Results 1 to 10 of 10

Thread: Coolant/Thermostat/Under Cover Valence

  1. #1
    Idling - Listen to it purr...
    Drives
    2000 LS
    Location
    St. Louis, MO
    Join Date
    Mar 2019
    Posts
    5
    Thanks Given
    0
    Thanked 0 Times in 0 Posts

    Coolant/Thermostat/Under Cover Valence

    I recently bought a very nice 2000 NB with 35,000 original miles. One owner, with every receipt from new. But it's 22 years old so I decided to bring all maintenance items up to date. I have fitted an Ultragauge, which plugs into the OBDII connector and gives all sorts of information. I was disappointed to find that the car normally runs about 205 degrees--and even tops 210 (I have a warning set) before the thermostat opens for the first time. I decided that this wouldn't do. I think Mazda selected a 195 thermostat--back in the day--mostly for emissions considerations. But it's my personal opinion that these very hot running temps are chiefly responsible for all the tan colored radiators that need replacement. Anyway, I changed all 7 coolant hoses, both serpentine belts, and installed a 180 degree thermostat from Moss Miata (part number 999-026, for $7.99). I am now running 185 degree temps, instead of 205, and I am very happy with this. By the way, the stock temperature gauge is useless. The needle shows the same for any temps from 180 to 220.

    On another matter, I took off the so-called 'under cover' plastic valence which covers most of the under engine compartment. I have no idea why this is fitted. It can get caught on curbs, etc. and rip off the front fender support. This has happened to friends. It did hundreds of dollars damage. I had run it on my 1992 because I couldn't run the Ultragauge to see temps (it didn't have OBDII). But now I can tell you that it makes absolutely no difference to the engine temps. If you do break down somewhere, and have to change the bottom radiator hose, you have to take this off. Good luck doing this by the side of the road somewhere. I'm not running it anymore.

  2. #2
    Ninja Messiah kung fu jesus's Avatar
    Drives
    1999 White
    Location
    Atlanta, GA
    Join Date
    Dec 2011
    Posts
    15,836
    Thanks Given
    2,787
    Thanked 7,172 Times in 3,420 Posts

    Coolant/Thermostat/Under Cover Valence

    Congrats on the purchase.

    The undertray is, in fact, important to the cooling system. It also helps keep water out of the engine bay electronics (the electronics in the NA and NB Miatas are not particularly good at being weather resistant), and aids to prevent lift at higher speeds. On the NB, bumper/fender struts are not utilized nor connected to it.

    The plastic radiators turn brown from heat cycling. Every car with a plastic radiator and cooling components ages similarly.

  3. The Following User Says Thank You to kung fu jesus For This Useful Post:

    HarryB (08-11-2022)

  4. #3
    Idling - Listen to it purr...
    Drives
    2000 LS
    Location
    St. Louis, MO
    Join Date
    Mar 2019
    Posts
    5
    Thanks Given
    0
    Thanked 0 Times in 0 Posts
    Why do you say it's important to cooling if I'm not seeing any change in temps with it fitted or not?

  5. #4
    Ninja Messiah kung fu jesus's Avatar
    Drives
    1999 White
    Location
    Atlanta, GA
    Join Date
    Dec 2011
    Posts
    15,836
    Thanks Given
    2,787
    Thanked 7,172 Times in 3,420 Posts
    You are monitoring coolant temps not necessarily cooling efficiency. I have witnessed testing contrary to your info on race cars and my own street cars in multiple climates.

  6. The Following User Says Thank You to kung fu jesus For This Useful Post:

    HarryB (08-11-2022)

  7. #5
    5,000 rpm - there be torque here! Greasemonkey2000's Avatar
    Drives
    2001 NB2 aka Misfire
    Location
    Temple, Tx is where Chad resides.
    Join Date
    Nov 2013
    Posts
    3,922
    Thanks Given
    4,870
    Thanked 2,393 Times in 1,216 Posts
    You put in the wrong thermostat and now you're running rich for no good reason, losing power and prematurely wearing your catalytic converter. The 195F is what the factory ecu needs to run PROPERLY otherwise it takes longer to get to temperature which means it's adding fuel and will retard timing under load.

    The undertray does aid in cooling which is WELL ESTABLISHED.
    '01 NB2 aka MisF1re: http://mazdaroadster.net/showthread....218#post207218
    '97 M aka Warbird, gone but not forgotten: http://mazdaroadster.net/showthread....B&goto=newpost
    Instagram: @greasemonkey2000

  8. #6
    3,000 rpm - starting to feel the power atlex's Avatar
    Drives
    blue, white and two-tone
    Location
    Empordΰ, Catalunya, Spain
    Join Date
    May 2016
    Posts
    964
    Thanks Given
    486
    Thanked 435 Times in 242 Posts
    There's nothing wrong with a motor running as high as 220F, with the system up to pressure a motor can run safely over that. They're _designed_ to operate at these temperatures since the 50:50 Coolant mix is designed to pressurize which increases its efficiency and the boiling point changes to be higher than the 223F, at 15 PSI it's actually more like 268F. that's a touch over 40 degrees of 'headroom'. 'Don't open while hot' means something on the rad cap. Ne touche pas, Baka ! Because if you open it while hot the engine might be over the atmospheric boiling point, causing it to quickly boil the coolant when you ignored the warning and undid the cap.

