Okay gearheads, need some advice. (again) lol

The Roots type forces less dense air into the car were as a centrifugal is a colder denser charge. Also the higher rpm hp is less with the screw type. I can see arguments going back and forth on this for sometime on which is better. IMO if someone is interested do allot more research while you ask around.

Here is a nice link I found with information.

Here is the keypoints of each type:

Centrifugal Type Supercharging

Recommended Usage: Street Use - Commercial Use - Road Racing - Drag Racing

Positive Points:

1) Lots of Flexibility for Power Adjustments 2) Lower Discharge Temperatures 3) Great Reliability 4) Easy to install

Negative Points:

1) Not as much power at low RPMs as Roots or Screw type superchargers

Manufacturer Availability: Paxton - Powerdyne - ProCharger - Vortech

Roots Type Supercharging

Recommended Usage: Street Use - Towing - Extreme Drag Racing - Show Vehicles

Positive Points: 1) Boost throughout the entire RPM range, right off of idle 2) Highest Potential for Gain (A must-have for all-out drag racing) 3) Excellent Reliability 4) Great Appearance & Stature (Most common supercharger type for show vehicles)

Negative Points: 1) Sometimes Violent Throttle Response 2) Lower boost ratings at higher RPMs 3) Higher Than Normal Discharge Temperatures 4) Lengthy installation times

Manufacturer Availability: Allen Engine Development - BDS - Magna Charger - B&M- Holley - Littlefield - Mooneyham - Weiand

Screw Type Supercharging

Recommended Usage: Street Use - Towing - Road Racing - Drag Racing

Positive Points:

1) Great Power at Low RPMs (Great for Towing) 3) Factory Fit & Appearance 4) Great Reliability

Negative Points:

1) The Power Doesn't Keep Climbing in the High RPMs (Power curve is very flat) 2) Challenging To Achieve High Boost Levels or CFMs 3) Lengthy installation times

Manufacturer Availability: Kenne Belle - Whipple

"Nicholas Anthony" wrote in news:KUFwg.2977$ snipped-for-privacy@fe12.lga:

So then why do they recommend it for street use? Are they only thinking high-winding ricemobiles?

If it's a show vehicle, what's a blower doing on it anyway? It ain't even gonna be used...

So instantaneous power is a bad thing? Or are they saying that you can lose control because of the massive amount of power right off of idle? If you can't control your car with that much power you shouldn't have a blower.

I'd love to know why a flat power curve is a bad thing.

To simplify, if you'll be winding out your engine and you prefer your powerband up in the higher end, a turbo or centrifugal is appropriate. If you want additional power in the lower-RPM range, the roots or screw is appropriate.

Joe Calypso Green '93 5.0 LX AOD hatch with a few goodies Black '03 Dakota 5.9 R/T CC

My Vortech's boost starts at just over 3,000 RPM and climbs until I shift at around 5,900 at which point it's at about 9PSI... I will agree that it is missing the low-end grunt, especially after getting used to the torque I was getting out of the N20... but for around town and the occasional trip to the track I really like the centr. s/c. Actually I didn't think i was going to like it... but I'm actually very satisfied with it...

Actually my car is a multi-purpose car! It's DD... It's race car... It's a show car... LOL!

I agree though.. a Roots type sitting on top of the motor is sexier than a centrify all plumbed up on the front of the motor... However.. I did get a win at the local car show yesterday... knocked off some nice F-Bodys, couple of Vettes and some entries from the local low-rider club... Let's hear it for the Mustang!! LOL!

I wouldn't say it's a bad thing.. but the way it was explained to me is it can make your car drive like an On / Off switch... which in itself may not be a bad thing but might get a bit tiresome if you r car is a DD and you roast the tires at every stop light..... With the Vortech the power comes on a bit smoother, definitely not a light switch... LOL!!

If RPMs are going up and power is flat, then torque must be going down. That's why I can't keep that grin off my face around 4000RPMs (still within the speed limits) buy crackers.

Personally, I wouldn't put too much credibility to this site, or for that many any site, that sells superchargers for a profit. There are many incorrect statements in the text you quoted.

Most commercial uses need low/mid range torque for towing or hauling heavy loads etc. It is rather inconvenient, unreliable and uneconomical to spin an engine to 5,000+ rpm to pull a load. Nearly all trucks, recreation vehicles etc. that need a blower use a Roots or twin screw type. Plus, most heavy commercial trucks use turbochargers.

What does this mean?

Lower than a Roots blower but not a twin screw.

Roots and twin screws are rated to last 200k-300k miles. A centrifugal is not rated that long. OEMs use Roots blowers because they are cheap and extremely reliable.

