Fuel consumption when tuned

forkinthroat · Post by **forkinthroat** » Tue Nov 04, 2003 2:34 pm

hi

my question is to all the people who have mods regarding more turbo pressure, bigger turbo and chip tuning.
has the fuel consumption increased? regarding the same kind of driving.

martinholmesuk · Post by **martinholmesuk** » Wed Nov 05, 2003 10:57 pm

I would think so

dragon · Post by **dragon** » Wed Nov 05, 2003 10:59 pm

I'd say so, especially with changed turbos as they often go hand in hand with bigger injectors and remapping to get more fuel through...

MatBat · Post by **MatBat** » Wed Nov 05, 2003 11:44 pm

More fuel = More power, thus
A more powerful car must use more fuel

Well one would assume.

Though saying that, a guy I know claims to get 30+ Mpg from his
3.2L Porsche 911

Ortovox · Post by **Ortovox** » Sat Nov 08, 2003 12:58 am

If you don't drive more aggressive after the tuning the car then:
-Generally chiptuning should lower your fuel consumption because a real chiptuning chip has got more optimised (ignition/fuel)settings than the fail safe original chip.
-The higher turbo pressure shouldn't make any difference as long as you dont use it

.

But with a tuned car you will probably use the extra HP and then the fuelconsumption will increase for sure. And with more serious engine tuning than (chip/higher turbo boost) the fuel consumption will probably also increase.

As an Example, my parents volvo 940 turbo is chiptuned from 165hp to about 210hp and when crusing on highways the fuel consumption is better than with the original chip.

forkinthroat · Post by **forkinthroat** » Mon Nov 10, 2003 12:34 pm

hi

that's what i'm talking about. the chipping should optimize the burn. in diesel, usually the fuel consumption decreases about 1l/100km

dragon · Post by **dragon** » Mon Nov 10, 2003 12:38 pm

I can hopefully answer this authoratatively in 4 or 5 weeks, as megasquirt should be arriving in 3 weeks

Jamo · Post by **Jamo** » Tue Nov 11, 2003 12:45 pm

If you don't drive more aggressive after the tuning the car then:
-Generally chiptuning should lower your fuel consumption because a real chiptuning chip has got more optimised (ignition/fuel)settings than the fail safe original chip.
-The higher turbo pressure shouldn't make any difference as long as you dont use it .

But with a tuned car you will probably use the extra HP and then the fuelconsumption will increase for sure. And with more serious engine tuning than (chip/higher turbo boost) the fuel consumption will probably also increase.

Hi

lets put to bed one of the misconceptions about chipping the 480.
FUELLING is not altered, by the Rica or Superchip etc.

In a standard car, fuel and ignition is controlled by the same ecu which means everying can be changed at once.

The 480 has it's own seperate fuel ecu, with a hard-coded fuel map.
(which is the primary reason why Dragon and myself are having to have installed megasquirt.)

This map can't be changed and any tuning (cam, larger turbo) will leave the car under fuelled at critical times.

The standard fuel map is made for a standard car and can just about handle changes in boost pressure up to around 12-13 psi from standard.

To counter this on a standard car the most common used component is an FSE valve. This increases fuel pressure, so that for the same amount of time an injector is open from the standard fuel map, more fuel is injected into the engine for that period of time.

most electronic fuel injection system have an oxygen sensor system, where the EFI tries to get the fuel/air ratio to 14.7:1 (actually the optimum for power output is about 12-13:1 but thats for another thread).

As with any equation, if you alter one side of the ratio then the opposite side must be increased to match.
i.e more boost pressure means an increase of oxygen which needs to be countered by more fuel to keep the correct ratio.

I'm barely scratching the surface as i'm not talking about the highlift cams or large valves or ported heads all of which also effect the ratios.

So fuel compustion will decrease with nearly all forms of tuning.

Now then here's the offset.

Cruising at a constant speed will yield better MPG with a chipped car!

But thats another story