What Lies Beneath: The Saab APC System

During Saab-Scania's salad days of the 1970s and 1980s, its interests were varied and far-ranging. Aerospace, automotive, defense, and even computing were all areas of research within the realm of the quirky Swedish company. The benefits of turbocharging - originally a means to compensate for altitude on piston-driven aircraft - were well understood to Saab. The company became known as a bit of a pioneer in the relatively under-developed field of turbocharging cars in 1978 with the Saab 99 Turbo. The 99 saw to it that the company with fighter-jet heritage had cars with performance to match. The old Triumph-based "B-Engine" was suddenly a force to be reckoned with thanks to the addition of the little exhaust-driven turbine.

The improved "H" engine found its way into the 99 (still sold in Europe at the time) and 900 by 1981. The following year, the turbocharged models would be fitted with the revolutionary Automatic Performance Control (APC) System. Saab has always believed in making cars that were not only well-built, safe, enjoyable to drive, but also practical. The APC system made it possible for the engine of turbocharged Saabs to compensate for pre-detonation or "knock" caused by low-octane or poor quality gasoline, carbon deposits, high operating temperatures, poor tuning due to lack of maintenance and so-on. Furthermore, this allowed the compression ratio of the engine to be higher, thus increasing fuel economy by taking greater advantage the available energy in the fuel. The Saab driver could now have performance, and afford it too.

The Basics of APC Operating Principals:

Knock occurs when the temperature inside of a cylinder's combustion chamber becomes high enough to detonate the fuel/air mixture before intended by the spark plug - near top-dead-center of the compression stroke. Since forced induction naturally raises pressures, the compression ratio of a turbocharged engine must be low enough to ensure knock does not ever occur. This does not mean that a turbocharged engine cannot happily run at higher boost pressures or compression ratios, it simply means that the conditions must be right.
Basic turbocharging principals dictate fitment of a wastegate to allow excess exhaust gasses to bypass the turbocharger, thus preventing too much boost from entering the intake of the engine. It is operated by a pressure line from the compressor side which forces a diaphragm to open the wastegate once boost levels become too high.

1) Knock Sensor

2) APC "Brain Box"

3) Pressure Transducer

4) Solenoid Valve

5) RPM Sensor

One part of the APC system's job is to act as a regulator for the wastegate, thereby controlling engine boost. Rather than the wastegate's line running directly from the turbocharger itself, it is re-routed to the solenoid valve (#4). This valve is controlled by the APC box (#2) and has the ability to override the function of the wastegate.
The APC box is connected to a knock sensor (#1) which can detect if pre-detonation is occurring within the engine, and also to an RPM sensor (#5) to factor in engine rotational speed versus intake manifold pressure, as determined by the pressure transducer (#3). If the APC system detects knock, it will allow the wastegate to open sooner and reduce turbo boost to alleviate the problem. Because of this ability, this is why Saab was able to maintain a higher compression ratio in their APC-fitted turbocharged cars. Before APC, the ratios for turbo "B201" engines was 7.2 to 1. This increased to 8.5 to 1 with APC and, on the 16-valve "B202" engine, 9 to 1. APC can also control fuel delivery to an extent. When boost becomes excessively high, due to a stuck wastegate or misguided modding for example, it has the ability to cut fuel to the engine.

As the name suggests, Automatic Performance Control also controls performance - with the emphasis being on performance. It is not simply a means to prevent the engine from destroying itself, but also a way to vary tuning for the sake of economy, emissions, simple marketing strategy, etc. Saab's own SPG model 900 used a tweaked APC box (known in the Saab world as the "Red Box" to allow for a more powerful engine.) This is where things get rather complicated.
Exactly how the APC's "brain" works has been a part of Saab lore for decades now. To this day there are conflicting and diverging schools of thought on how a would-be Saab tuner can go about tweaking the APC for more power. They more-or-less all involve three circuit board potentiometers ambiguously labeled P, F, and K as well as some playing around with transistors and a soldering iron.
Though this author admits to having spent some time boldly tinkering with the APC box of his own 900 Turbo, this is not something for the weary or faint-of-heart. For those interested, I will direct you here but beware - more than once I've gleefully watched my Saab's boost gauge eagerly run into the red, only to have all the boost suddenly dump and the fuel delivery cut out and leave me coasting at 75 mph trying to restart the car. After a while, you may just find yourself tearing the box apart again to turn the screws back to their original settings, desperately hoping to regain the driveability of a normally functioning APC.

