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Long story short but my car runs pretty hot. I'm sure having a turbo vehicle doesn't help the situation but who would have prioritised creature comfort over more power right?

The average temperature inside the cabin is a good 10 degrees hotter than outside. I'm not just talking about the centre console but the foot-well's hot, the glove box gets warm and even the air that comes through the vents get warmed on a cool day if I just switch on the fan and ask it to take in air from the outside.

Both the air and oil temperature seems fine but from time to time, I do encounter mechanical problems that causes the car to stall and I'll have to let it rest for a good 15 mins on the side of the road - happened to me twice so far on days over 35 degrees and I didn't even touch the air-con.

So what I'm looking for are suggestions on how to 1. make the car run cooler and 2. lower the cabin's temperature.

Here's what I've got/done so far in terms of cooling:
- PWR 55mm radiator already installed and both fans are working;
- Coolant's been flushed periodically and has the right mixture;
- My bonnet has a set of vents on one side directly above the SP intake box (but it's probably doing more harm than good if it's not in the right placement);

Here's what I'm thinking of doing:
- Install a coolant re-route kit;
- Change the location of the inter-cooler and the radiator so that they're not directly in-front of each other;
- Getting a new under tray to enhance airflow;
- Getting another bonnet with more efficient vents (ugly...);
- Sacrificing the fog lights and installing 2 more air intakes scoops;
- Moving the number plate to the side to maximise the intake area at the front;
- Install heat shielding sheets/sprays underneath the carpet (big job to rip all the interior out first...);

Any other ideas?

Heatshield in the tunnel for the exhaust heat in the cabin, and dont remove the fogs.

Vic, I've been thinking the same but more along the lines of reflective material under the chassis to stop the heat getting to the metal to begin with.

I find that my bonnet vent (over the turbo and manifold) is quite adequate provided I don't get stuck in traffic where it will hit 100-110degC. On the highway, my oil temp drops to about 85degC but trundling along at 80kmh the car will happily cruise along with oil temps staying at 90-95degC.

...and that is with an incomplete under tray but with fog lights removed.

I plan on fitting a water spray for the oil cooler and intercooler...when I get to it. I find that if I keep my oil temps (as a proxy for engine temp) below 95degC, I don't have stalling problems

Replace the rubber sealing strip running along the top of the firewall. It stops hot air from the engine bay flooding into the intake box for the cabin ventilation system. They cost about $40 from Mazda ($29 from Amayama plus postage, part number NA0156760). They only last 5-10 years before they flatten out and stop working. A new one usually drops the cabin temp by 10deg.

ACL heat shield screwed to the firewall between the headers and the passenger footwell makes things a bit more comfrtable for the passenger.

Well how about that...I'll bet that will benefit my oil cooler too as it's located behind the firewall!

Anyone up for a group buy?

+1 on manga_blue's comment about the rubber strip. This also works to stop the air flowing back into the engine bay as well as there is a high pressure zone at the base of the windscreen.

It is not about vents it is about air flow, as previously mentioned vents can allow air out and NOT in. Air flows from a high pressure zone to a low pressure zone. If you increase the air pressure in the engine bay (by letting air in) you will have less flowing through the radiator/intercooler. The effectiveness of your cooling is a result of the pressure differential between in front of your radiator/intercooler and the engine bay.

Is the radiator sealed so that no air goes around it?
What undertray do you have?
Have you any instruments to measure the pressure differential?

Apu wrote:...and that is with an incomplete under tray but with fog lights removed.

Both of these would not be helping..

Fix the under tray and either put the fog lights back in, or block the holes so the air doesn't enter the engine bay.

Thanks for the replies so far - they've been very helpful.

I'm planning to get a radiator cover and also replace the under body tray with a new OEM one (that has tighter cut holes). I think the rubber OEM one is much more durable than having an aluminium piece underneath that won't take many hits from scrapping, which would undoubtedly happen.

I'll definitely look into replacing the rubber strip and wrapping the headers as well.

Anything other ideas?

P.S. It does make me wonder whether the current vent is actually doing more harm than good (it was there when I bought the car years ago).

You could put some tape over the existing vent and see if it makes a difference. Alternatively tape some wool tufts around the vent and see what the air is actually doing.



I have managed to fit the OEM undertray as well as my splitter. Not sure how effective this is as not had dríven the car for a few weeks now.

My experiments (and others) can be found here http://mx5cartalk.com/forum/viewtopic.php?p=873782#p873782 ignore the splitter discussion

I will get some more photos on the weekend of the finished product. A new cover was made for the gap at the top of the radiator, heaps easier when you don't have to worry about the OEM bonnet catch system. This ensures as little air as possible escapes through the top.

Next on the agenda is to make a plate to cover where the Mania intake was installed, at the moment it has 'green' race tape covering the hole.

I wrapped the headers on mine once. Stupid idea. One of the worst things I ever did to the car.

manga_blue wrote:I wrapped the headers on mine once. Stupid idea. One of the worst things I ever did to the car.

Why?

An old topic on the subject http://mx5cartalk.com/forum/viewtopic.php?p=642819#p642819

My car required major bonnet venting to keep under bonnet and engine temps under control until the air con radiator was removed. Now has standard bonnet and no sign of moving towards any overheating - at all, even on a hot day at the track. Has coolant reroute, reasonably well sealed 42mm radiator, oversized intercooler, about 150rwkw from 8psi from the ickle IHI turbo which still gets quite hot itself.

It seems the air con radiator was blocking too much airflow through the cooling radiator, perhaps especially as it's a thicker radiator than standard.

Of course, while the engine bay and the engine temps are now ok, there's no air con in the cabin, but I'll put up with some discomfort in exchange for not blowing up the motor.

Heatshield under the transmission tunnel has helped cabin temps.

The EFI relay went through a phase of blowing, thus stalling the motor, and would sometimes "repair " itself when it cooled down. This improved as venting was improved but was only properly solved when the relay and the wiring to it were uprated to properly match the uprated fuel pump. Is your pump uprated?

rascal wrote:

Apu wrote:...and that is with an incomplete under tray but with fog lights removed.

Both of these would not be helping..

Fix the under tray and either put the fog lights back in, or block the holes so the air doesn't enter the engine bay.

Fog lights were removed with the intention of brake ducting...eventually

manga_blue wrote:Replace the rubber sealing strip running along the top of the firewall.

Or just feed another piece of hose through it like i did!

Cost less and should last forever.
This thread has reminded me i need a new undertray!