Installing a high performance cam (camshaft musings pt 3)

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HOTT
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Re: Installing a high performance cam (camshaft musings pt 3)

#16

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robin1731 wrote:
I read it on the internet.......

.
:blast

HOTT (sorry... the stories we could share that start with that phrase :IDTS: )
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Re: Installing a high performance cam (camshaft musings pt 3)

#17

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Thanks Mike great stuff !

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Re: Installing a high performance cam (camshaft musings pt 3)

#18

Post by mikenixon »

77Gowing wrote:On the US Army's Engine NATO certification test, it's a requirement to severely restrict air intake and exhaust gas flow. This makes the engine work very hard. The test requires four 100 hr intervals followed by oil change, then a ten hr performance and fuel mapping.
Test cell temps are held @125deg F.
Engine coolant at 220 Deg F with a static pressure preload to prevent boiling. This 400 hour test simulates 1000 hrs of wear.
Another requirement for our diesels is to run high temperature Jet A fuel. With almost no lubricity. And we are required to use the US Army's oil of which is usually recycled and has lots of ash particulates in it to coke up your injector holes and cause a downward ramp of rated power.
To pass, the engine must complete all test runs and not break or lose any more than 10% of it's original baseline rated power runs.
One thing I observed is the gradual loss of rated power on Detroit Diesel engines. This was due to injector coking during a 2 hr cycle called the up down cycle. 4 minutes no load idle followed by 6 minutes full rated power, run for 2 hrs. This happened on every 10 hour day run cycle for a total of 400 hrs. The engine is worked very hard. To learn about the coking we had to send injectors to Southwest Research to get them scanned via aScanning Electron Microscope to see the nano carbon modules that clogged or cooked the holes.
We ran 100 hp engines all the way up to 3000 hp engines on this cycle. Mostly it was many runs at full rated and runs at full rated torque.
The question you may ask is why what's the purpose?
The Army especially NATO want their trucks and tanks to survive in very difficult desert conditions at full power all day long unceasingly except for maintenance cycle.
Restrictions are set to simulate breathing in and out exhausting through very restrictive anti-balistic grills like on a tank. Ever notice tanks dont have grills mounted on their fronts? Cause that would be an easy target to knock them out of commission. That's why you see inlet air for engine intake and cooling mounted under heavy armor grills facing upward on top of the engine bay.
The vehicles get all kinds of dust thrown at them further making induction and exhaust a serious issue.
But, real world problems on the battlefield.

Blather rant over....uhmm sorry.
Not at all. I think it is interesting. Nothing beats trying things in real world conditions.
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Re: Installing a high performance cam (camshaft musings pt 3)

#19

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rcmatt007 wrote:These threads have had me thinking again about one of the things I see with V twins (and especially on the Morgan 3 wheeler forum), which is the desire to "knock out the baffles" and "take out the cats". To me that just makes a lot of noise without a lot of gain in power. Then there are others who think increasing the ability to get air into the engine is the key.
Yeah, I agree. It's a culture thing. Terry Vance (of the famous Vance and Hines team and later motorcycle business) communicated something every aftermarket exhaust manufacturer would rather keep quiet, when he said, and I quote, "We don't sell performance, we sell fashion", when speaking of the performance exhaust business. Denis Manning, world land speed record holder and owner of Bub Enterprises echoed that when in a phone conversation he described aftermarket exhaust design as more serendipity than science. He said he once had a bike on the dyno with one of his exhausts, developing and testing, and the bike fell off the dyno, banging the pipe, and the motorcycle made more power when he put it back on the dyno. :)

Folks have to have noise as part of their motorcycle experience, many of them, I have concluded. You can't rationalize it, and that's all performance marketing is, rationalization.
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Re: spring dynamics

#20

Post by mikenixon »

mikenixon wrote:There is of course a lot to this subject. But at the outset let me say it's not a practical discussion. The high performance valve spring world includes counterwound springs and inteference springs (an encounter with which has left me extremely disallusioned), both of which are exercises in dynamics, as well as flatwounds, beehive, and more. But you don't see this stuff even in the highest performance production motorcycle engines, not even in Kawasaki's supercharged 325-hp Ninja H2R. Valve springs obviously wiggle and squirm, even rotate, the latter being why aluminum heads require steel spring seats. Ever see a high speed camera video of engine parts moving? Pretty scary. Cylinders jumping up and down, parts oscillating all over the place.

People often talk of valve spring fatigue and Honda must be concerned with it or you would not find spring height measurement in the official manual. But although in the 1960s car world this would have been science fiction, modern engines can sit for decades, obviously with half their valve springs partly and completely compressed, show no ill effect when started afterward, and continue without problems indefinitely. And I think the Japanese were ahead of the game on this. Honda valve springs are very very good, even used in racing and proven superior to all the aftermarket "racing" springs available. In more than 46 years, the only stock Honda valve spring failure I have even heard of was collateral, that is, broken when another part failed.

Not strictly a topic of spring dynamics, the prohibition against installing two-rate valve springs upside-down is in my view the closest the common man comes to playing in the theory realm and applying it practically, that is, to good, real-world effect. Upside-down two-rate valve springs, common on many Honda models, do affect the engine's rpm limit enough to be a concern, because they add to the valve's weight. Again, probably not even this edges into our world, but potentially it can.

One of the things cam makers have to contend with is the lobe finish. Not only does the surface finish determine follower life, it also affects spring longevity. Even at the micron level, a tiny bit of irregularity sets up spring nastiness....

But all of this and a dollar won't be enough to buy a cup of coffee....
Edited to correct statement re counterwound springs.
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