Marciatelli

Hi there,

I am an intermediate/advanced nitro car enthusiast and usually I have no problems with my cars. I know how to tune 2stroke glow engines, what porting is and all this kind of crap. Lately I've picked up my older kit that I didnt use for some time and cleaned/lubed/re-oiled it just so I can use it again.
Ive dissassembled all of the car (including the engine) so I can lube and check all the parts. I have changed the outside bearing of the glow engine and its cylinder head. The chassis itself is a Tamiya Nitrage 5.2 and the engine is a Tamiya FR-32 FX / OFNA Force 32. The car weights around 4.5 kg with the engine fitted in but without fuel.
The chassis has no binding, performs superbly smooth and everything is in tip top shape.
The engine before running has been assembled with new parts, gasket silicone has been applied to all the needed areas, green slime has been applied to carb needle threads to prevent leaking. No leaks in the engine or the fuel tank. It has been checked 100%. The compression is good too.

My problem is that after the engine has been assembled, it has been acting like a a**hole and doesnt want to be tuned for shiz. I have driven with this engine before and tuning was not an issue back in the day.
I have had few glow engines in the cars, I know how they perform, how they sound, how they feel when they are healthy.
I am running HPI Racing Optimix/Optifuel 25% with HPI R5 Cold glow plug.

Yesterday I spend about an hour trying to tune this engine, but ended up chasing my own tail.
I was messing with the needles and ended up what sounds like a too wide idle gap. The low end was super rich and top end was lean. The engine didnt keep the tune, below 1/2 tank it would lean out and the temps would go more than 300 Fahrenheit. At half throttle it would run super rich and then at full throttle it still would run rich but over heat (lots of blue smoke). I understand that its obviously my error in tuning and its fine. Weirdly I didnt realise that earlier.

Today I tried to stop being silly as twichy and slowly tried to correctly tune the engine. I have measured the idle gap of the "too wide idle gap" setup and it was 1mm. I found that really weird.
I have set the idle gap at .7mm using a milimetre gauge to measure it. The engine wont even start when I go anywhere below .7mm no matter the low speed needle setup.
I have set all the needles to factory settings aka the break-in settings in order to reset all the crap i have made and to have a fresh start.
I was going to keep the idle gap constant as I tune (as I usually do) and then set the low speed needle so I have a constant idle, then tweak it for a clean take off. After that, I would go with the rich high speed needle and tweak it to its optimal point where it has smoke and runs clean. Its a standard tuning method, nothing super fancy.

So I have set the .7mm gap, adjusted the low speed needle for idle and take off. The engine is warm of course as I tune.
The engine had problems with non constant idle (fast rpm and then slowing down to bog down stop), thats a sign of being rich. I have turned 1/12 turn clockwise to lean out. The engine now wont start at all. Any leaner than that will not allow the engine to start... Just like starving it out... with such small adjustment. Any richer will flood the engine.
I have turned anticlockwise 1/12 of a turn to rich out and allow the engine to run.

When in air (no load), the acceleration is clean and nice, blue smoke, no bogging or anything. As soon as I put it on the ground and add little throttle, lots of blue smoke and stall due to rich conditions.
The lsn is suuuuuuper rich, even while being super rich, at idle I get temps like 260 fahrenheit... what the hell? 260 at idle... 260!!! COLD GLOW PLUG AND 260?!? And thats with a hsn set for factory break-in (rich). The ambient temperature is 62.6 fahrenheit and I am pretty much on the sea level.

Honestly I have never seen anything like this, at the moment I am at the border of raging and I do not know what the f*ck is going on. If anyone who has more experience and know whats wrong, please help me.

The car is 4500g with a .32 engine (engine itself is 380g, I measured). Losi 8ight-T is 4080g with .28 engine. The chassis has no biding or resistance, its just a 1gen truggy from 2007, the engine should make it fly (like it used to).

collector1231

My Feedback: (1)

I'm gonna say, bad piston/sleeve? My TRX 2.5 won't tune worth crap, gets really hot and shuts down, and also has tons of blue smoke, no matter the tune. And that was the problem with mine.

Either that, or you should try another type of fuel. Mine worked okay (while I had some) Byron Gen2 20%, but the VP Basher 20% causes so many problems.

Or a bad carb. It happens. Thats what happened to my TRX 2.5, too.

Marciatelli

Thanks for info man!
Ive checked the pison, sleeve and all the parts when I dissasembled. Piston and sleeve are nice and tight. Good compression without actual grind that would mess with the engine performance. Needles are in great form too, untouched.
The engine shows signs of wear but no damage or what-so-ever, its been looked after.

