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Old 11-13-2010, 04:54 AM   #1
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Default Can you be lean but not hot?

Hi there, i am slowly learning more and more about tuning engines.... and the more i read the more i question stuff!

My Head bone has me now contemplating this .....

Can an engine be too lean but not be hot?

My head bone says yes!!

I have a Ninja motor (MR12 TO1A) and I have read that this motor is happy running a bit hotter than your average motor with say 100-110c as an average.

It also has a massive heat sink head and when i run it on what i think is a good setting (maybe still a slight bit rich) the temps never really get much past 100c.
I figure i might have to run a hotter plug to have the motor run a bit hotter.

I was also reading about a fuel that made the motor run a fair bit cooler and it got me thinking if you had that and were trying to get it hotter on the same plug by leaning it off you could hit a problem of going too lean and still not getting hot.

I guess this is why a lot of people say dont tune to the temp gauge!

My head also says its not the heat that bugger a motor but the lack of lubricant so running leaner to just get temps up isnt the best idea~

I am probably just thinking out loud, but i thought id throw it out there for others to comment.

So what do you reckon?
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Old 11-13-2010, 06:19 AM   #2
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You may have read this, but I will say this again:
Dont tune your engine to a specific temperature, go by the sight of blue smoke coming out of the pipe at full throttle and the way it sounds. Sometimes you need it a little rich depending on your track, sometimes not. But if you seem to be running rich and its still getting too hot, maybe its the LSN being too lean. Different fuels also make engines run at different temperatures, it just depends on what blend you like and how the engine performs.
I made the switch from Nitro-X to ATS fuels, same percentages, and I like ATS better - more runtime, better tuning and its cheaper.
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Old 11-13-2010, 06:26 AM   #3
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Yes they can be lean and still cool. I had a motor that was only coming off at 190 after 10 min. That's really cold for an onroad .21 so leaned it just a hair more for the next qualifier. All it did was pick up a massive lean bog and no increase in temps.
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Old 11-13-2010, 07:19 AM   #4
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A lot of heat does not even come from the combustion but from parts with friction. A P/S set with a lot of pinch can heat up an engine with an extra 5 up to 10 degrees celcius as also a bad rod, bad bearings or bearings placed out of line.

Then there is the exhaust. the differens between a good and a bad exhaust can heat up an engine with an extra 30 degrees celcius.

Sadly the materials inside can stand certain temperatures, if they become to hot they will loose their strength, we have seen piston materials becomming weak/soft at an engine temp of 130 degrees but 130 is a common operating temp.....
So yes, giving an extra cooling can mean that you can go lean without overheating the materials and lubrication not to forget. A nice example is this topic:
http://www.rctech.net/forum/onroad-n...s-illegal.html
Novarossi did have some issues with pistons going bad at the exhaust side, the piston suddenly shows a rough surface at the side caused by heat and a bad lubrication, they did solve it with some small posts using mixtrure to lubricate and cool down.

An extra cooling can be found in special heads or combustion chambers like the Picco .21 EVO 4 models or the old Sirio WCR2003 integral sleeve. Our USE engine does have the AAC integral sleeve and when the engine is perfecly runned in the operating temp is about 80 up to 90 degrees celcius and so running much cooler than normal ABC engines.

Can you go to lean?
Yes! The right mixture is giving the best combustion, going beyond that will loose power, lubrication and will mash up the ignition timing. You can see it in the smoke and also in the sound of the rpm, the engine does scream it out if he does not like the lean setting, if the setting is right it talks with a nice constant tone in where you can hear the high rpm and the slightly deep rich tone at once, that deep tone is gone when you go to lean making the engine yelling it out from the pain it has.
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Old 11-13-2010, 07:27 AM   #5
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ROCK DJ, wise words right there.... interesting you mention the ATS fuel as i am thinking of switching to that soon once i can locate some.


WIngracer.... this massive lean bog you speak of has me intrigued .... perhaps that's what i had after i started trying to lean mine off the other week.

Iv'e experienced the choking chicken where the motor is just starving for fuel and wont rev too hard without dying.....

But the other one seemed to come toward the end of a tank ... it was like the brake came on .... a quick beerrr beeerrrrrr berr stop!
Perhaps that was the dreaded lean bog..... or my loose brake shoe did get into a bind.
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Old 11-13-2010, 07:40 AM   #6
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I have a Pico Evo 3 in a Mugen MRX4X that will not go over 190 degrees.
Runs great at that temp, but I did try and lean it out a little, and it leaned bogged so bad, it barely made it back to the pits before it starved itself for lack of fuel. I richened it back up about 1 hour, and the engine runs great, still coming in under 200 degrees. Engine has to have close to 2 gallons of fuel through it already, but it is just a quick now as it was when I broke in the enigne. I have owned many Pico engines, and they usually ran around 225 to 230 degrees, but not this one.Even after running in a main, I can check the temp, and it does not vary more than 5 to 10 degrees, even on hot summer days. But it will not run if I lean it out even 1 hour.
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Old 11-13-2010, 09:37 AM   #7
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plus temps guns not accurate too
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Old 11-15-2010, 05:46 PM   #8
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Quote:
Originally Posted by NitoriousRC View Post
ROCK DJ, wise words right there.... interesting you mention the ATS fuel as i am thinking of switching to that soon once i can locate some.

