I'm kind of curious why I never hear about anyone here using screw-type superchargers instead of roots or centrifical? I don't know off hand any screw-type "kits" for our cars, but who needs a "kit" anyways?
Screw type S/Cs are
1. True forced induction(roots is technically an air pump)
2. Produce power instantly reguardless of RPM range(centrifical charger aren't as quick as roots or screw type chargers)
3. Produce MUCH less heat than a roots charger.
4. While centricical chargers are more efficient than roots chargers, modern designs of Screw type chargers superceed these as well.
I've never heard of this "part throttle" before. Does it just bolt on?
No I just wonder why no one uses that type on a j-body. From everything I gather about different types of superchargers, screw type seem pretty much superior than any other type, yet I hear nothing about a J-body using one.
I've never heard of this "part throttle" before. Does it just bolt on?
personally i never heard of a screw type. but that being said, it is more than likley that avaliblity would be an issue, along with people just being straight up lazy like me.....
i mean why would i bother to go through miles of extra work, just to put that in and prolly see a little more gain, if i can just by a gm kit and slap that biotch on...... besides the heat problem is easily solved by alky injection
Sorry...
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Kenne Bell superchargers are twin screw, arent they?
whipple is also
reason why we do not use them
no one offers a kit to use 1
For the GM guys, there will be an LS2 kenne bell s/c, as if the vette needed more power
Pretty much all twin-screw s/c units are made by autorotor.
The stang guys with cobras usually swap eatons to kenne bell but whipple is really good too. For a j-body it would be interesting but it's doubtful that anyone would make it.
a link to kb for those interested
link
I want a cobra so bad , just to throw the KB on there, i love that whineeeeeeeeeeeeee.
Bastardking3000 wrote: I'm kind of curious why I never hear about anyone here using screw-type superchargers instead of roots or centrifical? I don't know off hand any screw-type "kits" for our cars, but who needs a "kit" anyways?
Screw type S/Cs are
1. True forced induction(roots is technically an air pump)
2. Produce power instantly reguardless of RPM range(centrifical charger aren't as quick as roots or screw type chargers)
3. Produce MUCH less heat than a roots charger.
4. While centricical chargers are more efficient than roots chargers, modern designs of Screw type chargers superceed these as well.
Now for the simple truth...
to #1 - any system that forces more air into an engine than it can normally ingest when fed by atmospheric presure IS TRULY force induced.
what you misinterpreted - Screw type SC's are compressors, Roots type are pumps. Compressors grab a gas (are in this case) and squeeze (compress) it while moving it to the outlet. Pressure is built up inside the unit before it releases. Pumps grab a volume of gas (or liquid, for that matter) and move it to the outlet without ever squeezing it at all. Only after it leaves the pump does it become pressurized.
to #2 - Roots type SC's move the same amount of air for every rotation (except at extremely low rpms) and will make about the same amount of boost at any engine rpm. Screw type SC's are almost the same, but they will have a slightly reduced amount of boost at lower engine rpms because they are more affected by low rpm operation than Roots. Centrifical SC's move liitle air at all at low rpms. The amount of air they move raises exponentially as rpm increases. Because of this, they are typically geared to make the maximum desired boost at or near the engines redline. The further you are from redline, the less boost pressure you have.
to #3 - I can't say I know this is true or not. I will say it is probably true, but the difference is not going to be very drastic. A Centrifical SC will have significantly lower outlet temperatures than either of the other 2 types at the same airflow and pressure.
to #4 - Centrifical SC's are still the winner in efficiency. Screw type efficiency depends on the level of internal compression which is typically low in automotive use. EvVen when it is high, it is still significantly lower than Centrifical. You are correct that Roots is less the least efficient.
Now to answer your 1st question
I'm kind of curious why I never hear about anyone here using screw-type superchargers instead of roots or centrifical?
Biggest reason is cost. Screw type SC's are pretty rare compared to the other 2. They also require much tighter tolerances to work properly. The lack of a large market and the extreme precision machining make them much more expensive thanthe other two types you listed.
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protomec wrote: Compressors grab a gas (are in this case) and squeeze...
That should have read Compressors grab a gas (
air in this case) and squeeze...
