Somedays I hear 13psi is overspinning the blower, somedays I hear stock, the blower is being overspun... is that true?
if so, is it enough where they aren't even that that efficient if you change out the pulleys? If they come maxed out are you only creating more heat than boost? Or how does it work, and how can you tell they are overspun?
If they come overspun, is it enough where if you put a smaller pulley on the bottom (reduse boost) and make more power? I am just asking cause I am curious. I've already changed the pulleys out and Im sure I'm pushing the eaton to it's max...
What will start to happen if the stock eaton starts to go? Do the roters begin to flake or break off or what happens when you overspin the blower besides you create a lota heat. (and risk your motor...)
I am starting to hear a lot more about the Eaton blower, and the new KB and the works twin screws... What is the difference with a twin scew and the eaton... The new twin screws bigger cubic inches than the eaton right? thanks, Shane

 

I don't think the Eaton basic design is overspun, but I think the fact that we have a top loader makes it close to call. If it were uneficient at 8 psi we wouldn't notice any horsepower gains with pulleys. I think if it was a rear feed, most of us wouldn't have aftermarket superchargers.

 

Eaton,

The problem with the eaton M112 isn't that the top loader decreases efficieny at all. With a rear inlet eaton, we still wouldnt be able to push much past 20 lbs, compared to about 18 with the stocker.

The real problem is that the roots design is inefficient in compressing air, and generates much more heat than twin screw designs in doing so. If someone would sell twin screw rotor packs for the eaton case, it would run much cooler with less drag and more efficiency.

 

The stock Eaton superchargers are only "tested" to 12,000rpm (Per the website)

7.5" lower (stock)
2.93 upper (stock)
= 2.559727 step-up ratio

2.559727 x 5,500 rpm (redline) = 14,078 supercharger rpm

So if 12,000 rpm is the theoretical "limit" of the supercharger, then yes, they are being overspun from the factory..

-Dale

 

Gadget I agree with the second half of your statement, but I strongly disagree with the first half. The top loader very much limits the efficiency of our stock eatons. Even Jim Bell said that the top loader on his Kenne Bell made it 10% less efficient. Thats just because of the top loader.

 

I agree with you that the top inlet reduces the efficiency.

However, all it does is make it so that the true displacement of our blower is not 112 ci exactly, but slightly less. This will reduce power, but I don't think many people have reached the point where that difference becomes noticeable.

Most people haven't reached the point at which a rear loader eaton would help them alot, but they are still opting for an aftermarket blower.

The main reason to do this is that a twin screw supercharger will make more or equal power with less boost and run cooler.

Less boost makes for lower cylinder pressures and reduces stress on the engine, and the cooler outlet temperature of a twin screw supercharger reduces the opportuniy for detonation to rear it's ugly head.

I wish someone would sell twin screw rotor packs for the eaton. Big sleeper.

However there the other inefficiencies of the eaton will become the problem, like the tiny outlet at the bottom.

 

Gadget, you will be suprised how efficient the roots can be when it's setup right. I think you will find that unless you use more than 20 psi which most of you cant, than the screw it's going to help.

 

No matter how it is "set up," a roots s/c simply cannot approach the efficiency of a twin screw. The Eaton is only about 65% efficient in the best case-scenario. A twin screw can exceed 80% efficiency.

A twin screw is a true compressor. A roots is just a blower.

Just look at the Holdener "Lightning Owners Get Screwed" article. Under ALL combinations of pulleys and boost, the KB produced lower output temps than the Eaton. Case closed.

 

It really doesn't matter that much what the exit temp of the blower is, that much anyway. That is why we have an intercooler. The screws have an advantage, the roots have an advantage. For a street car/truck a roots is the thing to have. If your in to all out drag racing, or high boost applications the screw is the way to go. But back to the subject, I don't think the Eaton is being overspun from the factory. I for sure think any of the aftermarket blowers would kill the eaton.

 

Bingo. Just look at the delta T charts below. Even at 12,000, the Eaton is already increasing the temps at an increasing rate, which means that it is past the point of peak efficiency.



Whether the bearings are being overspun is debatable. I doubt that Eaton would even allow Ford to "overspin" them in that sense. But there should be no doubt that the blower is being "overspun" in the sense that it is at or past its design parameters.

Now, it must be admitted that power is about area under the curve, so just because the blower is out of steam on the top end does not mean that it is not operating in its efficient range at lower RPMs. In an engine, the HP is often already dropping off by the time the engineers decide that the engine is at its redline/shift point. So a bigger pulley, while further overspinning the supercharger, will still add power by increasing the area under the curve. But it does so that the cost of upper-end efficiency.

I have stated before that a big pulley and commensurate reduction in redline/shift point might be a path to safe power. I have never actually experimented (my engine is still bone stock), but when the Predator comes out, all kinds of possibilities exist. One could take the Metco interchangeable lower lower pulley system and play around with boost and shift points while logging intake temps. There may be big, safe power to be made by concentrating more on the bottom end and midrange while keeping max blower RPMs in a safe range.

 

Thats why you get a Works.

 

Intercoolers only remove a percentage of the heat. Put more heat in, you get more heat out. The efficiency advantage enjoyed by the twin screw is exactly the same even after intercooling.

I know of no advantage other than lower manufacturing costs which a roots has over a twin screw. In every measurable parameter, the twin screw is superior to the roots.

Please understand that I am not attacking you, eatoncharged. I am just debating the facts. Please do not take the debate personally. In general, I respect your opinions and enjoy reading your often spirited posts -- I just disagree with you on the subject at hand.

 

That is one of the most wrong things I have ever heard.

 

 

Tim, first off I am not taking anything you say as an attack. Second thanks for not taking to heart and being reasonable about this. About the subject at hand though. I researched all three available superchargers at the moment. In looking at all of them I noticed that the screws do not build near the bottom end torque that the WP112 or even the Eaton. That being said I am confident that the screws under stock block boost levels are not that much more superior if any to the WP112 and even the Eaton. True they make more peak horsepower than either one, but someone once said that it is torque that gets these trucks to move.
So to speak, what is it that we are talking about. We could say that the stock rods in these trucks are working harder than they were designed to do. Same thing with the blower, it could be spinning faster than it was designed to, but it is still taking it, and still making horsepower. It's basically my opinion that the Eaton is still efficient mainly being that the faster we turn them the more power we make. Again to a point. You could argue that it is already being overspun from the factory with a support that the power drops off around 5000. You could say that it isn't being overspun because if you add more pulley it makes more power.
So my question to you Tim is how do we decipher what efficiency is?