Harder Quiz

If I'm not mistaken Larry, that's the engine currently in your personal bike?

larrycavan wrote:

T_Dub wrote:

I wouldn't say final exam Dave, but that'd be an average midterm in engineering fluid dynamics haha.

My main question Larry, is what are the equations that you use to identify these things? I suppose mean air speed would have to do with actually filling the cylinder in the time allotted(duration of cam as a fraction of a cycle, divide that by revs to get time). But my main thing would be valve size. What correlation are you using to determine required valve size at a certain lift to get the required flow rate?

I use feet per second at 28" steady state for mean air speed.

Valve size is a variable for flow and clearance reasons.

Well thats a different story. You're using test bench measures. I was trying to calculate actual steady state values at 9000RPM on a running engine!

you guys are making my head hurt! :woohoo:

T_Dub wrote:

larrycavan wrote:

T_Dub wrote:

I wouldn't say final exam Dave, but that'd be an average midterm in engineering fluid dynamics haha.

My main question Larry, is what are the equations that you use to identify these things? I suppose mean air speed would have to do with actually filling the cylinder in the time allotted(duration of cam as a fraction of a cycle, divide that by revs to get time). But my main thing would be valve size. What correlation are you using to determine required valve size at a certain lift to get the required flow rate?

I use feet per second at 28" steady state for mean air speed.

Valve size is a variable for flow and clearance reasons.

Well thats a different story. You're using test bench measures. I was trying to calculate actual steady state values at 9000RPM on a running engine!

That's fine. There's more than one way to arrive at the numbers. Steady state 28 with .55 mach is a mean is what is commonly used on these types of heads.

porchev914 wrote:

If I'm not mistaken Larry, that's the engine currently in your personal bike?

Yes it is.

PLUMMEN wrote:

what conditions are you working planning to run this motor under?
im figuring a low buck everyday driver,with the emphasis on low buck! :laugh:

It depends on budget as to going with the valves or not.

But if you start with the math and work toward the targets arrived at there, the valves would get changed Jim.

Stock valve KZ, 88cfm head like Injected put in his combo. It would work just fine. Put more duration in the cams if you wanted.

I like shorer duration cams. So my approach was give it more flow in the head and go with less duration

larrycavan wrote:

PLUMMEN wrote:

what conditions are you working planning to run this motor under?
im figuring a low buck everyday driver,with the emphasis on low buck! :laugh:

It depends on budget as to going with the valves or not.

But if you start with the math and work toward the targets arrived at there, the valves would get changed Jim.

Stock valve KZ, 88cfm head like Injected put in his combo. It would work just fine. Put more duration in the cams if you wanted.

I like shorer duration cams. So my approach was give it more flow in the head and go with less duration

Yes I agree with the idea of using a budget and putting the money where it counts the most.

The stock valve idea came to me recently on a 650 head when I needed to spend the money on the bore job instead of larger valves and seats - sacrificing a little bit of flow that could be easily fixed later on with a larger set of cams (bolt in operation) - the bore job being the bigger power maker and something that can't be swapped out in 1 hour was given that extra cash infusion.

I knew with that head cleaned up it would match the rest of my parts better and I would be able to play with it in the future when I could throw a bit more money in the right direction.

For a street motor you need to stay focused and realistic (says the guy with the magneto on his 650!) it's too tempting to want to go nuts on it once you start... you have to draw the line and say what do I "need"?

Injected wrote:

For a street motor you need to stay focused and realistic (says the guy with the magneto on his 650!) it's too tempting to want to go nuts on it once you start... you have to draw the line and say what do I "need"?

Answer: a turbo!

a 1998 1000cc superbike for about 1600 and this is all a worthless effort.....


the king has no clothes....

DoubleDub wrote:

Injected wrote:

For a street motor you need to stay focused and realistic (says the guy with the magneto on his 650!) it's too tempting to want to go nuts on it once you start... you have to draw the line and say what do I "need"?

Answer: a turbo!

I see the "KZ650 awaiting turbo project" at the bottom of your posts... believe me if I wanted the "easy" way out I would have one... I don't think it would take me anything to slap one on there within a day if I sourced all the parts and half of it would be homemade...

Yep, that and the wife are where I'm stuck at the moment. Getting a parts list together and waiting for the go-ahead... I'm also not positive yet the condition of the bike.

DoubleDub wrote:

Yep, that and the wife are where I'm stuck at the moment. Getting a parts list together and waiting for the go-ahead... I'm also not positive yet the condition of the bike.

That's my way of graciously saying, "Yes, I'm just one of the talkers, not one of the doers at the moment."
:laugh: