924Board.org

Zuffen · Posted: Sun Jun 26, 2005 4:37 pm Post subject:

Are you kidding?

it is an authentic GTS, not a GT , not a GTR,

this car is the 2nd maybe third rarest form of the 924 in a factory configuration

and the "smudge" is a reflection in the paint job

Need a history lesson on the G series cars, read the 924 site for more info.

Any questions and I'll be glad to clarify.

Bob
_________________
Bob Dodd - 924turbo@cox.net
931 1982, 944 1982 euro, 924S 1988SE, 93 968 tip 06 Silver Cayenne S, 06 Black Cayenne S

I have Way too many cars, parts for the 931,944 and 951

Racing · Joined: 27 Apr 2004 Posts: 374

By all means then...

Thanx for the vote of confidence cbass...

Having read the thread...at one point you want a "real" GTS,and then later down you´re just in it for the performance?
What gives?
If the latter thing is your cup of tea...then no problemo.
Why?
As any engine the 931 power plant can be made to perform.
Basic drawback of the engine per se is the cylinder head(and i´ll be happy to go into an argument bar none there),but the engine can be made to handle around the 400 mark if willing to spend some time and money.

First thing that needs to go is the head gasket,they simply fail(cant take the cyl pressure at the boost levels needed to make power),and it needs to be replaced with either a shimmed steel one or a solid copper one.
Next thing up that NEEDS to go out the door is the OEM pistons.
Dauuyyyym boyz,i´ve come to wonder if the factory actually made the molds to hold marshmallow dough at the factory!!!
They simply SUCK! Who in their right mind puts cast slugs into what´s supposed to be a non intercooled high performance engine??

Anyways...
That´s about it.
The OEM crank..the block..the connecting rods...looks like they´re built to handle a damn tank.
I used common off the shelf dirt cheap universal forged VW slugs for mine.Just rebushed the small ends of the conn rods to 22mm and were done with it.
Set the piston to wall clearance up a little loser than normal(approx3/100 of a mm more worth)and went to business.

Some people have come down on the OEM cast exhaust manifold.
That sure beats me,cause i for one have used EGTs and p1/p2 measurements of pressure diffs asf,and have have seen NO ill effects.
As i didn´t dyno my engine..have no idea of power output,but it performed-i´ll tell you that much.(at 2 bar we peaked just over 900deg C at one time,otherwise we were down at 850sh figures)
Used a K27 hybrid and a max boost of 1,8 bars that actually reached inxs of 2 at occasions.
Intercooler was one we welded up out of a spearco element-made to fit.At 1,8 bars that left us with an intake temo out of the cooler of 36 deg

As most on here know we ditched the OEM intake to at least get rid of one plug within the system,and...yeah well we had positive results from that too.
Especially so in the none boosted areas of the engine,and as far as difference at full boost...honestly no idea.
Made that up from a 70mm Alfa throttle housing.

The head IS a plug...
Those minescule little valves and ports do indeed hinder performance,and if u take a look at how contemporary engines are built today...you´ll get an idea how the enormous amounts of power is extracted.
Power,as always,is to be found within the head.
Some time has passed...and frankly,were i in it for the performance...
Today,like stated in another post...
I´d swap an Audi 20V engine in there and be done with it.
Admitted...making the 931 engine haul is a hoot...
But,from a PURE performance standpoint...there´s no need to have sex standing on your head in a canoo in a raging river everytime..
In my book the Audi engine would be a MUCH better choice with a performance potential that´s unreal from a 931 perspective.

Manning · Joined: 29 Feb 2004 Posts: 151 Location: Akron O-Hi-O

porsche9866 · Joined: 22 Jun 2005 Posts: 13 Location: eijsden

can you some one please line up al things what i can do from what really nesecariy is to things what not much hp give. it is mix up

morghen · Joined: 21 Jan 2005 Posts: 9095 Location: Romania

whats the max BHP that a 931 with boost control and minor tuning ?
_________________
Supercharger and EFI kits
https://www.the924.com

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

It depends on what you consider minor tuning.

An intercooler, boost controller and an air filter should get you to around the 200hp mark safely.

Other things that would be nice to have would be EFI, such as Megasquirt or one of the more expensive programmable units, cylinder head work such as porting, larger valves, higher lift camshaft etc...

If I was to build a motor to reach the 275hp of the GTS clubsport, I would build it with the following.

A good intercooler, one made to fit based from an aftermarket core, or an Isuzu NPR core.

Electronic fuel injection, my pick would be Megasquirt for it's low cost and ease of use.

Mandrel bent 2.5" exhaust, removal of cat(if equipped) into an absorbtion style muffler, most likely a Borla, since they are the highest flowing absorbtion mufflers.

Cylinder head port matching and a "cleanup" of hte ports, removing all casting marks, grinding the valve guides flush, contouring the short side of the bowl a bit, and back cutting the valves slightly. For this level, you don't need oversize valves, but a camshaft with a little more duration and a good bit more lift would help.

