ijpom

Hi all,

Since I'm the newb here, I'm in no position to choose between ways to tune an engine. Just hope to get some advice on what happened, and what is a good way to get things right (idle, power and durability)

Thanks to Neal for his through response. I was hoping this was copied from something previously written, but it appears he was live, and put a deal of effort into the response. Since this all makes great sense (getting your throttle linkages correctly set, and then perform HSN tuning, then adjust LSN, then refine), it does not conflict with anything else I'm being told.
Here is an analogy: I assume you can use multiple paths to get to the summit of Everest; different paths suit different climbers.

Where things differ slightly is the 0.5mm throttle opening. Manufacturers and everyone else I've read says 1mm. I still have the carb from the destroyed engine and will make a measurement the best I can. This will tell me where I was. I also have yet to look at the glow plug from that dead engine. The element will be grayed, have a little distortion, but the plug always tended to have a bunch of 'wet' (oil?) around base. Pictures will explain better.

While running the EX28 I find like Neal says, that it starts/idles/runs horrible for the best part of a tank, even though it ran great when it was last turned off. I'll pull this plug too, picture it, and see if anything can be diagnosed to prevent another "what happen to my engine" post.

1QwkSport2.5r

All glow engines run like poo when they're dead cold. That's normal - they need to warm up because at cooler temperatures, the fuel will condense and stick to the metal surfaces. Once the engine warms up, the fuel atomizes better which is true for all engines, model or automotive alike. Also, if the last time you ran the engine the ambient air temp was very warm and the next time is cooler, the engine will start out lean. Same with if you ran it in cold weather and later warm weather; it'll be rich. All glow engines will start cold being rich unless the idle needle is way lean. As the engine warms and the ignition advances, you'll notice how the tone of the engine changes. Listen and learn those different sounds. If you want, you can get in the habit of always richening your main needle (high speed) half a turn before you even start it up for the first time since your last outing so you know you're always starting rich. For someone that doesn't have the ear for it yet, this might be a good idea. You could set the idle a 1/4 turn richer as well. It's always better to start out rich and work your way leaner. Always set the high speed first as Anthoop mentioned, then set the idle mixture and idle speed.

I've been running nitro for the better part of 18 years and it took a long time for me to "get it". Oddly enough, it took getting used to running airplane engines to be able to better hear how an engine sounds rich/lean and be able to tune for it. Being in a stationary position puts you right close to the engine so I found it much easier to hear those "tells" that the engine makes when it isn't happy. Ground based engines like RC car engines are not any different in how they operate than an airplane engine. The only differences are how the engine is loaded and fuel used.

supertib

Thanks buddy, I appreciate the kind words !

Many ways to skin a cat.... but when you start playing with Lion's and Tigers the game changes a whole bunch and many of the old school idea's just don't work any longer.....what works for Lion's and Tigers works dam well for cats...but some of the things that work with a cat will get you clawed to death if you try them on a Lion or Tiger !

I have to admit I am arrogant when it comes to nitro engines ( depends how you define arrogance ) ...I am possibly the nicest guy you could ever meet and I will do anything to help anyone anytime, I will give the shirt off my back for almost anyone and have done so many times over.. I am kindhearted , honest and a all around good guy, but when it comes to these specific engines I do believe I am the best of the best and that confidence in myself comes across as arrogance at times, especially to those on the other side of a argument ... But unlike many I don't use my knowledge with the intent to belittle anyone or put myself above anyone, I don't do it to stroke my own ego on the forums as I suspect many others do.... I have a wall full of trophy pics and race wins to do that, I don't have anything to prove.. I Am just passionate about the nitro hobby and want to do my best to protect it, over the years I have seen hundreds if not thousands of hobbyist abandon the hobby due to trouble managing a nitro engine and it kills me ... I have gone from being that guy who was lucky to get his engine running to the guy who's coaching Pro level winning race teams how to tune... So coming from my current understanding I see many holes and fallacies in the common information that is passed around these forums and I also believe that much of this information is wrong and responsible for a great number of hobbyists leaving the hobby....Honestly 99 % of the online tuning guides are garbage, 90% of the fuel information is wrong... almost none of the guys writing tuning guides and advice have any real competition experience... And you may say that doesn't matter and competition doesn't mean anything, but it does, and until someone goes thru the levels of racing they will never understand how much more involved and technical it becomes and also how much more challenging it is... Like playing pool in your basement by yourself , you can only get so good if all you have to reference against is yourself, whereas someone who plays in tournaments and ends up climbing the ranks and placing at multiple pro level events...where they are competing head to head against hundreds of different opponents... there is going to be a vast skill and experience difference....... Honestly racing is so challenging that often times I can teach a compete newbie how to tune much better then a basher with years of experience..as the basher usually thinks he already knows everything and will want to argue over every little detail .... where the novice usually sits back and absorbs the information then runs with it..... I have dozens of trophy pics on my wall from my customers who started from square one with me, compete novices one year, winning A-Mains and being the top dog the next...... Anyways long and short is my methods work extremely well, they are very efficient and will have someone up and running safely in no time at all.... I have professionally and successfully coached thousands on how to tune their engines, I do definitely have a different take to how to tune but after all these years doing what I do its only understandable that I see things differently then most and would be a trailblazer instead of a follower.........

