J Chen

Hey NZ : Diy one yourself. Not that difficult. I'm gonna do one myself soon.
Would be even better if we can get taper manifold runners but I guess
those tapered pipes are difficult to source.

Coleone : What happen to your sleeved engine ? Since you're running
stock 2.5, are you already or have you considerred increase the compression
ratio slightly to 9:1 ? I would do that the next time when I mod the heads.
Should give the engine better response as well as better turbo spool up.
I've a 16v 2.5 head sitting around & am toying with the idea of installing it
on my 951.

Duke

Has anyone considered a T61 instead of a Garret GT30?
A bit more expensive but the map looks even better suited for a high hp 951.

J Chen

Hi Duke,
Why T61 ? Compressor flow is only part of the parcel.
I think many people overlook the importance of turbine
housing designs & tubines itself. I don't know if you've
looked into the design features of the GT series. I have
& I can tell you that alot of R&D has gone into the hot
housing side especially the design of the turbine wheel.
Pointless to get a compressor that flows lots of air if the
turbine can't generate the power to drive it. BTW no need
to go T61. A 60-1 hifi with stage V turbine in a T3
hot housing is good enough for big hp on a 2.5 if you can
live with the lag.

Corleone

Much to big! You can calculate with 10 lb/h för every 100 of hp and you need to choose a turbomap compressordiagram at full boost there you be to the right of the lines but maybe still at >70% efficency. If you choose a turbo and your max flow is in the compressors highest efficency lines (in the middle) it will be to big at the street with a narrow power band. It will be hard to reach moore than 500 hpīs with a 2,5 L so most of us choose to big compressors and to small hot-sides. You cant have power from 2-7000, that turbo dont exist. Many here at Rennlist wants turbo that spools early and fast and of course its nice, but its always a compromise. For myself I think its moore fun to gear down so I have 4000 rpm and then could rev to 7000 rpm.

My own compressor can deliver 47 lb/h at the most and with still 70% efficency and deliver about 40 lb/h at 79%. I hopefully can get up to 450 hp with that but it will need boost about 20-21 psi at 7000 rpm wich is a lot. And of course it will need a great head, cam, exhaust and a not to small hot-side. Many people choose bigger and bigger compressors beacause they think they will have moore power but in most cases it would helped to have a bigger hot-side. When the hot-side/exhaust is to small the exhaust temp go straight up and then nothing will help. If you have the right hot-side the compressor can deliver like its c-diagram, with a small hot-side it can not. The exhaust back pressure will affect the entire way around and spread to the "intake side".

J Chen

Way to go Corleone. Hey, still waiting about
your engine.

Duke

J Chen you're confusing the T61 as a bigger version of the 60-1, which is not the case.

Corleone which GT30 do you have?

I disagree that the T61 is much to big, or I'm missing something...
Compare its map to the (proven) 60-1 and it just looks better to me.

Edman951

A T61 is too big for a street 951.
Check out this map it with a 951 at 20psi.
http://sites.vwsport.com/944turbo/t61map.jpg

J Chen,
It's not fully tuned yet still. I am waiting to receive my remapped chip. The top end is tuned for 16psi.
But the low end is not perfect yet.
Hope to get the chip soon to finish my tuning.

Corleone

My hotside is a wheel wich measure 2,36/2,17" (trim 84) in a A/R 0.61 house. In area its about a KKK 8 but with way moore flow.
Compressor is a wheel wich measure 2,80/2,09" (trim 56) in a A/R 0,50 house.

When it comes to what all the different Garrets is called it will depend of who you ask. At my diagram my compressor is called GT37, 56 * 0.50. T04E

J Chen

Duke post a compressor map. Is it the same
map that Edman posted ? The 60-1 is actually
a little big for the 2.5 unless you run it at higher
boost. Yes I now guys out there are gonna flame
me for saying this but !!!!!!

Corleone

To produce 450 hp it will take about 18,5 kg of air (41 lb/h). If you have a larger compressor like the 60-1 (can produce over 600 hp) people can feel that it will "push hard" because first when you hit the floor nothing happens, then nothing, then nothing and then everything and can hold boost at high revs. Can a car like that anytime be quicker? And how many of us can run higher boost than 22 psi all the way? They who has big turbos would have benefit to go down in size and increase the engines VE with better head, cam, intake, exhaust and so. It will produce a faster car.

J Chen

Hey Corleone,
Can you tell me more about your stage 9 ported
head & why theres some many stages ? Are you
running higher compression ratio ?

Corleone

Stage 9 is only a Joke because the "Americans" always counts in "stages".

I have Ferrera 48 mm intake valves with 7 mm shaft (lighter) and stock exhaust valves. Head is ported by a flowengineer who designs head at a big Swedish car producer (wich one can it be...?). Of course the seats is done. Then I have a Milledge cam (not at his website) and Milledge springs (uuhhh so hard) with titanium retainers. Runs great up 7500 rpmīs. But I will normally not go beyond 7ī.

Compression ratio is about 8,1.

Duke

So true, but soooo expensive

Duke

I don't know... those flow estimates seems too low, around 32 lbs/min of flow at 6500 rpm with 20 psi of boost?


Here's the map of the T61


And comparing that to the map overlay TonyG in another thread the T61 looks like an alternative:

Corleone

Hmmm, didnīt think of that...

More fun, more expensive... Life is always a matter of priorities