The APC system lived on in Saab turbos relatively unaltered until 1990. For the 9000 models only, which were fitted with direct ignition, DI/APC integrated the engine's ignition control into the mix. Therefore, the system was able to control both turbo boost as well as ignition timing to keep everything running smoothly.
The success of the APC system certainly didn't go unnoticed. Today, nearly all turbocharged cars have a similar system in place. Personally, this has allowed my cheap self to be running low-octane gas in not only my APC equipped Saab, but my Volkswagen with a 1.8T as well. Many Volvo enthusiasts have adopted and adapted APC functionality to their old 240 and 740 turbos.

Unfortunately, and no doubt thanks to years of General Motors ownership, it's been quite some time since we've seen truly great and unique innovations like this from Saab, but lest we forget, we must give a nod to Trollhattan.

6 volt to 12 volt conversion on a 1969 Renault 4.

The car receiving the 12 volt system is this 1969 Renault 4:


It's an all original, mostly rust free car with about 80,000 kilometers. I purchased it for the price of the paperwork to transfer the title over two years ago and I haven't done anything to it since, with the exception of more or less looking for a cheap 6 volt battery to get it going. That didn't happen; the part of me that wants to keep it original lost the battle to the part of me that wants to drive it and I decided to convert it it to 12 volt.

So what's involved in this swap? First you need all the parts. This is when you're glad you have a parts car gracefully rusting in your backyard. Upon closer inspection of the parts car you will undoubtedly also be glad you have a tetanus booster shot.

I've owned this 1974 Renault 4 since 2006. It ran quite rough, overheated constantly and it's much rustier than photos make it out to be so I parked it when the started died.

Here are some of the parts pulled from the 12v 1974 that you'll need for the swap:

The voltage regulator, the coil, the condenser, two headlight bulbs, the only two remaining tail light bulbs and the generator. Other items not pictured are the front turn signal bulbs, the wiper motor (dead on both the 1974 and the 1969), the instrument cluster lights and obviously a 12v battery. Note that you do not need the 12v starter; the 6v one holds up fine, it just spins faster. The wiring and the switches carry over as well.

First step is to remove all the old 6v bulbs and replace them with 12v ones. Clean out dirty sockets while you're at it, too.

Next step, remove the generator. Before you disconnect anything pay attention to which wire goes where! Take a picture, draw a diagram, whatever helps you get it right when you put the 12v one on. On a Renault 4 of this vintage you need to remove the fan and the fan pulley to get out the bolt that holds the generator to its mount. The fan is held on by four 13mm bolts mating it to the shaft on the water pump and a 17mm bolt that holds the whole assembly on. Remove those, remove the 17mm bolt that holds the generator in place, remove the belt and remove the generator. It's good practice to have a new belt to put back on.

With the generator out (see picture above) you can easily get to the coil and the condenser. Remove and replace (fairly straightforward.)

Next up is the voltage regulator. On a Renault 4 it's held on by two 8mm bolts on either side. Like for the generator, take a picture or draw a diagram to remember what goes where.

Once everything is back together it should look like this:

And.. success!

Everything works fine.. sort of. It won't fire, I'll look into why in the next few days (it may need new points.)

What Lies Beneath: Porsche Sportomatic

Porsche’s Tiptronic system has become quite familiar to the automotive community by now. However, the Tiptronic system was not the first time Porsche offered a clutch-less manual transmission. In 1968, the Sportomatic semi-automatic 4-speed was introduced as an optional transmission to the standard 5-speed manual on the 911T and E. (though there were approximately 5 Sportomatic 914s made) It was quite an interesting design indeed. Porsche took their type 905 transmission and modified it to contain a torque converter along with a vacuum operated clutch.

