Hello, been a while since I looked in on this group.

For those of you who remember - or care - I am still driving my '87
Volvo 740, which I converted to a basic open loop system 9 years ago.

MoT was last week, which it passed, but the emissions - on LPG - were
a bit marginal to say the least. Pass is =<3.500% CO, and mine scored
3.507%. Technically this is a fail, but they're a decent lot where I
go for the test, and as it dropped to 3.49% a nano-second after the
test completed, he used his discretion.

But needless to say, this is way too high when it's running on LPG
(previous results have been around the 1% mark). I've always tuned the
mixture by ear, and got good results, but there is clearly something
more amiss, which is also indicated by a recent 10% drop in MPG.
Further tinkering seems in order.

So I want to get hold of an exhaust gas analyser of some sort. The
only one I can find this isn't aimed at 'professionals', the size of a
small wardrobe, and 500+ GBP is the Gunson's Gastester G4125
http://www.gunson.co.uk/item.aspx?item=1835 . Last time I had anything
to do with a Gunson's product (10+ years ago), they seemed to be
purveyors of utter crap, but I'm told they've improved their standards
since then. This thing only seems to measure CO, but that's probably
all I need.

It's listed at about 125GBP, but can be had online for 80 or so. That
seems OK to me - I realise this is not top-end stuff, but it's only
going to be used occasionally, and I don't really need greater
accuracy.

So, has anyone any experience of using it with LPG? In the MoT
Tester's Manual http://www.motuk.co.uk/manual_730.htm it says: "...the
hydrocarbons are propane rather than hexane. So the HC reading
obtained must be divided by the propane/hexane equivalency factor
(PEF) marked on the gas analyser."

I'm unsure it this would affect the CO reading, or whether it only has
significance for HC (which the Gastester doesn't seem to measure). I
phoned Gunson's technical helpline, but the chap I spoke to didn't
know. Anybody like to cast an opinion?

Stewart H.

On or around Sat, 4 Apr 2009 09:48:04 -0700 (PDT), mogme100@googlemail.com
enlightened us thusly:

[gunsons thing]

It'll pick up gross tuning errors, like CO at 5%, say.

It's not sufficiently accurate for good tuning, especially systems with more
accurate controls, where you can be looking for about 0.15%
-- 
Austin Shackles.  www.ddol-las.net  my opinions are just that
Travel The Galaxy!  Meet Fascinating Life Forms...
------------------------------------------------\   
   >>  http://www.schlockmercenary.com/  <<      \  ...and Kill them.
a webcartoon by Howard Tayler; I like it, maybe you will too!

On 5 Apr, 09:28, Austin Shackles <austinDITCHTHISFORBETTERRESU...@ddol-
las.net> wrote:

> On or around Sat, 4 Apr 2009 09:48:04 -0700 (PDT), mogme...@googlemail.com
> enlightened us thusly:
>
> [gunsons thing]
>
> It'll pick up gross tuning errors, like CO at 5%, say.

Is that because of the PEF thing, or is it just crap? Gunsons claim
accuracy a factor of 10 better than that, which on my open loop system
would be good enough.

Anyone know any alternative exhaust gas analysers?

Stewart H.

On or around Sun, 5 Apr 2009 05:04:01 -0700 (PDT), mogme100@googlemail.com
enlightened us thusly:

>On 5 Apr, 09:28, Austin Shackles <austinDITCHTHISFORBETTERRESU...@ddol-
>las.net> wrote:
>
>> On or around Sat, 4 Apr 2009 09:48:04 -0700 (PDT), mogme...@googlemail.com
>> enlightened us thusly:
>>
>> [gunsons thing]
>>
>> It'll pick up gross tuning errors, like CO at 5%, say.
>
>Is that because of the PEF thing, or is it just crap? Gunsons claim
>accuracy a factor of 10 better than that, which on my open loop system
>would be good enough.
>
>Anyone know any alternative exhaust gas analysers?

I've got a vintage Sun one. 

Yeah they claim 0.5%.  It's good enough for "passing the mot" checking,
ISTR.  Depends on what you're after, really.
-- 
Austin Shackles.  www.ddol-las.net  my opinions are just that
Travel The Galaxy!  Meet Fascinating Life Forms...
------------------------------------------------\   
   >>  http://www.schlockmercenary.com/  <<      \  ...and Kill them.
a webcartoon by Howard Tayler; I like it, maybe you will too!

