The only downside with the throttle body line is if you use a 1-wire temp sender that grounds through whatever it screws into. You can add a ground wire to the brass T and ground it, though.

This is a good option if you have the water pump housing off already and want to do it. The thermostat housing is still dumb any which way you look at it.

Also, I'm just not keen on 1-wire temp sensors, that's just a lazy design.

Dale

 

Clean setup on the waterpump housing, but is there any noticeable reading difference between the 2 location?

 

+1...on all points. And nice job Speedjunkie.
No difference between readings from the waterpump housing and the throttle-body coolant line. That line goes into the back of the waterpump housing. (see "from TB out to WP" below)

 

From this diagram, it looks like the coolant flows in the upper drivers side of the engine, and out the lower passenger side. It appears that the coolant to the throttle body coolant line escapes the engine before being completely heated by the passenger side of the engine.

If I am seeing this correctly, this would explain why my TB coolant line sensor is always several degrees cooler then my PFC reading.

 

Yeah it's quite a bit more work to install it this way, but I'm doing other major installation things anyway so I figured why not. Thanks!

That's where I had it installed this whole time, but I had to ground this new sensor and I'm going to use that coolant routing for the new wastegates and figured this was just easier.

Yeah it's a pain to have to ground this thing, but I like that these gauges take up less space being dual gauges. When I first installed these, I didn't realize I had to ground it and I was having all kinds of problems with the gauge reading correctly. I grounded it with a wire like you mentioned and it still didn't fix anything. Turned out to be a bad sensor.

Thanks! I'll have to see once I run it, although with the variables of ambient temp and all that, I may never really know, especially if it's just a couple degrees difference. It's been warmer lately than it was when I put the car down a week ago.

Thanks!

That's how I'm seeing it too. I figured if flows as the diagram shows (and it should), I should see hotter temps at the back of the thermostat since it flows through the exhaust side after the TB line. We'll see I guess.

 

It flows to the throttle-body coolant line right after passing BOTH combustion chambers. It just doesn't pass through the exhaust side of the housings.
I bypassed the T-body some years back but still use the line for my gauge sensor. Your experience is opposite of mine. The gauge is consistently in complete agreement with the PFC. If anything the gauge (DEFI 'D' Series) reacts a hair quicker.

 

Jim,

Glad your temps correspond. Mine don't. The exhaust is the hottest portion of a rotary engine. It seems to me that the coolant would be heated even more on the exhaust side.

Adam

 

Since we are replacing our factory W/T gauge with something more accurate can I just use the location of the factory sending unit and screw in the new sending unit there?

Joe

 

Depends on the thread pitch. I think the stock one is M10x1.0 and sensors tend to be 1/8NPT. But you can use this...

https://www.pegasusautoracing.com/pr...asp?RecID=1832

 

Good observation the TB water is taped out of the block before real heating from the exhaust side of block. Makes sense, mazda wanted to pre-heat the TB for anti-icing not super heat the intake air.

 

Are we sure the exhaust side is hotter than the combustion side? I ask because I've always seen the modifications for cooling done on the plug side of the housings, not on the exhaust side. And after the combustion event, which side of the housing (referring to the diagram) has the most prolonged contact with the hot exhaust gases?
Intuitively I think it should be the exhaust side, and certainly it's last on the coolant flow, but....

 

Another factor is that the turbos are bolted to the exhaust side, which would tent to heat that side of the engine even more.

 

I have been reading this thread and no one mentions installing the new temp sender in the old temp sender location. Since we are not using the old gauge why isn't this the easy way to accomplish hooking up the new gauge?

Joe

 

I'm still using my stock gauge as well. I don't look at it as much as the aftermarket one, but in case that one fails I can at least see something with the stock one, even though it's not great. That's why I ended up choosing not to put it there. I had thought about it though.

 

i just bought the prosport rad hose tap for $25. Nice write up im too chicken to attempt this.