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Discussion Starter · #1 ·
Super Street Feb 2002 Issue, page 190-191

Question:
What compression is a KA24DE motor running? Will I need to lower the compression to handle about 6-8 psi of boost? I'm considering a TD06 turbo it from GReddy. What kind of black/head work would I have to do and approximately how much would it cost me? I have only about $4000 to spend. I'm thinking if I do the usual head/block work, I might have to get lower-compression pistons so the turbocharged motor won't kill itself. As a result, I'll have to wait about a year to gather enough money for the turbo. About how much horsepower would I lose if I were to run lower-compression pistons on my normally aspirated motor until I get my turbo? Or should I just burn the $4000 on everything else (suspension, brakes, and so on) and wait until I have enough money to throw on the block/head work and turbo (which will probably be in 2-3 years)? BTW, the car is a 1995 240SX with approximately 80,000 miles on it. Thanks for all your help.
-Tam Tran via Internet

Answer:
At 6-8 psi, you will not need to worry about lowering compression. Your biggest concern will be fuel delivery. The KA24DE motor comes with 270cc injectors, which are not sufficient for high horsepower or boost levels for turbos. The TD06 kit from GReddy won't push your motor to its limits; it's one of the smaller-sized TD06 turboes, using a smaller blad and compressor housing. Horsepower figures for the GReddy turbo kit have not been released as of yet. But the company is working on making the KA24DE turbo kit 50-state street-legal. As for head and blockwork, it really depends on how much power you are planning to make. Most turbo kits are designed so they can be "bolted on," meaning no external modifications are needed to handle the additional power of the turbo. XS Engineering (714-992-4133) has a KA24DE turbo kit that used a larger T3/T04E Garrett turbo to produce a higher volume of air at lower boost levels, making up to 210 hp to the wheels at 7 psi. Other companies, such as F-Max and N Sport, use standard-sized T3/T4 turboes that start off adding about 50 hp to the wheels on their Stage 1 kits. Upgrading the fuel injectors (370cc or 550cc), ECU, fuel pump, and airflow meter would be wise investments when purchasing your turbo kit. If you decide to crank up the boost to 12-14 psi, you'll have to worry about the pistons in the KA24DE motor. There is a lot of discrepancy regarding how much power the KA motor can handle. Although Nissan used the same KA24DE motor from 1992 to 1998 in the 240SX, it tried to cut corners with the 1995-and-up motors. The "discount" bottom end internals make the newer KA24DE motors very fragile. We've seen turbo KA motors running 14 psi without any problems, but then there are some that have blown up running 7 psi.
When driving a normally aspirated motor with low-compression pistons, you'll feel the car become sluggish. Horsepower loss will vary depending on how low you choose to drop the new compression ratio. Your $4000 will get you a pretty decent turbo kit, some larger injectors, and ECU tuning. This would be more ideal than spending it all on getting the block and head rebuilt, then driving on a low-compression, naturally aspirated motor for a year. There is another option of swapping out the KA24DE with an SR20DET motor. An older S13 motor is in the same price range and can handle a lot more abuse than the KA24DE. The factory-turbocharged motor puts out 205 hp and can safely withstand abuse of around 300 hp. V-Spec Performance (626-813-9991) can get you the Japanese motor if you choose to go this route.


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There is a lot of discrepancy regarding how much power the KA motor can handle. Although Nissan used the same KA24DE motor from 1992 to 1998 in the 240SX, it tried to cut corners with the 1995-and-up motors. The "discount" bottom end internals make the newer KA24DE motors very fragile. We've seen turbo KA motors running 14 psi without any problems, but then there are some that have blown up running 7 psi.

Is that true for Altima motors as well?
 

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Official Troll
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Well... it's like what Sport Compact Car said about putting an underdrive pulley on...

[excerpt from Project 200SX 1.6]

Underdrive Pulley

Since we saw big results for very little investment with an Unorthodox Racing underdrive pulley in Project SE-R, the installation of it in Project 200SX 1.6 was going to be mandatory. The anodized aluminum pulley is well made with cool details, like a steel sleeve in the front main seal area to maintain a leak-proof seal with the front main seal.

The underdrive pulley works by reducing the speed at which an engine's accessories spin by reducing their drive ratio in relationship to the crank. This reduces friction and frees power. Since the amount of underdrive is mild--on the order of 10 percent--there is no trend to discharge the battery, overheat or lose power steering effectiveness. On Project SE-R, the underdrive pulley freed up 6 hp at the wheels!

There is some controversy about the pulleys, as they are not equipped with the harmonic balancer that the stock pulley has. We feel the risk of removing the balancer on certain engines is not really a risk. Inline, four-cylinder engines for the most part have short, stiff crankshafts. These do not need a balancer as much, because of their high natural frequency. Engines with long, whip-like cranks, like inline six-cylinders, need balancers to prevent failure, but most four cylinders do fine without them.

Nissan four cylinders, with the exception of the vibration-prone KA24, can do fine without a balancer. We have had underdrive pulleys on many SR20 engines, some with more than 1,000 track miles, with no problem whatsoever. Nissan four cylinders are also internally balanced, which reduces the need for a harmonic balancer. Many cheaper engines, on the other hand, need to have a built-in imbalance on the pulley to make up for a lack of an internal counterweight. Like the SR20 engine, the GA16 engine actually felt smoother and revved more freely with the underdrive pulley installed.
 

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Official Troll
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And then Sport Compact Car makes the following statement later on.....

[see attachment]
 

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:-)
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I should be turbocharging my Alty soon (Almost there :)). Me, i wanna run up to 18psi, but im starting with ~12. I plan on:
-8.5:1 compression forged pistons (slight overbore)
-balance the crank
-New Fly wheel
-forged aluminum conn. rods
-some block work
-port the valves, headers, intake
to start with (i think i got most [strengthening wise]) I think this should work :)
 

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founding father
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you may wanna research abit more before getting into this...cuz you'll find that you wouldn't need to port the "header" and you'll scrap the intake
 

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Discussion Starter · #12 ·
RyanDB2 said:








LOL more responses bashing OTB than talking about the engine.



...postwhore

[little kid voice]HE STARTED IT![/little kid voice]
 

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Discussion Starter · #13 ·
Now... back to the topic..


Is it true that newer KA24DE's aren't as strong as older ones?
 

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OTB Race Team said:
to much to read
Sometimes you just ask to get flamed.



I know nothing about what they did to the KA, but I was thinking that if what they say is true then at least the 00-01s probably have the weaker engines. Or the changed when the switched from OBDI to OBDII (which corresponds with the 95+ thing).
 
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