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Supercharger Boost Control

Shiftable Gearbox for supercharged cars
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This idea is for the performance driver of a factory or aftermarket supercharged car that wishes to have the advantage of two performance or boost modes. This will be accomplished by a gearbox as described below. It is popular among the performance tuner of turbocharged cars to buy a boost controller which varies the amount of exaust bypassing the turbo (wastgate). Simply by pushing a button on the electronic controller or turning a knob on a manual, you can set the maximum boost pressure and thus can have both street and race performance without having to change any parts on the car.

In the world of supercharging it is common to install a smaller pulley which spins the charger faster at a given engine RPM thus giving more boost. The problem with the smaller pulley is increased wear on the super charger, increased constant force on the engine and increased fuel usage. My concept is for the eaton roots charger most common in OEM applications. It may also be adapted for other chargers as well such as the whipple/screw charger. I don't know if it will work on the scroll/G chargers such as used in the vw g60 and g40 engines because of space requirments. The eaton has a neck on it which transfers power from the enging pulley to the rotors on the charger. It is connected to the drive gears by a plastic coupler. The neck (snout) varies in size depending on the engine that it is being used on and the size of the charger m45, m62, m90 or m112, but on most applications it has plenty of available space to install a gear box. My idea is for a two speed box that can either have a shift lever on the side or could be outfited with a solinoid in order to be electricly shifted from the inside of the car. The first setting would be direct drive without any change in speed. The second would be an overdrive gearset which would give the equivelent of a smaller "race" pulley setting. This is realy a simply idea and I can't figure out why I can't find one anywhere for my car. If it is already baked, please give me the source so that i can get it for my car (GM 3800 and Eaton M90 Powered). An alternative that i have seen used is to have a variable bypass valve or regulator, that is used to bleed boost off when it gets to the maximum set point. This allows one to run a smaller pully, but run stock boost until they wish to race. They then turn the regulator up and allow more boost into the engine. The problem with this is that the charger is always turning faster, thus lowering the effenciency of the engine as well as causing constatant additional wear to the charger. My consept would have no aditional drag in normal stock mode, since the gears would only be used in over drive mode.

Please show me all of the holes in this idea. Thanks

dlapham, Jan 07 2005

Aircraft / Boat version of this idea http://www.lesliefi...the_power_plant.htm
This is the system used on the RR Merlin [dlapham, Jan 10 2005]

Eaton Information http://www.automoti...argers/gm/index.asp
Click on the Click here to see how it works link [dlapham, Jan 12 2005]

Basic supercharger types. http://www.supercha...m/content.asp?ID=76
Fixed displacement (Roots or twin-screw) and variable displacement (centrifugal, incl. turbocharger). [bristolz, Jan 15 2005]

Turbo vs Supercharger http://www.supercha...m/content.asp?ID=19
Nice article discussing supercharger types and advantages between mechanically-driven and exhaust driven systems. [bristolz, Jan 15 2005]

[link]






       I like it, although it'd have to be very well made and balanced to stand up to the rotational speeds found in supercharger systems. I'm sure that could be overcome, though.
david_scothern, Jan 07 2005
  

       Yes, I agree. A stock PD (Positive Displacement) Charger like the eaton runs at about twice crank RPM or around a max of 14,000 RPM. This ought not be hard to make. A gearbox for a centrifugal supercharger (the compressor half of a turbo) would be much harder to make since they run at a max of between 70,000 and 120,000 RPM depending on the manufacture. For the centrifugal charger I would use a variable vain charger to vary boost instead of the gearbox. I think that is even already being done, but not sure where I saw it, most varibal vain turbos vary on the exaust side, not compressor. Still I think that it could be done on the compressor and used as a centrifugal supercharger. option, b with the centrifugal charger would be a simple pressure regulator that bleads off extra boost. This gearbox idea is mainly for PD superchargers.
dlapham, Jan 07 2005
  

       Where do you live?
david_scothern, Jan 10 2005
  

       Zooomer at zzperformance.com emailed me and said that they have been working on this idea for the past 6 months. I can't wait to see it. I did not post a link because they do not yet have any info on their site and I did not post this for advertising.
dlapham, Jan 10 2005
  

       Sorry to burst your bubble but this has been around since the 1930's. It was very popular with fighter aircraft during WWII. The Rolls Royce Merlin V12 engine usually featured a 2 speed supercharger to regulate boots levels. It was manually activated, and I heard there were some pilot errors which resulted in hurt engines due to over boost.
d55guy, Jan 10 2005
  

       I am quite aware of the use of dual speed super charging in aircraft. This is why I know that this is not only possibly, but easy to accomplish. This idea is new because it is for the performance street driven car. This idea is outdated in modern piston aircraft. They use turbochargers with waistgates just like turbocharged cars do. The reason for overboost is because the overdrive mode in the aircraft was ment for the thin air of high altitude, if engaged at too low of altitude, it would cause an overboost situation. In a car, neither mode will make more boost than the engine is built to take. The reason in this case for an overdrive high-boost mood, is for racing or other requirments for more power such as having a car full of plump family members. Although it could also be used when traveling in the mountains to equil out the thinning air. Again, this is for a CAR not Airplane. I have not been able to find a system like this being used in a CAR.
dlapham, Jan 10 2005
  

       I'm curious to know where superchargers are illegal as well. Exhaust-driven superchargers (commonly known as turbochargers) are so very common that it's hard to imagine them banned anywhere.   

