My supercharger setup re: Huge scott update.

[FalconGTHO]

Right. Very well.

[Brianesff]

OK guys. I'm working out some details with a forum dedicated to blow through carbs and supercharging. It appears that are a few more clutch activated superchargers than I realized in both centrifugal and positive displacement.



Look at all the blowers.

http://www.capa.com.au/main.htm



Here are some hydraulic clutches. A little pricey.

http://www.technodriveusa.com/Power-Tak ... tches.html



LPG conversions & info.

http://wps.com/LPG/index.html



The MR2 uses a roots type, straight 2 lobe design. The rotor surfaces appear to have a composite coating. I can't find the info again, but I believe the blower displacement was 1200cc.



A 6-71 displaces 410CU or 6720cc per revolution.

More later.

[MFP559]

Here's a theory that may or may not work, tell me your thoughts guys.


Take a late model V8, (coz as Barry says "twin overhead cams") beef up its internals, but keep the compression ratio low enough to run regular unleaded. Use multi-point direct port injection & a Microtech or Motec or similar management system, but one that has as many mapping points as possible. You also set the beast up to run LPG.


Manufacture a plenum chamber type manifold to sit in the valley, with the blower mounted on top. You then install a couple of large butterflies (as seen in "bug-catcher" type drag racing scoops) into each side of the plenum chamber and duct these to a fresh air source, maybe front spoiler or bonnet scoops. In line somewhere you place a K&N type foam filter element. Another foam filter element could be made to fit in the riser between the blower and the Scott Injector scoop.


I wont bother with the clutch set-up coz you guys all seem to agree on that bit. O.K. so now, when you're cruisin' along, you're running on regular petrol with no blower, just a nice V8 which, lets face it, will have enough power and torque to enjoy anyway. But thanks to some clever wiring through the Motec, when you hit that red switch here's what happens:


You activate the blower, switch to LPG (coz it just loooves high comp. ratios!), switch the Motec to the LPG program, and courtesy of some solenoids connected to the butterflies, you seal of the fresh air intake so that now the blower is pressurising the plenum chamber. And now you're having some serious FUN!


If anyone doesn't think this will work, please state you reasons why. I think it would be well worth looking into.

[FalconGTHO]

You need to diagram this and post the pic so we can see what youre talking about. But let me tell you why it wont work, even if it WOULD function in a manner of speaking. Before I start though, aside from "being like the movie" can ANYONE tell me WHY bother trying to do this? What is the payoff, reason or motivation beyond replica status?


Anyway, herewith the reasons it wont work. From what I picture you have a s/c manifold as the starting point right? If not, you have some type of custom? single plane intake? Something that has enough room to mount the s/c and also have enough room for your "air intake bypass runners" right? Why wont this work? The manifold doesnt direct air well at all in either application. A blower manifold is designed for ONLY blower use. Trying to admit air thats NOT pressurized would cause unconquerable driveability problems. Moving over to the s/c side, if its NOT a blower manifold, what I just said applies during s/c use. ANY part MUST be designed for ONE specific purpose and set of operating paramaters for it to work its best. A compromise part or application will not perform well in either environment.


Also, the "butterfly" concept you have would let some blowby past the throttle blades, not good in a pressurized setup. The s/c MUST be fully sealed from vacumm and outlet leaks.


Second, the vision I get from this is something akin to an EFI throttle body mounted in a pair to the manifold right? You woulndt have the room. Look for instance at 5.0 Mustangs. They use a 70-75mm throttle body. Since this is an EFI setup your proposing, all the sensors, parts and pieces needed for EFI to work would have to be in place, I.E. tps on the throttle bodies. Since your throttle bodies are a pair yet separated, you need linkage between the two. Unless you were thinking of some kind of "drive by wire" setup which now goes beyond the realm of backyard reality. Point is, for the vehicle to work in N/A mode, the engine is going to have to work like any other EFI setup. But you have added the twist of twin, separate throttle bodies located in a tight space. Theres no room. To make them fit, theyd be so small as to be ineffective. Like having a 3 or 400cfm single barrel carb on a V8. I could continue but theres no reason. I appreciate the thought and effort and applaud you for putting your mind to it, but its not going to work.


Cheers

[MFP559]

D'OH!

[5.7 Interceptor]

Well..... I think it's great that so many are thinking of ways to make a functional


on/off blower.. this would definately be a 'crowd pleaser'.


However for those using a 'dummy set up' like I am, we can expect a ton of idiots to make fun of it.


So to fully utilize that little red switch on my shifter I've added a 250 shot of nitrous (NOS for those fast and furious guys) which will replace the added power that the 'fake blower' is not producing.


I doubt that I'll really use it much though, but it's nice to know it's there when needed.


Doug

[MFP559]

I got so caught up trying to figure a way to deal with the hi / low pressure I totally forgot about the throttle body. OOOPS! Thanks for pointing that one out, Falcon. I guess there's no other reason for making the blower operate through a clutch other than trying to replicate what the car was meant to be.


I still believe it can be done, but as you pointed out, it would most likely need fly-by-wire technology way beyond the "piece from here, a piece from there" concept. The cost would be astronomical.


Guys, looks like you'll just have to make your mind up whether to have the blower operational, or just a dummy like thr real McCoy!


