GSJames

Quote from previous post:

"Oh BTW, I bought some Merlin 2016 "GloBee Style" plugs based on an article in the recent NMPRA newsletter. That article indicated that the 2016 gave superior performance in the TT 40Pro for 424 so I decided to try them in the OS 25FX. With the shim installed and 15% nitro, my engine won't even stay "lit" after removing the battery. With the shim removed, it will run pretty fast, but the speed drops off after removing the battery and although I haven't tried it yet, I can't imagine that it will idle without dieing. The 2016 plug is just too cold for this application "as is" I'm talking with Merlin Glow Plugs about a solution. " END QUOTE

To add more to this, I got a call from "Al" himself! (I hope I got that right), the owner of Merlin GlowPlugs and he gave me a suggestion on a possible fix to make the 2016 plug work better in a low compression engine like the OS 25FX (for Q-25). I will try his suggestion as soon as I can (within the next couple of days) and report back.

BarryReade

My Feedback: (1)

Gee, it would be great if you shared his suggestion.

[email protected]

I read with interest the first message, but I have to advise that using the 2016 plugs in a THUNDER TIGER 46 engine with 10% nitro the engine has never run better..........yes to the extent I sold my first supply to my fellow pylon people and had to get a further supply. Can only praise the performance. Al has been around along time and I believe he is doing a good product. Your motor is running undercompressed if when you take the leads off it drops rpm. They are a good product but as the previous participant said- what did Al tell you to do to solve your problem- it wasn't pulling the element was it? regards trevor henderson[sm=bananahead.gif]nz

Scorpion Racing

I think the glowBee plugs will work fine for 424, where you are setting up for full throttle only and are not trying to idle the engine. I can see an issue with trying to idle with a cold plug, which would let the engine cool too much and quit. My 424 engines all quit if you go below 1/2 throttle, but since we start wide open and only kill the engine to land, is isn't really an issue for racing.

The colder plugs will allow you to pull more RPM at the top end, but if you want to run the engine as a sport type engine and idle it, I would think the OS #8 or A3 would be a better choice for that. I have noticed every plug type I test will take a little different set up to get the most from it. Some work better in different temperatures, humidity levels, fuel types, head heights, etc. Make sure you are using a bladder tank (Jett or Tetra) to get a consistent fuel flow will also help you to get a good set up. I am sure the man who builds the plug can give you the best information on how to make it perform, since he did all that testing already.

Let us know what happens Gary, I am interested in what you fine out.

daven

My Feedback: (1)

Gary,

That is the nature of a cold plug. You gain on the top end, but suffer on the idle.

Many racers will unscrew the idle needle to the point of falling out, and then glue it in place with JB weld, or others glue so it doesn't. Check the rules, its in there.

Its a trade-off, do you want to have a nice idling plane, or possibly gain a little more on the top end.

Pick your poison, I'll use the coldest plug I can find and learn how to deadstick one of these days.

Conrod

Trevor
Where are you getting your Merlin plugs from?
Geoff

[email protected]

Geoff, I get mine direct from Al Kelly, Trevor H

GSJames

I plan to, but I figure I'd better see if it works first. I think I can get some time to test today.

GSJames

Different Day, Different Result...

I ran the same Q-25 engine on the test bench yesterday afternoon with the same 2016 plug, same prop, same fuel, OAT 102 deg, which is hotter than earlier. The engine ran flawlessly. No problems whatsoever. It ran the same speed whether the glowplug battery was connected or not. It idled down just fine and gave great top end, the best I've ever seen on one of these engines (OS 25FX). Hmmmmmm.

I then changed out the plug to a modified 2016 as suggested by Al Kelly to address my earlier problem. As mentioned, the modification is to lift the middle spiral coil slightly off of the ceramic insulator using a bent pin. I had a 200-300 rpm drop off in top end from the un-modified plug, same as that experienced on the TT-40Pro mentioned in the NMPRA newsletter.

It could be an effect of the different outside air temperature, or it could be just bad data on my part. In any case, I'll go back to the unmodified plug and keep an eye on it and see if my results continue to be the same. Merlin makes GREAT plugs and I heartily recommend them to anyone. Al's customer service is second to none.

