In response to numerous questions about KA24 turbo setups, I have decided to finally just lay it all down for reference. Please don't post in this thread!
We've all heard it before: "I'm getting SR20!" "I'm getting RB20!" Many of us have been through the same tired loop of engine options. There is a plethora of engine swaps available for the 240SX, but there is only one thing that they all have in common: turbo.
All of us want it. The more rich of us buy fancy things like JDM front clips, loaded with RB20DET's, SR20DET's, CA18DET's, etc. Well, some of us just can't afford them. But there is still hope for us.
I love all the KA24's. I think the iron block 2.4 liter stands on it's own, a uniquely American engine in a proud, tall line of fine inline engines produced by Nissan. Being poor isn't the only reason to go KA-T. The ridiculously strong iron blocks and almost 600cc cylinder size create a joyous torquey power band. The enignes are by no means rev-happy from the factory, but with a turbo attached, the combination of low end torque and high end breathing power is absolutely amazing.
The bottom line is, the KA24 is a viable option for turbo, and I feel the best option for those of us who either love the KA or don't have enough for a JDM engine.
ENGINE COMPARISON
-"S13A" 1989-1990 KA24E
The KA24E is the single cam ECCS 2.4 liter 4-cylinder engine that accompanied the S13 chassis on it's debut in the US. The engine produced 140 brake horsepower and 155 lb/ft of torque at the crankshaft from the factory, with a compression ratio of 9.0:1. The engine was driven by a single overhead camshaft, making it the only SOHC 240SX motor. It is also the shortest lived motor on the USDM S chassis, making a 2 year run of production. Nissan's ECCS system was used for fuel delivery. The KA24E never did shake its reputation for being a truck motor, but it's also the first KA and part of the 240SX story. It is, all in all, an iron block KA.
The KA24E is a surprisingly viable candidate for turbocharging. There are advantages and disadvantages to the KA24E. Advantages include the top mount fuel rail, which makes powerful top-feed injectors a "drop-in" replacement. Second hand large top-feed injectors are plentiful in the US and Japan, coming from Diamond Stars and RX-7's, as well as others. Fuel injectors of high capacity are easier to find and more affordable for the KA24E than for the later, side-feed types. The KA24E is also not severely disadvantaged due to it's SOHC nature. The KA24E is a 12 valve motor, with 2 intake valves and 1 exhaust valve per cylinder. Camshaft replacement mods are also half as expensive as dual cam engines. The ECCS system is a top-down intake runner design, unlike the KA24DE. The intake runners are relatively restrictive when compared to later engines, especially the S14 intake manifolds, but can still allow for up to 400 horsepower. Fabricating larger intake runners would be simple. In addition, the compression was slightly lower on the KA24E, making it a slightly more viable candidate for increased boost. The most deleterious drawback to the KA24E is the scarcity of turbo manifolds for the engine. This is due to the fact that the exhaust ports are closely juxtaposed in 2 groups of 2 ports, unlike the even spacing of the KA24DE. Fabricating a turbo manifold is not difficult, however, and if you love the KA24E, this is surely your best bet.
-"S13B" 1991-1994 KA24DE
Nissan quickly realized that the 240SX needed to be improved to compete with the American sports cars. The KA24E truck motor was the car's most severe market hindrance, so for the 1991 model year, the 240SX got the new KA24DE powerplant. The block remained similar, but the intake manifold, head, and exhaust structure were remarkably different. The KA24DE is a dual cam version of the familiar 2.4 liter iron block, which sported 155 brake horsepower and 156 pound feet of torque at the crankshaft with a slightly heftier 9.2:1 compression ratio. The torque of the old KA24E was there, but this engine breather better, revved higher, and made much more high end power, exactly what was missing from the KA24E. The KA24DE also has a bit of a bad "rap" for being the Altima engine, but this is notably better than the truck motor, most think.
