Zxr 750 radiator options.UPDATED - PLEASE HELP ME.. AGAIN

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Re: Zxr 750 radiator options.UPDATED - PLEASE HELP ME.. AGAI

Postby robz » Fri Dec 23, 2016 5:34 am

Really.... never knew that.
Out of pure interest and ignorance how come? (Like to learn) :lol:
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Re: Zxr 750 radiator options.UPDATED - PLEASE HELP ME.. AGAI

Postby BrettZZR » Fri Dec 23, 2016 12:52 pm

A thermostat is a valve that closes (just about) off the flow of coolant until the engine gets up to temp, and then opens to try keep the temp steady. In cool weather going down a long hill it might close again (almost) completely as the radiator cools the engine too much...

BUT... even when fully open, the thermostat is a bit of a constriction (bottleneck) and limits total flow through the system, so on the track where the heat load is at a maximum, and (specially on tight tracks) airflow through the radiator is up-and-down, then getting more coolant flow through the system is a good thing.

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Re: Zxr 750 radiator options.UPDATED - PLEASE HELP ME.. AGAI

Postby greenman43 » Fri Dec 23, 2016 10:06 pm

That said, some engines need to have the coolant stay a bit longer in the rad - if it passes through too quickly, it doesn't shed enough heat. I have read of race cars using what's called an orifice plate: basically, a replacement for the thermostat itself, being a plate with a certain-sized hole in it.

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Re: Zxr 750 radiator options.UPDATED - PLEASE HELP ME.. AGAI

Postby robz » Thu Dec 29, 2016 7:52 am

yup... understood the workings of the thermostat but never really put all that together..
great info to know.. cheers...well my 2nd hand rad is here and just drying the paint... will try and fit it this week
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Re: Zxr 750 radiator options.UPDATED - PLEASE HELP ME.. AGAI

Postby BrettZZR » Thu Dec 29, 2016 11:46 am

greenman43 wrote:That said, some engines need to have the coolant stay a bit longer in the rad - if it passes through too quickly, it doesn't shed enough heat ...

Mmm, I've heard comments like this before, and I'm no expert, but it does not sound feasible to me. Passing through the rad slower to shed more heat would have the equal and opposite reaction of passing through the engine more slowly and gaining more?!

I suspect that the orifice plate is more to provide some back pressure to the pump to prevent cavitation at high revs. That's the exact reason that I fitted a water pump from an Integra Type-R engine to my track car. It is driven by the cam belt and has 21 'teeth' instead of the normal 19 and requires a longer cam belt to suit.

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