FYI super charger history ,overview

[Ernie L]

eaton TVS
http://www.eaton.com/Eaton/ProductsS...ries/index.htm

Whipple
I found an article on the Whipple site worth a look at. It has some information on the history of the automotive use of superchargers. Of course being a manufacturers site it's a bit biased and probably outdated...but still informative ....

http://whipplesuperchargers.com/inde...e_id=14#tab-35




porno

[bfrank1972]

Hah, a bit biased, a bit of an understatement and centrifugal sc's don't have any type of " lag". They just don't produce much boost in the lower rev band- up high they're very responsive. The TVS roots is quite refined and efficient, a long way from the roots blowers we had years ago


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[Ernie L]

Originally Posted by bfrank1972

Hah, a bit biased, a bit of an understatement and centrifugal sc's don't have any type of " lag". They just don't produce much boost in the lower rev band- up high they're very responsive. The TVS roots is quite refined and efficient, a long way from the roots blowers we had years ago


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I and every thing else that I have read agree with your comment on the centrifugal blowers...

Yeah they sure were not shy about blowing their own horn...PR dude was working overtime..ha ha....

I did enjoy the history and development of the SC as used in the automotive industry.... ...amazing what they could do in the late 1800's...I would kill to see how one of those rotors are made...
This link has some pics of an edelbrock e-force supercharger case being cast...I have a feeling their are NO pictures of the rotors being made..hush hush secret squirrel information dontcha know
http://www.camarohomepage.com/THRSS/supercar.htm

[CSG Mike]

With modern options, if a supercharger is properly sized to the engine, and the charge temps are kept in control, you really can't go wrong with any option for street use.

Track use is a different story, and only applies to a tiny subset of users, but some people will go that extra mile, and that is where the "good enough" setups get separated out from the "great" setups.

[Ernie L]

Originally Posted by CSG Mike

With modern options, if a supercharger is properly sized to the engine, and the charge temps are kept in control, you really can't go wrong with any option for street use.

Track use is a different story, and only applies to a tiny subset of users, but some people will go that extra mile, and that is where the "good enough" setups get separated out from the "great" setups.

yup
Race on Sunday..sell on Monday...he he he..

seriously I'm glad some people have the time, means and desire to push the limits. I'm sure it helps the rest of us.

[Fizz]

I've looked around online but still having difficulty understanding the difference between twin screw and roots. They both seem so similar....? Can someone educate me please?

[jay1989]

I had a whipple on my challenger and it was pretty nice , however that article does look a bit biased as stated above

[bfrank1972]

Originally Posted by Fizz

I've looked around online but still having difficulty understanding the difference between twin screw and roots. They both seem so similar....? Can someone educate me please?

Well let's start with "centrifugal" vs "positive displacement":

"Positive displacement" superchargers: have moving parts that physically push the air into the engine. Spinning parts grab a volume of air and move it into an engine.

"Centrifugal" superchargers: have a turbine compressor with vanes (looks sort of like a pinwheel). The idea here is it pulls air into the center of the 'pinwheel', and as it spins faster it 'throws' the air toward the outer edges of the 'pinwheel', like a centrifuge. It compresses the air as it does this, and forces this air into the engine - but there are no physical moving parts that are physically pushing air into the engine, it's all from the pressure generated by the compressor.

Roots and twin screw are both positive displacement superchargers - roots has two spinning lobes which grabs air and just pushes it into the motor, there's no compression happening inside the blower itself (there is compression in the manifold). Twinscrew has two spiral 'screw' (for lack of a better word) parts inside that grab air at one end and push it along into the motor. The difference here is as the screws push the air along, it also compresses it inside the supercharger.

Since both roots and twin screw physically push fixed volumes of air per rotation, they are very linear vs rpm, which means they produce power across the RPM band (read power increases down low and up high). When twin screw supercharges first came out, they typically were much more efficient than the roots type superchargers. In other words, they heated up the air less - with combustion (and limited octane) heat is the enemy. Nowadays, roots superchargers have been refined greatly with advanced impeller designs and materials - the TVS units are really nice, and pretty much rival twin screws on efficiency.

