AvGas ok for Fuel injected PWC engines?

S

SierraPilot123

Well-Known Member
Anyone know if it is OK to use AvGas for a Honda Fuel injected Turbo-charged PWC engine? A similar engine to the CBR motobike I beleive.

I added a stage 1 kit and chip that increases my boost. It requires that I run an increased octane over 91 to gain the most performance for racing.

Could I mix 1/2 or a 1/4 100LL and 91 pump fuel?

I can't find any info on this and have searched everywhere. None of the jetski racers know much about AvGas. What makes Avgas so special and what makes it good or bad to run in a suped-up fuel injected engine?

The mechanics give away the gas they drain from the planes (so it is readily available), but tell me that it is only ok for carb equipped boats. Why would this be? Is this really true or a myth?

Thanks a ton.

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SierraPilot123 said:
Anyone know if it is OK to use AvGas for a Honda Fuel injected Turbo-charged PWC engine? A similar engine to the CBR motobike I beleive.

I added a stage 1 kit and chip that increases my boost. It requires that I run an increased octane over 91 to gain the most performance for racing.

Could I mix 1/2 or a 1/4 100LL and 91 pump fuel?

I can't find any info on this and have searched everywhere. None of the jetski racers know much about AvGas. What makes Avgas so special and what makes it good or bad to run in a suped-up fuel injected engine?

The mechanics give away the gas they drain from the planes (so it is readily available), but tell me that it is only ok for carb equipped boats. Why would this be? Is this really true or a myth?

Thanks a ton.

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02HondaEng.gif
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There is lead in Avgas at it will really JAG UP your sensors in that thing. I think you should look into Torco or VP fuels.
 
It would really depend on your setup. Some fuel injected engines on motorcycles just use a fuel map based on throttle angle, engine speed, and barometric pressure and temp. These might be ok with the lead.

If your engine has oxygen sensors in the exhaust that the computer uses to refine the mixture settings, lead would probably not be a good idea.

That is probably the reason they are telling you lead is only ok with carbureted engines. They don't have any sensors in the exhaust that will get covered with lead deposits.
 
I know nothing about motorcycles, but if the exhaust sysem has a cataylitic converter, using any fuel with lead will render it INOP.
 
Oh, wait, are we talking about a boat or a motorcycle? If its a boat, I highly doubt it would have a cat, so that wouldn't be an issue.
 
desertdog71 said:
I use VP 109 in my car and have never had any issues. It is unleaded.
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That is a pretty impressive octane rating for unleaded. I have always wondered how 100LL compares to the older avgas that had the dual number rich/lean ratings, and how these would compare to how auto fuel is rated. Probably never get an answer, but I'm still curious.

How much does that VP 109 cost, and what type of engine are you running that needs that high of an octane rating?
 
The aquatrax turbo doesn't have an o2 or cat. Those are the big issues with using leaded gas, so you should be golden.
 
averyrm said:
The aquatrax turbo doesn't have an o2 or cat. Those are the big issues with using leaded gas, so you should be golden.
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Hmm it sounds like it is a split decision.

Not it isn't a boat engine but a PWC or Jetski engine for the Honda Aquatrax. It is rated for ultra low emissions so it must have some type of sensors.

averyrm how do you know there are no O2 or cat converters?

With a few people saying yes and a few saying no it doesn't give me much confidence to run AvGas. I haven't been able to find the VP gas around here and it is around $8 a gallon for 100+.

After doing some more research I found out that I only need to run 93 and not 100. But the pumps around here are only 87, 89, and 91. Is this a California thing?
 
ananoman said:
That is a pretty impressive octane rating for unleaded. I have always wondered how 100LL compares to the older avgas that had the dual number rich/lean ratings, and how these would compare to how auto fuel is rated. Probably never get an answer, but I'm still curious.

How much does that VP 109 cost, and what type of engine are you running that needs that high of an octane rating?
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I run it in a high boost 3.8 L67 in my Buick Regal. :)

Takes care of any knock issues.
 
Look at the parts diagram for it. No "Sensor, o2" or "catalytic converter"

But 93's probly cheaper, try Sunoco.
 
The parts diagram would be good, but all you should have to do is look, most cat converters are pretty obvious, as are O2 sensors. I'm not big on PWC, but any aftermarket performance exhaust probably does not have a converter.
 
Wow you guys impress me with your knowledge, especially averyrm.

