When the ambient temperature is above 100f, the A/C has to work very hard to cool it off. Yes a compressor works at normal idle, but not as efficiently as slightly higher than idle (example 2000rpm), especially when the inside of the vehicle can be well over 130f!

Of course, protecting the battery is Ford's #1 concern on this system (They don't want to warranty these any more than they absolutely have to.. and I don't really blame them) so they want to cool it off as quickly as possible.. even if fuel economy takes a hit in the process.

 

Not sure.....

Think of it this way, with most cars the A/C MUST provide FULL cabin cooling capability even with the engine at or near idle. That means that the A/C compressor must have a relatively large displacement capacity.

Now put in a CVT, especially an Toyota HSD CVT, and those rules change. The engine no longer needs to remain at idle in order for the car to remain stationary and engine RPM no longer must directly correlate to gearbox ratio/roadspeed.

So the HSD can have a small A/C compressor to the advantage of improved FE.

Many newer cars today have more COMPLEX variable displacement A/C compressors using the "swash plate" technique. Think helicopter blade "tilt", attack angle as a function of rotational position. Your FEH/MMH has the same capability, but with even lower weight/friction, low pumping loss, but without the swash plate complexity.

 

Wwest, I'm not sure I see the point of using the Toyota HSD in your example, since it uses an electric A/C pump, completely different from the belt driven A/C in the FEH.

-J

 

It is a pretty serious hit. My mileage was down to 24.5 while the engine was at "high RPM". The thing I really don't understand is why it happened at highway speed. At highway speed the compressor is always on, and 1700 RPM (on the downhill) should be enough to cool. Not to mention the uphills at 2600 or so...

I have managed to get my MPG back up to 31.6 these past two days...

 

Your FEH/MMH does that, "real time" supplying of liquid refrigerant, via varying the ICE speed while using the CVT to hold the roadspeed to the desired level. Most other, non-CVT, cars are now using the variable displacement A/C compressor.

 

I notice no difference in mileage with my AC on. Its not normal.

 

We think it only happens when the outside temp is over 100 degrees. Is that true in your case?

 

I remember early owners (2005 -2006) complaining that the AC was anemic whem the temp was over 100 degrees F. I think this problem was solved in the 2008 version of the FEH MMH by ramping up the rpm's at idle. Remember, the 2005 is slightly different in the was it drives and in the "odd" behavior that hybrid cars can do. 2006 and 2007 are about the same in their behavior, but the 2008 was "refined" to go in and out of EV more seamless. I am sure their are other behaviors (can't find a better word) that the 2008 does.

Example of "behaviors" are when it is below 20 degrees F, the FEH and MMH will run @ 2500 rpm. Happens all of the time when it's really cold out side. The engine is hot, but the idle is fast. Same with the car turning off when the defrost is on and the temp is really low. Normally the car will just keep running when defrost is on, but when it's really cold, the engine will shut off at a stop light.

Lastly, you need to know that there is no "normal" rpm for this car. It will have different rpm's depending on the temperature, the battery charge state, and probably 10,000 different situations.

 

I dont get a chance to drive the FEH since its wifes, but when I have, noticed the rpm is around 2000 also.
Another ?, would it be possible to find a electric motor that could be fabricated with separate belt so it would run A/C only?

 

Why not just buy the compressor/motor/AC drive assembly from the Prius...??