Get To Know An Engine: The Saab B234R


The Saab B234R is regarded by many hardcore Saab fans as the greatest engine ever produced by the Swedish manufacturer.  That is, of course, all subjective.  However, there’s a reason why so many people that really know their stuff praise the engine.  In fact, because of junkyard availability the Saab B234R is actually becoming a relatively popular engine for swaps.  Why is that?  Well, let’s get started.

Saab B234R Block

The Saab B234 is a member of the ‘H’ family of engines first developed in the late 70s as a successor to the Triumph derived B engine, which was reaching its technical limits (especially with the advent of turbocharging).  When the H engine first appeared, it was fitted into the new Saab 900 at the very beginning of the 80s.  The problematic in-block water pump was replaced with a simple belt driven external unit, and a single cam sat on top.  CIS fuel injection was used, which generally was an excellent system, and plain old Bosch ignition powered up the distributor.  The new engine would be known as the B201, signalling the beginning of the iconic H engine family that would eventually continue on to 2009 in the 9-5.

A second camshaft was added in 1984 and the newly DOHC was renamed the B202 (two liter, two cams).  The B202 was Saab’s first quintessential production engine, and made it’s way into both the wildly popular Turbo Saab 900, as well as the freshly introduced Saab 9000 in 1985 where the strange slant block was configured to drop into the engine bay transversely.

The B202 struggled to make the 9000 a worthy adversary for some of the noteworthy competition such as the BMW 5-series, Mercedes 190,  and Audi 100, so it was time to get a fresh engine.

The Saab B234

Saab B234R

B234-balance-shaftsLaunching somewhere between 1989 and 1990, the H engine got a huge revamp.  Displacement was bumped to 2.3l by means of increasing stroke length to 90mm, up from 78.  The block was also taller in order to accommodate the longer stroke without shortening con rods, but bore stayed the same at 90mm.  That made the B234 perfectly square.  Balance shafts were added to give it a more luxurious feel, and oil squirters were added to cool the bottom of the pistons.  The compression ratio on turbo engines ended up at 9.25:1, while NA motors got over 10:1 CR’s. Normally Aspirated versions of the B234 made it into the NG900 as well.  The basic Saab 16v cylinder head stuck with only minor changes being made.

Connecting rods in the B234 were forged, as was the crankshaft.  Combined with the closed deck iron block, this created a very stout motor.  It would have to be, too, because Saab was about to bolt a large turbo and make the most powerful production engine in company history.

In 1993, Turbo Saab 9000’s were now shipping with Trionic engine management, allowing for a very precise electronic control of fuel, ignition, and boost pressure.  With the harmonious union of  the very strong torquey B234, a special Trionic 5 engine map, and a larger turbocharger, Saab punctuated a new chapter in it’s book “How to design a sleeper”  The B234R was born.

Automatic transmission cars were limited in power output, but if you were the type of person that preferred to shift yourself, you got the full 225hp and nearly 300ft/lbs of torque.  In 1993, this was a huge amount of power for a boxy four-cylinder front wheel drive sedan.  Even the top trim Porsche 993 turbo supercar only made around 50hp more at the time.

The turbocharger used was a Mitsubishi TD04HL-15, and charge air was cooled with a reasonable sized intercooler.  From the factory this setup still had miles of headroom, and it’s not uncommon for people to make big reliable power with only a few small modifications.

BMW with a Saab Engine

BMW E30 M3 with a Saab B234 Engine (click for details)

Because of this, it’s an extremely popular engine to swap into other cars, as mentioned above.  I know people that have picked up running B234’s for under $200.  I’m not just talking about people souping them up and putting them into other Saabs.  A cursory google search reveals successful swaps into Miatas, Subarus, BMW‘s, a whole variety of Opels, and more.  Our friends in the Saabs of Anarchy Lemons team even swapped its 2.0l brother (the B204) into a YJ Jeep Wrangler.  I personally know of a Mercedes 450SL that’s having its heavy smokey V8 replaced with a very cheap B234R.

Due to the low cost of purchase (unfortunately most Saab 9000’s these days can be found in recycling yards rather than on the road), the B234R has made it into several very successful LeMons racing cars, including an extremely successful Saab powered Nissan 300zx.  Someone even mounted a pair of B234R’s into a speedboat.  I think someday I personally would like to build a Volvo 142 with a B234R driving the rear wheels, due to the availability of custom bell housings to mate them with T5 gearboxes….goals.

If you have an engine you think is really cool, really interesting, or just plain weird, leave it in the comments below.  Maybe it will be featured on the next edition of “Get to know an engine”!

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20 thoughts on “Get To Know An Engine: The Saab B234R
  1. Harry

    Great article. Thanks! Have heard that the 202 is best for tuning due to lack of balance shafts,and being under square. Comments?

    • Adam Goral

      The B202 is a great engine for tuning, but of course only if you swap over the Trionic system on the B234R! The balance shafts can also be deleted on the B234, which is a route some people take. Honestly, the most popular route is to use a mixture of parts from the B234 and B235 to make the best combination (that M3 listed above uses the higher flowing B235 head). I’m not going to get into that now, but perhaps in the future it would be fun to get into.

  2. Gregg L

    I would think finding a decent B234R is getting tougher. Cars don’t hang around junkyards very long anymore and there weren’t really that many Aero 5-spds to begin with. The 9000 Aero AT cars had the smaller Garret turbo. I still daily drive my ’96 9000 Aero 5-spd and I have a spare B234R and 5-spd out of my wrecked ’97 9000 Aero. I also know I would not even consider parting with my spare for $200.

  3. Tom Lazouras

    Has anyone tried to drop one of these into a C900? I’ve got an 88 SPG with 250k miles and like the idea of a b234r swap…

    • Adam Goral

      Unfortunately the C900 has one of the weirdest configurations of any engine, and more specifically it is a slant so it won’t work. Fortunately with T5 you can get nearly all the benefits of the B234R minus the forged bottom end, in the B202. Of course none of that matters since the transmission will never be able to handle it.

      • Tom Lazouras

        Thanks Adam. I’ve been told that there’s a fix out there for the antiquated tranny, but haven’t been able to track down any info online. Maybe I should just enjoy what I have rather than turning it into a bottomless pit…

        • Adam Goral

          I’ve personally witnessed some of the strongest chillcast, racing gearset, steel reinforced everything, purpose built Saab 900 transmissions grenade under as little as 300hp. It’s just the nature of the design. Focus less on the power and more the chassis and balance, that’s where the C900 shines and there is no car that really feels like it out there.

  4. A.C. Smith

    I loved the article. There’s a guy in my neighborhood with a front yard & driveway full of Saabs, and I need to go pick his brain some time.

    I’d love it if you could write up one of these for the Volvo Whiteblock engine!

  5. Peter Dufferin

    I still use my 95 manual Aero regularly…..not all that pretty (dirt roads) but mechanically perfect with 320k km.
    Have had her 5 years and still love the drive. Oil changed every 5000 km and on a long highway trip is around 7 litres to 100 km. Have a 900 turbo convertible too…..they are great cars! Peter….Australia.

    • Leigh Dixon

      Like Peter Dufferin, I still have and occasionally drive my (black) 9000 manual Aero that is near perfect inside and out after 300k km. I need to sell either it or my 2002 9-5 Aero wagon, which I bought years ago to put the 9000 into semi-retirement. Reason: to make space for another Lotus. Unfortunately for US readers, the 9000 Aero is an Australian RHD model.

  6. John D Lincoln

    I still have a cherry ’97 9K Aero 5 spd. driven in New England summers only with no rust! It’s been warmed over slightly to 300hp with an SQR Stage4 but still gets 30MPG if you let it. It’s surprised a few 5.0 Mustangs!

  7. Phil

    We’ve had the privelidge of owning a few used SAABs, but the 9000 left the best impression due to the dependability, fuel economy, roominess, driving experience, fit and finish, capabilities in the snow, ability to start it no matter how frigid it was outside, the sleeper looks, etc. All of our 9000s were manuals – 91 blk/beige 9000T (underrated 225hp), ‘92 scarabe green/beige 9000T (225hp), ‘93 blk/blk 9000 Aero (underrated 225hp), ‘97 blk/blk 9000 Aero (modified-360hp).

    I used to get them serviced by a SAAB Master Tech who was it only a wealth of knowledge but also meticulous. In our vehicles, as well as those who had their vehicles serviced by him, trouble areas were addressed well in advance. For example, for the sake of head gasket longevity, on the ‘91 and the ‘92 a lower temperature thermostat and fan switch were used and augmented with the Mercedes Benz antifreeze. At 250k miles each when sold, they were still going strong on the original headgasket, timing chain, and turbos. Upon purchase of the ‘93 and the ‘97, their oil pans were dropped to ensure that there was no oil sludge buildup due to the heat from the catalytic converter. These two lar 9000s were sold as parts became scarce…

    In my opinion, neither of the last SAABs that we had, a 900SE and a 95Aero, were on the same league as the 9000. While the 900SE and the ‘95Aero had miles of plastic in their interiors, the 9000 had fabric covered A-pillars, quality leather, and real wood trim. I used to get complements by all who entered the vehicle. To boot neither the Clarion nor the HK system sounded bad.

    I lost count how many sport cars couldn’t keep up with 9000…Like others have said, they are scarce nowadays, even in junkyards, so finding a B234R with a 5speed will be though. I had considered securing a complete B234R drivetrain for a project at the time, but bellhousings to convert to a rear wheel drive (as my project required) were not readily available. The engine is a gem though considering that it does not have an air flow meter, has direct ignition with built in knock control, and that awesome automatic pressure control (APC). The Japanese imports certainly did not come with that type of technology…

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