This engine also has advantages and disadvantages. The KA24DE is a full 4 valve per cylinder DOHC motor. The exhaust ports are evenly spaced, making turbo manifolds easy to fabricate and plentiful on the market. It has a frustrating side-feed fuel rail, which of course lacks the uneven spacing of the KA24E fuel rail, making a retrograde impossible. To it's defense, the 370cc fuel injectors from the SR20DET are a "drop-in" replacement. Companies like Tomei and Denso make much larger side feed injectors as well, and all injectors that fit the SR20DET will fit the KA24DE. The intake design on the KA24DE is radically different than that of the KA24E. The KA24DE features intake runners that flow from below the intake ports, as opposed to the SOHC engine's top-down design. The S13B KA24DE's had a sharp cam profile, more so than the S14 or Altima versions. The intake runners were restrictive, but the S14 intake manifold is a direct swap, and larger intake runner fabrication is again a viable option. The KA24DE shares many of the same problems of it's single cam predecessor, namely high-end asthma, bearings that like to spin, and timing chain guides that become loose and cause a ruckus.
Due to the strong aftermarket support, KA24DE's of all years are generally considered a better starting point for building a turbocharged engine than the SOHC KA.
-S14 1995-1998 KA24DE
The S14 240SX came out for the 1995 model year as a substantial revision to the previous S body. This revision again was in response to the Japanese market, where the Silvia got a new body. In America, the same body came through, but the old engine remained. The S14 240SX had different valvetrain characteristics than the S13B, but only got 1 more horsepower out of the mix. The S14 motor cranked out 156 brake horsepower and 160 lb/ft of torque at the crankshaft from the old 2389cc engine, but had even higher compression: 9.5:1. All of the features from the previous longblock remained the same.
The S14 motors are slightly more powerful than the S13B, but are not different enough to be preferable. The later S14 KA24DE's went to an OBD-II ECU, but this was perhaps the most dramatic change that the motor underwent. All in all, the KA24DE was a remarkably static engine.
All three iterations of the KA block have advantages and disadvantages for turbocharing. In common, all three have weak internals, and all three tend to spin bearings. With stock internals, the KA24DE and KA24E can approach 350 brake horsepower, but staying with 300hp is probably the best idea if you don't want to rebuild your engine anytime soon. It is not extremely difficult to get the magic 300 with a KA-T, but it will take time and money. A properly built KA24DET with the full stand alone fuel management can produce over 700 brake horsepower.
We've all heard it before: "I'm getting SR20!" "I'm getting RB20!" Many of us have been through the same tired loop of engine options. There is a plethora of engine swaps available for the 240SX, but there is only one thing that they all have in common: turbo.
All of us want it. The more rich of us buy fancy things like JDM front clips, loaded with RB20DET's, SR20DET's, CA18DET's, etc. Well, some of us just can't afford them. But there is still hope for us.
I love all the KA24's. I think the iron block 2.4 liter stands on it's own, a uniquely American engine in a proud, tall line of fine inline engines produced by Nissan. Being poor isn't the only reason to go KA-T. The ridiculously strong iron blocks and almost 600cc cylinder size create a joyous torquey power band. The enignes are by no means rev-happy from the factory, but with a turbo attached, the combination of low end torque and high end breathing power is absolutely amazing.
The bottom line is, the KA24 is a viable option for turbo, and I feel the best option for those of us who either love the KA or don't have enough for a JDM engine.
ENGINE COMPARISON
-"S13A" 1989-1990 KA24E
The KA24E is the single cam ECCS 2.4 liter 4-cylinder engine that accompanied the S13 chassis on it's debut in the US. The engine produced 140 brake horsepower and 155 lb/ft of torque at the crankshaft from the factory, with a compression ratio of 9.0:1. The engine was driven by a single overhead camshaft, making it the only SOHC 240SX motor. It is also the shortest lived motor on the USDM S chassis, making a 2 year run of production. Nissan's ECCS system was used for fuel delivery. The KA24E never did shake its reputation for being a truck motor, but it's also the first KA and part of the 240SX story. It is, all in all, an iron block KA.
