Spark Ignition Nitro Engine

[SayMikey]

Lohring would you call that extreme detonation?

 

[Ian Inverarity]

I race in Australia and our rules for nitro dont even mention ignition so spark ignition is not prohibited.

It is interesting to see other people's experiences here, and indeed it appears the spark plugs themselves can be an issue running nitro. Considering how delicate a glow plug element is I find that curious.

From a safety point of view, the Power-spark system I would consider using for this sort of thing has a minimum speed of crank rotation before it starts to fire to prevent accidents from manually turning over a prop. And the system switches off completely when the radio is turned off.

 

[Andy Brown]

Good posts Lohring and Ian. That is good news about the power-spark system! I am sure with the correct engine set up, the spark plugs will hold up well with nitro....just a matter of the right set up.

Even that AAC and ABC P/L would work on the BIG gas engine. CMB just did'nt know how to set it up correctly! The success is in the details. Novarossi .46 was sticking pistons and had Glenn and Martin scratching their heads. Glenn sent me his .46 and I reground the piston and it never stuck again...and was very fast. Dale also just stuck a piston on his Novarossi .61. Just because an engine manufacture has some of the best 21 engines in the world, doesn't mean they can make them all work the same...Every size is different. I can run 70% nitro on a fine McCoy #59 wire without burning it out. It's all in the set up!

 

[lohring]

I agree that CMB doesn't know how to build an AAC piston and liner for gas engines. We also seized a ringed piston in a liner that had zero clearance just above the exhaust port. Rings are a lot more tolerant, but not that tolerant. I think dragsters on 100% nitro also melt their plugs and depend on preignition for running. Our engine kept running without the electrodes. It was hard on the piston when the electrode went out the exhaust port, though.

We also ran a modified Zenoah on nitro/gasoline with up to 15% nitro in 92 octane gasoline and methanol/gasoline mixes. It wasn't optimized for those fuels so we didn't see a power gain. The plug did fine. I'm sure plugs could be developed for higher nitro based fuels. The limitation in NAMBA is the requirement that only gasoline fueled engines can run spark ignition. With pump fuels for the "gasoline" classes becoming more exotic, I think it might be time for a change. Maybe going back to the IMPBA displacement only situation with open ignition systems would work. You could still have a separate “gasoline” set of classes with more restrictive rules. It would be fun to see how 20 to 29 cc “gasoline” engines would do against traditional IMPBA F or NAMBA X engines with open fuel rules.

Lohring Miller

 

[lohring]

Oops, I completely ignored the F hydro discussion. I guess that IMPBA requires glow ignition as well. I only know what the posted rule book says.

Lohring Miller

 

[Ian Inverarity]

Lohring, did you leave the pipe lengths and stinger sizes and compression ratios the same on the gas engines you tried with nitro and spark ignition?

 

[Ron Olson]

I just sat here reading the whole thing so far. Love this thread, hate it or anything in between it's just plain interesting as to where the boaters are loooking and trying if there's a class or not for them. I've sat in the background in awe of some of the best boaters around at the motel in Merrillville during the Indy Masters race in Hobart. Some people have said that nitro engine have hit their limits but not according to these guys as they found a place right in front of their faces to explore more.

Is the Tiger King all that yet? Well, that depends on who you talk to. The whispers are that they have bearing issues to contend with yet but just another little bug that almost any other new-to-market mill might have one of somewhere.

Would a gas to nitro conversion also mean that possibly a dished piston and a more concentrated cylinder head would be needed for a better combustion?

Again, just a guy sitting in the back mostly with my mouth shut but the ears (and eyes in this case) open.

 

[lohring]

We ran the pipes for gasoline on the test engines with the nitro fuels. That's another reason we didn't see any power gains. Everything needs to be set up for the fuels. Just changing fuel isn't a magic bullet. The results below show the opposite of what you would expect. Besides the wrong compression ratio, the pipe wasn't designed for the new exhaust temperature.