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check out Bahn Brenner Motorsport... they make Lysholm screw charger kits for VWs, but also sell the chargers and components separately. Prices aren't tooo bad but you could easily find an M62 cheaper and thats more than enough for the power level most here shoot for. The one distinct advantage is that BBM's charger is TINY, and could easily be made to fit in a lot of places an M62 wouldn't, but would still be capable of the same power levels. Plus, you can mount it separate from the intake mani, and route piping for an air-air IC also. On an eco at least, i'm pretty sure you could fit a Lysholm with relatively little difficulty, just finding the belt would probably be the hardest thing (as long as you can weld and fab). Not sure about the 2.4 or 2200 since i don't have in-car examples at my disposal right now.
I'd love to see someone do it, but i understand why they don't. Most people here can't fabricate parts, and thats what you'd have to do in this case. If it doesn't come in kit form, that automatically eliminates probably 60% or more of the people on this site as potential buyers (well, 60% of the people who would otherwise buy one). Then there's cost... depending on what hookups you do/don't have for parts, it would be difficult to do a setup like this for less than a decent homebrew turbo setup. And finally, its unexplored territory, and people tend to be scared to be the first to do things, since if something goes wrong, they don't have any backup since no one else has experience with it.
Arrival Blue 04 LS Sport
Eco
Turbo
Megasquirt
'Nuff said
You will never see a screw type for a J
I've had a mixed experience with my centrifical RSM kit, beyond the much discussed fuel management issues, the charger itself is a cam driven 6 rib 33inch Gatorback belt to a Vortech 800cfm blower with a max psi of 20. Weather is a huge factor in the way it runs I'd even go so far as to say 50 degrees of temputure would make as much as a 10hp or more difference. During summer I can barely touch 5psi at redline, the other night I hit 4 almost instantly and got up to 7psi by 5800rpm. PSI isnt really that important its volume that is. A vortech will put out more cfm than a roots or a turbo, this means if you do some headwork on the engine its going to flow better which generally most ppl will see a boost loss but more power. Being that a vortech has more volume to start with doing headwork will make a bigger gain and not cause much if any boost loss. The fact that it does build boost is rather annoying its not instantly there like the roots is.
Going back to the issue of temputure, only way really to help this on a roots is through alcohol injection or nitrous. The Vortech offers those solutions as well as the ability to add an aftercooler. A front mount is something that many seek to do with a vortech but its really not effective in bringing down the temps enough to make a power gain, the boost loss from adding an intercooler overcomes any gain in temputure. A more effective solution is a Cry02 kit from DEI, this knocks down the intake temp to winter like levels, you cant do anything like that on a roots cause the charger is right on the manifold.
On our cars though its all theory there really isnt an even comparision to make especially on the ecotec. Theres ways to improve the performance of both types of kits
Roots- They can do machine work on the blower to increase CFM, this all started with the GTP guys and alot of that tech and aftermarket is spilling over to the Cobalt SS ppl with the M62, cant run a wet shot on a roots cause of it eating up the blades, pulleys can be changed for more rpm to the blower, pulleys are fairly inexpensive, the M62 that may be coming for the ecotec can run to about 20psi before theres some thermal issues, really Airtonics is the only guy so far to even dive into that type of thing on a 2.2 Eco.
Centrifugal - Only way to get more power is to up the RPM to the blower, have to modify the drive system, for the RSM as stated I can only get to 7psi, I know that I can go alot higher and it will top out at 20psi, only way to get more rpms to it is to get the larger stage II kit pulley from rsm, the head has to be shaved on one side to be able to fit the larger pulley which is why the stage II kits come with the ported head, at some point I plan to switch to the stage II pulley. This should give at least 8-9psi increasing the redline to 7000 would prob provide a few more lbs as well.
Really though theres not two ecos out there running the same psi to do an even comparision of roots vs. vortech to see which is more efficient
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
For those that want to know how they work
Protomec - These guys seem to disagree with you. Although they might be slanted since they sell the things, I've done a lot of searching and the overall concensous agrees with what I said.
They do produce less heat than a roots by a considerible amount. The reason(beside the fact they compress air) Roots produce so much heat is their lack of efficiency. Screw type are far more efficient and therefore produce less heat.