When a driver changes gear, he simply grabs the shift knob and selects a different ratio. Beneath the shift knob, there is a micro switch that is triggered when the knob is depressed slightly. The switch then activates a vacuum valve that in turn operates a vacuum diaphragm. This diaphragm then operates the clutch and thus allowing the changing of gears and therefore eliminating the need for a clutch pedal. Before power from the engine reaches the clutch, it flows through a torque converter. This allows the driver to stop without putting the transmission in neutral. A feature that is particularly helpful in stop-and-go driving. Though the Sportomatic is a ‘clutch-less manual’, the ratios in the transmission are not shown as 1,2,3,4 and so on. Instead, Sportomatic ratios include L, D, D3, and D4. Furthermore there is a Park feature, as on an automatic, and naturally reverse.

Porsche’s period brochures indicate how to chose the correct gear:

L (Low): For ascending and descending steep grades or for slush, mud and snow.

D (Drive): Normal driving from 0-60 miles per hour. For rapid acceleration, the transmission can be shifted through all ratios like a typical manual transmission.

D3 & D4: For highway cruising. D4 is essentially overdrive, while D3 can be used for passing and downshifting under braking.

P (Park): This is necessary since due to the torque converter there is no mechanical link between the engine and transmission.

R (Reverse): Acts as it would in an automatic. It can only be selected if the car is at a complete stop. Slight increase in engine speed may be necessary to actually move the car.

Later, as 911 engines increased in power, a stronger Sportomatic was necessary. In 1972 the type 925 Sportomatic was introduced using the same casing as the type 915 manual. By 1975, engine capacity and power in such cars as the 911S had increased to the point where once again the Sportomatic transmission was too weak. Since the system incorporates a torque converter, only three speeds were necessary. This allowed for larger and stronger gears without increasing the size of the transmission case.

By 1979, Sportomatic had ceased development and was dropped from the line-up. Porsche released the 928 in 1977, which was available with a fully automatic transmission sourced from Mercedes-Benz, and later the 944 also had an optional 3-speed automatic. Porsche didn’t come out with another ‘clutch-less manual’ until 1992 with the introduction of Tiptronic.

Mercedes-Benz 240D transmission removal.

Just a disclaimer: I did this quite quickly and didn't pay as much attention as I should have to getting photos or getting the size of the tools. Also, this car had 318,xxx miles on the notoriously unreliable Mercedes odometer, meaning some of the bolts or screws might not be original to the car, meaning they might be different than your car. This one was different (and much more straightforward) than other 240Ds I've done, same way I'm sure my 300D is different than this, but the basic concept is the same. Also, it should be pointed out that I have no idea what year this car is, all ID plates were gone. It's your standard, U.S. spec 240D though.

The very first thing I did was get under the car and spray PB Blaster on all the bolts I'd be dealing with. This will help get them loose and doing it first avoids having to wait for the PB to work.

I chose to remove the gearshift assembly, you don't have to. To do that, start by crawling under the car. The three shift rods are held on by clips. Remove them using a flathead screwdriver and the rods slide out. Next, from inside the car, remove the center console where your hazard switch is. This one was held on by two screws near the end of it. Unscrew those, undo the connection to the hazard switch (and the power windows, if applicable) and the console comes out. Next, the actual assembly is held on by four bolts (I believe they're 10mm), undo those, unplug the reverse light switch and the shifter assembly slides out.

Next step (and in my opinion the trickiest) is the driveshaft. At the front, there are six bolts that keep the end of the driveshaft, the driveshaft donut and the output shaft of the transmission in one piece. This is where it can differ greatly from car to car: these were bolts with a 15mm head and a 17mm nut on the end. I've seen w123s that use allen head bolts instead which was an incredibly frustrating setup.

The transmission crossmember has holes provided to slip a wrench in there. Insert the wrench and make sure it goes around the nut. Then, using a ratchet with a 15mm extension, start working away on the bolts. A breaker bar is handy, borderline necessary, to get these bolts loose.

Once you've removed all six bolts, remove the driveshaft mount on the center of the car. This is held on by two 17mm bolts. Softly wiggle the loose end of the driveshaft until it's no longer attached to the transmission.

You'll notice the exhaust is attached to the transmission. Unbolt the two 13mm bolts that hold the mount on and the exhaust will drop. Depending on your car it may be necessary to unbolt the exhaust at the exhaust manifold, too.

Using a 12mm wrench, remove the hydraulic clutch line going into the slave cylinder and remove the speedometer cable. That should be everything attached to the transmission. Except that, wait, it's still attached to the engine.

