mtntopgeo

My Feedback: (12)

I order this new toy, & 3 (maybe more) weeks later this great looking little engine shows up. On to the test stand. Starts easy, (didn't have any "no nitro" fuel, so used 10% with 25 % castor) and after a few 1oz runs on the rich side, started leaning it out. Pretty good power, & idle. After about a half dozen runs, I leaned it out to get a tach reading. 18,300 with a MAS 5.5x4, & 16,200 with a MAS 6x3. I only kept the max RPMs up long enough to get a tach reading. The test with the 5x4.5 went smooth. I changed props, turned on the glo power, & was unable to get output balanced so that both the "hot" & "cold" lamps were illuminated at the same time. Either one, or the other, not both. This never happened before. Engine started ok, but I couldn't get a steady RPM. I kept chasing it with the needle to try & steady it out at max RPMs. Shut the engine down, & checked fuel system . All looked ok. Tried a restart. No continuity thru the glow-plug. Removed the head, & checked the plug. The coil looked like someone (me?) had taken a small drift punch to it. (The coils were compressed towards the top of the plug.) What did I do wrong? 2nd question. Three weeks (+) is a long time to wait for a new plug from Carlson. Do I have any options? ........ George K.

ptulmer

My Feedback: (5)

Doesn't sound like you did anything wrong. Plugs go bad a lot when you're breaking an engine in. It's always best to order a couple extras at the same time as the engine. As far as a quick fix, you might try a Cox/Norvel/AP head. It seems to be a standard. I've never had an MP Jet, so I couldn't tell you for sure.

combatpigg

My Feedback: (3)

Sounds like it should be run on zero nitro? The compression / combustion forces will force the plug element back. Sometimes you can pluck it back out so the coils aren't short circuited. To allow using nitro you can try shimming the head. I wonder how this engine performs on zero nitro?

skaliwag

My Feedback: (1)

It will proberbly work fine on 80/20... It European. Nitro is exxeee there and FAI says no Nitro.

Tim Wiltse-RCU

He's not going to be able to make a Cox/Norvel or AP head work. The MP uses a real bolt on head just like a .40 sized engine but then uses an insert. It fits down into the cylinder.

LAter,
Tim

mtntopgeo

My Feedback: (12)

Thanks for the input guys. The instructions say that the engine is designed to run on 0% nitro, break it in on 0% nitro, but use 5 to 20 % nitro to "improve starting, running, & power output". I felt comfortable with the 10% stuff, 'cause a friend runs his (bb version) with 30% & no head shims. I'm running one shim, as supplied from the factory. Guess that I could add one or two more when I install the new plug. Next order of fuel, I'll include a gal of 80/20....... George K.

gcb

Tests for the MP Jet .061 glow in an old Carlson catalog showed tests at 5% and 25% nitro and the starting and most performance was excellent. Tests were made with no head shim and with one head shim. The head insert lasted the entire test. The tests were made after the engine had been run for an hour. Although they ran it up to 30K, the instructions (at that time) said to not run it over 20K.

My GUESS is that you just burned out the plug. I would suggest keeping some old inserts in case you have to thread them for regular plugs some day.

I do not have the glow but my diesel runs great.

George

mtntopgeo

My Feedback: (12)

Thanks for the info George, This re-enforces what my friend says about using the 30%nitro fuel, with no shim, & no damage. I've seen coils open, & I've seen them coated with a white substance after failure, but never compressed like this. I was at a loss! I have ordered extra inserts, & will save the old one(s). The Logan has it's next job waiting; if, & when, I ever get finished with this up-comong move. ..................... George K.

combatpigg

My Feedback: (3)

Good to hear that the MP JET is a runner. I've never seen one. Nice to have an ace in the hole if AP goes T.U.

I've squished a plug element after a hydraulic lock.

digital_trucker

I had an OS .50 that had a habit of compressing the plug element. It'd only do it during a full-out power dive with full up at the bottom. The plane would some of the tightest loops you ever did see, but it would often kill the engine - after landing I'd discover the element pushed all the way to the top. Oddly, needle settings wouldn't affect it, and it'd even scramble the flat-wound plugs (glow-bees?).

mtntopgeo

My Feedback: (12)

Hec, I thought that I had discovered something new! The education continues! .................... George K.

digital_trucker

I suspect that in my case (due to the extremely high g-forces in that maneuver), that it was doing two things to the engine at once; first, the RPM was wayyy up cuz of the power dive and then at the bottom the engine was forced into an extreme lean condition. Might have some bearing on what you experienced. Possible underpropping along with a little lean-ness on a not-completely-broken-in engine?

jetpack

My Feedback: (1)

It is always a good practice to heat temper the glow element before using a new plug. They are not really ready to use out of the box.

Ignite your glow plug bright red to orange for ten seconds and let it completely cool. Repeat this five times and it will be ready for a long life.

gcb

The coils of a glow plug only need to be separated while using the booster. After they are running on the catalytic reaction, it shouldn't matter. I have carefully separated the coils with a needle (at home). Be careful, they can be a bit brittle.

I have never heard of heat treating glow plugs. Have to give it a try.

George

jetpack

My Feedback: (1)

Yep, it strengthens the metal before it gets pounded by compression. They can heat treat on thier own with each flight, but this gives it a jump on them first few uses - that means it adds to the last few uses on it's lifespan.

Either way they get heat tempered. Next time check out the springyness of the element on a new plug, and the brittleness on a used one (if you dare). There's a big difference!!! It pays to get them strong before they get used.

P.S. Don't tell this to the glow plug manufacturer's...they will feel compelled to put it on thier packages....

mtntopgeo

My Feedback: (12)

George, the separating with a needle" procedure wouldn't have worked on this plug. In addition to being compressed, the element was open. I have never heard of the heat treating of the elements either, but when my replacement plugs arrive, I'll have to give Jetpack's thing a try. ................. George K.

combatpigg

My Feedback: (3)

Anything that can prevent finding chunks of element scattered and wedged between engine parts is OK with me.

Cobra289

Nitro Cars and trucks will do that same thing with a violent crash. Infact i recently killed a TRX 3.3 because a plug decided to decentagrate[&o]. That was one fine running mill too. I think its just from the erratic g-forces we put on the vehicles caus the plugs to do that sort of thing.