I bought the engine of a Yamaha FZ6. I want to use it to run a competition single seater car we are builiding in the university. The engine didn't bring the radiator with it. I would like to refrigerate the engine with one or two radiators I bought separately.

I would like to know how many new radiators I should use. And in case I have to use both, how I must connect them.

I would also like to know if the pump will have enough power to flow the coolant liquid through the new cooling system.

The dimensions of the original radiator is 320x185x45 (millimeters). The two alternative radiators have the following dimensions 300x190x30 (millimeters).

The first photograph I add it have been taken to one of the new alternative radiator. The second image is a plan of the original radiator (see the red marked part)

New radiator imatge nº 1

Original radiator

  • Welcome to the site. You will need to share the details of the old radiator and new radiator. The ideal parameter to report here would be the NTU for each radiator. If this information isn't available then the radiator dimensions and material will have to be specified at the very least
    – Zaid
    Commented Dec 19, 2015 at 17:40
  • Yes. @Zaid said. Material is very important. Commented Dec 19, 2015 at 20:17
  • Why would you want to do that? It doesn't seem to have any benefit. I know quite a few guys that use that bike for track days. They are doing this in the summer in Phoenix Arizona and running their rpm's to redline over and over all day and they all have stock radiators.
    – Ppoggio
    Commented Dec 25, 2015 at 5:15
  • I am finding out from which material they are made (I guess it must be brass or aluminium). I saw they might have a similar NTU taking into account that the structure of the surface where the air flows through are quite similar
    – user13752
    Commented Dec 29, 2015 at 17:42
  • @user13752 welcome back. I voted to reopen. What bike does the new radiator come off of? Commented Dec 29, 2015 at 18:02

2 Answers 2


A bit of inspiration can be had from either the Yamaha or Kawasaki side by sides. If you have the time and inclination, go to your neighborhood Yamaha or Kawie dealership (they might be the same one), and speak to someone in the service department.

In all reality, your coolant system needs to maintain a certain pressure, a pressure tester can be used. The other consideration is the locations of the 2 radiators:

  1. Are they getting enough airflow to do their job, are they blocking airflow to the engine itself (passive cooling)
  2. Are they trapping heat?

You might very well be able to get away with just a single radiator with appropriate air flow. Since you are, I am guessing, an engineering student, some possible experimental methods can be used.

An example: aluminum tubing with cooling fins to and from the engine. If the engine is mid-mounted and the radiator up front, rubber hoses to the tubing. Beyond all that, the 3 biggest components that absolutely need to function are the radiator cap (regulates system pressure), the water pump, and the thermostat. The thermostat has responsibilities, speed up warm up, and maintain engine temperature in the optimal range. If the engine is to be completely enclosed, you might want to consider an oil cooler.

Most vehicles that use two radiators for the coolant system are slow moving and need more active cooling due to a lack of passive cooling.


Measure the rise from the OEM pump to the OEM radiator as implemented in the motorcycle. Measure the rise or fall from the radiator output to the engine/pump intake.

Implement the new radiators so that the intake at the top is the same height or lower as when on the bike, and the radiator(s) output is above the return port on the engine/pump. That way gravity will assist in cooled coolant return.

If the rise to the replacement(s) is the same or less, and gravity assists the return, the pump should do fine.

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