Venom Racing Temprature Monitor

[Mondo]

In the past I used an IR heat gun to (try and) get head temprature readings.
The problem with this particular temprature gun was the huge variations in readings, for example between 190° and 240°F on the head. This caused a lot of frustration, so I reverted to using a drop of water on the TRX 2.5 head to try and work out if it was within a safe temprature range.

Last week my new Venom Temprature Meter arrived from the U.S. and needless to say I fitted it on the TRX 2.5 motor.
In my rush job installation, I didn't fit the sensor on the head, instead I fitted it on the cylinder barrel, ont he other side of the exhaust port, but about level with the exhaust port!

On Sunday I took the MAXX for an asphalt run as the Orion StreetSweeper tires reveal.
The readings I got from the VTM were astounding.
According to the VTM, my tempratures were about 280° to 290°F with a maximum recorded temprature of 302°F!

The weather was cloudy and cool, air temprature was about 18°C
I used 20% Nitro with a McCoy MC59 glow.
I richened the mixture quite a bit but the tempratures were still too high. In fact, I leaned it back out again because there was nothing wrong with the performance, the MAXX was doing wheelies on demand from a standstill and generaly performing exceptionaly well. It has had about 3/4 of a gallon of fuel thru it, so it's well run in.

I can only attribute these insane temprature readings to where I had mounted the VTM sensor.
I think it was a hot-spot, because the sensor was mounted on the cylinder/barrel side that is about 4~5mm away from the EZ-Start motor can.

I have now remounted the VTM sensor deep in the head fins, where there is a slight gap level with the head screws/bolts.
I am still to try the VTM out with the sensor reinstalled on the head and not on the cylinder/barrel.

The reason for my somewhat detailed explaination is to see if any other Members have had similar experiences with VTM, Traxxas or other makes of digital temprature meters.
Here is a pic of the VTM on my MAXX

 

[Mondo]

New sensor mounting position

This is a (decent, I must add) close-up picture of where I've now mounted the sensor on the TRX 2.5 motor.
Is this area good for sensor placement?
Any feedback would be appreciated

 

[GilBeQuick]

Yeah man, that's ok. The closer you can get to the glow plug the better. The temp on the plug is the reading you want to have. Good luck, looks nice.

 

[LarryA]

I've been thinking about this and something just doesn't seem right. If you are saying that the probe should go higher on the head then the reading should be lower due to the head doing its job of removing heat from the engine. If Mondo has the probe around the cylinder and is getting high readings, then that is what the temperatures really are at the cylinder. Then, why put the probe at a location where heat has already been dissipated and the temperature is lower than at its highest location? This somehow doesn't seen to make much sense. The hottest location should be the combustion chamber just blow the glow plug where it ignites the fuel. That would be, in reality, just below the head.

 

[Mondo]

Positioning

LarryA,

You made a valid point in your reply.
But, I quote from the Venom Racing web page:

"Slide the probe loop over the engine head and position it as close to the bottom of the head as possible. For best results, ensure the probe sensor, which is under the heat shrink, is at a 90-degree angle to the exhaust port"

So, what Venom say is measure the temprature at the bottom of the head - not at the crankcase/cylinder area.

This is my point, where do people measure Nitro engine running tempratures? At the head or crankcase/cylinder?
Obviously reading at the bottom of the head would provide a slightly lower temprature reading than the cylinder/barrel area.

I would think thermal measurement is done at the head, as in real world use the car would have a bodyshell on and to measure tempratures below the head wouldn't be feasible at all.

I have attached a pic from Venom's instruction page.

 

[Bash_N_Thrash]

A couple things that have always bothered me about temp reading:
1. With a temp gun you are told to read down the glow plug hole and move the gun around to get the highest reading.
2. With a temp gauge you are told to put the sensor at the bottom of the heat sink or cylinder head, between the case and the head.
3. For the water test you are told to put a drop of water ont the TOP of the cylinder head.

All of these methods are different and would give a different reading. All are however a good way to get the approximate temperature of the engine, +/- 50 degrees would be my guess. None are perfect. I think the moral of the story is there is no perfect way to be absolute about the temperature of the engine. Just my $.02. I suggest tuning for performance and check temps with a temp gun occasionally after a heavy run to make sure you are within decent temp ranges. Other than that, just have fun!!

 

[LarryA]

I have an MIP gauge and a IR hand held. I pretty much gave up tuning by temperature and tune by performance. I do occasionally check the temp with the hand held for some sort of reference point but don't worry too much about it unless I get really high readings. As has been stated, temperatures are different no matter where you take them from.
Anyway, blown engines are a good reason for a Hobby shop run.....:write:

 

[Mondo]

Hot....hot.......hotter than Hell....

Bash_N_Thrash, LarryA

Valid points. I'm going to leave the Venom Temprature Meter just where it is and try and work from a "fixed reference point"
We can use laser, infra red, spit tests, but either way most seasoned Nitro owners are more than capable of working out when a motor is well tuned or too lean

 

[Mondo]

Run with re-located VTM

As this Thread will show, I relocated the Venom Temprature Meter last week.
I placed it in the gap on the TRX 2.5 head, just above the glow and level with the head bolts.

Today I took the MAXX for another parking lot thrashing. The air temprature outside was 26-27°C a sunny day.
I got the MAXX running sweetly, popping wheelies on demand and running generally well.
The VTM still logged maximum tempratures over 300°F, in fact my highest reading was about 313°F!
That was when the MAXX was running a little lean, but not too lean.
If I put a drop of water on the head, it would sizzle slowly, not hiss and evoprate (a sign of overheating) So, all in the MAXX was within the correct running temprature range

Conclusion:

On board temprature gagues may seem like the burning bush of Nitro thermal management, but obivously they are not.

Venom Racing: Nice, but no cigar... :ha: