BHP increase

Recently, I reluctantly sold a 2009 Laguna GT with a wonderful 2.0-litre 205bhp turbocharged petrol engine because I need an automatic. Its replacement is a 2009 Laguna Initiale 2.0, which although automatic and petrol, only produces 170bhp. I know the AJ0 autobox can take the extra torque, so I would like to increase the power to equal my old GT.

I understand the GT has a Mitsubishi twin-scroll turbocharger, but I can’t find out what type/model, etc. I believe the Initiale has a different turbo, but again I can’t find what type/model. Likewise I can’t find the specifications of the fuel injectors for either car.

I have a firm in Leeds (RS Tuning) in mind to attend to the engine mapping, but I need to know what the best solution is because, at nearly 60 years old, I’m not a boy racer. I’m not interested in all-out power, as economy is important to me too. The GT’S torque was fantastic – it was just about un-stallable and would exceed 35mpg on a long but fast-ish run. RS Tuning are suggesting a Megane RS250 turbo and 630cc injectors, which they said would easily give 250bhp, but this is more than I want. I don’t know the flow rate of the Initiale’s injectors, but I might not need to change them. Likewise, I suspect I need to swap the turbo but the GT’S might be better than the Megane RS 250. The RS quote was more than £2000. I’d welcome your thoughts on this.

Finally, do you think there’s any issue with putting an auto on a rolling road? I think I would have it done in cold weather in case the transmission fluid gets too hot. I’ve checked and the GT’S bigger front brakes will fit the Initiale’s suspension/ hubs/smaller wheels.

Any advice gratefully received. J Sykes

Checking out the specifications of the two engines, it appears that the bore and stroke are different, along with the compression ratio. The 205bhp unit has a bore of 84mm and a stroke of 90mm, while the 170bhp unit has a bore of 82.7mm and a stroke of 93mm. There is also a difference in displacement between the two engines of 3cm3 – although this does not sound a lot, it is these small differences that give the extra BHP. Although replacing the turbo for the variable geometry turbo (TGV) may give you a wider torque range, if it is purely fuel economy you are after then a simple remap should suffice.

I do not see a problem putting the car on a rolling road, provided there are proper facilities, with a cooling fan giving a through draught when testing.