I have for some time lusted after an exhaust gas analyser. Carl's latest post here Link (http://forum.w116.org/mechanicals/280-se-big-service/msg68861/#msg68861) 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 (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=390136176813&viewitem=&sspagename=STRK%3AMEWAX%3AIT)
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
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
Thanks Bill. Link fixed.
Here's some eye candy that gives some idea of what the decent stuff costs.
Link (http://motors.shop.ebay.com/i.html?_nkw=emission+analyzer&_sacat=&_trksid=p4506.m270.l1311&_dmpt=Motors_Car_Truck_Parts_Accessories&_odkw=exhaust+gas+meter&_osacat=0)
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.
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
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
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.
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
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.
Quote from: s class on 28 December 2009, 02:52 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
Quote from: koan on 28 December 2009, 02:34 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
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.
Sorry, correction, should read, current ones are 5 gas.
Trust me, I would be getting the 5-gas one if I could, but the price is a bit ouch.
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.
I've had a look at the Aus crowd Tech edge here :
Link (http://wbo2.com/home/products.htm)
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 :
(http://wbo2.com/sw/winlog1.gif)
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.
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 ;)
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.
Quote from: s class on 29 December 2009, 05:35 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.
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 ;)
Quote from: WGB on 28 December 2009, 05:44 PM
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
Quote from: s class on 29 December 2009, 01:09 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
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.
Quote from: s class on 29 December 2009, 07:53 AM
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
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. :)
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.
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.
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
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.
I see, no wonder that mixture screw has such a profound effect.
Tim
Speaking of tuning WUR's..
http://unwiredtools.com/utcis.asp
Quote from: wolf_walker on 07 January 2010, 10:11 PM
Speaking of tuning WUR's..
http://unwiredtools.com/utcis.asp
Very interesting find. My WUR is working sweet compared to my old one.
Weird thing is though, after a good run, if it sits for about 10mins then goes to start - it takes a bit of cranking... I'm guessing fuel pressure related.
It's interesting though, read through it but don't really understand that much of it.
Am I right to assume that at warm running temps it maintains better fuel pressure and even raises fuel pressure at different rpm ranges with use of the software application also?? (I'm probably totally wrong...)
Cam.
Hot start can be mixture but usually the accumulator.
That fancy WUR is tunable because contrary to popular belief and it's English name, the WUR operates and varies
throughout the operating range of the engine, varying pressure to adjust mixture. Or something along those lines, it's been years since I had a k-jet car, but I loved it dearly. You can indeed, in theory, tune that one to specific mixtures are differing temps and such, it's spendy in my opinino with the alternatives out there, but it's most defanantly neat.
K-Jet is one of the most reliable and long lived fuel systems I have ever seen, there is a reason all of the more pricy, and even cheaper, euro cars used it for so long, even hanging lamda on it later(which rocked) and less so the assorted other smog stuff. People have told me the only reason it finally went away was lack of fine tuning ability for cold start and warm up emissions, but I don't have any way to prove it. From the performance and MPG I always observed from healthy K-Jet, I believe it, none of the directly after EFI systems improved on any of that significantly for awhile.