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Nitro engine temp check... when? how?

Old 04-03-2015, 07:24 PM
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Fuelman
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I take it you are an old timer like me in the RC sports?
Old 04-03-2015, 07:36 PM
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xRuddyx
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Well im old as far as these guys on the forum goes i raced the original rc10 in 1983 and won a lot of trophies with that car. Everyone looked on that car in awe lol. Time has gone by and I've gotten myself back into the hobby. I own both nitro and lipo cars but being a tinkerer i just love tuning the nitros. Nice meeting your acquaintance fuelman.
Old 04-03-2015, 07:38 PM
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Fuelman
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Likwise, yes, we've both been around a long time......
Old 04-03-2015, 07:43 PM
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nitroexpress
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Talking about engine temps. Did you know that there is only one temp gun on the market that does not use emission to readout temps. Emission reading guns (which are 99% of those available) can give different readings depending on cooling head color and porosity The Exergen Precision Infra Red Temperature Gun is expensive and not needed by most, but it's the king.

Anyone calibrate your temp guns? Many guns have a calibrate mode. It's not just a useless doodad. Also, a dirty lens can throw off readings significantly.

That being said, tuning to performance and not strictly temperature is the way to go. Also, I have seen many discussions involving engine distributors, engine modders and many racers involving tuning. Never once have I seen anyone condone running a road going nitro engine at or around 350 degrees. Sorry Fuelman. I agree with much, if not most, of what you have posted over the years. But not on this.
Old 04-06-2015, 06:03 AM
  #30  
1QwkSport2.5r
 
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While I do agree the engine should be tuned to run properly by ear/feel, there is a limit I feel. I run my engines hard, but I try to keep the head temp below 310F. I find getting the engine warmed up as quickly as possible and adjust to max power with a full tank of fuel, then back off about 1/4 turn. I like to set my idle/midrange mixture a touch rich - just so it is just barely loaded up after a 20-25 second idle. Having both needles just a touch rich on a full tank ensures the mixture doesn't get too lean at the bottom of the tank and prevent temperature spikes. I find 10-12% oil content in the fuel is good for bashing - less than 10% oil seems to be a bit dry for my liking.
Old 04-06-2015, 03:20 PM
  #31  
nitroexpress
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The highest recommended temps that I have ever seen have been for engines using a high silicon piston. This would be indicated by the piston having a speckled appearance. Alpha engines and their clones have this feature. Even then max temps are 270 - 280 Engines at the Traxxas level of quality need not apply.

In regards to oil percentage, it all depends on the quality of the oil package. For more performance, the oil percentage needs to be low. But without a good oil package, engine damage can occur.
Old 04-08-2015, 11:16 AM
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jkdv8
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Quality fuel is key. I switched to byrons Gen 2 awhile back (after running originals) and made a huge difference in temps and performance. Think it is 12% oil and 20% nitro. Feel it is the best of both worlds but, you don't have to take my word for it.

Also used the spit test in the past. Used that in correlation with telemetry, and a temp gun to keep an eye on things.

Last edited by jkdv8; 04-08-2015 at 11:19 AM.
Old 04-08-2015, 03:57 PM
  #33  
nitroexpress
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350 is not too hot when the tune is correct.
Yes, but a temp of 350 indicates the tune is not correct.
Look at an airplane engine, the head has much less cooling fin surface area, and generally they run a lot hotter, even in the prop blast.
How can you be sure? Anyone accurately temp a running/flying airplane engine?
Most of your average ABC /ABN airplane engines last years of heavy use.
That’s with a steady throlttle and no dirt to contend with.
Your average car engine has an oversized cooling heat sink head, in most cases it is way too much and makes them run way too cool, even when they are not run too rich. Your average car engine piston and sleeve lasts a season or less.
I’ve seen this assertion from you before, but it obviously the manufacturers don’t agree.
In an ABC engine (car, plane, does not matter) the piston is in a tapered sleeve. The top of the sleeve is actually smaller than the piston at room tempreture (thats where the pinch comes from). At operating tempreture (around 230 degrees F or greater ) the brass sleeve begins to expand to design fit and becomes about the same diameter as the piston. Any time an ABC type engine is run too cool for extended periods of time, the top of the aluminum piston is actually wearing away and becoming tapered so it fits in the cold sleeve. The engine may run great for a couple minutes until it gets warm then sags off and dies. When you have too much cooling fin surface area and the engine can not sustain design temps when correctly tuned, accelerated wear of the engine is the result.
All true, but the expansion begins starts happening below operating temperature.
An ABC engine will not be harmed by tempretures of 350 or 400 degrees F when the mixture is not lean. Some engines , where the stock cooling heads that are not oversized, like the Fantom 18, a correctly tuned engine is gong to run over 300 on a cool day and a lot warmer on a hot day, and it will run that way for gallon after gallon after gallon. On other engines, in order to get them to run better, I must block off a couple cooling fins by wraping tin foil around them, so they do not dissipate the heat too fast. Interresting, but Fantom doesn’t seem to recommend temps over 290, even on hot days. http://www.rctech.net/forum/monster-...ine-bible.html
Who is Ryan Lutz and why trust him? I can assure you, this tuned engine is not runing 300 degrees or over (and is used a high silicon piston).