Really how hard is it to make it work for your application? If you can't fab then why not get someone who can? Get something(that will fit) meant for another car, find somewhere to put it on your pully system(larger belt etc of course) fab a plate to cover where its intended to to to the intake manifld, make your own intake from the S/C to the T/B. Of course I made it sound more simple than it really is.
Cost? Well most S/C kits are pricy anyways. Might as well go the extra step.
I've never heard of this "part throttle" before. Does it just bolt on?
Actually, the link you provided is talking more about Whipple SC kits than about a screw compressor specifically, but lets take a look at the marketing anyway...
WHAT SEPERATES WHIPPLE FROM THE COMPETITION
- Positive displacement twin screw design has the highest efficiency of all superchargers including roots and centrifugal simply not true
- Higher efficiency means more power at all rpm levels Boost levels that will destroy an engine at low rpm are avoided by centrifical, if you ignore durabilty then this can be true
- Unique Whipple twin screw design provides the largest power gains across entire rpm range depends solely on boost levels
- Similar screw compressor design as the Ford GT supercar its intercooled, more on this at the end
- Same screw compressor technology that Mercedes has utilized on all their latest vehicles including the 600hp McLaren SLR, E55AMG, S55, CL55, SLK32 and SL55 again, all intercooled
- Dyno proven to produce more horsepower and torque than any other supercharger throughout the entire rpm range. hard to prove or disprove this statement, they present no evidence to prove it
- 21st century fuel injection that has more processing power than the factory computer resulting in incredible drive-ability this has nothing to do with anything
- Whipple designed air-bypass system for unsurpassed fuel economy since the compressor compresses the air internally, it cannot be bypassed for better fuel economy. The Mercedes they refer to previously has an actual electronic clutch to disengage the belt completely to improve economy
- Commitment to quality and excellence marketing- has nothing to do with the SC
- Astounding customer support from our well trained, performance enthusiast personnel marketing- has nothing to do with the SC
- Nobody can compare to the OEM packaging and quality of parts Whipple provides marketing- has nothing to do with the SC
- 50 state emission compatibility marketing- has nothing to do with the SC
- Unmistakable industry leading fit and finish marketing- has nothing to do with the SC
- 100% complete systems ready for an easy installation and trouble free operation marketing- has nothing to do with the SC
- Systems consistently produce very low levels of noise, commonly undetectable please refer to the video posted earlier in this post and decide if this is true
- True technological leader in supercharger industry marketing- has nothing to do with the SC
At the bottom of the page they have a table.
Under the heading of
Whipple Charger it says this about
Heat Buildup
"Low; intercoolers are usually not needed."
Yet all the cars they list as examples of the technology are intercooled and alot of their own SC kits are intercooled. That kind of negates their opinion by their own samples.
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About the Heat build-up...
AE, or Adiabatic Efficiency, indicates the amount of heat build up.
The Whipple site you list claims a range of 75 to 80% for any charger in their whole line.
http://www.whipplesuperchargers.com/product.asp?ProdID=1162
But when you compare that to the company that invented the charger, their specs never claim higher that about 66% for any in their whole line.
http://www.opcon.se/index.asp?sPage=1&langID=1&cID=14
Why would there be such a large difference?
Eaton does not publish this info on their site, but generally, Roots are expected to range from 40 to 60%
Vortech claims a range of 72 to 79% for any of their units.
http://www.vortechsuperchargers.com/products/units/
Based on my general experiences, I would say the Lysholm, Vortech, and Roots # fall into a real expected range. The claim by Whipple seems like total BS.
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My vortech on my old cav, sucked with the heat problem.... it was mostly because it sat right ontop of my header.
Sorry...
You have been banned from posting on this site as of 2005-09-21
00:33:32. This ban will expire 2005-09-28 00:33:32 Pacific Time.
Reason: Comments over the top regarding Jordan Kruger and other members in Versus. Also, if you have a problem with a member e-mailing you, do not bring it into the forums.
If you believe this to be in error, please contact us.
the roots on my 2.4 only ever gets luke warm even after a few hrs of spirited driving.
