They lied.

1. No one in their right mind would intercool 4 PSIG.

2. No one in their right mind would post 4 PSIG numbers because no one in their right mind would sell a 4 PSIG kit -- and no one is going to underrate the kit by 50% or more (most roots applications are in the 6-8 PSIG range). Aftermarket HP claims are always at or well beyond the ragged edge of reality.

3. 4 PSIG could not possibly get an NA 5.4 up to 390 with only 4 lbs. Physically not possible.

4. If the boost is cool enough and the timing is conservative enough, nearly any engine can take 8 PSIG.

5. 12 PSIG of theoretically perfect boost won't get an NA 5.4 to 450 lbs without lots of other mods.

eaton, I hope you haven't allowed the lies of some brainless schmuck saleman at Holley (or whomever it was) to form the basis for your defense of roots.

Please don't get me wrong -- the Eatons are excellent blowers. Mercedes doesn't put junk on its cars, even the lowly "Kompressor" cars. It's just that the only advantage a roots has over a twin screw is cost. Note how Benz went to a twin screw on its upscale sedan?

You seem to feel the need to defend your blower purchase. Don't. I'm sure that your new blower makes gobs of power -- and it looks great also!

I don't thumb my nose at roots blowers -- it's just that facts is facts. I'm going to take a real close look at the Magnum Powers roots blower. If the price is right, it may make a great choice for those who won't be running 20 PSIG. I've also been lusting after an Eaton M-series blower for my motorcycle. H*ll, I think that the Holley system looks fantasitc and the added bonus of intercooling makes it a top choice for NA 5.4 owners. It's all good.

 

In case it's of any use to someone, some good reading on this topic is Street Supercharging, by Pat Ganahl. It's not in-depth, but a good intro to supercharger types, manufacturing, tuning, etc.

It specifically states that the only disadvantage in screw type compressors vs. Roots is the effect of the compression creates more parasitic drag. However, relative to the efficiencies is has (80+% vs. 50% adiabatic efficiency, improving at higher boost levels), the effect is almost negligible.

Hope someone finds it useful.

PS. Tim Skelton, did you do a little time in engineering prior to your law career, or are you just interested enough to do all of the background research on everything? Just curious.

--Rip

 

I also recommend Corky Bell's "Supercharged!," also available on Amazon.com.

No, Rip, I have never taken any engineering courses. I've just been an auto enthusiast since I was a little tyke.

But, as a lawyer, I have also been fortunate to have spent the last five years representing ATI in the now-famous Vortech v. ATI/ATI v. Vortech false advertising lawsuit, which is now set for trial in April '04. This suit is about centrifugal v. centrifugal, but compressor science applies to any supercharger. In addition to interfacing with the clients and our experts and consultants, I have read several texts on forced induction in my spare time.

But, I am just a bench racer with a bone stock engine. This topic, however, is a bench racer topic, so I had to add my $0.02.

p.s. -- I am also currently representing Amazon.com in six lawsuits, so order those books, folks!

 

I've read parts of that book, it is good.

 

What percentage of the time, do you think a factory supercharged vehicle is run in boost? 50%, 20%, 2%, 1%? I think it is probably around 1-2% of the time. I'd say the efficiency when not in boost is very important to the manufacturer.

As has been stated in this thread, the roots is just an air pump, when in bypass, it doesn't do anything but stir up the air flowing through it. The main inefficiency is the power it takes to turn the rotors in the bearings.

As screw supercharger is an air compressor. In bypass, pressure is released from the outlet to the inlet, however the air was still compressed going through the screws. That takes power, and heats the inlet air. Of course the heating isn't a big issue because of the IC, but the extra gas it takes to compress the air unnecessarily can be a big drawback.

I was told that the smaller Benx screw units (on the SLK) have a clutch on the supercharger to get around this problem. I haven't seen or heard how they are handling it with the big screw on the V-8's in the AMG-55 and other models with that engine. I think a 12V clutch capable of handling the torque to drive the big screw would be fairly exotic (and expensive). I guess at the price range those cars are, they can afford an expensive clutch on the supercharger shaft if they need it.

Anyway, with out the clutch a twin screw is definatly not better for ALL applications.

JT

 

great and very imformative thread. I'm gonna get that book tim, and im curiuos about jtfx's question too.

 

Have any stock eaton blowers failed? Has any of the rotor packs chipped or any internal damage to the eaton after being overspun for so long? Or is everyone just saying they become less efficient after a certain point? Thanks, Shane

 

Good point, jtfx. There is definitely more parasitic loss in non-boost conditions. But the amount is really low (less than 10 HP I would speculate) and heat is not a major issue. The heat of compression is partially reversed when the compressed air expands back into the manifold. (See Supercharged!, pp. 89, 91-92)

So we now have a total of one objective criterion where the twin screw is disadvantaged to roots. Nice catch!

I think that M-B has also used a clutch even on roots blowers. Definitely a better solution for either, but obviously more complicated.

 

Any of you guys seen Mad Max? Well if his car can have a clutch of some sort to activate his S/C --- then we can definately have one ! Now how cool would that be ? a Big red button inside the cab to activate the S/C

Come on---- someone has to have seen this movie !

 

After reading this thread I have one question:
Why would an Eaton (or Works or whatever) be more efficient if it was rear fed? A roots type pulls air in from the top, throws it around the side, and into the engine. How would a rear-feed help?

A screw type compresses the air along the length of the supercharger. As such, it makes sense that it would be more efficient if rear-fed. (The particular references seems to be the KB comparison in which the KB was disadvantadges by being top-fed.

Just curious.

-Don

(As for which supercharger is better? I will be running a screw and could care less what anyone else wants to run )

 

Have any of these blowers failed? Is overspinning the blower that bad for it (the blower)? If so what lets go on the blower? Also has anything been thrown into the motor and broken anything in the motor because a blower failed cause it was being spun so fast. Thanks, Shane

 

I didnt read thru all the BS in this post but lemme add this, I dyno'd last week with a buddy who has a 4#.


My truck with 6# pulley had inlet temps after the intercooler of 136 degrees

The truck with 4# pulley had inlet temps after the intercooler of 100 degrees

These numbers were read with a Genstar tool which is the same as Fords NGS.


On a side note, my homemade powercooler reduced inlet temps to 96 degrees.

 

That statement is true to a certain extent, what you dont realize is at the same boost level the KB also had lower intake temps. The lower intake temps will allow more timing into the tune, which would allow for gains to be even higher. Im not saying 1 blower is better than another because for $3000, I would just get a T67 or T76 and put all the blowers to shame.

 

might put em to shame on the dyno, but i doubt you will on the track.

Mechanic. . . english please?

 

I took this quote from eatoncharged off another website this afternoon...
"My problem? My problem is I have officially decided that Works makes the $****** product for the Lightning. You can retire from the labor on installing one of these pieces of ****. I think I spoke too soon. Looks like I will be getting a KB."