2002 Honda Fit acceleration issues

[culzean]

Could the humidity in the air have anything to do with it?  Or did the rain somehow get anywhere?  Colder air temperatures?  I'm in a fairly humid environment (humidity levels increase significanly when the sun is down) and at the moment temperatures during a day will range from 9C to 16C.
It all seems far fetched to me though....

It's always been known since the invention of the combustion engine that they run a little better with humid air, although the exact reason escapes me. In fact I believe there was some device brought out which injected a little moisture into the air intake many years ago. Perhaps there is a scientific reason, but always remember mechanics telling me this in days gone by.
Mike.

Anyone who has ever had a 2 stroke motorbike knows they run much better in humid conditions as the water in the air makes the charge more dense and flashes to steam when charge is ignited.  There was even talk of 'water injection' (in aerosol form,  not a hose pipe) in IC engines to improve efficiency.  when car makers are testing their cars on rolling roads they carefully ensured that the humidity and temperature in the 'laboratory' was right for maximum benefit (they also disconnected aircon, alternator and any other load on the engine) - and they never thought it was 'cheating'.

http://spectrum.ieee.org/cars-that-think/transportation/efficiency/squirts-of-water-can-boost-engine-performance-fuel-economy-by-13

the linked article suggests that some of the fuel is used to cool the engine rather than produce power,  so if you can cool the engine combustion with water it can increase power and improve mpg.

[Jocko]

Water is H₂0, both of which are the ingredients of combustion. I believe it increases the density of the charge. It also helps to cool the charge by latent heat of evaporation and the power from a given "combustion" is dependant on the change of temperature as it burns. Therefore the colder the mixture is before the ignition starts the greater the change when it reaches combustion temperature. If I remember my Ricardo correctly.

[MikeG1944]

Thanks Jocko; That makes sense. I thought there must be some scientific explanation. 

[ansys]

hmm. good stuff on all the combustion theory!

a couple other things I've tried to take a look at so far with my OBDII reader (using the Torque Light app)...
tried to watch the readings for the O2 sensor, and they seem alright.  The graph display shows the reading fluctuating between -0.1 to 0.7V or so, but the dial indicator shows it between 0.1V - 0.8V.  I imagine the graph reading negative might be a problem with the app??  Also, when the engine is being revved, the frequency of the signal wave seems correct.  At idle it is quite slow, but I assume that's not an issue.

Those readings were on O2 sensor 1 bank 1.  All other O2 sensors/banks were not giving any signal.  I was a little surprised because I thought there would be an O2 sensor after the catalytic converter, but the OBDII wasn't picking it up.  I had a very quick look under the car to see if I could see the sensor, but I couldn't find one... do early JDM fits only have the one O2 sensor?  Admittedly my search for the 2nd one was pretty brief.


I checked the vacuum readings the OBDII was giving back, and everything checked out normal as per these references:
http://www.gregsengine.com/using-a-vacuum-gauge.html
http://www.onallcylinders.com/2015/05/08/quick-tech-how-to-read-a-vacuum-gauge-to-pinpoint-engine-problems/


any suggestions on what to investigate or pursue next???  Car runs pretty well when the sun is down, but when the sun is up it give some hesitation/stutter issues. 

Thanks again for all the help so far!

[Jocko]

There are two heater Lambda (O₂)sensors on the exhaust. One ahead of the catalytic converter and one downstream from it. Shown here at either end of the cat.