Alright, here are my thoughts.

Twin Screw Blower:
On a whipple, magnacharger, or radix don't they see 80% of the boost at 3500. The biggest problem with this style blower is heat soak. To battle this wouldn't you try to keep it in low rpms. Maybe a small cam would work better for this style of blower. These blowers make incredible low end torque. With the low end benefits of these blowers and a low rpm big torque cam, you could keep the shift points at 5,500 rpms or lower. Thus lowering the heat build-up on the blower and over all power. Huge torque=low ETs. I think this is why someone installed a Z06 cam with a Radix and did not see any gains.

Centrifugal Blower:
A Z06 cam in my buddy's truck didn't feel like it started to pull until 4500. Which would be great on a ATI because that is where the boost starts to build. The Z06 cam doesn't start to lay over until 6,250. This style blower will make more boost the higher it spins. A higher stall and a slightly bigger cam would be good with a ATI or Vortec. These style blowers make all of the power on the mid to upper rpms. Thus, more rpm+more boost+larger cam=Huge power. This is why my cam is perfect if not to small for my blower.

I am just thinking out loud. What do I know, I own a ATI.
P.S. if this doesn't fill 2 pages with thoughts, opinions, or arguments I will be pissed. I took me forever to write this.

 

I don't know for sure about the Whipple, but I know my Radix had 99% of it's boost just off of idle when I nailed the throttle up until about 5500 where it started getting slightly more boost (bout half a pound or so). I would always have a hard time keeping the BFG AT's from spinning if I was in 2wd.

I can't tell you much about the cam selection, but I can tell you that CompCams recommended a custom ground cam of 216/224 .524/.534 on a 114+2. I was told that would have been good for 1500-6000 rpm.

 

What is the point of spinning the motor to 6000 if you make most of your power (torque) between 2000 and 4000. This is why people lower their shift points when on the bottle. The motor will keep making power with higher rpms but, you want to keep it in that HUGE fat torque band that juice makes.
The same with the Radix. The heavier the vehicle the more this will help. All full size truck are heavy and torque is our freind. Please correct me if I am saying something stupid.

 

Stupid Fast. I have a Radix and at about 2250 rpms i see 10# boost. At 4900 it goes up to 11# boost. I looked at a centrifical set up but it takes way to long to get up to boost. I would start making boost at about 3000+ rpms. I am not saying that there is anything wrong with your ATI setup, if it works for you then more power to you but my Radix set up works beyond great for me. I guess it just depends on exactly how your truck is set up.

 

When I had a stock stall, it seemed like a good 2-3seconds before I got to 4500 rpm where I started making good power.

Then I got a TT3000, and it helped right off the line...then revs would slowly build from 3500-4500rpm...then really take off.I still had a second or more of lag!

Also, the TT3000 didn't help enough with shift extension. It still dropped to 3900rpm between shifts.

I have a Yank SS3800 going in tomorrow. According to Mike, shift extension will be about 4900. That, along with the higher stall, and higher STR should keep the ATI in the powerband for the WHOLE 1/4 mile.

I think a Z06 cam would match this power delivery perfectly.

To go fast with an ATI, you need to keep it in the 4500-6000 range all the time. Below 4500 the power is kinda dissapointing.

I think for low E.T.'s the best bang for the buck right now is the Magnacharger. Even though its more expensive, you don't really need a huge stall, edit, and injectors to make it run hard.

 

i never was completely sure of the benifits of a cam with a blower and that is whay i never got one with my whipple.

the roots/screw type blowers come on full right away, as soon as you mash the throttle. i think your theory that they dont do well on top isn't quite right though. they just do the same, they pull from the bottom to the top all the way thru. the ati on the other hand is actualy a drain on hp down low and since it builds boost exponetialy of course it feels like it kicks *** up top. i think it is just that it is weak on the botom that it gets the strong up top reputation.

also the theory that a roots/screw should be short shifted 'may' be true buy you are going to far with the 5500shift points. the super steep 1st gear in the 4l60e is just too good to be shifting too soon. i think the bigest reason to shift sooner than later is to help the rods live a long and happy life but anything under 6000rpm is fine for that. your shift points are best determined by your ET or a dyno and some calculations with transmision gear ratios or with a gtech. my whipple 6.0 liked 5800 the best.

who put a z06 cam in a whipple truck, i missed that. i would like to know more about his set up. did he loose any boost? the typical thinking on blowers and cams is you will loose some boost presure but maintain the same HP, then when you pully back up to your original boost presure you see your hp gains.

 

I agree with parish about the top end of the different types of blowers. The whipple and radix may be hotter up top, but as long as theres no detonation and the timing, airflow, and AFR is the same, the power will be roughly the same. The only difference being parasitic drag differences.

I think you may be able to get a little more PEAK hp out of a centrifugal, if you run more boost than heat on the other systems will let you. Just because of their better efficiency up top. But 20 more peak HP doesnt mean much when you have 80 less at the bottom of a gear.

 

Not to split hairs, but AFAIK the magnacharger is a roots type supercharger and the whipple is a twin screw charger, two different types of blowers. The twin screw compresses the air internally while the roots blower effectively compresses the air externally of the unit or "stacks" it as some people describe it. The reason that roots blowers tend to run hot at high rpms, (so hot in fact that there have been issues with the rotors expanding, losing their coating and "self-porting" the inside of the case) is due to the fact that from the factory (they continue to improve the design) the inlet and outlets of the blowers are horribly ineffecient, resulting in unnecessary heating of the intake charge. Proper porting of a roots blower will yield much higher gains than a stock blower especially in the upper RPMs where people say they are lacking the most.

 

Humm, has anyone compared the lobes from a Whipple vs a Magnason? I think it would be interesting to see them side by side.

How much of a twist in the rotor does it take to be a screw? vs a Roots? The whipple has a displacement advantage too...

 

I am sorry, this was not a discussion about which blower is the best. I may start another thread on that later, you damn Radix guys are everywhere . It was merely a thread about the different blower cams and which is best for which blower.
I was not limiting the whipple or radix to 5,500. I know the blowers will make power above that. I was stating that these style blowers make boost and power right off of idle. And that if you keep it a low rpms that it will keep it in the torque band longer. If you are not building power than you are not going anywhere. You install a cam designed for off idle to mid rpm power and it will magnify the already huge off idle torque you get from the blower. Where as, you install a big cam shaft that doesn't start making power until 4,500 you have just wasted the best part of roots style blower: huge off idle torque and off idle boost. On the other hand you install a 208/212 cam into a ATI motor and the cam will start to die off right after the boost starts to build.
I have seen alot of posts about cams and superchargers. Everyone is wanting a big camshaft and most everyone has a screw/roots style blower. Leave the big stalls and huge cams to ATI and Vortec owners. It "may" work better for the
screw/roots guys with a small cam and stall.
Parish did you ever try shifting lower at the track. I hope when on the bottle you tried to shift lower. I believe that it was L-EATER that installed the Z06 cam.
This is good. I am learning.