Re: Eram

[Joel Marion <zeitguy@xxxxxxxx>]

Am I dense (pun intended) or would driving the car forward create this
kind of air pressure much more cheaply?

> - --- those not interested in E*ram talk can skip the rest of the post ---
>
>
> About the infamous e*ram, unless you have your A/C at max, your 500W
> high beams on, your rear window defroster on and your megawatt stereo
> blasting at 130 dB spl, etc, etc, if it only draws 30 A of current, then
> the alternator will be powering it since it has enough capacity.  30A at
> 14 volts is roughly 420 watts, which is about 1/2 horsepower.  So
> depending on the efficiency of the alternator, the power lost driving
> the alternator while the e*ram is running is about 1 hp (assuming about
> 50% alternator efficiency).
>
> If the E*ram is capable of a 5hp increase on a 200hp engine (that's a
> 2.5% increase) then it means that the manifold pressure is being
> increased by roughly the same percentage, or ~0.35 psi, plus 0.05 psi
> more to account for the increased alternator drag.  So for the E*ram to
> work it must be capable of boosting the intake pressure by at least 0.1
> psi (for a net gain of 0) to about 0.40 psi (for a 5 hp gain in a 200 hp
> engine).  Just food for thought (and assuming it only draws 30A of
> current).  I'll let somebody else decide whether it really is capable of
> these kind of boost pressures or if a hampster-powered unit would work
> better.
>
> Luis Marques
> '97 328i
>
>
- --
_______________________________________
Joel Marion, Principal mailto:zeitguy@domain.elided
Zeitgeist Artifacts, design services
http://www.zeit.com
916.682.9577
916.682.8953 fax

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