MP112/15lbs of boost on 402CID 600/700 to the wheels......video link
Sep 22, 2007 | 10:48 PM
#25
TECH Fanatic
Joined: Dec 2004
Posts: 1,099
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From: Tucson AZ
Originally Posted by thunder550
Doesn't condensation form on the WARM side of the surface? I'm definitely calling BS on this one.......
So let's think about this for a minute. If a 3.0" pulley makes about 9-10 psi on a small overlap cam in a 5.3, and a 2.8" pulley makes about 9-10 psi on a small overlap cam in a 6.0, we can extrapolate this into the theory that a 2.6" pulley (if it were even available) would make 9-10 psi on a small overlap cam in a 6.7 (402/408). (I'm assuming a front drive Radix here, for simplicity)
Let's go back to the 5.3 and 6.0 for a minute. Every drop of .2" in the pulley yields roughly a 2 psi increase. Let's ignore belt slip for a minute, and assume that this means that every .1" drop in pulley diameter yields a 1 psi increase in boost pressure. To get from 10 psi to 15 psi on the 402, we would have to drop from a 2.6" pulley to a 2.1" pulley. Again, this doesn't even account for belt slip, which would be enormous at that level (which is irrelevant anyway since you can't fit anything smaller than a 2.75" pulley, but I digress......)
So here we are, with a 2.1" pulley on our front drive/single pulley Radix on our 402 with no belt slip occurring. Completely impossible situation, but what the hell. Let's figure out how fast the blower is spinning anyway.
The stock crank pulley is roughly 7.5" diameter. 7.5/2.1 = 3.571. The supercharger is spinning 3.571 times faster than the engine. Since he doesn't say how fast he spins the engine, I'm going to assume a nice even number like 6000 RPM. At 6000 RPM, this means that our supercharger is spinning at roughly 21,426 RPM.
I'm not 100% positive on this, but I think I remember reading somewhere that the max allowable RPM's on the Radix-style blowers was about 18,000. Any faster than that and they ran the risk of damage from the rotors contacting each other. It's pretty safe to say that 21,500-ish isn't possible, which is why I call total
on this guy's results.
So let's think about this for a minute. If a 3.0" pulley makes about 9-10 psi on a small overlap cam in a 5.3, and a 2.8" pulley makes about 9-10 psi on a small overlap cam in a 6.0, we can extrapolate this into the theory that a 2.6" pulley (if it were even available) would make 9-10 psi on a small overlap cam in a 6.7 (402/408). (I'm assuming a front drive Radix here, for simplicity)
Let's go back to the 5.3 and 6.0 for a minute. Every drop of .2" in the pulley yields roughly a 2 psi increase. Let's ignore belt slip for a minute, and assume that this means that every .1" drop in pulley diameter yields a 1 psi increase in boost pressure. To get from 10 psi to 15 psi on the 402, we would have to drop from a 2.6" pulley to a 2.1" pulley. Again, this doesn't even account for belt slip, which would be enormous at that level (which is irrelevant anyway since you can't fit anything smaller than a 2.75" pulley, but I digress......)
So here we are, with a 2.1" pulley on our front drive/single pulley Radix on our 402 with no belt slip occurring. Completely impossible situation, but what the hell. Let's figure out how fast the blower is spinning anyway.
The stock crank pulley is roughly 7.5" diameter. 7.5/2.1 = 3.571. The supercharger is spinning 3.571 times faster than the engine. Since he doesn't say how fast he spins the engine, I'm going to assume a nice even number like 6000 RPM. At 6000 RPM, this means that our supercharger is spinning at roughly 21,426 RPM.
I'm not 100% positive on this, but I think I remember reading somewhere that the max allowable RPM's on the Radix-style blowers was about 18,000. Any faster than that and they ran the risk of damage from the rotors contacting each other. It's pretty safe to say that 21,500-ish isn't possible, which is why I call total
on this guy's results.What are you some kind of Engineer??
j/k bro
Sep 26, 2007 | 09:07 PM
#26
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Posts: n/a
I saw you said you had not seen a 2.6 pulley. You guys may already know but I found while looking for a few things I came across these
http://www.pulleyboys.com/radix.html
You can go up to a 2.5" Pulley.
I have not followed his setup but 15lbs he has got to be runnign some high temps. I would think with the displacement of the 408 he would be starving for more boost not running more right?
http://www.pulleyboys.com/radix.html
You can go up to a 2.5" Pulley.
I have not followed his setup but 15lbs he has got to be runnign some high temps. I would think with the displacement of the 408 he would be starving for more boost not running more right?
Last edited by BadMonkey; Sep 26, 2007 at 09:14 PM.
Oct 13, 2007 | 09:18 PM
#28
Oct 13, 2007 | 11:38 PM
#30
...I'm going to assume a nice even number like 6000 RPM. At 6000 RPM, this means that our supercharger is spinning at roughly 21,426 RPM....I'm not 100% positive on this, but I think I remember reading somewhere that the max allowable RPM's on the Radix-style blowers was about 18,000. Any faster than that and they ran the risk of damage from the rotors contacting each other....
On my setup, Whipple's redline for the 2.3L is 16k, for example. I run a 7.5" crank pulley, 2.625" compressor pulley, and shift at 5600RPM. Mathematically, it doesn't get any better than that. Roots (Eaton) can spin faster because the second rotor isn't overdriven like it is in screws, but even still, 21k+ is WAY past safe. It's a bomb. Kind of like sending power through a 4L60-E...