How do you tell if your water pump is cavitating?
 

I took my car (88 SE) out autocrossing yesterday - great fun, I have much to learn (a stock Cavalier beat me).

One of the things I figured out was that 1st gear, at least on this particular course, is a MUCH better option than 2nd. Coming out of corners at 2k RPM doesn't really do much for times.

Anyway, on the last run, I made the whole run in 1st, with the buzzer going off most of the time. It was much faster, but I finished with the stock temperature gauge at almost half (57 seconds of run). That's high enough to make me uncomfortable - it normally runs around 1/5 to 1/4. I've heard that cavitation sets in around 6000 RPM or so, and I was above that for at least half the time.

Is there any good way to tell if the pump is spinning too fast? Right now I only have the stock gauge set - I'm planning to add aftermarket water temperature and oil temperature gauges, but can't afford a good set right now.

Do underdrive pulleys cause problems for daily driving? I'd like to keep my AC & PS, so I'd need one that supported those belts as well.

-=Russ=-

Ultimately, your water temp is what matters - get a gauge. Autocross runs are so short, that even if you are cavitating for that 1 minute, you aren't going to damage the engine during that time. The Miata thermoswitch or fan mod might be a good idea to make sure the car will cool down afterward.

I am putting a Pettit underdrive pulley on my car (keeping the stock accessories: AC, PS, air pump, etc.), so I can let you know in a couple of weeks if it's a problem around town.

Neat. I'm getting a gauge... when I can afford one. :-/ It's an S4, so the stock gauge is actually halfway usable. Plus I still have the stock clutch fan (for now), so it cools down quickly.

-=Russ=-

A lesson learned the hard way
 

I have a 13B Bridgeport, that turn about 10,000rpm. After testing and running about 260 - 280 degrees water temp I finally called Mazdaspeed. They informed me that the stock pump and pulley cavitate above 6500RPM! With there new pulley system the problem was solved. HOWEVER, the Mazdaspeed pulley's do not work on the street where you are running about 2-3000rpm, the water pump turns to slowly. S o be careful what you do!

*nods* That's what I'm worried about - low pump speed on the street. That wouldn't be any good, to have it cool while racing but not while driving around town (it's still my daily driver).

I suppose the best solution would be an electric water pump, or at least an electrically driven water pump. A bit of a pain, though.

-=Russ=-

You really need an aftermarket water temp gauge to monitor the water temps.
The stock water temp gauge is too inaccurate.


-Ted

I run the RB under drive pulley set on my 12A street port , street driven car, and I do not have any cooling problems at low rpms.

I do notice that when the headlights, taillights, wipers, and heater blower motor are all running, then I am a little lower in voltage at idle (the alt. is spinning a little slower too.)

I recommend those pulleys for all performance Mazda operations.

Running an engine without a thermostat - does that have any effect on possible cavitation (more water flow - less problems???)???

I have the very small race pully running from the shaft, but a standard water pump pully, and the motor runs a good temp even at extended periods around 10,000rpm (but does run to cold on the road - have a blocking card to stop air flow to a large part of the radiator).

I run the Pettit underdrive crank pulley [only] and it works fine for daily and street driving with all accessories.

we tested it vs the haltech and the greddy, the 84-88 water temp guage is very accurate.

c on the 84-85 guage is about 65c, half way is 91c, when the mechanical fan turns on.

h on both is 235F

re10 - what year motor/ water pump housing are you using?