Friday, May 15, 2009

Engine Temperature

I recently read an article in the May Thunder Press by Kip Woodring who writes the Motorhead Memos. This guy knows his shit and does his research. (Note: The last time I looked Thunder Press did not have the May archives posted yet. But I’m sure you can find a copy at your local bike shop.) The article was about spark plugs. The thing that intrigued me about the article was that it was mainly about the advantages of Iridium plugs. I’ve been looking for a set for about 6 months, but didn’t want to pay the $20-$25 a pop for them. The two main reasons I wanted to change the plugs are; 1) the low amount of voltage required to spark these things. Might come in handy with a close to dead battery, or if you still have a generator or kicker. 2) The life span. Some estimates are that Iridium plugs will outlast the engine. I’ll do a update in 20 years to answer that one. A month ago I found a source that got me some for $9 apiece so I got four.

The main part of Kip’s article was the way that a spark plug dissipates heat from your engine, a fact that totally escaped my old brain. I’d try to explain it, but I would recommend that you read his article if that sort of thing interest you. With the stock plugs my 96” in 90-degree heat would run about 250 on the oil and 350 on the rear head. That’s pretty normal for a 96”. Since I was going to Bakersfield where 90 degrees is a cold spell, it was a good time for a test. The Iridium plugs have been in for a month, but it hasn’t been hot enough here to notice a difference. BTW, here’s a good Cross-Reference for Harley spark plugs.

0:dark thirty. 53 degrees. Head south down 101,east over the pass and into the deserts of Bakersfield. 200 miles and the sun is just rising. Perfect, no traffic the whole way. It’s now about 70 degrees. Oil temp never broke 200. Normal op. temp is 230 by HD specs. Go to the business meeting. Blah, blah, blah… frigggin meeting's over, get the hell outta here. It’s now somewhere between 90 and 100 degrees. Perfect weather for my test. I go about 100 miles and stop to check temps. I also stopped so Dave and I could get a cold drink and check out the little restaurant in Cholame that has all the James Dean memorabilia. Yes, Dave made it down there as he mentioned in his last post. Ya know, it’s one thing to drop everything and ride 100 miles when a Brother is down or needs a hand. But 100 miles in the heat just for the company… it’s much appreciated. That’s something few would understand. Thanks. So I check temps: oil 235, a drop of 15-25 degrees from normal. Rear head, 285, a drop of 65 degrees. I should say that I run Lucas synthetic motorcycle oil also. It may be a combination of the two, but the Iridium spark plugs definitely made a difference I could measure. If you can drop a few degrees off you engine temp by swapping spark plugs, it might be worth looking into.

Even though these plugs should last for I have no damn idea how long, there is a reason I bought four for a two cylinder. For one, they’re hard to find and usually need to be ordered in. And reason number two, the important reason; the second set went to a Brother for his birthday.

17 comments:

Baron's Life said...

Well I gotta say...Good on you for giving the second set to a bro on his birthday knowing they are hard to get...hop he appreciated it.
What you say makes sense overall but I wonder if the lower temp will affect the engine long run...better check these things as well before jumping to conclusions... Do you have an IR Laser thermometer?

chessie said...

Baron, I thought on the "too cold" issue as well...bears looking into, but when your riding temps like the Mojave run he just did...sure aint gonna hurt a thing! I believe I will do some reading up on the plugs...sounds interesting indeed!

Willy D said...

Baron: Don’t get me wrong; this is not about running colder plugs. That’s a whole different issue. Iridium simply has a melting point about 1300 degrees F higher than the best Platinum plug. Thus giving it the ability to pull and remove more heat from the combustion chamber while maintaining a very efficient spark. Laser thermometer? Absolutely.

chessie: Riding in the desert was a good test. When you’re talking about temps inside the engine ranging around 400 - 500F, trying to lower them I can only consider a good thing. But do read the article, it’s pretty interesting.

Baron's Life said...

Willy D...I am going to wait and see some test results before I consider switiching..I understand and appreciate your point...but a spark plug only provides a spark...that's it...it has nothing to do with removing or adding heat to the combustion chamber...It is just not physically possible for it to do so. The fact that it would only melt at 1300 degrees means it can withstand higher combustion temps before it melts and busts but it does not mean it will remove heat from it..
Spark plugs never pulled or removed heat from anywhere...they are just spark Plugs...a Ligther if you will... They tricked you on this one...

Willy D said...

Baron: All parts of a engine transfer heat from the inside to the atmosphere, that’s just the physics work, nothing we can do about it. That includes spark plugs. Most estimates are that about 20% of the heat generated by combustion is absorbed by the spark plug. Ever touch a spark plug on a hot engine? Science in action. That heat’s coming from somewhere. I assume it’s coming from the combustion chamber. As always, don’t take my word for it, do your own research.

mq01 said...

hmmm...very interesting... i ride the desert, rockies, and plains most of the dry season myself... im gonna watch temps more closely now. thank you.

Ann said...

Once Annabelle is running again, I'll bet Big D asks you where you found these plugs. :)

Mr. Motorcycle said...

I looked at the conversion charts. I saw on the left side bar that you can order NGK Iridium's from there.
Is this where you found them for $9.00 a pop?

Do share.

I'd be interested in trying them.

Thanks for the post.

FLHX_Dave said...

Thanks WillyD. You are a brother for sure. I consider you family.

Thanks for the B-Day present. Well, with the AMSOIL and the plugs you gave me, I have noticed a change in idle at high temps. Much better. This last 90+ heatwave really proved the point.

I don't believe everything I read but I do know when something has affected my bike. This definately made a positive change.

Correct me here. If the plugs take less power to jump the gap, then there is less resistence, thus creating less heat...which in turn would make the plug cooler, thus able to absorb more heat to dissapate throught the jugg? Now that's just my thinking based on what I know. Am I on crack or is this sound common sense.

Willy D said...

Mr. M: That link was “only” for the chart. I got mine from a small local shop.

Dave: Well… in around about way. Removing any heat you can is the goal, however you get there.

"Joker" said...

I'm going to look into this as well. It would seem that keeping the temps down would be the way to go. The point about the engine maybe running too cold is valid too though. I don't know enough about it on my own, but this is motivation for some research. If nothing else, using plugs that will lower temps on a long haul to Sturgis may be a big help for both comfort and engine wear. It's not like you can't pop the stock ones back in for Spring/Fall local rides when it's cooler out.

Thanks Willy....you da man!

Willy D said...

“Joker”: This is not about a different heat range plug, that’s a whole different subject. They are made of better materials that transfer heat better, provide a better spark and are very resistant to corrosion / tip wear. Heat range on the ones I’m using is the same as OEM.

Baron's Life said...

Sorry guy...none of this is scientific fact...!

Baron's Life said...

Not sure where you learned your Doctoring from...whole lot of Hog Wash on the spark plug deal.... Sorry no can do to swallow this one ! Even if it were so how much heat would be transferred from a spark plug... There just is no mass there to transfer anything significant...better go back to MED School Doc.

Willy D said...

Baron: http://www.ngksparkplugs.com/techinfo/spark_plugs/techtips.asp?nav=31000&country=US

Baron's Life said...

Ok you gotta a point there...Corrected I stand..

Willy D said...

Baron: Harleys have always had a issue with heat. Anything you can do to cool them even a few degrees is a good thing. That’s the only point I was trying to make.