Ive thought about fuel and checked yesterday with my Hyper ST, runs just fine... Normal temps and everything.

Am I being really silly with the tuning or did the engine just suddently become a bad apple?
With the cost of con-rod, pison and sleeve I might as well buy a new engine

collector1231

My Feedback: (1)

Humm, sounds odd. And no problem! You might want to PM a guy by the name of Maj_Overdrive, as he is one of the forum gurus.

nitroexpress

Get it pinched from a reputable source. Much cheaper.

Marciatelli

I think I will do, he seems to be a very competent guy! Hope he comments

Marciatelli

Youre right, gotta ask my local hobby shop expert as he can actually text and diagnose the engine on the go.

rcguy1411

Problem is this nice tight pinch on workbench but as soon as everything gets warm it expands and there goes the pinch time for a new p/s or new engine as you have stated bearings and gaskets have all been changed

Maj_Overdrive

My Feedback: (11)

Thats flattering, thanks Collector. But I don't know about guru, I just have too much info rattling around in my head. I've also ran lots of nitro but it's been a few years and I'm better at diagnosing electric.

Marciatelli, I read your post a couple times and can't find any obvious flaw in your tuning methods. Although personally, when you first had too much air gap I would've tried slowly leaning and closing the idle instead of setting the idle gap and resetting the needles. The temps throughout the whole process after the rebuild and the sensitivity of the LSN are baffling though.

While I won't rule out the piston and sleeve fit I'm thinking that's not the issue and instead think it might be an assembly error. The first one I'd check is the orientation of the piston. If it's backwards the ports won't be open/closed when they're supposed to be. Putting the piston in 180 degrees off would've been especially easy to do if you took the piston off the rod. If the piston and rod were both installed backwards the rod may be ruined as there's a chamfer on the crank pin that matches only one side of the rod. Another possible but less likely to cause these problems assembly error is the wrong head or shims altering compression. That's all I can think of right now.

Marciatelli

Thank you very much for the replies guys and sorry for not replying the same day.

Basically I spent past two days in disassembling the engine, checking every single part and then reassembling.

The crank case had difficulties getting out and I had to tap the other end slightly, I got it out.
What I have found yesterday is that there was a small rub between the crank case and the crank itself somehow? There were tiny marks all over small area of the crank. I thought it had to do with me replacing the bearing and inserting it not fully (bake method, small amount of time before binding).
I didnt think much and baked the crank case again, pushing the bearing all the way in (using the crank shaft so I dont damage anything).
After that I cleaned all the parts and assembled/sealed everything. No binding or anything, super smooth rotating.

I fired the engine up today, started tuning again and amazingly I got 200 idle and 250 degree full throttle readings after full speed run. The engine was not tuned to the optimum but holy crap that was amazing, rich and nice. That made such a great difference!

So the rub was the major reason for high temperature readings and being a b*tch to tune, I guess as it was binding it put stress on the engine more.



I had another major problem, my low speed needle. Leaning would cause some crappy acceleration and erratic idle.

No matter the setup at throttle applied it stalled, with thick smoke and excess fuel.
Rich? Dead.
Normal? Dead.
Lean? Its moving!... Dead.
And blue smoke all the time.

This was absolutely ridiculous and it didnt allow me to tune anything, hell, not even driving more than a feet.
Well, the reason for that was... slipper clutch.
I had to tear down the whole center diff (it comes in sections) and got to the clutch. The slipper clutch shoes were pretty much fused onto the slipper plate. After I got it out, it took reasonable amount of force to get that thing separated. I dont know whether its because its new, or soft shoes, or the force that was pressing on (my slipper is set fairly loose).

After I got these things done, the car is a fly, it tunes like it used to, drives amazing.

Thank you guys again for your help!

And for everybody who has problems with tuning their engine, remember, always check your clutch!!!
It plays a major role in running, and can get you thrown off the scale!

Mark

Marciatelli

I guess thats why it looked like it had a mind of its own.
You would think that leaning the low end would give better acceleration? It would make the engine choke on fuel.
You would rich out the high speed to get a cooler engine? 300 degrees and rising.

With nitro engines everything counts, not only the engine itself but also the surroundings, fuel, chassis, everything.
You think its the tuning, but its the rubbing of parts and slipper clutch.
Thats why its more complicated, more problems and more maintenance, but the feeling of reward in solving the problem is absolutely worth it.

