Mudgey wrote:TDi-North wrote:Because there is a turbo. Its not there doing nothing until 6000rpm. It will be making a few lbs of boost then when it goes through the supercharger its increased further. The idea of having the supercharger there is to add to the low down grunt missing when you just turbo it. Think it was also bigger displacement which always helps
I am not sure if you have read my questions correctly?! I completely understand the concept, but most non aftercooled JRSC cars are only making say 180 lb/ft of torque before 4k and this thing is atleast 50% more again, hence my original question about whether it is running smaller pulleys, aftercooler, stock bore/stroke to get the hike in low down grunt over and above a stock JRSC setup... I have never built my own twin charged engine but I honestly don't think the turbo is boosting a couple PSI before 4,000 rpm, infact if anything the inlet tract through the chargecooler and turbo will be under a very slight vacuum until there are enough exhaust gases to spool it up. To avoid further confusion: I am discussing the RED graph.
Basically, Paul is right...
turbo is making 'some' boost from <2,000 rpm.
SC on it's own has to 'suck' atmospheric pressure though whatever intake setup (air filter/pipework/etc), and when all said and done, Roots superchargers are not that good at sucking, this get's much worse once you start to ask them to pump any significant pressure.
now, if you give it a 2-3Psi head start, then the goal posts move quite a bit, with this setup, we were getting some 1Bar boost from before 2K, by 3K it was making 1.2Bar, at which point boost control of the SC was kicking in, this then not being surpassed until the turbo really picked up and ran with it.
without the turbo, I would suggest the engine might make ~250Lbft (at the hubs - it's a 2,140cc block)
other thing to remember is that the turbo needs exhaust mass to spool up, hence why most big installs don't spool up till 5+k, the advantage of this setup is that the SC gives enough boost for the engine to have much higher exhaust mass at low end, thus spooling up the turbo much earlier, and remember, this setup is using the 1.03ar turbine housing, the biggest there is, with a smaller 0.76ar, it would be dramatically quicker, but pointless as we don't need the boost and it would then choke the top end.
other big upside to this setup is it;s just as drivable as any other SC install, zero (and I mean Zero) lag, no sudden boost-rush's, totally controllable with the throttle, so you can sill make part thtottle adjustments on the limit's of grip in corners without any nasties.
TDi-North wrote:RM CYA wrote:TDi-North wrote:Motors dead now anyway. :bigcry:
What happened? What an absolute monster it was!
Real.shame and one of the quickest things seen out in Time Attack. All the time and effort that went into it it's such a shame for the lads.
Pictures showed an actual piston missing.
I spoke to Jamie at Brands last weekend who owns the car and they putting it down.to incorrect ring gaps and thermal expansion. Everything.was gapped to manufacturers specs but when this happend they contacted the manufacturer.who quickly changed their specifications online to a bigger gap!
Yup, bit of a downer, but looks like that was it... working on what spec's to use for the replacement, but looks like nothing drastically different.
Might double up on the fuel pumps as it's max'ed out the single 044, that said, the exhaust is also max'ed out (to the point of some 9-10Psi at the turbine exit).
As they say, onward and upwards!
(Gauling as before it let go, I had done a 1:01.7 on wets and a 0:56.1 on slicks just warming up on low boost on the test day)