Consumption at idle
 

I had to try a Renault Twingo during one day [1] :

• diesel 1.461L 65hp
• manual 5sp
• 3 doors
• rated 45.2 (city) 61.9 (highway) 54.7 (combined)
• CO2 113 g/km.

I plugged my SG2, which is incompatible with my 2 older Renault, and it was nearly fully compatible. It was missing TPS so the SG2 didn't had the open/closed loop information...

As I didn't know the cubic capacity when I plugged the SG2, I configured 1.6L, so the following figures are what I remember multiplied by 1.461/1.6.

I didn't had time this day so I have only been able to test the information I do not have in my scenic : the instantaneous consumption at speeds under 35km/h (21mph).

When the engine was started, the consumption at idle was at 1.65L/h (0.43gph). Ten seconds after it was down to 0.9L/h (0.24gph). After 1/4h of stop&go traffic, the consumption at idle stabilized at 0.73L/h (0.19gph).

Another thing I wanted to know is how much consumption the car has when you drive in 1st/2nd gear with the engine at idle (ie you doesn't touch any pedal). The results were :

gear	L/100	km/h	mpg	mph
1st	18	8	12.9	5
2nd	9	15	25.8	9

At these speeds, coasting in neutral would consume at 0.73L/h (0.19gph) :

km/h	L/100	mph	mpg
8	9	5	26
15	5	9	48

The conclusion is that at low speeds it's certainly better to pulse 'n coast in neutral than keeping the engine in gear at idle rpm.

[1] the megane had a leak near the water pump, the thermostat melted in part and the temperature gauge was shifted down. As I didn't drive this car since months I though the low temperature shown by the gauge was because of near freezing temperatures and short commutes (20 miles). I worried when i saw the gauge going up & down... I had then not enough water in the cooling system. Happily it wasn't the water pump, but the water tank and a pipe.
Even without front grill (removed because this problem) and heating system at full load (in the hope to remove as much heat from under the hood) I achieved 43mpg, only 10% under my summer tanks :)

Denis.

Good find!

Must be nice. Mine is in the range of .69gph at idle. Which I think is the main reason most SUV's get junk for gas mileage.

In the few minutes my MPGuino was working yesterday, even not-quite-calibrated, I noticed that with the car not moving at idle it would consume less gas in neutral than drive. (.43 gph in drive, .35 gph in neutral)

I have a 98 vw new beetle 2.0L gas 4cyl. it is around 0.28gph at idle which is 810rpm ish.

groar -

Cool! I love the first-gen Twingo design. The cute name totally fits the car's looks. Wow, 65HP is only 5 more HP than my Dad's 1971 Karmann Ghia.

My 1.9L engine shows about 0.3 GPH at idle (under 1000 RPM).

CarloSW2

My Civic' 03 1.7L fully warmed shows 0.2 GPH at 750 RPM.

i get .35 in my 98 taco(2.7l) at 650-700 rpm (when warmed)

it would blow my mind to see .1gph

My Tacoma gets the same. (As it should.) Though when I coast in neutral on the highway, I get .44 sometimes. Maybe all the time... I need to check more often. Does yours do that? Why would that happen?

akashic -

Is the idle RPM also higher? My "idle RPM in neutral" will be higher at freeway speeds. I think it is something the ECU/PCM does.

CarloSW2

Yea I get .45gph at coast even with my 5 speed.

a

I don't have the gph display, only the mpg and mph so I can easily calculate it. What I remarked is that the mpg display decreases more or less quickly depending on the temperatures, but also the consumption when I change to neutral. If I was accelerating quickly then it takes a lot of time to decrease to the stable idle consumption.

Now when I put in neutral while I was in engine break (DFCO) then the consumption increases to the stable idle consumption. I'm wondering if the strategy can save gas, but I doubt about it as you have to accelerate to a greater speed and loose noticeable speed during the 2 seconds of engine break needed to reach DFCO.

Denis.

Crazy analysis Denis, thanks a lot ;)

Should get a SG2 someday for my hyundai, or maybe i should just locate the OBDII port before.
Weird the 97 and 01 Renault don't work with it... by the way, what was them problem with that ?

Wanted to know such data since a long time as my iMPG (instantaneous) display in scenic doesn't show any value under 35km/h (22mph) and I'm often blocked in (very) slow traffic.

From ScanTool.net LLC - Powered By Kayako eSupport I found this : OBD Clearinghouse

The looong story : http://ecomodder.com/forum/showthrea...ault-4527.html

My cars are European so EOBD (European name for OBD2) is mandatory for gasoline since 2001 and for diesel since 2004. Both my cars are diesel.

Denis.