How would you like a $10 digital A/F meter?

douglas vincent · Post by **douglas vincent** » Tue Jul 20, 2004 6:19 am

I can expect the flames now but I will live with them.

Since I installed the nitrous I wanted to be sure I was never running anywhere lean so I needed a A/F meter to monitor my oxygen sensor. I check out Ebay but I didnt want to spend the money and wait around since the nitrous was installed and running. So after talking to my brother, we just decided to hook up my Harbour Freight $10 multimeter. Its digital, its lighted, it works and its $10. To hook it up, you just run a wire from the red wire (on my car) on the oxygen sensor (above the wire connection) to the red input and the black input is just grounded.

Here is the unit I use.
http://www.harborfreight.com/cpi/ctaf/D ... mber=90939

This one should work as well for $4.99
http://www.harborfreight.com/cpi/ctaf/D ... mber=33499

THAWA · Post by **THAWA** » Tue Jul 20, 2004 7:01 am

why would you be flamed?

douglas vincent · Post by **douglas vincent** » Tue Jul 20, 2004 7:17 am

Cause I sometimes miss the obvious fuck up. But I try!

vrg3 · Post by **vrg3** » Tue Jul 20, 2004 5:26 pm

It should be fine as long as the meter has a high enough sampling rate and you don't put too much stock in the voltage numbers.

mTk · Post by **mTk** » Tue Jul 20, 2004 5:41 pm

THAWA wrote:why would you be flamed?

People tend to randomly dog on other's ideas here, i haven't yet pinpointed the exact combinations that cause it.

MK

evolutionmovement · Post by **evolutionmovement** » Tue Jul 20, 2004 9:21 pm

People tend to randomly dog on other's ideas here, i haven't yet pinpointed the exact combinations that cause it.

It does seem very random. Maybe there's some people that they just don't like the look of. Oh wait, this is the internet ...

Steve

BAC5.2 · Post by **BAC5.2** » Wed Jul 21, 2004 7:50 am

Sounds like a pretty solid idea if you can mount it cleanly (i.e. sacrifice the Multimeter and flush mount the LCD display in the dash somewhere with the electronics shielded.)

That'd be pretty slick.

douglas vincent · Post by **douglas vincent** » Thu Jul 22, 2004 3:16 am

I actually have it zip tied to the drink holder for now. I havent gotten around to cutting up the multimeter for the lcd as I need to go buy another one first.

This multimeter seems to sample twice a second, which i think is slow for a real A/F meter.

THAWA · Post by **THAWA** » Thu Jul 22, 2004 3:26 am

well you could also build one yourself and have it react faster

http://bbs.legacycentral.org/viewtopic.php?t=15639

I think including the extras i bought i spent 15 dollars. If you have leds you can do it for under 10.

vrg3 · Post by **vrg3** » Thu Jul 22, 2004 6:16 am

Hmm, if it's only updating its display twice a second you have to wonder whether or not the sample you're seeing is an integral over half a second... if it is, the number is pretty much meaningless, unfortunately.

THAWA's suggestion of using an LM3914 is a pretty good one; that's what almost all commercial "air/fuel ratio" gauges use.

An LM3914 is even easier to wire for this purpose if you only use 8 LEDs; the internal 1.25v reference suffices in that case so you don't have to program the scale.

THAWA · Post by **THAWA** » Thu Jul 22, 2004 6:26 am

yeah i really ought to finish making that stupid thing

eastbaysubaru · Post by **eastbaysubaru** » Thu Jul 22, 2004 6:59 am

Please do

-Brian

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How would you like a $10 digital A/F meter?

How would you like a $10 digital A/F meter?