That said, neither positive displacement unit is as efficient as a centrifugal compressor. A centrifuge increases it's effect exponentially in proportion to the compressor speed. So if you have a centrifugal supercharger driven proportionally to engine RPM, the amount of air forced into the engine will increase exponentially as RPMs increase. This essentially means that the compressor's effect will me most noticeable in the upper RPM band, and not as noticable in the lower RPM band (relative to the positive displacement units). A well matched centrifugal supercharger will likely produce greater 'peak' HP at redline than a positive displacement unit (greater efficiency, less heat, allows greater max manifold pressure, engine timing, etc.) - but the advantages over a well matched positive displacement unit will only be in the very upper RPM band (last couple thousand RPM). Good for a race car that stays in the upper band, but not as good for everyday street driving compared to a positive displacement unit (caveat: not to say centrifugal SCs are bad for street driving, and some people prefer the 'racy' nature of centrifugal SCs).

[Kayshart]

Just to add to the above post...
In layman terms, Centrifugal superchargers are just turbochargers without the exhaust turbine side. Instead, it's connected directly to the Crank.

[King Tut]

Must downshift to maintain boost level

[CSG Mike]

Originally Posted by bfrank1972

Well let's start with "centrifugal" vs "positive displacement":

"Positive displacement" superchargers: have moving parts that physically push the air into the engine. Spinning parts grab a volume of air and move it into an engine.

"Centrifugal" superchargers: have a turbine compressor with vanes (looks sort of like a pinwheel). The idea here is it pulls air into the center of the 'pinwheel', and as it spins faster it 'throws' the air toward the outer edges of the 'pinwheel', like a centrifuge. It compresses the air as it does this, and forces this air into the engine - but there are no physical moving parts that are physically pushing air into the engine, it's all from the pressure generated by the compressor.

Roots and twin screw are both positive displacement superchargers - roots has two spinning lobes which grabs air and just pushes it into the motor, there's no compression happening inside the blower itself (there is compression in the manifold). Twinscrew has two spiral 'screw' (for lack of a better word) parts inside that grab air at one end and push it along into the motor. The difference here is as the screws push the air along, it also compresses it inside the supercharger.

Since both roots and twin screw physically push fixed volumes of air per rotation, they are very linear vs rpm, which means they produce power across the RPM band (read power increases down low and up high). When twin screw supercharges first came out, they typically were much more efficient than the roots type superchargers. In other words, they heated up the air less - with combustion (and limited octane) heat is the enemy. Nowadays, roots superchargers have been refined greatly with advanced impeller designs and materials - the TVS units are really nice, and pretty much rival twin screws on efficiency.

That said, neither positive displacement unit is as efficient as a centrifugal compressor. A centrifuge increases it's effect exponentially in proportion to the compressor speed. So if you have a centrifugal supercharger driven proportionally to engine RPM, the amount of air forced into the engine will increase exponentially as RPMs increase. This essentially means that the compressor's effect will me most noticeable in the upper RPM band, and not as noticable in the lower RPM band (relative to the positive displacement units). A well matched centrifugal supercharger will likely produce greater 'peak' HP at redline than a positive displacement unit (greater efficiency, less heat, allows greater max manifold pressure, engine timing, etc.) - but the advantages over a well matched positive displacement unit will only be in the very upper RPM band (last couple thousand RPM). Good for a race car that stays in the upper band, but not as good for everyday street driving compared to a positive displacement unit (caveat: not to say centrifugal SCs are bad for street driving, and some people prefer the 'racy' nature of centrifugal SCs).

Excellent post!

I feel that this graph (from the sticky in this subforum) demonstrates your point well.

[Calum]

Originally Posted by CSG Mike

Excellent post!

I feel that this graph (from the sticky in this subforum) demonstrates your point well.

You've said several times that simply removing the cats will give a nice gain up top. Throw an exhaust system and a little more octane at that Innovate car and I bet the differences at the top end would be much less while the difference at the bottom end would be even larger.

Yes, that completely negates repeatability and I agree that the JR kit would still be making more up top.

[CSG Mike]

Originally Posted by Calum

You've said several times that simply removing the cats will give a nice gain up top. Throw an exhaust system and a little more octane at that Innovate car and I bet the differences at the top end would be much less while the difference at the bottom end would be even larger.

Yes, that completely negates repeatability and I agree that the JR kit would still be making more up top.

Nobody's ever posted up an Innovate graph without cats, unfortunately

[Calum]

Originally Posted by CSG Mike

Nobody's ever posted up an Innovate graph without cats, unfortunately

No, but I'm pretty sure we both know someone how has access to JR carb tune graphs.