Tempature Gauge - observations (long post)

Juffa · Postby **Juffa** » Fri Dec 22, 2006 9:12 am

I have not had the chance to drive the now turbo'd Tweety in stop-start traffic on a hot day, until yesterday. I was curious to see if the huge intercooler that I have sitting in front of the PWR radiator and Air-cond would block air flow and cause over heating.

The hand held controller for my FM Link ECU has a display for the coolant temp, as well as the output from a temperature sensor which is mounted between the intercooler and the throttle body. Normally I see the coolant temperature between 88-92c once Tweety is warmed up, and the intake air temp between 25-40c.

I left work yesterday at around 4.30pm. The outside air temp was around 36c. For most of the drive home along edge of the bay from Port Melb to Chelsea the traffic was fairly heavy. I had the roof up, and the air cond on, thinking this would be a good test of the cooling system. I kept an eye on the dash temp gauge, which as usual did not move from its normal position of 'left of centre'.

At one point I checked the ECU readout and was surprised to see that the coolant temp was running at 100c and the intake air temp was around 50c. The dash temp gauge had not moved. Out of interest I turned the air cond off and noted that the coolant temp dropped down to 92c over a 5 minute period. I then turned the air cond back on and the temp climbed back up to 100c. The air intake temperature did not move much either way during the period that the air cond was off.

When I got home after the 1 hour drive I lifted the bonnet and found that the coolant level in the over flow tank was up slightly, no big deal. I'm running Nulon green coolant mix with demineralised water. Tweety did not smell hot at all, and there was no tell tale smell or visual sign of coolant leakage.

My observations are;
Air cond put extra strain on the engine, causing the coolant temp rise, probably not helped by the huge intercooler.
Dash temp gauge has a dead spot. It shows normal temp from around 80c to 100c (maybe higher).

J

JBT · Postby **JBT** » Fri Dec 22, 2006 9:23 am

Yep, the dash gauge has a dead area - sort of \"idiot light\" type thing so that those with no mechanical understanding (and Americans) don't go running to their dealer/mechanic for no reason.

Same reasoning for the 1995 onwards NA getting an \"idiot light\" oil pressure gauge.

kula · Postby **kula** » Fri Dec 22, 2006 9:25 am

yup.

make sure both fans are coming on when the a/c is on.

i have a defi temp gauge, and normal on the factory gauge can be anywhere from 67-100...
anything above about 98 or so is starting to get warm.

Garry · Postby **Garry** » Fri Dec 22, 2006 9:38 am

anything above about 98 or so is starting to get warm.

Is it? The cooling fan on my bike doesn't even come on until 103deg. Thats considered to be within the normal operating temperature by Yamaha. Once the fan comes on though it drops the temperature pretty quickly back to 98 where the fan turns off. \"Normal\" temperature while moving is around 90 degrees.

Juffa · Postby **Juffa** » Fri Dec 22, 2006 9:57 am

kula wrote:make sure both fans are coming on when the a/c is on.

I should have mentioned in my first post that I have the fans wired so that the Air Cond fan is running when ever the main fan is. Did it when I first installed the turbo.

J

glen73 · Postby **glen73** » Fri Dec 22, 2006 1:05 pm

when i first bought my car it had a boost gauge and a defi water gauge. i found the mx5 temp gauge to be very much inaccurate compared to the defi.
don't go off the mx5 gauge.

what sort of results did you get juffa with the turbo? are you happy with it?

cheers
glen

AJ · Postby AJ » Fri Dec 22, 2006 8:14 pm

100 deg is nothin' juffa.........as garry said, a lot of fans don't cut in till 103-105

kula · Postby **kula** » Fri Dec 22, 2006 8:16 pm

i guess it depends where your temp sensor is..
my fans come in at about 90-92.

kula · Postby **kula** » Sat Dec 23, 2006 8:41 pm

yup. thats about what ive seen too

Uncle Arthur · Postby **Uncle Arthur** » Sun Dec 24, 2006 1:04 am

I decided I wanted to know what's going on INSIDE the motor a bit more, hence I've installed an oil temp gauge.

Rarely gets much over 100C..... even less since the replacement radiator went in last weekend.

kula · Postby **kula** » Sun Dec 24, 2006 12:48 pm

yup. I too have an OTG, yet to be hooked up tho.

sabretooth · Postby **sabretooth** » Wed Dec 27, 2006 9:09 pm

Garry wrote:Is it? The cooling fan on my bike doesn't even come on until 103deg. Thats considered to be within the normal operating temperature by Yamaha. Once the fan comes on though it drops the temperature pretty quickly back to 98 where the fan turns off. "Normal" temperature while moving is around 90 degrees.

I'm inclined to agree with Juffa here. Anything much above 100 gets my gauge needle moving past 12 - and that's not a temp I'm comfortable with. My setup is set so that the fan cuts in at 92 and out at 84. I'm pretty sure that the stock ECU is set up similarly.

The gauge does have a dead spot - there is a thread on miata.net about removing said dead spot if you are so inclined. I think the current dead spot that Mazda give us from the factory could do with some undeadening, but not too much or else paranoia will set in every time it twitches.

I think you're getting a higher coolant temperature not just due to the extra load put on the engine by the AC, but because the condensor for the AC sits in front of the radiator. If that's shedding heat and the air is flowing through from the front to the back, then it's going to mean warmer air to the radiator, and less heat exchanged by it - which means a higher coolant temperature.

Juffa, which radiator do you have? I have the PWR 38 - I was advised by PWR themselves that the thicker one is way overkill for a road car and that you'd really want some good ducting set up to drive air through it.

Juffa · Postby **Juffa** » Wed Dec 27, 2006 9:38 pm

sabretooth wrote: I think you're getting a higher coolant temperature not just due to the extra load put on the engine by the AC, but because the condensor for the AC sits in front of the radiator. If that's shedding heat and the air is flowing through from the front to the back, then it's going to mean warmer air to the radiator, and less heat exchanged by it - which means a higher coolant temperature.

Juffa, which radiator do you have? I have the PWR 38 - I was advised by PWR themselves that the thicker one is way overkill for a road car and that you'd really want some good ducting set up to drive air through it.

Hi Sabre, I was thinking the same thing....plus I have a huge intercooler sitting in front of both the condensor and the radiator. I have the PWR 38mm radiator.

J