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boost taper Posted by jak [Email]  (#195) [Profile/Gallery]
(more from jak) on Fri, 22 Sep 2006 19:25:14
In Reply to: The idea is to..., saabrobaz, Wed, 20 Sep 2006 09:44:47 Members do not see ads below this line. - Help Keep This Site Online - Signup |
boost taper is a part of physics using smaller turbos
the engine is a pump with a fixed displacememt the faster it spinns the more air it moves
the turbo is a pump with a maximum volume it can move,(larger turbos move more air at a higher engine speed) so the smaller turbo may be able to make 20PSI boost at 3500RPM but cant keep up with the flow of the 2.0 litres spinning 5500RPM so naturally boost drops
I remember with my T3/60 on my SPG I actually ran about 17PSI base boost & bypassing the BPC Id get about 3PSI drop or more higher in the RPMs if I was trying to push more boost the taper would be more
the other part of boost taper in APCs & trionic engine management is due to the perception of pre ignition
if the timing, intercooling & fueling arent set up corectly by the time the engine hits 4500RPM it is so heat soaked that its pinging & the boost gets dumped
in a trionic ignition map you may see 0*BTDC timing at max boost or even ATDC #s for a short period then the timing will taper upward as RPMs increase,
in an LH car you just have the max retard on the diaphram which we usually set to 10 or 11*BTDC which is basically a fixed timing setting at any RPM above 10PSI of boost
finally you have what may be programmed taper
Id say that by the time you get through the fists few points above that you will notice much less taper
definatly buy modded APCs or mod your own but it all works together & the better you cover the other bases the more relyable your car will be
take care
JAK
, Fri, 22 Sep 2006 19:25:14 <-- Viewing This Message
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