Jaycar Smart Mixture Meter

[MearCat]

Has anyone purchased and installed the Jaycar Smart Mixture Meter? (Linky - This is new SMART version, not the original one from many moons ago)

Can anyone comment it's usefulness/accuracy? For $28, it looks like a great cheap alternative to A/F ratio gauges which do nothing but show the ratio (for much more $$). This has a lean-out alarm - a great feature!

I think Autospeed did a review on this at some stage too.

Edited January 18, 2006 by MearCat

[TTT]

unless you have a wideband 02 sensor, it's pretty useless.

anywhere below 4000rpm when in closed loop, it will beep constantly as it is always lean (at around 14:1 or something)

I bought one, built it and never installed it due to this reason.

I then gave it to a friend at work.

that $28 would buy a decent steak somewhere..

[GTRgeoff]

that $28 would buy a decent steak somewhere..

<{POST_SNAPBACK}>

HoooHooHooo, I like it

[MearCat]

anywhere below 4000rpm when in closed loop, it will beep constantly as it is always lean (at around 14:1 or something)

From what the Autospeed article says you can adjust at what point the display lights the red "Lean" LEDs. Perhaps this was not adjustaed accuractely in your case?

[TTT]

well think about it.

in a good tune, youd want your car to be at about 11.5 or 12:1 on full throttle.

and if it got to like 12.5:1 or 13:1 which is lean on full throttle, you'd want to be warned so you can back off right?

so you would tune it to show rich at anything bellow 11:1 and lean at anything above 12.5:1

but like I said before, at idle and cruise revs where you are in closed loop, below 4000rpm or whatever it is, the mixture is ALWAYS going to be over 14:1.

so it will be lit up like a xmas tree to show lean and buzzing it's arse off.

now... about this steak we discussed.

[MearCat]

Yes - I see what you mean. However - the kit has another adjustable variable (The voltage signal from the AFM) which you can set to signify when when the car under heavy/full load. When set up correctly, the buzzer will only go off when it's lean AND under load.

So yes the car is ALWAYS going to be over 14:1 when at cruise/idle/closed loop, but because it's not under load (ie AFM voltage is high) at the same time, the buzzer should not go off.

[TTT]

well maybe I shoul dhave clicked the link and read that first hey stupid.

back when I bought it it didn't have the "SMART" functionality.

this version may be a good buy.

But I still need my protein.

my $28 goes on steak.

[Sydneykid]

Waste of time and money, as is any device that relies on the standard lambda sensor.

The standard slow and narrow lambda sensor is exactly that, slow and narrow.

Narrow-----if the leaness exceeds 16 to 1 the standard narrow lambda sensor won’t see it, because it is outside its measuring capability. This means if you get a super lean condition (eg; fuel pump failure) you won’t get any warning.

Slow-----if the leanness happens suddenly (eg; fuel pump failure) the standard slow lambda sensor won’t respond quickly. This means you most likely won’t get enough warning to save the engine.

Buy a steak as GTST said, it’s better value and it won’t protect the engine any less.

Cheers

[MearCat]

Waste of time and money, as is any device that relies on the standard lambda sensor.

<snip>

So really, your also saying that the cars' ECU which relies on the standard sensor would wont be acurate in it's calculation of how much fuel to inject into the engine??

Surely this meter/device though would useful in detecting the "health" of the O2 sensor - say if the mixtures aren't being changed rapidly then the sensor would be on it's way out? Or to detect something like overfuelling due to eg. a problem with the AFM ?

[clayoth]

So really, your also saying that the cars' ECU which relies on the standard sensor would wont be acurate in it's calculation of how much fuel to inject into the engine??

That is sort of correct. The EGO sensor is only in use during closed-loop operation (idle and cruise) where the ECU is maintaining AFRs around 14.?:1 for fuel efficiency and good emmissions. It is sufficiently accurate for this purpose. Outside of closed-loop operation, the EGO sensor is not used and would be inaccurate and slow at mixtures away from stoichiometric point.

From Wikipedia...

The voltage produced by the sensor is so nonlinear with respect to oxygen concentration that it is impractical for the electronic control unit (ECU) to measure intermediate values - it merely registers "lean" or "rich", and adjusts the fuel/air mixture to keep the output of the sensor alternating equally between these two values.

This type of sensor is called 'narrowband', referring to the narrow range of fuel/air ratios to which the sensor responds. The main disadvantage of narrowband sensors is their slow response: the control unit determines the exhaust gas composition by averaging the high and low swings in the sensor's output, and this process creates an inevitable delay.

Edited January 28, 2006 by clayoth

[MountainRunner]

I agree, buy the steak. I put one together for a guy who was doing some tuning and he prompty realised it was junk and bought a good quality wide band unit for the appropriate $$$.

[MearCat]

Another thing I found out today was that the oxy sensor has different responses depending on it's temperature. The sensor doesn't actually start working until it reaches 350degC, at which point it starts conducting oxygen ions.

