Blue87Sport

Getting back on track (a little Railroad pun)...

Certainly the single oil cooler on the AT model is suspicious as a contributing factor. How about the transmission itself. Does the AT have a transmission fluid cooler? Anyone know how much of a heat load the Auto tranny adds to the mix, especially in stop and go traffic?

I guess that wouldn't explain why the AT models in other hot climates aren't having this problem. Are you Aussies obeying the laws of thermodynamics down under?

And what about the role of humidity? Sounds like the problems are in hot & dry climates but not hot and humid ones. Doesn't humid air have a higher latent heat capacity and heat transfer rate than dry air? I wonder if that is a factor...

Anyways, its fun to speculate until the facts come in.

Cam

iTrader: (1)

RG,

I appreciate your opinions regarding rotarys, but I think your post might insight more panic (if thats possible).

To tell the truth Ive been taking the whole recall/engine replacements in stride, feeling MNAO will do the right things.

However, if you do feel this strongly regarding oil breakdown what should owners do?

Should I change oil weights? Go synthetic (not trying to start up the syn oil debate)?

Any insight?

rotarygod

I might be a little overly cautious in saying that oil temps should never go over 210*F but the fact that the car with dual oil coolers is running hot should definitely make people well aware of the importance of a very good oil and frequent oil changes in this car. As to the old oil debate I use Royal Purple synthetic in my rotaries. I actually go a very long time between oil changes in a piston engine car but it also doesn't work the oil nearly as hard as the rotary does.

I do find oil temps of 240-250 extremely disturbing. The real question though is how long do those temps stay that way? If it is for a brief second then not much will happen. If the oil gets to that temperature and then stays there for a while at a time, it is much more cause for concern. Remember I am concerned with high oil temps on a dual oil cooler equipped car. How high are the single oil cooler cars oil temps getting? This should be downright scary and you'll notice that the cars that have had the most issues have been those with single oil coolers in very hot climates. Coincedence? I think not. I can't explan why other parts of the world with hot climates haven't reported the same issues but then again maybe they have and it just doesn't get publicized like it does here. We are pretty nosey here.

The simplest fix I can think of is to install small electric fans on the back of the oil coolers and make sure that there is a good path for air to travel both to and from the coolers. Run these fans off of thermostat control. Most of the problems are going to be when the car is not moving or moving very slowly. This mod should probably be done to every car regardless of oil cooler content. It can't hurt anything. I feel a 2nd oil cooler for the car should be mandatory along with fans on them. We'll see if Mazda agrees with me or not.

While I don't necessarily want the RX-8 community losing sleep over my comments, I do want the owners to be very aware of their cars vital signs. If the car is running a fever, you should know about it. Treat this car like a kid until the doctor (Mazda) finds a cure. Just because another kid in the class is sick doesn't necessarily mean they will all get sick but that doesn't mean the possibility isn't there.

RotaryGoober

Are we seeing the fallout from damaged oil coolers, as in bent fins, that restrict air flow? RacingBeat may have seen the writing on the wall here with more than a cosmetic upgrade. In cities, like Vegas, the amount of stone chips and trash may be higher than in less traffic areas. It would be interesting to look at these coolers and see just how damaged they are. Just a guess but, automatic transmissions are a choice for many in urban areas, lots of stop and go driving. Add that to less air flow, more dented fins, higher oil temps and on and on..

Phil's 8

iTrader: (3)

I have lived in Vegas for thirty seven years and have over heated and burned up several motors and transmisions. One of my first mods to my AT eight was to add an transmission cooler and a second oil cooler. I looked at the radiator and considered work here also but as yet have not. My 8 is a weeked car so does not see much city driving but I drive it hard. The rev limiter and I are friends. So far no problems with the engine. Mazda replace my air conditioner completely and now it's working well. I've seen where the eastern contingent were talking about their high temps but I do not think they understand 6% humidity. Water in the air is actually a cooling factor. My car is in for a regular service today so I'll nose around and see what good bs is floating around.

TexasKyle

My comment and a question for RG, Brillo or any other Houston 8ers....

On a couple of occasions, after getting home and parking my car I noticed the cooling fan is still on. No big deal, right. Come back out 20 min later and the fan is STILL running. Temp guage did not show the car was hot, guage showed normal in fact. While I never paid attention to how long it usually runs after shutdown on a hot day....I know for a fact it has never run that long (excpet on the few occasions I am talking about)
Any of you Houston guys/girls notice this before? Could this be a precursor to some sort of problem? Any of you Vegas ppl notice this before having the problems you have now?
I have had no issues with my car before, no mods (other than Richard's shifter) and only drive it two weeks out of the month. Have had the car 12 months now, and only put 9k miles on it. (it has 14k on it now). Carbon buldup is defintely not an issue on this car. :-)

crossbow

Rotarygod,

Something we have started noticing in the Mazda6's. The stock transmission cooler is located at the bottom of the radiator (as is with most ATX's) and is cooled by the vehicles coolant.

