AmericanBornSilvia

I know that you can do a ca18det swap..just wondering if there are definite advantages (price, performance, upgradeability)

ca18guy

Here is a quick comparision of the SR versus CA.

The following is Glenn "Lumpy" Campbell comment on the SR20 vs CA18:

Some Points of Interest – the CA18DET –vs- SR20DET

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 [email protected]

The CA will have to remain the unsung hero.



*** Glenn LUMPY Campbell ***

Racing, Performance, Motorsport (RPM)