Tim Benton

iTrader: (1)

I had to go to our Atlanta plant on Thursday so I drove the FD for a little fun on our interstate road system. I was just lucky we didn't have the usual traffic slowdowns/stops on the way there, but then again I left at 5 am to be safe. on the way home, I was doing anywhere from 85-95 mph in 100 degree heat and watched my PFC water temp hit the 101 mark for the first time, all while doing the speed stated above. I have the mazdacomp radiator, ducted nicely, touring model, stock front nose. I dropped my speed down to 70 and my temps quickly dropped to 93ish to 94. I again started doing 85 - 95, who can't resist the ease and stability these cars give, and my temps crept back up to 100, 101. Dropped down to 70 to 75 and temps again dropped to the 93 94 range. My guess is that at the higher speed, I wasn't getting enough air passing through the radiator and it was just coming back out the front opening. At th elower speed, air was able to pass through sufficiently and cool things off. Anyone else notice this on extremely hot days and the speed your going in relation to the temps your seeing. Granted a 99 spec nose would have a bigger opening, but if the smaller volume of air the 93-95 nose lets into wasn't able to make it through the radiator, why would the larger nose allow any more air through. The bottle neck in my system seems to be the mazdacomp radiator as far as letting air pass through.

Comments or ideas?

Tim

xblazinlv

Read this thread:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/why-am-i-still-running-so-hot-561436/


Same thing, and that's perfectly normal. I guess you guys who normally don't see 100 degree heat aren't used to this kind of thing lol

The Vegas guys know all about it, and it sucks. Once you slow down, it almost instantly cools down to 93-94c

Tim Benton

iTrader: (1)

Great, I basically reposted it

Good reading in that thread as well.

Tim

ExpensiveHobby22

Waterpump getting inefficient at higher rpms? Cavitation? Just a thought.

cewrx7r1

iTrader: (2)

Tim,

Last weekend Kyle and I drove up to and back from Houston to Dallas. The air temps were in the high 90s both ways. We were cruising 80-90 with the AC on , and my water temps were 88-89C by the PFC, cooler by Autometer.

75% distilled water, 25% DEXCOOL, 1 bottle Red Line Water Wetter.
An 1999 era M2 radiator which is smaller then the new Koyos.
N-Tech copied single shark mod to the nose.
Both plastic nose corner pieces removed, with cutom blocking plates.
Blitz FMIC.

Oh Yea, R1 = dual oil coolers with RP 10-30 oil.

Mazda Comp copied CF hood from http://www.atihun.com/ati-hardt.html.

Tim Benton

iTrader: (1)

Chuck,

I'm roughly 70% water/30% antifreeze and also use 10/30 RP. I thought about using the extra passenger side opening to duct some air to blow on the turbos just for the heck of it. I got a hood from Attila back when he first started making them, fitment was spot on but the vent openings barely cleared the M2 med IC and I had to make a small notch in one of the support braces to clear the inlet piping. I think my plastic end pieces are still on the car. I took the fog lights out, but can't remember if I took those off.

How's Kyle's car coming along?

Thanks for the input Chuck, gives me some things to work on and compare.

Tim

cewrx7r1

iTrader: (2)

A view of the driver's side inlet with blocking plates.
I have a protective SS screen in front of the IC to protect it from rocks.
Because the plastic ends are removed, some air can go around the IC to the radiator.

The shark mod pushes the nose down 1 inch.

All those little brown specs are dead bugs from my trip to Houma La. last month.

Kyle is slowly making progress with the LS1 conversion. His electric water pump just arrived.

AndrewDevlin

Ive got some comments and some ideas,

You make reference to your temperatures being ~ 70 - 100 deg F. Thats way too low for an engine to be operating.

Secondly you quote an outside temperature of ~100 deg F while an engine water temperature of ~ 70 - 100 deg F. That my friend is impossible. You must have one of those magical radiators ive been hearing about.

Unless you have read your gauge wrong, then you have broken all laws of thermodynamics. Im sorry but those numbers cant be right.

However, if you are experiencing heat problems at higher speeds, the problem is likely airflow related. Yes at higher speeds you should naturally flow more air through the core as there is a greater pressure at the face of the core. But however if the air escaping from the engine bay cannot do so freely, there will be an increase in pressure behind the radiator effectively limiting the amount of air you can flow. Airflow is ~ proportional to the pressure difference across the core, which in your case is decreasing (ie front pressure - rear pressure) as speed increases. Remember as heat load from the engine increases so does the need for airflow. (ie. increased drag = increased power = increased heat rejection to coolant / heat load)

No changes in anything mechanical can fix this. Nor will enlarging the front duct. Its a problem all cars have and unless you can vent the air better (ie top exit) your stuck with the problem.