On Sat, 4 Apr 2009 09:48:04 -0700 (PDT), mogme100@googlemail.com
wrote:

>Hello, been a while since I looked in on this group.
>
>For those of you who remember - or care - I am still driving my '87
>Volvo 740, which I converted to a basic open loop system 9 years ago.
>
>MoT was last week, which it passed, but the emissions - on LPG - were
>a bit marginal to say the least. Pass is =<3.500% CO, and mine scored
>3.507%. Technically this is a fail, but they're a decent lot where I
>go for the test, and as it dropped to 3.49% a nano-second after the
>test completed, he used his discretion.
>
>But needless to say, this is way too high when it's running on LPG
>(previous results have been around the 1% mark). I've always tuned the
>mixture by ear, and got good results, but there is clearly something
>more amiss, which is also indicated by a recent 10% drop in MPG.
>Further tinkering seems in order.
>
>So I want to get hold of an exhaust gas analyser of some sort. The
>only one I can find this isn't aimed at 'professionals', the size of a
>small wardrobe, and 500+ GBP is the Gunson's Gastester G4125
>http://www.gunson.co.uk/item.aspx?item=1835 . Last time I had anything
>to do with a Gunson's product (10+ years ago), they seemed to be
>purveyors of utter crap, but I'm told they've improved their standards
>since then. This thing only seems to measure CO, but that's probably
>all I need.
>
>It's listed at about 125GBP, but can be had online for 80 or so. That
>seems OK to me - I realise this is not top-end stuff, but it's only
>going to be used occasionally, and I don't really need greater
>accuracy.
>
>So, has anyone any experience of using it with LPG? In the MoT
>Tester's Manual http://www.motuk.co.uk/manual_730.htm it says: "...the
>hydrocarbons are propane rather than hexane. So the HC reading
>obtained must be divided by the propane/hexane equivalency factor
>(PEF) marked on the gas analyser."
>
>I'm unsure it this would affect the CO reading, or whether it only has
>significance for HC (which the Gastester doesn't seem to measure). I
>phoned Gunson's technical helpline, but the chap I spoke to didn't
>know. Anybody like to cast an opinion?
>
>Stewart H.

It displays CO. The graph on page 16 of the instructions is true for
all fuels only the AFR scale needs changing. Petrol AFR 14.7 = lambda
1 = Propane AFR 15.6, so scale all AFR values by 1.06 (=15.6/14.7) or
use Lambda (petrol AFR/14.7)

Very impractical. It says the pipe from exhaust probe should slope
downwards so water collects and is expelled from pulse pump on
readout/gauge unit - only realistically possible by placing the unit
on the ground. Not supposed to to have probe in exhaust when engine
reved or under load as exhaust temps at tailpipe too high. Won't give
any insight to higher load excess MPG, that needs constant 60-70mph
cruise or WOT acceleration runs. Really it can only be of use to mask
fault at idle condition giving a MOT pass.

Get a Wide band Lambda around £200 for wb interface + lambda +
display.
http://trigger-wheels.com/store/index1.html
This is what almost all "chip" tuners use. Inertia rolling roads only
do transients and don't allow mapping for cruise.

Should be easy to get a re-program to suit LPG 15.6 stoichiometric
AFR, or just use Lambda as that's 1 for all fuels at stoichiometric.

Once you have a WBO you may as well close the loop.
-- 
Peter Hill
Spamtrap reply domain as per NNTP-Posting-Host in header
Can of worms - what every fisherman wants.
Can of worms - what every PC owner gets!

On 5 Apr, 13:24, Austin Shackles <austinDITCHTHISFORBETTERRESU...@ddol-
las.net> wrote:

> I've got a vintage Sun one.

Well I've just bought a Bosch jobbie from Ebay, which I reckon should
be a better option than the Gunson's one. Only 1 gas, though. There
are plenty of ex-MoT Sun 4 gas units on Ebay, which would be lovely,
but I really don't have the storage room for one, and this thread
http://www.motester.co.uk/forums/forum1/737.html (start reading at the
bottom and work up) is a bit of a worry - gas testing is disabled once
the MoT calibration expires and can only be reinstated by Snap-On. Did
you have any problems like this with your Sun unit?


Stewart H

On or around Sun, 12 Apr 2009 06:37:45 -0700 (PDT), mogme100@googlemail.com
enlightened us thusly:

>On 5 Apr, 13:24, Austin Shackles <austinDITCHTHISFORBETTERRESU...@ddol-
>las.net> wrote:
>
>> I've got a vintage Sun one.
>
>Well I've just bought a Bosch jobbie from Ebay, which I reckon should
>be a better option than the Gunson's one. Only 1 gas, though. There
>are plenty of ex-MoT Sun 4 gas units on Ebay, which would be lovely,
>but I really don't have the storage room for one, and this thread
>http://www.motester.co.uk/forums/forum1/737.html (start reading at the
>bottom and work up) is a bit of a worry - gas testing is disabled once
>the MoT calibration expires and can only be reinstated by Snap-On. Did
>you have any problems like this with your Sun unit?

Mine is a true vintage piece, it's only CO.  No MOT stuff.
-- 
Austin Shackles.  www.ddol-las.net  my opinions are just that
Travel The Galaxy!  Meet Fascinating Life Forms...
------------------------------------------------\   
   >>  http://www.schlockmercenary.com/  <<      \  ...and Kill them.
a webcartoon by Howard Tayler; I like it, maybe you will too!