Maj_Overdrive

My Feedback: (11)

Sorry you had to go through all that to find out it was a small assembly error. Why is it always the stupidest and smallest things that cause the most grief?

I'm really surprised the slipper clutch had that much effect though. Usually a slipper clutch only works when there's a shockload on the drivetrain so it wouldn't effect normal drivability since it's not slipping all the time. I would've thought Tamiya just added a slipper to a 1/8 truggy and let the main clutch deal with the performance side like any other 1/8 truggy. I guess they did something different though and the slipper is always slipping effecting performance all the time. It's bad enough adjusting a slipper to protect the drivetrain, but having to adjust it and another clutch for performance sounds like more work than necessary.

Marciatelli

Maybe Im wrong but as soon as I loosen up the slipper (not fully, relatively speaking), the engine stops choking and starts houling like its supposed to be.
It works like a cushion for the engine to rev up I guess?, so at the low 10kpm when you have the least power, the slipper doesnt overload the engine?
At the end of the day its a first generations of truggy (the truggy with more of a monster truck look and function), and I have to say that the chassis its pretty heavy by itself.
On the other hand I would expect a .32 with 25% nitro to destroy tires and everything on its way.
Would that suggest that there is a problem in the main clutch? as the spring being too soft?
Maybe Im missing another point? I have no idea...
So far its working really good and I will see what problems will arise!

Edit: Im sure youre right about the slipper protecting the drive train from overstress and shocks but I've also seen dudes on youtube talk about "How important is to set up your slipper clutch" and how you have to have about 2 feet of slide (in the clutch) before the clutch disengages. Such thing would not only reduce stress on the engine but also give optimal traction at start (depending on surface).

I might make some stuff up (I've seen that video looooooong ago), but if I find it, I will surely post it.

Maj_Overdrive

My Feedback: (11)

Like I said, normally the main clutch is used for performance tuning. It's controls engagement for taking off from a stop and other low engine speeds. For a slipper clutch to effect taking off from a stop it would have to slip from a stop. In every other nitro vehicle equipped with a slipper clutch having the slipper slip from a stop is bad. It results in too much heat in the slipper and the engine can usually overpower the slipper once it gets into the powerband. Maybe Tamiya did something different and it's supposed to slip but I doubt it. And you've already melted one slipper. My $ is on your main clutch engaging too early and a loose slipper masks the problem at low speeds. Once the truggy gets moving is the engine revving too high for the speed it's going? If I is then you're slipper is definitely too loose and you need to look into the main clutch engaging too early.

It is important to have a properly set slipper. In nitro it's usually to protect the transmission and differential. I do not know of a vehicle that uses a slipper for performance tuning or to prevent wheel spin. Maybe nitro 2wd stadium truck? When slipper clutches first appeared on electric vehicles they did double duty to protect the drivetrain and also to help prevent wheel spin. Slippers are still used to prevent wheel spin (especially in 2wd classes) but all the tuning options of today's brushless esc's have changed that a bit.

Marciatelli

Yes, I know how clutches work. Cheers for the advice it is very sound, I will look into the main clutch assembly. Might even upgrade the flywheel and shoe system from two shoe to three (its really old, like 2007).
Personally I did not notice a performance loss or slippage at higher speed. The engine revs up, truck goes faster. Relatively it travels at the same speed too.
Laws of physics of course say that it would slip more as more power is delivered to the spur gear (optimum of 3 hp).


I never melted a slipper... I replaced the old slipper shoes and slipper plate. I did that because the old set was used up.
New set was never used, as soon as I put it on the truck, it stuck or seized together (reason is quote up there).
The slipper plate has no signs of being rubbed (scratches), so I dont think excessive heat from friction caused that.

supertib

HPI fuel is absolute junk ...and will likely cause you all sorts of tuning and running issues..

Maj_Overdrive

My Feedback: (11)

Sorry, I thought the slipper was melted and that's why it was stuck together. My mistake. FYI, I tend to explain everything so there's no confusion, it's not meant to imply you don't know something. I just rather make one long ass post instead of a half ass post that requires 2 more to clarify something! And it's very possible Tamiya did something different and the slipper is meant to slip from a stop, but that's not really the norm for nitro vehicles. I'm pretty curious now and am going to have to lookup your truck when I get home. Definitely keep us updated.

Marciatelli

Its not the worst out there but not the best either.
Surely I wont buy more of it.
There is definetly a difference once you switch back to Byron Race Gen2 25% in performance, oils and even in the smell!

What fuel would you recommend?

Marciatelli

Dont worry, no need for apologies, its alright!


