Rennlist - Porsche Discussion Forums

Notices
928 Forum 1978-1995
Sponsored by:
Sponsored by: 928 Specialists

The Twin Screw Thread

Thread Tools
 
Search this Thread
 
Old 11-08-2015, 12:23 AM
  #2521  
BrianG
Addict
Rennlist Member
 
BrianG's Avatar
 
Join Date: Jul 2002
Location: Edmonton, Ab
Posts: 2,286
Likes: 0
Received 0 Likes on 0 Posts
Default
Is anyone making a larger diameter crankshaft pulley?

Name: Almost2_zps3f541a48.jpg Views: 140 Size: 68.7 KB
BrianG is offline  
Reply Like
Old 11-08-2015, 02:50 AM
  #2522  
MjRocket
Drifting
 
MjRocket's Avatar
 
Join Date: Oct 2012
Location: Fort Wayne IN.
Posts: 2,157
Likes: 0
Received 3 Likes on 2 Posts
Default
I wish...I've been looking for a while.
MjRocket is offline  
Reply Like
Old 11-09-2015, 01:16 PM
  #2523  
Chris Lockhart
Rennlist Member
 
Chris Lockhart's Avatar
 
Join Date: May 2001
Location: Taylors, S.C.
Posts: 2,150
Received 10 Likes on 7 Posts
Default
I'm looking at having a local machine shop I deal with through work make one for me. Not sure what amount to increase the diameter? Trying to remember while here at work, but I was thinking that it was right at 5 inches. So, how much change would increasing the OD to 5.250" make? I need my pulley ratio formula, dangit.
Chris Lockhart is offline  
Reply Like
Old 11-09-2015, 01:31 PM
  #2524  
Imo000
Captain Obvious
Super User
 
Imo000's Avatar
 
Join Date: Aug 2003
Location: Cambridge, Ontario, Canada
Posts: 22,846
Received 339 Likes on 245 Posts
Default
You don't want to over spin the accessories too much.
Imo000 is offline  
Reply Like
Old 11-09-2015, 01:37 PM
  #2525  
MjRocket
Drifting
 
MjRocket's Avatar
 
Join Date: Oct 2012
Location: Fort Wayne IN.
Posts: 2,157
Likes: 0
Received 3 Likes on 2 Posts
Default
Originally Posted by Chris Lockhart
I'm looking at having a local machine shop I deal with through work make one for me. Not sure what amount to increase the diameter? Trying to remember while here at work, but I was thinking that it was right at 5 inches. So, how much change would increasing the OD to 5.250" make? I need my pulley ratio formula, dangit.
Let me know what you come up with and cost, i would be interested as well. Contact Hans or Colin (lizard) to get a good ratio. I had the #'s before but misplaced them.
MjRocket is offline  
Reply Like
Old 11-09-2015, 04:01 PM
  #2526  
victor25
Rennlist Member
 
victor25's Avatar
 
Join Date: Oct 2009
Location: Michigan... Grand Rapids
Posts: 758
Likes: 0
Received 2 Likes on 1 Post
Default
the stock crank pulley is apx 5.50 inches in diameter. I would go to 6.5 or 7inch. This will give you a 20% to 30% increase
victor25 is offline  
Reply Like
Old 11-09-2015, 04:12 PM
  #2527  
MjRocket
Drifting
 
MjRocket's Avatar
 
Join Date: Oct 2012
Location: Fort Wayne IN.
Posts: 2,157
Likes: 0
Received 3 Likes on 2 Posts
Default
Originally Posted by victor25
the stock crank pulley is apx 5.50 inches in diameter. I would go to 6.5 or 7inch. This will give you a 20% to 30% increase
Excellent!!
MjRocket is offline  
Reply Like
Old 11-09-2015, 04:45 PM
  #2528  
Darien
Rennlist Member
 
Darien's Avatar
 
Join Date: Dec 2004
Location: Fort Worth, TX
Posts: 2,649
Received 245 Likes on 109 Posts
Default
Hmm.
Darien is offline  
Reply Like
Old 11-09-2015, 05:25 PM
  #2529  
Glen McCartney
Rennlist Member
 
