Quote:
Originally Posted by RPIpower
Cool. Could you explain to me how a belt driven accessory will help with gas mileage over something that is being spun by exhaust gasses? Im just curious to see your theory on this because over the several years of doing this I have never seen this happen.
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There are different types of superchargers out there and some operate differently so for all intensive purposed we are taking a roots type supercharger which supplies low end HP and torque. A twin scroll or screw would be even more efficient.
Easy with a roots type supercharger power is instant, also linear therefore; one does not need to "Mash the gas" or bring up the rpm dramatically in normal driving to accelerate quickly.
Like I said before with my RSX I was making more power just off idle at 2500-3500 then my stock power peak N/A at over 200 WHP not HP. With power that low in the RPM band and a rpm band of 9K that is a big difference in drivability and fuel consumption. I guess I have a example here because I went from normally aspirated to supercharged. So I know my engagement points and how much throttle I need to use to get me to the speeds I want to go. NA usually I have to lay on the pedal and get into the higher rpms to get the car to accelerat to the speed I want it.
I don't need to use excessive fuel or even open up my vtec valve train to enjoy power that once was only accessible at 8-9K rpm with vtec and injectors working at 85%.
Turbo's have to be spooled to reach optimum efficiency at a certain rpm. Turbo's don't start at 11 psi they have to gain boost. That boost is gained by feeding more fuel and air building pressure. Which what consumes more fuel.
Superchargers are at optimum efficiency instantly and throughout the useable rpm range they don't have to build boost and don't use a lot of fuel to get there. Hence more fuel efficient. Also one is not on the pedal to get the car to the rpm where the performance they need. As you mentioned earlier that Superchargers are always on boost which is not true they have a bypass built into most units. They are always spinning just as fast as the motor and pulley is setup to run if that is what you meant, but they are not always on boost.
Not only are Superchargers better for street driving the acceleration is much more crisp and precise there instantly when you need it. Turbos are great and don't get me wrong it just takes a bit to get them going due to lag and even the Sky RL has lag. That lag can cost you that spot in traffic or not being able to pull out.
Now if one is looking for total top end max power then turbo is the way to go, but for normal boosted street driving SC is the way to go. Instant boost, power low RPM off idle performance and very little maintenance.
The only turbo charged car I would say that could compete with the instant response of the roots supercharger would be the Twin Turbo charged RX7 93-96 Those are insane, but again the 1.3 liter wankel or 13B rotary motor is itself a supercharger. So you would say that it is tripple charged.
Don’t get me started on twin charging which in this case would be a supercharger and turbo working in conjunction. The best of both worlds!
Here are some links to look at.
Supercharger - Wikipedia, the free encyclopedia
The volumetric efficiency of the roots type blower is very good, usually staying above 90% at all but the lowest blower speeds. Because of this, even a blower running at low efficiency will still mechanically deliver the intended volume of air to the engine but that air will be hotter. In drag racing applications where large volumes of fuel are injected with that hot air, vaporizing the fuel absorbs the heat. This functions as a kind of liquid after cooler system and goes a long way to negating the inefficiency of the roots design in that application.
Turbocharger - Wikipedia, the free encyclopedia
More reading:
Volumetric Efficiency - HSTuners
Unlike a turbocharger, a supercharger has no turbine to be an impediment on exhaust gas flow. Because of this, the supercharger maintains a
positive pressure across the engine with the intake pressure higher than the average exhaust pressure. With this positive pressure differential across the engine, the volumetric efficiency is almost always increased. A VE of up to 110 percent is possible with a supercharger (259).