Gunson gas analysers-anyone knowledgeable? HELP

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scirocco_ne
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Gunson gas analysers-anyone knowledgeable? HELP

Post by scirocco_ne » Sat Jun 08, 2019 11:43 am

I have a choice of two and dont know where to go with it.

Do i get a normal digi model new or a pro used for a little less and have it for tuning Sam next week? I have no idea if the pro is better or just has more features such as rpm etc?

Dilemma dilemma....

Does anyone know the models?

Thanks
Mick



BlackGTX
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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by BlackGTX » Sat Jun 08, 2019 4:04 pm

I got the digital, the magic number is 14.7

The guage one gives you a red amber and green sections to tell how it is along the revs which id prefer as you can visiually see the variance



scirocco_ne
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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by scirocco_ne » Sat Jun 08, 2019 4:35 pm

BlackGTX wrote:
Sat Jun 08, 2019 4:04 pm
I got the digital, the magic number is 14.7

The guage one gives you a red amber and green sections to tell how it is along the revs which id prefer as you can visiually see the variance
I went for the digi professional :)

Wow sam might actually run right yet :D

I chose digital over analogue as the older systems apparently use a thermo resistor over actual sensor so are less accurate.

Surely the professional model is a more sought after piece of kit too.

And tell me more of this 14. 7 business haha im looking forward to having a actual reading to set the weber too over ear.

Mick



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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by BlackGTX » Sat Jun 08, 2019 4:42 pm

14.7 is the general accepted mix ratio or as clise as you can get when setting a maf up



scirocco_ne
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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by scirocco_ne » Sat Jun 08, 2019 5:04 pm

BlackGTX wrote:
Sat Jun 08, 2019 4:42 pm
14.7 is the general accepted mix ratio or as clise as you can get when setting a maf up
As in maf sensor? Ours is on a weber

Mick



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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by BlackGTX » Sat Jun 08, 2019 8:33 pm

Its still the right mix ratio



scirocco_ne
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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by scirocco_ne » Sun Jun 09, 2019 1:23 am

BlackGTX wrote:
Sat Jun 08, 2019 8:33 pm
Its still the right mix ratio
Ill see how close i am Thanks

Does the Haynes recommend that?



GT_II
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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by GT_II » Sun Jun 09, 2019 8:11 pm

I assume you will be using the gas analyser to set the mixture at idle? This is usually set according to % CO. For the MOT test on non-catalyst cars, CO content must be less than 3.5% (or less than 4.5% before D reg). The official VW spec for DX and EX engines is anywhere in the range 0.5% to 1.5% CO at idle, well inside the MOT limit.

I think all the Gunson testers use thermal conductivity measurement, which is not brilliant. They claim to be accurate within +/-0.5% CO, so hopefully good enough to check the idle mixture is in the right ball park and within the MOT limit. My memory from using the analogue one in the 80s was that the reading would drift about massively before settling down.



scirocco_ne
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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by scirocco_ne » Mon Jun 10, 2019 8:02 pm

GT_II wrote:
Sun Jun 09, 2019 8:11 pm
I assume you will be using the gas analyser to set the mixture at idle? This is usually set according to % CO. For the MOT test on non-catalyst cars, CO content must be less than 3.5% (or less than 4.5% before D reg). The official VW spec for DX and EX engines is anywhere in the range 0.5% to 1.5% CO at idle, well inside the MOT limit.

I think all the Gunson testers use thermal conductivity measurement, which is not brilliant. They claim to be accurate within +/-0.5% CO, so hopefully good enough to check the idle mixture is in the right ball park and within the MOT limit. My memory from using the analogue one in the 80s was that the reading would drift about massively before settling down.

Thanks for the info and yes they are not the most accurate. I thought the digis were better but they do use the same reading method as analogue apparently.

I have had no luck setting from ear so needed the tester and a timing gun for piece of mind.

I think long term i will build my own and sell this as they do insane money these days however and ive heard self builds with lamda probes can be pretty good.

I am going to cross reference this against a test station and see how to set up optimum still though . I have heard they take a while to respond to changes so its slow going but if its accurate im happy.

I thought the ideal reading btw was 2.5% but where would be the best place to source the figure. I will try getting it as close as possible.

Mick



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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by GT_II » Mon Jun 10, 2019 10:33 pm

From memory, a painfully slow process to get the mixture right with the Gunson tester. Follow the instructions to make sure you get the calibration right before each test.

On the Mk2, according to Haynes, all carb engines are set at 1% +/-0.5% CO, as is 1.8 injection (DX). 1.6 injection (EG) is set to 1.5 +/-0.5%. It's possible the figure for the Weber may be different - might be worth checking with the manufacturer Webcon.

I had the opportunity to play around with the mixture on my Pierburg 2E2 while in the MOT bay at my local Kwik-Fit (as a favour as I had got to know the old MOT tester pretty well and the agency tester they had in the week before had wrongly failed it for not having a catalyst). I found the car idled pretty well down to around 0.3% CO, but I wound it up closer to 1%, which I assume helps it run better under all conditions. 2.5% is to my mind a bit close for comfort to the MOT limit.



scirocco_ne
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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by scirocco_ne » Tue Jun 11, 2019 3:51 pm

Well after a bit of research the reality is there is no pre determined c0 value for it beyond rough.

Its the usual weber set up followed by a check to make sure its right after. I was told by a weber specialist it should be 2.5 today and if its weak that my engine may need different jets from work im unaware of.

We shall see :)



mark1gls
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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by mark1gls » Wed Jun 12, 2019 2:49 pm

2% is what I aim for in my Mk1 Scirocco (carb) and my Mk1 Golf (fuel injection)

This is what rubjonny (mk1 golf forum) recommends and what he does not know about VW's is not worth knowing.... :-D


Mk1 78 Scirocco GLS 1.6 FR, weekend toy.
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scirocco_ne
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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by scirocco_ne » Wed Jun 12, 2019 9:39 pm

mark1gls wrote:
Wed Jun 12, 2019 2:49 pm
2% is what I aim for in my Mk1 Scirocco (carb) and my Mk1 Golf (fuel injection)

This is what rubjonny (mk1 golf forum) recommends and what he does not know about VW's is not worth knowing.... :-D

I always wonder how that works as you calibrate the machine at 2% in open air haha



mark1gls
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Re: Gunson gas analysers-anyone knowledgeable? HELP

Post by mark1gls » Thu Jun 13, 2019 10:24 am

I've a Gunson gas analyzer and used it to set mine up, when my car had it's MOT I get the bit of paper with the results on then go home and if needed adjust the mixture, eg.... MOT machine reading 1.5% and Gunson reading 2% I will then set the Gunson to 2.5% so the car should be at 2% when tested on a MOT machine as they are alot more accurate than the Gunson....


Mk1 78 Scirocco GLS 1.6 FR, weekend toy.
Mk1 88 Golf GTi cabriolet 1.8 DX. Daily drive.
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