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

Later 928 running hot? Maybe this is why

Thread Tools
 
Search this Thread
 
Old 07-13-2010 | 06:08 PM
  #46  
mcholdfast's Avatar
mcholdfast
Three Wheelin'
 
Joined: Mar 2006
Posts: 1,489
Likes: 1
From: Happy To Be Home in Sumter, SC
Default

Originally Posted by VehiGAZ
Mike, were you running with the belly pan/undercarriage tray/whatever you want to call it installed in those conditions?

I wouldn't care if the temp ran to the top of the range - I just don't want it over-heating.
Yes, it has a metal belly pan installed and flaps removed. I was in stop and go traffic through downtown Atl a couple of weeks ago with the A/C on. It climbed about the width of the pointer above the last white line and stopped there. Just enough to make me nervous but no overheating. Once I got going again, it cooled off a bit. The temp outside was 102.
Old 07-13-2010 | 06:11 PM
  #47  
pcar928fan's Avatar
pcar928fan
Nordschleife Master
 
Joined: Apr 2008
Posts: 9,337
Likes: 4
From: Austin, TX
Default

Originally Posted by Erik N
Ideal Gas Law: PV=NrT

P= pressure
V= volume
N= # of moles (molecules)
r= constant
T= temperature

Pretty sure that's right. I learned it in 7th grade IIRC (but that was about 30 years ago)

If you learned THAT in 7th grade then it was a 7th grade for science/math prodigies!
Old 07-13-2010 | 06:33 PM
  #48  
dprantl's Avatar
dprantl
Thread Starter
Race Car
 
Joined: Dec 2003
Posts: 4,477
Likes: 4
From: Atlanta, GA
Default

I remember learning that in 2nd year too (that's the 7th grade equivalent in the english system).

Dan
'91 928GT S/C 475hp/460lb/ft
Old 07-13-2010 | 09:51 PM
  #49  
Erik N's Avatar
Erik N
Been selling Twinkies on Ebay,
have some extra cash right now.
Rennlist Member
 
Joined: Jan 2010
Posts: 6,746
Likes: 142
From: Working the street corner for $$$
Default

Originally Posted by Erik N
Ideal Gas Law: PV=NrT

P= pressure
V= volume
N= # of moles (molecules)
r= constant
T= temperature

Pretty sure that's right. I learned it in 7th grade IIRC (but that was about 30 years ago)

Originally Posted by dprantl
Too bad it doesn't also work for liquids Oh, and it's a small 'n' and big 'R'.

Dan
'91 928GT S/C 475hp/460lb.ft
Not to get off topic, but what is the law for liquids?
PV=nRT was at work (I thought) for example when gaining elevation and water then boils at a lower temp, or when you pull a vacuum in an A/C system to vaporize off condensation.
Old 07-13-2010 | 11:51 PM
  #50  
dr bob's Avatar
dr bob
Chronic Tool Dropper
Lifetime Rennlist
Member
 
Joined: Oct 2001
Posts: 20,506
Likes: 549
From: Bend, Oregon
Default

It's the perfect gas law, not the perfect liquid law. Steam is not quite a perfect gas. OK, nowhere close...
Old 07-14-2010 | 04:46 PM
  #51  
AngelP's Avatar
AngelP
Advanced
 
Joined: Jul 2003
Posts: 61
Likes: 6
From: Blairstown, New Jersey
Default

Ok folks here are my roundabout coolant temp. story. All coolant components original equipment except thermostat, and water pump -89 GT. It’s always run the same which is to say warm, typically about 1, perhaps a bit more, needle width with below the last white hash mark. Eons ago when I used to track the car it would run a bit past the last white hash mark but not overheat. It made me quite uncomfortable though. Next I need to set the stage with a seemingly unrelated aspect; For quite a while after getting Autothority chips I had a detonation issue, which was improved but not totally eliminated with a new rising rate fuel pressure regulator. Always used premium gas. One day an idea popped into me noggin’ and this went something like this; I’d always wanted to JET-HOT coat the exhaust manifolds to keep the engine bay as cool as possible and allow the engine to run more efficiently. So I reasoned that perhaps doing this would not only allow the engine to run “better” but also perhaps eliminate any tendency to develop hot spots in the head which might produce detonation. SO, about four years ago I had the opportunity to do this and voila, no more detonation, even while now using only plus gas, AND getting back to the original point of this story, the coolant temp is lower overall. When running up a hill on a hot day it still can get say up to the last white hash mark, but in general it stays cooler. Two issues resolved with not a trivial mod, but in my book it ranks as second best besides retrofitting the twin plate clutch. Almost forgot, since I’ve put off replacing my original hoses( believe it or not) I bought the 7psi cap from 928 motorsports and have been using it for a year now. It’s a bit of a bitch to remove, and initially I seem to recall coolant fluid evaporating more readily, though not unexpectedly, due to the lower pressure cap, but lately even in this hot weather I haven’t had to add any distilled water. In any case the car keeps running cooler even with the 7psi cap. Hope this was of interest...
Old 07-26-2010 | 04:27 PM
  #52  
dprantl's Avatar
dprantl
Thread Starter
Race Car
 
Joined: Dec 2003
Posts: 4,477
Likes: 4
From: Atlanta, GA
Default

Any update on this Andrew? I am curious. Today I was blasting down the highway again with both A/C's on full at ~80mph, digital dash showing 103 deg F for outside temp (heat index today is 104 - 108). Slow down to 55, then 8psi boost to 80 several times to try and make it hotter, yet the temp line was glued to the low side of the last white line, never higher. The most the ST2 ever read was 95 deg F. As soon as I got off the highway and got into stop-go traffic, ST2 temp dropped down to 92 deg F and the temp gauge went to a needle width below the last white line.

Dan
'91 928GT S/C 475hp/460lb.ft




All times are GMT -3. The time now is 09:48 PM.