Most non-intercooled systems are easier to install compared to a Roots/twin screw. Throw in an intercooler and they are just as complicated.

It's called torque, not "violent throttle response". This is a laughable statement. A negative? Not hardly. Plus the power is easily modulated with the throttle. They make it sound like the throttle is an on/off switch.

With a roots blower this is true to a certain extent. However, it usually occurs because the size of blower used is too small for the boost level desired on a particular engine displacement.

This is very true.

Not necessarily true. Most kits are just a little more complicated than installing a centrifugal blower.

Or launching with slicks bolted to the rear. Or just sending tires up in a cloud of smoke. Or effortlessly passing a car without down shifting. You get my point. ;)

True. Twin screws will typically out live the engine.

In addition, twin screws take the least amount of hp to spin per psi of boost, they have the lowest discharge temperatures, are quiet, provide full rated boost from idle to redline. Also, the statement that twin screw don't provide high rpm horsepower is BS. They are great for it. With all the low end torque they produce the engine can be setup to be a high rpm monster with no low/mid range torque/drivability penalty. Do this with a centrifugal blower and it would be a disaster for drivability. Take a look at the dyno charts at the link below and tell me if power drops off at higher rpms. :)

This is just a flat out false statement. It is the torque curve that is flat, not the hp curve. A flat torque curve is a good thing. Look at the curves in the above link.

WTF are they talking about? Put the right size blower on an engine and it will move all the air you need at any psi level you want. This is an idiotic statement and quite scary from someone claiming to be a blower expert.

Not really. The Kenne Bell kits can be done in a about a day or two depending on the installer's experience level. Add an intercooler to a centrifugal (most Kenne Bell kits are intercooled now) and the installation time is nearly identical.

The Kenne Bell kits for the Mustangs provide the biggest hp increases per psi of boost of any supercharger type. Their 8.5 psi intercooled kit makes 456 rear wheel hp on an otherwise stock '05+ GT. This is the same as 536 hp at the crank and is 90 rwhp more than a stock 03-04 Cobra. ProCharger, Vortech, Paxton etc. can't match them psi to psi on identical engines. Also, the area under the torque/hp curves for twin screws is greater which makes them faster at the track than centrifugals when peak hp levels are equal. Typically, a twin screw will run the same ETs as a centrifugal with 30-40 less rwhp with weight etc. being equal between the cars.

Just to clarify, the difference between Roots and twin screw blowers is a Roots is an air pump and the twin screw is a compressor. The Roots moves air to the intake manifold which is where it gets compressed. Also, there is a slight reversal in the direction of air flow because of this since the manifold air is at a higher pressure than the air in the blower. This flow reversal heats up the air more and makes the Roots less efficient. The twin screw compresses the air in the blower not the intake manifold so the air flows one way all the time. This lets the discharge temps be much cooler than a Roots and even cooler than a centrifugal, psi for psi of boost. It also makes twin screws more efficient.

Your last sentence is what it is all about. If you're happy who cares what I think. ;)

Us twin screw guys see the centrifugals as a hair dryer on steroids. :)

In some ways I thing the twin screw/Roots blowers are easier to control power delivery than a centrifugal. The power for a centrifugal comes on like a freight train in the upper rpm band. With the twin screw on my car I can modulate the power with great finesse with throttle position. It's an apples and oranges thing.

I can't get the grin off my face from 2,000 rpm to redline. ;) With a twin screw, it is not the power curve that is flat. It is the torque curve. When the torque curve is flat the hp curve is not and keeps increasing with rpm level. Check out the curves here:

Show me a dyno run from a centrifugal that matches the KB kit at 8.5 psi of boost on an otherwise bone stock 05+ Mustang GT.

both drop in torque high in the RPMsUp high they compare fairly close, KB rules down low and ATI is peaky, and to catch up it has that mid-high RPM "rush" so they are both fun, when "running", right?

The ATI is still 14 peak hp off the KB even with 0.5 psi more peak boost. The ATI torque curve is pretty good for a centrifugal. Either blower will put a smile on your face. The biggest drawback I see to a centrifugal is the narrow power band for peak boost. Beyond first and second gear it is hard to be in the meat of its boost curve on the street. For some people though this isn't a negative and is even seen as a positive. Still though, it is all good.

"Joe" wrote

Lysholm? The one being used on the Ford GT?

The twin-screw supercharger was originally invented in the 1930's by Mr. Alf Lysholm who was then Chief Engineer of SRM (Svenska Rotor Maskiner AB).

And your response is? Another site that is specifically selling one type versus a site that is impartial selling all different types of Superchargers.

