Fuel consumption - what are you getting

Christopher

Christopher

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hi folks - interested to know what kind of fuel consumption you get out of your coupe - particularly if it's injected. i reckon i'm getting about 12 mpg at the moment which is worse than ever - i''ve just had all my valve clearances redone, new plugs, points and injectors redone but it seems to have got worse. also what rpm do you idle at when warm ?

any tips on how to get better fuel consumption much appreciated

thanks
 
consumption

Christopher,

where abouts in London are you? My car idles at 800rpm. I get about 15 around town although I dont use it like that much. Are you in stop go traffic?

12 is low enough.

Regards,

Rohan
 
People check the fuel economy on e9's? :o :lol:

I honestly have no clue. My daily driver e12 mit warmed/chipped Motronic 3.5 gets 18-ish on my city street commute, and anywhere between 15 and 25 on the highway depending on the weight of the right foot that day.
 
My coupe runs a 3.5 with L-jetronic idles at 750 rpm and the last time I checked I got 24mpg on a gentle (mother-in-law in the back) cross country run, probably could do a little better on the motorway.
12mpg seems a little low, have you checked the CO content? you're running injection but don't say what type if it's D-jet check the vacuum pipe running from the manifold to the map (vacuum) sensor make sure it's not split and that the pipe is tight on its fittings. Also check the fuel pressure, the pressure regulators can seize up, not sure of exact figures but early L-jet runs at 2-2.2 bar which is 29-32 psi. An easy way to check if the regulator is working (could still be out of spec though) is to pull the vac pipe of the fuel pressure regulator with the engine running if the car runs worse (starts to hunt) the regulator isn't seized but I'd still get the pressure checked.
Another possibility is the coolant temperature sensor (for the ecu not the temp guage) connecting an ohm meter across the terminals should give a reading of 2500 ohms approx.
Good luck
 
thanks for the advice gazzol - i'm running d-jet - any idea on the pressure for that system ? - i'll get it checked out.

what kind of co2 reading should i be getting ?

rohan - i'm in notting hill west london
 
Hi Guys,

I tend to get between 20 and 22 mpg from my D-Jet CSL - no heavy traffic but I do tend to drive it farily hard.

It took me an age to get the fuel consuption and general running right but with tinkering (mainly with the timing) I got it from single figures to what it is now. It is still not spot on though but I'll live with it for now.

Another E9 in London. That's 5 to my knowledge and that's not including Rohan (if you are still based in Herts - sorry if I have got that wrong.)

Paul

SE London
 
Christopher said:
thanks for the advice gazzol - i'm running d-jet - any idea on the pressure for that system ? - i'll get it checked out.

what kind of co2 reading should i be getting ?

rohan - i'm in notting hill west london
Click to expand...

From memory it's about the same, I do have a set of bmw blue books in the loft I'll have to dig them out.
It's not the co2 reading that you're interested in it's the co (carbon monoxide) you should be looking for a figure of arround 1-1.5% at idle, however it's not the idle that is too important it's the running figure that we're more concerned with. To check what the car is doing under load involves either a rolling road or a portable co meter which you can sit on the passenger seat while you drive along. Again unfortunetly I'm not sure what the reading should be while you are cruising what I can tell you is that it is negligable i.e. normally lower than the idle figure, this will obviously rise as the car speeds up and will be at its highest under full acceleration regardless of the engine speed.
If you can't get to a rolling road ( finding one isn't too hard but finding an operator/ tuner who knows what he's doing is) try this, with the engine fully warmed up and the car coupled up to a emmissions analizer take the engine speed up using the throttle and then hold it there, it doesn't really matter too much what speed but 2-3K rpm should do, the co reading should drop to arround 0.25- 0.5% sometimes even less.

Before you do any of this though get the fuel pressure and coolant temp sensor checked. Aim for arround 30ish psi. If I get time I'll dig those books out from the loft.

Regards
 
Running 32/36's I would be in the 14-16 MPG range. The driving would be considered light comprising weekend runs with a bit of high speed freeway runs.

Running the new 3.5 L FI I was able to get 23-26 MPG driving from La Jolla Independent to SF haulin ass on highway 5.

Shawn
 
thanks for the advice gazzol - going to get the once over on everything this weekend - if go the specs from the blue book so here's hoping i can lighten the burden on my wallet once and for all !
 
Ok just went up into the loft and brought the blue books down. Fuel pressure should be 2 bar with vac pipe connected and 2.5 bar without vac pipe.. don't forget to check the vac pipe to the regulator for splits/leaks aswell as the map sensor pipe any leaky pipes will make a huge difference.
Let me know how you get on

regards

gazzol
 
Gas Mileage

Remember that UK, Aus and Canada all use Imperial (4.54 litre) vs US (3.8litre) gallons so the mileage should be about 17% different all other factors being equal.
 
Co should be around 2 - 3% for smooth running

Check the colour of your spark plugs too, a very good indicator of running conditions:

White / glazed - mixture too weak
sand / light brown - correct
black / sooty - too rich
black / wet with petrol - high tension ignition faults, bad plug, injector dumping too much fuel
black / oily - rings, valve stem seals

Look at the plugs after driving and the engine has been up to temperature

be aware that if the plugs are too "cold" ie they transfer heat away too quickly then the car will appear to be running too rich. "hot" plugs are the opposite.

HTH
Malc
 
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