Some of my friends have been speaking about this--we track a LOT.
All of the 8's that have gauges that i know off. have the coolant temps sensor installed in the heater hose.
Now the question is--is that an accurate temp?
Well monitoring obII and my gauge shows that my gauge is off by 5-10F in comparison to the obII sensor on the thermostat housing.
Now for those pushing temps on the track or were ever---i suppose this should be kept in mind?
Oh my gauge coolant sensor is mounted on the heater hose --right when it comes out of the engine---not on the passenger side firewall.
OD

 

why would u mount the thing at the heater hose? i did mine to the upper hose annd its only 2 to 5 degrees difference.

the obd2 get its readings from the sensor behind the thermostat housinng. which imo it will be a bit hotter cuz its connected to the engine

 

most people mount these things as instructed. Instructions usually point to the heater hose.
when i replace my radiator hose i plan on relocating to a radiator hose.
I wonder what the hot side sees
OD

 

i wonder if this accounts for the discrepancies i've been reading about with regard to my engine temps, which i get from ODB readings...

they are consistently above 200, while some ppl (in my climate region as well) say they very rarely see anything about 200. 5-10 degrees less easily puts me in that territory

 

The racing beat water block attaches to the heater hose.

I've hit the thermostat housing with a laser thermometer and it was the same temp as my gauge reading off the heater hose. The OBD II readouts tend to be about +10 degrees warmer than actual.

I'm inclined to believe my external gauges since normal operating temperature is 180 degrees while OBDII reports 190 degrees. It could easily be different for other RX8's but that's what I've found with my own car.

 

well, I dont use RB's adapter. That's why.

I should have made myself clear.

 

Clear as Cat pie!

 

so this may mean for those that are hitting 220F on their gauges---they may be at 230F!!
Watch it!
Top radiator hose is the return---correct? The bottom on is to the radiator --correct.
I just bought new silicone rad hoses from Pettit and I am thinking about getting pro sports adaptor and mounting my temp gauge in the bottom hose.
OD

 

Top goes to Radiator. Bottom goes into Engine.

This is why the top one is always "hot hot hot" and bottom one not quite as hot.

I think it makes more sense to install it to the Radiator hose because its controlled by the thermostat. stock thermo won't open until like 82' Celsius. there is no point to monitor anything below that temp, for that I have the stock "slow" gauge to do the job.

 

Wouldn't a sensor in the heater hose be meaningful only if the heater was on?

Is it customary to have the heater on when running on the track?

Ken

 

uh---no the heater hose has coolant constantly flowing---are you serious?
OD

 

I never had a problem with my setup ---- you should try mine OD.

 

At steady highway speeds, my external gauge (sensor at the Racing Beat heater hose adapter) and OBDII readings are identical. In stop-n-go traffic, they differ by about 6 degrees F.

 

i have the sensor by using Racing beat adapter, and when i also tried to use COBB, and i compared the numbers, they are pretty identical, and it's just different 5 to 10 degree.
steven

 

10 degrees is alot!
Since our engines run so hot.

 

You know whut I also think happens is the old flash version didn't do fan and the engine prob was cookin up super hot from exhaust heat feeding back into the core when turned off. Without heads like pistonz there is less place for the thermal energy to go.

 

I don't track the car and only read mine(real time) off the ODBII . I do also have the old Mazsport cooling fan mod on there and I really have to run it pretty hard for an extended time to see 200 degrees.

Most times it sits in the 185-195 range, so if that is reading 5-10 degrees higher this way, I'm okay with that.

I think if I saw 210 on my car(with my setup), I would begin to get real nervous and think something is up........just because I know it would be outside my norm. If I saw 215 or above, it would be off with the motor until I discovered why.

 

Hit the point right on the head!
Car has a narrow range of acceptable engine temp--most people at some point will see over 200F. And more than a few will see 220F --but if that 220 is really 230--well then thats another story.
Also good point was made about steady state running being the same temps. It probably does balance out?
The header cooling circuit takes the engine coolant before that coolant comes by the exhaust ports? It exits the rear of the engine on the drivers side. So I guess it would stand to reason that coolant would not be has heated as the coolant going to the radiator?
Also the heater coolant circuit is non thermostatically regulated. That comes in handy when you add a secondary radiator.
Non the less-- prosport has a cool radiator hose adapter for its coolant gauge
and since my prosport oil pressure sensor gave up I need to make an order anyway. I do hate to cut my new silicone rad hose--but WTH.
OD

 

When I installed my ProSport gauges and adapters, I didn't cut the rad hose.
Instead I installed it where the two upper hoses are coupled together:

I don't have a pic with the ProSport coupler attached, but you get the point.
I then cut that angled bracket holding the lower hose so that stayed on that cross brace.
But having both upper hose sections out also allowed me to use RTV around the coupler to ensure no leaks.
Just a suggestion

 

Huh??

OBDII Sensor is not on Thermostat Housing it is Behind Water Pump
it is no where near Thermostat??...that is the OEM one OD

 

I have a Goodbox to display the OBDII reading and my Glowsport gauge is connected to the *lower* radiator hose. This way I can watch the temperature rise through the engine and roughly monitor what the thermostat is doing. It's surprising that the temp rise is only about 20 deg F under normal circumstances. It's also interesting to watch the temp out of the radiator jump 10 deg F or more when the airconditioner is switched on.

 

Yes. I haven't been through the RX-8's plumbing, but on every other car where I have turning the heater off shuts off the coolant flow to the heater core.

If coolant always flows through the heater, how do you turn the heater off?

Am I showing my age? Or the age of the cars I've worked on in the past?

Ken

 

well, I hate it too,

when I first got my 3 piece hose from Billion Japan, it was the first company that I know of to make a silicone hose for Rx-8 that has all 3 piece (all other only made 2 piece, the lower and the upper up to the water jacket)

it was brand new hose and I have to "cut" it to fit the Greddy coolant hose adapter. Ahhh ... and those hose are so strong, I can't cut it with some "typical" scissor. I had to go ask my mom for her big *** scissor that she use to cut fabric. it cuts the hose like tofu (put my "work/professional grade" scissor to shame)

but, trying to fit the thing into the hose was a bitch, it was sooooo tight it took me like an hour something 2 b4 I can "finally" squeeze it in.


I guess you're using RB's coolant hose set? if u don't want to go thru the trouble of cutting/fitting it, Fujita Engineering Japan sells a special piece, it looks exactly like the stock water jacket, except that its pre-drilled, so its pretty much plug and play. just remove ur stock water jacket and install that. thats it.