Exhaust Gas Analyser results

[ghost123uk]

Following on from my recent discussion, re are cheap(ish) home EGA's any use, to which the answer was mostly "No, go and use the one at your local friendly garage for beer money", so that is what I did

Now, as some on here will know, I like to understand stuff, this coupled with the fact that there is no-one near me (that I know of) that I can trust to work on a simple, non computerised, no closed loop setup has led me down this route.

Just so ya know, it is a 1.9Ltr, carbed VW flat four, water cooled, mid 80's T25 camper, engine in great nick and fitted with an R90 feeding an open looped BLOS.

I had previously set the BLOS up by road feel and ear, but obviously I needed it better than that, don't want to run lean but don't want to waste fuel either.

So if I post up some results, could anyone comment please ?

EGA was a rather elderly Potech FULX2000-4 (4 gas)

I let it warm up for around 15 minutes then set it to "Cal", which it seemed to do OK, reading all zeros.

My first test was "as is" =
@ Idle CO = .09% / CO2 = 9.1% / HC = 290ppm
@ ~3000 rpm CO = .07% / CO2 = 9% / HC = 270ppm

Second test was "lean off BLOS Idle valve 1/2 a turn" =
@ Idle CO = .07% / CO2 = 8.6% / HC = 300ppm
@ ~3000 RPM = did not test

Third test was "lean off BLOS main valve 1/2 a turn"
@ Idle CO = .15% / CO2 = 8.0% / HC = 300ppm (was a bit confused by this)
@ ~3000 CO = .06% / CO2 = 9% / HC = 230ppm

I then set about adjusting a combination of idle valve on the BLOS and main valve on the BLOS to get the following =
@ Idle CO = .07% / CO2 = 9% / HC = 250ppm
@ ~3000 rpm CO = .07% / CO2 = 9% / HC = 210ppm

I was expecting higher CO2 readings (12 - 14 %) across the board than those I got

Also the unit has a "Function" button which only affected the O2 display. I did not have an instruction book, but will quote what it read during the different Function symbols that appeared after my final adjustments =

"A" = 7.99
"o" = 21 (I know that is the ambient % O2 in fresh air)
"c" = .15
"5" = .529
"symbol" = like a small, square, upside down "u" = .532

Would anyone be kind enough to comment on my findings (if they make any sense, or was the EGA foobarred)

Many thanks in advance,
John

[Gilbertd]

My only comment would be that on an 'old school' engine fitted with an 'old school' fuel system, the best method of setting it up is by 'old school' ear.....

HC is unlikely to change much unless you get it miles out and unburnt fuel is being detected in the exhaust. CO looks about right, far better than the 3.5% maximum allowed for the MoT test. No idea about CO2, it's not checked for the MoT so of no interest (not to me anyway).

[ghost123uk]

Really appreciate your input (again )

My only comment would be that on an 'old school' engine fitted with an 'old school' fuel system, the best method of setting it up is by 'old school' ear.....

I am generally of that opinion too. I don't own any "modern" vehicles, I own 2 x 1950's British bikes, an 85 carb'd Scirocco and this 86 VW camper. Most "tuning" (timing etc) I do by ear and lots of years experience

I am just cautious here of running too lean and damaging valves (or worse), or too rich and wasting money

This is the first time I have used an EGA and though I researched it A LOT !!, I am not confident that any of my results indicate to me richness or leanness (or indicate much of any value in that respect ) I was hoping to see, as I made adjustments, CO go down and CO2 go up (to 12-14%) then if I went too far, one way or the other, the CO would start to rise and the CO2 start to fall, hence me being able to settle at a midway point.

[rossko]

Okay, so you leaned it off and the CO2 reduced. That seems appropriate. We might expect the O2 content to have gone up as well, but that isn't reported.

I think from the near-zero CO starting point I would have gone the other way, richening up until it started making CO. At which point you know you have just crossed the line between lean and rich, and you can use that as your baseline.
(If all you had was a Gunsons CO meter, this is what you'd have to do.)
Have you looked up yet what the engine manufacturer expects/recommends for CO output?

O2 and HC readings at that tipping point are what they are, depending on engine efficiency and so on.

"symbol" might be calculated lambda, but that figure doesn't make a lot of sense.

[ghost123uk]

Okay, so you leaned it off and the CO2 reduced. That seems appropriate. We might expect the O2 content to have gone up as well, but that isn't reported.

Aye, I could not make sense of the figures I was seeing in the O2 display, plus the "Func" button made them change, but none of the figures seemed appropriate

I think from the near-zero CO starting point I would have gone the other way, richening up until it started making CO. At which point you know you have just crossed the line between lean and rich, and you can use that as your baseline.

Good point, I only had limited time with this EGA and it was the first time I had used one, so I did not have time to "experiment" much. The knowledge I had gleaned led me to think I should be aiming for a setting that gave minimum CO and maximum CO2, which is what I did.

Have you looked up yet what the engine manufacturer expects/recommends for CO output?

I have been unable to find this info despite considerable searching. Would it be the same value on LPG as for Petrol ?

"symbol" might be calculated lambda, but that figure doesn't make a lot of sense.

I wondered about why I could not see a calculated Lamda, and you're right (of course) non of the figures go anywhere near what one would expect for a Lambda reading

I don't even know if this EGA was working correctly. The owner of it said it hadn't been used for a good few years.

I think I might have to bite the bullet and drive the 120 mile / 3 hour trip to Grantham, where I know a place that specialises in VW T25 LPG conversions, and let them put it on their EGA. They are well respected and I believe will also show me what is what. Shame I have to do that though as the fuel alone will cost around £35 if I use LPG and more if I drive to them on petrol (in case I am running lean), plus their charge At least it's a camper, so I can break the journey up with an overnight stop somewhere.

[ghost123uk]

Quite pleased with my self now I did not trust that EGA I used, it had stood for years untouched.

So today I popped into my local friendly classic car repair garage in the town (Waymills Garage, Whitchurch). The owner said if it's been stood for ages, the O2 sensor system will likely be in need of replacement and the whole unit could not be trusted (i think I knew that ).

Then he said "would you like to put it on my £6K Sun one" So I did

At Idle I was only concerned with CO and CO2 (not having much time again) for MOT reasons

Idle, CO = .171% / CO2 = 11.1%

At ~3,000 rpm, CO = .114% / CO2 = 13.5% / HC = 14/13 (?) / O2 = .5% / Lambda = 1.026 ( )

Re the HC reading of "13/14" which is what my missus wrote down off the readout, not sure what that means ? Anyone ? (I forgot to ask him )

I also held it at ~2000 rpm and then at about 4000 rpm and the Lambda stayed in the green (though it went rich briefly as the throttle was increased = all good thanks to the BLOS )

Am I right to be happy with those readings ? (Any comments appreciated)