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Message started by Eddie Picasso on 09/11/16 at 13:56:26

Title: Hot or cold?
Post by Eddie Picasso on 09/11/16 at 13:56:26

Does a black engine run hotter than say an aluminium lacquered engine, or does it just feel as though it's hotter, due to better radiated heat? Discuss. :-/

Title: Re: Hot or cold?
Post by Armen on 09/11/16 at 14:09:14

One of the misconceptions is that black is hotter. People wear dark clothes in the winter and light ones in the summer because the lighter colors do a worse job of absorbing the sunlight and outside heat. Black does a better job of transferring heat.
So, theoretically, a black engine should run cooler than a silver one, all else being equal. Running motors will always be hotter than the outside air, so black should transfer heat better and run cooler.
Having said that, a lot depends on the type of paint or coating, and how well it was applied.
Honda did a lot of work on the heat transfer characteristics of their silver engine paints when all their street bikes were air-cooled. In the old days, in general, the Japanese aluminum cases were painted and the American and European ones were left as cast.
I always thought that was because of the lower quality of the aluminum that the Japanese used.
It would be hard to beat the heat transfer of raw aluminum with your average rattle-can paint job. Having said that, there are a lot of outfits that specialize in high heat and high heat transfer coatings. Most high performance motors use at least some coatings inside.
Short answer-if you want better heat transfer (better cooling), count on stripping and blasting the castings and doing a thorough job with an appropriate black coating.

Title: Re: Hot or cold?
Post by SavageMan99 on 09/11/16 at 14:25:45

I read a hotrod magazine that claimed a transmission ran 10 degrees cooler with the pan painted black..

Title: Re: Hot or cold?
Post by Armen on 09/11/16 at 14:29:11

I believe it, but as I said, a lot has to do with what kind of paint/coating and how it was applied.
Years ago Circle Track Magazine did a test of all sorts of internal engine coatings and got some impressive results. But, all that stuff was put on professionally.

Title: Re: Hot or cold?
Post by verslagen1 on 09/11/16 at 15:01:03

70435C545F310 wrote:

OMG terminology.
In general, lighter colors do a better job of reflecting all wavelengths of visible light. Black does a better job of irradiating heat.

Having said that, a lot depends on the type of paint or coating, you can have one type of white paint that's better then another type black paint. Do your research before selecting a paint or coating they can vary a lot.

Title: Re: Hot or cold?
Post by Dave on 09/11/16 at 15:01:10

And...the wrong kind of paint can also make things hotter (even black) - if they are not good at transferring heat and are applied too thick.

Title: Re: Hot or cold?
Post by Kris01 on 09/11/16 at 20:00:33

I read an article in an airplane magazine published around '75 or so that dealt with this. The writers had the opinion that certain colors were better than others.

Title: Re: Hot or cold?
Post by norm92de on 09/11/16 at 20:30:34

Personal experience:

I operated an aircraft that had dark blue wings. It was necessary to operate the electric fuel pumps in hot weather - summer in the south US-
because the fuel got too hot This was not a problem except that the fuel pumps were not rated for continuous operation. I replaced a lot of electric fuel pumps that should have lasted many more hours. I was told by the manufacturer that had the wings been painted white the problem would have been much less or non existent. :'(

Don't know if this is relevant.

Title: Re: Hot or cold?
Post by Eddie Picasso on 09/13/16 at 12:05:55

Interesting! The reason I posted this is pretty obvious. My engine was a mess, so I had it blasted and gave it a single brush coat of satin black heat resistance paint. It looks good to me and went on really well. But now when I'm riding, and especially at traffic lights etc, the heat coming off the engine is so bad I have to stick my leg out ( exhaust side ) to keep away from the engine. My initial thoughts were that the engine was running hot, but then thought it must be running cooler if that much heat is being radiated away. I hope I'm right. :-/

Title: Re: Hot or cold?
Post by Dave on 09/13/16 at 12:23:37

Title: Re: Hot or cold?
Post by verslagen1 on 09/13/16 at 12:49:35

Not to discount your 'feelings' but you might get a cheap I/R temperature gauge and compare several points on your engine against others.

Title: Re: Hot or cold?
Post by verslagen1 on 09/13/16 at 14:11:37

I use one of these to monitor oil temp at the front pressure port.

http://www.trailtech.net/media/catalog/product/cache/1/small_image/135x/9df78eab33525d08d6e5fb8d27136e95/b/l/blackTTO_degf_15.jpg
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1361141824

Title: Re: Hot or cold?
Post by MnSpring on 09/13/16 at 16:58:56

This is VERY interesting.

I Always held to the credo, (as verslagen1 said: In general, lighter colors do a better job of reflecting all wavelengths of visible light. Black does a better job of irradiating heat.)

Then, Dave said: “ the wrong kind of paint can also make things hotter (even black) - if they are not good at transferring heat and are applied too thick.”

Sooo with that in mind, (Not Thinking M.C.’s), Would a ’Thick’ Layer, of paint, provide a better, ‘holding’, of the heat?
What kind of paint. (Need to be stable at 750-800 f)

Use, two, ‘cans’, (Old Freon cans), cut off two, one a 1/4” smaller in dia that the other. Coat the outside of the smaller one, and the inside of the larger one, with, a ‘heat’ resistance, (2,000 f), ’goo’, (or stove.pipe packing), which is water biased, For melting 50-70 lbs of old wheel weights, on a 175,000 BTU LP burner. It Works, BUT, it takes at least 10 cycles, of heat, to ‘Just’ about 300f, then the goo in-between, boils, and I have to cool down. Want to make them, so they work. with out having to, wait, 6 months, for it to dry naturally, or waste gas and time, to, speed up, the process. (it may be 1/4 - 1/2” thick at spots.)

I make a ‘pot’ up, (with, Frankenstein ’ bolts), then they disappear. Then later, someone tells me, “Oh They Borrowed it”, and I never get it back. Thinking, the, ‘wrong’ kind of paint, liberally applied, then a piece of, ‘(Heat resilience), rope, around the top, ‘may’ do a better job ? And faster ?

Title: Re: Hot or cold?
Post by Armen on 09/13/16 at 17:38:29

Hey Verslagen,
Can you post a pic of where you put the oil temp sender? I'm prob going to put a temp sender on mine.
thanks,
-Armen

Title: Re: Hot or cold?
Post by Dave on 09/13/16 at 17:48:17

When I had the Trailtech Vapor...I put the temperature sensor on the left rear head stud, just under the nut.

I would get about 240 degrees on cool days of 60 mph riding. On really hot days where temps were over 90 degrees, the temperature would get up to 280......and on a couple of 95 degree days and 70 mph speeds it reached 300 degrees.

Title: Re: Hot or cold?
Post by verslagen1 on 09/13/16 at 18:19:29

0E3D222A214F0 wrote:

Hey Verslagen,
Can you post a pic of where you put the oil temp sender? I'm prob going to put a temp sender on mine.
thanks,
-Armen

use the oil pressure at the forward plug in the case. Get one for a 14mm bolt and just put it on.

http://www.savageriders.com/verslagen/images/Oil%20flow.jpg

730A6A46444C16270 wrote:

The test port plug is a 14mm bolt. Interesting, it's the same thread as many spark plugs. Since I'm not in europe and have a limit selection of metric adapters,

Title: Re: Hot or cold?
Post by justin_o_guy2 on 09/13/16 at 18:40:27

Build one from a plug..

Title: Re: Hot or cold?
Post by Armen on 09/13/16 at 19:17:20

Dave,
You were reading head temp or oil temp?
Sounds like head temp.

Title: Re: Hot or cold?
Post by Armen on 09/13/16 at 19:20:40

Spark plug is 14x1.25mm
Thanks!
I just bought one of the Koso speedo/tach/odo/etc gags. It has a 6 bar fuel gauge, which I can't use and don't need.
The resistance for the scale can be selected from a bunch of ranges. I thought I'd connect an oil temp sender and pick the resistance range that gave me the most useful readings.
In my abundant spare time, of course ::)

Title: Re: Hot or cold?
Post by Dave on 09/14/16 at 08:07:24

23100F070C620 wrote:

Dave,
You were reading head temp or oil temp?
Sounds like head temp.

My gauge was reading head temp.

The sending unit was intended for use on the spark plug - but that is nearly impossible on the Savage, as the plug is down in a hole and there is no room for for the sender to sit between the spark plug and the head. It worked just fine on the cylinder stud, and I used the rear as I felt it got less air flow and most likely would read a bit hotter than the one in front.

Title: Re: Hot or cold?
Post by verslagen1 on 09/14/16 at 09:36:15

0C3F2028234D0 wrote:

The bimetallic temp sensors send voltage.

While I currently use mine as a oil temp gauge, I had another one on the head bolt like dave.

Title: Re: Hot or cold?
Post by Eddie Picasso on 09/15/16 at 12:28:24

Well your thinking most likely is correct....if you are feeling the heat it is not being held in the engine.

Did you change something else....like the muffler or jetting or the air cleaner that may have also contributed to the way the engine may be running? Or did you change your route that requires you to spend more time in traffic? Have you cranked your idle speed up?

Oh yes. I have never ridden a stock Savage. Mine was bought as a barely running heap. So silencer and air filter are non standard. Runs ok but pops a bit when throttling off. Some say this means it's lean, others say it,'s rich and igniting un burnt fuel in the pipe. Another conundrum perhaps. :-/

Title: Re: Hot or cold?
Post by verslagen1 on 09/15/16 at 12:43:00

426F7D7965646E0A0 wrote:

Runs ok but pops a bit when throttling off. Some say this means it's lean, others say it,'s rich and igniting un burnt fuel in the pipe. Another conundrum perhaps. :-/

Shift pop is most likely an exhaust leak, check your header bolts and muff connector.

Title: Re: Hot or cold?
Post by Eddie Picasso on 09/17/16 at 13:34:41

Didn't even think of that. I will check the full exhaust system tomorrow. Could be that it's settled since it's shake down runs.