Gunson Gastester

Dec 11, 2004 11 Replies

I have a 900 T8 fuelled by the K-Jet system, so I'm pretty much in the dark when it comes to mixture. I'm getting pretty fed up of having to go to a garage to have my mixture checked after cleaning the air filter. Half of the time, they get it wrong anyway ... by wrong, I mean nowhere near as good as my normal SAAB independent garage who often need a week or so notice to get in. A slight tweak gives me better power and performance ... usually.



So, I've been looking at the Gunson Gastester. In Halfords (I know ), their display case had the instruction manual still in the box. Am I right in thinking that reducing CO to as low as possible gets the car as close as possible to stoich? It would appear so from the graph. I take it this is not just a case of twiddling the mixture, but adjusting the basic idle too.



I'd appreciate hearing from people who have this kind of tool, especially B201 engine owners; 900 or 99. How useful is it? How easy to use is it; not that I'm scared off by having to spend some time fine-tuning. Is it a good tool?



Paul


1989 900 Turbo S
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in article BDE0F64E.12C5A%pjgh.smtp snipped-for-privacy@blueyonder.co.uk, Paul Halliday at pjgh.smtp snipped-for-privacy@blueyonder.co.uk wrote on 11/12/2004 19:09:

Well, I finally got my gastester, somewhat delayed due to (a) Halfords' incompetence and (b) Gunston getting bought out. Wow! What a difference. My car was miles out (erm, somewhere between 6 and 7 percent!!!) ... So I've backed it down to about 3.5 percent and the car feels "just right". It holds the high notes without the wastegate smashing about and doesn't require anything like the footdown to get it moving.

Not the best 60 quid I've ever spent, but well worth it. I'll see what it does for my fuel economy over the next few tanks once my excitement at having high steady boost wears off :)

So ... My next question: How hard is it to fit a lambda to fine tune CIS fuel metering device?

Paul

1989 900 Turbo S
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Do you mean to permanently install a lambda sensor and hook it up to the CIS? I don't believe that's possible - the CIS is purely mechanical, so there's nowhere in the control loop where you can plumb in a sensor.

Sure you could, just install the fuel distributor from an early 80's Volvo, though I thought the 900's already had Lambda? There's ports on the side of CIS cars meant for Lambda where a frequency valve plumbs in to tweak the control pressure.

I don't believe there was ever a UK 900 with CIS and lambda, or CIS that had a suitable interface - but if the volvo one is compatible, then that may well be a way to go.

in article snipped-for-privacy@individual.net, Grunff at snipped-for-privacy@ixxa.com wrote on 12/02/2005 18:37:

I'm not sure I've seen a CIS powered 900 with lambda, although my downpipe has a tell-tale weld over in a location suitable for lambda. The early Volvo setup is certainly worth looking into - Thanks James.

The reason I asked is that I have downloaded a Bosch service manual for the CIS/K-Jet system (which happened to be for a Porsche, but ...) and it made reference to hooking up a lambda probe. I can't see anything obvious on the SAAB, but I'm on a mission around the scrap yards to see what I can find. Mercedes of the early '80s vintage might be good too, but I doubt I'll find an old Porsche in any scrap yard near me :)

Here's the location of the manual for other CIS pilots:

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Cheers guys ... I let you know what I find.

Paul

1989 900 Turbo S
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Ah, didn't know we were talking UK spec cars, a lot of the emission control stuff came in much earlier in the US than UK, Canada and probably the rest of the world. I'll have to look under the hood next time I see a CIS 900 in a scrapyard.

The 924 and the 928 both used CIS.

More likley to find a 924 though. And that used the LT35 Van engine. Yes another source.

BTW, investigate K-Star setups. They don't like messing with Saabs as they haven't done any/many, but it's justa K-Jet afterall, just like the VW/Audi/Porsche stuff, and I think Big John from Saabscene has one on his very fast 900 T8 Special edition.

Cheers fella. Yeah! JW's T8S is quite something. I've yet to ee the car, but my pal PDA (from SAAB Central/900 Aero) has had a ride and a close inspection. TBH, I'm very happy with the stock setup which hits

0.8 bar spikes (4th gear, uphill with very cold weather) and settles at 0.75 bar usually. Okay, the wastegate is set to 0.35 bar, rather than 0.32 bar ... but the APC box is stock :) It feels alright ... especially since the fuelling is right now!

I'll want to setup a variety of LEDs to "watch" APC function before putting my uprated box back in for anything longer than the occasional mischief at the weekends! K-Star is something for the future ...

Before he had it fully setup, he took me for a spin arround Angelsey at the trackday 2 years ago. Was a fantastically smooth drive, non of the usual thumps and bangs that one expects from a 900, as he had had it fully rebushed.

And the power when it came in was awesome. The plumbing for his water injection and FMIC are something else too.

in article snipped-for-privacy@individual.net, Grunff at snipped-for-privacy@ixxa.com wrote on 12/02/2005 18:37:

I happened to mention this to my mechanics today (along with a whole raft of other jibberish ... My brain was actually working today) and they thought it wasn't worth the hassle. They did say that the early Swedish 900s did come with lambda probe controlled CIS systems. Not the UK though.

Paul

1989 900 Turbo S
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