Turbos

[buickanddeere]

  A crankshaft drive blower will boost power. However even a whipple screw compressor uses more drive power at 15psi than a "properly" sized exhaust turbo at 15psi.
  There are applications where yes it is more efficient to  use a mechanically driven blower to fill the cylinders than using piston travel. However we are getting complicated and specialized.   

[SHIPCHIEF]

A Lister CS clone might not be strong enough to turbocharge (or otherwise boost) to the level you seek.
The connecting rod bearings tend to suffer wear on the top shell unless an improved upper shell half with less oil groove is employed.
The oil film is too thin. The gooves and top oil holes reduce the bearing surface area that carries the load, and provide grooves and holes to let the presurized oil film escape during the power stroke...
Turbo charging would increase the pounds of force load on the connecting rod bearing.
It is common to reduce the compression ratio when turbo charging. The result is a modest increase in combustion pressure, that is maintained longer down the stroke. Fortunately, lowering the compression ratio is easy on a Lister CS. The CS stands for Cold Start, which means "High Compression". (for 1927)
We had a group buy a while back to get 'grooveless' top bearings too. Also special oil dipper spoons or tubes are available thru talent on this forum.
I went thru a lot of bother to alter my engine for full flow oil filteration and oil temperature regulation, and increased oiling to the 'offside' injector pump. I have a couple of camshaft idler gears and offset idler gear shafts, and the afore mentioned grooveless top con-rod bearings. I dismantled my engine, de-sanded it and de-burred the block etc. working on nearly every aspect. My engine is just now getting dependable enough and broken in to play around with boost...Except my drive belt squeeks at full load! Gotta do something about that before I up the power! 

[mobile_bob]

fwiw

for an oil pump use a belt driven p/s pump off a small car, they are compact and can move sufficient
oil at and easy 40psi or so to feed a turbo, as for safety T in a pressure switch to deactivate the fuel rack
solenoid and kill the engine should the belt break and pressure be lost.

as Shipchief stated, you better do away with the oem big end grooved brgs, or they will go away for you.

i would set a limit to about 5psi, with the stock pistons, maybe 7 psi, and use a radiator neck and caps for pressure
regulation, 7lb caps are common, as are 10 lbs, 14, 15 and 16lb caps as you get some experience.

you can use a heater core for an intercooler, or better yet an old GM evaporator, they are very strong, aluminum
and readily available and can take the pressure.

it might be fun, but likely not at all practical for output over about 20kwatts electrical in my opinion.

oh ya,, before i forget,, i sure would want all my failsafe shutdowns fully functional, and damn sure my governor
working in a first world manner.

somehow a big twin turning 2 grand with 30psi of boost seems pretty dangerous to me.

just be sure to get it all in a utube clip, especially the 2 grand 30psi run



bob g

[compig]

"No , a supercharger will not give more power"

Uh, then why use one. I thought it provided more power than normal aspiration.

Maybe my context wasn't clear. A supercharger will not increase engine power more than a turbo.  The reason is that a supercharger cannot spin fast enough compared to an exhaust gas turbine which is all a turbo is. However  , that is for positive displacement superchargers , the more recent centrifugal superchargers are much more efficient but the downside is still arranging a drive system. Also , superchargers are noisy.

[AdeV73]

Also , superchargers are noisy.

Yes, but what a noise!

I can't find a clip of an old Bentley Blower on full chat, or one of those early Le Mans Mercs with the blower going, but what a lovely noise that was. The Roots blower is, of course, the one famous for its whine; I think modern 'chargers are quite a lot quieter.

[buickanddeere]

Maybe my context wasn't clear. A supercharger will not increase engine power more than a turbo.  The reason is that a supercharger cannot spin fast enough compared to an exhaust gas turbine which is all a turbo is. However  , that is for positive displacement superchargers , the more recent centrifugal superchargers are much more efficient but the downside is still arranging a drive system. Also , superchargers are noisy.

  I don't follow that line of thinking. A crank driven Whipple screw compressor turning 5000rpm and a exhaust driven centrifugal turbo turning 50,000rpm are two different designs. Depending on the size of the units, either one will flow more. We could even throw a crank driven centrifugal blower such a the Paxton into the conversation.  