The KA24E is a surprisingly viable candidate for turbocharging. There are advantages and disadvantages to the KA24E. Advantages include the top mount fuel rail, which makes powerful top-feed injectors a "drop-in" replacement. Second hand large top-feed injectors are plentiful in the US and Japan, coming from Diamond Stars and RX-7's, as well as others. Fuel injectors of high capacity are easier to find and more affordable for the KA24E than for the later, side-feed types. The KA24E is also not severely disadvantaged due to it's SOHC nature. The KA24E is a 12 valve motor, with 2 intake valves and 1 exhaust valve per cylinder. Camshaft replacement mods are also half as expensive as dual cam engines. The ECCS system is a top-down intake runner design, unlike the KA24DE. The intake runners are relatively restrictive when compared to later engines, especially the S14 intake manifolds, but can still allow for up to 400 horsepower. Fabricating larger intake runners would be simple. In addition, the compression was slightly lower on the KA24E, making it a slightly more viable candidate for increased boost. The most deleterious drawback to the KA24E is the scarcity of turbo manifolds for the engine. This is due to the fact that the exhaust ports are closely juxtaposed in 2 groups of 2 ports, unlike the even spacing of the KA24DE. Fabricating a turbo manifold is not difficult, however, and if you love the KA24E, this is surely your best bet.
-"S13B" 1991-1994 KA24DE
Nissan quickly realized that the 240SX needed to be improved to compete with the American sports cars. The KA24E truck motor was the car's most severe market hindrance, so for the 1991 model year, the 240SX got the new KA24DE powerplant. The block remained similar, but the intake manifold, head, and exhaust structure were remarkably different. The KA24DE is a dual cam version of the familiar 2.4 liter iron block, which sported 155 brake horsepower and 156 pound feet of torque at the crankshaft with a slightly heftier 9.2:1 compression ratio. The torque of the old KA24E was there, but this engine breather better, revved higher, and made much more high end power, exactly what was missing from the KA24E. The KA24DE also has a bit of a bad "rap" for being the Altima engine, but this is notably better than the truck motor, most think.
This engine also has advantages and disadvantages. The KA24DE is a full 4 valve per cylinder DOHC motor. The exhaust ports are evenly spaced, making turbo manifolds easy to fabricate and plentiful on the market. It has a frustrating side-feed fuel rail, which of course lacks the uneven spacing of the KA24E fuel rail, making a retrograde impossible. To it's defense, the 370cc fuel injectors from the SR20DET are a "drop-in" replacement. Companies like Tomei and Denso make much larger side feed injectors as well, and all injectors that fit the SR20DET will fit the KA24DE. The intake design on the KA24DE is radically different than that of the KA24E. The KA24DE features intake runners that flow from below the intake ports, as opposed to the SOHC engine's top-down design. The S13B KA24DE's had a sharp cam profile, more so than the S14 or Altima versions. The intake runners were restrictive, but the S14 intake manifold is a direct swap, and larger intake runner fabrication is again a viable option. The KA24DE shares many of the same problems of it's single cam predecessor, namely high-end asthma, bearings that like to spin, and timing chain guides that become loose and cause a ruckus.
Due to the strong aftermarket support, KA24DE's of all years are generally considered a better starting point for building a turbocharged engine than the SOHC KA.
-S14 1995-1998 KA24DE
The S14 240SX came out for the 1995 model year as a substantial revision to the previous S body. This revision again was in response to the Japanese market, where the Silvia got a new body. In America, the same body came through, but the old engine remained. The S14 240SX had different valvetrain characteristics than the S13B, but only got 1 more horsepower out of the mix. The S14 motor cranked out 156 brake horsepower and 160 lb/ft of torque at the crankshaft from the old 2389cc engine, but had even higher compression: 9.5:1. All of the features from the previous longblock remained the same.
The S14 motors are slightly more powerful than the S13B, but are not different enough to be preferable. The later S14 KA24DE's went to an OBD-II ECU, but this was perhaps the most dramatic change that the motor underwent. All in all, the KA24DE was a remarkably static engine.
All three iterations of the KA block have advantages and disadvantages for turbocharing. In common, all three have weak internals, and all three tend to spin bearings. With stock internals, the KA24DE and KA24E can approach 350 brake horsepower, but staying with 300hp is probably the best idea if you don't want to rebuild your engine anytime soon. It is not extremely difficult to get the magic 300 with a KA-T, but it will take time and money. A properly built KA24DET with the full stand alone fuel management can produce over 700 brake horsepower.