Saab 900 air mass meter

All ye who are technically competent, please pass on to the next story. This is for the tech duds like me.
Some of you may recall that I had some issues late last year with my 1985 Saab 900 Aero. The car would develop this tendency to jerk around a lot.
At first, we thought it was the fuel pump playing up, but $400 and a replacement later, we learned that wasn’t the case. Matt the fudgepacker correctly diagnosed the problem as being the Air Mass Meter. These are pretty expensive to buy new (around $800 here in Oz) so any sort of fix would do. Matt provided the simplest answer possible – A quick tap on the head of the unit and it seemed to right itself. It worked on the odd occasion it was needed after that, so I didn’t worry too much.
The problem was long forgotten until earlier this week, when the car developed it’s jerkiness once again and no amount of tapping on the AMM would set it straight.
Hesitating to pony up for a new unit, I rang a spare parts supplier in Melbourne and got them to ship over what they thought was a good second hand unit. I fitted the unit to the car today and it ran even worse than when I had my old part on it. Here’s the part, so you know what it looks like:
Saab AMM
That’s actually upside down to how you see it in your engine bay, but the battery ran out in my camera before I could take another shot ๐Ÿ™
So whilst my part was off the car, I thought I’d take it into my local Saab specialist, Steve E, so that he could have a look. Steve tested the unit and found it had been adjusted at some point. Once it was adjusted back to the proper settings, I took it home, reinstalled it, and now the car’s running as good as gold.
So what was the adjustment?
Here’s a look at the unit from a different angle:
Saab AMM
As you can see, there’s six pins in the plug for this unit. The test involved putting a multimeter on pins 3 and 6 and measuring the ohms. It should read 380 ohms. Mine was reading somewhere up past 530 ohms. The supposedly good replacement part I got from Melbourne was reading 995 ohms!!
You can see a gold-colored adjusting screw just to the right of the plug in that photo. That screw adjusts whatever it is that adjusts the ohms readout. Steve simply turned the adjusting screw until it read 380 on the multimeter.
How the AMM works (my limited understanding) – the computer sends a current through a filament in the AMM, which is cooled by the air passing it. If there’s more air passing by and cooling the filament (and going on into the engine) then the AMM boosts the current in order to maintain a set temperature in the filament. The variations in current required tell the computers how much air is coming into the engine and therefore, how much fuel is needed to match the air and create an optimum mix.
I assume that if there was an incorrect setting, such as that on my unit (where it was 500+ ohms instead of 380), then it would be misreading the volume of air that it’s meant to measure, hence the rough running that I was experiencing from time to time.
I believe the AMM is also commonly referred to as the Mass Air Flow sensor (or MAF)

Saab vs Audi vs BMW

Here’s a chart. An interesting chart.
Buy the Audi for badge value only. No other reason stacks up, if you ask me (with the possible exception where the car’s interior is the only thing in the world that matters to you – and even that’s subjective)
Saab Audi BMW

Tech Time: Saab 2.8 litre V6

Once again, armed with photographs from the Saab TurboX Media Drive, I’m coming to you via the internet with information that you must, at all costs, absorb and hold dear because it’s going to be on the final exam.

Today’s topic: the GM 2.8 liter V6 in turbocharged form as in the upcoming Saab TurboX.
Oy, this is one smooth engine. After all, it’s won awards from people who really know a thing or two about engines, so you expect some refinement. This engine, as I’ve said before, has power and torque available from the minute that you stomp on the gas pedal. So, you really want to know how that power is made so quickly and smoothly, don’t you? Of course you do!

Well, here’s the secret: it has six cylinders.

And here’s the other secret: the turbocharger has two scrolls.

Now, I’m not advocating a wholesale change, and I’m not saying that everyone needs a 2.8 liter turbocharged V6, but I am saying that it’s nice to have in your product line because some people, myself included, will want the performance that it offers.

While at the Saab TurboX Media Drive, I studied the display V6 for a few minutes. After orienting myself and studying the airflow and the layout, the first thing that struck me was the additional piping and routing required to make a V arrangement work. On the four-cylinder Saabs, everything is easily routed from the same side of the inline bank of cylinders, while the V6 has to route exhaust to and inlet air from a single point on one side of the engine: the turbocharger. The well-sculpted inlets of the Saab V6 are a testament to both design and manufacturing prowess, but what a tangle it appears to be.

While we’re on the subject of metals, take a good look at the engine block and the cylinder heads. Casting technology has come a long way in just the past ten or twenty years. The detail and specialized shaping of each component is truly amazing and most certainly adds efficiency and performance.

The two-scroll turbocharger by Mitsubishi enhances the driver experience by allowing a workable variable inlet arrangment that gets the turbocharger impeller spinning at operating speeds with even a small change in exhaust flow. That is, turbo “lag” is greatly reduced. I can tell you first-hand that it works. With thirty years of turbocharging experience, Saab certainly made good choices with this one.

Not only is it easy to see the air and exhaust routing with this cutaway, it’s also to easy to see the 60 degree angle that helps to balance the engine and make the whole assembly a little shorter from top to bottom.

Notice that the exhaust manifolds are lined with stainless steel to keep the aluminum alloy from being heat worked over the life of the engine. That’s reliability, folks. Kudos to Trollhattan.

2010 Saab 9-5 to show in Geneva, 2009

I mentioned to you that there was going to be a GM Next presentation this week, right?
Hot off the press from Djup Strupe in Europe….

Well to be short, the new 9-5 is absolutely magnificent (both the sedan and the estate are beautiful). The cars were presented last in the GMNext conference, almost 6000 people joined this event last evening.
Unfortunately the 9-5’s weren’t real cars but dummies without engines and real suspension, so the cars had to be pulled in with ropes.
We also saw the new 9-4x, the final version (even better looking than the concept, more European)
And finally a 9-3 CrossRoad kind of car, something like the Audi A6 Allroad or the Volvo V70 CrossCountry.
The introduction of the 9-5 will not take place in Paris this Autumn, it’s going to be Geneva once again.

Oh yeah, baby!!!
It seems that my previous prediction, based on a quote from Steve Shannon, that the Saab 9-5 would debut at the Paris Motor Show later in 2008, was incorrect. I’m more than happy to exchange an error for a confirmed date, though, especially when it means we’ve now got something else to look forward to in Paris later this year ๐Ÿ™‚
Bring it on. And in a hatchback form too, please……

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