If you go with EFI though, you could set up two maps, one for economy and one for power, maybe even with different rev limits and have the power mode activated with the blower through the red switch as a compromise. That way at least you will get a noticeable increase in grunt when you turn the blower on. Does that idea work for all you guys trying to build your cars with the switchable blower??

[Dave_H]

Maybe peter should put a page together, a "museum of switchable supercharger proposals by people with not enough money".


include diagrams etc. at least it would make for a bit of a laugh for us all.

[toecutter]

The CRS approach is very simple. My one concern is that the volume of the toyota blower is just too small for even a 3.8 v6.



Still, its AN approach.



url: http://www.rodshop.com.au/accessory.htm



(cutnpasted from the CRS website)



V6 Holden Superchargers. Cheap power!



Here is power at will, a clutch operated supercharger and fitting kit.

The blower is clutch driven and engaged with a simple switch the

same as air conditioners. Three and a half pounds of boost straight

into the manifold. A 30% power increase is there when you want it,

then just turn it off.



The kits include all necessary parts including the blower, mountings,

intake and air cleaner, relief valve, manifold pulleys and belts

[Brianesff]

Excerpts from another forum.





Beginning with the SSK in the 1920s up through the 740K of the late 1930s, top of the line Mercedes featured clutch activated blow-through carburetted Rootes superchargers. A precision valve allowed the carb to draw air from the atmosphere during non-boost and then shunted to draw air from the blower when the clutch was engaged.


ED





Mercedes still uses a clutched Supercharger.


Jeff








Scania HD trucks use clutch type whipple superchargers in the 2 liter displacement range. They are used to provide low boost while the gigantic turbo spools up. I actually have 5 of these units right now and was thinking of a twin supercharged motor build-up one day! Two whipples are better than one! Plus you can turn it off while you cruise into your neighborhood to keep those A-holes happy!


J





Accel made an turbo kit in the 70s where the carb fed directly into the intake manifold through small holes when off boost and a flapper valve closed the holes under boost and shunted the air/fuel through the turbo and back into the intake manifold (could be any kind of blower)


ED





For the diverter valves I would use two or four of the


high volumn blow off valves mounted between the supercharger


and the carb inlet. These can be controled by supplying


vacumn at no boost operation and air pressure from the


same supply sorce for the air cylinders used to activate the


clutch.


TurboDude390





The other advantage to your proposed system is by being off most of the time, the Rootes' turbulence won't be preheating the air and intake manifold while off boost. I also like the stealth concept. You don't hear the blower until it's too late.


Ed





Stealth concept.


Just like the Helicopter in "Blue Thunder".


(must have used a Ford motor)


Of coarse I would bypass the mufflers at the same time. I know it's


illegal but it would definately put the fear of God into people.


B





Realistically, the extra power from the blower would almost never be


needed. The engine is almost 460cid and likely 500+ HP. Boost levels


will be conservative and the blower engaged manually.


B





The Kompressor cars from Mercedes currently use an electric clutch blower.


I saw on of them listed on ebay about a month ago...


L RE





This was the description given on a Toyota MR2 site.


http://www.mr2.net/


B





"Air Bypass Valve





The air bypass valve (ABV) serves two functions. The first is to


provide a route for air to bypass the supercharger when it is not


spinning. The second is to act as a blow-off valve when boost exceeds


aproximatly 8 PSI. The blow off point varies significantly between


cars from 8 to 10 PSI.


The valve is attached to the rear of the supercharger and is closed


when the car is not running. It is in effect, a spring loaded plunger


that blocks a port that runs from the supercharger inlet to the


outlet. When the intake manifold pressure on the plunger exceeds the


spring pressure, the valve starts to open, allowing the outlet side to


discharge some of it's air back into the inlet. This sets the maximum


boost pressure.


The bypass function is achived by adding a vacuum operated diaphram on


the back side of the valve, which pulls the valve open. As soon as the


car turns over, intake manifold vacuum is created, which is routed to


the diaphram and opens the bypass port. As the throttle is opened,


vacuum in the intake manifold drops and the valve starts to close. The


valve starts closing around 4-5" of intake manifold vacuum and is


fully closed by 1-2". Since the computer has activated the SC clutch


when intake vacuum dropped to 8", the supercharger starts spinning


while the bypass valve is still open. The valve starts closing with


the supercharger already spinning thus creating a gradual smooth


transition from an open to closed intake system.


The computer also controls a solenoid valve that vents the vacuum


diaphram on the air bypass valve to outside air. By doing this, the


computer can cause the ABV to close irregardless of intake manifold


vacuum. This valve opens as soon as there is positive pressure in the


intake, thus keeping the diaphram from working in reverse and pushing


the ABV valve closed more tightly as intake pressure increases. The


computer also holds the ABV closed this way when there is sudden


vacuum in the intake, such as when you release the throttle during a


shift. This way the intake system stays sealed to the supercharger


while you shift and the system does not have to re-seal when you step


on the gas again. After several seconds of closed throttle (constant


vacuum in the intake), the computer releases the valve and disengages


the supercharger.


Interestingly, connecting the diaphram directly to the intake system,


thus causing the valve to cycle open during shifts does not produce


any noticable change in throttle response."





The exhaust cutouts would be icing on the cake. A turbo is great in many respects, but when it comes to making beautiful, cacophonous, window shattering noise -- only a supercharger can fill the bill.


Ed