Author Topic: Exhaust gas analysers  (Read 12034 times)

s class

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Exhaust gas analysers
« on: 28 December 2009, 01:22 AM »
I have for some time lusted after an exhaust gas analyser.  Carl's latest post here Link has further sparked my interest.  

Carl's one is a 5-gas analyser (if it is the one I think it is on Snap-on's website).  This snap-on one is out of my price range.  

Simpler ones can be had on-line quite cheap, but I wonder if the cheapies are any good.  typically, they are only single gas (CO) measuring meters like this one : Link
As I understand it, measuring CO is quite likely perfectly sufficient for tuning 70's benzes, which don't have catalytic converters.  

Does anyone have any input on these issues based on experience?

I suppose the basic question is :

a) is that cheapie meter waaay better than nothing, or
b) is it so far short of the snap-on meter that it is only very slightly better than nothing?

Does anyone have some other affordable meter that they could recommend?

Thanks

« Last Edit: 28 December 2009, 02:23 AM by s class »

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

WGB

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Re: Exhaust gas analysers
« Reply #1 on: 28 December 2009, 02:16 AM »
I explored this two or three years ago and didn't come up with anything useful so will be interested in what you find.

I aked my mate who owns the local garage and he said he threw his out years ago.

BTW the link you supplied didn't come through.

Bill

s class

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Re: Exhaust gas analysers
« Reply #2 on: 28 December 2009, 02:24 AM »
Thanks Bill.  Link fixed. 

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s class

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Re: Exhaust gas analysers
« Reply #3 on: 28 December 2009, 02:33 AM »
Here's some eye candy that gives some idea of what the decent stuff costs. 

Link

I want to believe that the cheapie is OK for home use, but my gut tells me that anything less than these multi-thousand dollar units is not much help. 

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

WGB

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Re: Exhaust gas analysers
« Reply #4 on: 28 December 2009, 03:52 AM »
Gunson have made cheap tuning gear for the past 40 years at least.

I still have a Gunson Colourtune plug also a carb balancer that I used in my Mini Cooper S and 260Z with triple double Barrel Dellortos. All still work (not necessarily so with the cars) and are in my posession (not the cars) but of course contain no electronics.

I would imagine like most cheap electronics it would be ok for a year or so but long term you are on your own.

Bill

Papalangi

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Re: Exhaust gas analysers
« Reply #5 on: 28 December 2009, 04:50 AM »
I have that very Gunson exhaust gas analyzer and use it once or twice a year.  I've had it eight or nine years now.

I bought mine here and also bought the eezibleed from him.
http://www.autoexpertproducts.com/gastester.htm

The analyzer works fine, it's not the fastest nor the most stable unit around but my W114 280C (M110) blew a 7.5% CO when I took it in for it's yearly test and I was able to tune it to 1.5% or whatever it was that was posted on the emissions tag on the radiator support.  I keep the 450SEL at ~1% or so.  It does change when you adjust the idle.

Michael
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1971 250C, 114.023      Sad but true, it's gone to a new home.
1976 280C  Stolen by the City of Seattle, sort of.
1970 250/8, traded in on a 1993 Land Rover Disco

s class

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Re: Exhaust gas analysers
« Reply #6 on: 28 December 2009, 05:08 AM »
Thank you papalangi.  Your input encourages me that maybe it isn't the world's greatest, but it at least allows you to get usable results.

Since posting this thread, I have had another idea - I have a generic Bosch lamda sensor lying at home.  It is new, and I believe (would have to check) that it is the variety that incorporates a heater.  The significance of the heater is that it is self-sustaining, and does not rely on the exhaust gas temperature to reach operating temp.  This would (I hope) allow it to be mounted in a temporary tail-pipe extension and function satisfactorily.  Normally they are located at or near the exhaust manifold to utilise exhaust gas heat to reach operating temp. 

I want to play around with this idea, as it will cost me basically nothing to make if it works.  If not, then that Gunson unit may be my answer. 

