Is there a limit for a S/C

[Gordo]

I know if you want bhp you go with a turbo but I was wondering if the S/C has a limit where no more power can be given. So far from what I've seen its around 170-200bhp.
I no there are other ways of getting horse power as well. But purely from a FI point of view.

[93_Clubman]

That would be for the Eaton M45 at the rear wheels, but there are other SCs out there which if you're prepared to spend the money on will give you more. Fair to say though that turboing is a more cost effective way of getting more power. Reminds me of the observation: "Performance costs money, how fast do you want to spend?"

[Guran]

Top fuel dragsters use SC don't they? They manage OK.

I think it's more a case of spending on strengthening the engine internals to cope with the power ... whether it's SC or turbo.

[Hellmun]

Those superchargers do tend to be larger than the whole BP block . Changing turbo compressor wheels or even the whole turbo is a lot cheaper/easier than getting a supercharger with more puff to increase boost pressure. The supercharger doesn't quite scale so well. I think you can get over 200hp though with an M60 or a Kraftwerks centrifugal unit though if that's what your after. The smoothness of a good positive displacement charger is quite incredible.

[timk]

An uncorked centrifugal would make more than enough power to bend the stock rods!

[Benny]

Superchargers, like the old GM671 can suck in HUUUUUGE amounts of air , and spit it right out again into your inlet manifold.
One of these would blow the top right off your engine too.
Just like they do with dragsters every now and again, but is that what you really want?

After all, a dragster engine is fully re-built after EVERY run, and I think you would like to get more than 400M out of your engine.

The deciding factor is size and weight.
Superchargers that suck a lot of air are mechanically large and heavy, whereas a turbo of similar output is a lot smaller and lighter, hence their use in hi-powered street cars.

Obvioulsy a twin-charger setup like VW are now using is the best of both worlds.
A small supercharger for low-down response, with a turbo cutting in for the high rev bit.

Superchargers are usually hampered by only having one ratio on their pulleys, so they can either be set up for low boost or medium to high boost, but not both.
That's why many supercharged engines run out of puff around 6,000RPM in most installations.
You can set them up for top end power, but then they are usually pretty well useless at low revs.

The other thing is parasitic drag.
Superchargers do use up a lot of the extra horsepower they help the engine to produce, and in a dragster, this can be as much as 600bhp, so this extra load on the engine has to be compensated for, usually by running even more boost.
Turbochargers do not consume any power and in fact, actually use the heat and pressure of the exhaust, which is usually wasted energy, to produce boost so they are inheritantly more efficient.

There is also chemical supercharging, which is like nitrous injection.
This uses a chemical rich in oxygen to make the engine think there is more air than there is, but if you are using nitrous, make sure you also inject the appropriate amount of extra fuel otherwise your engine will run very lean and blow up very quickly.
However, nitrous is illegal to use on the road in NSW and it is even illegal to have a tank fitted in your car if it is physically connected.

[orx626]

Turbochargers do not consume any power and in fact, actually use the heat and pressure of the exhaust, which is usually wasted energy, to produce boost so they are inheritantly more efficient.

Actually that is not true Benny. The fact that the turbocharger uses exhaust pressure and flow to compress and pump the air intake charge means that the engine is loaded by the turbocharger and is therefore a parasitic load....and when in positive pressure the parasitic power consumption between a supercharger and a turbocharger become somewhat closer. However, when the engine air intake is in vacuum the parasitic load of a turbocharger is substantially less than a supercharger.

Regards,
Danny

[Gordo]

Thanks for all the info guys.

I've been looking at FFS and there stuff looks quite good. Under 4k US and with the Aussie dollar strong in the US market I was thinking it could be the best way to go.

[charlie_91]

Turbochargers do not consume any power and in fact, actually use the heat and pressure of the exhaust, which is usually wasted energy, to produce boost so they are inheritantly more efficient.

Actually that is not true Benny. The fact that the turbocharger uses exhaust pressure and flow to compress and pump the air intake charge means that the engine is loaded by the turbocharger and is therefore a parasitic load....and when in positive pressure the parasitic power consumption between a supercharger and a turbocharger become somewhat closer. However, when the engine air intake is in vacuum the parasitic load of a turbocharger is substantially less than a supercharger.

Regards,
Danny

HE KNOWS ALL

[zoomzoomzoom]

Hi Folks,

I'm thinking of going down the Kraftwerks SC road and applying JTG Liquid gas injection (not dual fuel). Not sure how much KWs I'm gonna spend down the road, but this is where I'm starting. Gas has a higher octane than pump fuel and exhause "lower" CO2. Liquid injection is also supposed to have an inter-cooling affect.

BTQ: Any success stories you know about LPG Gas tank placement on MX-5s?

Regards,
zzz

[Benny]

Turbochargers do not consume any power and in fact, actually use the heat and pressure of the exhaust, which is usually wasted energy, to produce boost so they are inheritantly more efficient.

