atsturbo

I am not sure why you are debating my math numbers. IF your blower uses 58hp we can assume it is:
58 X 175 or 200=10150 to 11600 divided by 14.5 psi = 700-800CFM. Using a density ratio of 1.5 (assuming a 75% efficient blower) you have a 467CFM to 533 CFM NA motor. With a redline of 7000 RPM, we then know you have an engine:
467 to 533 x 3560/7000rpm =237 to 271 CID. If that same blower is on a 350 SBC, it would be 350 X 7000/3560=688 cfm. 688 X 1.5 density ratio is 1032 X 14.5 psi divided by a 200 factor would be 75hp. If we used the 175 factor it would be even more hp lost.
The SBC and 5.0 are the two most popular blown motors, so people want to know how much crank power they are losing. If you have an engine that makes 550 flywheel hp on a dyno with a crank driven blower, and the blower is taking 75 hp tp turn it, then you are actually making 625 hp but the crank losses are 75. The 550CID engines running the Procharger @ 25 psi are using 200 +crank hp to turn them.

foxman

What ever happened to the Genom project 8?

globi

Good point. I wonder why Geoff Knight and Richard Paul don't consider a joint venture?

globi

I wonder whether someone came up with a hydraulic or an air driven supercharger?

How?
Instead of a flywheel generator you'd have an air pump. Since the engine is an airpump already, you'd install a compression retarder and a valve and you pump air into a tank everytime you hit the brake and therefore store braking energy. At WOT the pressurized air in the air tank would drive an airmotor which in turn drives the supercharger.

Why?
* Because you could still use regenerative braking.
* There's no parasitic loss nor is there any increased back pressure which means power will higher with less boost.
* The supercharger would only be used at WOT and therefore not increase fuel consumption at normal driving conditions.
* The supercharger can generate more pressure at low rpm since its drive is independent from the crank rpm. Therfore a more efficient and lighter compressor (centrifugal or axial) can be installed and still generate a drive shaft terrifying low end torque.
* An intercooler can be installed since the supercharger can be placed before the throttle plate. With an intercooler the efficiency or power would even further go up since the cooler air will require less compression work.
* Storing pressurized air would probably use less weight than storing electric energy in batteries.
* An air tank can be charged million times.
* Hardly anyone drives at WOT for longer than maybe 20 seconds therefore no giant airtank is required.

GeorgeH

iTrader: (2)

The air tank required to store that kind of energy would be quite large. Think what kind of tank you need to drive an air tool for 20 seconds, and then think about how much more air would be required to drive a supercharger. Of course, you could go with a high-pressure tank, but then you'd have to figure out how to generate those pressures during regenerative braking. Then you have the whole bomb thing.

If you could figure out a way to store the air, why not bypass the supercharger altogether? If you have a source of pressurized air, why not just blow it straight into the intake manifold at WOT (along with the required extra fuel, of course)?

Thinking of this, I'm sure it's been thought of before. If it worked we'd all have little pressure tanks in our trunk we would charge up before we leave for the day, and then "spray" the air when that STI rolls up. I'm sure the reason people do this with NOS as opposed to air is the energy density - you just couldn't get enough air in your trunk to last very long.

Liquid oxygen, anyone?

globi

Actually I thought about this too. This would basically be a jet pump, but jet pumps for some reasons have a very low efficiency (Something like 20%). And I'm actually not even sure to what level you can even generate pressure with a jet pump.

Ok let's do the math: You'd maybe need 5kW for 20 seconds which would mean 100kWs. According to the compression ratio it should be able to generate around 10 atm. Work is pressure times volume (simplified). So in order to generate 100kWs you'd require a 100 l tank. Oh well, it's bigger than I thought.

But if you had a turbocharged car, you could simply use the pressurized air to bring the exhaust wheel up to speed and you sort of end up with the same concept, but you'd need less energy.

Or if you had a hydraulic pump connected to the flywheel you could generate much higher pressures and have a much smaller tank. But I don't say that an electric supercharger might ultimately still be the superior solution.

I think the reason why we don't have it, is because regenerative braking is something fairly new and no matter how you do it, it simply makes the car more expensive. Now ordinary Hybrids have the benefit of making a car far more efficient and a hybrid supercharger wouldn't really make it much more efficient but more powerful. It'd be something inbetween and so far there wasn't a market for it, since buyers of sportscar don't really care much about fuel efficiency.

