Twin-Screw Compressor conversion

greenwood_60

Registered User
Has anyone ever looked at putting a twin-screw compressor on the SC?

UPS just dropped off my IHI twin-screw compressor. I am attempting to fit it to my Lancia Scorpion 2.0 4 cylinder engine. In the compressors stock setup, it produces 20 psi on a 2.3 L V6. It can be spun fast enough to produce 35 psi on the 2.3 L engine. By volume, that would be 12.1 psi on the 3.8 L in stock form, and just over 20 psi if you really spun it up. The best part is the increased efficiency and decreased heat.

Just an idea. The compressor I am using is off the Mazda Millenia S, and can be bought for <$300 in decent shape on ebay.

Jason
 
Many many years ago the first twin screw went on an SC. SInce then variosu peopel have done so, some on this board some not. Most recently Dave D has produced a kit using thje 1.7 AutoRotor and now the 2.0 however its nowhere near 300$.

So yah it has been done with great results...WHat size is that mazda blower?
 
I really dont know the size of the blower. It seems to be very hard to find any specs on the blower. All I know at this point is lbs of boost, drive ratio and displacement of the stock engine.

Jason
 
That blower will work great on your Lancia but can't be spun fast enough to make good boost on the SC motor. Twin screw compressors have definite rpm limits.
 
Yeah, 35,000 rpms... Would make something like 20 psi on the 3.8...even at 12 psi, it would make more power than the stock m90, due to the cooler charge, and would make better low rpm torque because of the low leakage past the rotors.
Jason
 
I don't know where you got that information. Please elaborate on your statement. What about it is not tolerant of over revving, and what are you considering over revving? One of the benefits of twin screw compressors is the small displacement and very small rotors. This allows them to be spun very fast without issue. I am still working on getting the compressor maps out of IHI or Mazda, not sure how that is going to go.

Jason
 
The IHI twin screw is a Lysholm design manufactered by IHI (Lysholm holds the patent). The problem with twin screws as it relates to rpm is that the drive rotor (the one with the pulley) turns slower than the driven one typically by a ratio of 6/4. So if you do the math you will realize that at 15,000 pulley rpm the male rotor may be spinning as fast as 22,500rpm. At 35,000rpm the male rotor would be spinning at 52,500rpm. Not going to happen.

Most twin screws start to lose efficiency significantly above 15,000rpm. They have a compressor map which means they have a peak efficiency rpm which for most units is around 12,000-14,000rpm. This is why there are many different sizes of twin screws - because keeping the blower in it's efficiency range is important.

But like I said, if you know something I don't then that's cool too.
 
The IHI twin screw is a Lysholm design manufactered by IHI (Lysholm holds the patent). The problem with twin screws as it relates to rpm is that the drive rotor (the one with the pulley) turns slower than the driven one typically by a ratio of 6/4. So if you do the math you will realize that at 15,000 pulley rpm the male rotor may be spinning as fast as 22,500rpm. At 35,000rpm the male rotor would be spinning at 52,500rpm. Not going to happen.

Most twin screws start to lose efficiency significantly above 15,000rpm. They have a compressor map which means they have a peak efficiency rpm which for most units is around 12,000-14,000rpm. This is why there are many different sizes of twin screws - because keeping the blower in it's efficiency range is important.

But like I said, if you know something I don't then that's cool too.

For a guy who does not know very much you sure made that sound good!:rolleyes:

Marty
 
The IHI unit is 3/5, from what I have read (IHI still has not responded, in english at least). A roots blower can be spun to 14,000, surely the twin-screw can be spun faster. I will dig through my sources again and respond once I have more information from people who know.

Jason
 
Why must it surely be able to spin faster? I would think that it would be less tolerant of over-revving based on the fact that it compresses air internally between the rotors. The Eaton Roots-type just pushes it out of the blower case. I could see some bad things happening in an over-revved Lysholm.
 
Those are valid points. But don't you think that extreme internal pressures might cause a problem? Or at least limit the amount of boost you can actually make?

I don't want to mess with you, I 'm just asking.
 
As dave pointed out. In a roots blower, both rotors spin at the same rate. In a twin screw, one rotor is spinning significantly faster than the other.

That's one of the many reasons why at 10,000 rpm for a twin screw you can get 16psi where it takes a roots blower 18,000 rpm. (not accurate example but proportions are close enough)

You can do whatever you want, just make sure you're taking into account all the issues you might see. You'd hate to blow up the blower.
 
This is yet another example of someone just not taking into consideration what others are offering as information. Just because a twin screw is more efficient in certain ways then a twin helix (eaton) that does not mean that any old twin screw will fit that bill. It needs to be sized for the engine. I am attaching a photo of what happens when a twin screw is overrevved and the male and female rotors collide....Its pretty and its a 1.6L
 

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BTW, that can happen to roots style blowers just as easily. I have one here in my garage as proof. It was only spun 20% OD at the time. It was even rebuilt and everything.
 
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