GoodfellaFD3S

iTrader: (213)

Before you post up a lengthy dissertation of condescending drivel, consider this:

The Apex'i Power FC Commander measures coolant temperature in degrees C. Not once did Tim use the letter 'F' in his post. No magical radiators here. The land of oz indeed.......

artowar

iTrader: (1)

Lol

kerry chandler

....doh!!!

xblazinlv

lmfaooo

AndrewDevlin

Wow, the Apex'i Power FC Commander. Its funny how everyone thinks these a the be all to end all. Hardly likely. Just good marketing.

How about this then, maybe he should use consistent units or if not be specific. He does mention 100 degree ambient, and being as it may 100 deg C is alittle difficult.

SO before you try to trump me, you better have more thave more than just that next time.

I did offer him help, but ovbiously you guys think you got it covered just by replacing parts until you think you've found the problem. Be my guest.

MazdaSpeed93

I'm surprised that you are trying to correct a man that probably knows more about these cars and the parts that go into them than anyone on the board. I am sure that he knows exactly what he is talking about when it comes to this stuff. Just read a little bit closer next time and stop posting with all of this knowledge that you think you have.

GoodfellaFD3S

iTrader: (213)

Hm, how about this then: maybe you should refrain from making absurd assumptions, and apologize when you're needlessly a jerk to a forum member (in this case Tim). Admit it, you feel silly

Rich

Sgtblue

iTrader: (16)

Rather than the radiator, could the fans be a factor here? Smart people chime in, but I was wondering if, at high speed, the fans provide progressively more resistance until they become counter-productive.

Joe Geiman

100c is boiling but it's not a problem because the system is pressurized, that raises the boiling point. We used to have a problem in road racing where the driver would bring the car in off the track because the water temp would read 250-260 degrees F. We would have a 25# cap on and the coolant was not boiling. What we did after that was tape up the guage so the driver couldn't see it. If it's not boiling over, then it's not too hot.

cewrx7r1

iTrader: (2)

At Tim's temps if the AC is on, then the fans should be at speed two.
If Tim is runing the FC thermoswitch like I do which turns on at 207F then the fans will be at speed three as 100C is 212F.

When I read Tim's post about his temps, I being an above average mechanical knowledgeable and intelligent person; perfectly understood him.

Many of us have noticed a lot of posts by people who probably can not take a bicycle apart and reassemble it without asking for help.

Tim Benton

iTrader: (1)

I will remember next time to differentiate the F and C when I'm posting. I did have the AC on and do have the FC thermoswitch as well like Chuck just stated. Although I did mention 70 in my first post, it was in regards to 70 mph, at which point my water temps dropped to 93/94C. I looked last night when I was changing my oil since I hadn't changed it since my last track day and noticed I still have the 2 small plastic pieces in the nose of the car. I'll take those off later today and if I drive the car again in similar conditions, I'll see if they make any difference.

Chuck, one thing that I appreciated while driving through TX a few years ago was the people in TX pulling to the right shoulder, not slowing down, to let a faster car pass on a 2 lane road. Wonder how that started?

Tim

cewrx7r1

iTrader: (2)

Someone probably shot at them. We Texans love our weapons!

rynberg

Tim, your temps seem fairly normal to me, although they could be improved. My mods are in my sig....cruising in 100-105F ambient at 80-85 mph with A/C on, my temps are 95-97C on the PFC, 204-207F at the t-stat housing.

I still have fog lights and plastic corner pieces.

AndrewDevlin

Oldfella, Im not going to appologise for anything as i dont believe ive done anything wrong. I was pointing out what i saw. Stop playing games you cant win.

As far as him knowing more than me about RX7's your probably right. More about engines, probably not.

Tim, have you tried running at those speeds without the AC on? It dumps heat into the system. Whether you have a separate heat exchanger for that i dont know. If you dont, try turning it off, may help some.

fdeeznutz

Who said it was the be all end all?

adam c

iTrader: (2)

I suspect that your "big" oil coolers are responsible for the difference.

Kento

Doubtful. The actual airspeed through the radiator (with stock ducting and underpan, even with gaps sealed) is probably slow enough that the fans and shroud don't really make that much of a difference, even with the car traveling at high speed, due to the resistance the radiator itself poses to airflow. If there was ducting that created a major negative pressure area behind the radiator (dramatically increasing airflow speed through the radiator), then the fans/shroud could become an impediment.

I tried not to make it sound condescending, Rich.