Well it turns out, that it almost appears that the ATX fluid will start "heating" the coolant up something fierce if it starts overheating. In the case of the Jatco in the 6s ATX, the ATF fluid can get as high as 250-260F (its horribly undercooled), and seems to actually cause the coolant temp to spike up rapidly. (Nice secondary heatsource at the bottom of radiator =/ ).

In the case of the 6s, if the coolant hits 240F, the car flips into safemode, and forces the ATX into D (from M mode) changes the shifting pattern, completely throws the timing off, and appears to change the fuel map as well. (Timing is retarded almost 50% at this point).

I'm mentioned a few times the importance of installing transmission coolers on vehicles in hot areas (and on performance cars), but since it doesn't result in a HP gain, most people have ignored those threads .

For anyone considering that their car isn't overheating because "the temp gauge is fine"...is wrong. The stock temp gauge is a dummy guage. It has a HUGE dead zone and usually won't move from around 160F, to around 220-230F. In that range the needle will stay completely in the middle. The gauge is nothing more then a piece of flare on the dash...a sweeping idiot light.

If you want to know what your coolant temp actually is, you'll need a CAN capable scanner, or a temp sender and your own gauge.

As for the oil weight discussion...current tech oils are significantly better then those just a few years ago. Most 20 wt oils are superior in almost every characteristic to older 30 and even 50 wt oils. Viscosity is not a measure of protection! Its nothing more then a consumer label to aid in picking the correct oil for your application. You have to look at other specifications of the oil to try and figure out its actual ability to protect in high heat, high stress situations.

Redline 5w-20 for example, has a HTHS # of 3.3, which is higher then 10w-30 mobil1, and even higher then a large # of 40 wt oils. HTHS = high temp, high sheer, or the oils relative resistance against sheering/breakdown in something like a bearing or an extremely intense (heat/pressure wise) part of the engine.

Gomez

Hi crossbow,

Do you know this as a fact for the RX-8.....or is this your experience with the Mz6?

missinmahseven

Seems to be mazda practice. The miata has the same style gauge.

It's not a dummy gauge in the sense that it's not ON/OFF. What it is, is Non-LInear.

You can have a huge rise in engine temp, and not show needle movement. Then a little bit more heat will cause it to swing towards "Hot".

I wish it were linear. And I wish we had a real OPG again.

marcj1

I was just about to ask if anyone had any insight into the accuracy of our temp guage. Our oil warning light isn't of much use, perhaps the temp guage is also less than precise.

missinmahseven

There was a trick to the Miata temp gauge. In mine, it *always* would point at roughly 11 o'clock. Any further to the right of that and you had temp issues -- even tho it wasn't anywhere near the H mark.

By the time it gets to the H, it's Too Late.

I bet real money the 8's gauge works the same. As soon as it slightly departs from its normal place, you've got a problem. Don't wait for the H. By that time it's too late.

We all know why this is so -- same reason the OPG is now a dummy gauge -- it's because dumbass owners would see both gauges changing readings all over the place, and complain. THEY"RE SUPPOSED to move!

So, make 'em real again, but borrow a page from aircraft gauges: Have a Green Zone, a Yellow Zone and a Red Zone. In the green, you're OK, in the yellow be careful, in the red, you're dead.

The trickiest is the oil pressure, because it reads sky-high when stone cold, and drops as the engine warms.

I hate it when things get dumbed down because of the lowest common denominator. It seriously chafes me.

Sigma

That one is easy too.

Just have variable 'zones'. When you start up, the zones could actually reverse (or anything you wanted really). I.E. 25psi in a cold engine == BAD. But 100psi is good. As the engine warms up, the zones could slowly shift over.

Then the hard part becomes explaining that operation to the consumer.

Some high-end cars do something very similar -- their redline moves. As the engines warms up the redline and the rev-limiter moves further and further up the tach. You can actually watch it move.

missinmahseven

If nothing else, it'd make for a very trippy dash :D

As for the sliding redline, ours actually do that. Car stone cold, revs won't go past 6k (this is for MT). I know the actual redline mark doesn't move on ours, but the ECU won't let you get over 6k.

Or so the manual claims. I haven't tested it, and don't particularly care to try it out. I dont like spanking a cold motor.

Seen recent BMWs where you do see the redline mark move. Trippy.

bureau13

The FD temp gauge was infamous for this. All it ever really did was provide a false sense of security...if it moved north in any detectable way it was pretty much already too late. I had hoped they would have figured this to be a bad thing, but apparently not (and the fact that they went to something equally useless for oil pressure should have confirmed it for me).

For the FD someone came up with a linearization circuit to put on the back of the cluster, but I'm not sure how feasible that is for the 8...I know modifying the oil pressure gauge appears to be a lost cause.

jds

Oktobernv

AS far as the engine coolant temp guage on the RX8 goes.....

This is what my service rep at Magic told me 3 weeks ago.


When I first called Magic and had my 8 dropped off for service after losing power and getting the "metallic rattle" from the engine again, my service rep asked me:

(service rep) "So does the temp guage look hot or normal when you start to lose power?"

