924Board.org

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

Hi Steve!

Tell me more about your Wössner pistons. If they're custom, did you get some kind of part no with what you can order them more?
How much were they approximately?
I've heard good things about Wössner pistons, but I also heard (from very respectable source) that they use very crappy rings by default and it's useful to use different piston rings....
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'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

bass gt · Posted: Thu Jan 25, 2007 10:02 am Post subject:

Raceboy,

The pistons are totally custom, as i will be using Cosworth steel rods, which have a very similar big end, nearly identical small end, but a different length. They are a little longer, which means reducing the crown to wrist pin length, which is a good thing. Also, being Cosworth items, ARP bolts are a snip to get. Funnily enough, i am going to get a couple of sets made. Although the price obviously goes up, the effective price per piston drops significantly. These will also be ceramic coated.
regarding the rings, i have not heard anything negative, but then again, i have not heard anything positive either!! I usually presume that no news is good news.
As i was having the slugs custom made, i took the opportunity to have them fit a good quality, easily available rod, such as the Cosworth.
So if anybody else was interested, it would mean changing out the rods as well. obviously not cheap.

Steve

Racing · Joined: 27 Apr 2004 Posts: 374

Hiya guys!

Being one of those that has actually run the VW slugs with at least fair results let me fill in the following.

As far as dished slugs vs flat tops as well as the topic of quench areas.

It is boost dependant.

The higher the boost,the less the need for "artificial" ways of promoting turbulence.
IOW..when i was running my motor with the VW slugs i was running higher levels of boost for those that remember(around the 2 bar mark for those that recall),which resulted in no ill effects from that rather "low tech" setup the open chamber solution brings.
All in all it worked like a charm,so in essence Nick et al...just go ahead...you guys will be just fine.

That 3ccs of removed material would make for a world of difference...yeah yeah...and pigs fly as well as santa exists.

On the topic of the slugs themselves i found them of decent quality(had the head off a couple of times due to other issues) to check,and indeed had pinging marks on the piston crowns on occasion due to overly agressive timing at one point.
Structural integrity of the slugs per se was just fine though.

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

Hey Racing - how is yours holding up nowadays? Still pushing 2bar with regularity? Any dyno charts of the latest incarnation? From what I remember your earlier dyno numbers were from an older incarnation.
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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

Racing · Joined: 27 Apr 2004 Posts: 374

Nick.
The 931 is long since gone.
Last couple of years i´ve been into the old cosworth mercedes 2,3-16s.
Not without success,and i´m currently putting another plant together for my own 16V merc.
This time out a little more balls to the walls,with reinforced/stressbored asf block,Bofors crank,Verdi rods and modded forged Mahles for a Volvo(originaly at least)
Head is full of a mix of ferrea and home brew titanium stuff,and ...yup...shooting for 2 bars of pressure out of the 64mm inducer and power slit compressor.
Hope for 650-700hp that way.

Lizard · Posted: Fri Mar 02, 2007 12:59 pm Post subject:

leadfoot · Posted: Sun Mar 04, 2007 11:50 am Post subject:

Well I finally got my car back from the dyno shop....
The car is making 128.6RWHP on 4.8 psi...
So the extra bore increase has dropped boost a bit over 3 psi... It's seems the new supercharger manifolds have reduced the gap between pre and post intercooler boost measurements though.
I'm happy with how the car feels at the moment... although after having just had the steering column intermediate shaft replaced I'm a little annoyed that I think my booster has chucked in the towel now too... So I have only driven it back from the shop, not taken it out for a real drive.
My finances are well and truly blown at the moment so having a new sc pulley made up is well into the future.
Leadfoot
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

Wow! Dropped over 3psi of boost. This is actually very good news as I'm sure you know. It means you have uncorked a HUGE bottleneck being namely the head I think. I imagine the little bit of bore increase had some effect but head flow has to be the biggest reason for the drop.

The increased bore probably helped flow too by unshrouding the valves.

I don't remember what your prior dyno numbers were. Could you remind me?

Your new intake can probably take some of the credit too.

This puts another nail in the coffin of the NA head in boosted applications

Todd

BTW, you may want to budget a new clutch to go with that new pulley

_________________
'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!....

leadfoot · Posted: Sun Mar 04, 2007 2:46 pm Post subject:

previous dyno was 126RWHP, almost identical power but at 3.2psi more pressure.
My idle has smoothed a little, no increase in vaccuum though, that would be the cams doing... I'm still running with the sc clutch too...
I should be able to add a decent amount of RWHP with an increase in boost now the foundations are laid down...
It will be nice to get back into the car once the brakes are sorted...
Leadfoot
_________________
1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

Hmmm, I definitely smell fun and clutch in your future

Todd
_________________
'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!....

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

sounds great ! but whats a SC pulley cost over there...here its 50$-70$ max.

A G60 friend had one made in one day for 30EUR using his piece of aluminium.
_________________
Supercharger and EFI kits
https://www.the924.com

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

N-Dub · Posted: Tue Mar 06, 2007 8:44 am Post subject:

Electronic clutch pulley??? Like on the car in Mad Max? I'm not trying to be sarcastic, just wondering.
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'79 924 now Totaled! Carrera GT bodywork for sale!
'87 951

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Here's Leadfoot with an early prototype.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

Good one there Rasta!!

I should let Leadfoot answer but I'll do it anyway

N-dub, it is pretty much just like that except I think Leadfoot has his setup to come on at a certain load or RPM. It bypasses air around the blower when it is off. I guess there have been several stock vehicals with this clutch setup. I'm not sure what Leadfoots came from but I seem to remember it was a Toyota of some sort. Could be wrong.

Todd
_________________
'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!....