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post #1 of 6 (permalink) Old 07-18-2010, 05:36 PM Thread Starter
lee
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Heat

Let's talk about engine heat. It seems to be a popular topic around here. Coolant temp and engine temp are not the same. Coolant temp is an indication, if you will, of the engine temp and not the really critical figure even though it's all we've got.

Engines are designed to operate at optimum efficiency and produce maximum power in a certain temp range and by that I mean the temp of the internal components such as pistons, rings, valve stems and guides, bearings etc. The stuff that moves.

Take the piston. It is designed to have a cyl wall clearance of X when cold and Y when hot. Y is the important figure as the piston will expand as it gets hot, decreasing the clearance between itself and the cyl wall thereby promoting a better seal and less slop which leads to premature wear. In the day piston material was such that it expanded quite a bit and a cold engine would experience something refered to as "piston slap" which was the cold piston slamming against the thrust side of the cylinder on the compression stroke until it expanded and was at proper clearance. Alloys now are such that engines run frightenly small clearances.

Piston rings have a certain "gap" range on the ends to allow for growth as they heat up and ideally end up with 1 or 2 thou clearance when hot to better seal the pressure. They also have "side gap" in the ring lands on the piston for the same reason.

Valve stem to guide clearance is another critical item and is designed to be just enough when hot to allow the valve to get lubed and be able to move without binding.

And let's not forget about detonation. Anyone ever experience that when the coolant's reading 225? Course I guess the ECU takes care of that critter. Assuming all the components are functioning. Thank God for guys like Noel. He loves electronics and were it not for guys like him we'd be in deep stuff without it. Go Knurl!

The whole point is that it's the temp of the engine and it's goodies that's important. If the coolant reads 225F well yeah that's pretty hot but what are the clearances in the engine at that temp? A better indication would be engine or cyl head temp. I use cyl head temp gauges on my air cooled bikes and regularly see temps of 275F and on occassion have seen 300-310. That's taken from a sensor in the head next to the exhaust ports. Those engines have pretty tight clearances and at those temps have never had a problem. Other than to fry my crotch and legs. Gotta' quit this riding in shorts and a tank top shit. The flip flops are killing my left big toe too.

Anybody know what the cyl head temp range is on an MV? Betcha it's up there.

Man, I gotta' get a friggin' life here.
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post #2 of 6 (permalink) Old 07-18-2010, 05:53 PM
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LEE- didn't you said, You have lost interest in bikes ??? ( or something like that in your tri color Duc. for sale add !!!) maybe you should consider to turn your Duc. into an ultralight

Last edited by Nicolino; 07-18-2010 at 05:58 PM.
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post #3 of 6 (permalink) Old 07-18-2010, 05:57 PM Thread Starter
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Yes I did say that but I can still share my ignorance now and then.
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post #4 of 6 (permalink) Old 07-18-2010, 06:01 PM
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Absolutly , and We the forum members will be happy to read your contributions !!! (except Randy of course)
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post #5 of 6 (permalink) Old 07-18-2010, 09:42 PM
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Quote:
Originally Posted by lee View Post
Gotta' quit this riding in shorts and a tank top shit. The flip flops are killing my left big toe too.

Man, I gotta' get a friggin' life here.

Hey LEE!!

The last picture I saw of you on an MV there were no tank tops or shorts to be seen.....

As for a life, I do believe you"ve got a pretty good one going. How's that very tolerant lady that you live with doing? Heading to Bubba II? The HEAT there should be intellectual...

Gapalicious 2020 at
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post #6 of 6 (permalink) Old 07-19-2010, 11:59 AM Thread Starter
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Yeah we'll be there. Wouldn't miss it for the world. Or that good looking babe daughter of his.
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