Aiming to own one of the "coolest" MX-5 in OZ...

Steampunk · Postby **Steampunk** » Mon Jul 28, 2008 9:43 am

On the weekend I installed a radiator from an automatic NA, as well as a BEGi radiator coolant bypass kit.
For those who are not aware, the radiator from an automatic NA, as well as NB, is approximately 75% thicker than a manual radiator.

Long story short, this bigger radiator, combined with the BEGi kit reduced my coolant temperatures by 37deg Fahrenheit, or about 20deg Celcius in our language.
In other words;
- Standard coolant temp = approx 200deg F / 93deg C
- Bigger rad + BEGi bypass = approx 165degF / 74deg C

I must say that is a pleasant surprise as I was expecting no more than a 10deg Celcius drop.

The intake manifold temperature has also dropped, on average, by 5-10 deg Celcius across

Next comes an oil cooler

Thanks to Muzza2, GP14 and AZNTien for your assistance.

SuperMazdaKart · Postby **SuperMazdaKart** » Mon Jul 28, 2008 11:03 am

got demineralised water with Water Wetter in there too?

Steampunk · Postby **Steampunk** » Mon Jul 28, 2008 11:08 am

nope and nope.
I have Tectaloy 100Plus in there.
I did some research on Water Wetter and I didn't like the reviews it had. I found more cons than pros.
Apparently it does work, but it coats the internals with gunk that is difficult to remove.

Juffa · Postby **Juffa** » Mon Jul 28, 2008 1:25 pm

Andrew,

Are you saying that for normal day to day driving you are seeing coolant temp at 74c? Are you running a thermostat? How/where are you measuring the temp?

To be honest I'm not sure this is a good thing. The engine is designed to operate most efficently within a specific temp range and 93c is pretty much the norm.

ps have a look at this high level article. There are heaps more on this subject.

http://autospeed.com/cms/A_108378/article.html

Just my 2 cents worth.

J

Steampunk · Postby **Steampunk** » Mon Jul 28, 2008 1:57 pm

Hey Jeff
Yes, day to day driving (but keep in mind I've only dríven it a few times since Saturday when I did the installation), I am seeing 74degC instead of 93degC.

The reading is from the datalogger on my MegaSquirt, and I can only assume that it gets its reading from the thermostat, unless there is another coolant temperature sensor :roll:

I realise that engines have optimum operating temperatures, but I reckon it's still on the safe side as the temperature reading at the inlet manifold has only gone down, for the most part, 5 deg with a maximum drop of 10 deg.

The coolant bypass re-routes the outlet hose from the cabin's heater-core, and sends it straight into the top of the radiator via a T-piece into the top radiator hose. The temp drop at the thermostat confirms that the front of the engine gets hotter because the heated-up coolant (after it passes through the engine) is being fed back into the front of the engine after it passes through the heater core.

GP · Postby GP » Mon Jul 28, 2008 4:01 pm

It doesn't matter what you do the engine will always run at the thermostat temp. If your water temp is at 74 then you will need a new thermostat

Steampunk · Postby **Steampunk** » Mon Jul 28, 2008 4:33 pm

Thermostat is working fine.
Almost every time I go for a drive, I datalog it.

nfs13b · Postby **nfs13b** » Mon Jul 28, 2008 7:18 pm

i have a civic radiator and i get about 160deg F after a hard run

Boags · Postby **Boags** » Mon Jul 28, 2008 7:19 pm

Your thermostat should be set to higher than 74 shouldn't it? If it is an 80 deg thermostat and you are data logging temp at 74 then it isn't working. It should stay closed until the car is up to temp and then open; regulating the temp at "at least" 80 deg.

Please let me know if my understanding of thermostats is flawed (it's not something I have dealt with a lot).

Boags

Steampunk · Postby **Steampunk** » Tue Jul 29, 2008 9:32 am

It just means that the coolant has not gotten hot enough for the thermostat to open fully.
Just to heat up the subject more, this morning's datalog, easy driving from home to work for 25mins in light traffic, the coolant temp peaked at 145deg F. Outside temperature is around, what .... 12 deg Celcius this morning?

Boags · Postby **Boags** » Tue Jul 29, 2008 10:25 am

1red5 wrote:It just means that the coolant has not gotten hot enough for the thermostat to open fully.

I don't really understand that. I'm happy to be wrong, but none the less I think this thread is a good place to understand it better.

The thermostat is heated by the coolant in the engine (the coolant in the engine is circulated by the waterpump; the thermostat is closed, which stops the coolant going through the rad). The coolant in the engine will heat very quickly and continue to heat until the thermostat opens at a certain temp. When the thermostat opens, the waterpump then pumps the coolant through the radiator rather than just around the engine. Once the coolant in the rad (still at air temp) reaches the thermostat it cools the thermostat, closing it again (meaning the temp @ the coolant in the engine can't drop below the set temp of the thermostat once up to temp).

That is how I understand it. From that; 2 questions. 1. Where does the megasquirt take coolant temp readings from? 2. At what temp is your thermostat supposed to open?

Steampunk · Postby **Steampunk** » Tue Jul 29, 2008 10:52 am

1) I assume the MegaSquirt reads the temp from the thermostat. Unless there is another temp sensor.
2) I don't know.

Thermostats will allow some coolant to flow through at all times, and it's only at a certain temperature, let's say 90deg Celcius, that it will open up 100% and allow as much coolant to flow through as possible.
Thermostats open gradually, according to temperature, in other words, they are not completely closed at, for example 50deg Celcius, then completely open at 90 deg Celcius.

Juffa · Postby **Juffa** » Tue Jul 29, 2008 11:53 am

Not trying to gang up on you Andrew, but I'm with Boags on this one

Below is a helpful link from miata.net which amongest other things shows the flow of coolant through the block. It also shows the two temp sensors at the back of the block. One is used for the temp gauge on the dash and the other is for the ECU.

http://www.miata.net/garage/CoolingSystemProblems.html

My thinking is if a car is overheating you would want to reduce the coolant temps back to the normal range, not reduce it below the normal range. From what I understand running the engine at below normal operating temps is not a good thing, including oil not at optimum operating temp, running too rich....and so on.

J