RPM vs. Temp for initial tuning

[mcstoufer]

Having enjoyed Nitro boat and planes for the past N years, I am suprised to see talk centering on using the temp of an engine to properly tune it. While the correlation of temp to performance is obvious here, has anyone ever considered reading the output RPMs of a mill as well to determine peak performance?

There are just as many rpm meters out there that read blade revolutions. This could easily be adapted to marking part of the flywheel. In fact I recall seeing something magnetic that could be attached and read quite easily.

 

[racing revo #21]

I've heard of those devices for the flywheel. Never actually seen one. So I can't really tell ya. I think its pretty cool tho.

 

[ZANDOR]

You hear talk about temp guns...But I would say 70% of us tune by ear...
You will hear us ask noobs what there temp is...This is to help under stand just what is going on with there rig...We are not there to see or hear it...When trying to help over the net..It is some times the only way to truly help some one out.that knows nothing about there RC!

 

[mcstoufer]

These stances make perfect sense. However, this now begs the question, are these nitro motors special in that they operate best in a specific heat range irrelevant of the HP and RPM at the time?

I started this weird thread because neither boats nor planes would tune their engines via temp (being either air or water cooled) and tuning by ear is useless due to the either the prop or large tuned pipe/mufflers being used.

 

[jon2]

These stances make perfect sense. However, this now begs the question, are these nitro motors special in that they operate best in a specific heat range irrelevant of the HP and RPM at the time?

Generally, all Glo- powered nito motors operate best above 200 F and below I would say 275. Some engines run better hot and some not. Now where exactly in that heat range depends on the needle settings. You can get your car above that number by leaning out the HSN but to get the optimal running conditions, the tuning of it needs to be done properly.

 

[Candyman]

I'm suspecting that cars have a much more difficult time cooling, thus temp is critical. With boats, they typically have a water cooled head, yes? Thus keeping temp down. And planes allow the head to cool in the prop wash. Again helping control temp. But our cars have a much narrower allowance for cooling airflow. If we tuned for optimal RPM's, I'm certain we'd be running at engine killing head temps most of the time.

 

[mcstoufer]

Proper tuning is really what I'm driving at here. While tuning by ear will get you a ballpark estimate for peak performance, I am looking to incorporate the techniques used for the boats and planes. Will these specialized engines respond to these methods, or will you just spend half the day retuning because the weather has changed?

Do you just find a good running temperature and look to maintain that for each run?

 

[sweetdiesel]

Proper tuning is really what I'm driving at here. While tuning by ear will get you a ballpark estimate for peak performance, I am looking to incorporate the techniques used for the boats and planes. Will these specialized engines respond to these methods, or will you just spend half the day retuning because the weather has changed?

Do you just find a good running temperature and look to maintain that for each run?

It all depends on what the ambient temps are. My temps vary between 200 and 275 depending on ambient temps. Often if I am running below 50 degrees ambient temps, my mill has a hard time getting over 200, so I wrap the head with paper or a sock to build some heat into it.

Like others have said, the more experienced users will tune by sound and smoke, then check temps occasionally to make sure the mill is not running too hot.

 

[mcstoufer]

I'm suspecting that cars have a much more difficult time cooling, thus temp is critical. With boats, they typically have a water cooled head, yes? Thus keeping temp down. And planes allow the head to cool in the prop wash. Again helping control temp. But our cars have a much narrower allowance for cooling airflow. If we tuned for optimal RPM's, I'm certain we'd be running at engine killing head temps most of the time.

Ah, sweet talking Candyman! Therefore we can safely assume that optimum running conditions (HP & RPM) are constrained by acceptable heat limits and not by tuning every ounce of power from the mill.

And yes the boats do have a water cooled head (and for the exhaust manifold as well). How ironic that you HAVE to keep the boat running at high idle out of the water to let things heat up and then idle it around in the water so you don't crack the head with a sudden flush of water.

It all depends on what the ambient temps are. My temps vary between 200 and 275 depending on ambient temps. Often if I am running below 50 degrees ambient temps, my mill has a hard time getting over 200, so I wrap the head with paper or a sock to build some heat into it.

Like others have said, the more experienced users will tune by sound and smoke, then check temps occasionally to make sure the mill is not running too hot.

So it is possible to have a crappy day of running if you can't maintain a minimum temp on the head. And by leaning it out to bump up the heat, you loose power?

I'm glad I asked before I started to break one in thinking it was just like a plane engine!!