zoom44

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

zoom44

shelleys_man_06

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

rotarygod

It was pretty neat watching Jim play with the ecu bench. He'd hold it at one rpm and then turn a **** 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.

Xyntax

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!

zoom44

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.

Xyntax

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.

rotarygod

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.

rotarygod

How about installing an aftermarket digital water temp gauge.

RX-Nut

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

Mugatu

iTrader: (1)

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.

sco

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?

rotarygod

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

MadDog

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

rotarygod

Damn near self aware!

Mr M

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.

rotarygod

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.

shelleys_man_06

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

bgreene

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

GeorgeH

iTrader: (2)

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.

zoom44

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.

rotarygod

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.

olddragger

iTrader: (3)

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

Razz1

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?

rotarygod

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.