Thom

Paulyy, check out the Bombardier if you have the time, should make you feel not too far from home...

http://www.qype.co.uk/place/52366-The-Bombardier-Paris

blade7

Do they serve Fosters ?

facboy

aussies don't drink fosters

Paulyy

If i have time i may have to!

I dont. not in melbourne. we've got vb hahah but dont drink that also. Corona or carlsberg

blade7

Heineken, Fosters or Carlsberg I,m not a beer snob, whichever's on offer at the supermarket that week .

TurboTommy

One has to be careful of that statement.
There is a price to pay for "expandability" and "headroom".
Larger compressors result in higher exhaust back pressures, given the same turbo hotside.
Highest power will be achieved by using the smallest compressor possible, which is still big enough to flow enough air for the boost you want to run at the highest RPM (even if that falls a little more to the right on a compressor map).

Paulyy

on a 3L ...When i was looking at numbers, running the gt3582r or the gtx3076r, when looking at numbers on paper the hot side of the gt30 .82 in this case (most popular choise); and the 1.06 have similar flow rates there for should result with similar back pressure. but the gt35r has better flow for lower boost when the gtx30r will show good numbers in the 25psi+ area.

That's the way i see it.

correct me if im wrong though

Penguinracer

So Tommy you're coming down in the direction of the 71R for a 2.5 & the 76R for a 3 litre?

I ran through the calcs on the Garrett site for my 2.5 based on 500 bhp, 6500 rpm & a .92 VE & I came up with a Compressor Discharge Pressure of 47.36 psia & a pressure ratio of 3.34
With a N/A big-valve head, 70mm throttlebody, cam, standalone & aftermarket intake I think the VE figure should be realistic for an 8V.

This put me well within the 76R map (still upper right) but just off the 71R map.
This sizing is for a DE car, not a DD.

Even if I can get hold of a GTX there's still the issue of the engine mount. The crossover & downpipe issues can be resolved with aftermarket V-band solutions.

Penguinracer

Correction - ******** here was looking at the GT30 maps !
Looking at the GTX30 maps there doesn't seem to be much in it!

Duke

PR 3.34? Are you going to run 30 psi of boost?
And I think the VE is a bit high, I would calculate with 85%.

You will get better average power throughout the powerband if you max out the map at redline instead of being in the middle of it.

Penguinracer

Duke, if I recalculate using a .85 VE I get a Compressor Discharge Pressure of 51.1 psia & Pressure Ratio of 3.72.
This puts me on the outer edge of the 71R map & reasonably comfortably within the 76R map.
My question for you is - will my 2.5 be making more power & torque at any place in the rpm range (0 - 6500 rpm) pushing the 71R harder rather than operating comfortably within the 76R envelope?
I'm basing my assumptions on 500 bhp from a 2.5 - I assume this is flywheel hp- is that feasible with a 6500 redline & 20 psi boost?
Tim

Duke

PR 3.72 means that you have a boost level of 2.72 bar = almost 40 psi!
Subtract about 0.2 bar for pressure loss through the IC ~ 37 psi intake boost level. So the answer is no, you won't get 500 bhp on a 2.5l @ 6500 rpm with 20 psi of boost. Well maybe on some dynos...

You should calculate the other way around - rpm, displacement, VE and desired boost level. That will give you the necessary flow rates at a specific pressure ratio.
Then calculate for a couple of brake points through the powerband, say 3500 rpm, 5000 rpm, 6500 rpm, and make sure you cover as much of the compressor map as possible and don't fall out on either range.

333pg333

Also note that when comparing against other cars / forums / man in the street etc....look at their charts and see where boost/rpm is the norm. It's generally much higher than we see for 944turbos. Add to that they usually have higher ceilings for rpms too.

Penguinracer

After running the numbers it looks like 500 bhp out of a 2.5 litre is pretty optimistic & given that the 71R is supposed to be good for 560 bhp I don't think there's much chance I'll be threatening the "choke" lines on the compression map.
As Duke observed, to get 500 bhp out of a 2.5 would involve boost levels (& a redline) which just aren't feasible for our motors - well not unless you're building a "grenade" of a qualifer unit!
With the 76R I could be looking at surge in the lower rpm range & the exhaust back pressure Tommy mentioned.
I think I've debated this thing full circle & the guys at the turbo shop were recommending the 71R with a .82 which is broadly what Duke & Tommy are alluding too.
I can imagine that with the larger compressor working underspeed across the rev range power & torque could be down compared to pushing the smaller wheel harder.

JET951

Hi Penguinracer,
Are you only limiting yourself to a choice between the turbos you have listed? We have had first hand experience with the gt3071 and the gt3076 as well as the Vitesse stage 3 and 5 all on 2.5ltrs. We have not used the GTX series so i cannot comment although my thoughts would be that there would not be a huge improvement on the GT series turbos.

As far as ease of install the Vitesse turbo setup wins hands down. it bolts up to the standard engine mount/oil lines and down pipe. And fits under the inlet manifold.
The Garrett GT series will need a custom oil feed line, custom down pipe and crossover and a modified Engine mount. all to which add money to the cost of the turbo install.

As far as power usability is concerned the Vitesse stage 3 had the largest power band available. I will give you 3 examples i have from some dyno sheets we have
951 #1: Vitesse stage 3 kit 15psi 3 inch exhaust
951#2 : garrett gt3076 3-5 inch exhaust, vitesse chipboard and piggyback 22psi E85
951 #3: garrett Gt3071 3 inch exhaust 17psi
these figures are comparable as they were done on the same dyno. this dyno does read very low compared to the equivalent US units.

Vitesse stage 3 3000rpm 140whp
Garrett GT3076 3000rpm 60whp
Garrett GT3071 3000rpm 98whp

Vitesse stage 3 3500rpm 210whp
Garrett GT3076 3500rpm 100whp
Garrett GT3071 3500rpm 152whp

Vitesse stage 3 4000rpm 245whp
Garrett GT3076 4000rpm 195whp
Garrett GT3071 4000rpm 200whp

Vitesse stage 3 4500rpm 255whp
Garrett GT3076 4500rpm 254whp
Garrett GT3071 4500rpm 225whp

Vitesse stage 3 5000rpm 270whp
Garrett GT3076 5000rpm 270whp
Garrett GT3071 5000rpm 240whp

Vitesse stage 3 5500rpm 275whp
Garrett GT3076 5500rpm 285whp
Garrett GT3071 5500rpm 255whp

Vitesse stage 3 6000rpm end-whp
Garrett GT3076 6000rpm 290whp
Garrett GT3071 6000rpm 270whp

Personally i think the Vitesse stage 3 shines through here. its was only dynoed at 15psi.if it were dynoed at 17 it would produce i would imagine the same power if not more then the gt3071 and if were dynoed at 22psi with E85 i am sure it would produce more power again. infact if i get time before we swap our engine over to the 3.0ltr 16v i will get a dyno readout from the vitesse stage 3 on 20psi with E85 for good comparison. the power of the GT series seem to be lacking a little in the bottom end. From our results i would consider that the latest is not always the greatest and it may be worth to look at other alternatives
Sean