Engine temp range
 

Yes the ever asked question of "what temp should my engine be?"

now I know the answer is "tune to performance not temp."

However, what is the temp that no matter what is too hot? With my current engine which is a JP Modified Mugen x12, what temperature should I stay below? Looking for more concrete info other than "if it sounds and feels good then it's good." basically after running a few passes at high speed and bringing the car in I get temps around 260F and wanna know if this is safe. I can richen up a bit to drop temps right?

Thanks for any replies.

250 is a nice place to be at, i would say keep it within 10 degrees of 250 and you should be just fine.

I agree with randay. As long as the engine is running well, I try to make sure it's in the 240-260F range. Less than 240 and I would say I'm running too rich. More than 260 and it should begin to sound too lean. 300+ is bad, although the CRF can handle 300+ without blowing up on you or burning plugs in 4-5 minute heats.

BTW ... I am by no means advocating running a CRF at 300+ degrees. :sneaky:

Ok then I will richen it up a little bit and make sure it stays below the 260 mark.

someone does it like this;
use thrumb to stop the engine at idel at flywheel, let it cold down, take out the plug, stamp the plug onto our hand or palm, you will see a ring by the fuel. The more wet it is, then it tells you there is still room to lean.
But make sure you observe the temp and having enough smoke.
just my 2 cents ;)

The hotter the better . If youre tuning for racing you cant rely on smoke out the pipe as a sign.. Different fuels will smoke more or some less, some not at all.

Many things determine the race temp on an engine so its a very broad question to answer.

I rarely temp my engine , i tune for performance till it chokes. I get just over 9 mins tank time in my MTX3. Ive run over 15 litres through it like this hitting temps in excess of 160 deg C the engine still has great pop .. Thats running 7% oil total..

Anyway i hope this helps some

Cheers MM

Mark are you mad??. The guy asked a simple question Ya shore you can run engine like that. But under normal use you would stick around the 240 to 260 deg f and 120 to about 130 deg c for a 12 size engine. A .12 engines normaly runs hotter than a .21 engine i try to keep my 21 engines around 100 to 125 deg normaly about 110 or there abouts. Regards Jeremy.

Usually you want your engine to run around 160-170F more than the ambient temp is.
For example if it's 60F outsite then the safe engine temp is around 220-230.
If it's 90F then 250-260.
But this is all theory since the engines cooling head, the body, the gearing, the track,... all affect the engines temps.

Of course you can't run it for 5 minutes and say it's OK at 250 that it temps now and later on you go and run a 40min final and expect it to stay there...!!

There is also a point where the metals of the engine will start to wear out much faster at a given temp which for each engine this differes.

Temp Guns and Engine Tuning.
 

Tuning by temperature depends on alot of variables. Temp Guns as well. I have seen temp swings of 40 degrees F between guns. Also the method on how someone temps it is another factor. I use an Exergen 501, and try and temp it the same way each time. I make sure the cone is perpendicular to the head entering the cooling head.

If you use a temp gun.........use the same one each time. It will help you gauge a baseline reading on that motor.........and that particular day's ambient temps. For mains, you might want to start the motor a tad rich. Perhaps an hour or two richer on the top end. Many motors will come in 20 to 30 degrees hotter after ten to fifteen minutes of hard running. If your on the threshhold of too lean before a main........you might come in overlean during the main.

I know this topic was about specific temp...........but some motors run great at 240...........some won't even get out of there own way unless at 280(.12's that is). Depends on the motor.

tune the engine by performance ,not all by temperature,

Here in Hawaii, our temps are usually between 80-90F, give or take 5. That's why randay and I would say 240-260F. :D

Now days, given the different head designs and materials, it's hard to gauge what is accurate anymore - and you have to have a very accurate temp gun.

Our humidity swings quite a bit throughout the day. You have to fuss with the engine quite a bit. We only get 3 minutes of warm-up on the track to figure out how the humidity has changed the tune of our engines and then figure out how much to turn the HSN just before the start of the race. If you know your engines well enough, you can guess-timate what the settings should be on the starter box. If you don't know your engines, guess-timating can be a bad thing.

IMO, temp-ing is good to help tune your engine, but should not be the only means by which you tune your engine. Tune for performance first and then make sure you're not about to blow up your engine by taking the temp. ;) Well, that's how I do it. :D

It's true you can't tune for performance and worry about temps...it will always be high...at least in most engines and most places.
That's why engine manufacturers keep increasing the size of the cooling head.
For example the new O.S. speed, the new O.S. VG, the RB S3, Radical, SH, ...
You can't have the same cooling head for all over the world.
In very cold climates you might need a head of an on-road engine...and on hot climates you might need an off road head on an on-road engine to keep the temps down.

You have to make sure that you have the right cooling head for the climate you race at.IF you care about your engines...!!!
The best case is to have the temps at a safe level and still be able to tune for performance.

I normaly tune my engines to i have a good paformance and then do a few laps and just check the temp if i feel its to high for the condishions ill ritchen it. you can not tune an engine to temp but i have "ruff" temp ranges i try to stay with in. Regards Jeremy.

That's the way to do it.

I got all that I was wondering if there was a point where I should say "that's too much"

At 300F plus, I would be feeling sorry for what I am doing to my motor. "thats too much" is totally up to you and how long you want your motor to last! :nod: At 240-260 you should be making decent power, at 280 you should be screaming, at 300+ you should be crying and screaming. :lol:

Amen to that... tuning for performance is not for everyone. at what price are you willing to pay for performance is what you should be asking. common sense tells me that metals in general when you heat it up will soften and expand. at 280+any metal will soften up combine that with 43000 rpm+ you can do the math. my friend do what your common sense tells you. everyone here feels that their way is the way, rightfully so in some instances. just be careful..

I don't think we posted different ways here.
I think all of us said almost the same thing!!

Tune for performance and then check the temps if they are at safe levels...that's it!!!!!!!!!!!!!!!

It's 280F on the outside. On the inside it is at least 450F degrees. I agree though that if you are running your engine over 300F then you should be cautious.

Yes Jeremy i am mad , thats why im in this business lol

There is no way you can limit an engines temp range for tuning, you tune for performance and where ever the engines temp is at peak tune thats where it like to be.. pretty simple.. If you were to tune to temp , lets say you get it to 120 deg c then change the pipe, 9 times out of 10 the temp will change, then if you change the fuel , it will change again, if you change the body , tires , surface , air filter .. all these things will change the engine temps. So that why i dont bother with it, I tune for performance only adn the logevity of my engines and that of my racing team is better for it .. Im just stating real time experience..

Anyway its a scarry thought to run engines that hot but believe me they dont mind it at all .. A well built engine should lean choke on fuel intake before it causes a malfunctoin.. it a malfunction occours running at say 140 deg c theres a good chance that the engine materials couldnt handle it.

MnM

For those that are Celsius challenged (such as myself)...

120C = 248F
140C = 284F

lol Celcius challenged ..

250f is fine. 300f is pushing it a bit!

I stopped using temp guns years ago. I only tune with spit now, as it is always consistant.

If you dab a drop of spit to the cooling head and it stays there and slowly evaporates then you are too cold. If it quickly jumps off the head then you are generally too hot. You want the spit to sizzle for about 1-2 seconds then dissapear to be within a safe range.

More important in my opinion is to remove the head button regularly and view the combustion color on the head button and piston crown. This gives you a much better idea as to whats going on inside the engine. Also you will get quick warnings to dangerous running conditions such as detonation and lean conditions.

Also look for slight wetness to the piston top. Too much oil and your too rich, and dry piston you are too lean.

Constantly removing the head button will also give you the opportunity to readjust the head clearance with shims, which is one of the most important tuning adjustments with these engines for all out performance. Just take care to always seat the head correctly and tighten evenly. And lastly, don't overtighten the head screws or you can deform the block putting pressure on the piston sleeve. This will cause pressure points and you WILL loose power and destroy your piston/sleeve set.

Just my 50cents worth!

BK

Ok I got it anyhow, I was just concerned with temps while running with the body on and comming in to refuel and the tem was way up. I think I got it now.

Hey MXWRENCH

i have friends in RC that have had way more experience than me running engines to about 350 F and have no problems. Im not meaning to go against what your saying, its quite sound advise to stay within a certain temp range but some engines just like to run hot.. some dont its hard to guage thats all..

I know I had a motor than ran 280F :flaming: anything lower the motor didn't perform well :weird: and people would say the motor is too hot :flaming: all I can say I still have the motor after about 3 gallons. :weird: :tire: :tire:

Go to any major race & watch the top engine tuners. Notice they never use a temp gun? I have never seem Mario Rossi, Andrea Rossi or Rody Roem use them.

if it "smells" hot and is at a screaming high idle when it comes in...... it's too hot ;)

FWIW....... At both the '06 Nationals and '07 WinterNat's most guy's are pushing 300F with engines these days.

That's like saying that Emeril Lagasse measures ingredients. :sneaky: :lol:

we dont have engines named after ourselves, well... at least I dont. :lol:

Exactly! Most people know when they've pushed the engine too far. :nod:

I am not saying it is not possible to run an engine to that high of a temp and have it survive. I am just saying that it is not good practice.

And if an engine needs to be that hot to run properly then it has some serious design flaws, or more likely the pipe is out of tune until the ex gas temp comes up. Id try different pipes on the suspect engine.

And as I was saying, I haven't used a temp gun to tune for many years now. Does that mean I'm cool and can have an engine named after me?!?
JK!

BK

I've won quite a number of races with my CRF "screaming" at 300F. :sneaky: :lol:

:nod:

Well, now that you mention it, I was wondering how long it would take before the idea crossed your mind. All you have to do is partner up with an engine manufacturer. I would definitely buy and engine you designed! :nod:

a flat 4 with 16 valves? :batman:

Yeah for sure ! lets call it the BK MX1 sounds cool ! lol

Sounds like some new burger from burger king :D

I never use temp guns either. Dont even own one yet. Way I see it, we were tuning race engines long before temp guns came out. What changed since then?

Lol Burger king : )

this folks never have to pay for an engine my friend... they can run it till it blows and call it testing for metal fatigue. this does not apply to me. I pay full price for my RB's (Rody's) and JP's. I run my JP FX21 RO3 at 220-240f for 5min quals and no more than 220 for a 15-20 min main with plenty of power. if you have to run 300f just to get the power you need? well maybe. just maybe you have a wrong kind of engine. you are just too fast for that engine... :nod:

btw : this guys do not use off the shelves engines like you and me.

I agree with tuning for performance and using the temp gun to make sure that you are within a reasonable temp range.