I'm wanting to mod my Rover 25 2.0l TDiS to give it a little more umph!
I'm aware that getting the EMS "chipped" or "tweaked" can give up to 30% more power without noticable loss of fuel efficiency - are these claims wildly exagerated?
also apart from the cosmetic impact and the increase of grip, will going from 15" to 17" alloys make much difference assuming the overall tyre diameter doesn't change?
What stuff should I be looking to improve on? Exhaust, Turbos, cams? I'm not a mechanic, and don't expect to be doing much more than changing plugs and filters myself - so what sort of money should I be looking at to spend to get "good under the hood"?
Not really. Often the power increase quoted is taken at the point where the difference between 'before' and 'after' is at a maximum, but it's certainly quite possible to get a 20% increase in maximum power, and a significant increase in torque accross the rev-range.
It depends to some extent on the wheels and tyres you use. The bigger alloys might actually be heavier than the originals, in which case you will increased the 'unsprung mass' of the suspension system, which is a Bad Thing - it basically results in worse grip on rough surfaces. Also, without wanting to go too nerdy, you mill almost certainly increase the moment of inertia of the wheel(s), which means that a larger fraction of the engine's power will go into speeding up the rotation of the wheels, and thus less into accelerating the car. This is a very small effect, and only really of concern to racing teams who need to squeeze every last bit of performance. The other side of it is that bigger tyres cost more pennies, so you might not be able to put as good a quality rubber on as you can on your 15's.
Things like changing air filters, cams and exhausts improve the breathing of an engine, and only give an improvement at high-revs. As the diesel engine is inherently low-revving, it really isn't worth making that kind of modification.
If you _really_ want to improve the power output - more than can be accomodated by chipping - then you need a bigger intercooler, or even a chargecooler (see
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and a customised ECU. It's possible that you might reach the limits of the fuel injectors, in which case upgrading those might be an option. If you go this far, then the bottom-end of the engine is probably going to need upgrading, as will the gearbox, and things start to get expensive. Allard
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have some good general info on tuning diesels, and can probably answer any questions you have. Similarly Van Aaken
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