• CA18DET vs SR20DET Articles

    These two articles came from a member of Automotive Forums. Quite good when comparing the two engines and I think it dispells some common misconceptions and myths about the two engines.


    Article One

    Certainly there appears to be a great deal of interest out there in which one of Nissan’s ’hot-4’s is the hottest of the bunch.
    Nissan have made some very formidable hot 4’s in the past, but this note is aimed directly at S13 owners who may be looking at either the CA18DET or SR20DET engines.

    Firstly let me say that the SR was never designed to technically supersede the CA in any way other that cost. As with natural evolution and development the SR became more powerful. How much of that power is directly attributed to the fact that it is a 2 litre rather than only 1800cc?
    Many of the famed benefits of the SR20DET were in the CA18DET too. Piston oil squirters and crank stud girdle for starters.

    Externally, The 2 engines look completely different, and they should. The first obvious difference is the SR’s shiny alloy block, Next you notice the different inlet manifolds. The list goes on. Don’t mistake that alloy bloke as being lightweight either – there is that much alloy in the thing to keep it strong that they weigh no less than the CA.

    A lot of people refer to the CA as ‘the plastic motor’ – why I don’t know, when the SR has exactly the same item made from plastic right on top too. Obviously the CA looks a bit boxy and I guess plasticcy (?), but….

    Lets take a quick look at the intake design of the 2 engines. The SR uses a 4 runner manifold and a 4 port head. Standard garden variety manifold design. The CA on the other hand starts with a 4 runner manifold and then splits into 8, entering the head as an 8 runner manifold. Every second runner is only flowing air under certain circumstances (high air flow). Much more sophisticated design, and much more expensive to produce. I think the theory of this manifold design was to regain some low-down torque missing as a result of the comparatively lumpy camshafts used in the engine.
    Some feel that the combustion chamber design of the SR20 is also better than the CA, however I am yet to hear that report from anyone who has actually seen both types of engine in S13 RWD trim for a valid comparison.
    There’s more to the head than that too. Looking above the valves, the first thing that grabs you with the SR is that is only has 4 cam lobes per cam, not 8. Doesn’t it have 8 valves per side? Yep, and to get around that Nissan decided to use a rocker arm arrangement to actuate paired valves simultaneously from the single lobe. Not a bad way to do it actually. Certainly cheap to make, but at the cost of increased valve train losses and noise.

    The CA on the other hand has true 8 lobe cams which act directly on the top of the valves. Minimal components. Maximum revs, and no noise.
    The SR has also gone back to the classic timing chain idea, and dropped the tooth belt. My theory here is it has something to do with reduced maintenance costs and less damage when the belts fly from lack of maintenance.

    Obviously, the SR is a bigger engine in capacity, it has a relatively long stroke and is ‘over-square’ in design, meaning that the stroke is longer than the width of the bore. Fortunately the stroke to rod length ratio is at such a point that the engine can still rev, but it suffers classically from excess stroke. Sure, they rev out, but not anywhere near as willingly as the little CA with it’s square design (stroke=bore).

    Many hi-po USA engines are using oversized pistons from the 300ZX, bringing the stroke/bore relationship back a bit, and providing a cheap source for forged pistons and further increased capacity.

    Sure they rev out OK, but not anywhere near the same as a CA. I'm talking stock engines here too, not comparing an SR with aftermarket cams on modified lobe centres, which wouldn’t be a fair comparison now would it!
    In retaliation to the plastic tag for the CA, I would now like to refer to the SR as Nissan’s 4 cyl domestic truck engine. The TRUCK MOTOR !!!

    So, in conclusion, there is no real winner in this debate - they are not predecessor and successor that is for sure.

    I guess the best thing about the SR is that it is almost still in production (although getting very old by other examples) and is well supported by the aftermarket industry. This makes it an excellent choice if you are going to be rebuilding the engine for a specific purpose or inflicting a lot of bolt-ons to it.
    There are obviously many more variations between the engines. This writing is simply a small part of it. I will continue this article soon. Any comments appreciated and if anyone has some facts of would like to contribute, please forward them to me lumpy@wasp.net.au
    The CA will have to remain the unsung hero.

    Article Two

    Start talking about four-cylinder Nissan performance and people automatically think of the SR20-DET engine. There's no denying the brilliance of the SR20-DET motor, yet its popularity has to some extent overshadowed the CA18DET engine.

    There are in fact those who believe the CA18DET to be a better all round package, including Glenn Campbell from Glenn Campbell Motorsport. Glenn has been messing around with Nissan engines for more years than he cares to remember and has swapped more engines, turbo's and ECU's than most of us have had hot dinners.

    Glenn was keen to ensure that this article didn't attempt to compare the SR20DET with the CA18DET, as that would be a pointless exercise. We were instead convinced - and rightly so - to look at the CA18DET on its own merits and as it turns out, the merits are numerous.

    Firstly though, some basic background info. Nissan's CA engine family began in the 1980s, in various formats and configurations, from 1600cc through to 2000cc, single cam, twin cam, atmo, turbo, 4 plug, 8 plug, DIS etc - I am sure you get the picture - it is quite the 'mule'.

    The S13 is certainly the most popular of the many Nissan Silvia models and although never officially imported Down Under, their popularity as a low volume import over the years means they are dirt cheap. How cheap? From as little as $7,000. These early Silvias came with the CA18DET engine and still offer terrific performance value for your dollar. Atmo versions were also available.

    While many enthusiasts quickly remove the original CA18DET engine from their Silvia and go searching for a later SR20DET, building the CA18DET motor can offer surprising performance for relatively lower cost. "A lot of people throw a few grand at an SR20DET conversion for their S13 instead of the CA that was in it's place then leave it stock for budget reasons. It makes much better sense to me to leave the CA in place and spend the money on it instead."

    This also applies to the Nissan 180SX, which followed on from the first of the Silvias and also came Down Under in sufficient numbers with a CA18DET under the bonnet. Also featuring the CA18DET motor were some early import Bluebirds, which primarily ran as AWD auto cars. From an Australian sales perspective, the CA was featured in N13 Pulsar EXA coupes (CA16DE and CA18DE), late bluebirds (CA20E), Pintaras (CA20E) and Gazelles (CA20E).
    "One big advantage the CA has over the SR or even the old famed FJ is it's physical size. The SR and FJ are comparatively large engines and that makes them hard to use in conversions into other cars and models." But enough of the background info and onto what makes the CA18DET such a great engine for your next performance project. Over to you Glenn!

    "The CA18DET is not an alloy engine - it's all iron and basically bulletproof.
    With direct fire ignition, spark plug mounted coils, oil sprays for the pistons bases and a strengthening girdle around the main caps, the CA18DET was in many ways ahead of its time and still a brilliant performance platform today."

    Indeed, but the CA18DET's advanced features ultimately led to its demise, as Nissan decided it was too costly to produce. Some of its features were carried over to other engines such as the SR20DET, leading many to falsely believe that the SR evolved from the CA. No matter, the CA18DET also features a number of simplistic design features, which Glenn particularly likes.

    "The cams act directly on the top of the valves via a hydraulic follower for one thing, while a ribbed belt instead of a chain is used to actually drive the cams. Sure, having a dry belt arrangement does little for power but it keeps the engine noise a lot quieter. I have seen a number of SR cars come in through the import yards and they literally sound like diesel trucks. The single row timing chain on the SR can get very noisy indeed, and in addition the valve train design of the SR is particularly sensitive to lubrication, and given the fact that most Japanese import engines would appear to have never had an oil change, they become very susceptible to wear.