Has anyone got ideas on how long would it take to reach this temp?

[paulr33]

what gary is saying is the factory 02 sensor is used in closed loop mode, ie when you are plodding along in a gear and dont have much throttle applied. the ecu looks at the 02 readings to trim fuel and save fuel consumption.

its not used for wide open throttle, ie when you boot it the sensor is ignored.

it takes sometime upto 20 seconds for the 02 sensor to "show" the ecu whats coming out, ie you take off, 15 seconds later the 02 sensor goes "rich" as you've just started acceralting, the info is kinda useless 15 seconds later

[GTRgeoff]

15 seconds is a bit much Paul, they are a little quicker than that. We're talking a system that needs responses in the milliseconds but in truth the standard sensors (see cheap) aren't that good so the computers rely on open loop tables for open throttle or under load and use closed loop when at idle or close to, when there is little load.

They have a heater unit in them as well to help get to operating temp. How long it takes is not something I've troubled myself to discover.

Again, go the steak dinner

[TTT]

why is this thread still going?

factory o2 sensor only works when in closed loop (ie when cruising and not racing where you are concerned).

this device which is worth a decent steak works of the factory o2 sensor.

therefore by the powers of Chuck Norris, Vin Diesel and Mr T combined, I here by decide this device useless.

[ebola]

why is this thread still going?

factory o2 sensor only works when in closed loop (ie when cruising and not racing where you are concerned).

this device which is worth a decent steak works of the factory o2 sensor.

therefore by the powers of Chuck Norris, Vin Diesel and Mr T combined, I here by decide this device useless.

<{POST_SNAPBACK}>

Err - just because the O2 sensor isn't being read, it doesn't mean its not working, has vanished, or has turned into a steak.

Like has been said though - why bother? The factory sensor is barely adequate for its job (14's), and with undefined (or no) behaviour past 16..........

[TTT]

Err - just because the O2 sensor isn't being read, it doesn't mean its not working, has vanished, or has turned into a steak.

Like has been said though  - why bother? The factory sensor is barely adequate for its job (14's), and with undefined (or no) behaviour past 16..........

<{POST_SNAPBACK}>

this device lights up little lights depending on wheter the factory o2 sensor sees lean or rich.

so out of closed loop, it is going to see one thing.. I assume rich.

so lets say he has the boot in and at about 5500rpm which is probably 1500rpm out of closed loop, and the car leans out, This device is not going to report it.

mmmmmm steak.

[MearCat]

From what I understand about the device, it would report it though. There are two configurable settings (AFM voltage and Oxy Sensor voltage). So when he has the boot into it at about 5500rpm, the AFM voltage would be above the preset amount. And if the oxy sensor voltage rises above another preset amount, it's lean. When both preset amount are reached and alarm is reported.

The device or course wouldn't report it if you were doing 5500rpm but didn't have your foot down (revving slowly) and it went lean, but of course if you haven't got you foot into it, is it really as important to indicate a lean condition?

Also, whether the oxy sensor is being used in closed loop or open loop by the ECU, it will still report a voltage to the device. I don't think the device cares whether the oxy sensor can detect the differenc bewteen 14:1 or 16:1. All it needs to know it that the voltage is above eg 0.8V which is lean.

Edited February 1, 2006 by MearCat

[ebola]

unless you have a wideband 02 sensor, it's pretty useless.

<{POST_SNAPBACK}>

Waste of time and money, as is any device that relies on the standard lambda sensor.

The standard slow and narrow lambda sensor is exactly that, slow and narrow. 

Narrow-----if the leaness exceeds 16 to 1 the standard narrow lambda sensor won’t see it, because it is outside its measuring capability.  This means if you get a super lean condition (eg; fuel pump failure) you won’t get any warning. 

Slow-----if the leanness happens suddenly (eg; fuel pump failure) the standard slow lambda sensor won’t respond quickly.  This means you most likely won’t get enough warning to save the engine.

<{POST_SNAPBACK}>

Sheesh, go buy the thing then. It may provide interesting data, but it will be useless in preventing engine damage. If anything drastic happens, its slow. If anything big happens, the O2 sensor is undefined at 16. I *presume* that it reaches max voltage (and holds), but who knows.

Well, I think I've cause enough trouble. I wanna go home (did someone say steak?)

[Warpspeed]

I have a four dollar conversion kit that converts an R31 Skyline into a genuine R34 GTR.

If you believe that, then you will believe a cheap build it yourself Jaycar kit will read accurate air fuel ratios with a stuffed secondhand narrow band oxygen sensor, with no temperature compensation, and without any calibration.

It is like using a wooden school ruler to set up the clearances in your race engine. If you are building a ten dollar race engine it will work fine.

Bloody hell guys. If you want a decent measuring instrument, buy a real one. Spend the money and get something that works.

If you want the best, buy Autronic or Motec. If you have a crap engine, a crap air fuel meter will be quite o/k.

Edited February 1, 2006 by Warpspeed