infinitebass

Kenku, you're right...I was confused. I still haven't found exactly what I'm looking for, but the Root's doesn't compress air in the case like the Lysholm, but if I remember correctly the air ends up getting compressed between the lobes. I don't remember if this causes extra heat or just extra parasitic losses.

If you think about the two lobes on one rotor, and then the third lobe on the other one enters between them, the area between the two lobes gets smaller, causing the air to compress...

Blake

KevinK2

looks like about 61% is max efficiency for whipple/lysholm, but they do have much better boost capability .... real advantage vs eaton/mod'd-roots is for boost above 5-8 psi. the eaton goes into high heat mode at 10 psi or above.


http://www.rotor.se/lysholm/PDF/diagram_lys1600ax.pdf

infinitebass

Whipple claims its almost 80% efficiency....

KevinK2

Whipple is only a distributor for autorotor screw-sc's in sweden. lysholm technologies also supplies screw-sc's to the US. Both mfgs are owned by Opcon in sweden, who also owns a major mfg'r of inductrial screw compressors.

Point is, autorotor is similar to lysholm tech in screw-sc design, and both will have similar compressor maps. I believe an mfg's map, vs a distributor's verbage.

eaton is now 'teamed' with lysholm tech, for another twist.

Evil Aviator

That's volumetric efficiency, not thermal efficiency. It is capable of thermal efficiency in the 70% range, which is about the same as a turbocharger. The really strange thing about the twin screw type of supercharger is that it tends to heat the intake air more off-boost, and less on-boost, when compared to other forced induction devices.

If you would like some good supercharger information with explanations of different types of superchargers, their installation, boost profiles, drive belt drag equations, etc., see Corky Bell's "Supercharged!" book, which is available from several online book stores.

KevinK2

my linked map showed 61% max, any other maps showing 70%?

BLUE TII

iTrader: (9)

Mazda used a Lysholm twin screw SC (like "Wipple" is) in the Miller cycle Millenia S.

It is for a ~2.3 liter V6 Miller cycle which I believe is the same max dislacement as their 2.6 liter Otto cycle Millenia, just drastically lower internal compression and so lower "working" displacement.

So, I thought it would size well for our 13B- which is why I have one in the garage :P .

For weight comparison- it is ~27 Lbs. My '89 hybrid stock turbo w/ manifold and wastegate is ~40 Lbs.

It would have to be positioned higer than the stock turbo unless one really moved things around under the hood. If most people were really worried about this they would mount their 30-40 Lb battery lower and further back in the car (mine is where the passenger muffler was in stock FC- as low as you can go and a little too far back).

To limit the pumping losses at idle and cruise I believe their are 3 choices.

1) bypass valve (as Mazda used)
2) mount throttle plates before SC (like traditional SC)
3) use an electric clutch pulley to disengage SC (as Mercedes used)

I thought the Lysholm SC would be nifty on a peripheral port rotary as its low rpm boost would negate the P-port late closing intake reversions and make it streetable and boosted. This is what is is designed to do on the ~30 degree later intake closing Miller cycle Mazda Millenia S.

Streetable boosted peripheral port

chairchild

you could take an electronic clutch off an old air-con unit as well - saves having to buy a new one for $$$

Hmm.....I've got a new idea for my 12a semi-PP

mwatson184

The sc takes a lot more power to run than an ac compressor. I'm not sure if the electronic clutch could hold up to that, but if it did that would be pretty cool.

-Marques

rotarygod

iTrader: (1)

An electric clutch can work fine on a centrifugal supercharger because they are fairly light and easy to get spinning. The positive displacement units are much harder to turn. A clutch would self destruct here under the load pretty fast. You'd have to desing one that would gradually slip for a second or 2 on purpose before totally engaging.

I like the idea of a supercharged peripheral port engine. The biggest key in forced induction of a high overlap engine is little to no exhaust backpressure. The supercharger would ensure this provided that your exhaust system is free flowing. I would easily favor the Whipple unit with an intercooler. The supercharger does take some power to spin and isn't quite as thermally efficient (but close!) as a good turbo system but I'm willing to bet that a properly tuned exhaust system will make up for most of this in the power department. Proper exhaust tuning is something that no turbo system has.

I've got Corky Bell's Supercharged! book. Great reading. Much of the book is a carbon copy of his book Maximum Boost. Another good book is called Street Supercharging. While not as in depth it is still good reading and has many nice pictures.

chairchild

anone got a spare $100, 000 that i can borrow to make this engine then?

Kenku

Actually, Toyota had various roots-type superchargers that were clutched like that; blower in the supercharged 1st gen MR2, for example.

BLUE TII

iTrader: (9)

I like the idea of a supercharged peripheral port engine. The biggest key in forced induction of a high overlap engine is little to no exhaust backpressure. The supercharger would ensure this provided that your exhaust system is free flowing. I would easily favor the Whipple unit with an intercooler. The supercharger does take some power to spin and isn't quite as thermally efficient (but close!) as a good turbo system but I'm willing to bet that a properly tuned exhaust system will make up for most of this in the power department. Proper exhaust tuning is something that no turbo system has.

That is what I was thinking as well.

Boost and high overlap seems like a good way to waste a lot of fuel blowing your air/fuel charge right out the exhaust.

It would seem to me a good solution would be to run sequential fuel injection w/ the inj. timed to begin AFTER the exhaust port is closed.

