Last post on Jul 25, 2003 at 6:41 AM
You are in the Maintenance & Repair - Archived Discussions
This discussion is ARCHIVED. To reactivate the discussion, post a request in the Lost? Ask the M&R Host for directions! discussion.
What is this discussion about?
Honda, Engine, Fuel System, Fuel Efficiency (MPG)
Jul 17, 2003 (9:01 am)
How about turning off your CAPS LOCK key? It's the internet equivalent of shouting and it makes posts harder to read.
#3 of 11 Just his heading was in caps...
Jul 17, 2003 (9:21 am)
Not the entire message. I don't see what the problem is.
Jul 18, 2003 (8:32 am)
The original post was all caps. Looks like the gentleman was kind enough to edit and repost in lower case.
#5 of 11 Then I must have missed the original post**
Jul 18, 2003 (9:38 am)
Jul 18, 2003 (5:12 pm)
I think your problem might be more related to two other "power-robbers" in combination in your area--high altitude and VERY warm air. This is why, at some high altitude airports, they will actually take some passengers off a plane to lighten it, during extremely hot weather.
#7 of 11 Power-robbing vs fuel economy
Jul 20, 2003 (8:57 am)
OK, this stuff always blows my mind when I think about it: My experience on flatlands generally is that I get my best gas mileage in summer, except of course when running the A/C. That usually drains about 3-4 MPG. Of course, in the mountains the air thins even more, but this is a similar effect to summertime air in that it's less dense, just to a greater degree. BUT...fuel economy and power are not always proportional. Whether you use a carburetor or FI, both systems compensate fuel metering to match air density. So, if you drive a car on flatlands, then drive at a higher elevation with the accelerator in the same position, you would notice a lack of power. But you would also use less fuel. Increase pedal position to match your flatland speed, and your throttle plate would open to pass the same air mass/time as on flatland, and your fuel metering would increase to match. This is theoretical, of course, and actual mountain driving requires much more fuel because of the hills, but I believe the original poster's location was a constant anyway.
My guess is the biggest problems with his summertime fuel economy are the reformulated gas (they use that in AZ?) and his use of A/C, which a lot of folks forget to consider. An A/C compressor really sucks power.
Jul 20, 2003 (7:40 pm)
I heard out in AZ, temps are close to 100's everyday in the summer. with the a/c on full blast, that's sure to rob you 3-4 mpg
Jul 21, 2003 (5:02 am)
Arizona gets its bulk gasoline from California refiners. Look to the recent changes in mix....phase out of MTBE......are they substituting Ethanol in the blend yet?
The air loses density 1% per 333 feet AMSL and 1% per 11F these are additive vs 32F and SL......at 5,000 feet engine power is down 15%........in 110F engine power is only down 5% from SAE rated 60F.
However most/all ecu have a summer protective mode where the coolant temp is monitored and the AC ON signal is considered........ignition timing is reduced and fuel is enrichened [to cool cylinders] to protect the engine above 195F coolant sensor reading.......this has at most a 10% effect.......but may be additive to air temperature.
Each manufacturer is different as to how exactly they attack these problems.
Jul 21, 2003 (2:26 pm)
<<However most/all ecu have a summer protective mode where the coolant temp is monitored and the AC ON signal is considered........ignition timing is reduced and fuel is enrichened [to cool cylinders] to protect the engine above 195F coolant sensor reading.......this has at most a 10% effect.......but may be additive to air temperature.>>
Wow. So I guess in a very slight way a FI engine could actually use more fuel than a carbed engine in extreme heat? Of course, it's nice not having to listen to that carbed engine ping itself to death, huh?
Jul 25, 2003 (6:41 am)
People sure have a lot to say re: this whole topic and some of it very technical. I will say this, however, that in Arizona we have to use our a/c a lot even throughout the rest of the year. I normally can get about 28-29 mpg in my Honda Civic auto most of the year with a/c use but when summertime hits they have that mtbe reformulated gas that is 15% mtbe and the mileage drops to 23-25 which is substantial. I have noticed this on all cars, however Hondas seem to be more sensitive. Yes in Arizona in the summertime starting usually around mid May to Early June the temps are usually over 105 and this summer they have been over 110 and a lot of days over 115 but it seems that the gas is the main problem since I use the a/c at other times of the year with the other gas. Why do they put this gas in affect does it decrease emmissions or help the car run better in extreme heat?