snoopy5

I have a SC 70 four stroke glow engine. My friend says he uses Formula Irvine sport 5 glow fuel. It is 30% nitromethane and 18% oil. Is this ok for my engine or do have I to use other fuel. Not that I dont trust my friend but would rather use the correct fuel than be sorry. Can anyone specify the correct fuel.

many thanks

asmund

The oil is fine, I only use 15% myself. I am a little worried that 30% nitro might be a little overkill on that engine. I do have the SC 91 fs and ASP 180 fs that I want to try with 30% but I am a little hesitant to do it. I have read about broken crankshafts due to the use of 30% in Magnum fourstrokes. I do not fully understand why the crank will break as long as the engine is held within its normal rpm range however. Maybe someone will chime in here and explain??

Sport_Pilot

I am not aware of problems with broken cranks, even with 30% nitro. However, I do know that even if you keep the RPM in limits, with more nitro you may have to go to a bigger prop and so more torque is applied to the crank. Torque breaks crankshafts not RPM. RPM is hard on the con rod and the crank pin, but not so much the crank shaft itself.

asmund

I would think that going from 14-6 (15%) to 15-6 (30%) should be within the safety margin of the crank? Maybe there have only been a couple of "lemon" cranks that would break eventually regardless of % of nitro used??

Checklst

You are correct about the lemon cranks being the problem not the nitro...........

Marcol

Snoopy,
Irvine sport 5 is a fuel containing 5% Nitromethane NOT 30%.

Your engine will run ok on Sport 5 . But if you want the best get yourself some Prosynth 10%.

http://www.westonuk.co.uk/index_032.htm

snoopy5

Hi to everybody

thanks for your replys. Just to say in response to Marcol that it is www.Alansmodels.com that says there is 30% nitro in the Irvine sport 5 fuel. This is why I am asking you guys whats what, becasue they are saying different things and I am getting confused.

NM2K

My Feedback: (14)

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Bingo.

Unless they have changed the cranks in the .91 engines from a few years ago, I would NOT go there with higher nitro. Too many cranks have snapped when the engine appears to be whapping and running great.

You out there Tom? Tell them about yours.


Ed Cregger

Ken6PPC

I think you missed two very important words in that ad. It says UP TO 30%!

"Sport 5" would be 5% nitro, unless I am missing something too. (which is certainly possible.....)

speedster 1919

My Feedback: (3)

Snoopy IT makes sense Sport 5 has 5% nitro and the name changes with nitro content. Sport 5 looks like a dead ringer to Wildcat 5% here in the U.S. Since SC is the same as ASP and Magnum 70 which I have one of each. The manuals were fairly clear the best suggested fuels were 5%-10% nitro but if you had to 15% could be used (max) These engines were intended for Canada and Europe market for lower nitro contents and using a YS20/20 or 30% Heli would be stupid...................

snoopy5

Hi Speedster

Great news about the Sport 5. Sorry for not understanding the % misunderstood it. Great all you guys have taken the time to give me some info. Just one more thing does anyone know the SC web site address ? because I have lost the manual for the engine and I am going to try and get a replacement.

once again thanks to everyone

asmund

Just search for Magnum 70 fs, it is the same engine, just more commonly used name

NM2K

My Feedback: (14)

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Those lemon cranks held up good to 15% nitro usage for years without failure. After running a few tanks of 30% nitro, many of them broke.

Now it appears that the manufacturer has gotten smarter. Instead of improving the crankshaft and costing them (manufacturer) additional money, they have now reduced the carb throat size and may have reduced the compression ratio. This isn't even counting the possibility of reduced valve sizes and the possibility of mellower cam profiles.

If they feel that their niche is inexpensive sport engines, it is easier to accomodate the 30% nitro crowd with changes that cost them nothing or less when compared to hardening the crank sufficiently to withstand the higher nitro.

I'm just guessing, but it appears that in view of the recent production changes to their engines, they are headed in this direction. Change costs money. They certainly had a reason for detuning their already anemic engines.


Ed Cregger

P-40 DRIVER

Running 30% nitro in a sport engine is a waste of money. I talked to guy at the field who broke his crank on a Mag .91 using 30%,

NM2K

My Feedback: (14)

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I agree with you, but we have plenty of young'uns who think that they can hang with the gurus by burning 30% nitro in a cheap engine.


Ed Cregger

broke_n_bummin

I've seen some that say that the 30% helps the engine idle better. I've even tried it myself. The biggest problem I had was that at WOT I had to make it so rich that you could see oil spitting out of the muffler. If I leaned it out, I ran into predetonation problems. Of course, I could have used a cooler plug, but then I ran into idling problems. I actually went through more fuel running 30%. I'll leave the 30% for the Helis. I don't run anything more than 20% in a 4 stroke, and that's in something heavy like a war bird.

Sport_Pilot

Next time try a K&B 4C plug, it will allow you to lean it out a bit and gain some RPM. High nitro is not necessary for common sport flying. I have only done if for fun fly competition. It really makes a differance in the climb and glide.

speedster 1919

My Feedback: (3)

Snoopy My ASP had Magnum manual in the box when new. So go with the Mag 70 reprint.