supertib

A group of scientists placed five monkeys in a cage, and in the middle, a ladder with bananas on top.

Every time a monkey went up the ladder, the scientists soaked the rest of the monkeys with cold water.
After a while, every time a monkey would start up the ladder, the others would pull it down and beat it up.
After a time, no monkey would dare try climbing the ladder, no matter how great the temptation.
The scientists then decided to replace one of the monkeys. The first thing this new monkey did was start to climb the ladder. Immediately, the others pulled him down and beat him up.
After several beatings, the new monkey learned never to go up the ladder, even though there was no evident reason not to, aside from the beatings.
The second monkey was substituted and the same occurred. The first monkey participated in the beating of the second monkey. A third monkey was changed and the same was repeated. The fourth monkey was changed, resulting in the same, before the fifth was finally replaced as well.
What was left was a group of five monkeys that – without ever having received a cold shower – continued to beat up any monkey who attempted to climb the ladder.
If it was possible to ask the monkeys why they beat up on all those who attempted to climb the ladder, their most likely answer would be “I don’t know. It’s just how things are done around here.”

ijpom

These are from the blown and dis-assembled SH28 engine.
The actual Glow Plug (looks to have been cleaned of oil) and carb final settings.
Idle gap as best measured is between 1.0 to 1.2mm. The plug is grayed, mildly distorted and had at least a quart or two on it.






On closer inspection the carb throat appears not completely clean. I'll check the part, and maybe find an answer there.

ijpom

These are from the working EX28.
Carb gap slightly smaller (est 1mm), and plug is shiny, undistorted and has 5 tanks on it. Looks better to me.
Note from truggy surrounds that the track is plain dirt and gets everywhere.

supertib

There was your phantom air leak right there.... big idle gap and the engine wont tune.....pretty much no matter what no engine is going to tune with that large of a idle gap, its pretty much a endless game of chasing needles........ thousands and thousands of guys have slathered their engines in silicone trying to seal that exact airleak...... these horrendously bad tuning guides are responsible for causing this to happen to almost everyone who starts out in nitro.... Anyway please read my tuning guide, its much better and far more accurate to how these engines run....

ijpom

Thanks Neal. You have a very professional bunch of links. Store and YouTube demo video. That car runs great, and whoever is driving it is awesome too. Gives great a great example of the tone, rev down and smoke of a high performing engine.
I have my replacement EX28 to match my existing unit, and plan on starting the tune process with a much small idle gap (5mm as you recommend).
What I have also learnt from my extended conversations is that my use patern had been contrary to good tuning. One tank at a time never got it to a stable operating temp.
Thanks to Tim and Anthony too for their help.

Anthoop

No problem.

Did you get a chance to measure that bore size on the EX.28....wondering if it is 18.5mm?

ijpom

Anthony,
Just this morning I pulled the head off the new EX28 and put my vernier caliper in the bore. To the best of my measurement, and without scratching up the liner, I measured the bore at 18.4 to 18.5 mm. This is from factory with zero fuel through it, so a little underspec/pinched is probably expected. It looked real clean in there, with a light oil coverage and no visible manufacturing debris.
I think this confirms our suspicion that this is a bore/stoke clone of the SH28.

Anthoop

Yes...trouble is that it also creates more questions (in my mind anyway).
Thanks for doing the measuring.