SuperMid users--how much gas at idle?
 

i'd particularly like to know for da VX but anyone who wants to do a little espermint. See what your MPG is at 40mph or 50mph in Neutral with the engine idling.

Any VX owners have a supermid and can tell me what the mpg is? I wanna know how much gas to a tank roughly is being used while engine on coasting and sitting at traffic lights.

When I am idling down the HW, my SuperMid indicates about 1/100 of a liter every 10 sec, if there are no lights or radiator fan running.

The SuperMid always shows 99 km/L under these conditions... even at much slower speeds (makes sense since it is barely sipping any gas at idle)

Do you think it uses less gas to do engine off coasting?

That converts to roughly 1/65th of a gallon every minute.

The amount of time I probably EOC every 60 miles is about 5 minutes I think. Not this tank, but that's about the upper potential based on my most common route and driving style. So on a 500 mile tank that's about 42 minutes that otherwise would be engine idling. Wow, that actually is somewhat significant amount of gas saved. .65 gallons. but then you have to figure FE lost to o2 sensor getting cool from engine being off and lean-burn taking longer to kick back in once engine back on. (So I've been told)

If there is no penalty for turning the engine back on after EOC, then based on my calculations it equates to a 5mpg increase from 58 to 63 to do EOC. My idle is probably using more fuel than yours since I have a surging idle.

Calculations assuming you are going 60mph idling on the highway.

Does this have anything to do with when the green shift arrow comes on? I've been wondering if my ECU is the culprit for my wonky green shift arrow coming on at sometimes slightly random times.

I'm pretty sure the upshift indicator and lean-burn are rather separate.

this taken from an article on P&G from metrompg.com

"the average mpg shown on the ScanGauge in the glide down from 90-70 km/h was 550 mpg"

Now consider the average speed was prolly around 75km/h because more time is spent at slower speeds than higher speeds during glides. 75km/h equals about 47mph. So 47mph in neutral equates to 550mpg in a MetroXFI.

This equates to just over 700mpg at 60mph. Or 11.7mpg at 1mph. Which is 11.7hpg (hours of idling per gallon). This equates to 0.06 gallons or 3.65 ounces of gas saved for every 42 minutes with the engine off. Which is a huge discrepancy from the VX. Which makes me wonder where I did my math wrong. VX should be 0.065 not 0.65? hmm....

Let's go through it step by step. 1/100th=0.01 liters every 10 seconds which is 0.06 liters every minute which is 2.52 liters every 42 minutes which we divide by 3.8 to convert to gallons and get 0.66 gallons every 42 minutes. No way the VX is using ten times as much gas as the MetroXFI at idle. So either the guy who did the Metro P&G test scangauge is wrong or Ica13's scangauge is wrong. Something's wrong somewhere.

To throw some perspective on this issue. My dad's 3.8 liter Town & Country drops below 99mpg at about 48mph when in neutral. It seems possible, then, that the XFI with a 1.0 liter engine uses about 5.5 times less gas in neutral. This is all assuming the metrompg guy from the P&G article was accurate with his assertion of an average of 550mpg from 90-70kmh.

The second half what you say here Ica13 makes sense but the first half isn't corroborating to my math!

Ugh, what am I doing wrong. 99km/L quals roughly 60miles per 1/4 gallon which equals 240 miles per gallon. Now this seems to make sense that it would not drop below 240mpg even at slower speeds. So how am I doing my math wrong?

I thought all the math geeks stayed home on Friday night. (?) heh

Well, until someone else weighs in on this issue I'm gonna give it a rest. I think the VX should be using about 0.1 gallons of gas per hour of idling. Maybe a titch more. But certainly not the .9 gallons an hour or .65 gallons per 42 minutes I was coming up with before. More like 0.09 (just under a 1/10th of a gallon) per 42 minutes.

you know what..... my mistake.... it's 1/1000, not 1/100..... three digits of precision on the SuperMid, not two.

As for Km/L, there are only 2 digits of precision, so 99 is the best I can see.

Good catch, dude. Continually proves my memory isn't what it should be (Need to go look again the today.... maybe I'll run a few idle scenarios and report back)