I found this specs on the internet...

Engine model 4G91
Displacement, cc 1496
Max.power (Net), kw(PS)/rpm 97 ps (71.34 kw) / 6000 rpm
Max.torque(Net), N*m(kg*m)/rpm 12.8 kg*m (125.53 N*m) / 3500 rpm
Power density 10 ??
Engine type Serial 4 cylinder DOHC16 valve
Engine information
Fuel system Electro- carburetor
Fuel type Unleaded regular gasoline
Compression ratio 10
Bore, mm 78.4
Stroke, mm 77.5
Fuel consumption at 10-15 modes, l/100km 6.2

While...

Engine model 4G15
Displacement, cc 1468
Max.power (Net), kw(PS)/rpm 91 ps (66.93 kw) / 6000 rpm
Max.torque(Net), N*m(kg*m)/rpm 12.4 kg*m (121.60 N*m) / 3000 rpm
Power density 9.01
Engine type Serial 4 cylinder SOHC12 valve
Engine information MVV
Fuel system ECI multiple
Turbocharger No
Fuel type Unleaded regular gasoline
LEV system (Low emission vehicle) No
Compression ratio 9.4
Bore, mm 75.5
Stroke, mm 82
Fuel consumption at 10-15 modes, l/100km 4.7

Why is the fuel consumption for the 4G91 engine so much higher than the 4G15 when both are 1.5l engines?
What does it mean by "Fuel consumption at 10-15 modes"???
Lastly, say I have a Satria, would it be wise to switch to the a 4G91 engine or 4G15 if fuel is my main concern???

Thank you for your opinion...

So the 4G91 is better?

Juz wondering, how do you know how economical an EFi 4G91 Twin Cam can be??? Have you use it before???

"Our" 4G15 is underpowered and consumes more fuel because of Proton's "clever" idea to match it with a 3-speed auto gear box right? Or does it also suffer with a manual???

I found it in a 1993 Mitsubishi Mirage...it comes with automatic tranny...does it still provide good power and decent economy???

Wow...RM5000.00... I think after transplant, no money to "play n mod" d...

Does it come with the 4-speed auto gearbox?

Auto only RM2+++... That sounds reasonable... Hope the gearbox brings no problem'

What's the advantages gained???

Will it save fuel???

Well, actually that's the main point I wana mod...
I like the whole Wira look (aeroback/Satria)...but it's a fact that these models use up petrol as it were free!
So, I would like to get a more efficient engine...not til like that of the i-DSi, but something better than the stock...
If I wana go for power, might juz go for EVO half cut'

Well, that's y I wana transplant either a 4G91 or 4G15... their FCs are said to be better... I juz wana achieve 6l/100km @ around 16km/liter...without sacrificing too much power and torque...

Oh btw, what engine are u using??? Stock???

Of coz I don't mean 100% city driving...
I mean combined...
I drive to Setapak frm Pdn Indah daily...so, hoping to get a good FC car since the route does not have heavy traffic...