(26-11-2015, 06:45 PM)PugLee Wrote:(26-11-2015, 06:37 PM)Ruan Wrote: Notice that precise design is for Diesel motors which need very high boost pressures - turbocharged petrol motors don't... You simply don't need this - just run a single, GOOD turbo - I'm all for interesting stuff, but it's pointless, will eat money and the outcome will be poor since you simply cannot use the amount of boost pressure you're on about.
You also need to study the compressor maps if you are to make the setup you're on about work - the turbos you're intending on using are very poorly specced for that job.
Surely this setup can be run at lower pressures to suit?
Well, you could, but that defeats the whole object of what that configuration is trying to achieve - that's designed to provide high boost pressure, which is precisely what you don't want - because you cannot combat the issues with detonation before you actually start being able to utilise the boost pressures provided by a system like that at low RPM.
Why have any of the complexity and inevitability that it'll all go wrong, jam a valve shut and either produce insane boost pressures or not make any, when your money, time and resources would be better spent getting a single _good_ turbo to work efficiently...
I see so many crazy, hairbrained ideas which are all well and good, but if it's too complex, it just won't get done.
Just actually begun to look at compressor maps to maybe attempt to prove to you how far out you are with those two...
With 3 seconds of googling I found a T28 compressor map which proves that at the maximum pressure it'll provide PR2.8 it'll provide around 25lb/min airflow - enough for around 250hp. At absolute maximum airflow on the choke line which corresponds to around PR2.0 - you're getting 33lb/min.
Start to look at the GT3782 compressor map - well, 25lb/min hasn't even hit the first efficiency island barely, move to 33lb/min - we're only just beginning to look decent here on the GT37 compressor map, but the first turbo will now not be able to provide any pressure, it's overspeeding and choking up... To move 25lb/min into the engine at 4000rpm, you'd need PR2.8 - where you're RIGHT up against the surge line, because now the primary turbo is running out of puff...
They're very badly matched - the T28 isn't a high pressure turbo and is too small anyway, the GT37 is too big anyway - you'd run it into surge because the small turbo can't move enough air. If you were looking for a setup to do 4bar of boost to provide 380hps worth of airflow, but maxing at around 4000rpm, a GT3271R and that GT3782 would be a nice combination. But you don't need high pressure to get high horsepower, just rev it to 7k and realise you only need 22psi boost at 7k to make 380hp - but you needed 50psi boost at 4k
TL;DR - get an EFR/GTX.
