Part 7: The Quest for Efficiency



If I were to ask you what your vices are, what would you say? Now what about your automotive vices? What preoccupies your mind when you are working on a project? What grabs a hold of you and makes you a slave to the build? I myself have a few and one such vice is efficiency. More specifically, I’m talking efficiency of design, efficiency of cost and efficiency of power. This latest installment of Project CA18DET 240sx highlights just that and will show the myriad of changes the CA18DET has undergone in this quest for efficiency.

Efficiency 101: Reducing the Coolant System’s Complexity

There are several systems on the CA18DET that won’t necessarily increase the car’s efficiency in a power producing sense but will greatly simplify the cars supporting systems and therefore, improve the car’s reliability. The coolant system fits this criteria perfectly. In fact, excluding the two radiator hoses, the stock CA18DET runs a total of 10 individual water hoses that snake around the intake manifold. Not only are these lines hard to reach and leak prone, most of them are not even necessary. In reality, one custom hose that connects the small outlet near the thermostat to the block inlet under the intake manifold is all that is needed to properly circulated the coolant through the block. Now this particular mod is not for everyone. To route the coolant with only one line, the heater core must be removed as well as the water cooling for the turbo and throttle body. However, this mod is very simple and is easily modified with simple t’s if additional coolant routing is necessary. A step by step guide of the first iteration can be found here (CA18DET Water Mod – Simplifying Water Circulation)) and the second version is located here (CA18DET Water Mod Number 2 (From 10 Lines to 1))

Another image showing the possible path of the new coolant line on the ca18det.
This image is from the (CA18DET Water Mod Number 2 (From 10 Lines to 1)) walkthrough that shows the roughed in coolant line.

Efficiency 201: Use What You Got

The intake manifold on the CA18DET works very well for all but the most power hungry individuals. But what if you could improve this system’s bottleneck with a simple parts swap from the old KA24DE that now finds its home on the garage floor. Improving throttle response is what the KA throttle body swap is used for on the CA manifold. Swapping the CA18DET’s factory throttle body out for the larger, freer flowing, direct bolt on throttle body from the KA is a pretty simple affair that entails boring the throttle opening in the manifold, swapping over the tps and then modifying the CA’s throttle pulley to work with the KA throttle body. Check the tech section for the upcoming tutorial (Swapping the KA24DE Throttle Body onto the CA18DET Intake Manifold (The Quick and Dirty Way))

The KA24DE throttle body and the CA18DET throttle body side by side.
Note the size difference between the KA24DE throttle body (top) and the CA18DET throttle body (bottom). The KA24DE throttle body will improve on/off throttle response once installed onto the CA18DET’s intake manifold.

Efficiency 301: Go With the Flow

Now things are getting juicy. Project CA18DET is slated to run 1 bar(14.7 psi) of boost in its final form. Unfortunately, this isn’t the best idea with the factory T25 turbine. The stock turbo begins to run out of steam toward redline at the stock boost setting. Double the boost and the problem begins to get worse. Not only is the small T25 out of its efficiency range at this point but worse, it is generating a lot more heat and therefore adding more thermal stress to the motor. For the power levels in mind, this leaves only one option. Even by increasing the T25’s exhaust housing ratio (which will allow the turbo to flow a little better at higher rpm’s) the T25 will always be at the ragged edge at this boost level. So in comes the T3 Super 60 Garrett Turbo. The T3 Super 60 is an excellent match for the CA18DET. It can safely support boost levels in excess 15psi, offers excellent spool characteristics and is literally the work horse of the do it yourself turbo crowd. The particular turbo I chose was the 46 trim model without the liquid cooled center section. To complement the new T3 exhaust housing, I also added an equal length, top-mount, stainless steel exhaust manifold to the mix with a Tial external wastegate. With this combination, I dare say the T3 provides better spool and boost response than the smaller T25 and pulls all the way to redline without hesitation.

Side by side comparions of the T25 from the sr20det vs the T3 Super 60 by Garrett
Notice the T3 Super 60 (bottom) only looks slightly larger than the stock T25. Looks are deceiving however as this turbo is capable of much larger numbers than the T25.

Image showing the larger t3 super 60 turbo installed with the new top mount manifold on the ca18det.

The T3 Super 60 is mounted to the new top mount stainless steel exhaust manifold.

Efficiency 401: Take a Deep Breath

Following this logic:

  1. turbos compress air
  2. the side effect of compressing air is heat
  3. excess heat leads to pre-ignition
  4. pre-ignition robs power and causes trauma to the motor

It only seems logical to supply the turbo with the coolest air possible in an attempt to reduce the temperature of the compressed air exiting the turbine. With that in mind, the fabrication of a custom cold air intake is needed. Why feed the turbo 110+ degree air from the engine bay when it could be getting 70 degree ambient air. Ultimately, cooler air into the turbo results in cooler air into the motor. Fabrication of the cold air intake could not have been simpler with the new top mount turbo placement. Using 2 1/2″ aluminized steel tubing from Autozone, a 110v mig welder and a little elbow greese, I welded angled pieces of the tubing together into a very gradual bend. The finished result put the air filter just outside the engine bay through the hole that was previously used for the liquid intercooler water tank. Finally, A/C duct sheetmetal was cut and riveted around the hole to completely isolate the air intake from the engine bay. Conveniently, the 240sx has a vent just below the front, driver’s side turn signal that will constantly feed the new cold air intake with fresh, ambient air.The new cold air intake (CAI) passes through the sheet metal of the 240sx and puts the filter just behind the bumper.
The new cold air intake (CAI) passes through the sheet metal of the 240sx and puts the filter just behind the bumper.

The air filter is now located outside of the engine bay yet remains protected from the elements.
The air filter is now located outside of the engine bay yet remains protected from the elements.

That’s all for now. I will be adding the associated tutorials throughout the week. Be sure to check back for the next update to project CA18DET. I’ve got something really special planned. (Hint: What intercooler?)

By 240am

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