I always like an opportunity to learn and I think your statement is contrary to what I wrote. I certainly could be wrong (I used to be so certain in my younger days) but I thought experimental data has illustrated that for a given volume of air the centrifugals added the most heat. If this fact is true then your statement would be incorrect right? Or is the experimental data to which I refer to wrong?

Now then onto efficiency... The energy required to compress a given volume of air to a lesser volume. I was also under the impression that the centrifugals were lacking here as well, but again I could certianly be wrong.

I don't mind being wrong at all, I'll know better the next time. I selected the KB becuase there isn't an IC for my application and decided to pick the device with the highest Adiabatic efficiency (or so I thought).

I too apologize for the hijack, but I wanted to try to make sure you had an opportunity to read this here as opposed to hoping you would look in a new thread.

 

Actually, a compressor forces a quantity of air into a space that it normally would not fit into unless it is under pressure. I.E. Drawing air into the large end of a roots style supercharger, and forcing it through the small end. And the tubes don't cool the air. They simply act as ducts to the intercooler, and then to the throttle body. If the SC wasn't a compressor, then it would not build boost. Whether it be in the ducts, or in the intake. It would also not heat up the air, nor heat itself, as they do. An air compressor, such as used for painting and for powering air tools, would not build pressure if there were not a tank to put the air in. Leave the drain valve open on the bottom of the tank, and that air compressor would never shut off. But it is stiil a compressor.

 

If you think I have to wait for my Vortech equiped rig to make boost above 3K then you are WRONG!!! Right around 3k I'm seeing 7+psi. Just before the shift it hits 14psi,and this is done through several feet of pipe and even an air-to-air intercooler, which you can't utilize with a roots/twinscrew...and I haven't even maxed the blower out yet.

When we talk about efficiency, some of the things mentioned are CFM, discharge temps, and parasitic loss. But if that is your criteria, then GIT 'ER DONE and go buy whatever blower floats your boat!

Now that is just retarded! Since when do any of those drivers take their dragsters to Home Depot for a load of lumber, or haul a trailer full of livestock. Better yet....I'd like to see YOU make one of "THOSE" blowers they use on your everyday street driven pickup, and make it roadworthy...NOT GONNA HAPPEN!!!

No I don't...I don't drive a big diesel. That is a totally different animal so I don't really care what they are doing! The originator of this thread drives a '99 Mountaineer for cryin' out loud!

 

Heh, totaly missed the point.... On every single part.

but hey, like you said "then GIT 'ER DONE and go buy whatever blower floats your boat!"

"this is done through several feet of pipe and even an air-to-air intercooler"

Lets see, more installation work AND a more cluttered engine bay, more chances for something to go wrong ( I have seen the couplers on the piping and actually seen the intercoolers themsevles blow out on a dyno). and STILL cant make the boost on the low end that a roots setup makes.

"...and I haven't even maxed the blower out yet."

Want a cookie?? I really dont see what the point of that would be, or why you would brag about it. In fact, the more I think about it, the more I want to laugh. I cant think of a single street car that would max out a blower... Whats YOUR point?

I never wanted to hijack this post, and the original topic, but it seems so many people know more about blowers (and "maxing" them out?!?) then the few of us that actually have experience with both types... Go and hug your Vortec, I never said they were bad, just not the greatest thing since sliced bread.

 

OH Puuuulllleeeaassse...and you think the power adders that top fuel dragster and big diesel trucks use is a good comparision to our daily driven/gas burning pickups. Again, the orginator of this post drives a 99 Mountaineer.
For what to go wrong??? Seriously...how many times have you witnessed this? I've been to several "dyno days", and visit the track often, and the last time I've seen someone blow a coupling was on a turbo'd EVO...the car was making well over 23psi. I've also seen several centrif setups perform just as well down low and even better up top with Renegade pulley upgrade.
Most accidnets I've witnessed at the dyno and the track are people throwing belts and popping head gaskets, which can happen to any type of blown setup. I'm not saying the blown coupler thing doesn't happen, but you make it seem as though it happens quite a bit...and I'm sorry, unless they're using cheap parts and accessories then I don't buy it.
And why are you making an intercooler install sound so difficult? It is NOT hard to assemble and install and it doesn't look cluttered (there's enigne pics in my gallery). However, you do understand the advatages of cooling the discharge temps, right?
OK...here's my point; when you can take a blower (roots or twinscrew) and spin it slower but still push the same CFM than a less efficient blower then that = less parasitic loss, more power and even cooler discharge temps. Maxing out a blower means reaching the maximum RPM/CFM that it is rated for. Sure...a smaller unit might still make boost, but it wont make power as "efficiently" as a unit that has a higher CFM/RPM rating. In a nut shell, I wouldn't spin a KB 1.5L or a PD BD-11A to make anythng over 8psi because efficiency goes down the drain at a high rate of speed. NOW does that make sense
If you look at other threads concerning this topic, I have always said that a roots or twinscew, on some applications, will work rather well. However, they are not the best/most efficient blower (as another member stated here) for a street/strip/off-road application...bar none. Which is why i replied with the and left it at that.

