Jaycar Fuel ratio Meter, I built one!

Gannon · Post by **Gannon** » Fri Jul 13, 2007 6:54 pm

It came thisarvo so i soldered it all up and temporaly installed it, and it worked.

KC5195 at Autospeed.com

Only thing is, it needs calibrating, and i also believe that my o2 sensor is a bit old.

But it gives an indication of my fuel ratio, richer when accelerating, lean when decelerating.

just have to mount it somewhere.

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Sat Jul 14, 2007 5:28 pm

What are you using as your O2 sensor?

fredsub · Post by **fredsub** » Sat Jul 14, 2007 6:02 pm

Suparoo wrote: just have to mount it somewhere.

I had mine mounted in a cut slot in the plastic that overhangs the speedo cluster.leds pushed thru the slot. That way you can see them directly ahead;)
wired to the O2 sensor that sits behind the turbo. O2 sensor was a generic one.

steptoe · Post by **steptoe** » Sun Jul 15, 2007 11:33 am

those kits must be getting better, I have had trouble getting these things to work after putting them together according to instructions. WELL DONE !!

bluesteel · Post by **bluesteel** » Sun Jul 15, 2007 11:51 am

fredsub wrote:I had mine mounted in a cut slot in the plastic that overhangs the speedo cluster.leds pushed thru the slot. That way you can see them directly ahead;)
wired to the O2 sensor that sits behind the turbo. O2 sensor was a generic one.

thats exactly how i mounted mine too

same for the knocklink sitting next to it

discopotato03 · Post by **discopotato03** » Sun Jul 15, 2007 2:35 pm

Calibration is everything with those things and they usually only work over a narrow AFR range .
The people who tune engine management systems properly need true wideband 02 probes sometimes known as UEGO (Universal Exhaust Gas Oxygen) . I'm no electronic tech head but the more recent "pump cell" type probes were the breakthrough for reasonably cheap fast accurate sensing .
Out of time now but the Tech Edge site is a great read for the truly technically minded and they are based in Canberra .

Cheers A .

mroberts · Post by **mroberts** » Mon Jul 16, 2007 2:13 pm

For a basically stock car, they are a valuable diagnostic tool - I had one in my old turbo porsche, and yeah, you wouldn't tune from it but it was very useful to know whether things were working as they should be.

Gannon · Post by **Gannon** » Mon Jul 16, 2007 5:33 pm

Im using the factory o2 sensor, but i plan on getting another, a 3 wire one prehaps.

It still needs calibrating (ive turned the trim pot fully down but still cant get it to centre on the gauge) or maybe its running rich all the time.

I plan on drilling 10 holes in inderside of the dash surround and mounting them above the multifunction display.

Whats knocklink ?

bluesteel · Post by **bluesteel** » Mon Jul 16, 2007 10:02 pm

knocklink is a 5 led setup connected to the knock sensor, and tells you when the engine is about to knock/knocking (pinging)

Gannon · Post by **Gannon** » Mon Jul 16, 2007 10:39 pm

Sounds sweet, is it hard to build?

steptoe · Post by **steptoe** » Wed Jul 18, 2007 11:10 am

I seen a diagram for this that uses the knock box out of a VN Bommodore, got it somewhere in a Zoom mag

Ben · Post by **Ben** » Wed Jul 18, 2007 9:23 pm

I think I might have that Zoom article here somewhere too...

Wouldn't be hard to nut out a circuit based on a piezo sensor though...

Gannon · Post by **Gannon** » Wed Jul 18, 2007 10:51 pm

ive been doing a bit of reading on the subject and it isnt as easy as it sounds.
A simple amp and bar graph driver wont do the job of detecting knocking very well. it will only show overall engine noise. You need a device to filter out the knocking frequencies

discopotato03 · Post by **discopotato03** » Thu Jul 19, 2007 9:26 am

Yes and to be specific to the EA82T that probably means the "knock box" from an early 3 plug RX turbo .

Cheers A .

bluesteel · Post by **bluesteel** » Thu Jul 19, 2007 9:54 am

ive got one of these, bought it second hand and pulled it apart to install just abouve the cluster

VL400 · Post by **VL400** » Thu Jul 19, 2007 11:09 am

Knock sensors use a band pass filter to tune to the knock frequency. The frequency is mostly dependant on bore size so its hard to just use parts from another engine. Still works but the sensitivity is reduced.

The V6 commodore uses a knock sensor but the V8 does not (only HSV). There is a piezo sensor on the block and a filter inside the memcal that outputs a logic low when knock is detected. Its fairly easy to make your own standalone knock monitor using these parts but dunno how well they will work on a subi.

Would anyone be able to scan the zoom article and post it up?? Would be really interested in that as have never seen it.

Gannon · Post by **Gannon** » Thu Jul 19, 2007 4:48 pm

I was looking at autospeed.com, and they said just stick a microphone pickup to the block and listen with headphones while driving, sounds easy enough