The Four Banger We’ll Never Forget: SAAB B234 Turbo Engine


SAAB B234 represents a journey from a borrowed design to what is generally accepted as one of the best four-cylinder engines built in recent history. At the very minimum, the B234 rates as one of the best engines SAAB have ever made.

Our goal with this short guide is to introduce the B234 to those who aren’t familiar with it and explain just how important this engine is in the grand car modding scheme.

SAAB’s Ticket to the Engine Hall of Fame

The so-called engine hall of fame is packed full of awesome designs from all over the world. Every or almost every manufacturer has contributed to this legendary roster that grows each year.

What makes an engine worth such high praise?

The answer to this question varies from person to person; however, most will say it’s some combination of reliability and performance. But wait, things get even more interesting. A small group of engines stands out, even from the other hall of fame members.

We’re talking about engines that aren’t just popular for their power or reliability, but also their versatility. Engines such as the K20/24, the mighty LS, and of course, the B234 from SAAB.

All of these have in common that people swap them into all kinds of vehicles. SAAB’s B234 has always been a popular swap option, but it is becoming even more so now that donor cars are abundant.

What exactly makes the B234 so suitable for swaps and tuning? Let’s find out!

Saab B234R The Four Banger We'll Never Forget: SAAB B234 Turbo Engine at eEuroparts.com

Building Upon a Solid Foundation

The story of B234 starts way back in 1968. Back then, Triumph Motor Company designed the first H pattern slant-4 engine. They’ve used the original 1.7-liter version in their Triumph Dolomite 1850 and later models.

At this point, you’re probably wondering what does SAAB has to do with Triumph? Back in the day, while Triumph was designing the slant-four engine, SAAB was also trying to build a motor of their own.

The company was putting together the SAAB 99, and they needed something to power this new model. After some time and several failed attempts to build something that met their needs, the brass at SAAB realized that building an engine from scratch is neither easy nor cheap.

Fortunately for them, they had Harry Ricardo’s consultancy firm working for them. It just so happened that Ricardo was well-informed about what Triumph was building. His idea was to have SAAB adopt the engine because it was simply better than the 1.2-liter motor they were unsuccessfully putting together in-house.

That is precisely what happened. SAAB took the slant-four and used it in a variety of models. The original Triumph motor was later used as a foundation for the B series engines, which is where B234 originally comes from.

Saab B234R Block That is precisely what happened. SAAB took the slant-four and used it in a variety of models. The original Triumph motor was later used as a foundation for the B series engines, which is where B234 originally comes from.

The Slant Design

Slant engines are a rarity these days. So much so that even some of the most hardcore car enthusiasts don’t know they exist. However, the fact that they are rare doesn’t mean that they are bad. On the contrary, slant engines were known for a few fairly important benefits.

The slant engine differs from a standard inline design in cylinder orientation. With the slant design, you’re looking at 45 degrees of angle from the crankshaft to the combustion chamber. Such structure may come across as odd, but you’re getting more room for both intake and exhaust manifolds, and they allow the engine compartment to be thinner altogether.

Most importantly, slant engines are easy to make, which is why both Triumph and SAAB kept making them for a long time.

BMW with a Saab Engine Slant engines are a rarity these days. So much so that even some of the most hardcore car enthusiasts don't know they exist. However, the fact that they are rare doesn't mean that they are bad. On the contrary, slant engines were known for a few fairly important benefits.

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

B202 – The Prelude

To reach the B234, we have to first go through the B series and then the famous H series, which has spawned the B234. SAAB didn’t just use the Triumph slant four engines as a crutch to bridge a technological gap.

No, they’ve pretty much leaned on this engine hard, perfecting it through various iterations until they reached what is now known as one of the best turbocharged engines in the world.

Getting there wasn’t easy. SAAB had to jump a few hurdles to get the engine to work reliably with a turbocharger. For one, they had to get rid of the in-block water pump that caused all kinds of issues.

The redesigned version had the pump moved outside the block and chain driven. Not only was this solution easier to make, but it was far more reliable and simpler. The B series and H series were installed in everything ranging from the SAAB 99 to 9000, and 900.

Before B234, there were the B201 and B202. These were 2-liter versions of the H engine fitted with the new water pump, SAAB’s CIS fuel injection system, and a BOSCH distributor. The B201 was a 2-liter engine with a single overhead camshaft, while the B202 added another one, hence the altered designation.

The B202 was introduced in 1984 and was the powerhouse behind the SAAB 900. When they tried to push the 9000 series with it, things didn’t end so well. In fact, the 9000 wasn’t capable of going against the equivalent BMW or Mercedes-Benz of the era. Something new had to be devised.