[compig]

I didn't intend to infer that a positive displacement blower and a turbo should be compared in design terms. A positive displacement blower is restricted on the amount of boost it can develop for a given size compared with a turbo. This is due to the limitation on speed that a blower can be driven before it either fails mechanically or hits it's efficiency limit. Then there is still the issue of power absorbed from the engine to drive them.The exhaust driven turbo is the choice for most applications from cars to ships for this reason. Many high performance cars have now gone from blowers to turbo's to reach higher power. Mercedes at one time used blowers but have now changed to turbo's. Centrifugal blowers are like the compressor side of a turbo but with a geared up mechanical drive to reach the high speed required for effective boost , but , that drive is complex and still cannot drive the blower to the speed of an exhaust driven turbo due to the problem of changing engine speed. Changing drive speed on a high ratio drive would damage the gears due to inertia loading. As it is there is a clutch to cushion the shock loads from the gear train , but the drive ratio still has a limit. For moderate boost requirement a positive displacement blower is quite effective and may be a good practical choice for this 24/2 , I would still go for a turbo though !

[jsw123]

is there a type of supercharger with a variable speed pulley or variable speed electric motor on it to increase power when more load is applied, or in case of a vehicle, when RPMs increase?

[compig]

I'm not aware of a supercharger with variable drive except the dual stage blowers that were fitted to Spitfires and other WW2 aircraft. Electrically driven superchargers are a non starter , the size of motor and the power required to drive it would be impossible to incorporate practically. Think of the math , say a turbo or blower increases the power of an engine by a modest 50 bhp , as they are not 100% efficient that means they are extracting or absorbing more than 50 bhp to drive them , so that would require an electric motor of more than 38 KW !!!  There is an electric supercharger sold on the likes of ebay etc which always makes me howl , it's nothing more than an 80mm computer cooling fan in a tube but it's claimed to add as much as 20 bhp and improve fuel economy !!

[compig]

Also , superchargers are noisy.

Yes, but what a noise!

I can't find a clip of an old Bentley Blower on full chat, or one of those early Le Mans Mercs with the blower going, but what a lovely noise that was. The Roots blower is, of course, the one famous for its whine; I think modern 'chargers are quite a lot quieter.

You mean the SSKL Merc ?  Agreed the noise is glorious but not on a genny in an engine room !!

[compig]

Actually , the best engine noise I've ever heard is the Alfa Romeo P3 straight 8 GP car !! It puts me into a trance !!

[buickanddeere]

is there a type of supercharger with a variable speed pulley or variable speed electric motor on it to increase power when more load is applied, or in case of a vehicle, when RPMs increase?

   At low power levels a turbo isn't pumping so there isn't extra airflow through the engine wasting fuel by carrying heat up the stack. At high power the turbo spools up and supplies the extra air required. One of the reasons a turbo diesel's economy is so high.
  A positive displacement blower's output is linear and changes little from idle to redline. At part load the blower is requiring power to turn & pumping unused air through the combustion chamber. Which wastes even more fuel. You could do a half decent compromise using the bypass on a Buick3800 Whipple blower.
  All this is mute point as others have pointed out. Unless that top rod bearing  is solid and pressure lubricated. It will be looking at you through a hole in the crankcase.        

[compig]

Just thinking of that Merc SSKL , it had a clutch so that the blower only engaged when the gas pedal was floored and held there !! So no minimised losses on cruise , quite clever for the time.
Bearings wise , would that be a problem though if the engine speed stayed the same ?  Turbo's are mechanically kind to engines as only the average combustion pressure increases there are no shock loads. Heat is more of an issue , the engine would be producing more power so more waste heat.

[AdeV73]

Just thinking of that Merc SSKL , it had a clutch so that the blower only engaged when the gas pedal was floored and held there !! So no minimised losses on cruise , quite clever for the time.

The reason wasn't economy (at the time), it was reliability. The Blower Bentley's kept blowing up (no pun intended) because the superchargers were engaged all of the time...

[Irish Artist]

Okay. . .  I've found a blower, got it adapted to the engine. . . just trying to figure out what to do with the damn drive belts!



I know, I need to be more serious about this, just can't help myself!