Forged pistons in a rebuilt bottom end, with all components thoroughly checked for wear and damage.

That's all pretty easy to figure out, but I'd be worried about the turbocharger at this point. I don't think the K26/#6 can support quite that much airflow, but I could be wrong. I really have no idea when the K26 is going to run out of breath.

If I were to build a new turbo manifold, after spending much time thinking about it, I would do what Porsche themselves did when turbocharging the 944, I would make a 4-2-1 header out of stainless steel, and route it to the other side of the engine bay, where the intake manifold is. This leaves plenty of space, especially for routing hoses. With a clean sheet of paper, you could also use any flange you wanted, opening the door to a whole selection of cheaper, more modern turbos. A ball bearing Garrett turbo can spool faster than, and still provide more airflow than the old thrust bearing K26.
_________________
'81 931 in various states of assembly

porsche9866 · Joined: 22 Jun 2005 Posts: 13 Location: eijsden

why don't use the efi of the 944 ore 928. And could you not mount a k27 insteade of the k26 (911 turbo)??? when you install the efi of the 928 you have 8 injectors 4 were the original sat and the other 4 you can drill holes in the intake and mount them there. and when you do all these things---------->
''If I was to build a motor to reach the 275hp of the GTS clubsport, I would build it with the following.

A good intercooler, one made to fit based from an aftermarket core, or an Isuzu NPR core.

Electronic fuel injection, my pick would be Megasquirt for it's low cost and ease of use.

Mandrel bent 2.5" exhaust, removal of cat(if equipped) into an absorbtion style muffler, most likely a Borla, since they are the highest flowing absorbtion mufflers.

Cylinder head port matching and a "cleanup" of hte ports, removing all casting marks, grinding the valve guides flush, contouring the short side of the bowl a bit, and back cutting the valves slightly. For this level, you don't need oversize valves, but a camshaft with a little more duration and a good bit more lift would help.

Forged pistons in a rebuilt bottom end, with all components thoroughly checked for wear and damage. ''

have you got then 275 hp i think you have less.

morghen · Joined: 21 Jan 2005 Posts: 9095 Location: Romania

dude...forged pistons, higher cams, high compression engine with turbo will give you as much HP as you want...a 10:1 forged engine with a turbo jumps over 400 HP these days....so why do you think that 931 with all those changes wont jump over 260 HP ?
_________________
Supercharger and EFI kits
https://www.the924.com

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

I really don't think the combustion chamber design will take high compression + boost like modern engines can. Not to mention, you'll need to tune the fuel requirements and spark as a function of rpm & map, which means a stand-alone in our cars. Grafting a 944 or 928 fuel system is pointless.

I think 275hp with the above changes is a little optimistic, but not out of reach. I'm running basically all of the above and I'm shooting for a rock solid and reliable 250hp.

In addition to the above, if you want to go higher you're going to need to play with the turbo (which can be tricky since you can only easily change compressor wheels; the bearing and exhaust housings are unique to the 931).

Remember, the amazing numbers of the GTS/R cars are likely in a very narrow power band (they're race cars after all), and longevity of those kinds of engines is measured in hours, not miles- literally.

Anyway, this thread gives a good starting point for making real power from the 931. Anything more, and you need to start studying and designing, rather than asking questions.

nick

Racing · Joined: 27 Apr 2004 Posts: 374

Nick...are you ever right...

..and that´s exactly my point.
Ya know...sorta like the story of the sows ear.

Speaking of which-for our young friend here.
Yeah.
I was running the K27 compressor.
Worked like a charm.
Exhaust was a built full 3"

Racing · Joined: 27 Apr 2004 Posts: 374

btw.
275hp on the stock unopened engine...
Sorry guys,but i dont see that happening...
Be happy to be contradicted tho...

Raceboy · Joined: 01 Mar 2004 Posts: 2327 Location: Estonia, Europe

400hp on a totally overhauled engine (forged pistons + copper hg) can be made reliable, without a doubt, not for couple of hours but thousands of kms (asked Racing about total mileage of his well-performing 931, it was somewhere around 5000) There's something to consider...

Anyway, I have taken the challenge to find the absolute limits of 931 engine (specifically head) and we'll see. I have aforementioned bottom end, 931 head with slightly modified comb. chamber (smoothed edges, port matching) and healthy rebuilt K26/28 hybrid turbo that has 83mm K29 comp. wheel. That huffer is capable of app. 600hp. and we'll see the limits of 931 head, I promise. I plan to get tha car running at the end of that summer, maximum power (=standalone EMS install) somewhere later. Hopes are on Jesper (Racing) to setup this

Why so late on the engine reinstall? It's because I swapped the whole 931 thing to a '84 924 NA chassis (due to galvanized body, 944-type heater system, better shape etc).
Haven't told about this yet.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold

'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

Raceboy · Joined: 01 Mar 2004 Posts: 2327 Location: Estonia, Europe

Fuel is 98 RON and no point in worrying about rods, those are strong.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold

'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche