I was thinking of something completely different. I've had instances where my engine was up to temp, and I was doing some runs up and down the front straight on my local track to dial in the HSN, and I could hear some "pops" as it was running at high RPM.

I was curious whether that was tune, fuel, or glow plug.....

Put a drop of spit on your finger, and wipe it on the cooling head.....

boils off in less than 1-2 sec = too hot
boils off is 4-5 sec = good temp
just sits there, and doesn't boil off = too cold.

See now some of the other things that i have read was that pre-detonation is usually right around the max rpm that you can make. Perhaps that is the pop you are hearing? I do believe a change to either nitro content, head shims or colder glow plug might be needed in that case.

I havent heard a "pop" come from my engine. Does it sound like a backfire or something? I honestly dont know that ive ever heard one?

The noise i heard was pretty strange, at this point im really starting to think that i was a touch lean up top, and using a glow plug that was hotter than i needed that day. Like I said hard to describe. maybe like the engine wasnt firing once every 4-5 stokes? Hell maybe it was a bad plug, its been changed since lol.

Skipping may be

Lean HSN and Large idle gap. In combo after a fast run you come to neutral and hear a skipping sound.

Good to see people forgetting the temps. Tune the engine for performance always.

Remember temps are suseptable to and will vary up to 20 + deg C depending on

temp gun
Your fuel
Shimming
Pipe
Air filter
Emmesivity of the alloy the head is made from
Chassis
Engine mounts
Tyre choice
Diff silicone selected
Clutch
Ambient temps

bla bla bla

Ok SO forget temps. If the engine is running badly you will hear it. it will sound like a cat having a bad day in a blender.

Smoke trail is also a little tricky. Some fuels smoke more than others. a good fuel will have a medium smoke trail but that depends on the tune. When you tune for ultimate performance you should not see any smoke at any stage. refer to some videos of top drivers in the world on and off road. You will see virtually no smoke trail.

This is due to the fuel being of higher quality and a really lean mix, perhaps just on the rich side of too lean. This condition is for max power and run time. Not recommended for beginners.

Oil coming out of the pipe is actually a good sign but only a few drops here and there. If its oozing out then its too rich.

Fuels that smoke very little is an indication of high quality synthetic. The higher quality synthetics will have a much higher flash point so they dont burn off as much in the combustion process. this is good because you need lubrication on the down stroke too.

Great thread and lots of good info , sorry for blathering lol

M

Thank you sir! I believe this is the explanation i was looking for. I do recall having a slightly large air gap at the time. It makes sense now. It sounds like i had it slightly lean up top with a combo of a large air gap. Just a tad rich on bottom and would skip until it hit the 2nd (semi loaded) stage in the idle.

I was total noob with nitro last year, and getting into it this year I now have a better understanding of it. I just remeber it running like this last year, and then the first run I had of it this year. It has since been retuned, so for now the problem is solved lol.

Thanks again

Very very very common tuning mistake

Some engines will run fine like that and many will not

Mine has always ran like a beast, just sounded odd like that off throttle.

Either way I can add that to my book of knowledge of what to look for if i come across it again. Might be able to help another total noob at the track with it one day lol.

Its amazing how you idle air gap can contribute to a LOT of strange happenings.

Both Grizz (New Zealand) and Massive Mods (Oz) have been involved with GO engines for a very long time. They have repeatedly shown (in the GO threads) that the air gap is the first (and most problematic) adjustment to be made on a nitro engine.

I remember doing a whole tuning guide, using pictures in one of those threads, showing idle gaps and fat bottom ends, etc etc etc

Those that seen it will know why I'm hehehe

I think I know what you are talking about and I have only every really noticed it from a tuning bench. When you hit that spot of the borderline of starting to go lean, and watching the smoke, the engine will blow smoke in a random frequency and that is the point I usually back off about an hour on the hsn needle. I do all this by sight and sound and rarely use the temp gun. You can really hear the engine rpm's from the tuning bench.

Engine tune is an art, get help at the track from someone who is experienced if you're struggling.

You want to be blowing white smoke, have good top end performance.

The bottom end response wants to be crisp, but you want it to idle well.

Be within 200-260f depending on the engine, temperature is purely just to check the engine isn't cooking it's self.

The plug wants to look nice shiny, undistorted and be ever so slightly wet to touch.

Be aware though!

If your clutch settings are off, you're never going to get a good tune.

If your plug is old, you're never going to get a good tune.

If you have a pipe that is too long or short, you're never going to get a good tune.

If you've got a damaged engine, you're never going to get a good tune.

If you've not got good seals from your exhaust gaskets, you're never going to get a good tune.

I definitely agree, but how do you, or most people determine the correct length or best pipe to use
for their set-up without dyno testing?


Bill M.

I think worrying about 'dyno testing' shows a misunderstanding of nitro car racing at it's best...
Track Time is the only testing you need for all questions regarding best performance and best runtime.
Dyno will not show you how changing track conditions plays a GREAT influence when it comes to best performance and best runtime.
Learning clutch setups to match changing track conditions alone takes Track Time and plenty of it.
Best Track Time is right after the mains at your local track!

I really appreciate what you are saying, and I am not saying a dyno is all important,
but like I have mentioned before, there is many myths about pipes. The idea that
there is multiple pipe set-ups because of track conditions is one of those myths,
and a source for fuel economy issues.

The best pipe and engine combination is created completely separate of an track
conditions. An engine set up this way will have the best acceleration before and
after the peak, and the greatest peak HP.

Then it is up to the tuner to adapt that set-up to the current track conditions.




Bill M.

Your statement would make the many engines that get best performance with a Werks 2058 a myth but we know different...
I hear ya bro and I know where your mindset is and it's not going to change anytime soon, good luck and above all have fun at the track!