Let's have a bit of fun
Modest prize to the person that guesses the nearest (don't know what it is yet - I'll find something...)
What power will my
shiny new turbo give when it's dyno'd on 4th Feb?
To help you out, let's have a look at some stats.
Let's also forget for a moment that the dyno that Leighton uses appears to be a little on the generous side. The beauty of the FC performance dyno league table is that the vast majority of the cars are measured on the same dyno with the same settings, so its a valid comparison, even if the figures aren't 100% accurate.
Right - my previous turbo was a GT2871 with a 0.64AR turbine housing and a 48 trim cast compressor wheel.
This turbo gave:-
1bar396bhp @ 6926rpm
310lbs/ft @ 6359rpm
335wheel power @ 6951rpm
1.2bar424bhp @ 6895rpm
338lbs/ft @ 6145rpm
370wheel power @ 6923rpm
1.5bar451bhp @ 6826rpm
368lbs/ft @ 6036rpm
402wheel power @ 6678rpm
1.7bar457bhp @ 6575rpm
389lbs/ft @ 5702rpm
410wheel power @ 6482rpm
However, something to consider is that for whatever reason, this turbo on my engine gave more power than a GT2871 with the larger 0.86AR turbine housing on several other cars. It even managed to beat a handful of Coupes with GT3071 0.64AR turbines. This would appear to be down to a good VE figure, caused by a very good build (the rebore was highly accurate) a good head (one of Barbz's early efforts) and high comp pistons and C&B cams - all conspiring to give an efficient engine that seems to outperform expectations.
Next up is that fact that I've decided to be a bit different, and I've gone for a billet compressor wheel. This is 20-25% lighter than a stock cast wheel and because it's stronger, the central spindle can be thinner which in turn means that there's more blade area. On
a 2-litre Impreza simply adding the billet wheel (and remapping to suit) gained 20bhp.
However, I'm not just chucking a billet wheel onto the same turbo. I'm using the fact that the new wheel will spool up earlier than a cast wheel to go up in size slightly. I'm having a GT3071 with a 56 trim compressor wheel and a 0.64AR turbine housing, with a larger turbine wheel and a ported wastegate (to prevent the boost creep problem seen by a few 3071 owners, caused by the less restrictive exhaust side)
So - the hot side is less restrictive (this was the limiting factor on my old turbo) and the compressor side will flow more air due to being bigger and having the billet wheel
For what it's worth, my requirement is more mid-range power from spoolup to redline. Any increase in peak power is not a primary requirement, although it's difficult to see how I can't get SOME more.
So - take a look at
Leighton's league table - work out where I came with the setup I used to have and make a guess at where it's going to end up.
(note that this all assumes that nothing breaks or goes wrong while Leighton is mapping it....)