But the other one seemed to come toward the end of a tank ... it was like the brake came on .... a quick beerrr beeerrrrrr berr stop!
Perhaps that was the dreaded lean bog..... or my loose brake shoe did get into a bind.
Im not sure if there is a brand of fuel named ATS fuel or not, but I only just realised I use AT Racing nitro, not ATS

Usually if what you described happens near the end of the tank, that because the fuel left in the tank would pull the fuel from the fuel line, since it can move around more than when the tank is half-full. Normal, but annoying. Try making a loop in the fuel line so it doesn't happen, or minimizes the effect.
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Old 11-15-2010, 08:34 PM   #9
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Tuning by smoke can be a bit tricky as well as you need to "learn" the fuel you run.

Byrons 12% lube smokes quite a bit
Byrons 9% lube smokes less
Losi Nitrotane (what I use) smokes very little.

I would always use a combination of smoke and temps with the engine performance as well. Within certain limitations, the temp is not that important, but what is important is if the temps rise continuously.
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Old 11-15-2010, 11:02 PM   #10
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Once my engine has perfect needle setting from previous races.

I usually turn HSN anti-clockwise 1 or 2 hour before playing.

After that, my pitman and I go to track and we start retuning for that day.

Thats it.






( I live in tropical country with high humidity, hot climate and near sea level, SO for my own recipe : 120C is maximum limit for novarossi engines, and 108C is max limit for OS engine )
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Old 11-16-2010, 12:43 AM   #11
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True Scott, I feel that by tuning only looking at smoke does limit how much you can do, that's why I have a temp gun to get an idea of where Im at, even if it is inaccurate. One question though:
Is it possible to have the HSN too rich but have the LSN too lean making it seem as if the top is fine? A fellow racer I know can go 2 laps or so before a 5 min race, and still finish with a quarter to half a tank left (its a small track, he isn't running WAAAY too lean.) whereas I only finish with about 30 sec to a minute worth of driving. I figured yesterday I was in the "too closed, too lean" situation, so is it possible a lean LSN gave me a false correct HSN tune?
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Old 11-16-2010, 02:52 AM   #12
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Quote:
Originally Posted by DJ_Shakespear View Post
True Scott, I feel that by tuning only looking at smoke does limit how much you can do, that's why I have a temp gun to get an idea of where Im at, even if it is inaccurate. One question though:
Is it possible to have the HSN too rich but have the LSN too lean making it seem as if the top is fine? A fellow racer I know can go 2 laps or so before a 5 min race, and still finish with a quarter to half a tank left (its a small track, he isn't running WAAAY too lean.) whereas I only finish with about 30 sec to a minute worth of driving. I figured yesterday I was in the "too closed, too lean" situation, so is it possible a lean LSN gave me a false correct HSN tune?
I would honestly say no.. The high speed needle setting is much more critical than the low. If the HSN is too rich the engine wont make good power and it will use a lot of fuel. Its way more common to see people with too lean on the HSN and too rich on the LSN.
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Old 11-16-2010, 03:31 AM   #13
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Difficult to say, with a rich LSN people are tuning the HSN so it will reach the better topspeed on the straight and still accelerating good enough. Depending on how fast you go onto the straight it will lean out while accelerating and at the end it will go (to) lean.

With a good LSN the HSN is better to adjust because the engine is much faster on top speed giving a better information how it is running on top rpm and so a much easyer find of the HSN setting.

I would almost say the LSN is more important, for sure for faster laptimes. And at the end both needles are important.
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Old 11-16-2010, 09:38 AM   #14
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I'm sure we have confused him now.
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Old 11-16-2010, 02:55 PM   #15
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Nope, not confused!

I have read before about a false lean .... i forget where i read about it but it was an interesting concept.

Basically yeah, a really rich bottom end helping to mask a really lean top end.

I often wonder about the relation of the two needles, and how they work together ... but i now tend to treat them as two seperate beast ... one for the idle... and one for the top end.

This has been an interesting discussion for my head bone!

Now what about the dreaded 3rd needle, my mate has been looking for the settings for the 3rd needle for his Sirrio .12 Evo4. I have the same motor and the needles seem to be set different. (both second hand motors)
I read some interesting stuff once how it changes where the powerband is at.

Also DJ, yeah i often say ATS fuel too ... getting AT racing fuel confused with ATS Tyres!
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