y cymro wrote:
Ignition Timing:
The Z3 3litre has active detonation control – a knock sensor. The trick with these is to run the engine close to this limit without triggering the knock sensor, as doing so will retard the ignition. Hitting the trigger repeatedly increases the amount of retardation by increasing amounts so is to be avoided. Without running higher RON fuel or changing the combustion chamber design the trigger level will be the same. No gains here either, other than the combined effort that may be possible on some engines after peak power, already covered above.
Again, it may be possible to find 5% at lower revs. Let’s be generous and offer a potential 10% increase at 4k revs, or therebouts. That could provide up to the 15bhp bandied about by most remappers as being achievable on the Z3.
Excuses 1:
What about ‘other markets’ having shite fuel, often used as justification for gain. No gain here, as manufacturers map cars for their target market and whatever RON fuel is generally available. So a UK car will be mapped for 95RON. A custom remap should provide 2 or 3 bhp if you run on 99/100RON fuel and the car has active detonation control. But we’re not discussing that here.
Excuses 2:
If you read adverts by tuners, they use subjective terms like ‘lively’ and ‘spirited’, which mean little. A common way of achieving this is to over-fuel when you quickly mash the accelerator pedal to the floorboards. Power won’t be increased (it may actually decrease) but there will be an effect like an accelerator pump on a carburettor’d motor. If you’ve driven a car with correctly set up multi choke carbs (such as Weber, Dell’orto or Solex) you’ll have experienced that feeling of sharp throttle response that’s difficult to achieve with fuel injected motors. Only two manufacturers come to mind that have done this properly: Peugeot did it very well on the 1900 205gti and more recently, Alfa Romeo did it superbly on the wonderful Busso v6. It feels great, but no power gain though.
So we can gain a couple of bhp (though maximum gain probably won’t occur at peak revs) and make the car feel more spirited to drive. Only you can decide whether that’s worth hundreds of pounds.
For another discussion, is whether you should believe that an ordinary bloke with a laptop and a map altered by someone else in Italy (there’s a well-known Italian website selling maps for most cars for not many Euros) can really introduce benefits compared with a manufacturer with highly skilled and highly resourced staff.
I’ve not visited the forum much in the last weeks due to the same reasons expressed by others. I’m told that Richard has defended his claims, and I may address this later once and if I read all the posts.
But, you’re not going to gain 30-40 bhp on a Z3 by just a remap.
There is a flaw in your argument, IMHO, you state a number of very logical reasons why remaps on naturally aspirated engines don't benefit from a remap.
But then you say 15bhp is achievable.
So if 15bhp is achievable, why isn't 28bhp?
Surely, either a remap gives nothing or "some" increase. The factors that determine "some" will depend on how the manufacturer set the engine up from the factory.
On a separate note, my 1925 Citroen only makes 11hp. Is there a chip that will mean I can go up hills without resorting to first gear?