Pre Heating Engine
10-01-2010 | 07:39 PM
#91
Tech Adept
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does cold 4 strokes have more to do with Cooler air after running through cold motor(more dense not getting heated by blowers and manifolds), Colder Fuel (more dense/more power per Oz). But isnt starting a Cold 4 stroke where most of the damage is done?
anyhow im done I preheat my engine some ppl dont. end of story.
anyhow im done I preheat my engine some ppl dont. end of story.
10-02-2010 | 01:17 PM
#92
Tech Regular
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Serious question here. With no glow plug my Reedy turns over easily by hand, and with the glow plug in I of course get compression that makes it harder to turn over.
So I must ask, if there's no pinch restricting the piston, why does my engine turn over on the box easier after heating it?
So I must ask, if there's no pinch restricting the piston, why does my engine turn over on the box easier after heating it?
10-02-2010 | 01:34 PM
#93
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Serious question here. With no glow plug my Reedy turns over easily by hand, and with the glow plug in I of course get compression that makes it harder to turn over.
So I must ask, if there's no pinch restricting the piston, why does my engine turn over on the box easier after heating it?
So I must ask, if there's no pinch restricting the piston, why does my engine turn over on the box easier after heating it?
I'm not saying preheating is good or bad, just wondering why everyone claims it is needed for longevity. If the motor NEEDS to be heated to reduce/eliminate damage when new, the pinch is too tight and the engine shouldn't have passed QC checks at the factory...IMHO. The Pinch is needed to produce compression due to the sleeve expanding more than the piston at operating temps. The "pinch" is more noticeable when new because the sleeve and piston must wear together, making a sealing surface.
I can see heating reducing the "felt" pinch, but I look at like breaking in a new dirt bile motor..Without a load placed upon the new piston and rings, it won't seal correctly and you'll have problems down the road. I know an ABC engine doesn't have rings, but the theory is the same...Without a load placed on the piston,. it won't wear in correctly.
Again, my opinion and worth what you paid.
10-02-2010 | 02:00 PM
#94
Tolerances open up on sleeve/piston fit from expansion and any oil/grease in bearings flows easier.
I'm not saying preheating is good or bad, just wondering why everyone claims it is needed for longevity. If the motor NEEDS to be heated to reduce/eliminate damage when new, the pinch is too tight and the engine shouldn't have passed QC checks at the factory...IMHO. The Pinch is needed to produce compression due to the sleeve expanding more than the piston at operating temps. The "pinch" is more noticeable when new because the sleeve and piston must wear together, making a sealing surface.
I can see heating reducing the "felt" pinch, but I look at like breaking in a new dirt bile motor..Without a load placed upon the new piston and rings, it won't seal correctly and you'll have problems down the road. I know an ABC engine doesn't have rings, but the theory is the same...Without a load placed on the piston,. it won't wear in correctly.
Again, my opinion and worth what you paid.
I'm not saying preheating is good or bad, just wondering why everyone claims it is needed for longevity. If the motor NEEDS to be heated to reduce/eliminate damage when new, the pinch is too tight and the engine shouldn't have passed QC checks at the factory...IMHO. The Pinch is needed to produce compression due to the sleeve expanding more than the piston at operating temps. The "pinch" is more noticeable when new because the sleeve and piston must wear together, making a sealing surface.
I can see heating reducing the "felt" pinch, but I look at like breaking in a new dirt bile motor..Without a load placed upon the new piston and rings, it won't seal correctly and you'll have problems down the road. I know an ABC engine doesn't have rings, but the theory is the same...Without a load placed on the piston,. it won't wear in correctly.
Again, my opinion and worth what you paid.
10-02-2010 | 02:04 PM
#95
Tech Initiate
Joined: Apr 2010
Posts: 30
If you could saturate the entire engine without running it, yes. Too bad a heater will leave the head hot, the block warm, and the crank and conrod cold.
Heat dissipates from a larger concentration to a lessor one. Heat is also transmitted by convection, radiation or conduction. convection and radiation heat the engine with a "bulb" type or heat gun type heater. Conduction by a wrap type. This heat travels from the outside into the motor. Because the sleeve is in contact with the block, it starts to heat after the block. then piston and crank(through the bearings) and finally conrod.
I'm talking ANY Heli motor. I have NEVER seen an air guy preheat ANYTHING but a cup of Irish coffee.
Only car guys preheat engines. Air guys just start them and run them...
Like I do, have done for 20 years and still do. I have running engines from companies not even in business anymore. Very Early ABC engines. Like from 1981.
And to answer your question, any race team interested in instant raw power do NOT preheat engines...IE Any Top Fuel engine. Longer time at the line heating engine=less power is made from that engine. Old bracket racer trick. Stage late to make the other guy gain a few * in engine temp and produce a tiny bit less power.
Heat dissipates from a larger concentration to a lessor one. Heat is also transmitted by convection, radiation or conduction. convection and radiation heat the engine with a "bulb" type or heat gun type heater. Conduction by a wrap type. This heat travels from the outside into the motor. Because the sleeve is in contact with the block, it starts to heat after the block. then piston and crank(through the bearings) and finally conrod.
I'm talking ANY Heli motor. I have NEVER seen an air guy preheat ANYTHING but a cup of Irish coffee.
