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More On The E-Ram Electric Supercharger
Recently, I received an e-mail from a Mr. Mark Kibort <firstname.lastname@example.org>, concerning the E-Ram electric supercharger. His company, E-Racing, makes and sells this device. He apparently was not happy about the treatment I gave the E-Ram in the preceding page, and proceeded to tell me so. Before I respond to his e-mail, I'll print it here in its entirety.
Now, it's my turn. "Once more, from the top..."
Okay, so on the one hand, the E-Ram is supposed to draw 40 amps, as pictured. On the other hand, the E-Ram is supposed to draw 50 amps, as pictured. Which is it?
Also, what black adapter? The version I got only had the K&N filter. There was no black adapter you mentioned. For those readers who are wondering what "black adapter" I'm talking about, it's a little cone that goes on the flat part of the E-Ram fan wheel, where the bolt sticks out.
Are you sure what you're talking about? "Bite"? If you mean to tell me that the E-Ram is powerful enough to draw a partial vacuum with the K&N filter installed, you're not succeeding. If you mean to tell me that the E-Ram actually needs the aerodynamic smoothing provided by a inlet cone, you're not providing much of a convincing argument.
Finally, did you ever consider that the numbers I got were with the K&N filter installed?
Is that so? Well, let's use a little something I like to call the Law of Atmospheres. This is something I'm using from college thermodynamics, so it's not something I just pulled out of thin air, either. Basically, it states that:
This law states that a given volume of gas at a given temperature and a given pressure at state 1 will occupy a different volume at a different pressure at the same temperature (This is actually a simplified explanation, but will do fine for my reply).
Now, consider 211 cubic feet at 15.7 psia and at 70 degrees Fahrenheit (530 degrees Rankine for absolute temperature). Now, keeping the temperature the same, and dropping the pressure to 14.7 psia, the volume increases to:
So, in other words, to flow 211 cfm at 1 pound of boost (15.7 psia, or 1 psi over atmospheric pressure), you'd need to flow 225.4 cfm at atmospheric pressure.
Unfortunately, the E-Ram can't even do that. It's best "boost" for a 2.5L V-6 at WOT is just barely enough to budge a boost meter's needle. This pitiful performance is far below the 1 psi needed to substantiate the E-Ram claim to fame.
No, not really. Let's see what the E-Ram actually does, shall we?
Given that the E-Ram weighs 2.5 pounds, and it has 8 fan blades with each blade having 0.75 square inches of area. Since it's the moving fan blades that actually work to compress the air going through the E-Ram to generate air pressure, thus generating thrust, we'll limit the evaluation to just the fan blades. Now to levitate itself, the E-Ram would have to develop 2.5 pounds of thrust to overcome its weight, right? Let's see...
Note that this pressure is able to just barely levitate the E-Ram. This leads to the other part of the questionable claim put forth by Mr. Kibort. If this E-Ram is actually able to flow 400 to 500 cfm of air at atmospheric, then it ought to not just levitate itself, it really should violently try to fly up into the sky. Why? Consider this:
One cubic foot of air weighs about 0.0753 pounds. At 400 cfm, that E-Ram would have to move 30.1 pounds of air every minute, or 0.502 pounds per second. Let's use a pipe with a diameter of 2.7 inches (such as the effective pipe size Mr. Kibort is going to use later on). To flow 400 cubic feet per minute through such a pipe, one would have to pass that air through a cross-sectional area of 0.040 square feet. This gives a velocity of that 400 cubic feet of air per minute, through that 0.040 square foot restriction, of 10060 feet per minute, or 167.7 feet per second.
Using physics momentum and impulse equations, one can see that:
Now, assuming t = 1 second (since it would take 1 second to make 0.501 pounds of air move, using the above numbers), we get:
Now, keep in mind this thrust is only due to conservation of momentum from moving the air mass through the E-Ram. This does not take into account the relatively static mass of air behind the E-Ram, from which the moving mass is able to push against, therefore creating pressure at the exhaust of the E-Ram. Nor does it take into account the partial vacuum developed at the inlet of the E-Ram. We'll assume, for the sake of argument, that the E-Ram is able to affect air pressure within 2 cubic feet of the inlet and exhaust. Allowing for the energy imparted to the moving air of about 600 joules (Anybody who ever took college physics ought to be able to get that figure from the mass and velocity of the air), and considering that this energy is being dissipated in the form of pressure only (no heat losses), we find that the E-Ram is able to generate a 0.7 psi boost. Now, multiply that by the 6 square inches of the fan blades, and you get 4.54 pounds of thrust due to pressure differences.
Hm... 4.54 pounds due to pressure, and 2.6 pounds due to momentum conservation... That's 7.14 pounds of total thrust acting against a 2.5 pound object. That's a thrust-to-weight ratio of 2.85! This thrust would tend to make the E-Ram take off for parts unknown rather than just levitate.
Alas, the E-Ram is just barely able to levitate...
Ah, so the air filter and the intake piping don't provide any restriction, either? These are also non-issues, is that correct? In case you've forgotten, those items are also present before the throttle plate. Those items will also hurt intake performance, or else there wouldn't be such a market for performance aftermarket induction tubes and high-flow filters.
How can you say that the E-Ram flows as much when off, as a 2.7" diameter pipe? How long would that pipe be? How much airflow did you use to determine your assertion? You do know that flow ability is related to airflow and pipe length, right?
No, if my E-Ram did draw 40-50 amps, it would quickly turn itself into a hot pile of molten slag. Passing 40 amps through a resistance of 0.9 ohms (such as the E-Ram's motor coil resistance) would give a power draw of 1360 watts. Your typical high-performance audio amp is only rated at 500 watts. A blow-dryer on high draws about 1500 watts. Add this to the fact that there really is no good way that the E-Ram is able to shed the heat generated by this much wattage (remember that the amp has a butt-ton of cooling fins and a large metal heat sink, and that the blow-dryer is constantly passing air past those spaced-out heater coils that consume the 1500 watts). The E-Ram would very quickly fail due to overheating, and would probably cause a good deal of damage to the electrical system of the vehicle that had this device installed. Thank God, in this case, that the E-Ram only draws about 15 amps.
About your product's claim to fame with racing: So what? If your product doesn't perform (which it doesn't), why should I care what application it's used for?
Let me get this straight. A close friend of yours did the "independent" test that supposedly proves your E-Ram's performance gains. Oh, yeah, that really sounds objective... Not.
Also, how am I supposed to relate your Porsche engine numbers? Was this E-Ram alone providing your gains, or was it (as I suspect) an intake tube better than stock, that the E-Ram was installed into? Where's your dyno chart "proving" this claim of yours?
Okay, I will. By the way, you do have a point. I was actually mistaken about the amount of power it takes to boost 212 cfm of air to 1 psi. Turns out it actually takes about 3.9 HP, and not the 1 HP I claimed earlier. So, let's see...
3.9 HP... That is equivalent to about 2900 watts. At 13 volts DC, that turns out to be 223 amps! Remember, this is merely the power needed to boost 212 cfm of air to 1 psi over atmospheric. I haven't even touched on the power consumed by the E-Ram in the form of mechanical and electrical losses!
I look forward from Mr. Kibort's reply to the above information...
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|This page last updated 20 April 2010.|