944 turbocharger options

stv951 · Jul 8, 2014

Need your ideas on choosing a turbocharger on an engine that I am building.

I want to have the best possible throttle response and low turbo lag and dont really mind going for crazy hp numbers. I am happy with 320-330 reliable whp but want mid range punch

What options are there to choose from aside the original k26-6 or k26-8 ?
Is there a Garrett unit that can be modified to fit on the stock 951 header ?

I see lots of Japanese cars utilizing various units with great results

Anyone has done something similar ?
Engine will be 2,5 951 not 2,8 or bigger

It is going in a lightweight 924 Carrera GTS recreation I am completing

TIA

Steve

Lowtimer · Jul 8, 2014

330 at the wheels is about 380 at the flywheel. That is pretty top end for the 2.5l engine.

Jon Mitchell will, I am sure, be along to shortly with some options but I would have thought if you really want that much power with the best midrange, excellent throttle response and low lag that increasing the capacity would be a far mode effective way of getting there than relying on additional boost to do it all for you.

stv951 · Jul 8, 2014

ORIGINAL: Lowtimer

330 at the wheels is about 380 at the flywheel. That is pretty top end for the 2.5l engine.

Jon Mitchell will, I am sure, be along to shortly with some options but I would have thought if you really want that much power with the best midrange, excellent throttle response and low lag that increasing the capacity would be a far mode effective way of getting there than relying on additional boost to do it all for you.

You are right, but I see loads of cars making this short of power out of much smaller engines. How hard could it be to go to this level of power ?
I understand that I might need a MAF kit and also bigger injectors. Still though these engines should be able to reach that level of power with modern turbochargers and peripherals, no ?

TTM · Jul 8, 2014

ORIGINAL: stv951
Still though these engines should be able to reach that level of power with modern turbochargers and peripherals, no ?

Unless having some major expensive head work done, the answer is no.

stv951 · Jul 8, 2014

ORIGINAL: TTM

ORIGINAL: stv951
Still though these engines should be able to reach that level of power with modern turbochargers and peripherals, no ?

Click to expand...

Unless having some major expensive head work done, the answer is no.

So the head is the bottleneck ?
What needs to be done ? Flow development ? Bigger valves ? What else ?

Ewan · Jul 8, 2014

My Ghibli Cup makes 330 bhp from a 2.0 lt engine, and that's factory standard on a car that's now 18 years old. So you'd think that a bit more from a 2.5 lt lump with a modern turbo shouldn't be so hard. (Admittedly the Cup uses two turbos, not just one.)

944 man · Jul 9, 2014

Based on a domestic market 2.0l BiTurbo V6 Ewan? I had always presumed that they were a 2.8l until you said.

TTM · Jul 9, 2014

ORIGINAL: stv951
So the head is the bottleneck ?
What needs to be done ? Flow development ? Bigger valves ? What else ?

Flow development, but you will spend a fortune and a standard 16V head will still flow more.

PSH · Jul 9, 2014

Hi Steve

You will be able to get the figures that you have quoted from the 2.5 without much problem but it won't be cheap and it won't be quick in as far as time scale and R&D...If you check my build thread (building a 400+bhp 2.5 turbo) on the next page or two I have listed what my car had on her to reach your target figures. I'm not a great fan of bigger displacement, IMHO it takes away some of the liveness that the 944T has in bucket full's as a 2.5ltr. Looking at your signature it seems that you have a 944T close to this level already so I guess you must know a fair bit about what's needed?

regards

Pete

DavidL · Jul 9, 2014

I'm sure Jon M said that a 400bhp 400ft/lb engine is quite possible from a 2.5 engine and is the end of the road for that size. After that you're into 3.0 and 3.2 engines.
Not cheap but quite doable.
Turbos - again Jon has developed his own after looking at what is on the market. Things like the LR super 61.

http://www.pistonheads.com/doc.asp?c=161&i=30031
this gives the goss on the 2.0 ghibli cup cars. I believe the cup cars had the 2.0 engine and the stock UK ones the 2.8 but Ewan will put me right, he's had them all several times over!

