Talk to me about AFR gauges

[ben711200]

Evening,

I'm having a look around at AFR gauges and lambda probes for the Volvo. As part of the ongoing arsing about with the LPG fuelling, I think it would be very useful to know what was actually going on!

I'm looking at guages and some are dirty cheap, some are massively expensive. I'm told it's not worth bothering unless I go for wideband but then that's where it gets expensive.. Any advice to steer me in the right direction would be brilliant.

Cheers!

Ben ;D

[BenzBoy]

I, too, looked into this. I actually got a cheap air/fuel gauge on ebay just to mess with. The wideband ones give much more accurate readings whereas I was fully prepared just to get a very approximate indication of what was going on from my cheapy.

The cheapies are really nothing more than a gauge which reads from 0 - 100% indicating the lambda probe's output (0 to 1 volt, if I remember correctly)

[steveo3002]

yeah its true...need a wideband to be accurate

the cheapies aint much more than a fancy display really , not good enough to tune from

[vitesseefi]

I have an Innovate LC-1 hooked up to my Megasquirt ECU. This has proved an absolute revelation when tuning and is not permanently in the loop keeping everything on target. Works really well.

You can also connect it to an analogue display or hook it up to a laptop.

Bear in mind that LPG is stochiometric at a different ratio (15.8:1) compared to petrol (14.7:1).

If you are running old style inducer-ring lpg system rather than injection then be prepared for disappointment when it comes to getting the right numbers to come up.....

Nick

[hongkongphooey]

Yep,those narrow bands are just pretty lights and nothing more, operating on a 1v range.It'll just show rich if you're running 12-1/11-1/9-1 or whatever and lean if you're running 15-1 or 18-1. You just won't know. Narrow band lambda sensors have anything from 1 to 4 wires,found on most injection cars. The narrow gauges tap into these sensors. Wideband sensors are 5 wire and operate within a 5v range.

There are pretty much two sensors used in UEGOs,the NTK L1H1 and the bosch LSU. The ones using the bosch would be the ones to go for as the replacement sensors tend to be 1/4 of the price of the NTKs. Most units use the bosch now.

I've used the AEM unit before which is self contained in a 52mm gauge and seemed a very good unit. I'm currently using the Innovate unit mentioned above which has the capabilities of hooking up to a lappy....but i've not used that bit yet. This needs a seperate gauge unit though if you want an in car display afaik.

[hongkongphooey]

Actually,it looks like most of the LM-1s on ebay come with gauges. I got mine from here with a seperate digital gauge from the same place.

[ChrisT]

^^^^got my gauge from the same place (first IIRC) but using it with a techedge 2J1 controller from triggerwheels. like the others can be linked up to a laptop for whatever reason

gives good readings, according to the guy mapping the car on the rollers.

not the best quality vid, does react quicker than it looks, was done with a low res phone.....

[lolface]

yep as already mentioned, the cheap ones are pretty useless really, looking at the oxygen sensor graphs it pretty much shows rich 13.5 onwards and lean 15.5 onwards the other direction.
On turbo applications they are totally useless, as even a 'rich' 13.5:1 at max boost is too lean in reality. I guess they can be used to tune up a set of carbs or something
you can get a programmable system with screen and sensor for about £100 delivered with a bit of assembly required from here:
14point7.com/

I have the jaw 1.03 (which has now been superseded) but it's fapping brill and does everything an innovate lc1 does (and more?)

[30psi]

I first had a narrow band gauge when I was a youngster about 6 years ago. Completely curse word to be honest as basically said up there. They only monitor approx 14.2 - 15.7, so are really only ok for absolute fine tuning to stroich, but have now been superseded on cars by widebands. Alot of VAG cars run them I think and that large volume of supply has prob brought down the cost of a wideband significantly.

I now have 2 widebands. One's an LM1 for mobile use, I've probably used it on 10 different cars e,g my tbird, my datsun auto, dad's corvette, mates Alpine, mates S12 etc. Brilliant bit of kit if you get it with the exhaust clamp as typically speaking you don't need a permanent gauge unless your running a highly boosted engine or something where any weakness in AFR is critical. That's why I have a VEMs 52mm one, I will be keeping one eye on the AFR, one eye on the boost, one eye on the oil pressure, one on the water temp and half an eye on the road lol...

[hongkongphooey]

Dec 18, 2009 23:31:51 GMT ChrisT said:

like the others can be linked up to a laptop for whatever reason

I assume it's for data logging qtr mile runs or laps of a track etc etc. Possibly useful for tuning when you can't watch the gauge every second?

[30psi]

Data logging is handy because when your trying to watch the afr on full thottle its very hard to keep track of the rpm as the afr changes. To stop the revs climbing quick you need to be in a higher gear, which means more concentration needed on the road etc etc. You'd get a lot more meaningful info out of of the datalogging than using a gauge on its own.

[ben711200]

Cheers everyone. Being an open loop LPG system, it looks like it may just be something I need to put up with until it comes to upgrade time..

Dec 18, 2009 21:05:24 GMT vitesseefi said:

Bear in mind that LPG is stochiometric at a different ratio (15.8:1) compared to petrol (14.7:1).

If you are running old style inducer-ring lpg system rather than injection then be prepared for disappointment when it comes to getting the right numbers to come up.....

Nick

The stoich of petrol and LPG shouldn't make any difference on a Lambda though, should it? Because the lambda reads the amount of oxygen remaining in the exhaust gas, not the actual AFR.

[30psi]

Correct I believe... Stoich is 1:1 and that's what's measured. That's why the single figure eg 1.01, 0.97 etc makes more sense as it's relevant to the stoich of the fuel