Originally Posted by
rsnissan
Im interested
is it to do with cold starts etc, I have a P8 and would like to go GT30/T4 from a T38 (with rest of spec to suit) have ALS already but would want dizzyless enabled, and then mapping for the new turbo.
Well, in a nutshell, if you want a highly modified street car then you really should make the extra effort to ensure that it is not only fast, but that it also performs properly when cold. Commonloy, a badly mapped cosworth will sit there with its idle going up /down/up/down when cold. If you drive it, the car can stink of fuel and the throttle response be almost non existant with it needing harsh acceleration to make progress. This is all pathetic.
There is no reason that a well modified engine cant perform properly at all temperatures and anyone who says different, well, look at BMW/Porsche etc.. do their cars do this in the showroom? Ha Ha.
To get the mapping right when cold requires that we are able to actually emulate and adjust the fuel compensation maps when cold. These maps must be done when you are sure aht all the main fuel and spark tables that will be accessed cold are correct so that the multipliers chosen are not later made incorrect by main table adjustments.
A weber has 2 cold multipliers. one of them works for the first 27 seconds of cold start and is richer than the later one which works from then onwards. To be sure the mapping is correct, lets say we have one that hunts for fuel as its too lean and the revs go up/down/up/down and we add fuel into the correct tempareture stabiliser, perhaps the engine is at 5DegC, and we smooth it out, it doenst take long for teh engine to warm up and move onto the 10Deg C site, and the 15Deg site etc... so how do we know for a fact that at 5 and 10 its perfect, when we spent 4 of the 5 mins tuning it?
Thats right, we need to try again next time its at 5C, and thats not likely to be until tomorrow. If we have the car a week, we still only get 5 goes at that as it will take the first three days to get it setup, powered up and the base fuel and spark mapping completed. Top end mapping is childs play and not really a relevant part of the discussion, but it does of course still all take time.
Hope this helps and isnt over complicated as im rushing a bit this morning, i may revise it later.
