MAP and Boost gauge

[gotboost3]

ok guys a little confused my map readings through my aero are always diff then what my mechanical boost gauge reads....at idle i get 20.1 vac on the aero and the boost gauge reads at 18.5 vac.....why is this? could it be a flaw in the line running to the gauge?

[minichopper6hp]

mechanical is always more accurate than electric gauge.

FWIW, i see straight 20 in hg when im at idle.

[gotboost3]

i get 19 is that normal?

[minichopper6hp]

yep, perfectly.

[Sabrewings]

mechanical is always more accurate than electric gauge.

That's way too vague. It depends on who makes it. The factory MAP sensor is very accurate, and I'd be inclined to believe it over any aftermarket gauges.

[minichopper6hp]

Electrical gauges have too many variances

[Sabrewings]

Electrical gauges have too many variances

Again, it depends on who makes it. A quality electrical gauge is just as accurate as any mechanical gauge. Any variances in the system voltage are accounted for with voltage regulators. Here's a hint, no gauges on the aircraft I work on are mechanical and they're accurate to within a thousandth of a percent of their range. Moste electrical gauges these days use air core motors which are more precise in their movements than mechanical gauges.

Autometer makes awesome electrical gauges that are 100% as accurate as their mechanical brothers. GM's OEM senders are just as accurate, with the PCM being the "gauge" and it definitely has its own electronics to handle any electrical instabilities.