Author Topic: Exhaust gas analysers  (Read 12035 times)

s class

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Re: Exhaust gas analysers
« Reply #15 on: 29 December 2009, 01:33 AM »
I've had a look at the Aus crowd Tech edge here :

Link

They have many AFR measuring units, some even DIY, based on wide-band lambda sensors. 

For a little over 200 dollars, one can get a decent unit which allows on-board logging, or logging to a PC, of AFR, plus various other analogue inputs (RPM, MAF, etc etc).  the number of inputs varies with model.  There's a lot of reading to do, but it seems even the $200 options allow real-time monitoring on a PC with displays something like this :



I'm reading a bit on their forum about the pros and cons of different models, but I think I might give this a go in the new year. 


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

Big_Richard

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Re: Exhaust gas analysers
« Reply #16 on: 29 December 2009, 02:24 AM »
that looks really cool.

and laptops are cheap enough these days to have one out in the garage for test runs for such tasks.

Not many of the inputs would get used on a w116 though ;)


s class

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Re: Exhaust gas analysers
« Reply #17 on: 29 December 2009, 02:35 AM »
Yeah, the only signal readily available would be tacho.  But I am contemplating an electronic pressure transducer to allow real-time logging of control pressure.  That would be cool. 

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

Big_Richard

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Re: Exhaust gas analysers
« Reply #18 on: 29 December 2009, 02:52 AM »
Yeah, the only signal readily available would be tacho.  But I am contemplating an electronic pressure transducer to allow real-time logging of control pressure.  That would be cool. 

that's very doable, I'm sure one that detects pressures within the operating range of K-jet will be an "off the shelf" affair anyway ;)


koan

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Re: Exhaust gas analysers
« Reply #19 on: 29 December 2009, 03:31 AM »

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


I've been buying a the odd English magazine recently and they are still advertised.

When I was given a demo I couldn't see the colours which was probably my colour vision not the plug.

koan
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koan

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Re: Exhaust gas analysers
« Reply #20 on: 29 December 2009, 03:33 AM »

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

Should we be aiming for something other than 14.7:1 ?

koan
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s class

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Re: Exhaust gas analysers
« Reply #21 on: 29 December 2009, 04:53 AM »
I don't know koan.  I think that k-jet being what it is, one will not be able to reach a setpoint AFR at every RPM condition.  To accomodate this, I believe these old engines are tuned slightly to the rich side.  Of course, there will be a different AFR during acceleration when the WUR drops the control pressure.


I think these variations in AFR is what will make a narrow-band type lambda sensor unsuitable for tuning. 

'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 #22 on: 29 December 2009, 01:22 PM »
I think that k-jet being what it is, one will not be able to reach a setpoint AFR at every RPM condition.

I think these variations in AFR is what will make a narrow-band type lambda sensor unsuitable for tuning. 

I see what you mean now. I've driven round with a narrow band sensor up the exhaust pipe, it wasn't much use. Any situation but idle it went out of range, showed over rich - which might be accurate of course but I doubt it.

koan
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SELfor50

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Re: Exhaust gas analysers
« Reply #23 on: 29 December 2009, 04:15 PM »
That computer kit looks pretty cool.  On K-jet though, you can only set the one mixture setting right?  So it's a case of compensating for higher rpm's and then suck and see?   

Or is it a case of getting the data by using the analyser at different RPM's, and then if at say 4000rpms it's leaning out then you wind the mixture up so it's even richer at idle but has the right setting at 4000rpms?

I'm guessing it depends where in the RPM range you spend most of your time?!  For me, I need to tune it for 3000-5500rpms.  :)
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s class

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Re: Exhaust gas analysers
« Reply #24 on: 29 December 2009, 11:46 PM »
Yeah.  Basically, the workshop procedure calls for tuning the CO to the correct setting at idle.  But of course, that assumes the FD, WUR, injectors are all in spec, and there are zero vacuum leaks, and perfect compression.  This is all highly unlikely on our 30 year old engines (yours is different though....), and one could easily set the required idle CO and find that it is way too rich or way too lean under load or at mid range for example.  This data would either help you set a more suitable compromise mixture under the circumstances, or let you diagnose a poor WUR.  I would like to be able to use it to tune a marginal WUR, or identify a poor WUR as bin material. 

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

SELfor50

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Re: Exhaust gas analysers
« Reply #25 on: 30 December 2009, 04:01 AM »
Poor WUR's seem to be a dime a dozen.  Swapped the 1 on the track car twice, and before changing engines, swapped that one twice.  Just didn't wanna play nicely.

Be good to get a good analysis of mixtures at different revs though, find an optimal range.
"Man who come first, wins race." -Unknown

-= 1978 - 450 SEL [Euro] =-  Locked
-= 1976 - 450 SE 6.9 #2 =-  New Heart

TJ 450

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Re: Exhaust gas analysers
« Reply #26 on: 30 December 2009, 04:14 AM »
I've just been mucking around with mixture settings etc and I was under the impression that the adjustment screw was simply for idle only?

Having adjusted the mixture/idle speed, I've been able to obtain quite a smooth idle, but it lacks a bit of the initial acceleration bite it used to have. There is no ping and it doesn't run hot anymore. It has returned 17.777L per 100km max when used every day for business purposes.

An analyser would be cool, along with the K-Jet gauge that I really should be getting.

Tim
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1969 300SEL 6.3 1394
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s class

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Re: Exhaust gas analysers
« Reply #27 on: 30 December 2009, 04:19 AM »
TJ, there are two adjustments as I'm sure you know.  The idle air screw affects idle only.  The little allen head adjustment accessed via the grommet on top of the air meter housing is the mixture screw, and that has an effect across the entire rev range, since it alters the relationship between the air meter flap deflection and the FD metering piston movement.

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

TJ 450

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Re: Exhaust gas analysers
« Reply #28 on: 30 December 2009, 04:28 AM »
I see, no wonder that mixture screw has such a profound effect.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
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wolf_walker

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Re: Exhaust gas analysers
« Reply #29 on: 07 January 2010, 07:11 PM »
Speaking of tuning WUR's..

http://unwiredtools.com/utcis.asp