Air fuel gauge

[gingerpaul]

Hi all. I've just upgraded the engine (Rover V8) in my kit car and will need to alter the fueling in the carb. I've got the set up kit and previously did it at a rolling road session. What I was wondering is whether I'd be better off getting an air/fuel gauge and driving on the road. If so can anyone recommend a gauge that's any good? There are lots available. The option of being able to plug two lambda sensors in would be a bonus as I have a pair of side exit exhausts.

Thanks in advance.

[stevieturbo]

If you have no ability to tune the carb for each side of the engine, then 2 lambdas isnt really needed.

There are a couple of units out there that can run 2 sensors, but they tend to be pricey. Might just be as cheap to buy 2 single widebands.

There are dozens of options really, just depends what you want to spend, and what sort of display you want.

With PLX you could get 2 controllers and one of their single displays.


Haltech also offer a dual wideband option...not 100% sure on display options though.

But there really are so many out there

[gingerpaul]

I was thinking something with a plain digital numerical read out. I don't really need anything with memories or modes etc. Just a simple indication of the exhaust gases at that moment in time. The smaller the gauge is the better. Being cheap would be a bonus, but not at the expense of it not doing its job.

You are correct that I can only alter the tuning for the whole engine rather than each bank so perhaps I could fit a second sensor in one side and wire them up through a switch to be able to switch between the two, or just look at one bank. This part of the criteria isn't important then.

[stevieturbo]

That isnt doable. If a sensor is installed in the exhaust, it must have a heater working.

So it should be wired to a controller at all times

Hard to say which option is cheapest.

The control units and sensors are all sort of evenly priced. The displays vary.

Cheapest option is a basic voltmeter and calibrate as needed.

Here is a source of some PLX stuff in the UK

http://www.gb-ent.com/index.php?option=com_virtuem...

PLX's website

http://www.plxdevices.com/

NGK also make a cheap unit which is very good.

Instructions for Haltechs dual unit. You could wire a switch to switch the output voltage to the display to switch between both sensors.

http://www.haltech.com/downloads/accessories/Halte...

Edited by stevieturbo on Friday 6th November 22:00

[eliot]

stevieturbo said:

That isnt doable. If a sensor is installed in the exhaust, it must have a heater working.

yep.

[fatjon]

And the wideband unit has to be free air calibrated for each sensor so you can't flip it between two sensors. Tech Edge do a dual wideband controller for V engines but it's pretty expensive for just getting a readout.

[gingerpaul]

Doesn't look like a goer then! I suppose I can always take the sensor out of one side and put it in the other. It's not a complete nightmare because they are on the outside of the car. It's a shame you can't just change with the flick of a switch though. Oh well.

Thanks for the information. I'll have a look at the recommended stuff above.

[Steve_D]

gingerpaul said:

Doesn't look like a goer then! I suppose I can always take the sensor out of one side and put it in the other. It's not a complete nightmare because they are on the outside of the car. It's a shame you can't just change with the flick of a switch though. Oh well.

Thanks for the information. I'll have a look at the recommended stuff above.

You can change with a switch but you will only be switching the gauge from the output of one Wideband controller to the output of another.
So you would need two sensors and their controllers
One gauge
One switch

If you have no way to adjust one bank against the other then a sensor in one side will tell you all you need to know.

Word of warning.....an AFR gauge can be very mesmeric taking your attention off of the road.

Steve

[blitzracing]

For setting up carbs you can get away with narrow band sensors, but the voltage change is pretty flat between 14.2:1 and 12:5 af ratio but it can be measured. I can vouch this works:

http://www.pelicanparts.com/techarticles/mult_air_...

[stevieturbo]

Or to save any fking about with building all that crap. Just use a cheap digital voltmeter.

But given how cheap widebands are, the only place a narrowband sensor has for engine tuning....well, it doesnt have any really lol

[blitzracing]

Tried reading a cheap DVM on the move, especially considering the way they jump about as they sample the voltages every .25 - 1/2 a second or so ? You cant ! If you dont like the complexity of that particular circuit then an audio VU LED meter can be made to work pretty well. Heres one I made earlier specifically for the RV8 lambda probes. (with different voltages to the "generic" ones): 4 green LEDS for lambda switching point, plus one orange LED for full power at 12.5:1 (with new probes as the reponse drops off with time). Theres no reason why you cant feed both probe outputs back to a switch so you can switch between banks, as long as you use good screened audio cable to prevent electrical noise. Or of course you could use stereo VU meters so you can read both banks at the same time if you want to be flash.

[stevieturbo]

Ive never had any problems with a voltmeter, and it would respond plenty fast on a carb equipped car.


But I really cant see why anyone would waste their timing cocking about with narrowbands, when widebands are so cheap.

[blitzracing]

stevieturbo said:

Ive never had any problems with a voltmeter, and it would respond plenty fast on a carb equipped car.


But I really cant see why anyone would waste their timing cocking about with narrowbands, when widebands are so cheap.

Depends what you call cheap really? Id agree about the voltmeter on a carb'ed engine, as Ive been dealing with the catalyst cycling that is a lot more rapid. I guess the lowest cost would be a £25 narrow band sensor and £6- £10 for a low cost DVM, or around £150- £200 for the wide band set up

[spend]

blitzracing said:

I guess the lowest cost would be a £25 narrow band sensor and £6- £10 for a low cost DVM, or around £150- £200 for the wide band set up

I don't understand what you are talking about, WB sensor doesn't cost anything like that

[stevieturbo]

You could have a viable wideband and display for around £140.

You'd spend more money on fuel wasting your time getting nowhere with a narrowband than the wideband would cost.

[blitzracing]

spend said:

blitzracing said:

I guess the lowest cost would be a £25 narrow band sensor and £6- £10 for a low cost DVM, or around £150- £200 for the wide band set up

I don't understand what you are talking about, WB sensor doesn't cost anything like that

A WB sensor is not much good without a gauge of some sort... I just find a wet finger for measuring the output is just not up to the job!

[eliot]

stevieturbo said:

You'd spend more money on fuel wasting your time getting nowhere with a narrowband than the wideband would cost.

Have to agree.
I've got a narrow in one exhaust bank which is a legacy from when I first started getting into using lambda probes, they dont provide you with much information and there still a degree of guesswork involved.
GET A WIDEBAND!