333pg333

Well the new motor started first time today which is always nice. I have been rather expectant about the results we get tomorrow at the dyno. There are many differences between this and the last motor and your mind starts almost playing tricks on itself by second guessing what may and may not eventuate.

So I thought I'd throw it to the panel and see what you guys think?

Basically the last motor:

3.1ltr

Stock length Arrow rods (lighter than stock)
Stock pin position and size CP pistons
8:1 c/r
3ltr crank severely lightened.
Moderately ported head with 49mm inlet & 40 ex valves
247 cfm @ 28 .550" lift Inlet
192 cfm @ 28 .550" lift Exh
Cam with 537 in / 502 ex lift
Hydraulic lifters
GTX3582 .82

Best result on dyno was 552whp / 520ft/lb @ 25psi (as shown)

New motor:

2.5ltr
Longer custom Carrillo rods (approx 7mm)Still lighter than stock
Custom CP pistons with much smaller skirt and wrist pin (much lighter piston and assembly)
9:1 c/r
2.5ltr crank moderately lightened.
Huge ports with 49mm intake and 43.5mm ex valves
273 cfm @ 28 .550" lift Inlet (279 @ .600)
206 cfm @ 28 .550" lift Exh (211 @ .600)
Cam with .595 in / 526 exh
Solid lifters
Same turbo

We also have longer runners in the smaller motor but the internal diameter is over 5mm larger on the new intake and the bellmouths are considerably larger.

So parts of the motor will be lighter, crank no so. We lose approx 600cc in capacity but gain an extra point in Compression. The data shows that the head won't go into choke up to and possibly over 8000rpm where our last chart shows how it fell over at just over 6000rpm. Will the larger longer runners improve the torque at the expense of top end?

My thoughts are of course we'll lose some torque and probably the broadness of the powerband...however if we can continue to make power well over the last motor, then perhaps it won't be so much smaller, just further up the rev range. We should make up some of the torque loss (drive out of corners) with the extra compression ratio. Will probably have to run a few more psi to make similar peak power too.

What do we think?

Duke

This is going to be very interesting!!
I've tried to do some basic calculations but it is impossible to guess

IF the combo indeed can make max power above 7500 rpm I will guess that it will make the same hp at the same boost as the old engine. At the same rpm as the old engine I'd guess it will be 20 hp down at the same boost.

333pg333

I'd be happy enough with that outcome. The other advantage is potentially less gear changes with the higher available rpms...although with less lower down tq will we have to drop down an extra gear coming into corners as to drive out in the meat of the rpms?

JET951

Are you going to use the same boost as before (25psi) or increase if possible? My guess is that Robbo will crank it up until you hit a ceiling. In which case i think your new setup will be less restrictive and allow a bit more boost. Im going to guess the hp around 570hp at 30psi with 500ft/lbs.
Sean

Paulyy

I think you'll get peak torque around 4800-5100 rpm. ~450- 500ft/lbs and peak hp around 7800-8000 rpm 580-600hp.

I'm thinking with the 8v head and 2.5L you'll get more linear torque curve and not fall as much higher up.

333pg333

The interesting thing will be putting the intake guy's theories to the test. Will we get 'free torque' with these longer runners without sacrificing top end? We guess that we're going to have to run more boost and wouldn't necessarily want to run at 30psi if we can avoid it. Looking on at Gustaf's latest results with more power than either of these motors on 10psi less...brilliant stuff. Can't wait to see when he cranks it up!

That's another thing, the linearity could prove faster on the track too. Even though we had tons of torque on the old motor which was a major factor in our good lap times, it was also quite easy to spin up the rears to our detriment. So I'm hopeful that the linearity will increase the driveability as Pauly touches on.

refresh951

Wild guess

470 rwhp at 25 psi at 7000 rpm
450 ft-lbs at 4700 rpm

Really looking forward to the results. Looks great! Glad all is well thus far!

Paulyy

My theory goes like this.
Choose a peak torque figure at an rpm point.
Then work out how to keep that torque linear to redline with out much drop.

IMO dropping torque is a bottle neck. I'd rather have 400ft/lb at 4k rpm and trop to 350ft/lb at 8k rpm and make 500hp
than have 450ft/lb at 4k rpm with 450hp - 295ft/lb at 8k

You'll be spending more time north of 5k rpm and wont rarely see the peak torque coming out of corners. last place i want to be in my rpm range is before peak torque is reached as this is when the turbo starts its stride, so you'll still have turbo lag and loss in time.

333pg333

Well looking at the old tq curve, without any data in front of me I'd imagine that where we were in the rpm range on some slower corner exits would have been very much in the meat. Also we were able to use a higher gear in many corners and just drive out on the tq. With the new motor I suspect we might need to downchange to a lower gear possibly.

333pg333

...

Paulyy

would be interesting to see how much you'd need to change driving style.

Who took the car into the dyno? I'm keen to see results!

333pg333

I agree. It will be interesting just how a few engine changes might influence the driving and lap times.
Paul is taking it in this afternoon. Tick Tock....

Paulyy

Should have went in the morning

Geneqco

Great news Patrick, really glad to see it all coming together for you!

My guess is, providing everything works together optimally and you don't have any head lift or exhaust back pressure issues, somewhere in the low 600's HP, possibly a little higher depending upon how much you crank up the boost.

Can't wait to see the results!

Paulyy

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