Actually that is not true Benny. The fact that the turbocharger uses exhaust pressure and flow to compress and pump the air intake charge means that the engine is loaded by the turbocharger and is therefore a parasitic load....and when in positive pressure the parasitic power consumption between a supercharger and a turbocharger become somewhat closer. However, when the engine air intake is in vacuum the parasitic load of a turbocharger is substantially less than a supercharger.

Regards,
Danny

However, the losses using a turbocharger at high boost levels are far less than the losses incurred by a supercharger.
Superchargers ALWAYS use power, even at low revs, but turbochargers do not.
In relation to each other, turbochargers consume far, far less power than superchargers do.

What you also forget Danny, is that a lot of the rotational force of a turbocharger is not caused just by exhaust pressure, but by exhaust heat, and it is this heat that actually causes most of the rotation of the turbocharger impellor.
If not used this way, the energy in the heat of the exhaust is just wasted.
Boyle's Law says that an increase in the temperature of a gas will also mean an increase in pressure, and it is the heat generated by the exhaust that causes this increase in pressure which turns the impellor.
So with a turbocharger, you do get something for nothing!

[orx626]

Turbochargers do not consume any power and in fact, actually use the heat and pressure of the exhaust, which is usually wasted energy, to produce boost so they are inheritantly more efficient.

Actually that is not true Benny. The fact that the turbocharger uses exhaust pressure and flow to compress and pump the air intake charge means that the engine is loaded by the turbocharger and is therefore a parasitic load....and when in positive pressure the parasitic power consumption between a supercharger and a turbocharger become somewhat closer. However, when the engine air intake is in vacuum the parasitic load of a turbocharger is substantially less than a supercharger.

Regards,
Danny

However, the losses using a turbocharger at high boost levels are far less than the losses incurred by a supercharger.
Superchargers ALWAYS use power, even at low revs, but turbochargers do not.
In relation to each other, turbochargers consume far, far less power than superchargers do.

What you also forget Danny, is that a lot of the rotational force of a turbocharger is not caused just by exhaust pressure, but by exhaust heat, and it is this heat that actually causes most of the rotation of the turbocharger impellor.
If not used this way, the energy in the heat of the exhaust is just wasted.
Boyle's Law says that an increase in the temperature of a gas will also mean an increase in pressure, and it is the heat generated by the exhaust that causes this increase in pressure which turns the impellor.
So with a turbocharger, you do get something for nothing!

That's fine Benny...but it is not what you stated in your first post. I didn't forget anything....thanks for correcting your information.

Regards,
Danny

[16bit]

you can get heaps of hp out of a bp with a supercharger. on the flyin miata site they have a dyno of a built motor with an mp62 with about 300whp.

on miataturbo there is a time attack car on there with the c30-94 rotrex charger on it with about 340whp. all these a built motors with bigger displacement and lots of other mods though.

[Gordo]

My aim was to stroke it to a 2.0L and then add a MP62, Plus adding new rod's, clutch, brakes etc. "waits for money to be saved up"

[Mokesta]

Turbochargers do not consume any power and in fact, actually use the heat and pressure of the exhaust, which is usually wasted energy, to produce boost so they are inheritantly more efficient.

Actually that is not true Benny. The fact that the turbocharger uses exhaust pressure and flow to compress and pump the air intake charge means that the engine is loaded by the turbocharger and is therefore a parasitic load....and when in positive pressure the parasitic power consumption between a supercharger and a turbocharger become somewhat closer. However, when the engine air intake is in vacuum the parasitic load of a turbocharger is substantially less than a supercharger.

Regards,
Danny

However, the losses using a turbocharger at high boost levels are far less than the losses incurred by a supercharger.
Superchargers ALWAYS use power, even at low revs, but turbochargers do not.
In relation to each other, turbochargers consume far, far less power than superchargers do.

What you also forget Danny, is that a lot of the rotational force of a turbocharger is not caused just by exhaust pressure, but by exhaust heat, and it is this heat that actually causes most of the rotation of the turbocharger impellor.
If not used this way, the energy in the heat of the exhaust is just wasted.
Boyle's Law says that an increase in the temperature of a gas will also mean an increase in pressure, and it is the heat generated by the exhaust that causes this increase in pressure which turns the impellor.
So with a turbocharger, you do get something for nothing!

He he he ... I bet if I put a turbo charger in an oven and heated it up ther impeller wouldn't turn. Heat on its own is the most useless form of energy.
Fuel burning with oxygen in the cylinder creates heat.
The heat is directly related to pressure when the volume is constrained. {Insert gas equation name here to appear smart }
The pressure drives the piston.
Then, on the exhaust stroke the piston drives the gas (still at pressure but lower than at TDC) out of the cylinder and into the exhaust.
If there is a restriction in the exhaust, say a turbine wheel turning slower than it wants to because it is connected to a compressor wheel that is busy pumping, then the piston must push harder to expel the exhaust air.
Yes there is resdual pressure in the cylinder at the end of the power stroke that we can extract more useful work out of, but as we do, we load up the piston on the exhaust stroke. You have also lost the ability to tune the exhaust so that active scavenging occurs.
You would only be getting something for nothing if you were using the exhaust gas velocity for thrust.

M