I understand how the mechanical boost gauge receives the boost signal through a vacuum line.

But how does an electric boost gauge receive its boost signal to read on the gauge?

Thanks,
James

Through a sending unit that mounts under the hood. The line from the manifold connects to the sending unit which outputs an electrical signal to the gauge.

So, there is a vacuum line to the sending unit, then that unit sends the electrical message to the gauge?

Are these more accurate?

Yes that is how they work. As for accuracy, it is probably equal as long as they are decent quality gauges, the electrical type will have a faster response because there are no moving parts that have to react to the changing pressure/vacuum as in the mechanical one.

...the electrical type will have a faster response because there are no moving parts that have to react to the changing pressure/vacuum as in the mechanical one.
If I'm on the same page as what Mulder was trying to say, the additional response delay in mechanical gauge theoretically has to do with the fact that the measuring membrane/device/bourdon-tube is located farther away from the measured chamber.

Between the measured chamber and the measuring device, the vacuum hose contains a finite amount of air, which, is not 100% incompressible. Add to the fact that the vacuum hose itself does not have infinite stiffness, and you get a "flexing-like" behavior between the source and the measurement.

However, given the relatively small amount of air in the vacuum hose, and considering that human eye probably have a limited bandiwdth of about 25Hertz, I would say that the difference due to this phenomena is imperceptible.

The above is true. However what I was referring to is that the actual meter movement in the mechanical gauge is the bourdon tube itself, which has a certain response time to changing pressures. The electrical gauge has an electronic transducer as its sending unit, with no moving parts, and the electrical meter movement responds much faster than the mechanical one.

The above is true. However what I was referring to is that the actual meter movement in the mechanical gauge is the bourdon tube itself, which has a certain response time to changing pressures. The electrical gauge has an electronic transducer as its sending unit, with no moving parts, and the electrical meter movement responds much faster than the mechanical one.
Ah, I was wondering whether you were considering the air in the hose or the dial+bourdon tube mechanism.

Imho, if we consider only analog gauges for both mechanical and electrical, the response time of the needle of the electrical gauge may or may not faster than the needle + bourdon tube of the mechanical gauge. Suppose both have needles with equal rotational inertia, and suppose they have equal energy losses (e.g. same pivot friction), then whether the needle of the mechanical or the electrical gauge is faster depends also on how much force is available from the motor, voice coil motor, bourdon tube, or whatever it is that drives the needles. Perhaps a good quality mechanical gauge is built with a very light & responsive bourdon tube + needle mechanism, while a mediocre electrical gauge could be built with an underpowered motor & heavy needle.

Having said that, I agree that a properly designed electrical boost gauge will have a higher potential in achieving a fast response compared to a properly designed mechanical boost gauge; not that faster is necessarily more desirable imho.

Ooooo-K :)
I think we've gotten way too technical beyond the basic answer to the question that was asked ;)
Anyway the electrical gauges I've seen have been more responsive and less "damped" than the OE Lamco mechanical one that I have. Which as you point out isn't necessarily either a good or bad thing. I don't mind the way the Lamco gauge behaves.

Originally posted by Mulder
Ooooo-K :)
I think we've gotten way too technical beyond the basic answer to the question that was asked ;)
Agreed. :lol:
My apologies to jroberts for getting a bit off-topic.