Only car guys preheat engines. Air guys just start them and run them...
Like I do, have done for 20 years and still do. I have running engines from companies not even in business anymore. Very Early ABC engines. Like from 1981.
And to answer your question, any race team interested in instant raw power do NOT preheat engines...IE Any Top Fuel engine. Longer time at the line heating engine=less power is made from that engine. Old bracket racer trick. Stage late to make the other guy gain a few * in engine temp and produce a tiny bit less power.
Some which will run 1-2 gallons on a race. so they will compare the amount of gallons they get on a motor and not time.
I think air guys are not running tank after tank without shutting down the engine, they mostly fly 1 tank stop flying sit around with others talk/warm up their coffee, drink beer lol and have fun. Some may jump out and fly more then others but some dont, it is a little different then cars because when u are driving at a long period and get tired they keep going, if the crash no big deal, with the heli/air you get tired and mess up u crash "Big deal".
Now with preheat it is all to do with abc motors and ringed motor are not as critical for this method, but would not hurt to do it!
10-02-2010 | 05:06 PM
#96
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Well i could be wrong here but to answer ur ?, All of the heli/air motors are ringed and that is why the preheating is not done. Now if there are any that are abc motors for them and you are getting many years of use out of the, the only explanation that i can think of that is different from car guys is, car guys run consistence tanks at a time, for example a car guy will run 1-2 gallons practicing, 20 - 45min at a time, then on race day pratice/qual/main.
Some which will run 1-2 gallons on a race. so they will compare the amount of gallons they get on a motor and not time.
I think air guys are not running tank after tank without shutting down the engine, they mostly fly 1 tank stop flying sit around with others talk/warm up their coffee, drink beer lol and have fun. Some may jump out and fly more then others but some dont, it is a little different then cars because when u are driving at a long period and get tired they keep going, if the crash no big deal, with the heli/air you get tired and mess up u crash "Big deal".
Now with preheat it is all to do with abc motors and ringed motor are not as critical for this method, but would not hurt to do it!
Some which will run 1-2 gallons on a race. so they will compare the amount of gallons they get on a motor and not time.
I think air guys are not running tank after tank without shutting down the engine, they mostly fly 1 tank stop flying sit around with others talk/warm up their coffee, drink beer lol and have fun. Some may jump out and fly more then others but some dont, it is a little different then cars because when u are driving at a long period and get tired they keep going, if the crash no big deal, with the heli/air you get tired and mess up u crash "Big deal".
Now with preheat it is all to do with abc motors and ringed motor are not as critical for this method, but would not hurt to do it!
Maybe motors have changed in the last 10-15 years, but I haven't seen any degradation of performance in my engines by not preheating.
01-20-2012 | 07:22 PM
#98
Tech Addict
Joined: Dec 2007
Posts: 543
From: Brandon, MS
Not a good comparison, air to surface engines. Air engines spend most of their life at less than 12,000 rpm's. They operate in a loaded condition. Most flyers don't use high percentage nitro. Engines are toleranced for higher oil levels. Need I go on? Ever here of the Saito 100 gallon club? To get in it you have to run your engine for over 100 gallons just like the club name states. Try that with ANY surface engine.
as far as the heater not getting the crankshaft, rod and wrist pin hot......... when the bottom of the chassis is hot, the rest of it is hot also.
Dragsters run without preheating for max power, plus look at the rebuild frequency. Nascar on the other hand hates cranking a cold engine, especially a used cold engine. Ever see a crew cheif cross his fingers hoping the engine is fine after a long red flag?
as far as the heater not getting the crankshaft, rod and wrist pin hot......... when the bottom of the chassis is hot, the rest of it is hot also.
Dragsters run without preheating for max power, plus look at the rebuild frequency. Nascar on the other hand hates cranking a cold engine, especially a used cold engine. Ever see a crew cheif cross his fingers hoping the engine is fine after a long red flag?
01-20-2012 | 07:57 PM
#99
Not a good comparison, air to surface engines. Air engines spend most of their life at less than 12,000 rpm's. They operate in a loaded condition. Most flyers don't use high percentage nitro. Engines are toleranced for higher oil levels. Need I go on? Ever here of the Saito 100 gallon club? To get in it you have to run your engine for over 100 gallons just like the club name states. Try that with ANY surface engine.
as far as the heater not getting the crankshaft, rod and wrist pin hot......... when the bottom of the chassis is hot, the rest of it is hot also.
Dragsters run without preheating for max power, plus look at the rebuild frequency. Nascar on the other hand hates cranking a cold engine, especially a used cold engine. Ever see a crew cheif cross his fingers hoping the engine is fine after a long red flag?
as far as the heater not getting the crankshaft, rod and wrist pin hot......... when the bottom of the chassis is hot, the rest of it is hot also.
Dragsters run without preheating for max power, plus look at the rebuild frequency. Nascar on the other hand hates cranking a cold engine, especially a used cold engine. Ever see a crew cheif cross his fingers hoping the engine is fine after a long red flag?
All so when i run Late Models it was the same way we Crossed are fingers each time we started the motor after a Long Stop and the motor cooled down and we could not get back to the Pits to hook up the Block heaters.
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