Once again you were right when it comes to clutches, slipper should protect the gears from overstressing (jumps and that kind of crap) and standard engine clutch when it comes to coupling.
It doesnt take much brain (which looks like I dont have haha) to figure out that making the slipper slip from low rpm torque is definetly bad and that it will cause all kinds of friction heat. It would as you said mask up the real issue.

Went for another run ( not a long one, around ten minutes) just to warm up the engine and just watch in detail how the car behaves. The tuning was fine, as I am bashing, a little bit to the rich side. Idle is low and stable, nothing fancy but as soon as I pick it up off the ground, the wheels start to spin pretty fast (you can easly stop it tho). To me it looks like the clutch spring has just loosen up, and it engages as soon as it can (the clutch springs is a round spring, came with the set, its about 3 gallons old - been sitting about 4 years in the clutch).

I looked into the engine clutch and shoes are pretty worn out and all that jazz.

Honestly 2 shoe clutch is hella old and outdated and I got nothing to lose so I ordered:
- Answer RC 34mm aluminum 'vented" 3 pin flywheel (an upgrade for the old heavy steel one) - I will be able now to fit now 3 shoe clutch. Everything is compatible with the engine and clutch bell. Light aluminum flywheel should allow for faster and easier increase in rpm but slightly less stable idle from what I understand.
- Answer RC 3 shoe clutch compatible flywheel nut
- Generic cheap 3 shoes with springs (not sure what thickness springs as 0.9 or 1.0mm, will measure when they come)


As soon as the parts come (around 27th August) I will install and run them, will see how the performance changes, if it changes at all (it should).
As the slipper shoes are still pretty much new, I will reset it to factory settings (as in the manual).
I am out of budget now but will get Dynamite Max-Life aluminum shoes and different springs 0.9, 1.0, 1.1mm for tunablity later.

Maj_Overdrive

My Feedback: (11)

This hobby is always a learning experience. Sometimes you figure it out in 2 seconds flat. Other times it has to knock you upside the head for that "ah hah!" moment to sink into your (or my!) thick skull! Lol.

Marciatelli

I honestly thought as I was writing this thread that its gonna be like "turn this 1/4 turn clockwise" or "change the air filter oil"... You know generic newbie type of crap
How little did I know hahaha

Marciatelli

Ive got a general question to Losi 8ight-T 2.0 users or anyone that had to do with the 4 shoe clutch.

I know that there are few posts about them, and I read them but is it worth getting the 4 clutch shoe?

I know how they look like and im worried about my 25mm inside diameter and ~11mm long clutch bell not to be able to fit over the assembly.

Are they pretty much the same fit as 3 shoe clutch, just change the flywheel, nut and the shoes? Do you need a longer clutch bell, or shimming or anything.

What are the general dimensions of the whole clutch assembly? The diameted from shoe to shoe, length from flywheel pin base to top of assembly and the distance from the tip of the nut to flywheel pin base.


Surface wise its really minimal and its more about tunability

supertib

Yeah...its one of the worst....... wears engines so quickly we use it for breakin fuel............truly...

run race fuel...30%, 9% oil............... tune will bemuch easier and much more consistent..... the lower the nitro and the higher the oil the harder the engine will be to tune.............

Marciatelli

Alright, I see your point.
What would be defined as "race fuel" other than the nitro percentage content?
What brands would you recommend?
Not sure what you mean by "the lower the nitro and the higher the oil", does that mean more oil to protect the engine? So higher nitro % is easier to tune, but protects less?
My OFNA Force 32 is running 2 x 0.2mm head shims at 20%/25%, if I move up another 5% how many more shims do I need to add to avoid detonation?

supertib

Where are you ;located ? the HPI fuel in Noth America is likely different then HPI in Europe.....I just considered this

So basically what I have found is that too much oil makes tuning difficult... So hence I say the more oil, the harder it is to tune

Higher the nitro the more reactive the fuel..which means the richer the fuel can be run and still burn clean

High oil does not protect that well if the engines are tuned in..as the higher oil requires a leaner mixture to burn clean...cancelling out the benefits of higher oil..as well increasing the rist of detonation.

A race fuel has a lower amount of higher grade oil as opposed to a bash fuel that has a higher quantity of lower grade oil....

Every brand is different, not all race fuels are good....however fuel is not something to overlook..the running and tuning differences between the products can be vast..with some fuel barely able to run, and others running so well the engines nearly tune themselves....... Fuel is huge and unfortunately the market is flooded with bad fuels that end up creating all sorts of crazy tuning headaches for nitro enthusiasts