Lohring Miller

 

[dwilfong]

Lohring

Maybe adding nitro to the gas would have seen bigger gains as this would have bin closer to the pipe set up .

 

[BobBonahoom]

Here are pics of the spark set up I put together for a CMB 101. I never actually tried it, but I have alwasy wondered how it would compare to glow igniton using nitro/methanol fuel. This CDI ignition requires 4.8 volts to operate. You press a magnet into the flywheel and set the wheel magnet so that the system fires at TDC. Then you use the potentiometer on the circuit board to advance the timing. There are other CDI systems that work with a fixed advance and then retard timing electronically as a function of RPM (the lower the RPM the more they retard timing). It seems to me that one would need a dyno to figure out where to set the timing for a given fuel, pipe and engine set up. Has anyone tried one of these systems in a nitro racing engine?

Bob

 

[Andy Brown]

Cool stuff! In the old days of Top Fuel drag racing they ran about 70 degrees of advance with a single plug in the head. These days with dual plugs and other improvements they do not need so much advance.

For us it would mainly depend on how much nitro, compression and combustion shape. Just start with methanol and or 10% nitro and use the advance that works for gasoline. Then work in a little more advance as you learn. Boats make great dynos!

 

[dwilfong]

Bob can you give us a few details on this set up. plug # and make ign system what make. also any info on other ign systems out there.

Here are pics of the spark set up I put together for a CMB 101. I never actually tried it, but I have alwasy wondered how it would compare to glow igniton using nitro/methanol fuel. This CDI ignition requires 4.8 volts to operate. You press a magnet into the flywheel and set the wheel magnet so that the system fires at TDC. Then you use the potentiometer on the circuit board to advance the timing. There are other CDI systems that work with a fixed advance and then retard timing electronically as a function of RPM (the lower the RPM the more they retard timing). It seems to me that one would need a dyno to figure out where to set the timing for a given fuel, pipe and engine set up. Has anyone tried one of these systems in a nitro racing engine?

Bob

 

[Ron Olson]

I've got an electronic ignition system sitting in the shop right now that I haven't hooked up to anything yet. It uses the Hall sensor and has 30* of advance timing with a water-proof ignition box. You can also hook up a tach or battery voltage meter to it. It does need its own dedicated 4.8 V pack to power it.

 

[BobBonahoom]

This is a "ProSpark Electronic Advance Ignition". They were sold by Nelson Hobby Specialties, Keller Texas. Here is link that describes this system and a few others. http://www.rcfaq.com/ANSWERS/ENGINES/ignitions.htm#prospark

From what I can tell, Nelson Hobby has gone out of business. I bought this about 6 years ago and it has been gathering dust since then. I can't find any reference to the manufacturer on the web now.

The spark plug is an NGK ME-8 1/4-32 thread.

Here is an article on how glow plugs work for comparison. http://www.modelairplanenews.com/Media/MediaManager/GlowPlugsExposed.pdf

 

[Andy Brown]

Over 2000 views in one week! Must be a little interest in this subject?

 

[David Ashcroft]

www.power-spark.de they cater gas r c boats they look to be good quality. They are used a bit on jims site

David

 

[Jeff Lutz]

Over 2000 views in one week! Must be a little interest in this subject?

I know someone who wants to hunt bald eagles too, but its illegal….

 

[Don Ferrette]

Over 2000 views in one week! Must be a little interest in this subject?

Until you posted at 1am this thread sat idle for almost 5 days. Kinda like a car wreck, you don't want to be involved but you're gonna look when you see one.

 

[Ron Olson]

I sat here at first and read it "cover-to-cover" initially and then you figure how many members who are subscribed to this thread who only read the e-mail notifications you should be able to just about double that number.

I also read the whole "F" class thread, that was a lot of reading!

 

[dwilfong]

It is going to happen no mater if you like it or not.

Kinda like when you go to the big house.