Ok I have a question and if this has been addressed tell me to search again because I haven't found it. My question is, why does my car run better on hot days (90+) as opposed to cooler and cold days? It starts better and has noticeably more response and power. Most things I have read have said they tend to start worse on warm days. I only ask because I am trying to get this kind of performance all the time. Thanks for reading.

 

Can you go into more detail?

If you're talking about your engine running better when warm, its because you aren't supposed to drive the engine hard before it reaches operating temps (180+ degrees)...

 

The problem with the rotary engine is whenever it reaches 100+ degrees (specially in Las Vegas), the car idles like it's about to die and the engine stalls. It happened to mine a few times now, and i needed a tune-up and getting my fuel pump replaced. If that doesn't solve the problem, then i might get a compression test. Anyway, i hope those things will help with the problem with the car when driving in excessive heat and i hope i don't need to do a compression test.

 

My question isn't because the car runs bad or has a problem starting. Simply why does it run and start better on hot days(95+) and is there anything I can do to make it run this good on not so hot days? I've recently replaced the coils, plugs, and wires (a month ago). In cool or cold weather the car will start fine it just takes a few seconds. During the last few days of hot weather it has started almost immediately after the key is turned. I usually let it idle until the gage is halfway then drive it 10 or 15 minutes before revving over 4000ish. As far as more description I don't have any hard numbers but the car simply feels more responsive and definitly has more power. I haven't had any problems with it failing to start or idle problems. I apologize if I'm not being completely clear it just seems to go against conventional thinking.

 

Just because your car does this doesn't mean it is generally a "problem with the rotary engine". A renesis with proper compression and ignition should not have running quality problems in hot weather. Mine LOVES hot weather....

 

You might try cleaning the MAF sensor. If dirty, it can give a false air temperature signal.

 

I'll give that^ a shot i cleaned it once but maybe I didn't clean it very good. Thanks for the advice

 

Fixed. Most of us don't have that problem.

There are corrections built into the PCM programming for temperature.
It is possible that, since every RX-8 behaves differently on the factory programming, your particular engine runs very lean. In warmer weather, this will result in better response and output.

Engine management tuning.

 

This thread puzzles me greatly. All the cars I've driven runs significantly stronger in colder weather.
I always thought colder air meant denser charge. Denser charge means more fuel can be mixed with it and converted into energy. I feel like I'm missing a crucial detail.

I understand that it starts better and has better response, but more power (once it's warmed up)?

 

If the car already runs too lean, the additional air mass during cold operation will only exacerbate the situation.

 

Ah~ gotcha. Thanks.

 

Thanks for clearing that up

 

Gee, I have always found my 8 runs better in cooler weather with high cold humidity or high moisture content in the air, around 22-25 (65-75 F) is perfect for mine.

 

Yeah, that is fairly typical, though some run their best when it is closer to freezing.

 

Maybe its simply something like a sensor for the air temp or the coolant temp that is giving bad readings to the ECU when its colder than 90 degrees on this particular car.

Might it be cheap and worth it to swap one of both sensors to see if the cold start problem then goes away?

BC.

 

That makes sense. Maybe if the problem gets worse that is the first thing I'll do. Thanks for all the input guys, it's really enlightening

 

Like mine. Runs it's absolute best around 25F (well, on stock tune, have MM tune for this next winter so it may change) But then, I've always run too rich on the stock tune, and the reverse of the hot temp issue making lean conditions better makes sense

Unfortunate that it means that my best power is when I have the worst traction

 

running better? I'm not sure exactly how you mean. But...

over the winter I averaged 18mpg, but had "more power" (colder/denser air requires more fuel, obviously)

I just filled it up today, where temperatures have been over 100 (las vegas ftw), and got 20.9 mpg. It idles the same, and runs the same (though feels slightly less "powerful").

 

My car has felt much less...powerful since we started getting these consistent hot spells. It's been 92+ here every day for a week, but I do notice, at night, when it's around 70 or 72, the car pulls considerably harder.
It appears that I've finally gotten rid of my misfire too. Damn throttle body was gunked up like crazy.