[Diy_efi] DIY-WBO2 circuit improvement suggestion

William Shurvinton shurvinton at orange.net
Tue Jun 18 15:19:24 GMT 2002


Ummm A wirewound resistor generally has a constant resistance. Power
=Vsquared/R.

A heater coil is more light bulb than resistor. Cannot comment on how
commercial units drive heater as I haven't studied that area at all, but a
step up is not out of the question. Well designed switchers are not noisy.
However designing them is an art.

Bill
----- Original Message -----
From: Perry Harrington <pedward at apsoft.com>
To: <diy_efi at diy-efi.org>
Sent: Monday, June 17, 2002 7:23 PM
Subject: Re: [Diy_efi] DIY-WBO2 circuit improvement suggestion


> The heater is a coil of resistive wire, correct?
>
> Well, let's assume it's a 15W wirewound resistor for argument.
>
> If you're pumping 10v at 1.5a into it, it's 15w.  If you pump
> 5v at 3a into it, it's still 15w.  A wirewound resistor will
> follow power dissipation, not current.  So why wouldn't the
> heater do the same?
>
> Gar is always talking on about how commercial systems work down
> to 6v. I would doubt, due to noise, that they use a step-up
> switcher for powering it, so they HAVE to pump more current at
> a lower voltage into it.



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