 

its all per application guys. for trucks, its great to have the roots blowers for that low rpm torque and instant towing power. plus since the roots blowers are positive displacement and make max boost at low and mid range rpms its great for trucks that dont spin high rpms. centrifugals require high rpms to attain high levels of boost and are more suited for cars and trucks that already have enough torque to shred the tires off the line. The higher you spin the motor, the more boost(giving the blower doesnt max out). they also are great for launching, you ever see a high hp nitrous car hit the juice off the line? not gonna happen unless you have loads of traction. the centrifugal is great in this case as by time you hit boost you are already moving. another downfall in using centrifugals is towing, if your tugging up a hill and then the boost kicks in, the tires can break loose, which makes it kinda hard to get over the hill.

anyway, this debate should be continued in a thread called: roots vs centrifugal - which is better. i hope the original poster got his questioned answered.

 

I said MORE CHANCES FOR SOMETHING TO GO WRONG. I also said MORE WORK involved in the install with an IC. I never said it was a difficult job. Please reread my posts a few times before trying to answer them.

"However, you do understand the advatages of cooling the discharge temps, right?"

Obviously not, You must think I have absolutely no idea what Im talking about, and have no experience with boosted engines....

 

Please excuse my bit of "sarcasm" then.

Look...I responeded to a post that said "The centrifugals are far less efficient than roots, twin-screws, etc." They work very well for certain applications, but they're not the end all/be all blowers for everyone, and I will NEVER agree to that statement!

With that said, I am done with this.

 

Some great debates here...and some great technical discussions too...but when you filet all of that I get:
A 99 Mountaineer that drives just as it did stock with the awesome power when I need it.
I picked the centrifugal for my application as I tow with the Mounty, and since I only needed some additional power when passing, climbing hills, and a solo fun factor I choose the centrifugal (and it was quite easy to install!)
It does take a little RPM to achieve boost, but when just driving around not in boost, the SC makes the throttle very snappy. It turns a 2ton SUV into a very fun vehicle.
I have yet to tow with it but I anticipate the SC to really shine when needed.

I would venture to also say, that since I already have the torque and HP of a V8, the need for a roots is less necessary than that of a 4 or 6 cyl where you need it off idle IMOO

Also, with the Powerdyne SC...
"Powerdyne delivers substantial power increases over conventional centrifugal superchargers due to the unique Hyperdyne™ impeller. Featuring an exclusive curved-blade design that literally grabs air at low speeds, the Hyperdyne™ impeller generates low RPM boost levels that are unmatched by the competition." *as stated from their web site

Kurt
99 Mounty SC'd

 

I guess we'll differ on the issue then. I thought that the thermal efficiency of the roots and twin screws was better than the centrifugals.

 

No, discharge temps are (generally) lower on a cetrif compared to a Pos. Disc.

I have yet to see a KB out-perform (overall) any centrif application. The quickest/most powerful street application (that I know of) trapped a 117mph w/ heads, cam, Pro-M Mass Air and a small shot of N20 on a 351 stroked to a 408.
Other Centrif trucks are producing as much or more HP/TQ with less with a centrif and stock stroke.
Pos. Disc. blowers have thier place for certain applications and work best for these applicaitons. However...they are not the "end all-be all" blowers for every application. For many applications, the parts and accessories limit the Pos. Disc. SC'ers true potential.......riding on the same belt as the engine accessories is just one of them.

 

Ok. I stand corrected I guess.

 

i have been reading this section because i was dreaming about puting a supercharger on my ex. but this topic seems as hot as the word "oil"

 

Just because someone on the internet states something, doesn't make it true. And I'm not saying he's wrong, but to be fair one cannot really say "roots" is better or worse than a centrifigal blower without clarifying other details.

what RPM range is the powerband?
what fuel will be used?
will there be an intercooler?
What is the engine displacement?
who will be installing it?
Who will be tuning the *system* post installation?

There is six of about 20 questions one should ask.

A blower is really just a fan, so the faster you spin it, the more flow it will provide, to a point. Flow doesn't necessarily correlate to pressure, either.

8psi of boost into a small block V8 is much smaller FLOW RATE as compared to 8psi of boost into a 500cid stroker motor.

And before you buy something, research carefully. Like "oil" there is a lot of misinformation on the 'net, and certainly in car magazines.

I'd recommend reading some of these:

Corky Bell Books:
Maximum Boost: Designing, Testing, & Install Turbocharged Sytems
Supercharged! Design, Testing and Installation of Supercharger Systems

Graham Bell:
Forced Induction Performance Tuning

Pat Ganahl:
Street Supercharging (mostly Roots oriented if I recall correctly)

And there is a McInnis book I think also, but the name escapes me.

 

Well, short of doing the testing myself I don't know who to beleive. My original argument is that the roots or twin screw blowers have a greater Adiabatic efficiency than the centrifugals.

This does not mean one does not make more horsepower than another, which some seem to confuse here. My claim is that the roots/twin screw add less heat energy when compressing a given volume of air to a given pressure. That's it.

I stick with my original position based only on the experimental data I have seen. I have gone as far as to ask the KB folks right up, but they have not responded. Whether that means they're not standing behind the claim or if they haven't has a chance to respond. But the data I have seen indicates that the roots/twin-screw has a higher adibatic efficiency.