DirtRider . Net MX, SX, Arena Cross, Off-Road Community
Dirt Rider . Net Text Version Home
Dirt Bike Dirt Bike Dirt Bike Dirt Bike

This is the text version of DirtRider.Net
Click Here for the Full Version


Pages: 1

Some info for you Race gas users

(Click here to view the original thread with full colors/images)

Posted by: Jeff Howe

I had heard recently that Turbo Blue was produced by Sunoco so I went and compared specs. Sure enough Turbo Blue Unleaded matches Sunoco GT100 and TurboBlue Unleaded Plus matches Sunoco GT Plus 104. I am currently trying out Sunoco GT Plus 104 and jetting changes from Turbo Blue Leaded (which I ran last year) are alot different. Bike feels a bit more crisp.

I had to go 3 sizes up on the main (175 to 190) and needle clip from #3 to #4. Do you any of you experts think I will need to up the pilot one size too. It seems ok as it is, but I have not ridden on this GT Plus 104 yet, first ride on it will be tomorrow afternoon.


Posted by: steve125

Im really suprised you had to go that rich with just 3.5% 02. Ive been tuning with VP U-2 and U-4 for years now and have never had to vary more than 1 jet size richer with its 6% 02. I see the Sunoco's EP temp is low, under 300, that will richen it up over pump fuel.

With U-2 or the U-4 my jetting for 70+ degrees has been 1 leaner clip(2nd position) and 168-170 main(stock 178). Feels like the top end pull is up 2 hp over stock, and the plugs fuel ring is perfect after a 4th gear pull and throttle chop. This is for the 05 YZ 250.


Posted by: Jeff Howe

Well, I really had no idea what jetting oxy fuel would be like since this is my first time with it. I AM playing somewhat safe but the absolute leanest I can go is going to be 185 on the main.


Posted by: Jeff Howe

I got a good ride in tonight and to say I'm impressed is stating it mildly. I would have never imagined one could gain so much from a oxygenated fuel. I am good on the main jet but I could go one notch leaner on the needle. Steve, my cylinder is ported...mid/top if that means anything. right now it's probably more then I can handle so I'm a bit concerned of going leaner on the needle. Holy crap this thing rips!!

Anyway, just wanted to share what I learned regarding Turbo Blue and Sunoco. I never thought I would be spending $5.50/gal on race gas but there is NO way I'm going back. Its either TB Unleaded Plus or Sunoco GT Plus 104 (same thing) from now on for me. Why did I wait so long???


Posted by: drz400e

Have any of mixed your own race fuels?
3 products that are readily available are toluene,Xylene and MTB
Here is the link for a quick reference guide to mixing fuels
http://www.easyperformance.com/Octa...rd_Frameset.htm

It's definatly cheaper than buying race fuel!


Posted by: Rich Rohrich

Quote:
Originally Posted by drz400e
Have any of mixed your own race fuels?
3 products that are readily available are toluene,Xylene and MTB
Here is the link for a quick reference guide to mixing fuels
http://www.easyperformance.com/Octa...rd_Frameset.htm

It's definatly cheaper than buying race fuel!



In short, if you want to run pump fuel you are going to trade off some performance and response PERIOD, and no combination of additives from the local chemical supply store will change that. Whether or not that trade off is an issue is up to you decide.

While on the surface that looks like a nice little website there are some important issues that it doesn't address. Additives like you noted do NOT blend linearly in pump gas. So you can't do some simple math and be sure how much change you'll make by adding an octane booster. They tend to act differently when they are mixed with different base components. The octane values of Toluene and Xylene are routinely overstated. The blending octane value of even reference grade Toluene is no where near 114 (which is the number commonly thrown around), and neither Toluene or Xylene has a usuable MON value greater than 101.5 which is the value we're really concerned with anyway.

Adding 10% by volume of an aromatic component like Toluene or Xylene is an excellent way to make the throttle response really flat, and kill the flame speed of the fuel to the point where power will be reduced at high rpm. Race fuels that use high levels of Toluene will usually have olefinic components added in an attempt to improve flame speed. These components are strictly limited in pump fuel, so you end up with incredibly lazy throttle response with even moderate levels of aromatics added to pump fuel.

MTBE is an oxygenated component that has great potential in race engines, but due to it's high cost it's not a component you see in octane boosters very often. When it is used it has a PROFOUND effect on the jetting becuase it carries it's own oxygen and it's chemically correct air/fuel ratio is ~11.7:1 versus ~14.5:1 for current oxygenated pump fuels.

Toluene is a decent additive if all you want to do is protect the engine from fragging itself due to detonation. It has reasonably high octane and it is relatively cheap. The downside is additves like these are fairly reluctant to vaporize so they make for sloppy throttle response noted earlier, poor carb circuit transitions and poor high rpm running in engines like ours that have short intake tracts.

I think it's also worth noting that there are different types of Xylenes with distinctly different behaviours in an engine. o-Xylene (1,2-dimethylbenzene), m-Xylene (1,3-dimethylbenzene), and p-Xylene (1,4-dimethylbenzene) are commonly available . You can see that the ring structure is completely different on each one, which changes it's behaviour in the combustion chamber as well.

On the surface the Xylenes seem pretty attractive as a fuel additive but they present a number of problems. You need 272 times as much Xylene by weight compared to tera-ethyl lead (TEL) to get an anti-knock effect similar to TEL. As you increase the percentage of aromatic hydrocarbons like Xylene to the levels we're describing you'll see a marked drop off in throttle response in a normally aspirated engine. The same is true in blown applications, it's just less severe. In a normally aspirated (NA) engine poor throttle response , lazy
combustion and subsequent need for increases in ignition advance are common side effects with high percentages of aromatics like Xylene. The difficulty in getting Xylene to vaporize is a critical factor with it's use in a unblown engine.

Blown applications have considerably more heat available in the
intake tract to help Xylene vaporize completely. Xylene has nice high octane numbers , but in practice it seems like these numbers are only atainable when you mix Xylene with high alkylate base fuels (like AvGas) or when TEL is present.

In air cooled turbo drag race applications I've had great luck with Xylene, but it's been nothing but a disappointment in unblown engines that see constantly changing throttle openings.Once you get past about 2-4 oz/gal most of the good high octane aromatic hydrocarbons (Toluene, Analine, Benzene, Xylene, etc ) become more trouble than they are worth in a dirt bike or road race application.

Here's some additional info on MTBE for those of you who have dozed off YET.

AMA legal race fuels with MTBE generally contain about 15% by volume and subsequently have a lower energy per pound. You have to look at the big picture to see how this works in our favor.

Here's a few numbers to explain things :


Typical leaded race fuel (no oxygenates) = 18636 (BTU/lb)
Typical unleaded race fuel (with ~15% MTBE by vol) = 17876 (BTU/lb)
MTBE = 16353 (BTU/lb)

As you can see the addition of MTBE lowers the overall energy value. So on the surface it looks like the leaded race fuel with highery energy content would make more power. But we know it doesn't. HOW COME?

We have to look a little deeper and figure out the heat available in the cylinder per pound of air. If we look at the chemically correct (Stoichiometric Ratio) air/fuel ratio of our non-MTBE fuel we see it's 14.88 while the MTBE laced fuel has a Stoichiometric Ratio of 14.15 (for reference MTBE is 11.76) . So that tells us we need to add more fuel for each pound of air we ingest into the cylinder when we are using an MTBE based fuel. In this particualr example we would need to add 1.016 times more fuel with the MTBE based fuel (1.228 for pure MTBE).

So we have more fuel in the cylinder for each pound of air with our oxygenated fuel and the actual heat available in the cylinder per pound of air (or specific energy)looks like this:

Typical unleaded race fuel (~15% MTBE by vol) = 1263 BTU/lb of air
Typical leaded race fuel (no oxygenates) = 1252 BTU/lb of air

MTBE = 1391 BTU/lb of air

So as you can see even though the non-oxygenated fuel started with an advantage sitting in our fuel can once it got around to doing some real work it loses the race.

The super-fuels Nitromethane and Methanol have similar characteristics to our MTBE-fuel. Lower energy per pound but higher specific energy when you add in enough fuel to compensate for their lower stoichiometric ratios ( about 6.47 for Methanol and about 2.1 for Nitromethane). All that extra fuel adds up to lots of extra oomph.

At the end of the day, you can't beat a properly designed race fuel with some homebrew pump gas based chemical melange.

*** If anyone wants specific references for the numbers I listed above just let me know.


Posted by: drz400e

Rich: You type fast!!!!


Posted by: drz400e

Rich: Would lets say 10% Toluene to Premeium pump fuel help eliminate the ping in my drz400e at low rpm?

My still produces 95% odorless tasteless alcohol. Could I mix that with pump fuel for more oomph or should I just stick to drinking my homebrew?


Posted by: Rich Rohrich

Quote:
Originally Posted by drz400e
Rich: Would lets say 10% Toluene to Premeium pump fuel help eliminate the ping in my drz400e at low rpm?


Maybe. The problem you run into with Toluene is it's high distillation temperature. At small throttle openings it's very possible the Toluene won't vaporize completely and won't contribute to the overall octane of the fuel. Best bet is to try it and see what happens. You won't hurt anything but the throttle response at 10%.


Quote:
Originally Posted by drz400e
My still produces 95% odorless tasteless alcohol. Could I mix that with pump fuel for more oomph or should I just stick to drinking my homebrew?


Alcohol has enough negatives associated with corrosion and water attraction to keep me from ever recommending it to anyone for a general use engine.


Posted by: drz400e

Net ride I will try 10% Toluene and will let you know how it works.

Thanks


Posted by: happy hacker

DRZ400E

5% toluene mixed with 92% octane fuel (premium) if your from Canada "eh"
is all you need to get rid of the pinging at low rpm under load. I don't think that
it reduces throttle response what so ever but try it yourself.

Are you using a thinner base gasket to raise compression?


Posted by: GKL

for us, our pump gas is always changing blends throughout the year + it's not high enough octane. The only way we can get consistant fuel and being able to jet consistantly from race to race is to use race fuel.


Posted by: Hart89

Here in Australia Shell has just release a fuel with a 100 octane rating with only 5% ethanol from the bowser. Surely there is higher octane fuel then 92 in canada or is it crazily priced?


Posted by: Rich Rohrich

The Shell Optimax Extreme 100 octane fuel they released in Australia is a 100 RON fuel. Which on the scale used in the US and Canada at the pump (MON + RON) / 2 , would make it a 94 or 95 octane fuel. It's an improvement but not as big a difference as the raw numbers would indicate.

In most parts of North America the fuel will be lower octane at high altitude locations, because the octane requirements of engines run inverse to altitude. In other words the higher the altitude the lower the octane your engine will need to avoid knocking.



This is the text version of DirtRider.Net
Click Here for the Full Version

Text Version Home





vBulletin Copyright ©2000 - 2008, Jelsoft Enterprises Limited.
vB Easy Archive Final ©2000 - 2008 - Created by Stefan "Xenon" Kaeser