Gilgamesh

I am making this post here in reference to a thread started in general rotary tech found here:
https://www.rx7club.com/general-rota...7-fd3-1046061/

And because this is a 3rd generation specific problem I wanted to bring it up in the 3rd gen section. ( plus it gets more traffic)

IF the RX8 water pump runs in reverse of the FD water pump, why do we band aid the air pump removal and belt slip problem by adding an idler?

Rx8 water pumps are $35-60 on rock auto and an OEM mazda one is $112 through mazda speed. Cheaper than the Idler kits that i have seen. Not to mention if you ponied up to one of the Mazmart RE-medy water pumps and still had to add an idler on top of it.

What is the down fall of using an Rx8 water pump?

** Ideally ** i would like to think the rx8 water pump would be superior to the FD pump as the rx8 pump was designed and equiped on factory cars that are meant to see 9000 RPM on a regular basis.

j9fd3s

iTrader: (3)

besides fitting the thing, the big problem is that the FD spins the wrong way.

you want the late Rx8 water pump, as it has the good impeller on it, N3R1-15-100 for the pump, N3R1-15-V15 for the gasket (an o ring), and N3R1-15-131 for the pulley.

Gilgamesh

Thanks for the part number info, this water pump is almost half the cost.

When you say the FD spins the wrong way, your talking about how the FD belt routing for the water pump is meant to be ran to the inside of the Pulley. And the RX8 belt is meant to be ran to the outside of the pulley?

If so, that is exactly what i am talking about. Unless i am completely mistaken, running an RX8 water pump the way it was meant to be ran will produce more surface contact with the water pump pulley.

Because right now, an FD with the Air pump elimination kit does not make alot of contact with the water pump pulley. ( i can turn mine by hand with the belt pretty tight.)

But running an RX8 water pump makes you run the belt to the other side of the pulley, which makes more contact "corrects" the issue of the belt slipping on the pulley without buying a $150 aftermarket idler pulley.

j9fd3s

iTrader: (3)

the FD is the only rotary engine ever to have the pump go in the opposite direction to the engine. counter clockwise, if you're standing in front of the car. every other rotary every goes the other way.

so yeah the belt goes on the other side, so not only is is more contact, its contact on the correct side of the belt

jkstill

iTrader: (11)

The impeller will be spinning the wrong direction.

The direction will be correct for the FD with the belt on the other side of the pulley, but incorrect for the impeller, as it was designed to spin in the opposite directly.

Just get a Mazmart water pump and be done with it.

Gilgamesh

This theory is for not having to buy an idler pulley kit to keep the water pump from slipping. But to instead buy a water pump that spins opposite of the fd.

Thus increasing contact with the pulley and reducing slippage, and paying 60 bucks for a new water pump that spins in the opposite direction vs 150 for an idler kit.

Adding a refined own water pump is just an added bonus.


I want achieve this on an fd by using an rx8 water pump.... Will it work?

j9fd3s

iTrader: (3)

it will if you can get the pump to bolt up, the impeller is the same size and the Rx8 w/p pulley fits with the FD main pulley...

Sgtblue

iTrader: (16)

Because under-driven (over-sized) pulleys are the band aid. An idler pulley is actually the proper and more practical fix unless...

Banzai-Racing

iTrader: (11)

I have seen this question pop up a couple times. Completely different bolt pattern and pump orientation. FD gasket on Renesis



RX-8 water pump housing is integrated into the engine front cover, so installing that is not an option.



Install an idler and be done with it.

Gilgamesh

Thanks!

Hopefully the next person who googles the question will find this thread.

silverTRD

iTrader: (37)

Possible to put the rx8 impeller on the fd pump?

That'd be awesome remedy made a fd pump with the impeller going backwards. . That would solve 2 problems, 1. The cavitation issue and 2. the belt slipping issue.

7krayziboi

iTrader: (15)

This is the discovery of the day for me...gotta love this club