https://www.youtube.com/watch?v=kZ5BsceGVbo
but on the other hand these engines parts will stand under 350 conditions if it has proper lube anyways how could an engine go up to 340-350 range with proper lube[X(] Proper lube and tempreture do not have the relationship you think it does. Methanol in the fuel does the majority of the cooling, followed by the nitromethane. The oil provides little if any cooling factor and is there strictly to maintain a protective barier between moving parts. Methanol will suck the heat out of an engine just due to the latent heat of vaporization of methanol (which is very high), as the fuel vaporizes in the crankcase. Oil on the other hand does not vaporize and never becomes a gas, it atomizes into tiny droplets, some of which coat the internal parts of the engine but most of it flows with the vaporized methanol and nitromethane into the combustion chamber. In the combustion chamber, gasses (methanol and nitro) can be compressed, liquids (oil) can not be compressed. the more oil you put into a fuel, the greater the increased compression factor exists in the combustion chamber, causing operation tempretures to rise due to an increase in relative compression.
Yes Yes, but the quality of the lube package enaters into the equation. One cannot equate the quality of a Traxxas fuel with, let’s say, Werks or Byron’s.
For instance, I was test running a Fantom 18 on a very warm and humid day (about 90 F and 70% RH), using standard 20% car fuel. The consistent temps were about 325 to 350 when correctly tuned for the day. To prove the point to a fellow racer who argued that 350 was way too hot and said that I need to run more oil (I tried to explain the relationship, but he did'nt get it), I got out some of my 20% airplane fuel which had 20% oil in it. After retuning to the new fuel and making a tank worth of fast laps, I pulled in and let him measure the temp. His jaw droped when he saw it was running between 405 and 415. I continued to run the engine on that fuel for several more tanks. That Fantom 18 still has awsome compression, even after well over 10 gallons through it (probably close to 20 by now), it has never been apart. I see what your saying, but you’re exceeding Fantom recommendations. I’m just not buying that a good tune can be had at 300 and above temps.
Again; higher temps when the engine is not lean will not hurt a darn thing. I just don’t agree with your defination of higher temps. Too many engine guru’s (not directly connected to a factory) disagree. Elevated temps due to it being too lean will hurt the engine. True. Running an engine too cool will destroy the piston and sleeve fit faster than anything. Many bashers run their engines too cool. Thus reducing the lifespan of their engines. Running too cool during break in increases rod wear and sometimes causes rod breakage (hello Traxxas).

Last edited by nitroexpress; 04-08-2015 at 04:03 PM.
Old 05-06-2020, 12:29 PM
  #34  
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There are many good points raised here. I think too many people buy a temp gun and attempt to 'tune' their engine to a target temperature. During the process, they ignore their own senses.

Long before people could source a temp gun, people enjoyed nitro engines - tuning was done by ear, eye & nose.

Some engines run right at higher temps, others lower. Just ensure it sounds right, responds properly and leaves a misty smoke trail on full throttle.

I say this after running and tuning my STS .30 today, using an O.S. carb, and it was in the sweet spot running 286F, which some might tell you is a little high. But for this engine, on this fuel, on this day - it was spot on.

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