Start undoing the bolts that hold the transmission on. They're 17mm. Some are simple bolts, some are bolts with nuts behind them, one also has a ground cable. You also need to unbolt the starter bolts which are allen bolts of a size that I cannot recall. You have some coolant hoses in the way for the top bolts. You can work around them, or you can choose to remove them. On a 4-cylinder, you have plenty of room between the engine and the firewall to get to the top bolts. This clearance is MUCH less on a 5-cylinder car and consequently those bolts are tougher to get to.

Double check that all bolts are out (and keep track of them-- don't lose any!) You can now unbolt the transmission mount (which also acts as an engine mount.) These are once again two 17mm bolts and they're the reason why I said above that dropping the exhaust from the exhaust manifold may not be a bad idea, it's easier to get to the passenger side one. You'll naturally notice the transmission start dropping.

Making damn sure you have something to set the transmission down on (couple of old rims and a piece of wood will do), slide the transmission out. It is not light so I'd advise against trying to get it onto your chest.

If you're trying to get to the clutch out, you're not done yet. Get your allen wrench set back out and unbolt the six bolts that hold it on (a breaker bar is handy.) You'll need to block the flywheel so it doesn't move. Once that's off, the clutch slides out.

And, if like me you need to remove the flywheel, you're still not done. There are twelve 12mm bolts that need to be undone. They're very tight and a breaker bar is handy, once again. Use something to block the flywheel and untight them all.

Reassembly is straightforward and is the reverse of disassembly. Align the clutch using the proper tool and it's always good practice to replace the release bearing and the pressure plate. Be VERY careful not to turn the engine the wrong way when torquing the flywheel/pressure plate. Now is also a good time to replace that worn driveshaft donut.

Changing the fuel filters on a 300D.

Since the week I bought the car, I have had both the main fuel filter and the pre-filter bouncing around the rear footwells of the car. I turn, they turn too, it's all fun and games until I hit a hill and the car essentially goes nowhere. Clearly the hour to change the filters had rang. So I naturally put it off for a bit. I got around to it this morning, it's a fairly simple job.

I changed the pre-filter first. It's right by the injection pump on the driver's side of the engine. It has a line on either end held on by a ring.

Unscrew the ring, take the filter out, put your finger on the end of the line and quickly put the end of the new filter in there. Set the old filter down above the headlight. Realize it's leaking diesel and toss it on the ground where it will continue to leak. Make sure the new filter is in all the way and tighten the ring. Repeat the process for the other end of the line.

You've now changed the pre-filter. The main filter is a bit different. It looks just like a regular oil filter:

That said, you might be tempted to grab your oil filter wrench and attack it. That would not do much good. On the photo above, look at where my key is pointing-- that's the bolt that holds it in. Now, as much as I'd like to tell you what size that is, I have no idea. It's larger than a 19mm, I didn't have anything larger on hand and didn't fancy digging through my garage to find one so I used an adjustable wrench, worked fine.

Undo the bolt, you'll see the filter slowly start to drop. This is full of diesel and, much like the last one, will leak. Let it leak onto the pavement for a bit until you decide to use the roll of paper towels you brought down for this very purpose.

Once the top bolt is loose you can unscrew the filter. Toss it next to pre-filter where they will leak in harmony, nicely complementing the oil stains from your valve cover gasket.

Now that the filter is off it gets interesting. You need to prime the car because air gets into the injection system. The injection pump has a little knob that you use to prime it. Alternatively, Ian told me of a way that involves cracking open the injector lines until gas comes out.

I did none of that. I filled the main filter with diesel until it was almost to the top, screwed it back on, tightened the bolt. Then I got in the car and cranked it until it started. And it did. And it died. So I cranked it again until it started, this time it started faster and ran fine, albeit with a shoddy idle, my treat every morning when I start it up.

Make sure everything is tight and that you haven't left any diesel-soaked paper towels in the engine bay, close the hood and start the car. Drive it around to see how it runs. While you're driving, you'll notice a mighty diesel smell. You'll likely worry about that diesel smell, you might even be tempted to turn the car off until you realize it comes from your hands. Park it, open the hood and inspect for leaks. If it all checks out okay, go inside and take a shower.

Fiat radiator.