Glen McCartney's Avatar
 
Join Date: Feb 2002
Location: Allentown, PA
Posts: 1,235
Received 36 Likes on 15 Posts
Default
Hmm Darien, need more power in rocket? It can't keep up with the Cayenne?
Glen McCartney is offline  
Reply Like
Old 11-09-2015, 10:56 PM
  #2530  
AO
Supercharged
Rennlist Member
 
AO's Avatar
 
Join Date: May 2002
Location: Back in Michigan - Full time!
Posts: 18,925
Likes: 0
Received 60 Likes on 34 Posts
Default
Originally Posted by victor25
the stock crank pulley is apx 5.50 inches in diameter. I would go to 6.5 or 7inch. This will give you a 20% to 30% increase
It's not that simple. You also need to think about the speed at which your SCer will spin. At a certain point you will exceed the VE and the physical specs for your SCer. IIRC most of the Twin-screws don't like to spin beyond 18k RPMs. If you're already spinning at 16k RPMs, if you increase the crank pulley size, you could end up with a SCer spinning at 20k and killing the seals... I know.

As for a larger pulley, Hans had mentioned doing something, but not sure if it would work on a Keel kit or if he went through with it. Murf also makes a custom crank pulley that is quite a bit larger that the stock one, but again, not sure if would work for the keel kits.
AO is offline  
Reply Like
Old 11-09-2015, 11:08 PM
  #2531  
MjRocket
Drifting
 
MjRocket's Avatar
 
Join Date: Oct 2012
Location: Fort Wayne IN.
Posts: 2,157
Likes: 0
Received 3 Likes on 2 Posts
Default
What does Murph's cost?
MjRocket is offline  
Reply Like
Old 11-09-2015, 11:13 PM
  #2532  
worf928
Addict
Rennlist Member
 
worf928's Avatar
 
Join Date: Oct 2003
Location: Gone. On the Open Road
Posts: 16,496
Received 1,638 Likes on 1,069 Posts
Default
Originally Posted by AO
It's not that simple. You also need to think about...
And won't you spin the alternator to death with a bigger crank pulley? I seem to recall that our alternators don't like to spin too much faster than they already do at red line? Where's Alan...

Originally Posted by MjRocket
What does Murph's cost?
Not a twin-screw. Wrong thread.
worf928 is offline  
Reply Like
Old 11-09-2015, 11:16 PM
  #2533  
AO
Supercharged
Rennlist Member
 
AO's Avatar
 
Join Date: May 2002
Location: Back in Michigan - Full time!
Posts: 18,925
Likes: 0
Received 60 Likes on 34 Posts
Default
Originally Posted by MjRocket
What does Murph's cost?
Dunno. Ask him. I do know it is the 2nd most expensive piece of his kit. 1st is the Scer.
AO is offline  
Reply Like
Old 11-09-2015, 11:21 PM
  #2534  
worf928
Addict
Rennlist Member
 
worf928's Avatar
 
Join Date: Oct 2003
Location: Gone. On the Open Road
Posts: 16,496
Received 1,638 Likes on 1,069 Posts
Default
Originally Posted by AO
Dunno. Ask him. I do know it is the 2nd most expensive piece of his kit. 1st is the Scer.
Oh. He meant the crank pulley. I though he meant the whole kit.

Sorry MJ.
worf928 is offline  
Reply Like
Old 11-10-2015, 08:45 AM
  #2535  
Darien
Rennlist Member
 
Darien's Avatar
 
Join Date: Dec 2004
Location: Fort Worth, TX
Posts: 2,649
Received 245 Likes on 109 Posts
Default
LOL. I'm good with my 12lb pulley


Originally Posted by Glen McCartney
Hmm Darien, need more power in rocket? It can't keep up with the Cayenne?
Darien is offline  
Reply Like



Advanced Search
Quick Reply: The Twin Screw Thread


Reply Closed Thread Share
Forum Jump

All times are GMT -3. The time now is 06:26 PM.