This Will Make One Think Twice Before Winding One Up ! - Chevelle Tech
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post #1 of 23 (permalink) Old Feb 20th, 20, 9:26 AM Thread Starter
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https://www.youtube.com/watch?v=_REQ1PUM0rY
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post #2 of 23 (permalink) Old Feb 20th, 20, 10:37 AM
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Re: This Will Make One Think Twice Before Winding One Up !

That is a neat video! It amazes me to see how fast some of these engines turn.
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post #3 of 23 (permalink) Old Feb 20th, 20, 10:39 AM
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Re: This Will Make One Think Twice Before Winding One Up !

It is a fine balancing act between not enough spring pressure & too much.
Honda was successfully building 12,000 rpm Grand Prix engines in the mid-1960s. I would think the lower the valvetrain mass, the better on such a revver.

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post #4 of 23 (permalink) Old Feb 20th, 20, 11:11 AM
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Re: This Will Make One Think Twice Before Winding One Up !

Quote:
Originally Posted by Cam View Post
It is a fine balancing act between not enough spring pressure & too much.
Honda was successfully building 12,000 rpm Grand Prix engines in the mid-1960s. I would think the lower the valvetrain mass, the better on such a revver.
Like these.

https://www.youtube.com/watch?time_c...ature=emb_logo

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post #5 of 23 (permalink) Old Feb 20th, 20, 11:19 AM
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Re: This Will Make One Think Twice Before Winding One Up !

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Surely! Those tiny sixes don't sound like the 6-cylinder Honda CBX though. I remember a new one back in 1979 with a 6-into1 header on it. I just stopped and listened to the beautiful sound reverberating all over the town of Dundas, Ontario. I also rode a friend's 1980 CBX & loved the sound of the pair of his 3-into-1 headers. Mechanical symphony.


Back to valve float. Float a valve one time and float will occur sooner (lower RPM) next time.
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post #6 of 23 (permalink) Old Feb 20th, 20, 1:11 PM
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Re: This Will Make One Think Twice Before Winding One Up !

12,000 was easy for my Yamaha YDS2. Valves? What valves?
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post #7 of 23 (permalink) Old Feb 20th, 20, 5:47 PM
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Re: This Will Make One Think Twice Before Winding One Up !

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Originally Posted by dyno jonn View Post
12,000 was easy for my Yamaha YDS2. Valves? What valves?
These Hondas were almost 2x that with a whole lotta valves.

Jim

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post #8 of 23 (permalink) Old Feb 20th, 20, 8:48 PM
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Re: This Will Make One Think Twice Before Winding One Up !

.........and you wonder where premature guide wear comes from!

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post #9 of 23 (permalink) Old Feb 21st, 20, 8:17 AM
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Re: This Will Make One Think Twice Before Winding One Up !

At 7200rpm, each valve opens and closes and the plug fires 60 times every second. That means that the plug fires as fast as the fluorescent light in your office. It fires so fast that you can't tell that your light is actually growing brigher/dimmer 60 times every second as you look at it.

Add to that the fact that the retreating piston sucks the cylinder full (aided by the intertia of the whole fuel:air charge) in that amount of time through that ever-changing small orfice baffles my mind. Not just full...in a truly efficient engine, it actually sucks in MORE than will fit at atmospheric pressure.

And some engines turn twice that RPM....

Impossible. This is all just a figment of our imagination - nothing physical can happen that fast, right?


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post #10 of 23 (permalink) Old Feb 21st, 20, 8:27 AM Thread Starter
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Busted....Something to think about !
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post #11 of 23 (permalink) Old Feb 21st, 20, 12:07 PM
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Re: This Will Make One Think Twice Before Winding One Up !

I just did the math backwards from 7200 and I think I twisted myself...
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post #12 of 23 (permalink) Old Feb 21st, 20, 12:43 PM
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Re: This Will Make One Think Twice Before Winding One Up !

Then there's Kawaski's upcoming ZX-25R that redlines at 20,000 rpm.

https://www.motopinas.com/motorcycle...0-000-rpm.html

Boy, if something comes undone at that RPM with so much kinetic energy there is going to be shrapnel across a huge debris field. I'd sure hate that happening between my legs!

With all the dynamic forces at work on an engine, I would imagine at that kind of RPM the reciprocating assembly would distort & stretch (rods etc). How can a valvetrain function at that speed? It must be very direct acting with lightweight components & high valve spring pressures. Still it is mind-boggling.


At the opposite end of the scale, I love my relatively low-revving thumper. The old trials bikes I owned were slow revvers with heavy flywheels so they would not break traction while climbing very steep, tight mountain goat trails (o.k. actually ridges along the Bruce Peninsula).

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post #13 of 23 (permalink) Old Feb 21st, 20, 1:02 PM
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Re: This Will Make One Think Twice Before Winding One Up !

Quote:
Originally Posted by Cam View Post

Then there's Kawaski's upcoming ZX-25R that redlines at 20,000 rpm.

https://www.motopinas.com/motorcycle...0-000-rpm.html

My 25 year old self would be hot for one of those, but traffic conditions and in-attendant drivers would keep my older and wiser self from buying one. I'm sure they would be exciting, what with a 250cc four cylinder having tiny pistons and very short stroke. My Yamaha and Kaw X6 Hustler only had two pistons with longer strokes and still rev'ed to the moon.

Jon N.

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post #14 of 23 (permalink) Old Feb 21st, 20, 5:08 PM
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Re: This Will Make One Think Twice Before Winding One Up !

Modern day MotoGP inline and V4 cylinder engines are all overhead cam, 4 valve, and RPM limited to 18,800 rpms. There is NO comparison from a push rod Chevy to one of them in valve train geometry, valve float, nor operation, as they do not have lifters, push rods, rockers, nor undampened valve springs, and the valve weight is absolutely minimum in comparison.

I know this for a FACT, as one of my other jobs is engine designer for one factory team, there are 5 of us ouside services engineers located all over the world. I have been doing this work since I left working directly for Duntov at Skunk Works, on both two and four stroke engines. This included the older Yamaha 5 valve 4 stroke engines as well, (two exhaust, three intake valves per cylinder), and the Honda 500 and 750 OVAL BORE engines, no round cylinders, they were straight edge oval, and 8 valves per cylinder (4 intake, 4 exhaust).

NONE of the above engines spun with RPM limits less than 18,000 RPM's.

The heavier the valve, the heavier constructed a valve spring has to be, and with that weight, more oscillation, spring issues/problems, outright failure.
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post #15 of 23 (permalink) Old Feb 21st, 20, 5:46 PM Thread Starter
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OHC engine’s are huge ! Look at the size of coyotes

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