I can say from experience that Fiat’s Uno is one of the most reliable car to ever come out of Torino. Yes, I just used "Fiat" and "reliable" in the same sentence. The Uno is amazingly basic in conception, economical to run and the availability of the FIRE engine make it a great used car, moreso than later Fiats. But, alas, nothing is perfect. This 1992 Uno (roughly 168,000 kilometers) has been in the family since new. It’s currently under my aunt’s ownership and has had a leaky radiator since January. She drove it as is, filling it up when she felt it needed it (i.e. never enough) until recently when the leak got worse and the car became undriveable. Only then did she finally decide to replace the radiator. I got a used radiator from a junkyard for 30E. It’s from an older Uno so it’s a bit smaller than the original one but it’ll do the job and it fits into the engine bay without modifications.

The whole process took about 25 minutes, it’s very straightforward on a car like this.

1) Remove the two clips at the top, undo the two coolant hoses, unplug the fan connection and pull out the old radiator.
2) With the radiator out, remove the three screws that hold the fan and its assembly.
3) Bolt the fan and its assembly to the new radiator.
4) Put the radiator back in its place, tighten the hoses and secure the clips, plug the fan connection back in.
5) Fill it with water and barring any issues with a used radiator, it’s good to go.

Euro Switch

I like European cars... and I like them the way the Europeans intended them to be. Therefore, one of the first things I did to my new daily-driver 2000 Volkswagen Golf 1.8T was install a European market light switch and disable the daytime running lights. 

I purchased the 'euro-switch' on eBay for $30 shipped. Not a bad deal, though I'm pretty sure it's a Chinese knock-off. Either way, it looks and functions exactly like the genuine article. The North-American market switch originally in the car had two positions. On, and off. Since I intend to (eventually anyway) get fog-lights for the VW and also wire up the rear fog light, and since the Euro-switch accommodates these features, it was a natural choice. More importantly though, it allows me to 'legally' de-activate the daytime running lights. (allowing for parking lights which are necessary to pass inspection without DRLs) Say what you will about the safety benefits of DRLs, but I hate the notion of driving around on a warm sunny day with my low-beams blazing away constantly because VW feels it's a necessary feature to make their cars more appealing in North America. Not to mention also that since this car goes through about 2 sets of headlight bulbs a year, driving without them on all the time should save me a decent amount on lightbulb costs. (I figure the switch will pay for itself for that reason alone within about 6 months)

Installation is simple, just pop out the old switch by pushing in and turning, and pop the new switch in. However, the DRLs will remain on when the switch is in the "O" (off) position unless you make a slight modification (or go about pulling relays out of the dash and involving yourself in a chore of a wiring job). I chose to simply bend back the one contact pin on the switch that allows the DLRs to come on, and therefore, when plugged in, the contact never actually makes contact. And that's all there is to it!

With either parking lights or headlights on, one click out activates the front fog lights and changes the icon green. Two clicks out activates the rear fog light. 

Pictured above are the low-beams activated. The city-light (the small dim bulb) remains on along with the high beam bulb. Previously, when the DRLs were on, only the low-beams (not the city lights) were on, until the headlight switch was turned to the "on" position.

Below just the parking lights are activated. Rather than illuminating the amber turning signal as with Jettas equiped with a "Euro-switch", the low-power city-lights come on.

Busting my Ball...joint...

Above you will notice a thoroughly failed ball joint on a 1993 Saab 900 Turbo. To be honest, I knew a while ago that I had a bad left front ball joint. I chose not to replace it in anticipation of retiring my Saab within the next week or so. However, almost as if the car knew I was being neglectful, it forced it's attention upon me rather suddenly while making a left hand turn during my lunch break. The right front of my car came crashing to the road rather violently, sending my wheel well up into the fender and taking the drive shaft with it. All much to the dismay of myself, other drivers, and the Millcreek police once they saw it sitting in the intersection of two high-traffic roads.

Not having my new car yet at that moment forced me to fix the problem immediately. Let me tell you, it wasn't exactly a joy. Fortunately the only problem that resulted from the drive shaft being literally torn from the transmission was a ripped rubber CV joint boot. Interestingly this part was the most difficult to locate and the drive shaft proved to be the biggest nuisance to re-install. 

