Hyper 21 engine back up and running w/o stalling. Need help with what to tune next.

[GlowingBulb]

When everything is in the right area then you shouldn't have to adjust any needles between cold start & warm running.

 

If this problem was on my buggy I'd try a drastic change on the LSN by leaning it 1/2 turn & see if the problem gets worse or better. If worse / no change then you know that its not too rich, try 1/2 turn richer from its current position if leaner doesn't work. When making big changes to any needle always watch for smoke & check temperatures to be certain you're not damaging internals - this is usually most important when leaning out the mixture.

 

Just a thought - when you let the buggy idle to a point you know it will bog down when you open the throttle take a look at the fuel tube, is there any tiny bubbles in there? I'm taking a wild guess but you could potentially have a very slight air leak which is being pushed through to your carb when its been idling for a while - probably not though, just trying to think bout what would cause an issue of any description with your fueling after extended idle.

[squarecrumpets]

6 minutes ago, GlowingBulb said:

When everything is in the right area then you shouldn't have to adjust any needles between cold start & warm running.

 

If this problem was on my buggy I'd try a drastic change on the LSN by leaning it 1/2 turn & see if the problem gets worse or better. If worse / no change then you know that its not too rich, try 1/2 turn richer from its current position if leaner doesn't work. When making big changes to any needle always watch for smoke & check temperatures to be certain you're not damaging internals - this is usually most important when leaning out the mixture.

 

Just a thought - when you let the buggy idle to a point you know it will bog down when you open the throttle take a look at the fuel tube, is there any tiny bubbles in there? I'm taking a wild guess but you could potentially have a very slight air leak which is being pushed through to your carb when its been idling for a while - probably not though, just trying to think bout what would cause an issue of any description with your fueling after extended idle.

 

Thanks. I'll give that a go, preferably once the SMD starter box arrives as I always have issues starting this engine. It's difficult to prime etc.

 

Anyway just a thought, I did the pinch test and the engine revs up in about 1 second and stalls in about 4 seconds. Sometimes it takes a second longer. This tells me that it's too lean but the starting procedure tells me that it's too rich. This is what confuses me and I hope you could shed some thoughts on this.

 

Thanks again.

[GlowingBulb]

Also after watching your last video a few times I think I've heard the engine over-running a fraction when you come off the throttle at 1:39, if you listen underneath your talking you'll hear the engine flutter before the revs drop, I'd richen your HSN by 1/8 turn min, maybe 1/4 & see if there is any major change in top end performance. Again, its an observation based on a  video & it was WOT for a long time, probably more than you would usually do if not doing a demo.

[squarecrumpets]

7 minutes ago, GlowingBulb said:

Also after watching your last video a few times I think I've heard the engine over-running a fraction when you come off the throttle at 1:39, if you listen underneath your talking you'll hear the engine flutter before the revs drop, I'd richen your HSN by 1/8 turn min, maybe 1/4 & see if there is any major change in top end performance. Again, its an observation based on a  video & it was WOT for a long time, probably more than you would usually do if not doing a demo.

Hi,

 

Yes I have the engine run on problem. I used to think my throttle was stuck open but now I'm 100% sure it is running on for a second or two. The guys over here seem to think it's caused by the LSN being too lean: https://forums.traxxas.com/showthread.php?265996-Solved-Engine-Run-On-Overrun-problem-when-decelerating

 

however the issues we were discussing above seem to indicate the LSN is too rich.

 

Honestly I've been getting conflicting observations and am not sure whether the LSN is too lean or rich at the moment.

[GlowingBulb]

3 minutes ago, squarecrumpets said:

 

Thanks. I'll give that a go, preferably once the SMD starter box arrives as I always have issues starting this engine. It's difficult to prime etc.

 

Anyway just a thought, I did the pinch test and the engine revs up in about 1 second and stalls in about 4 seconds. Sometimes it takes a second longer. This tells me that it's too lean but the starting procedure tells me that it's too rich. This is what confuses me and I hope you could shed some thoughts on this.

 

Thanks again.

I genuinely wouldn't worry too much about the pinch test, it's very subjective & variable based on how far away from the carb you pinch, how firm you pinch, etc etc. I believe that if the engine is performing correctly & isnt overheating then you're pretty well tuned.

 

What fuel are you using, I know that Optifuel fuel, especially the 25% RTR mix is very smoky, you can be too lean using that & still get good smoke,

 

When checking the tune of my engine I use a Fastrax IR Temp gauge to be sure I'm not cooking it, if I see the cylinder head temp (top of glowplug) higher than 130degC then I richen the mixture by 1/8 turn

 

https://www.modelsport.co.uk/fastrax-temperature-tuning-temp-gun-and-screwdriver/rc-car-products/374120 - its out of stock at the moment everywhere I've looked but there are similar available, I like the rubbe bung on this type that makes sure you're locating it correctly in the heatsink at a repeatable distance each time.

[GlowingBulb]

7 minutes ago, squarecrumpets said:

Hi,

 

Yes I have the engine run on problem. I used to think my throttle was stuck open but now I'm 100% sure it is running on for a second or two. The guys over here seem to think it's caused by the LSN being too lean: https://forums.traxxas.com/showthread.php?265996-Solved-Engine-Run-On-Overrun-problem-when-decelerating

 

however the issues we were discussing above seem to indicate the LSN is too rich.

 

Honestly I've been getting conflicting observations and am not sure whether the LSN is too lean or rich at the moment.

Its a minefield mate, you can be too rich LSN & too lean HSN at the same time. I do think you're too lean HSN now I've heard that overrun. I think you're bogging with too much fuel after extended idle also. 2 problems caused by separate needles.

 

If it was my buggy I'd richen off the HSN, that's an easy fix, you're just slightly over lean IMO. Once that's done you can forget about it (until it gets much hotter / colder than the day you did your tune, or you change fuel brand, or glow plug etc etc).

 

Personally I think you're over rich on your LSN & it needs to clear its throat on WOT after a while so you need to reduce the fuel being presented to the throttle after idle.

 

Tuning is really subjective, there must be science behind it all but your ears, eyes & a screwdriver seem to be all that's available to us mortals

 

 

[squarecrumpets]

I pinch the tube right at the top of the fuel tank so I don't burn myself  yeah it's non scientific. Will ignore that for now.

 

Will try richening the HSN and leaning the LSN as you've suggested.

 

Yes Optifuel 25%. Thanks for pointing out that the smoke can be misleading with this one. I wasn't aware of that. I've also got a bottle of Optifuel 20% which gives less acceleration.

 

I've been using a FLIR IR camera to check the temps. I'll look for one of those gauges that you've suggested as they aren't too expensive.

[GlowingBulb]

Best of luck mate!

 

You cant beat FLIR for accuracy, they've been around for years, I used to nick 1 from work to check temps when I started to my buggy but I found that I'd get variable readings depending where I pointed the gauge (obvs). With a pen type that has a bung to push into your heatsink you can be sire that its always pointing in the same position & is the same distance away from the glow plug.

 

https://wheelspinmodels.co.uk/i/252617/

 

That looks exactly the same as my Fastrax just a different colour, you can see the bung installed on the photo which helps consistency. I'm sure its not as accurate as the FLIR but I'm really interested in the same reading every time as reference not a reading accurate to 0.5deg 😉

[squarecrumpets]

3 minutes ago, GlowingBulb said:

Best of luck mate!

 

You cant beat FLIR for accuracy, they've been around for years, I used to nick 1 from work to check temps when I started to my buggy but I found that I'd get variable readings depending where I pointed the gauge (obvs). With a pen type that has a bung to push into your heatsink you can be sire that its always pointing in the same position & is the same distance away from the glow plug.

 

https://wheelspinmodels.co.uk/i/252617/

 

That looks exactly the same as my Fastrax just a different colour, you can see the bung installed on the photo which helps consistency. I'm sure its not as accurate as the FLIR but I'm really interested in the same reading every time as reference not a reading accurate to 0.5deg 😉

Ahh I heard your message come in but thought I'd read it after placing the order. I've just ordered the Fastrax one.

 

The FLIR stuff are a bit fragile. This one is much easier to use and quicker to position. It's definitely a good investment.

[GlowingBulb]

Just took my sons buggy out this evening, had what sounds like exactly the same problem as you're having, bogging after idle. Didn't matter what I did with the needles couldn't get it right. 

 

I managed to find the issue because the idle was all over the place - I found a slight airleak in the fuel filter, you could see fine bubbles entering the fuel messing up the mixture, not bad when blasting about but the bubbles got bigger when idling. 

 

Could be worth a look for you also? 

 

[squarecrumpets]

23 hours ago, GlowingBulb said:

Just took my sons buggy out this evening, had what sounds like exactly the same problem as you're having, bogging after idle. Didn't matter what I did with the needles couldn't get it right. 

 

I managed to find the issue because the idle was all over the place - I found a slight airleak in the fuel filter, you could see fine bubbles entering the fuel messing up the mixture, not bad when blasting about but the bubbles got bigger when idling. 

