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Starquest Cams


spoon32
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Just wanted to share a little spread sheet I've been working on. All numbers are accurate to the best of my knowledge with the exception of the purple cells.

http://www.starquestclub.com/forum/uploads/1288117566/gallery_5741_794_41618.jpg

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i wish i knew what all of that ment lol. im dumb.

 

yeah.. could someone offer a brief explanation of what all those numbers mean? ;) i'm sure supersteve and i aren't the only people hear that don't understand it haha

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yeah.. could someone offer a brief explanation of what all those numbers mean? ;) i'm sure supersteve and i aren't the only people hear that don't understand it haha

 

Assuming most people know the common terms of duration and lift...... Lobe separation angle (LSA) is the number of degrees spearating the intake and exhaust lobes on the camshaft. Generally speaking smaller separation lowers powerband, narrows powerband, and decreases idle vacuum. Increasing the LSA would have the opposite effect.

 

Overlap is the amount of time both the intake and exhaust valves are open. I feel this number is of great value to our cars. Assume a stock starquest with its highly restricted exhaust and fairly lower boost pressures. If a high overlap cam were to be used in that circumstance I think its vary likely the engine will experience alot of backflow..... where your exhaust gasses will go into your intake manifold rather than the exhaust manifold. I could see exhaust manifold pressures being upwards of 2 bar, while the intake pressures would be 1 bar or less.

 

It appears there is alot of variance in the valve open and close numbers. I find this interesting but don't have the experience to comment on their effects other than how it may alter cylinder pressure and manifold pressure waves.

I also find the Twist the Banshee exhaust valve closing before TDC to be especially interesting.

 

I was hoping to start a dialog from these values so people may be able to select the best cam for "their application" rather than just bigger must be better.

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I agree with what you said about the exhaust bottleneck. Most people think cams are of no signifigance on these engines. For the most part they are correct but only due to the little research put into them. I feel that there is much to be gained from a cam with more exhaust duration over inlet. What are your thoughts on that?

 

BTW, your missing data on a supposed GOD Cam....... B)

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I agree with what you said about the exhaust bottleneck. Most people think cams are of no signifigance on these engines. For the most part they are correct but only due to the little research put into them. I feel that there is much to be gained from a cam with more exhaust duration over inlet. What are your thoughts on that?

 

BTW, your missing data on a supposed GOD Cam....... B)

 

I didn't include the GOD Cam because I found it has been discontinued unfortunately. :wacko:

 

For a TB injected car with stock exhaust, I think this may also cause excessive reversion. In an MPI car with larger turbo A/R I suppose it may be worth exploring. I also have doubts about the 2.6 being able to rev high enough to take advantage of a reverse split cam. After all..... it boils down to the fact we're pretty much working with a diesel engine. :rolleyes:

It seems to me for most well designed turbo engines, a single pattern cam is very capable of getting all it can out of an engine.

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you mean head flow bench results?

 

Has nothing to do with cams. Rather porting and valve work

 

Thats a misconception.......... thats how you come to the valve lift numbers you need.

A head can only flow "X" CFM. After a certain lift you will see minimal flow gains if any, then adding more lift to that will just slow the flow velocity down.

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I'd be curious to see some cylinder flow vs. valve lift figures. Im sure somebody has done this, but so far I haven't been able to find these numbers searching between the various forum websites.

 

No misconception, cylinder flow vs valve lift is what you get from a flow bench and its not done with a cam. Yeah, you can use this info to help you find the right cam, but thats after the fact.

 

Whatdo you want toknow? stock head flow #'s? Aftermarket Heads? Our heads vs others?

 

http://sqperformance.forumcity.com/viewtopic.php?t=11

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No misconception, cylinder flow vs valve lift is what you get from a flow bench and its not done with a cam. Yeah, you can use this info to help you find the right cam, but thats after the fact.

 

Whatdo you want toknow? stock head flow #'s? Aftermarket Heads? Our heads vs others?

 

http://sqperformance.forumcity.com/viewtopic.php?t=11

 

Thanks.... those numbers are exactly what I was looking for.

 

I think you may be confusing what I am trying to say. Take for example the numbers quoted from the link you provided.

From .1 to .2 lift you get a 74% gain in flow.

From .2 to .3 lift you get a 22% gain in flow

From .3 to .4 lift you get a 4% gain in flow.

 

This trend of increase lift vs. decreasing flow will continue to a point of no flow gain or even decreased flow, due to Flow=Area*Velocity. Granted that is an over simplification since velocity and port roughness will change the flow boundry layer thickness.

But you can see how the increase in lift, or flow area, will start to decrease your intake velocity.

Since the came profile determines the valve lift....... selecting to proper lift is important.

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right, but even though we only see 4% increase, a lobe cant be square. So if anything it can be thought of as more time at or near max flow. I also dont see velocity decreasingin a boosted engine.

 

btw, ill be adding new marnel flowbench results with just valve work

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  • 2 weeks later...

right, but even though we only see 4% increase, a lobe cant be square. So if anything it can be thought of as more time at or near max flow. I also dont see velocity decreasingin a boosted engine.

 

btw, ill be adding new marnel flowbench results with just valve work

 

Off boost it might make it a bit worse, but under boost I think your right able to see huge gains with more lift. as the air is getting forced in to it.

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I just recieved my 296F from schneider this after noon and I'd like to donate some information, this is from the cam card itself.

 

Pictures mean nothing at this point since cam profiles are really in the numbers themselves.

http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1137.snc4/149971_459687057772_603717772_5621110_3691722_n.jpg

http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1226.snc4/155836_459680902772_603717772_5621008_3245196_n.jpg

http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1172.snc4/154398_459680847772_603717772_5621005_6303009_n.jpg

http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1186.snc4/150809_459680142772_603717772_5620984_5183794_n.jpg

http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs975.snc4/76814_459677922772_603717772_5620933_7213097_n.jpg

 

I hope this helps some,

 

-Chips

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That's how mine looked with lobe separation at 114 and 112 where you should degree the intake lobe to. I asked schneider about the 296 and homie talked me out of it. I'm not upset since the 292 is amazing, but you might want to make sure it doesn't smash the valve stem seals.
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That's how mine looked with lobe separation at 114 and 112 where you should degree the intake lobe to. I asked schneider about the 296 and homie talked me out of it. I'm not upset since the 292 is amazing, but you might want to make sure it doesn't smash the valve stem seals.

 

Interesting....... makes you wonder how many people have/are getting these things and ending up way out in left field without proper degreeing.

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