I did a lot more goggle research and found a group of guys that have experience with AvGas and PWCs. Yes there are NO O2 sensors and NO Cat so that is good. But it turns out that the extra lead can wear out the expensive iridium spark plugs quicker. It is a Honda so most of the components last a long time. Anyhow a couple of guys use AvGas from time to time and have not had any problems thus far. Sounds like a split decision to me. They both make good points.

Side A

"Just like many an expert [friends who are exxon engineers] have said, "Avgas has no place in a land engine".
The best reasons are:
It's full of deicing agents.
Is full of dye [to identify fuel grade i.e blue is 100 LL and to show leakage from bladder tanks in the wings].
It has a bunch of vapor pressure additives.
It contains enough lead to foul plugs [we see it during runup / mag checks all the time].
The only good thing about avgas is... It smells great when checking the sumps for water.
Use vp race gas instead."


Side B

"Totally disagree. 100 LL is low lead.

-Many aircraft engines are turbocharged, and have a high effective compression ratio.
-I have been using LL (low lead) aviation fuel for 15 years, it works just fine and will not create any problems for your Honda. It sometimes has a rotten egg smell from the exhaust, but will work just as good as any other 100 octane.
-Lead sometimes plays havoc with oxygen sensors, but the Honda does not have an O2 sensor.
-I'm not speaking from what I've read on an internet forum, I've probably burnt over 1000 gallons of AvGas in dunebuggies and off road cars over the last 15 years. I know what it can do.
-At 3.75/gal, you need to figure out if it's cost effective over $6 gallon 111 octane when mixing to achieve a certain octane rating in a tank of gas."
------

There is an article that states that AvGas is formulated different than land fuel and won't ignite as quick. Also, that the blue dye other ingredients are not so good for the engine. PDF attached.
----

Flyguy I think it is a Reg that you can't re-use fuel that has been drained during maintenance. I am sure someone knows the details. Anyhow, it is much cheaper than the $6-8 a gallon for VP and easier to get.
 
You are just going to have to decide whether you think it is worth it or not. Looks like the worst that could happen is some fouled plugs, which you may be able to fix by using a hotter plug. I don't really think that the dye, vapor pressure additives, and any anti-ice additives will cause any harm. The average airplane engine cost more than the car you probably drive, so I doubt that any of the additives can be that harmful. Same goes for the fuel system. The rubber bladders used in many airplanes are a lot more delicate than what you would find in most other vehicles.
 
ananoman said:
You are just going to have to decide whether you think it is worth it or not. Looks like the worst that could happen is some fouled plugs, which you may be able to fix by using a hotter plug. I don't really think that the dye, vapor pressure additives, and any anti-ice additives will cause any harm. The average airplane engine cost more than the car you probably drive, so I doubt that any of the additives can be that harmful. Same goes for the fuel system. The rubber bladders used in many airplanes are a lot more delicate than what you would find in most other vehicles.
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Hotter Plug in a forced induction engine? I disagree.

Here is a copy of an Article I wrote about engine knock for my customers. www.modbug.com is the website if you care. I was under the impression it had O2 sensors, my mistake on the engine in question. However forced induction is a subject I am quite familiar with.


Combating Engine Knock in your Forced Induction Engine.

What is Engine Knock?

Engine Knock is also referred to as premature detonation. As the piston in your engine travels up and down, there is a point in it’s travel where it stops and begins to travel in the other direction. Ideally, the force of burning fuel pushes down on the piston at exactly the moment that it reaches the top of its travel and begins to force it back downward (the power stroke of the cycle).

Now, because the fuel does not burn instantly, we change the timing of the spark in the combustion chamber. 0degrees of advance is considered to be this point where the piston turns around and goes the other way. Advance, is when the spark happens before the piston reaches this point. The number of degrees is measured in degrees of crankshaft rotation. So an engine running 14degrees of advance timing (noted by a positive number in scan tools), is creating the spark when the crankshaft is 14 degrees of rotation before each piston reaches this top of travel point. IF, the timing is advanced too far or engine gases ignite prematurly, the force will push down on the piston while it is still traveling upward. This doesn’t seem too bad until you consider the force of this “push”. It is equivalent to hitting your piston with a sledge hammer, and none of us would do THAT intentionally. This is what KNOCK does to our engines. The PCM (power control module) will account for engine knock and reduce timing, and other protective measures depending on the vehicle’s individual PCM program. This lessens the effectiveness of the Power Stroke of your engine. The PCM is protecting your engine from turning itself into scrap iron.

