there have been some posts by people saying that they went to WOT at various times and the car just wouldnt accelerate or it seemed like they hit the rev limtier when they actually hadnt.

one of the responses usually given is that the car lowers its redline when the car is cold so the original poster maybe running into that. that is true when the car is cold.

however some have gone on to say that the car was in fact warmed up because they had been driving for a time before this occured. some of us have suggested getting the coils looked at. when talking with jim mederer at racing beat this past sunday i was informed of another possible reason. he said that along with lowering performance and redline when cold the PCM also does it when it decides the engine IS TOO WARM. so for those that have experienced this sort of thing in the past or do in the future there may be nothing wrong except that the car is too hot. let it cool a little and the problem will go away. its just another way for the PCM to protect the engine.

they are learning many many things about the pcm over there. the test bench is very cool:)

:)

Odd. I thought the problem solely lied within the electronic throttle circuit. I miss mechanical throttles. :(

It was pretty neat watching Jim play with the ecu bench. He'd hold it at one rpm and then turn a knob that told the ecu that the coolant temperature was lower. You could watch the timing retard itself. The timing was affected by alot of things. He stated the car reduces power in the event of overheat. If the water temp gets too high, the ecu cuts power. It will eventually cut power to the point where you can just keep the car running. You know when this car overheats.

Ohhhh... that explains why I was ranting about how slow my 8 was a month ago when I was driving it all day on a hot Saturday! By 5pm, it was slower than what I was used to and once it's off, the fans didn't stop for almost 30 minutes.

Could adding water wetter change this? I have been looking at solutions to cooling the engine or engine bay more. I hope someone comes up with a great solution!

spot on xyntax- i couldnt remember the various members who had mentioned this but as soon as i heard it at racing beat i knew this was the answer to some people who have encountered it like yourself.

SHit, so this is like the intake temp gauge that some users have on 7's

i always wondered what the hell they were talking about, it all makes sense now!

Intake gauge? You mean that's where the engine determines if it's time to slow down or not? I have monitored the intake temps in my Canscan before and I gotta tell ya, it gets hot in there. I'm not sure what the borderline for intake temps is though, but mine reached above 100s or 120's in there. I'll check again this week and see what numbers I could get.

The ecu will reduce power dramatically when the water temp reaches 120 degrees C. Optimally you'd like to see it hover somewhere around 90-95 C or so when you are just cruising around.

how can we rig up an indicator ?

how can we rig up an indicator ?


How about installing an aftermarket digital water temp gauge.

How about installing an aftermarket digital water temp gauge.will a water temp gauge fuction the same as an air intake temp gauge?

dang, I think the car is smarter than most people I know..

I find that the RX-8s computer is too obtrusive. Hell, it prevents acceleration for some people as stated above, and won't give proper readings on a dyno.

At what coolant temperature does the PCM start to change behaviour? Is 120C the start or does the PCM start reducing power output at lower (but still high) coolant temperatures?

will a water temp gauge fuction the same as an air intake temp gauge?


Oops. One person was talking about intake temperatures in F and I was referring to water temperatures in C.

wow. I've experiened power loss after driving around in traffic for a while in the summer. I just thought I was dreaming! Is this thing "self-aware"? haha

Damn near self aware!

To my knowledge the PCM does not reduce fuel injection or ignition when the ECT is over a certain temperature. It just operates the cooling fans. If the IAT and ECT readings combined indicate a high intake air temperature, then corrections will be made to the fuel map to compensate.

There definitely is a fuel cut at low engine coolant temperatures though, which I am sure many of us have felt!

That doesn't explain the power loss at high load/rpm though. Maybe excess blow-by? It sounds like more of a fault than fuel-cut to me.

We learned about this power reduction while at Racing Beat. Jim Mederer was demonstrating the ecu test bench. He had the ability to change values to fool the ecu into thinking the car was running a certain way when in fact there wasn't even a car there. When he changed the water temps, the timing drastically retarded itself and fuel injection output was decreased. It was a neat setup.

