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Old 10-30-2007, 02:27 AM   #1
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Default Cam Design For Supercharged Engines

Does anyone know of any good books that discuss valve timing/cam design for supercharged engines? I got Corky's Book "Supercharged" today and read the first 7 chapters, and it's pretty good. Just looking for something else to read specific to cam design on DOHC 4 valve heads. I got a book on intake and exhaust systems from the campus library but it dosn't go into any detail on cams design other than pointing out how important it is. Our library dosn't have any books on cam timing or design and I searched Google, but couldn't find anything. Thanks.
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Old 10-30-2007, 08:42 AM   #2
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You'll be happy to know that the cams in the Miata work great with a supercharger. They are pretty damn close to being perfect. They have fairly low overlap and make good power from about 2500 rpm - 7500+ RPM. Unlike a turbo, these cams keep a nice flat torque curve.

(Specifically I am referring to the '99 cams.) If you want more RPM all you need to do is switch the valve springs and buckets out to a shim under bucket design and you can spin the motor (with good rods) to 8500 RPM, no problem.

As opposed to the cams, you would be better off working the head for flow. I would bias the head with 1mm over exhaust valves. Remember, making the head flow better is just as good as putting a bigger cam in. If you think you want a larger cam, consider bigger valves first.

Mark
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Old 10-30-2007, 09:30 AM   #3
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I know the stock cams are ok, but I really just want to learn about cam design for the hell of it. I'm sure there are improvement that could be made. I have done some pretty good diy headwork but the valvetrain is stock. One day I'll swap out the valves and springs as you've mentioned. From what I've read, with a SC motor, you want to keep the exhast valve closed longer than on a NA motor, but then ramp it open quickly at very high lift to quickly get the exhaust out of the way, so you can somewhat minimize overlap. I did some more searching last night but I still couldn't find any books.
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Old 10-30-2007, 10:04 AM   #4
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cam design is old school, its gonna be a dead technology in the next 5-10 years. What you need to learn is vlave timing, then learn to make the cams.

Does your school offer some classes in it? I took some grad level courses in internal combustion engines and we touched the subject a bit. If you PM over the weekend I will look for the book.
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Old 10-30-2007, 10:58 AM   #5
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Our school does offer some classes on internal combustion engines, but I can't take them yet. Yea, I realize that cam timming is really what I'm after, as that's what I put valve timing/cam design in my first post. I guess my next search I'll use cam timing instead of design and see if I find anything.

So Loki, what's that book called? Our library had a few books on interal combustion engines, but they are rather old and mostly based on carburated UHC engines. One I looked at didn't discuss cam timing in a performance oriented engine, it only explained the fundementals of how it works.

Thanks
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Old 10-30-2007, 04:43 PM   #6
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Quote:
Originally Posted by patsmx5 View Post
I know the stock cams are ok, but I really just want to learn about cam design for the hell of it. I'm sure there are improvement that could be made. I have done some pretty good diy headwork but the valvetrain is stock. One day I'll swap out the valves and springs as you've mentioned. From what I've read, with a SC motor, you want to keep the exhast valve closed longer than on a NA motor, but then ramp it open quickly at very high lift to quickly get the exhaust out of the way, so you can somewhat minimize overlap. I did some more searching last night but I still couldn't find any books.
Ok, you admittedly no nothing about cams, but you are sure that there is improvement to be made?

The problem that you have is that the Miata already is near the maximum ramp rates for the given duration. (For more on this talk to the girl at Web-cam, I think her name is Lori.) Kinda the situation with Corky and his daughter Stephanie where the girl ends up becoming a car guru... Go figure!

There are some books, I don't have them here, but more useful is a good engine simulation program where you can manipulate the various factors and test them without spending the money building the motor.

Mark
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Old 10-30-2007, 05:01 PM   #7
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Well the trick is to understand the timing as when cams are obsolete your knowledge is still good (give it 5 years)
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Old 10-30-2007, 05:31 PM   #8
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Quote:
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Kinda the situation with Corky and his daughter Stephanie where the girl ends up becoming a car guru... Go figure!


I want to be Corky's son in law.
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Old 10-30-2007, 05:42 PM   #9
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Stephanie is his daughter?
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Old 10-30-2007, 07:28 PM   #10
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Quote:
Originally Posted by Markp View Post
Ok, you admittedly no nothing about cams, but you are sure that there is improvement to be made?

The problem that you have is that the Miata already is near the maximum ramp rates for the given duration. (For more on this talk to the girl at Web-cam, I think her name is Lori.) Kinda the situation with Corky and his daughter Stephanie where the girl ends up becoming a car guru... Go figure!

There are some books, I don't have them here, but more useful is a good engine simulation program where you can manipulate the various factors and test them without spending the money building the motor.

Mark
I don't KNOW, but I would highly suspect gains in performance could be had by altering the lift, duration, overlap, ramp rates, etc. of the stock camshafts to adjust valve timing. Also changing the various aspects of the valvetrain such as the valves, springs, and shim under bucket's would change the weight of the valvetrain, so ramp rates could be adjusted if needed. I didn't say I know nothing about cams or valve timing, I said I want to learn more about it. I'll check into an engine simulation program as you suggested.
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Old 10-30-2007, 07:37 PM   #11
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Quote:
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Stephanie is his daughter?
Thought they were married myself. Cool daughter.
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