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andy 931 · Posted: Sun Jul 22, 2007 2:11 am Post subject: advise wanted

hi,i am looking for a bit of advice. i have recently purchased a 85 2.0 na
with the intention of building a lightweight fast road car for a bit of fun at the weekends . as practicality is not important with this one it is completley stripped out (ever removed the underboady sealant on one of these? its caked on, a 25kg saving tho!)
i have fitted fibre glass bonnet, wings, front pannel and replaced the glass with poly carbonate windows. trying to get weight down to approx 800kg!
i want a bit more power but without the extent of engine swaps or capacity increse . im looking for 140 bhp +
any suggestions woul be appreciated.
thanks
andy
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1980 924 turbo blue/silver
1986 924s red
1988 944s black
1985 924 na blue

Lizard · Posted: Sun Jul 22, 2007 4:13 am Post subject:

to get 140bhp NA out of this car,

rebuild the engine with a turbo head, and custom pistons with say 10.5:1 or 11:1 CR, stage II camshaft, add ITBs, and convert to standalone EFI like megasquirt or VEMS
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3 928s,

andy 931 · Posted: Sun Jul 22, 2007 8:21 am Post subject:

is a 931 head realy required to reach around 140bhp?
_________________
1980 924 turbo blue/silver
1986 924s red
1988 944s black
1985 924 na blue

Scorpio · Posted: Sun Jul 22, 2007 10:23 pm Post subject:

hey Lizard would that increase to 140hp require a change to the tranny..gearbox etc..breaks aswell or can the stockNA handle it?..mainly asking for road worthy reasons..
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1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT

Brisbane , Australia
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all youll see is
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924RACR · Posted: Sun Jul 22, 2007 10:35 pm Post subject:

I don't think it's necessary; I'm creeping closer to 130hp crank (on the racecar) with stock head and CAM, little more than a header. The cam is a big issue with these cars, apparently you can really free up a lot of power if you reprofile. Frankly, I hold out some hope that I can maybe, eventually, with some expert direction, get this thing nearer 135hp.

There's other internals stuff done to my motor, admittedly, but it's a pretty limited rebuild, by the rules; 9.5:1 CR, .040" overbore, Total Seal rings, and balanced and blueprinted lower end. No real tweaking of the head allowed, just a minor port match and a performance valve job. I do have a cam advance key, 4 degrees, but a proper cam grind should eliminate the need for that.

So my recommendations would be a good header and exhaust, rebuild and bump the compression to maybe 10.5:1 (to make it manageable with street gas), definitely balance and lighten up the rotating assembly and flywheel a bit (or Al. Fidanza flywheel). Performance valve job, some port-matching, not sure I'd go whole hog on porting the entire head though... larger throttle body... and yes, I agree, some kind of modern programmable EFI conversion - I'm going to do a Megasquirt, eventually.

Then some dyno tuning time.

I expect a fresh rebuild on the trans and torque tube may be needed, but 140 isn't THAT much... if you did find it to be a problem, I'd switch over to a 944 box and torque tube - that's designed for 150hp stock (at least in US trim, probably more over there).
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Vince Ponz · Joined: 02 Nov 2002 Posts: 3581 Location: Florida

Mild cam, headers, Euro pistons which you have, MSD ignition, Webers and I think I have about 135. I lightened the car also. You started with 125 hp and the stock euro pistons.

Not hard to reach.
_________________
"Never let them see you sweat"
77.5 924 modified track car
79 931 Euro stock
88 924S SE
87 911 Targa stock

andy 931 · Posted: Mon Jul 23, 2007 12:42 am Post subject:

cheers guys, as with regards to compretion increse, whats your vews on skimming the block buy 2mm,1 mm being the norm. i have heard of this being done but at what cost on reliabilty?
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1980 924 turbo blue/silver
1986 924s red
1988 944s black
1985 924 na blue

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

Where did you get the fibreglass panels from, Andy? Is the qualiity any good?
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

Lizard · Posted: Tue Jul 24, 2007 7:55 am Post subject:

scorpio, 924Racr aka Vaughan answered your questions nicely.

If you are going to do it, imo do it fully. You may get more than 140bhp out of what I have suggested but it is hard to say.
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3 928s,

seanski44 · Joined: 13 Mar 2006 Posts: 532 Location: Nottingham UK

or get your N/A head modded to remove that 'corner' the air has to go round!!

now, my knowledge is limited about these things, but don't go for HP and sacrifice torque!!

_________________
1998 BMW Z3 2.8 arctic silver & red

1981 168HP 931 S2 blue/tan leather - SOLD

1985 121HP 924 2.0l na modded - SOLD!
1992 968 lux SOLD
1989 944 2.7 lux SOLD