wthdidusay82

iTrader: (15)

Ok i havent yet put on this underbody tray thing and the car seems like it is running hotter than it should (goes up to a 1/4 then after 10-30 mins about 1/2 on temp gauge, and once it went maybe a hairline higher than 1/2)

the time it went a hairline above when i shut it off it was gargling etc for a minute or two

would having that tray out defintely be my cause to my problem ? or no

RETed

It's not guaranteed, but there's a good chance that it will make the car run hotter.


-Ted

therotaryrocket

i took out that tray on my turbo II, which also didn't have the thermostat and it ran less than quarter for an hour long hard driving trip. actually it ran at the same temp before and after removing the tray, so i don't think it caused your problem.

DrifterX

i had to people without the tray have there fc's start to heat up while mine and my friends didn't and we all were pushing the cars on a fun road.

homebrewer

No, I never put mine back on after I pulled my oil pan. Runs at same temp and no overheating while driving up steep mountain passes at high engine speeds.

idsigloo

the tray helps with air flow so that its smoother, but that's it. what's this gargling your talking about?

eage8

iTrader: (9)

my car didn't have one when I bought it... but I got one from my friend who has like a billion parts cars because I'm probably going front mount soon. and I'd just feel better with one.

GTUser

Read the thread above on the temp sensor gage and then you'll better understand the problem with registering accurate temps and how or if the undertray affects operation temps.

The tray is there to direct airflow thru the radiator. In order to cool the coolant running thru the radiator air must flow thru the radiator. Air like any fluid will flow along the path of least resistance. Air pressures also affects the flow of air and the faster the air flows the lower the air pressure is (A vert's top bulges out because the air flowing around the passenger cabin is at a lower pressure than the relatively still air inside the passenger cabin.

Without the undertray in place air has a lot of options about where to go. The air moving under the car is going faster than the air at the front of the car that hits the radiator. A lot of air can bypass the radiator and flow under it to the low pressure area, thus the radiator becomes less efficient when the tray is missing. With the tray in place the air hitting the radiator has few flow options and more will go thru the radiator since the route out the bottom is restricted. Thus the radiator is more efficient with the tray mounted and your car will run cooler since the radiator will have more air thru it. You may not be able to see a change on the temp gage in the dash but you will if you have an accurate aftermarket gage.

Agent_D

iTrader: (2)

without a tray my wifes vert would heat up to ~3/4 on the gauge on road trip, 70-80mph, with it on, its never even thought about it.

SureShot

Another issue is the oil cooler.
The rotary engine get almost half of it's cooling through the oil.
The fan pulls air through the radiator, but not the stock oil cooler.

Have a look under there & you will see what I mean.

An oil temp gauge really shows the difference when the front bottom duct in in place.

While your there, clean out the leaves

MARTIN

I agree. Removing the duct wont have an affect on your water temp at all.. I noticed no difference with or w/o it mounted. However, your oil temp is partially affected...

alwayssideways

3rded . oil temps are a lil bit higher. not coolant

SureShot

FWIW I also have the front edge of the bottom duct lowered & connected to the trailing edge of the chin air splitter.

I can run the AC full blast and cruise on I95 at 95MPH with the outside temp at 95 degrees & 95% humidity.

I call it haulin ice!

wthdidusay82

iTrader: (15)

the gurgling i am talking about happens after i drive the car until the gauge reaches 1/2 and sometimes i will hear gurgling out of the radiator / hoses, and u can see where the fluid and steam is spitting out from the hose that goes into the overflow if u take it off and look yourself

i dont know why its running hot like this , but it will be at a 1/4 then after a bit of driving goto 1/2

i am thinking of getting an aftermarket gauge and putting that tray on but i still dont see what the real problem is

edit - also someone said the oil could be gettinghotter without the duct, what effect does this have on things ?

Aaron Cake

iTrader: (1)

You're not really going to notice hot oil on the the water temp gauge, but you WILL notice it when you begin to wear out your oil o-rings and the car starts to smoke. Hot oil also looses it's lubricity as the temp goes up.

The undertray is not only important for cooling, but it also prevents debris from flying up off the road and puncturing the oil cooler and rad.

As for your cooling problem: http://www.aaroncake.net/rx-7/cooling.htm

sirx7

with out tray i heat up very fast with tray car is nice and cool

wthdidusay82

iTrader: (15)

my car smokes but i would hope its not the oil rings, since it just been rebuilt and only has about 150 miles on it, i would think the smoke will take at least until 500 miles to go away ?i dont knowi just hope its fine i would think it is

NZConvertible

They still seems to mass misunderstanding about how the cooling system actualy works. The engine's temp is controlled by the thermostat. If the undertray is removed, airflow through the radiator will be reduced (and I challenge any one to prove me wrong on that). This will cause coolant temp to rise slightly, which will cause the thermostat to open a bit more to increase coolant flow through the radiator. So temps will remain okay. But what has happened is that the cooing system's efficiency and hence its heat rejection capacity has now been reduced, because more coolant flow is required than normal to keep temps stable. This means that under load and/or in high ambient temps when the cooling system works hardest you will reach the system's capacity sooner and then temps will rise.

The oil cooler is a different issue. It's thermostat is only there do disable it while the engine is cold. Its open by 150degF and stays fully open until the engine is off and cools down. It doesn't regulate oil temp like the coolant thermostat does. Since the airflow through the oil cooler will be also reduced if the undertray is removed, then oil temps will increase.

So if you still think driving around without an undertray is fine, you're an fool.

MARTIN

I dont notice a difference in temp with the tray on/off. There is no reason not to have it on, but it doesnt make any difference on the water temp. Oil temp might be a different story, but I dont have an oil temp guage so I cant say.

staticguitar313

iTrader: (2)

i live in AZ 105+ temps, the tray helped a little but not much, i run a stock cooling system and no IC yet, i never see more than 1/2 the temp guage (S4)

NZConvertible

Didn't I just say exactly that? It won't make any difference until you reach the cooling systems now-lower capacity.

Then don't you think you should put your tray on?! Why are you risking it?

MARTIN

I said... That there is no reason for you not to have it on, but I dont have mine since im lazy..

Wankel7

And when you don't run an underpan your engine bay seems to get rather dirty.

And it does help out the oil temps

Aaron Cake

iTrader: (1)

With only 150 miles, you have hardly made a dent in your breakin. If the engine was reassembled with used hard oil rings, then it can take some time for the smoke to stop. If it was assembled with all new stuff, then it shouldn't smoke much or at all.

wthdidusay82

iTrader: (15)

it smokes the most when it first starts up, and still seems to smoke when it is all the way warmed up(but not as much), it was rebuilt by kevin landers, i dont know if he normally replaces all the old oil rings or reuses them if they are in spec.

I cant really tell u what color the smoke is , all i can say is it smells like gas pretty bad when its idling from the exhaust

He took the engine apart in front of me and i think he told me everything looked good as far as the internals and seals etc, the engine was bad due to a busted water jacket on one of the irons and that one rotor looked a like it had surface rust or whatever so it would be harder to take the rotor apart etc but could still be taken apart and used

Also as far as the coolant temps. If my heater hasnt been used (doesnt turn on) would this cause any problems with air staying in the coolant system ?

Do you need to bleed coolant sys several times before it will be completely bled ? thought maybe this is why the temp rises after so long of driving (10-20 mins street driving)

Coolant/radiator hoses are spongey and not stiff after the car has completely cooled down, ( but when its running and all warmed up it has plenty of pressure).

Also seems like the coolant level goes down a little bit too after car shut off and is completely cooled down(from coolant going into the overflow), is this normal ?