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B234 is Born

The need for something more powerful has put SAAB in a very peculiar position. They could either build something new or just keep doing what they were doing up to that point. Naturally, they went with the latter option.

The new B234 features a larger displacement, being a 2.3-liter package, unlike the standard 2.0-liter B202. Instead of messing with the bore, SAAB simply increased the stroke to gain those .3 liters of displacement. The addition of some 12 mm to stroke gave the B234 a boxy, square appearance.

They went on to add balance shafts because there were excess vibrations without it. The addition of balance shafts gave the whole package a more refined feel. Next, SAAB introduced a set of oil squirters to keep the bottom end of pistons cold. Where SAAB really went a step further was adding forged connecting rods and a forged crankshaft.

What they’ve basically done is created a perfect stock platform for all kinds of tuning. Forged internals were capable of cranking out much more horsepower than the stock block had to offer. Combined with their standard 16v head, the B234 engine was ready to make history.

The boosted version delivered 9.25:1, while the naturally aspirated models got over a 10:1 compression ratio.

The Trionic Engine Management

When SAAB introduced the Trionic engine management systems in the 1993 SAAB 9000 series, they’ve essentially built the final piece of the B234 puzzle. Trionic computers were capable of making very fine corrections both to the fuel/air mixture and boost. The resulting engine got to be known as the B234R.

Paired with the capable manual transmission in the 9000 Aero, you could get 225hp out of one of these, as well as 300ft/lbs of torque. Those figures don’t look like much these days, but keep in mind that we’re talking about the early ’90s.

SAAB was one of the few brands that could deliver such power from a four-cylinder engine. For comparison, the next best thing was the Porsche 993 that made only 50 hp more. To make that additional 50 hp, Porsche had to use almost anywhere from 1.3 to 1.5 liter of additional displacement compared to the SAAB 9000 Aero and its B234R.

It didn’t take long before enthusiasts realized just what kind of weapon this engine really is.

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The Unsung Hero

Although the B324 engine’s story is obscure on its own, the Mitsubishi TD04HL-15 turbocharger they’ve used is talked about even less. The setup SAAB had put together includes this massive turbo, paired with an equally massive intercooler.

Such a combo did two things for the car – it provided tons of cold air, and it gave the engine miles of headroom. Headroom that would later be used to squeeze out crazy horsepower figures from stock engines. Oh, remember those forged internals? They added to the whole headroom situation as well.

Engine Oil Change Kit (5W40) (7 Liter) (X-CESS 8100)
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Popular Engine Swap Choice

The tuning potential of both B234 and B202 engines has made them a popular choice for all kinds of swap projects. Today, in 2020, the situation is even more hectic since you can get your hands on a B234R 9000 Aero for dirt cheap. There are running motors out there for $200 or less.

Because of that, you’ll see all kinds of Miata projects, franken-BMWs, and other cars being running H series turbo engines.

Engine Oil Change Kit (5W-40) (7 Liter) (X-CLEAN 8100)
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Quality SAAB Parts

If you’ve got a B234R or any version of this engine, sooner or later, you’ll have to change a worn-out part. We offer one of the largest catalogs of Genuine, OEM, and aftermarket parts for SAAB vehicles.

To find the parts you’re looking for, simply head over to our online store and select your vehicle in our navigation tool. Our system will crunch the data and give you a list of parts that match. Additionally, you can always use your VIN to get even more accurate results.

25 thoughts on “The Four Banger We’ll Never Forget: SAAB B234 Turbo Engine
    • 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.

  1. 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.

    • 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.

    • Hi
      Love my Saab – engine great. Live in New Zealand & hubby brought in all the hoses, as can’t get parts that easy. My problem is the roof rams have both stopped- anyone’s advice welcome

  2. 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!

  3. 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.

  4. 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!

  5. 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…

  6. Len Burke

    Great info from knowledgeable people.
    I have a 1997 faded red Aero auto with 209,000ks
    Love the car but drive a Chevy 2007 Saab 95.
    2.3 wagon. How much work would it take to 5 speed
    this old girl? Would love a 9000 Aero 5 speed.

    • Adam Goral

      Yes it will, of course some additional research will be required but from everything I know it should more or less be a direct replacement. The 2.3 liter in that 95 900s IS a B234, just not the R version which has the high output turbo. It’s called a B234i. Expect to have to swap over additional components like oil coolers and intake/exhaust piping, wiring harness, vacuum hoses etc to accommodate the new-to-you turbocharger system.

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