       Maybe it's just a ban on mechanically-driven blowers?
bristolz, Jan 10 2005
  

       Another method would be to use two superchargers, and select one or two using a coupling or clutch.
Ling, Jan 11 2005
  

       Or a two position wastegate: 50% loss and no loss. It'd be noisy.
bristolz, Jan 11 2005
  

       //very popular with fighter aircraft during WWII//   

       Suddenly I have an image of a Spitfire squadron, and all of the pilots are modding their aircraft.   

       "Hey, chaps, have you seen the latest in dual-speed supercharging? Must get one to go with my six-inch chromed exhausts and lowered suspension."
david_scothern, Jan 11 2005
  

       //Another method would be to use two superchargers, and select one or two using a coupling or clutch.//   

       I thought of this using a centrifgal charger as the second, but this would not work on my car since the charger is a part of the intake manifold. This is being done as a two stage system with turbo and supercharging, but it seems not work as well as one would like.   

       //Or a two position wastegate: 50% loss and no loss. It'd be noisy.//   

       This is what I was talking about in the concept when I said "An alternative that I have seen used is to have a variable bypass valve or regulator, thqt is used to bleed boost off when it gets to the maximum set point." While simple, this would still spin the charger at a higher than stock speed at all times.
dlapham, Jan 11 2005
  

       That depends. Are you interested in volume or velocity?
bristolz, Jan 11 2005
  

       volume and efficiency. It would however be cool to funnell the bypass air so that your car sounds like a jet going down the road.
dlapham, Jan 11 2005
  

       Throttle the supercharger's intake. The charger will then spin in a partial vacuum and do less work. This will, however, introduce throttling losses.
david_scothern, Jan 12 2005
  

       Variable Geometry Turbochargers are more efficient over a range of operating conditions because they only extract as much power as required from the exhaust gas flow.   

       I think some recon Spitfires were modded to go higher & faster than any other aircraft ( and so didn't need to carry guns ) ; polished smooth rivet heads, the works!
furmobile, Jan 12 2005
  

       //Throttle the supercharger's intake. The charger will then spin in a partial vacuum and do less work. This will, however, introduce throttling losses.//   

       This is already done on the GM 3800 and most other eaton supercharged cars. The throttle body is on the intake side of the supercharger. The supercharger has a bypass valve so that it doen not create boost until a pre-set throttle position.   

       Again all I want is an overdrive setting for the supercharger that can be changed without requiring a pully change. This is simular to the aircraft systems mentioned above.   

       //Variable Geometry Turbochargers are more efficient over a range of operating conditions because they only extract as much power as required from the exhaust gas flow.//   

       True, but this idea is for supercharged no turbocharged cars. Supercharging has its advantages as well, one of them being no turbo lag.
dlapham, Jan 12 2005
  

       //Another method would be to use two superchargers, and select one or two using a coupling or clutch.//
//but this would not work on my car since the charger is a part of the intake manifold. This is being done as a two stage system with turbo and supercharging, but it seems not work as well as one would like.//

But the second supercharger could be a smaller belt driven unit that blew slightly compressed air into your existing unit. Then you would need to do two things to disengage the second unit: disconnect the drive, and open up another intake for the first unit.
Ling, Jan 12 2005
  

       //But the second supercharger could be a smaller belt driven unit that blew slightly compressed air into your existing unit.//   

       This would work, Still I like the dual stage gear box for my application.
dlapham, Jan 13 2005
  

       Hm. I think that anything that produces induction boost beyond ambient atmospheric pressure is a supercharger and turbochargers are merely an exhaust-driven supercharger sub-species.   

       The law banning mechanical superchargers is kind of non-sensical if the intent is upon safety as turbochargers are capable of delivering more ultimate horespower than a mechanical blower and can also be more difficult to contend with, driveability-wise, than a mechanically-driven supercharger.
bristolz, Jan 15 2005
  

       Ssh... you know they'll only ban turbos too...
david_scothern, Jan 17 2005
  

       ...I think dlapham meant "underdrive gearset" instead of an "overdrive gearset".
BJS, Jul 29 2005
  

       I ment over drive not under drive. Drive would be a 1 to 1 ratio with the engine or at least the factory setting for the supercharger. Eaton and most PD chargers spin at about twice crank RPM of the engine. What I am talking about is driving the charger past stock settings with the change of a lever or button or over drive.   

       Under drive pullies are used on alternators and other parts that draw power from the engine in order to decrease the amount of power that they draw. This is not what I am talking about at all...
dlapham, Aug 23 2005
  
      
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