This would help make for a streetable P-port

chris wilcox

Rotarygod and BLUE TII,

You two are onto something with HUGE potential. Looks like the apex seals might be the weak point. At this time I believe the Peripheral Port Whipple with sequential injection is THE way to get a rotary with high low end torque and more specifically high average horsepower.
And as a bonus when the apex seal does fail you don't harm the whipple unless the possible sudden stop damages the gears/shaft.

gambone

iTrader: (3)

got this super off of a 3.8 buick sitten rite next to me, has a vac controled bypass. so with the valve open and useing a electic clutch from a John Deer lawn & garden tractor mite just work. I'm into turbos just becouse they are so easy to get a hold of, if it where the other way around I think we all would be useing them

chris wilcox

Quote from Lysholm contact.

Dear Chris,

the adiabatic numbers you refer to from Whipples website are isentropic eff. We are showing the mechanical efficiency which includes
all mechanical losses.
As you probably are aware of, the temperature efficiency are higher than the total mechanical efficiency.

Please let me know the reason for your interesting in this matter before we go any deeper in technical terminology.

Regards
Benny Lindbrandt
END QUOTE

So there we go with marketing again.
Realize that turbo compressor efficiency curves don't include the turbine and bearing friction losses.
Chris

KevinK2

Ya, maps just show what a driven compressor would do. doesn't include up to 30 hp to pump exh out the engine at pressures greater than boost.

But Benny seems to be inconsistent. Both whipple and Lysholm pages refer to adiabatic efficiency, which one reference says is same as isothermal eff'f, as it's used with compressors.

http://www.vairex.com/pdf/Efficiency-0523.pdf

The Lysolm map sure looks like a conventional compressor map that deals with air flow predicition, independent of parasitic mechanical losses.

thedguy

an interesting note...
Most if not all top fuel drag cars I'm told use Twin screw superchargers. on the Suzuki escudo pikes peak car they used a whipple and twin turbo's to get their as loads of power. although I believe on the upper rpms they disengaged the SC and just ran both turbo's.

My bro tells me a whipple charger will make a small block v8 feel like a big block, or a v6 like a v8 etc...

I'd like to see the supercharged P-port Sequential FI setup... sounds like it could make for a rather awsome engine.

rotarygod

iTrader: (1)

Top fuel cars use Roots units. The twin screw was used before but was banned from competition as were turbos. They have some pretty tight regulations as to what can and can't be used.

Just to bring back an earlier subject that someone mentioned. I hear people say that a supercharger or a turbo on a really high overlap engine like a peripheral port will just blow air straight through the engine and no power will be made. Nonsense! Yes it will at low rpms but remember that alot will still get to the combustion side to make some power. As rpms increase less and less is blown through the engine due to inertia keeping the gasses exactly where they need to be. even if you were to lose a little intake charge through the exhaust it is still no big deal. On high overlap naturally aspirated engines, at low rpms alot of exhaust gas gets into the intake side dilluting it and heating it up. How is this any better than a supercharger blowing a little fresh charge out? At higher rpms the inertia of escaping gasses keeps the intake and exhaust going in the proper direction just as with the forced induction engine. This assumes that a very good scavenging exhaust is used. Backpressure is your enemy. A supercharger may have an advantage in this respect to may turbo systems. On most (but not all) turbo systems, the exhaust side has more pressure than the intake side. As long as this is true then a small amount of exhaust will always dillute back into the intake side. Even a large very free flowing turbo exhaust wheel exerts alot of pressure back in the exhaust since the wheel is very heavy and hard to spin. This is why Mazda and Racing Beat used 2 smaller single tubos in their bridgeport and peripheral port race engines. The smaller wheels weighed much less and were easier to spin. Exhaust gasses from each rotor were also not interacting against each other inside the turbine wheel which led to better flow. The most important thing was that backpressure was decreased to the point that it was less than the intake boost pressure. No more exhaust diluting the intake charge and more power to be made. A supercharged engine will not have any of these issues unless it has a really crappy exhaust system on it. If a turbo system is losing so much efficiency due to this problem then why is a supercharger robbing power from the crank so much worse? On a properly designed turbo system yes there is an advantage but many prople don't design a proper turbo system do they?

chris wilcox

[I hear people say that a supercharger or a turbo on a really high overlap engine like a peripheral port will just blow air straight through the engine and no power will be made. Nonsense!]
I assume that sometimes people think about WOT conditions and apply that to idle. Right now I'm slowly educating myself on exactly what is going to happen at idle with a PPort Whipple. The intake should be at significantly lower pressure than the average exhaust press. But if one can get a strong scavenge wave just before the exhaust port closes the low idle rpm would probably be in a driveable range?

rotarygod

iTrader: (1)

Sure you'll lose a little charge out the exhaust due to port overlap. It will idle and run just fine. If you didn't have a supercharger than some of the exhaust would just flow back into the intake side whcih isn't any better. At higher rpm's the problem gets less and less. From a drivability standpoint you'll have no issues.

Jeff20B

iTrader: (13)

I know a guy who's installing a Whipple on a 20B. It looks promising.

kcr8

from what i understand Ford will be converting to whipple in the future. A lot of 03+ Cobras are running the kenne bell twin screw now and making over 600rwhp.

BLUE TII

iTrader: (9)

Sure you'll lose a little charge out the exhaust due to port overlap. It will idle and run just fine. If you didn't have a supercharger than some of the exhaust would just flow back into the intake side whcih isn't any better. At higher rpm's the problem gets less and less. From a drivability standpoint you'll have no issues.

Well, yes it will run just fine- but the gas mileage will SUCK!

That is why I love the idea of a P-port w/ Lysholm and sequencial injection- should be very streetable! The SC will stop the exhaust from dilluting the intake at idle and the sequencial inj will stop you from blowing fuel out the exhaust. It should idle well at a low rpm and get reasonable gas mileage. It could even be well muffled and still reap the benifits of the overlap!

Well, that is why I dream of it anyways...

rotarygod

iTrader: (1)

You might have read it wrong. I'm basically saying what you are.