“The biggest problem with brakes would be fading. Cars are way way better than they used to be in the past but that's more of a formulae one driving style type problem which just wouldn't be appropriate on the road. 2ndry one is the brake fluid boiling. There are different fluids. I drove down the Glossknocker pass in a car once a long time ago and had no brakes to speak of when I got to the bottom. I'd guess all modern cars would do it easily now.”
Most cars have some form of ABS, running ventilated discs etc. The size and performance of these items is matched to the vehicle performance and use envelope. Add a performance increase (which is going to be used or you would not bother doing it?) and they are no longer matched and probably (speculation) not up to the job. Most modern cars have advanced ABS systems (not the old fashioned simple systems of yesteryear) which are linked into the other vehicle systems (transmission etc.) and all of this is out the window when you start playing around.
Fluid choice for the system is again linked to the type of system and the design of the internal components and the design of the valves and actuators etc. Again, fiddling is likely to result in a system performing in something less than optimum.
“Suspension – maybe the uprate the springs.”
And geometry (including different wheel/tyre combinations). Changes in compliant bush design (often stiffer). Reduced spring height (affecting overall vehicle dynamics) and changed spring rates – often variable rate. Shock absorber changes have always been the standard stock in trade for vehicle tuning, another area requiring extensive knowledge to achieve the correct results unless you are lucky or prepared to experiment and be capable of interpreting the results of any changes.
“Cooling. As Saab offered a power upgrade on a 95 without any effect on the warantee there doesn't seem to be a problem. They even pointed out that fuel consumption during some kinds of use would actually be better. I suspect what is actually happening really is that all cars are electronically limited. Saab normally offered a time limited power boost for overtaking. Some one working on engine management was wondering what to do about engine overloading when towing – from the engines point of view it's best to give the power that's needed. They can pick up when this is happening from engine data.”
I am prepared to stick my neck on the line here and say Saab are in a minority of 1 here. Certainly, most other manufacturers require modified cooling if you fit a tow bar (that is why they make them as kits). I know there are those who will claim it is a ruse to sell their kit, but you fit some spurious bar and start towing/using more power than was intended, then don’t bother trying to complain your engine broke to soon ‘cos I would have to agree that you broke it through misuse!
“There seems to be a lot of scope on diesels for increasing power by changing the limit and or mapping but there were a huge array of possible power levels available out of Rover V8's as well. I toyed with the idea of having one fitted to a Shogan and it was a case of what power would you like sir up to silly numbers. We found a nice fairly cheap Landcruiser instead.
The problem with using the power however on modern diesels would be very likely to be the clutch. Once upon a time the diesel engine was entirely different to the petrol one and would have a larger clutch – not so now they use springs and things to try and absorb the torque”
Diesels are not petrol engines (they have very different power/torque output maps). The internal engine components are also stressed in very different ways. Rover V* engines are a very old design and a huge amount of empirical tuning information is available. I have one fitted to a sports car that is tuned but it is an old car and the engine was altered along with a lot of other items on the car appropriate to the power output of the engine. Getting huge power outputs from these engines is not a simple or trivial matter. Clutch modification is included in transmission in my book and the mods run to a bit more than some springs….. You really think so?
All of this just adds weight to the argument against letting people make changes when they are fiddling with stuff they clearly don’t understand fully. After all that, what happens when you tell the insurance company it is no longer standard?????
Mark