P. Johnson

My Feedback: (1)

I have a relative question and Gosh I hope this doesn't sound too negative or be taken wrong. BUT.. I keep reading how a plug will give 300 more rpm, or changing a head shim will help out in another area.
If the whole idea of Q25 or 424 racing is to bring new blood into the sport (hobby) , why are you messing with getting that extra little bit out of the engine?
If a new racer comes out and looses ( and he will because of lack of experience ), and then over hears the more experienced pilot talking about head shimming and special plugs, isn't he going to feel like he is already loosing in an event that is supposed to be STOCK!
Sorry if I have offended anyone , but if 300rpm is going to make or break your day,,maybe spending a few more dollars on another gallon of fuel and practicing would be better spent.
I run my engines just as they came out of the box , STOCK. I don't remove or add head shims and use a KB1L. I don't use a tach !
I have NO idea of what kind of RPM my TT40 will turn, and it doesnt matter. It is STOCK ! If I loose a heat, I want to know it was because I was outflown or I had stupid thumbs, Not because my plug wasn't as good or my head shimming was off.
C'mon guys..keep it simple .

.

GSJames

You will notice that I am SHARING the information freely, NOT hording it to myself. The same can be said of NATS winner David Norman and MANY others. The NMPRA newsletter is FULL of information to improve the speed and reliability of your models.

Seeking ever-increasing performance in our models AND OURSELVES is fundamental to racing at EVERY level. If it were not an inherent part of the competitive personality that gravitates to racing, then those pilots would be flying pattern or something equally boring.

I AM running a STOCK engine, and will continue to do so. To do otherwise in a stock class would be cheating and I DON'T CHEAT even though I know just about every trick in the book after 45 years of modeling experience. Experimenting with plugs is not "modifying" even under the strictest interpretation of the rules. And by the way, the KB1L is the second fastest plug that I tried. I don't think that a KB1L came 'STOCK" with your TT40Pro. Are you "modifying" your engine by using a plug other than the one that came with it??? Adding and removing head shims is specifically allowed in all classes that I am familiar with. I am also SHARING that information as well, both with this forum and with all of my club members.

As far as "STOCK" goes, I hope that the FIRST thing that you did with your TT40Pro was to take it apart and clean it in lacquer thinner. MY TT 40Pro was FULL of metal chips and junk. It also had not been correctly machined and the main port was 70% blocked off with metal flashing that had not been milled out. Did I 'MODIFY' the engine by removing the chips and opening the main port to where it was supposed to be if the quality control had been any good ??? I don't think so.

300 rpm... Let's say for argument that the race takes 1.5 minutes. That's 450 revolutions of the prop. With a 6" pitch and an 80% effective pitch (i.e. a 20% slippage) that works out to 180 feet.. I would say that is significant.

Based on experience, the ONLY effective way to limit performance is to DIRECTLY LIMIT the performance like we do in SSC combat, Limited B and 2548. That is by specifying a specific prop and a max rpm limit. Some 424 races do this already, and in Q-25 in our area we specify an engine, the OS 25FX, a max nitro limit and your choice of 2 different props.

Having the best performing, and most reliable equipment WITHIN the limitations of the rules is the fundamental essence of racing, to do otherwise is just sport flying. I understand the point that you are making, I just completely disagree with it. BTW, I AM that new blood you are talking about, I've flown exactly TWO RC Pylon races so far in my life. It's FUN, almost as much fun as Combat! and I'll be flying LOTS more races in the future.

daven

My Feedback: (1)

All areas have different tweaks to the rules for their "beginner" classes.

Look at the rules, and stay withing the limits of the intent of the rules of your area and you will be fine.

Shims are gaskets, and in most rules are legal to modify, so are glow plugs. Nothing stated by Gary is moving outside the rules that I can see.

300 rpm may seem minor, but can account for 1/3 a lap if all other things are considered equal. Rarely do I consider ground rpm important, look at lap times (with people making sure you make it to pylon 1) and determine if you are unloading properly.

There is so much more involved in going fast than RPM on the ground, or compression when the motor is cold.

HighPlains

My Feedback: (1)

I'm afraid that your understanding of prop efficiency is incorrect. Prop efficiency is a measurement of power transfer and is generally in the range of 80 to 85%. Knowing the amount of power available allows one to figure out the speed possible with a different engine, since the speed is proportional to the third power. In other words, it takes 8 times the power to double the speed.

However what you want to quantify is the slipage of the prop, which depends on a lot of factors, but is usually in the 10 to 15% range when the prop diameter and pitch are well matched to the engine and airframe. This means that the prop slip stream past the fuselage is about 10-15% faster than the airplanes speed in unaccellerated flight. Oddly enough, the slipage amount is pretty close to the amount of unload that most engines see on clean airplanes.

BobHH

My Feedback: (18)

Well guys, I put a 2016 into my stock TT40 today at the race. I was running an OS8. Same fuel same temp, etc. Gained 375 RPM without even touching the needle. The engines does tend to load up a bit more at lower throttle just make sure you clear its throat. Strangely I can't see how this improvement works unless the burn is more evenly spread with the glowbee type plug. Any comments?

Bob Harris

BarryReade

My Feedback: (1)

Why didn't you tell me at the race and offer me one???

GSJames

Only that years ago when GloBee was in business, their spiral-wound plugs were quickly adopted by virtually all CL racers. I suspect that it was used by many RC Formula One guys too. In the CL Rat Racing world, the spiral-wound plug gave superior performance, not only in top end, but also fewer blown plugs as the design is more resistant to damage since it is 100% supported by the ceramic insulator rather than being a helix suspended in a tubular cavity. As for why, I'd like to know that myself, but the basic physics of combustion means that either a higher cylinder pressure is being generated due to more efficient/complete burning of the fuel or that the pressure is being generated at a more efficient time in the stroke. It's P.F.M. to me but I'm gonna use them.

Oh BTW Bob, I'm in the process of painting my Buckshot wing. So far, so good.

twitte1

I have seen the same results as Bob H. The firsty readings I got were 400-500 RPM more without touching the needle. Depending on the outside conditions I have seen every more gain. This is on a TT Pro 40.

The 25FX saw a little less gain. The idle was affected some, but not much.

Trey

BobHH

My Feedback: (18)

Gary, here is a shot of some BuckShots at this weekend race. Now some pictures of your!!!

Bob Harris

Phil Heller

My Feedback: (9)

Hi,

Where are you buying Merlin Plugs?

Phil

GSJames

http://www.merlinglowplugs.biz/

Phil Heller

My Feedback: (9)

Thanks Gary,

I already ordered several!!!

Phil

jaka

Hi!
It's easy!
You use a colder plug than the OS 8, then the the timing is retarded (the fuel/air mixture is ignited earlier) and that way you get more power.
The problem is finding that "timing" to get more power as there is so many factors involved, props size , head shim, fuel, glow-plug...etc.

[email protected]

a very true comment.............regards trevor h[sm=thumbs_up.gif]nz

Conrod

Doesn’t retarded timing mean latter ignition. Geoff

mdwpylonracer42h

To Jaka,

You may be partially right, but when using a hotter plug the ignition timing is advanced, meaning the plug will ignite the air fuel mixture much before top dead center. A colder plug will retrard the timing more, meaning the fuel air mixture will ignite after a hotter plug would - - the piston would get closer to top dead center on a colder plug before ignition before a hotter plug will. In essense, a cold plug is retarding the timing of that of a hotter plug. Being these are glow plugs on a 2 stroke 1 cylinder engines, I can't imagine that the plugs would ignite after top dead center, which is very possible on a multi piston 4 stroke engine.

Therefore, an OS#8 is a relatively hotter plug than the Merlin 2016. The OS plug will ignite the air fuel mixture ealier in the pistons upstroke than the Merlin 2016. The OS 8 advances timing - - the Merlin 2016 retards it.

I understand that a colder plug works better on WOT on a 2 stroke engine where the compression is increased, but it does not do well for idle, mid range, etc. Of course when we are racing Quickie, WOT is all we are concerned about, because we mostly land dead stick and an engine that will idle is not necessary.