Supercharger on a 280Z

[thehelix112]

While we're referring to past responses, I will reiterate mine. You can't make blanket statements based on a poorly designed setup. Yes I do know that they are all like that to a degree, but so what? When the degree drops to close to zero, that does it matter? I don't really see that your RB20 with incorrectly matched turbo example is in any way more pertinent to the majority of z-car owners than my L28 with slightly oversized turbo example.

Basically, (and if we can be bothered I'll elaborate) a turbocharger is the easiest way to make a certain power level.

Would you agree power output will change with boost pressure? Yes. Good. Say you're balancing it around the corner like you said. Say you squeeze the throttle open another 15%, does boost instantly change with and proportionally follow throttle position? No. Maybe close on your engine, but refer to response No. 1. You see, that's what you get out of an NA or supercharged car, that's what I personally want.

I'll be back after I've done some datalogging and 14psi runs with some info for you.

[Murph]

I don't really see that your RB20 with incorrectly matched turbo example is in any way more pertinent to the majority of z-car owners than my L28 with slightly oversized turbo example.

This thread was about superchargers on the L-series anyway, so the whole big/little engine/turbo argument is well off topic.

PM me with your results....I think we should leave this thread on topic.

[thehelix112]

Good point. Sorry everyone, I didn't mean to add to the side-trackedness. My apologies, and some more apologies if I came across angsty.. (I just went for a blast in my car, 150-190 through moderate twisties so I'm feel very mellow atm. )

Take it easy guys,

Dave

[g72s20]

Here's an interesting site for basic supercharging info Whrrrzzzzz!!

The book was written during the sixties but the basics are as sound as ever.

I heard a great story years ago of one of these vane type superchargers fitted to a Prince Gloria (S41 series).G7 2 litre 6 cylinder, hunting various street racers, and pulling away while hazing the rear tyres (POWR LOK diff).

The age is evident on the cover, which depicts a 1967 HR series Holden speedo. (Same as 1966 HD)

It's a good read!

Cheers,

Jim.

[thehelix112]

Oh and while we're getting back on track, here is some pics of my old (very basic) setup. Note I just brought this as a kit so I take no credit/responsibility:

I must admit instant throttle response was nice, but the engine never really got cooking til above 3000 anyway, which is why I made the decision to go turbocharged.

Dave

[chickenwafer]

Hyrdacharger, a great little invention.

It uses a turbine about the size of a quarter. It is mounted on the intake track on the engine and has the same basic design as a turbocharger, with a compressor and turbine side. The turbine is driven by water (hense the name "hydra") instead of hot exhaust gases. The water is pumped by an electrica water pump that operates on a seperate throttle-circut, which means the pumps speed varies with throttle position.

When you mash the loud pedal, the water pump goes into full tilt mode and pushes lots of water throught he turbine, causing it to spin and turn the compressor, which in-turn compresses the intake air (just like a turbo). Then you can route an intercooler as well for added performance.

The beauty of the hyrdacharger is gets "free" power like a turbo (without backpressure), but doesn't have any lag because of the electric water pump. Now, the water pump will take some voltage to run, but if you add a larger alternator then it should be fine, not to mention the water pump won't be that big so it won't draw much current.

So there is no parsidic lose with a hydracharger. No added backpressure, no turbo lag, and high-rpm-turbo-like effciency. It literally is the best of both worlds.....

A centrifugal supercharger I believe would be better. A screw or Eaton-type supercharger is basically just an "air-moving", refered to as displacement superchargers. The centrifugal SC works like a turbo, actually creating boost, just it's driven by the engine. And yes, they're dependant on engine rpm, but with the proper size centrifugal SC you can have power at any rpm range. Most boost near 2K rpm. Not trying to start anything here........

Dave

[Murph]

Sorry mate, but I have to rip this one up.

Hydracharger: There is no such thing as free power. It's like the whole electric supercharger idea, but worse. Why not just spin the turbine with an electric motor, removing several other points of inefficiency. That's pointless anyway, you need some pretty conisderable power to spin the compressor hard enough to make decent boost. For a factory 2L, we're talking something in the ball park of 15kW to spin the turbo. Have you seen how big a 14kW electric motor is?

Now you have to start adding up the inefficiencies. The electric motor has considerable losses as does the alternator, niether can turn 100% of the energy going into them, into the form of energy going out. If you added a water pump and piping to that the efficiency of the whole system would plummet.

Basically, it'd never work. There is NO FREE POWER. EVER.

A centrifugal supercharger I believe would be better. A screw or Eaton-type supercharger is basically just an "air-moving", refered to as displacement superchargers. The centrifugal SC works like a turbo, actually creating boost, just it's driven by the engine. And yes, they're dependant on engine rpm, but with the proper size centrifugal SC you can have power at any rpm range. Most boost near 2K rpm. Not trying to start anything here........

Do remember the positive displacement supercharger is pushing a larger amount of air per revolution than the engine is swallowing each revolution, hence compressing it. A centrifugal compressor and roots/vane/twin screw superchargers all compress the intake air via different means....but what results is no different, it's compressed air.

As for general characteristics for each...

Roots: Good bottom end and mid range, lacks top end and not capable of high boost without toasting the air.

Centrifugal: Poor bottom end, ok mid range, good top end, probably the most efficient compressor type.

Twin screw: good bottom end, mid range and top end. Capable of high boost levels. The only real downside being relativley high outlet temps, nothing intercooling wont fix.....and as Ken has shown, you can get away without it NP.

So basically, the twin screw will be making a shite load more power than the centrifugal, right up until the red line where the centrifugal will probably JUST edge it out. Good for dyno queens and that's about it in my opinion. You might as well use a turbo.

[chickenwafer]

I think I explained the hydracharger wrong....

there's an editorial on it in Sport Compact Car by Dave Coleman in the "Technobable" section. He explains it better....

And why the electric motor doesn't just spin the turbine is for the reasons you explained- it would take too much power. But the water compensates for it, hense why a hydracharger would use less current.

[Murph]

Just read the technobabble article, it seems the water is psuhed by a mechanically driven hydraulic pump, not an electric motor. None the less, why not just directly mechanically drive the compressor? The hydraulic system can only ever add inefficiency. You simply will never get more power out than you put in. The only possible pro that I can see for this system is packaging. I'd say the fact garret dropped the design is a good indication!

[chickenwafer]

Opps, my bad

And yes, Garret dropped it probably because it would cost too much R&D and too much to produce, and the public may not like it, and it is only slightly more efficient than a turbo/super anyways.

[thehelix112]

chickenwafer,

As datto-zed has said, there is not WAY it will be more efficient than either a turbo or supercharger system (has SFA incommon with a turbo system so we'll leave that alone). As datto-zed is hinting towards, by adding more energy conversions between the engine and the compressor you are only loosing more energy. You will get losses driving the water, and more losses in the water driving the turbine. Pointless.

DattoZed,

Care to explain the rootes generalisations comment? You are aware that jimmy blowers (as seen on 5 second drag cars) are roots yes? (52psi boost and I can't see them having a problem with top-end). They are however, the least adaibaticly efficient compressor of the three.

And I find it funny you mention roasting the air as a problem with roots but then say that twin-screws will do it too, (to a lesser degree I admit), but that its not a problem. You obviously are a fan of the twin-screw type. Personally I'd like to see a centrifugal compressor with a CVT drive.

Dave

[chickenwafer]

sorry, Dave, but I think I didn't explain the hydracharger right. In the article, Dave Coleman of Sport Compact Car explains it better....