turbo johan said:
Isn't there enough exhaust energy for the HP to keep it "compound"
till the end of the rpm range?
Yes, there is, but EMP would rise because the system is choked flowing through the HP turbine bottleneck.
That means it run 2.5/2.6 bar boost @ max hp @ 5500 rpm.
With 90 % ve and 17:1 lamda i need a some more boost for that hp what i calculate.
So i do something wrong i guess..
Max boost will be about 2.8/2.9 bar in midrange?
My calculations fully support my target HP. Pics to follow in a future post that will back up all the numbers used below, which reflected the assumption of an 8V head with VE/PD injection technology and 400 HP. With a 16V CR and a little extra boost, I should be able to reach 450 HP easily:
VE: 91%
Boost: 3.5 bar absolute
Fuel LHV: 42.5 MJ/kg
BSFC @ rated power: 222 g/kWh -- incidently, this is the same as that achieved by the 1997 VW Motorsport R-TDI at rated power and corresponds to a brake thermal efficiency (BTE) of 38.1%
Lambda: 1.2 (AFR=17.5)
Gas constant of Air "R": 287 J/kgK
Inlet air temperature: 313 K
BMEP = BTE * VE * LHV * BOOST / ( AFR * R * T )
= 32.8 bar
BRAKE POWER = 0.5 * BMEP * RPM * DISPLACEMENT / 60
= 300.4 kW = 403 HP
What will be the PCP max? 250 bar?
Yes, and achieved when a CR of 15:1 is used with the above numbers. This is the maximum figure at all operating points. At max power, PCP is "only" 230 bar. With a CR of 16:1, PCP comes under 250 bar at max power but peaks at 265 bar from 4500 - 5000 RPM.