Well with liquid oxygen you wouldn't just burn fuel, but I guess you're aware of it.

atsturbo

Dont let my reply stop you from imagining additional ways to make an AP supercharger (auxiliary powered). As the previous post states, the tank would be enourmous for a 10-20 second run. This is because of the need for more pressure and airflow coming out of the tank than what is going into the engine. The formulas for determining power to drive any supercharger is the same:
(PSI X CFM / 229) /EFFICIENCY OF THE BLOWER/FRICTION LOSSES
So a 13B engine uses the airflow of a 3.9 liter engine. That translates to:
3900/16.6 = CID X 7000 (RPM)/3456 = CFM @ 100% EFFICIENCY. THE ENGINE IS ABOUT 90% EFFICIENT, SO CFM/90 = 430CFM.
Lets do the math for 10 psi with a 75% efficient compressor. The density ratio at 10 psi with 75% AE = 1.5, so 430 x 1.5 = 645 cfm @ 7K @ 10 psi
10 x 645 = 6450/229 = 28hp. No compressor is 100% efficient, so 28/.75% = 35hp/.05% friction losses = 37hp.
The typical air tool is 1-3hp max, so you would need a serious air motor as well as a tank (even with air compressed to 4000 psi)
There have been several good designs in the past. Turbonique used rocket fuel monopropellant to run their turbine/superchargers with unbelievable results. Other than the several dozen deaths associated with explosions and little problems like that, the design was good for the late 60's (You know I am being sarcastic in this sue-anyone age) I owned about two dozen of their units before nearly killing myself trying to power one with steam. A tank ruptured at 600psi. Fortunately, it exploded in the opposite direction of me or I would have been deep fried. I sold all the units immediately before I could kill myself :-)

globi

atsturbo, I have never heard of Turbonique but it certainly sounds exciting.
Actually I think 4 psi boost would be enough to generate an extra 50HP (since there's no parasitic loss). I still don't see why you need to anticipate an airflow of a 3.9 liter engine, since the engine would displace 1.3 liter per revolution if it had a volumetric efficiency of 100% (which is the same as a 2.6 liter otto engine). So the air consumption would then be 151.6 l per second at 7000 rpm (1.3l*7000rpm/60). 4psi is about 27400Pa an volume times pressure is power(27400*0.151=4.2kW) (assuming isochor compression which it's not, but it's not too far from adiabatic compression). If you had an efficiency of 70% you'd end up with a power requirement of 6kW which is roughly 10HP. I wouldn't take the power needed to generate the air pressure into account, since it's supposed to be generated when you brake anyway. It just saves your brakepads.
(I'm not very familiar with English units so I use SI-units.)
But as I acknowledged before you need a larger tank than I originally expected and I agree electrically powered might ultimately the better way to go. Well actually a flywheel can still store more energy per weight than a battery. And a flywheel might also give one some interesting stories to tell, granted he or she ever gets old enough.

globi

Not that this has anything to do with a rotary engine, but this might be an excellent application for an electric supercharger:
http://popularmechanics.com/automoti...ession_engine/

globi

So, has anyone ever ended up installing one of those ESCs, I wonder?

SureShot

I was surprised that the RX-8 used electric power steering.
I guess practical electric boost is just a matter of engineering.

rotorocks

The reason the Nitrous is used is because because essentially you deliver Oxygen to the engine, but in a safe "capsule". At around 400F (or is it C)? Nitrous Molecules Break down releasing all that Oxygen.
Oxygen on it's own is going to blow up along with your car and you in it.

sosonic

http://www.boosthead.com/ seems legit. Anybody try this on an RX-8?

Based on the theory, it should work. I don't see any reason why you can't use electric power for short bursts.

The real issue would be the type of supercharger, boost level, HP gain, and cost. Since he using a centrifugal supercharger, I wonder how fast the boost would come on. If belt driven, there should be a little delay, like turbo. But for an electric driven centrifugal supercharger, would it boost faster?

globi

Yes it would boost faster (than a turbocharged engine). Actually Borg Warner is working on a turbocharged system in combination with an electric supercharger in order to reduce turbolag - such that a downsized turbocharged engine develops the same torque curve as an engine with a large displacement.
http://www.turbos.bwauto.com/de/products/ebooster.asp
(Sorry I couldn't an English link).

pdxhak

iTrader: (2)

I see atsturbo has not posted since 2004. Did he ever get an electric SC working on the RX-8?

Renesis_8

we need another planet with different air compositions for the RX-8 to develop more power with its 1.3 liters..... 50%nitrogen/50% oxygen?

RX8PDX

I read an article about the proposed RX8 mazdaspeed a while ago, and it was supposed to have an eletrically assisted turbo, to remove lag.

Marx8nka

in english
http://www.turbos.bwauto.com/en/products/ebooster.asp

Viich

So, is someone running one of these suckers yet or not?