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

koan

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Re: Exhaust gas analysers
« Reply #7 on: 28 December 2009, 11:34 AM »
Don't know if they were called analysers 30 years ago but the device I had then worked well, it displayed stoichiometric ratio on a meter, it used hot wires to measure the thermal conductance of exhaust gas. I lent it to someone who on-lent it and never saw it again.

More recently I built a box that uses a Bosch 02 sensor, it works but I don't trust it. Because it uses a narrow band sensor it's a bit sudden death, small mixture adjustments cause big changes in indicated values.

There's a similar kit now that uses a Bosch wide band sensor, I might give that a go.

Since we don't have emission rules here I can't see the need for a device that shows gas percentages, all that matters is air/fuel ratio, I just go for around 14.7 and that's it.

WGB, those colour tune plugs are a very English way of doing things, a mate had one years ago and didn't think much of them, what's your opinion of them?

koan
 
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s class

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Re: Exhaust gas analysers
« Reply #8 on: 28 December 2009, 11:52 AM »
koan, I agree that we don't need gas percentages, but my thoughts were that if I use an O2 sensor, the output voltage actually is related by a conversion curve to a stochiometric ratio.  The sensor I have is, I believe, also a narrow band one, and so would only give an accurate value when one is very close to the target.  I'm tied up with work at the moment, but a bit later I'll dig it out and look up the part number. 

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

koan

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Re: Exhaust gas analysers
« Reply #9 on: 28 December 2009, 12:43 PM »
koan, I agree that we don't need gas percentages, but my thoughts were that if I use an O2 sensor, the output voltage actually is related by a conversion curve to a stochiometric ratio.

The output voltage of the sensor is an indication of excess air relative to 14.7:1 but as I mentioned it's sudden death, a very steep curve, it shows correct ratio accurately but no useful indication of anything either side of 14.7:1.

Quote
The sensor I have is, I believe, also a narrow band one, and so would only give an accurate value when one is very close to the target.  I'm tied up with work at the moment, but a bit later I'll dig it out and look up the part number. 

The unit I have is 0 258 104 002, definitely  narrow band.

koan
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WGB

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Re: Exhaust gas analysers
« Reply #10 on: 28 December 2009, 02:44 PM »

WGB, those colour tune plugs are a very English way of doing things, a mate had one years ago and didn't think much of them, what's your opinion of them?

koan
 

My 260Z had 6 carburetor barrels and to get a stable idle the idle mixture as well as the air volume had to be quite precise for each cylinder.

My then wife would also drive it to school with the choke out most of the way and it would need tuning every few months to keep a reliable idle.

I thought the plug was excellent - especially when each cylincer could be adjusrted individually.

Bill

carl888

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Re: Exhaust gas analysers
« Reply #11 on: 28 December 2009, 08:09 PM »
The Snap On one I use in the pics belongs to a friend, it's really expensive, sadly.  But it works a treat.  The function I use the most is AFR.  I also check CO and HC more out of curiosity though.  The current ones are three gas, that's what I'd be buying.

For me, the single most imporatant function with a gas analyser, is that it be portable.  I love to check the AFR under dynamic conditions.  In fact, I was able to locate a fuel metering problem with the W126 (Excessively lean at 1,800 rpm at part throttle) that would have been impossible to diagnose at idle.  So after I set the car up at idle, I take it for a spin with a analyser sitting on the dash.

You do get some funny looks from people with masking tape up the side of the car!

Regards,

Carl.

carl888

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Re: Exhaust gas analysers
« Reply #12 on: 28 December 2009, 08:17 PM »
Sorry, correction, should read, current ones are 5 gas.

s class

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Re: Exhaust gas analysers
« Reply #13 on: 28 December 2009, 10:07 PM »
Trust me, I would be getting the 5-gas one if I could, but the price is a bit ouch. 

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

s class

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Re: Exhaust gas analysers
« Reply #14 on: 28 December 2009, 10:09 PM »
koan, the sensor I have here is 0 258 003 842, which is a member of the LSH25 family - again definately narrow band.

So it will probably not work, since the AFR we are aiming for on these old benzes is way outside of its sweet spot.

The later generation of wideband sensors though, may well do the job. 

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL