dubya86

I have a 3.3 nitro 4-tec and after I make a couple of high speed passes I check the temp and it never reads over 160 degrees at the plug without the car body on... now I have not been in the RC hobby that long, but my LHS told me that 180 degrees above the ambient outside temp is a good mark to shoot for... the thing is the car runs beautifully, maybe just a touch on the rich side.

My temp gun seems to be fairly close to being accurate but i cannot figure out for the life of me why it is running so cold... so I guess my question would it be safe to lean it up until the temp get about right or should I get someone else to make sure my temp gun is getting an accurate reading at the plug?

And please no Traxxas bashing its what I have so if you don't like please keep it to yourself!

UG0TB4NN3D

My Feedback: (1)

Well, this isn't bashing, but I would recommend you get a new engine as soon as possible, as I've heard a lot about those engines, and not good things.

Try leaning the engine, but don't lean it so much that you don't still have a nice trail of smoke, you want the engine to stay nicely lubricated.

What fuel do you use?

Also, 240 degrees is about where you want your engine to run, not +180 degrees.

stanggod

hold your temp gun next to your thermostat in your house.thats how i test mine.i would run your 3.3 at 200.

dubya86

@UG0TB4NN3D
I will probably look at getting another engine after this one blows, but so far there have not been any problems so I am not too worried right now.
I run Traxxas 20% I know its not really the best to run but I have not had any problems with it yet.

@stanggod
That is how I test my temp gun it is usually +- 1-2 degrees, but thanks anyway

SAVAGEJIM

One of the hardest thing about this hobby is taking the temp correctly with the cheap chinese-made hobby temp gus we use. These things are primarily inaccurate because it is hard to aim them directly onto the hottest part of the plug. I suggest you buy an automotive or HVAC grade temp gun with laser pointer so that you can point it exactly on the hot part of the plug to get an accurate reading. The chinese-made hobby guns simply dont have that (except for some of the higher dollar ones). Worse yet, several other members of RCU have said that the hobby temop gus are prone to being off by as much as 30degrees F and/or going badly out of calibration (if that is even possible).

The automotive/HVAC grade temp guns will cost alot (at least $100), but you are assured of their better quality, accuracy, and most importantly, the laser pointer.

NOTE: Even with an automotive/HVAC grade temp gun, dont think you can stand on you feet and take the engine temp of your RC 3ft below. You will still have to hold it close to the engine, but just high enough for you to see that the laser is on the hottest part of th plug.

dubya86

I use a Raytek mt4 IR thermometer. I have tested it against other thermometers in my house and it is usually pretty well on. when I do check the temp it place the sensor right above the plug and check the temp at least 3 times but i never get any hotter readings than what i do right over the plug...

I use the same gun on my Nitro Sport and it works just perfect.

I think I will try to run the car after I get off work tonight with the body on and see what kind of readings I get.

Thanks for the help so far.

downunder

If it's running beautifully and slightly rich then why mess with a good thing just to get a temperature it doesn't want to run at?

Argess

I think it's a summer winter thing. If it runs 240ish in the summer, and then 160ish in the winter, you may be running with a lot more "pinch" in the cylinder. This puts a lot more strain on the crank and rod, etc. Some people put a sock over their cylinder head in the winter. I don't as the glowplug temp doesn't seem to drop much with colder outside air temps. On the other hand, the top cooling fins are much colder in cold weather than in hot. I admit, I am at a loss to explain why the glowplug temps don't seem to drop as much as the ambinet temp drops from season to season. Maybe it's because the combustion heat is the same and it has to travel past the glowplug to get to the finned cooling head?

So, I'm no help to you, but if I was measuring a big temp drop in cold weather, and I was happy with the engine tune, I'd put a sock over the head. I once broke a crank-pin by running an engine too hard at around the 160F mark, but that's because I was experimenting and overcooled an engine that had always run hot.

SAVAGEJIM

It's a good thing thet you do take several readigs in one setting, not just on, I do the same when I have to resort to the chinese temp gun. I always get a discrepency of as much as 20dgrees F. I always go with the hottest reading (I personally do 5 readings in one setting, but 3 should be sufficient).

Sorrily build chinese made temp guns aside, if you simply cannot hit 200degrees F, before even starting the engine, try preheating it to 200degrees F with a hobby grade air gun (basically, a hair dryer with a super heat coil).

Also try doing several straight-line full trigger passes up and down the street once the engine is fully warmed up. I gauranty that the full speed passes will keep your engine above 200degree F.

dubya86

@ downunder
I have to say i agree with you at least for the most part.

@argess
Normally I would have said you are right but the thing is it was around 75 out when I was checking it... I think the coldest we got down here was 28 this winter but I usually run it when it is over 60 out

@ Savagejim
agreed a cheap oriental made gun is not the best way to do it but that all i have right now... also i may try to pre-heat it after my next paycheck and can get a heat gun.

thanks