PHall

I have been racing boats for a number of years and I am now getting into speed planes. I mixed my own fuel for boats and I was wondering if anybody here does it for planes. How high can I go on nitro and how much oil? Or is their any advantage to higher nitro?

Flying freak

Can i ask you were you get nitro? (nitromethan) is it over the internet is there a local way?

Steven

PHall

I buy from World Wide Racing Fuels outside of Richmond, VA.

Flying freak

Thank you,

brewski

Here is where I buy nitro from. They ship a short case (2 gal.) but it is more economical to buy a full case since the hazmat fee is the same for either.

As far as mixing fuel for your planes there are alot of variables to consider. You will get tons of info on the glow fuel forum.

http://www.shop.pricechemical.com/ca...g?categoryId=4

Destiny-RCU

Reducing drag on an airframe makes more difference than increasing Nitro.
Start with a nice sleek plane and it will go fast with no nitro.

combatpigg

My Feedback: (3)

The guys who run real high nitro change pistons every round. If you want to buy your own ingredients locally, ask around at the local oval track, drag strip, or just look in the phone book under fuel..

HighPlains

My Feedback: (1)

Anything less than 25% is mild sport fuel.
Up to 40% is nearly idiot proof.
65 to 70% can easily send piston material out the exhaust if you are slightly lean, but pretty easy to master. However, the plug cost might exclude going that high, since they are only good for one flight.

Oil really depends on the engine, but 18% seems pretty safe.

bob27s

My Feedback: (19)

Playing with fuel was my least favoite thing about F-1 years ago... Second least thing was buying glow-bee plugs by the pound.... running a close 3rd was the inevitable exploding bladder tank.

Im sure there are a few folks who prefer to blend their own fuel. Ive always been all up for experimenting in years past. Heck, I even tried hydrogen Peroxide

These days what comes out of the jug from PM, WC, OM, RB, or what ever is good for me.

I've not run anything over 30% nitro in quite a while ... and that is the heli fuel.

As was noted... yes, you might get another 1500 rpm out of a properly tweeked engine, the right prop, a good pipe setup, and a crap load of nitro.... but when it results in about 3-4 mph on the top end aircraft speed.... its kinda a waste for just sport-speed flying.

PHall

Why do think these engines come apart? We run the marine stuff at the same and higher rpm without failure and rarely a burnt plug. This is using 60% nitro and 12% oil. There probably is not as much heat with marine but nitro tends to cool and engine and more oil should help compensate for heat as well.

combatpigg

My Feedback: (3)

You're engines aren't loaded the same as ours........different environment, too.

proptop

My Feedback: (8)

Does the Marine engine's water cooling head or jacket make for more consistent runs and longevity? (longevity being a relative term here...)
I mean there's less temp. fluctuation?

combatpigg

My Feedback: (3)

Take whatever your marine engine weighs and find the equivalent weight aircraft engine, then look up what size prop the aircraft engine turns. Now bolt that prop up to your marine engine and use it to pull around a swamp buggy, using your ordinary marine fuel. I'll bet this experiment will show that marine engines are very good at what they are designed to do and that aircraft engines are very good at what they are designed for.

PHall

combatpigg, I have been thinking about this.

If an airplane has more drag then why are they going almost 200mph when the best a boat can do is 126mph? I think that analogy is false. A large prop on a plane will fly. A large prop on a boat will not get you off the bank. As for torque, it takes a considerable amount to get a boat to launch.

Either way, a certain cu.in. motor will put out a certain horsepower. A fast plane compared to a fast boat with the same size engine have both obviously reached peak performance from there engines. The relation between rpm and torque are the only variation.

If my motor is made from lead it will weigh more. So therefore the performance suffers? I don't understand where you are going.

proptop,
Water cooling is helpful. We are able to cool down a motor at will. They must be under more load to be building more heat in my opinion. However, we all try to maintain a hot enough but cool enough engine temp no matter what the vehicle. Think about it. They all have the same construction.


bob27s,
Thanks

proptop

My Feedback: (8)

I agree with you about their construction.
I was just thinking about the early K&B 7.5 inboard that I had recently converted (from marine ) to aircraft use...it's basically the same engine except for the head and flywheel...all I had to do was swap the heads and a prop driver for the flywheel and now I have a RIRE (disc rotor ) 7.5 similar to an SRII 6.5 [8D]

R/C boat engines, generally speaking have wilder timing, correct? They use open pipes and turn some rather high r.p.m. too, right? (r.p.m. that for an aircraft engine is usually reserved for engines like Nelson, Jett or the old K&B F-1 or DF engines, etc...)

The H.P. and torque curves are different for the two types, so to me it's (to use that over-used analogy ) like comparing apples and oranges...(isn't it?)

Not exactly sure where I'm going with this...

To me, the main similarity is that they both get their ability to turn a prop by winding the snot out of them? (not talking "sport" engines, but racing stuff here )

Edit: What I meant by the water cooling ? was the ability to keep a more consistent temp around the cylinder and therefore less (potentially anyway ) distortion for better piston/sleeve wear and seal? (true/false?)
Keeping a more stable temp. would allow you to put more load on the engine and/or run more nitro wouldn't it?

IMO a high performance marine engine is under substantially more stress than just about any aircraft engine...(from what I have seen anyway )

PHall

Proptop,
I have never measured a plane motor so I can not say at this point but I am about to find out.
RPMs are high, but some here quote even higher rpm, but in general I say yes.
Apples to oranges in a way, yes. Props are obviously different but the engines perform best at a certain rpm.
Water can be bad. We usually restrict the water to get more heat. Nitro actually cools the motor so that is why restrict water, run hotter/colder plugs, change head clearances and volumes and things of such. The funny thing I have found in the boat world is that the fastest and best running engines seem to be under the least "abusive" load. I say abusive because when you are lucky enough to be able to get the prop, pipe length, engine timings, and hull setup you can run more fuel (ie more oil and more power), not burn a plug, and the engine will barely be discolored on the inside. Lean ain't mean. I do believe a boat is under more load in general, but the fastest of the bunch must be under less load because they will hit a third stage on the pipe and I have even heard a 21 hit a fourth stage. Now you are turning some rpm at that point.

Between this and my other thread I think some may be trying to make this out into a plane and boat thing. It is not. I just know that in the boat world you can make almost any engine comparable to the next without sacrificing reliabilty. I only want some baseline information from the plane guys so to try it on my own. All I ever read is how fast something is but there are no numbers to describe the speed. 100 is fast for many, so how do I know when somebody is 100 fast or 175 fast?

Destiny-RCU

Yes this is really "apples to oranges". An .18 size boat/car engine makes more power than my Thunder Tiger .40. But they are each intended to be that way. In the boating world you want the most power out of a .xx size engine. Just take a look at the boat engines and car. They are all very high strung making a lot of power. Plane engines all have a different purpose unlike cars and boats. A slow .40LA is perfect for a piper cub, or a Big Stick. Cheap, reliable, and will run forever. What I mean is,in the boating world the engines are all designed for the same purpose...More Power!! (apples to apples)
plane engines have many different intended purposes
.40LA Vs. Q500 Nelson....Apples vs. oranges....And they will never meet performance wise

You have cheap reliable engines such as the .40LA
You have the "sport" catagory TT, ST, OS etc. Also reliable
You have 4 strokes, Good TQ!
And designed racing engines, Jett, Nelson...Only run well at high RPM and need the right prop to get there + a sleek plane that will unload.
The way I see it is you can mix the first 3 without much of a problem.
But none of them can be the 4th due to internal desing (rods, cranks,porting etc.)
Even if you want to mod a ST it won't match a Jett or a Nelson.

PHall

Destiny,
I agree with what you say to a point. Most engines are not produced to be balls to the wall. The reason being is that 90% of the people could not tune them and the manufacturer would soon have a bad reputation. As far as that goes probably 50% of the people I meet can't tune anything glow much less if it has a tuned pipe. However, just because an engine is produced with the average user in mind does not mean that the material and workmanship have been sacrificed. Picco and CMB are prime examples. They will not hold a match to a modified version of the same but they do last just as long. The only way I can link this to planes is through O.S.. A stock O.S. (and a LA is not even worth mentioning) can be modified to perform very well. As good as Jett or Nelson................NO. But then again, if you get within 10mph of a JETT or Nelson and you are sport flying, then I say you obtained something.

Anyway, I have talked with Jett and they are sending me a quickie pipe for my sport Jett 40 which should get me fairly close to where I need to be.

Jett has not returned my email yet, but does anybody have an idea of a top speed of a Diamond Dust/ Sport Jett 40 combo?

Destiny-RCU

I think with some this is true, but with others it's not. In a recent thread on here a guy did some "tweaking" on a TT40 and it made some respectable numbers and lasted. While others and a few Locals I know have had negative returns (bearings, Crank broke etc.). The second part to this is, is it worth the chance? Not really, as Bob27 noted. Tweaking and engine shows minimal gains on top end speed.

Reduce drag..Makes more difference
Reduce drag + a Jett 60LX....Now were talking

PHall

Bearings may very well be at risk. The boat motors use a phenolic retainer as oposed to the steel cage. The phenolic has a higher rpm rating in general.