|
Author |
Message |
Director
Moderator
Joined: Nov 05, 2009 Posts: 1634 Location: Isle of Palms, SC
|
Provost wrote: When looking into a cylinder with a bore scope the 9.5 pistons are flat and the 10.5 are not. As far as the after market dished ones I have no quick way of telling. So is there going to be a prevision in the rule's(PCA) for aftermarket pistons? This is so complicated and should not be.....open for suggestions. The 944 Cup has always allowed aftermarket pistons. Too late to back up on this. Also, much more expensive to buy or build with factory pistons : viewtopic.php?f=10&t=2119
_________________Dave Derecola National Director 944 Cup cup944@aol.com
|
Thu Dec 20, 2012 8:21 pm |
|
|
Director
Moderator
Joined: Nov 05, 2009 Posts: 1634 Location: Isle of Palms, SC
|
Provost wrote: Problem with the wistler is atmospheric pressure. Compresion readings will change at different altitudes. There is a chart for this but we are getting way complicated.... There are numerous factors that can effect the whistler. As I understand, PCA has a trained tech in charge of its use. But like the dyno, there just isnt any perfect solution. I am trying to write the rule so that half the field last year isnt illegal but still sets a reasonable limit attainable by all and that can be reasonably enforced. If you talk to 5 engine builders, you get 3 different answers, and the other two won't give you an answer. It's not an exact science.
_________________Dave Derecola National Director 944 Cup cup944@aol.com
|
Thu Dec 20, 2012 8:31 pm |
|
|
DrFranz
Driver
Joined: Nov 23, 2009 Posts: 204 Location: New York, NY
|
Provost wrote: Problem with the wistler is atmospheric pressure. Compresion readings will change at different altitudes. There is a chart for this but we are getting way complicated.... Would it really? The tracks we run at all have to be within, say, 500' of each other in terms of altitude, I would think. Unless we're having an event at Mexico City, I don't think this would come into play, would it? Just interested, and wondering.
_________________ SuperCup #57, National Champion 2011 and 2012 www.frankcelenza.com/racing.php
|
Thu Dec 20, 2012 10:57 pm |
|
|
wormhole
Rookie Driver
Joined: Mar 08, 2010 Posts: 10
|
Quote: There are numerous factors that can effect the whistler. As I understand, PCA has a trained tech in charge of its use. But like the dyno, there just isnt any perfect solution. I am trying to write the rule so that half the field last year isnt illegal but still sets a reasonable limit attainable by all and that can be reasonably enforced. If you talk to 5 engine builders, you get 3 different answers, and the other two won't give you an answer. It's not an exact science. You can use a car or seriers of cars as a baseline for environmental variables. If everyone is a tenth of a point over then it's a safe bet on the machine. If everyone is within range and one car is half a point over then there is a problem with that car. John
|
Thu Dec 20, 2012 11:21 pm |
|
|
Director
Moderator
Joined: Nov 05, 2009 Posts: 1634 Location: Isle of Palms, SC
|
I sent over to PCA what I hope to be the final version of the rule change covering compression ratios and the cylinder head. I accepted the PCA version, one that has been endorsed by some techs that I would have confidence in as valued members of the 944 Cup community, setting the CR limit of 10.6 for the 2.5L and 10.9 for the 2.7 L . Truing of cylinder heads with compensating head gasket is allowed, as long as the compression limit listed here is not exceeded. Aftermarket pistons will be allowed.
The CR values for SP3 were already included in the rules for 2012. Added was truing of cylinder heads with compensating head gasket is allowed, as long as the compression limit listed is not exceeded.
_________________Dave Derecola National Director 944 Cup cup944@aol.com
|
Thu Dec 20, 2012 11:39 pm |
|
|
Provost
Rookie Driver
Joined: Nov 15, 2011 Posts: 51
|
Sounds good Dave ..... I think it is important to allow aftermarket pistons...For those who think they are illegal we did the math and if you do a simple compression test and don't go over 197-199 psi you should be in the ball park for 10.6-1...... 200 plus your over. We have seen some heads come threw here cut so far down that they were around 13.5 to 1
_________________ Robbie Provostmotorsports.com
|
Fri Dec 21, 2012 8:26 am |
|
|
Director
Moderator
Joined: Nov 05, 2009 Posts: 1634 Location: Isle of Palms, SC
|
Provost wrote: Sounds good Dave ..... I think it is important to allow aftermarket pistons...For those who think they are illegal we did the math and if you do a simple compression test and don't go over 197-199 psi you should be in the ball park for 10.6-1...... 200 plus your over. We have seen some heads come threw here cut so far down that they were around 13.5 to 1 Thanks for the info Robbie. That should help our drivers get some idea where their motors are. I quick measurement of the head may also give them an idea how much the head has been milled, using the specs provided by Wormhole. PCA has confirmed the changes we are making to the Cup rules. Hope to have the finals version posted in the next week or so.
_________________Dave Derecola National Director 944 Cup cup944@aol.com
|
Fri Dec 21, 2012 8:50 am |
|
|
cris.brady
Rookie Driver
Joined: Nov 09, 2009 Posts: 84 Location: Landenberg, PA
|
Provost wrote: Sounds good Dave ..... I think it is important to allow aftermarket pistons...For those who think they are illegal we did the math and if you do a simple compression test and don't go over 197-199 psi you should be in the ball park for 10.6-1...... 200 plus your over. We have seen some heads come threw here cut so far down that they were around 13.5 to 1 Hey Robbie, what would be the compression numbers for a 2.7L?
_________________- Cris #88 1989 944 NA Tales from the Dark Side of Racing
|
Fri Dec 21, 2012 9:22 am |
|
|
Director
Moderator
Joined: Nov 05, 2009 Posts: 1634 Location: Isle of Palms, SC
|
_________________Dave Derecola National Director 944 Cup cup944@aol.com
|
Sat Jan 12, 2013 11:58 pm |
|
|
Who is online |
Users browsing this forum: No registered users and 10 guests |
|
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot post attachments in this forum
|
|
|