I got the car back together and all was relatively right with the suspension again, but now my alternator has failed... and it's not getting fixed. I'm now officially (and somewhat unwillingly) a Volkswagen driver.

Bleeding green.

One afternoon I noticed a pool of coolant under my 300D. Further inspection revealed it was coming from the water pump. This car had all of the service records since new (it was a 1979 with 195,000 miles) and the words "water pump" didn't appear once so I believe it was original to the car.

The process is pretty straightforward, you don't even have to mess with the timing like you do in other cars (I'm looking at V6 Alfas here.)

1) Drain the coolant and remove the upper radiator hose.

2) Remove the bolts that hold the fan to the fan clutch. Use a box-end wrench but make sure it's a six point, NOT a twelve point. A twelve point sometimes won't get them off, I know-- I tried. Remove the fan, the fan clutch and the alternator belt. Removing the fan shroud isn't necessary the it gives you more access, I recommend it.

3) Remove the water pump bolts. Coolant will undoubtedly spew out so have something under the car ready to catch it unless you fancy having green snow on your driveway. Once the bolts are off, use a mallet to pound the water pump out of its housing.

4) Scrape off the old gasket material with a razor and dry it off. Spread gasket maker material around the pump and make sure not to go around the bolt holes. Put the new pump in its housing and tighten the bolts. Put the fan and its clutch back on (with a new alternator belt) and tighten those bolts. Put the radiator hose back on and fill the coolant. Check for leaks when it's all together.

While you're doing the water pump, change the thermostat as well. It's cheap, easy and a good precaution.

Saab vattenpump avhjälper

For about the last 5000 miles I've suspected the water pump on my 1993 Saab 900 was going to fail. The obvious thing to do would, of course, be replace it. But since I'm a poor college student and also generally pressed for time when it comes to doing more than topping off the perpetually dripping coolant, I didn't. This all came to a head on Easter Sunday when the original factory water pump with over 179,000 miles on it finally said "to hell with it" (in it's own metallic chirping sort of way) and released copious amounts of coolant all over a parking lot. In anticipation of the pump's immanent demise, I did get a replacement earlier in the week, which was conveniently sitting in a box behind the passenger's seat. And so, that day, I used my cheap Wal*Mart sourced emergency kit tools to replace the pump in the parking lot by my building. In my wisdom, I opted to leave my nice Craftsman toolbox with all the nice Craftsman tools in it at home - over 200 miles from my aging, high mileage car.

A long time ago I went through a spree of removing non-functional, heavy parts from my engine bay. Basically, my entire air conditioning system. This made the water pump job much easier since the AC compressor was not sitting right on top of everything I needed to get to. 

The process was more or less as follows:

-Gently push aside old, brittle, and very expensive rubber cooling hoses that are rubbing against alternator, and loosen rounded off alternator adjusting bolts. Also loosen power steering belt.

-Remove belts from pulleys, swear at car as you smack knuckles into firewall (Saab 900s have a backwards mounted engine remember)

-Remove water pump pulley, then remove water pump bolts.

-Whack water pump with tire iron so that it breaks free from housing and dumps gallons of coolant all over parking lot and your feet.

-Realize that you don't have a razor blade to scrape old gasket material off of the housing. Go up to your room (on the top floor of your building) and find that you have left your keys in the car and your door is locked. Then, go across hall and ask for a razor blade.

-Using the X-Acto blade, spend the next hour or so leaning into the fuse box and scrape all the old baked on and wet gasket material off the edge of housing. 

-If you're lucky you still have some gasket maker stuff from a previous project still sitting in your trunk. (and you never thought of getting any before committing to doing the pump job anyway) Use this to stick new paper gasket to new water pump, and install. 

-Since it's Easter Sunday and everywhere is closed, re-use one of the ancient 15 year old belts for the time being since the auto parts store only stocked two of the three required new belts at the time you purchased the pump a few days ago.

-Top off windshield washer fluid tank and use the now empty jug. Fill with water from a drinking fountain and pour it into the coolant tank. You don't have any new coolant since you never thought to get any on the way back to your building. Then, drive car very carefully, while keeping eye on temp gauge, to Wal*Mart (only place open on Easter) and buy coolant and top off tank. 

-Have a drink, then go finish some graphic design project due tomorrow morning.

EDIT: photo changed to more appropriate one of all-swedish products