    As Greasemonkey2000 states, the point of the thermostat is to get the engine up to peak efficiency (temperature) as quickly as possible before then allowing cool coolant to flow into the motor, and this can show you hitting 220F or a touch beyond as the coolant pressurizes prior to the stat opening, and again, there is nothing wrong with this behaviour. The coolant system of the miata, while not as perfect as is could be (transverse engine origins..), has proven to be extremely reliably engineered for normal use. Thermostats are a service item, not a weak point in the Mazda engineering.

    The undertray's cooling function is to increase/stabalize a low pressure area under the car, which helps draw air through the radiator, past each side of the motor and the transmission tunnel. Without the undertray you basically generate excess turbulence under the car. In fact there is a mod that can even lower UBTs over the stock undertray/setup by adding a small upside down gurney flap at the end of a cut OEM undertray, because it increases the size/immediacy of the low pressure area I've just described.

    https://rev9autosport.com/nielex-und...r-end-lip.html
    Last edited by atlex; 08-22-2022 at 05:04 AM.

  9. The Following User Says Thank You to atlex For This Useful Post:

    freedomgli (08-30-2022)

  10. #7
    3,000 rpm - starting to feel the power freedomgli's Avatar
    Drives
    1991 Miata
    Location
    Oak Hill, VA
    Join Date
    Nov 2012
    Posts
    2,021
    Thanks Given
    325
    Thanked 1,052 Times in 418 Posts
    Quote Originally Posted by atlex View Post
    The undertray's cooling function is to increase/stabalize a low pressure area under the car, which helps draw air through the radiator, past each side of the motor and the transmission tunnel. Without the undertray you basically generate excess turbulence under the car. In fact there is a mod that can even lower UBTs over the stock undertray/setup by adding a small upside down gurney flap at the end of a cut OEM undertray, because it increases the size/immediacy of the low pressure area I've just described.

    https://rev9autosport.com/nielex-und...r-end-lip.html
    Thanks for the awareness. I think I’ll add something similar when I make my own custom front splitter and undertray to interface with my aftermarket front bumper. I just haven’t decided whether it’s worth the hassle to continue the flat floor aft of the stock engine under tray since I’m not building a dedicated time attack racer.

  11. #8
    5,000 rpm - there be torque here! Greasemonkey2000's Avatar
    Drives
    2001 NB2 aka Misfire
    Location
    Temple, Tx is where Chad resides.
    Join Date
    Nov 2013
    Posts
    3,922
    Thanks Given
    4,870
    Thanked 2,393 Times in 1,216 Posts
    Quote Originally Posted by freedomgli View Post
    just haven’t decided whether it’s worth the hassle to continue the flat floor aft of the stock engine under tray since I’m not building a dedicated time attack racer.
    Could just buy a flat bottom setup: https://www.rtheorymotorsports.com/s...-kit-1990-2005

    I have it along with R Theorys frame rails w/backing plates and their new brace kit...... waiting to be installed.
    '01 NB2 aka MisF1re: http://mazdaroadster.net/showthread....218#post207218
    '97 M aka Warbird, gone but not forgotten: http://mazdaroadster.net/showthread....B&goto=newpost
    Instagram: @greasemonkey2000

  12. The Following User Says Thank You to Greasemonkey2000 For This Useful Post:

    HarryB (08-31-2022)

  13. #9
    3,000 rpm - starting to feel the power atlex's Avatar
    Drives
    blue, white and two-tone
    Location
    Empordΰ, Catalunya, Spain
    Join Date
    May 2016
    Posts
    964
    Thanks Given
    486
    Thanked 435 Times in 242 Posts
    I'm running the Moss stainless undertray on one of my cars (the blue turbo)

    that R theory looks amazing, I wish we had someone offering that in povertyspec euroland.

  14. #10
    6,000 rpm - mere mortals would shift HarryB's Avatar
    Drives
    '04 Strato Blue NB2
    Location
    Greece
    Join Date
    Jun 2015
    Posts
    5,718
    Thanks Given
    6,503
    Thanked 2,228 Times in 1,300 Posts
    Funny you said that; I have been working on something similar for my car. I have a complete 3D scan of the underbody which I need to clean up and then do all the CFD work, so it will not be ready any time soon though.

  15. The Following User Says Thank You to HarryB For This Useful Post:

    atlex (08-31-2022)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •