Tuning OS RG .21 engine by temperature questions

[kryczech]

Hi all. I'm new to the forum and 1/8th scale buggies, and I've got a question about tuning my engine.

I recently finished building a Kyosho Inferno MP7.5 and since I'm new, I opted for the inexpensive OS RG engine. I've broken it in, but now it's time to tune the engine in. I know that performance is what tuning is about, so actually driving the car and seeing how it reacts is going to be the best measure of tuning. But I'm also afraid that I would end up running it too hot, and I don't feel like having my engine go bad too quickly. So, I went and got a $35 Duratrax IP temp gauge this afternoon, and I had a few questions about how to use that to make sure I'm not running too hot.

1) I've searched around and checked the OS manual (no mention of temperature), but I can't pin down where the temperature should be running on the engine. I've seen suggestions from 210-260 degrees. I've been trying to keep it around 220. Does that sound right, or should I heat it up just a little bit?

2) When should I take the temperature? I haven't run it at a track yet, just out in my yard and the road. It runs noticably cooler when I'm hopping around in the yard, and much hotter after a few WOT passes on the road. I'm guessing that has to do with the head losing the heat quickly. Running around in the yard, I'm running about 215, but three or four WOT runs and the temp gauge is showing me around 235. Should I be shooting for average temp or maximum temp?

3) Anyone have any tips on using the temp gauge? It's a Duratrax Flashpoint. I've been pretty much holding it directly over the top of the head pointing at the glow plug since that puts the glow plug itself about 1 inch from the end of the gauge. I still find that the readings vary a fair amount (+/- 5 degrees or so). I've just been making sure to take 4 or 6 readings and kind of eyeball average them. Does that sound about right?

Thanks for the help.

--Kryczech

[cbreaker]

Everything you're doing sounds right.

As far as temps, every engine has it's own "comfort" spot, usually between 220 - 270. You should be able to tell when it's tuned the best; too lean and the temp shoots up quick, too rich and it boggs down on you. At the very least, you don't want the temp above 270 when running the engine hard, preferrably below 250. These are very generic numbers though, your engine may vary.

I've found that my little stock GS B01 engine puts around the field at 230 or so, and runs hard at the track around 260.

I'd say check the temps often. If your temp gun/thing has a setting for "max" (it will show the highest temp recorded on the screen and hold it until it reads something higher) I'd suggest using that.

[niggle]

1. The fuel pressure will decrease as the fuel tank empties, leaning out the mixture and increasing temperatures as a result. Tune for the worst case (tank nearly empty) and set a safe temperature in this case.

2. Set your IR temp gun to "max" mode.

3. Don't tune by temperature alone, look for a visible trail of blue smoke when running at wide open throttle with a nearly empty tank.

[olds97_lss]

I ran the 21 rg on a 21 maxx for about 2 gallons, then the crank shaft snapped in two... bomber ran the same engine in his 21 maxx and shattered the connecting rod in the first gallon. He did the same with engine #2. I want to think we were both using to hot of a plug causing it to detonate early. Being as we were both relatively "new" at this racket, we were using OS A3's in our engines. They ran clean with ok power. We kept our temps below 250 and above 200 all the time.

Now that we have a little more time under our belts and doing some reading, the hot plug is what I think got us both. It was detonating as the piston was coming up, putting a lot of strain on the internals.

Consequently, we both now run different engines. I run an OS #8 in my 21 now. Much better power than when I try the A3. A little more fickle to keep the low idle, but other than that, it runs really well.

235 isn't hot at all. You could probably lean it out a bit. Just try to stay below 260 and above 200 and you should be just fine. Just keep in mind the plug thing. Hopefully my mistake won't be yours...

[slim1]

i race a RG, i love it. it is a awesome engine!
if my tank is full, i hover around 212 and the end of tha tank-race it might be from 260-280, but it has been hot and our track is indoors...

the throttle responce is sickning on it, just explosive!

im going on 2.75 gallons and will prolly finish that off tomorrow at the races.
still good compresion. im pretty religious on my warm up. i let it run for a few on the box, blipping it it clean it out, once its cleaned, ill put around the track, 2nd lap i start giving it more so it gets cleaned out again, and befor that 2nd lap is over i can punch it full throttle. and maybe one more hot lap and im ready. almost 3 gallons and still had some pinch left, i just put a slight squeeze on it last week and it ran about the same...

[Jim52786]

Originally Posted by cbreaker

Everything you're doing sounds right.

As far as temps, every engine has it's own "comfort" spot, usually between 220 - 270.

I absoultely agree. Every engine is different. Never tune an engine just by the temp, make it run good and then check the temperature. I run an OS RG in my 7.5 and it runs great. It has awesome low end (although it lacks alittle up high) and is extremely reliable.

[slim1]

well yesterday at the end of the tank-race i temped at 212. i was thinking about it, i havent touched the carb in almost 3 months! what a great motor, at this point ill never buy anything else! for this track anyway!

[dgrobe2112]

really.. cant say anything.. however.. if your are truley running 212.. then you are not getting the full performance of the motor.. these motors.. and i mean all motors are designed to run at around 230-240.. they run really good at those temps..

just a little side note.. it is just as hard on a motor to run at 200 degrees.. as if you were to be running at 300.. running too fat is just as hard as running too lean..

[slim1]

i agree on the too cool part 100%!
i really do believe tho the motor is performing at its best, it hangs with the big dog motors of the track on the straight, and explodes when you grab the gas, and never flames out. that last race day, it was humid so maybe thats why it temped lower than the previous weekend. i dont rely on temps for tuning, i listen and feel what the motor is doing, but that is not what were talking about here...

my father has a RG aswell, and his doent quite respond the way mine does, even with identical carb settings. id like to try my carb on his motor sometime...

[dgrobe2112]

not all motors or carbs are the same.. you will rarely find a motor that runs the exact same settings as another.. even if its the same motor.. or anything like that.. each motor is its own.. and of course.. each has its own settings.. motor manual will give a factory setting which is break in settings.. and you tune from there...