Diver944 · Jul 9, 2014

Let's not forget that his intended target of circa 380 bhp is at the flywheel. Trying to get that from a 2.5 with minimal lag and lots of midrange will be difficult or very costly, especially if you don't want to be rebuilding it every 10,000 miles

You will need a large bore exhaust, a ball bearing turbocharger and a MAF (or MAP) setup with either standalone or piggyback to control it. The head will need a lot of work to make it flow (or go 16v as Thom has said) and you will need a very efficient intercooler to try and keep all the heat down because you will need to be running around 1.4bar boost.

What is the intended use of the car? Day to day driver, track beast or Dyno queen?

Lowtimer · Jul 9, 2014

Which beg the question: why not do it a lot cheaper and with far better tractability and throttle response by using a larger capacity bottom end? You will need a fully rebuilt bottom end anyway, if you are investing a pile of cash in a 380 hp engine...

Ewan · Jul 9, 2014

ORIGINAL: 944 man

Based on a domestic market 2.0l BiTurbo V6 Ewan? I had always presumed that they were a 2.8l until you said.

The Cup was based on the Open Cup race car of 1996 and quite different to the standard Ghibli of the day. So a 2.0 lt engine, different turbos, Brembo brakes, lowered suspension, etc.

Mike_Pollock · Jul 9, 2014

The most straight forward way of getting those results is give Lindsay Racing in the States a large wad of cash, should be reliable too. MarkK's is 400 at the flywheel and 8 years converted, regularly used and still flies.

T3rra · Jul 10, 2014

I'm running gtx 3071 with tial 0.63..see sig for most mods. Currently stock engine. Not sure what bhp I'm at as iv not dyno car or had tom do final mapping.

But from my data logs I can tell you iv got spool up as quick or quicker then 26/8 key. Didn't get data logs for 26/8 which I can cross reference to. 60/100mph is 4.5 secs I'm on full boost 1.3 pretty much gear + 2 X 10 so 3rd gear is 3+ 2 X 10 50 mph

Of course I would like some head work. If you want to run lower boost your have to go for 3076 0.82 which makes around 40hp more per boost level but takes 400 rpm to spool. Still got boost by 60 in 3rd

Ex Skyline · Jul 10, 2014

I'm aiming for 400+ from my 2.5ltr. Jon' will be doing the work. However, will that be achievable from my 8 valve head or,
would I have to go for a 16v head? If it is achievable, what would the benefits be from going with a 16v head anyway [8|]??

George Elliott · Jul 10, 2014

I would be confident Jon could get you 400 with the 8v.

Whats the advantage of a 16v, ask Jon, I think maybe there are very few advantages. An 8v with valve work and the right cam has considerable potential assuming Intake, Exhaust, IC, Turbo, Fuel & ECU are optimised, and Balancing, Oiling, Rods, Cooling and drivetrain are up to scratch.

400 should be a nice package

Keep us posted

George
944t

Diver944 · Jul 10, 2014

400 from an 8v is entirely possible and has been done several times by cars on this forum, but not with minimal lag and mid range punch as Steve has requested. There is a thread about 6-7 years ago about a Turbo Cab that Jon built for a customer that tested at 416:

http://www.porscheclubgbforum.com/tm.asp?m=371395&mpage=1&key=powerful

I got the chance to drive it in the damp (eek [

]) and once the turbo had spooled up it was frighteningly fast, but had a very on/off delivery - not what Steve is looking for

PSH · Jul 10, 2014

keep the 8 valve head Pete.. I hate 16 valves... no low down torque and far too much throttle needed to get going in comparison... ok for the race track when the engine is screaming it's nuts off 90% of the time but who wants that for a road car? not me...

Pete