(me) "normal......doesn't move at all"

(rep) "that's what I figured. The problem is that the temp gauge is reading the engine coolant, which appears to be normal, but the ACUTAL temp on the engine block is OFF THE CHART. The engine is burning up. There is no temp sensor on the block itself"


Also, I have experienced the ENGINE FAN RUNNING for extended periods of time after I shut the car off when it is hot out. A good 10-15 minutes.

I will be stopping by Magic today to get an update on my 8.

I will inquire about the oil coolers and oil weight issues we have been discussing.

Will report back

Rob in Vegas.

Gomez

That is just rubbish as far as I'm concerned. Someone correct me if I'm wrong, but I have never heard of a car with a block temp sensor. They all have coolant temp sensors.

missinmahseven

Rob, I think I've said it before -- the more you tell us what your dealer says, the dumber he looks.

Gomez is spot-on: No such thing as a block temp. sensor. There's a water temp sensor. However, guess where that mounts? Into a hole in the block.

The scenario your service rep paints is highly unlikely. Think it thruogh:

1. The block gets hot because of the combustion going on in it.

2. That heats the coolant inside the block, to the temperature of the block.

3. It follows, if the 'engine is burnin' up" your temp gauge WILL show it. Maybe a small needle movement, but it will show it.

May I kindly suggest you find a dealer with a clue? Prefferably one with a tech or two who've been certified by Mazda for rotary engines, and even then, try to find rotary certified techs who've been doing for a while.

In other words, I wouldn't trust your dealer to fix a broken screwdriver. Plainly put, from what you tell us, he's an absolute retard when it comes to engines, and his information is *not* to be trusted. That's just my opinion, mind you.

Sigma

If the engine block was "off the chart" I would think that the coolant would have to be as well. And if the engine fan is running it knows that it's running hot.

Sounds to me like it's just the coolant gauge in the car that's the problem; not the fact that there is no sensor on the block. The coolant would have to be hot if the engine was hot, unless it was not getting to the engine, and the car knows that it's running hot, which is why the fan stays on. So everything points to a gauge not working properly.

zoom44

thats my experience witht he 8. nothign nothing nothin gthen PEGGED

zoom44

the RX8 red line is rev limited when cold. and moves up as the engine warms. no indication tot he driver from the guages however. that is trick.

zoom44

well they had the engineer team there to back them. i bet he does understand what is happening and just doesnt relate it well to the customer.

missinmahseven

I dunno, man. In general, my experience with MNAO service managers rates from poor to downright dangerously ignorant, with two shining exceptions.. one in Biloxi, MS and one here in FL.

The rest of 'em... they should hang. One tried to tell me my Rx-7 needed a 'valve job' when it was running rough. (An igniter lead had fallen off... the guy in Biloxi looked at the car, plugged the wire back in, and the 2nd rotor lit off like magic.. valve job my foot.) This was *before* I had educated myself to the intricacies of the Wankel. But even then I knew these engines have no valves.

In Fairbanks Mazda (now sold to Bachrodt), the SM wanted to put some triple-digit weight gear oil into my Miata's gearbox.. and charge me 400 bucks for it. The car calls for 90w. See?

Just because they had engineers there from Mazda, and these engineers explained it to his SM, doen't mean his SM understood what's going on. Or as you said, it doesn't mean he can clearly communicate what the engineers say.

I know it seems as I'm harping on this, but Rob's SM sounds very dangerous from what Rob is writing here. Like the kind who'd sell you a 'valve job' to fix a rough-running 13B.

We really need to get Mazda to get better people to handle service. The techs for the most part, I've noticed they're fine. The managers, on the other hand... ugh.

sharward

How about accurate gauges with actual numbers on them (what a concept!), each with three indicators beneath them, only one of which is visible at a time:There... Gauges that smart and stupid people can both love! :D

The indicators would allow for "moving redlines" based on the conditions (e.g., oil pressure when engine is cold). The gauges themselves would have only numbers on them -- no redlines (except the tach, of course).

Too bad I was unable to find a GIF of the famous blinking "A Little Hot" instrument panel indicator light from the movie Airplane! Wouldn't that have been perfect? :p

And the fuel gauge can have the indicators too:

Gomez

I've had plenty of old cars boil on me with the gauge indicating in the normal temp range. Generally occurs due to loss of coolant. No (low) coolant means the sensor measures the air temp in the coolant passages, and since air doesn't conduct heat as well as a liquid, the gauge doesn't read as high. This is not occurring in the RX-8 though as it has a recovery tank.

Hmmm, a thought from left field. Try this on for size. I wonder if a sizeable air pocket in the engine is masking rising coolant temperatures in these Vegas cars? I know my car has an air pocket, the thing gurgles through the heater core on every cold start. Plenty of people have reported the same issue, I've just never bothered to clear it. I'm not experiencing 120 deg days ATM, either.

missinmahseven

I would ammend the last step of the gas gauge to read "Got Sneakers?"

:D

Seriously, I like that idea.. a 3-color LED, have the ECU tell the driver if what he's seeing is normal, creepy or downright scary/fatal.