels have a higher hydrocarbon count per unit volume than higher SG fuels, or that they are less viscous than higher SG fuels such that they yield higher flow rates through a fixed orifice? Again, fuel ratios are expressed in terms of mass fractions, not volume fractions, so given volume of a lighter fuel will yield a leaner mixture when mixed with air than the same volume of heavier fuel, oxygenates notwithstanding.

You know...

This whole fuel conversation is pretty interesting, Paul would understand it.  As for myself - - not so much.

Dawn   :-/
Title: Re: Bike Problem or Bad Fuel?
Post by: unforgivenracing on April 03, 2003, 03:01:26 PM
Just get your bike drunk, the hole will not matter.
QuoteI'm confused: 1) Fluids are effectively incompressible, so the same volume of fuel should pass through a fixed orifice (jet) regardless of the fuel's specific gravity, assuming that the fuels' viscosities are the same; 2) Air/fuel ratios are expressed in terms of mass, not volume, so if a lighter fuel (lower specific gravity) passes through a fixed orifice (jet), it will do so at a lower mass flux rate, resulting in a leaner mixture, right?
Title: Re: Bike Problem or Bad Fuel?
Post by: tcchin on April 09, 2003, 04:31:31 PM
Truer words were never spoken!
Title: Re: Bike Problem or Bad Fuel?
Post by: unforgivenracing on May 12, 2003, 04:31:58 PM
installing a exhaust sensor will not make it a closed loop system either.  SO, :P
but the bike does know Threw its formentioned sensors how much pressure is around.  you need to look at the whole.  Give up, we both have valid points.  let the guy get his fuel question answered. ;)
QuoteThe bikes computer has no idea what the outcome of it's calculations is based on the fact it has no Oxygen Sensor.  It is merely a computer that accepts inputs from it's sensors, looks up a number from a PRE-PROGRAMMED table and executes what the table says.  There is no learning involved based on the fact it's an open loop system.  As far as removing the battery fixing it?  There are other things that changed like the atmospheric conditions etc.