SR20DET vs. KA24DE
I have noticed that the Internet is littered with debates on whether or not a SR20DET is superior to a turbocharged KA24DE motor. I am, however, confused on why this debate even exists. Therefore, I am posting this thread to find out what I must be missing.
I feel that there is absolutely no contest; the SR20DET motor is a far superior racing motor. It seems like this debate is comparing apples to oranges.
Here is my rationale.
Horsepower: The SR creates far more horsepower then a turbocharged KA. Although the KA has a 25% increase in displacement, the displacement is found in the stroke. The larger stroke limits the KA’s ability to rev as high as the SR. Since HP = Torque(RPM)/5252 (torque @ a given RPM is multiplied by that RPM, then the answer is divided by 5252) higher revs will create higher HP readings. (You will notice on graphs that all engines have the same horsepower and torque at 5252 RPM’s).
Torque: The KA obviously creates far more low-end torque (created by the bigger stroke). Since torque is what moves you, you would think the KA would be the better choice. The SR, however, can easily overcome this loss in low-end torque. Since the KA redlines at approximately 6,000 RPM’s and the SR at 7,500 RPM’s the SR can create more low-end torque. How, you ask? Well there are two kinds of torque, engine torque and gear torque. The KA produces more engine torque and since the SR revs higher it can use a lower gear ratio too build more gear torque. The gear torque quickly increases the total torque output in a vehicle. Therefore, with the 25% increase in RPM’s, the SR can produce comparable low-end torque.
Weight: Obviously, this is a huge concern for any racer. Lighter weight means quicker acceleration, deceleration, and better handling. The SR is an all aluminum construction, while the KA has an iron block.
Technology: The KA is a truck engine. It uses a distributor and is fuel injected. That is about the extent of its technology. The SR has direct ignition, and continuously variable valve timing (late model SR’s). This technology will give the SR a flatter torque curve then the KA.
I know the saying goes, “There is no replacement for cubic displacement.” but, I would take the SR over the KA any day of the week. Besides, what would you rather have? A big block NASCAR engine or a F1 engine?
With that said, I await to hear what I missed about the performance benefits of a KA.