Toymods Car Club Inc: Tech & Conversions => PARALLEL Twincharging, whatever....

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oldcorollas
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Kita-Ku, Sapporo, Japan
Registered:
January 2003

Re: PARALLEL Twincharging, lets make it work	Tue, 23 August 2005 08:31

thinking a bit more abotu the SC recirculation.... with SC only, the air going in is at 1bar, the air going out (we will assume) is 2bar... (well actually, it is still 1 bar, just that when it gets into the system post-SC it becomes 2 bar as there is less space for it to occupy) when the turbo starts pumping air.. the air to be recirculated will be at 2bar (absolute) before T3, but between T3 and T1, the air must be at 1bar.. if it is higher than 1bar, the air will escape back past T1 and back into the SC intake tract..... so the SC is still pumping 1bar air into a 2bar system.. but the source of the air is from the pressure side.... so the amoutn of air going into the system is still the same, AND the SC crank losses are still the same.. since it is not freewheeling... the only way to reduce the SC losses is to have the input and output air at the same pressure, and then it will be freewheeling as such, and only have friction losses... when T1 is closed and T3 is open, this will be the case.. but i think the transition of T1 and T3 needs more thought based on a volume/pressure/flow point of view as it stands, T3 bleeds2 bar air at a rate that keeeps 1 bar pressure between T3 and T1, and we will still have the SC pumping losses. these losses will only be reduced when T1 is closed enough so that the SC intake air (between T1 and T3) is higher than 1atm,which can only be the case when T1 is closed... if we close T1, so we have a higher SC intake pressure, the SC still pumps more air, at a lower pressure differential, but the input to the system is zero... so the SC may as well be off.... maybe there will be a small period of time (i hope it is small, otherwise we are not accelerating fast enough ) whereby we can almost close T1, accept the loss of air past T1 back into the intake tract, BUT, the slight reduction in manifold pressure is offset by the gain by the reduced pumping pressure of the SC... so in fact, to make the crank output smooth, we DO need a SMALL dip in the manifold pressure, but only enough to compensate for the reduction in SC losses.... i would guesstimate roughly that we can gain about.. what?? 20hp/15kw in pumping losses by increasing the SC intake pressure.. at 5000rpm, this equates to about....7.9Nm.. which on a 1.6L motor is about 0.73 psi..... so we could have a 0.73psi loss from reducing the air input to the system, and yet still have the same crank output... again... when we turn the SC off, if we do so in such a way that results in a 0.73psi loss, we have same crank output... or said in a different way, if we don't do anything to reduce pumping losses of the SC before turning it off, we can still have an instant loss of almost 1.5psi, but STILL have the same crank output...... which means that we can stil have the SC contributing some air to the system (ie 40hp worth) and when we turn it off, as long is it doesn't upset the turbos compressor flow, we have smooth crank output... just more fodder for thought Cya, Stewart and to ppl just joining the thread, please go back and read all the posts to get up to speed TIA.. [Report message to a moderator]

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