I wonder what it would be like if there was a self-aware stand-alone EMS.

All this and they can't put out a software patch to make the "gauges" on the dash actually behave like gauges.......

I experienced power loss at high rpm, but it was very abrupt - like the fuel (or air) was cutoff. And I also got a check engine light (which went away on it's own). The car was up to temp when it happened, and I was exercising the motor on a back road, but it wasn't that hot that day (perhaps low 80's) and it was nothing like track use. If the car was cutting power due to coolant temp under those circumstances I'd be very disappointed.

There have been several people who have done track days and to my knowledge none of them have experienced what I have. I could see a gradual loss of power as the car gets hot, but in my case it was abrupt.

All this and they can't put out a software patch to make the "gauges" on the dash actually behave like gauges.......

no because the sensors that the guages get their info from cant do anythin but turn it off or on. you'd need different sensors.

george your's sounds more like misfire or knock. and its not air temp but engine temp. even on a day in the 80's if you ran the car hard enough the engien could get overheated. also obviously it can be caused by a break down in the cooling system.

I really don't see an overheat issue with the RX-8. It has adequate cooling. The 3rd gen RX-7 had poor cooling but there were so many other things that contributed to this.

george h
just a thought. if you felt an aburt loss of power it could also be your gas pick up. Some people on the track have stated that if the tank is less than 3/8's full then there is a possibility of a failure of the gas pick up from the tanks. Seems like they may need a baffle in them. (when driving hard of course) on the street no problems.
yes I hate this intrusive ecu. damn cars have gotten to complicated. I admit some things are better, but I hate not having control of what I want to do with the car. It's MUCH more difficult than it should be. All in all though its a great machine.
I dont know how fast your where going but I do know that pre filter air absorbs MUCh ambient temperature below 60-70 mph. I did some measurments some time back and if I remember correctly on at 90 f day at 45mph the pre filter air was around `121 f and on the same day on the interstate at 65-70 mph the temp was at 92.
olddragger

So what happens when you live in Las Vegas or Nevada?

Your car is a dog?

So if I drive to Las Vegas from California and its 125 degrees outside my car is a dog and a SUV can pass me?

What matters are the coolant temperatures. If they get up high enough then yes. Most likely they won't though. If you are really paranoid switch over to Evan's NPG coolant. It runs cooler. It is also not compatible with water so must be the only fluid in the system. It's about $30 per gallon.

Would going with the MS (or other aftermarket) sports radiator help with this issue?

Of course our cars are self-aware. When you turn on the key the display says "Mazda RX-8".

How much more self aware do you want? :-)

I'm a newbie, bear with me...

I've been lurking here for months now. I'm in grad school, eagerly awaiting that first new car purchase when I graduate. I test drove a yellow 8 a couple of weeks ago and loved it. I think I can deal with the relative lack of power. Mazda is smoking some serious crack if they think this car is making 238 hp. It's probably more like 210. But that's okay -- the smoothness of the power delivery is intoxicating. The car was *so* fun to drive, and that's what matters, right? It was just so responsive and connected to the road. All that stuff about the car being an extension of your will -- that's not marketing BS! And I love the cockpit sensation and the position in the driver's seat and the way the controls are layed out... 1st class all the way.

I'm just having a lot of trouble with the quirkiness of this car. I don't know if I could live with it. Let me get this straight -- when it's too cold, it pulls timing. When it's too hot, it pulls timing. It can get too hot from just driving around town in warm weather. It sounds like my last girlfriend! I mean, seriously! Do you have to take it out to dinner and give it expensive flowers and blow in its ear to get it to put out (the power, that is)?!? I don't want a car that argues with me. I don't want a car that is self-aware. I want it to go like stink on my terms when I tell it to. I don't feel like arguing with a damned computer!

I plan to autocross my next car and do track days with it. If the 8 is going to overheat that easily and stop making power when I need it, I might have to choose a different car. And I don't want to do that, cause I love the 8. Especially in lighting yellow or winning blue.

Can anyone reassure me?

Seriously, the 8 must have THE most intrusive engine management of any car on the market!

I REALLY want to love this car. My heart says yes... my mind says maybe.

No. Don't buy it. Go buy an old Z (or ooold '7)... you know... one with a carburetor and no ECU... Those aren't intrusive.

Like MM said, most engines are getting this way. It's to keep you from killing the engine. If you want to be able to kill it, get a carb driven motor and then you can set it up the way you want.

For the most part the MFG knows the tolerance levels and aren't going to LET you kill an engine. It seems normal to me. It's like a lock on a gun. It's there to keep things safe.

Nah, its a lot more than that. Its also to allow them to meet emissions and mileage targets. If those aren't as important to you as to the manufacturer (likely true in most cases) then that may be a trade-off you don't want.

That said, while the ECU in this car is pretty damned controlling, I haven't found it overtly irritating.

jds

No. Don't buy it. Go buy an old Z (or ooold '7)... you know... one with a carburetor and no ECU... Those aren't intrusive.

Like MM said, most engines are getting this way. It's to keep you from killing the engine. If you want to be able to kill it, get a carb driven motor and then you can set it up the way you want.

For the most part the MFG knows the tolerance levels and aren't going to LET you kill an engine. It seems normal to me. It's like a lock on a gun. It's there to keep things safe.

Just experienced the same reduction in rev-limiter limit.

I was testing my car after they changed the electronic throttle body, which was faulty. Well, the knocking at 6500rpm went away, but another surfaced:

On the 20mile run, 10 miles each way I experienced this: Going out, the first half seamed fine in all the gears (although the car doen't pull much beyond 120mph). This section had a long gentle uphill on the last 5 miles.

After turning back, I could only get the car to reach 135mph, down hill with a tail wind. Then a little later on the final stretch back, in 5th gear, I tried to get the revs up to 8000rpm, but when pressing the throttle to WOT, the revs suddenly cut at 7500rpm. It felt like a controlled event, but was quite dramatic. How can the engine be considered too warm when it was cold outside (13 deg C) and I was not in traffic? What's going to happen on a 30 deg C day?

Damn, a BMW 330i with the same quoted hp will run away from this car. This just irks me no end. There is no way this car has the full quoted hp! Besides that, the engine management system just gets in the way all the time.

I am now on the verge of kicking this car back to mazda for a refund. I paid for a performance car, and all I have is a car that just wimps out in the engine performance area.

Although most of us never really use 100% of the engine performance, this type of problem gives the car a bad reputation amongst sport car enthusiasts. This in turn kills the resale vaue of the car and that is a big problem for me.

Sorry for the rant guys, but that's the way I feal right now. I could do with some positive news or views to get me out of this freaked out state.

i should mention that i have not had this happen to me. coming back from cali last sunday driving with 3 other 8s for extended periods between 85 and 115 mph some of that climbing into the mountains i never experienced any over temp situations or loss of power and neither did the others. it got as hot as 100f air temp i think.

Thanks zoom44, that's very reassuring!

Robertdot, I'm not one of those rednecks who complains about fuel injection and bemoans the golden days of carbs. I just think that the RX-8s ECU is more active than the ECUs in a lot of comparable cars. Now MazdaManiac may be correct when he says that the 8 is ahead of the curve... I don't know. I just think about all the trouble aftermarket companies are having with the 8's ECU (canzoomer, etc) and the difficulty people have had in dynoing the car. It has led me to conclude that the 8's ECU is quite fussy.

Maybe it is better to think about this in terms of costs vs. benefits. What are the benefits of the 8's active ECU for the driving experience? Do rotaries inherently require more management than piston engines?

One more thing... would anyone comment on the ramifications this might have for future forced induction mods? Wouldn't this tend to increase the operating temperatures of the motor?

Maybe an aftermarket radiatior will be a mandatory upgrade for 8s with FI.

Alot will be mandated with this engine and forced induction...

There are carb driven rotaries, and MANY rotaries without ECUs at all. I wasn't trying to peg you as a carb enthusiast (and I didn't mean to sound mean if I did). I was just working on the point that ECUs are slowly getting more intrusive in ALL cars, and cars w/o any ECU are carb driven.

But really, if you buy the car, you buy the ECU. Right now there is no "bolt-on" replacement (that I know of). If the ECU bothers you, don't get the car. That said, I've never had a problem where the ECU doing funny things.

Guys
I have NEVER had a problem with this car overheating even in 100+ days in Georgia! The prefilter air temps I did was just to see how much airflow we where getting through our current factory intake. I also did some engine bay temps because I was concerned about the electronics (i had just installed a cz unit) and was thinking it was getting to hot for the cz unit inside the ecm box. That turned out ok although it did kinda did help explain some of the problems surrounding the burnt coils issue. ( for instance i never let my cooling fan run after I turn the engine off!).
Now, in truth when the weather is a little cooler and the engine has JUST warmed up it does feel a little stronger(not much).
And Shams 42, the 8 is a differant car. Every car has its quirks. Ask the bimmers, ask the z's ask the evo's etc etc . A lot of our talk and stuff is simply because we are all crazy and we try to make whatever it is we are messing with better. Sometimes I think we dont talk enough about the GOOD stuff we have. Hell, Charles Hill is now pulling a 13.3 in the 1/4 with a handfull of mods and a 55 shot of nos!
Its a new car and in 2-3 years it will have a stand alone emu and fi available if someone wants it.
with current mods I think its possible to get well over 250hp.(excluding nos)
olddragger

only power cut i've run into is at 120mph on a low fuel indicator light

I posted this thread the other day, judging by the lack of replies, perhaps I AM the only one experiencing this, but I have the issue below and am concerned if something may be wrong with my 8. This happens at ANY temperature, from recent starts, to when I have been driving all day. Any help in figuring out what is going on would be greatly appreciated...

Sorry of someone posted this before, but I wasn't able to find any other threads with this subject covered.

I was wondering if I am the only one experiencing this issue. When launching the car with a light effort on the gas pedal (which is not that often ;) ) at low RPMs in first gear, I am finding a good amount of hesitation or rather a "dead spot" in the powerband. This tends to happen below 2000 RPMs from a dead stop. Once past that point, all seems to accelerate as I would expect, but this hesitation sometimes feels like the car might stall if I do not get on the gas a bit more.

All of the cars I have had in the past have all been manual transmissions, so it is not a case of me not being able to drive a stick properly. Just interested to know if I am the only one experiencing this, and if not, if anyone out there might be able to help me to understand exactly what is happening mechanically when this occurs.

Dave

... and cars w/o any ECU are carb driven.Not all cars w/o any ECU are carbureted. Mercedes used a Bosch fuel injection unit on the 300SL back in 1954 and Chevrolet used Rochester fuel injection on the Corvette starting in 1957. There have also been MANY fuel injected race cars w/o any ECU at all. It's just that ECU is not practical (or even possible?) on carbureted engines. You can have either carbs or FI w/o ECU, but you can only have FI w/ ECU.
And I'm rather happy that my ECU will try to keep my engine in one piece when things start to get too close to the edge. I've blown up too many engines already. :( I just wish Mazda would use that temp sensor (the one that lets the ECU know the coolant temp) to operate the dash temp gauge!

2rotorz, If you are feeling a hesitation when you launch and/or when you shift to the next gear, it could be a burned coil module. Do a search for "burned coil" 'cuz I learned about this on the forum and there are pictures of what a blistered coil pack looks like. ...Maybe have the dealer test the coils. I also suspect some folks plugs get dirty/fouled, especially before "M" flash was released, so you might check/replace those too. Do a hard-acceleration run to redline once a day - I think this cleans the plugs. Try detergent gas such as Shell 89 or 91+ "V-power" in the tank - cleans plugs.

And maybe you might try reseting your PCM by disconnecting the negative battery cable for a minute. When you reconnect you will have to crank the wheel to the left and then to the right and then maybe shut-off and restart to clear the traction control/DSC lights. You'll have to reprogram your clock and radio too.

Another reset you can try is by turning the key to "on" and then stomping on the brake pedal 25 times in 8 seconds till the oil pressure guage needle sweeps across the face - only shows if you have "L or M" flash. Then start your 8 and drive it a while. It will take a couple drive cycles before the computer relearns what it has to. I've notice engine response to be flat during the first couple drive cycles after this reset, but I could be wrong.

Good luck!

shams42, I don't think the 8 is that fussy with high temps. I've driven my 8 around Las Vegas, in traffic, in the low 100s (with A/C on) and haven't had any cooling issues. I've even been in traffic in "Death Valley" at 112 degrees with no issues. Sure the 8 likes the cooler air (below 70) but all cars and people perform better at cool temps :-) ...Never experienced an ignition retard or power cut-off from high or low temperarture though.

I will be addressing the overall performance with mods - flywheel, pulleys, HF CAT, intake, titanium exhaust, PCM upgrade etc... Till there is a boost solution >:-D

Today at Watkins Glen I had a lack of acceleration at WOT + CEL that I think fits some of the issues brought up in this thread. Do to a number of things falling into place my groups last run of the day was set to be a FULL HOUR! Yes a full hour on the full Watkins Glenn course! I had about ½ tank of fuel and had done 4 ½ hour runs on Sat and 2 ½ hour runs today 2 hours prior to the full hour run. After about a great 45 minutes on the track my 8 felt as if a rev limiter cut in, no power etc and I got a flashing CEL when I was around 8,000 RPM + and under 1/4 tank of fuel. Power did return when I dropped it under 7,000 and the CEL went away about when I went into the pits. Since it was the last run of the day and I had a 6-hour ride home I didn’t wish to take any more chances and did not go back on the track. On the way back the 8 ran fine at highway speed, no CEL’s but I have not gone over 7,000 k since. Did the car just tell me it needed a break? That 45 minutes at track speed was too much? If I burnt a coil would I still have a CEL and would I notice it at normal speeds/RPM’s? I will be dropping it at the dealer Monday but should I get a chance at a full hour on a track again is the 8 to “fragile” to run that long at 7,000+ RPM?

Install a digital coolant gauge. Make a note of what temperature the power falls off at. You might be surprised.

Install a digital coolant gauge. Make a note of what temperature the power falls off at. You might be surprised.

The OEM temp gauge stayed at normal all day. So your saying the temp gauge isn’t really a gauge but more like an idiot light similar to the oil “gauge”?

The stock gauge may not move much, but what temperature is the engine at when the needle is there? That's the point. We don't know. I'm sure it is a functional gauge unlike the oil pressure gauge. I just want to get a corellation as to where power drops off. Jim Mederer from Racing Beat has done alot of testing with the stock ecu. He says that after the car reaches a certain temperature, it backs power down. This temperature does not necessarily mean overheating. I'd like to know what temperature this is at.

Expo1,

The flashing CEL and drop in power could have been a miss fire caused by weak coils or bad spark plugs. It is very easy to check the coils with a multi-meter and it only takes about 30 minutes from start to finish.