Forced-induction adds another twist to the equation. Boyle’s law states, that if you compress a gas, the gas is heated as a result. We don’t need to go into all the technical details here, but suffice that your supercharger is compressing the air that goes into your motor. Then, the compression stroke of the engine is compressing it further. When we increase the amount of boost to the engine, we also increase the heat of the air as it begins its path into the cylinder where it is compressed even further. Gasoline has a “flashpoint”. This is when the fuel will combust without the introduction of a spark. IF, this temperature is reached in the cylinder there is no more control over the timing of the burning of the fuel. THIS is where we need to take additional precautions when adding more boost to the engine.

There are several ways to combat this.
First, is to reduce the boost on the motor. We don’t want to do this, because if we can increase boost WITHOUT knock, we can increase both HP and Torque. So this option is not valid in this discussion.

Second is to have lower air temperatures going into the system to begin with. This is where a good quality (CAI) cold air intake comes in. The factory intake system is designed for many purposes, the least of which is HP. One of the largest considerations in a factory intake system is the amount of noise it lets out. The factory combats noise by PURPOSELY putting some restriction into the intake. This increases the velocity of the air going into the engine, but decreases the ability to flow large amounts of air in a short time frame. This is why throttle response is improved with a CAI, because the engine can take a GULP of air instead of a long sip like from the factory intake. The closer to true outside air temperature you can get with an intake, the better. This is the reason that many forced induction vehicles also use an intercooler, alcohol injection, Nitrous Oxide and other methods to cool intake air.

Third is to decrease the temperature inside your engine. This can be accomplished a couple ways, or both for even better results. One, is to decrease the temperature rating on the thermostat. This rating sets the temperature when the thermostat opens, and the base operating temperature of the engine. Most stock thermostats are 195 degree thermostats. Remember, “flashpoint” is a fixed number. One degree below the flashpoint and knock won’t happen, so 1 degree of temperature decrease CAN make all the difference in the world. This is why many people that modify forced induction vehicles will use a colder thermostat. 180 or 160 degrees for example. The other way is to decrease the temperature rating or (Heat Range)of the spark plugs.

Spark plugs and temperature ratings simplified:

The temperature rating on a spark plug does not indicate how much heat it creates! or how hot the spark is. What the Heat Range indicates, is how fast the plug body takes heat AWAY from the cylinder. Yes! That is really how it works. That being considered, we want to keep the temperature inside the cylinder down. After the fuel burns, it gets exceptionally HOT. The faster we can take that heat away from the cylinder, the better. NOW, if we take the heat away too fast, the plug will get fouled quickly and not be effective in creating a good solid spark to ignite the fuel. So a balance has to be maintained. Email us and we will be happy to tell you which plug temperature is best for your particular needs based on modifications.

Fourth, we can improve the flow OUT of the combustion chamber. If we add too much boost on the intake side, and don’t account for how the exhaust gets out, boost can pile up. Sometimes referred to as “boost-stacking”. Basically, this means the cylinder is not starting with 0 pressure when it should. There is residual pressure in the chamber, because the exhaust system cannot clear it out fast enough. THIS is where a good exhaust system comes in. Headers can actually DECREASE the amount of boost you apply to your engine. WHY? This is because ALL of the exhaust gas can escape, and the cylinder is starting over with Zero residual pressure. This allows you to step up more boost with yet a smaller pulley, with the same net boost as a result. BUT, with more air volume flowing through the engine. This equates to even more power.

Lastly, The fuel you feed your engine is key. Lower Octane Fuels have a lower flashpoint temparature. This makes low octane fuel very suceptable to knocking. Use the highest octane fuel available to you, and when operating at Wide Open Throttle it is best to use a Higher Octane Racing Fuel, these can be found at Auto Parts Stores and Race Tracks all around the country in 94-109 Octane ratings.

As you can see, it is very important to address these Engine Knock Issues in order to get the most from your engine. A car running too small a pulley for the supporting modifications, will actually run SLOWER than one running a larger pulley with no knock. The PCM will adjust for knock as we stated before and rob your engine of the power you just tried to add. We have been modifying modern, forced-induction vehicles for years. Todays PCM/ECU programing must be understood in order to get the most out of your enigine. This is not new to us. Old School ideas are great but they can only take you so far, todays complex engines must be handled properly in order to get the most out them, while still protecting it. We are happy to help out with a game plan for your vehicle, regardless of where you purchase your products.
 
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