 

Could be worth a look for you also? 

 

Hi,

 

I've decided to take the buggy out for a quick spin as the starter box would only arrive tomorrow or the day after.

 

So I've richened the HSN by 1/8 and leaned the LSN by 1/2. After doing so, I've noticed the overrun is a lot shorter (approx 1 - 1.5 seconds). The bogging down after sitting idle is also a lot less. I think the LSN needs to be leaned some more. Unfortunately I ran out of fuel before I could record a nice video.

 

I forgot to take the head temp gauge with me. I'll check the temps next time.

 

The hoses to the fuel filter are very tight so no leakages there.

 

I don't use after-run oil as I tend to start the engine up every 2 - 3 days at the moment.

 

Hopefully things will improve. I hope I'm on the right trajectory with this one....

 

 

Cheers.

[squarecrumpets]

Hi again,

 

I have received and set up the starter box which works like a charm and is very helpful because my engine stalled numerous times today. The idle was too low at first.

 

I also started using the IR head temp gauge and found the engine temps after high speed runs to be way too high at about 120 degrees C. The spec for this engine says the max should be 107. I then started richening the HSN but it didn't help much and the engine stalled after high speed runs a few times.

 

I then returned the HSN to factory settings and leaned it by 1/4 turn and the temps came down but was still quite high so I richened it by 1/8 turn. i.e. it is now running 1/8 turn leaner than the factory default settings. The temps are now around 100 degrees C but the acceleration is noticeably worse than before. Am I stuck with this config due to the temps?

 

btw the above was with 25% Optimax.

 

After that I switched to 20% Optimax and the temps came down to about 93 degrees C but the performance is much worse now.

 

As usual any advise would be greatly appreciated. Thank you.

[GlowingBulb]

I'm not familiar with your engine so I cant say for certain but 107degC seems very low as a max temp, I aim for 120degC above ambient temperature (so if air temp is 20deg I avoid going over 140degC measured at the glow plug).

 

Edit: I've checked CML's website & these temps are correct, it runs cooler than mine.

 

Performance will take a hit running 20% Optimax but temps will drop due to a smaller detonation within the engine.

 

It does sound like there's something off if you're struggling to hit a decent tune; the adjustment windows seem very small, you should be there or there-about & have a tolerance of a couple of hours turn either way without too much difference in performance. You've done all of the basics - factory default settings, lean off small turns on HSN until improvements are seen then adjust LSN the same.

 

It might be time to look at other variables rather than just your needles - is the glow plug correct type, functioning at peak, correct grade (temp), do you have a new 1 to replace it with to try & eliminate this? Is the exhaust gasket seated correctly / not damaged? Is the pressure return tube from exhaust to tank in good condition without kinks or holes? Is your fuel filter clean & passing fuel correctly? Is your air filter clean? Is the fill lid on your tank seating correctly? 

[squarecrumpets]

I'm not familiar with your engine so I cant say for certain but 107degC seems very low as a max temp, I aim for 120degC above ambient temperature (so if air temp is 20deg I avoid going over 140degC measured at the glow plug).

 

Edit: I've checked CML's website & these temps are correct, it runs cooler than mine.

 

Performance will take a hit running 20% Optimax but temps will drop due to a smaller detonation within the engine.

 

It does sound like there's something off if you're struggling to hit a decent tune; the adjustment windows seem very small, you should be there or there-about & have a tolerance of a couple of hours turn either way without too much difference in performance. You've done all of the basics - factory default settings, lean off small turns on HSN until improvements are seen then adjust LSN the same.

 

It might be time to look at other variables rather than just your needles - is the glow plug correct type, functioning at peak, correct grade (temp), do you have a new 1 to replace it with to try & eliminate this? Is the exhaust gasket seated correctly / not damaged? Is the pressure return tube from exhaust to tank in good condition without kinks or holes? Is your fuel filter clean & passing fuel correctly? Is your air filter clean? Is the fill lid on your tank seating correctly? 

 

Thanks I have checked and been checking all those things. They all seem to be spot on.

 

Today I tried to tune only the HSN based on temperature. I brought 2 of those IR gauges to cross check accuracy.

 

Interestingly even at factory HSN settings on 25% fuel the temp goes up to over 110 Deg which is out of range.

 

Should i try a cooler plug? I’ve been running medium and the weather has been quite hot.

 

EDIT: The newer version of the manual says the normal range is

 

Thanks.

 

 

 

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