I also suggest checking your spark plugs. The electrodes on my leading plugs were worn away until there was almost nothing left. The spark gap was over 0.125", the max is only supposed to be 0.059"!!! :eek:

george your's sounds more like misfire or knock. and its not air temp but engine temp. even on a day in the 80's if you ran the car hard enough the engien could get overheated. also obviously it can be caused by a break down in the cooling system.

charlie, didn't Jim also mention something about fuel pickup in the tank? It is on one side, and going around a curve with low fuel could actually cut off supply due to this? What side was it?

he did but i dont remember which side. a low fuel situation like you describe could cause an excessive lean situation.

There are 2 fuel pickup points in the tank. One on each side. Each has it's own dedicated pump.

Regardless, you are still able to get the engine to starve for fuel with 1/3 of a tank of gas by blasting through a long high G corner. I've run into this problem myself and have since tried to keep the car above 1/3 of a tank when I'm out on the track.

One of my co-workers, who has raced for years, said that this is a common problem in racing but he also mentioned that it is pretty easy to fix. In the past he has created a baffle with a one-way door and placed it around the fuel pick up. When the car is level fuel flows through the door and fills the resevoir. When the car is under load the door closes and keeps the fuel from sloshing to the far side of the tank. Problem solved. :)

Regardless, you are still able to get the engine to starve for fuel with 1/3 of a tank of gas by blasting through a long high G corner.

I wasn't saying that it can't get starved for fuel. I was just addressing the statement that the pickup is only on one side of the tank. It isn't.

Regardless, you are still able to get the engine to starve for fuel with 1/3 of a tank of gas by blasting through a long high G corner. I've run into this problem myself and have since tried to keep the car above 1/3 of a tank when I'm out on the track.



Mine cut out on the back straight when I hit about 8,000 RPM in 4th.As I said in my post I was about 1/4 tank so I am hopeful that fuel starvation was the cause, I should find out by tomorrow.

I wasn't saying that it can't get starved for fuel. I was just addressing the statement that the pickup is only on one side of the tank. It isn't.

Sorry, my bad. ;)

...I had a lack of acceleration at WOT + CEL...
...I had about ½ tank of fuel
...the 8 felt as if a rev limiter cut in, no power etc and I got a flashing CEL when I was around 8,000 RPM + and under 1/4 tank of fuel.
...Power did return when I dropped it under 7,000 and the CEL went away about when I went into the pits.



VERY similar to my sistuation last Saturday. My car had just under 1/2 take of fuel on the gauge. I was in a fast sweeper, left-hander. As I was exiting the turn, I went WOT and the car sputtered and coughed and had NO Power. As the tach dropped below about 6k? I got on the gas again. A second later the car coughed and sputtered again. Then - the flashing CEL. I hit the pits. I disconnected the battery for a few minutes, and re-started the car. No CEL but my DSC OFF was flashing, AND my 'TCS Warning' (center of tach) was illuminated. I drove off to fuel up, as I remembered reading this thread. After I fueled the car, there was no change to the DSC flashing, and the TCS was still illuminated. Driving about 1/2 mile, I shut the engine off, then pop-clutch restart. The DSC stopped flashing, and went out, but the TCS warning was still illuminated. One more pop-clutch start and both were off. I pressed the DSC and the light came on normally. I tried the 7-second and things looked right.

With a full tank, I took the car back out for one last (and by far my fastest) session of the day with no noted problems (save for tire and brake fade :) ).

DMP you have to sweep your steering wheel back and forth after a battery discon. to recalibrate the DSC.

DMP you have to sweep your steering wheel back and forth after a battery discon. to recalibrate the DSC.


Oh...weird. Never heard of that before...hasnt happened before. :)

Thanks! :)

Sure. No prob. It is in the manual somewhere. I think if you look up DSC in the index you will find it.

I posted this thread the other day, judging by the lack of replies, perhaps I AM the only one experiencing this, but I have the issue below and am concerned if something may be wrong with my 8. This happens at ANY temperature, from recent starts, to when I have been driving all day. Any help in figuring out what is going on would be greatly appreciated...

You are not alone. This is particularly obvious if a blip of the throttle is done.