Blower Cams
02-24-2005, 04:56 AM
#34
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Here's a bit of Q&A I had with a quite intelligent fella.
I see posts repeatedly about how the lobe seperation angle on a blower motor should be inbetween a 114-119 degree angle. That is total bull **** in my opinion. Knowing it's all about the valve events, the lsa idea doesn't make much sense at all. What is your opinion on lsa, besides it being a by-product. Have you ever cammed a blower motor and used a narrow lsa?
Blower LSA...Ha! As you say, it's a by-product. The more overlap you give a blower motor, the more power you'll make, just like N/A. You just don't *need* as much overlap to make power....since upping the boost 1psi would give more gains then 5 degrees of added overlap.
I'm coming around. I get what your hinting at. It almost seems the best cam would be a stockish one, with rearranged valve events. Or something that can keep the power range down in the blowers working area. Bump duration, take down the lsa for the suited valve events, but then that gets to the beginning paragraph and overlap.
Yes, you should design a cam that is ment to work in the 'sweet' spot of the blower/motor combo. Small, more aggressive lobes on a tight LSA keeping near the stock IVC/EVO .006 events will give great results.
I see posts repeatedly about how the lobe seperation angle on a blower motor should be inbetween a 114-119 degree angle. That is total bull **** in my opinion. Knowing it's all about the valve events, the lsa idea doesn't make much sense at all. What is your opinion on lsa, besides it being a by-product. Have you ever cammed a blower motor and used a narrow lsa?
Blower LSA...Ha! As you say, it's a by-product. The more overlap you give a blower motor, the more power you'll make, just like N/A. You just don't *need* as much overlap to make power....since upping the boost 1psi would give more gains then 5 degrees of added overlap.
I'm coming around. I get what your hinting at. It almost seems the best cam would be a stockish one, with rearranged valve events. Or something that can keep the power range down in the blowers working area. Bump duration, take down the lsa for the suited valve events, but then that gets to the beginning paragraph and overlap.
Yes, you should design a cam that is ment to work in the 'sweet' spot of the blower/motor combo. Small, more aggressive lobes on a tight LSA keeping near the stock IVC/EVO .006 events will give great results.
02-24-2005, 04:05 PM
#35
Originally Posted by James B.
Hey guys, with a blower motor overlap has to be minimzed or it will bleed off boost and unburnt fuel. High LSA, good lift biased heavily toward exhaust, and minimal overlap.
02-24-2005, 04:19 PM
#36
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Overlap increases cylinder pressure. Boost increases cylinder pressure.
More boost requires less overlap to make a given cylinder pressure. That certain cylinder pressure being the desired power. If we want X amount of power. And we add a blower. It doesn't take as much overlap to get us to (x).
Perhaps the internet hype has raised the "no overlap" scare to a far far extent. People are so affraid of blowing boost out of the tail pipes they've limited themselves to no tighter than 114* lsa, on ANY 2 given lobes.
Why? Is it really necessary to decrease overlap on a small grind w/ low boost?
More boost requires less overlap to make a given cylinder pressure. That certain cylinder pressure being the desired power. If we want X amount of power. And we add a blower. It doesn't take as much overlap to get us to (x).
Perhaps the internet hype has raised the "no overlap" scare to a far far extent. People are so affraid of blowing boost out of the tail pipes they've limited themselves to no tighter than 114* lsa, on ANY 2 given lobes.
Why? Is it really necessary to decrease overlap on a small grind w/ low boost?
02-24-2005, 04:22 PM
#37
Originally Posted by SportSide 5.3
Think about it.
Overlap increases cylinder pressure. Boost increases cylinder pressure.
More boost requires less overlap to equal a given power. Perhaps the internet hype has raised the "no overlap" scare to a far far extent. People are so affraid of blowing boost out of the tail pipes they've limited themselves to no tighter than 114*, on any 2 given lobes.
Why?
Overlap increases cylinder pressure. Boost increases cylinder pressure.
More boost requires less overlap to equal a given power. Perhaps the internet hype has raised the "no overlap" scare to a far far extent. People are so affraid of blowing boost out of the tail pipes they've limited themselves to no tighter than 114*, on any 2 given lobes.
Why?
02-24-2005, 08:41 PM
#39
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Originally Posted by moregrip
ok, I'll think about it while I'm washing my truck
I finally selected the comp cam 212/218 114LSA. The folks at Comp cam thought the GT7 would build up too much compression and limit the fuel to race gas.
Good Luck i nyou selection
02-25-2005, 09:31 AM
#40
Originally Posted by Jamesbond2509
I finally selected the comp cam 212/218 114LSA. The folks at Comp cam thought the GT7 would build up too much compression and limit the fuel to race gas.
Good Luck i nyou selection
Good Luck i nyou selection