>diesel, you get only 2 times larger consumption between mild and hard acceleration.
with gas engine, it raises 5, 8 or even 10 times more. that's what makes it uneconomical.

Which means that it's even more crucial to accelerate gently in a gas engined car - if you bring the fuel consumption on hard acceleration down to 6mpg, the improvement over the 1km with gentle acceleration is a whopping 87.5%.

I am well aware of the characteristics of gas engines, both petrol and LPG - I used to own a Nissan Micra with an LPG conversion - small engine, 16 valve, non turbo and high revving - if I used it reasonably hard on LPG, my average fuel consumption could easily be 20 - 25 mpg, used gently it was around 35mpg.

 

well, I can't tell you in mpg-s, but I will tell you in litres per km.

cruising around with 60 kmh I have around 5,8 or 6 l/100 km. it's hard to tell becouse I don't have cruise control on renault SUV.

now, if I press the pedal very, very, very, very gently, I can accelerate very slowly, but keeping the consuption below 10 litres/100km.
if I press any harder (and that happens every other time, difference is too small), it goes up to about 15, 18 or 20l/100. car accelerates better, but still too slow. consumption is high (brake specific fuel consumption is high in those low revs) and acceleration is poor.
and if I press firmly, consuption will not get above 22-25 l/100km. even WOT will not bring it to more then 28l/100km. it can't becouse ECU will not allow it, engine can not inhale enough air to raise the consumption to more then that.

it is pretty obvious that firm acceleration (not WOT) will shorten the time of large consumption and extend the time of low consumption. the diffrence between mild and hard acceleration in litres per 100 km is too small, it is almost allways high, around 20l/100 km. all gas engines take a lot of fuel on acceleration and it is simply not worthed to accelerate lumpy, unless you can keep your mixture in stochiometric all the time.

 

and then, my voyager has cruise control.
so, crusing at about 80 kmh keeps it on 8 l/100 km.

if I press steering acc. button once, that will accelerate the car for 3 kmh.
it will also bring the consumption to 11 l/100 km for a while, untill the car reaches 83 kmh.
any movement on acc pedal will bring the consumption to 25, 30 or even 45 l/100 km. again, difference in liters consumed between mild and hard acceleration is too small (not through cruise control, but with the pedal).
every time I tested the car, it is allways better to accelerate firmly and gain normal cruising speed as soon as possible. also becouse the difference between acceleration (say, 30l/100km) and criuse (8l/100km) is far greater then with diesel engine.

also on start up.
normal start from stand still will consume 35 or 40 litres per 100km (or 70-75 with WOT). in 1st and 2nd gear that goes very fast (timewise).
but in 3rd gear, if you don't press firmly, it will take forever to reach revs for 4th, and all that time the engine will take a lot of gas.
4th to 5th, same thing.

not worthed.

 

I think that's exactly my problem. The auto box won't shift into higher gear like I would have when I drive a manual. Because I do a lot of town driving, at 30mph I am stuck in 3rd gear most of the time. Even though I know the engine has enough torque to push me along in 4th at 30mph (in 5th even when I had my Alfa 147), the auto box just won't upshift...

...Which is the reason for the first thread. Would that contraption, giving my engine even more torque, make it shift to 4th earlier and hence reduce consumption? I think that's what the sellers are claiming as well.

FYI I resetted the mpg counter and I am on around 13L/100km in town. :.-( But that's still better then the loan PT Cruiser 2.4L Petrol I am having at the moment. 20mpg on the motorway...

 

wooow
only now I saw that your car is diesel. so, appologies to actd, my advice does not fully apply to 2doctors. but the rest stays.

why do you have to shift 4th?
you can still drive in the 3rd gear and have the same fuel consumption, you just have to be a little slower.
you get me?
you consume 10l/100km in 4th, the speed is 60 kmh.
you can consume the same 10l/100 km in 3rd gear, you just have to drive 50 or 55 kmph.
the main thing for you is to use cruise control as much as possible, even in city driving.

my voyager is 2,4 gasoline, and I can make 13l/100 km of LPG in the city driving like I explained.
alfa has a different transmission, it's not to be compared with T&C.

for your car, even if you install this gizmo, I don't think it'll make any difference. those revs are too low (30 mph in 4th gear) and whatever it does, it's simply not enough becouse on those revs the turbo is not filling the engine with sufficiant air. no turbo - no fun (or no torque).
and one other thing.
in that techincal document, they explained how gas and diesel engines work. but they didn't explain what is that device doing, except injecting more fuel.

 

Hmm nice suggestions guys..very helpful information thanks a lot..having same problem..but now hoping for good this info will clear all my doubts..

Thanks

Diesel tuning