Here is a heads up comparison on a Corvette newsgroup.

bInteresting article in the August issue of Hot Rod. Take a stroked 327 ci SBF with common aftermarket parts, and compare the performance of the engine with commonly available Centrifugal (Paxton Novi

1200), Turbo (HP Performance T62-1), and Roots (Holley 174) supercharger kits. Boost was limited to 9.5psi, non-intercooled.

--------------------------------Baseline------Centrifugal------Turbo--------Roots Peak HP---------------------392@6000------617@6000----600@6000--535@6000 Peak TQ---------------------386@5200------561@5200----617@4200--513@4600 Min Boost--------------------------------------1.7@2500-----5.7@2500--4.8@2500 Max Boost-------------------------------------9.5@6000-----9.5@5100--8.0@6000 Ave HP(2500-6000rpm)-------310-------------412------------460---------394 Ave TQ(2500-6000rpm)-------365-------------494------------564---------483 Ave HP(4000-6000rpm)-------352-------------518------------555---------472 Ave TQ(4000-6000rpm)-------371-------------542------------585---------497

TQ@2500-----------------------------------------360------------490---------440 TQ@3000------------------------340-------------405------------500---------450 TQ@3500------------------------355-------------450------------560---------475 TQ@4000------------------------365-------------500------------610---------500 TQ@4500------------------------380-------------525------------610---------505 TQ@5000------------------------375-------------555------------600---------505 TQ@5500------------------------355-------------555------------560---------485 TQ@6000------------------------354-------------540------------530---------475

HP@2500-----------------------------------------170------------235---------210 HP@3000------------------------190-------------235------------290---------250 HP@3500------------------------240-------------300------------375---------325 HP@4000------------------------275-------------375------------455---------375 HP@4500------------------------325-------------450------------525---------445 HP@5000------------------------360-------------525------------575---------485 HP@5500------------------------380-------------575------------600---------510 HP@6000------------------------395-------------617------------600---------535

I have been dealing with Kenne Bell for several years. The numbers they state are very close to those experienced by people who purchase and install their kits. Check out the dyno numbers on sites such as "The Corral" and you will find verification of KB's claims time and time again. They have very few complaints from those that purchase their blower kits.

I responded item for item about what was wrong with text you quoted. I see you haven't bothered to make any statements proving me wrong.

Regarding the above link, first of all you need to school yourself on the difference between Roots and twin screw blowers. They used a Roots blower that was run at 8 psi while the others were run at 9.5 psi. Also, a Holley 174 is not enough blower for that engine and boost level. You do realize a twin screw is much more efficient than a Roots blower? If they had used a twin screw of the proper size and at the same boost level then that article might have been relevant to our discussion. Regarding efficiency, the pecking order for forced induction is turbos, twin screws, centrifugals and Roots.

God... I started this discussion and I'm as confused as ever! lol!

Seems that I should get a Kenne Bell, but there's that price issue...

So, going with the centrifugal, the Ford model, what is the proper great ratio?

I imagine 3.73s are too much...???

Thanks guys. It was VERY enlightening!

Brad

I have been dealing with Kenne Bell for several years. The numbers they state are very close to those experienced by people who purchase and install their kits. Check out the dyno numbers on sites such as "The Corral" and you will find verification of KB's claims time and time again. They have very few complaints from those that purchase their blower kits.

I responded item for item about what was wrong with text you quoted. I see you haven't bothered to make any statements proving me wrong.

Regarding the above link, first of all you need to school yourself on the difference between Roots and twin screw blowers. They used a Roots blower that was run at 8 psi while the others were run at 9.5 psi. Also, a Holley 174 is not enough blower for that engine and boost level. You do realize a twin screw is much more efficient than a Roots blower? If they had used a twin screw of the proper size and at the same boost level then that article might have been relevant to our discussion. Regarding efficiency, the pecking order for forced induction is turbos, twin screws, centrifugals and Roots.

They are more expensive but there are some good trade offs for that added expense. Plus, the kits for the 4.6L engines are complete. They include fuel injectors, computer chip etc. so the installation is complete and very reliable. When considering all that comes with the kit the price isn't that bad. The 5.0L kits aren't as complete.

The 3.73's might work well since you won't make much power in the lower rpm range.

That is what we are here for. Whatever you choose will put a smile on your face.

I have a Keene Belle on a 93 5.0 and it is cool, lots of torque at 1800 rpm, gets 6 to 8 lbs, nice whistling sound with it.

I'm going with the KB, got one on my 93 5.0 for the last 10 years. If you put a KB kit on 2006 with the intercooler do you need a new hood? how bad is it trying to get the upper manifold off the 2006?

Most KB kits don't require a new hood. I don't much about the newer

4.6L engines and how easy they are to work on.