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:-

1bar
396bhp @ 6926rpm
310lbs/ft @ 6359rpm
335wheel power @ 6951rpm

1.2bar
424bhp @ 6895rpm
338lbs/ft @ 6145rpm
370wheel power @ 6923rpm

1.5bar
451bhp @ 6826rpm
368lbs/ft @ 6036rpm
402wheel power @ 6678rpm

1.7bar
457bhp @ 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....)

484bhp

475bhp

449BHP @1.2 BAR
473BHP @1.5 BAR

497 bhp & 415ft lb @ 1.75 bar
475 bhp & 405 ft lb @ 1.5 bar

443 bhp at 1.5 bar. Mock not, you heard it here first

487 bhp max

478bhp.

Im along the lines of Hovedan on this one im afraid, more or less.

Id say on high boost, what ever that may be, im guessing around 1.7 bar, 455bhp.

Dont ask me why.....

485 at 1.5 bar.

After reading your turbo thread I now know less than I did before, and that was not much Good at mathematics though.

467 max, should be within 10bhp though.

455 will all the midrange you required. If I win I'd like the M reg 16V as my prize please - thanks

If I get it right can I have your old 2871 for free??? 505Bhp

think nigel will agree to that.... Although your next dyno graph will read about 30 bhp!

and about '2' ft lb or torque!

No problem

While it was on the car, I couldn't get it to rev past about 2,500rpm and the smoke out of the exhaust meant I couldn't see any cars behind

You're welcome to it.....

476bhp @ 1.5 bar

1.5 Bar 462 BHP 373 lb/ft
1.7 Bar 477 BHP 398 lb/ft

If you can keep the boost and ACT stable to 6895 RPM (as with the original 1.2 bar run) you might see 500 BHP

472 bhp @ 1.7bar
401 lb/ft

465bhp & 375lb/ft at 1.7bar

I'm not going to offer a figure but I will say this;

It won't 'spool' any earlier, it will more than likely stay the same or show a positive boost a few hundred rpm later.

The torque slope will be steeper although the peak won't move, from aprox 5.5k-6k rpm to redline will show a 15% gain more or less independant of the boost level run.

But then I could be completelty wrong.

15% of 450 = 67.5

so you reckon nigel could see between 515-520?? That'll be mighty impressive on that hotside!!

Nick

442 bhp max

Nick, if you re-read I was talking torque. Yes it would be quite impressive, but VE counts remember !

481 bhp.

464bhp at 1.5bar

Good luck - is the first prize a night out with JBT?

No - that's second prize

First prize is a night IN with JBT.....

nice.Im quite boring at home so dont get your hopes up.

too true

482bhp from me!!

Good luck mate!!