3rd Generation Specific (1993-2002) 1993-2002 Discussion including performance modifications and Technical Support Sections.
Sponsored by:

Compression Test results im confused

Thread Tools
 
Search this Thread
 
Old Jan 28, 2008 | 06:04 PM
  #26  
Tim Benton's Avatar
FD title holder since 94
Tenured Member: 25 Years
Liked
Loved
Community Favorite
iTrader: (1)
 
Joined: Mar 2001
Posts: 4,203
Likes: 37
From: Cedartown, Ga
Originally Posted by wb123
ok so what I am reading into after looking at all of this.

If the motor is brand new or freshly rebuilt it will result in 100psi on all rotors....

Now with that being said, and engine that is 16 years old and does score a compression test of 80psi all round is technically "good". THis is obviously do to obsolence wear and tear. So technically the this is a pretty darn good score for a car that still has all stock motor in it.

Now, The way i see it, unless you have a fresh motor your going to be in the range of 80-90 if the car has over 50k mils on it.

My car is not used for racing or crazy erratic driving.
I have had it for 4 years and its rarely seen over 6k rpms.
And the owner before me was an older gentlemen who traded it in for a Porche, and he also just drove it for pleasure sunday drives.

Now with that being said, I beleive my asking price of $22k is a fair starting point a I am not looking to just accept the first low ball offer i see.

THis car is really well taken care of, yes the car is 16 years old, and does show a small bit of obsolence on the exterior and engine, but it runs fine for someone who is looking for a nice partially stock rx7.
What everyone is saying and your not follwoing is your mechanic probably didn't use a mazda rotary compression tester for the test (or maybe didn't follow the procedures correctly). Also what they are saying is that your engine had even compression for hopefully all 6 rotors faces and pulls a nice vacuum at idle. So they are saying don't worry about it unless you want it done again with a mazda rotary compression tester for your's and the potental buyers peace of mind.

Tim
Reply
Old Jan 28, 2008 | 09:32 PM
  #27  
GoodfellaFD3S's Avatar
Original Gangster/Rotary!
Veteran: Army
Tenured Member: 25 Years
Liked
Loved
iTrader: (213)
 
Joined: Mar 2001
Posts: 30,804
Likes: 646
From: FL-->NJ/NYC again!
When I tested my FD with the throttle open vs closed, it made almost 1 bar difference.
Reply
Old Jan 29, 2008 | 10:17 AM
  #28  
alexdimen's Avatar
TANSTAFL
Tenured Member 15 Years
iTrader: (13)
 
Joined: Oct 2003
Posts: 3,770
Likes: 128
From: Richmond, Va.
Originally Posted by wb123
ok so what I am reading into after looking at all of this.

If the motor is brand new or freshly rebuilt it will result in 100psi on all rotors....

Now with that being said, and engine that is 16 years old and does score a compression test of 80psi all round is technically "good". THis is obviously do to obsolence wear and tear. So technically the this is a pretty darn good score for a car that still has all stock motor in it.

Now, The way i see it, unless you have a fresh motor your going to be in the range of 80-90 if the car has over 50k mils on it.
Not at all. Ideally, a fresh motor will make 132.3 psi. This is based on atmospheric pressure and the 9.0:1 compression ratio of the 13B-REW rotor.

My FC has 25k on the motor and still reads 120+ psi. all around.

Unless the gauge or information is wrong, 80 psi isn't a good score. Period.

FYI, when I obtained my FD it read 80 psi. I didn't even try to run it. I immediately started tearing it down for a rebuild.

As far as holding the throttle open, in my experience it makes a difference. ~10 psi or more on my gauge
Reply
Old Jan 29, 2008 | 01:32 PM
  #29  
beqa16v's Avatar
Senior Member
Tenured Member 05 Years
 
Joined: Sep 2006
Posts: 393
Likes: 0
From: Tbilisi
Originally Posted by alexdimen
Not at all. Ideally, a fresh motor will make 132.3 psi. This is based on atmospheric pressure and the 9.0:1 compression ratio of the 13B-REW rotor.

My FC has 25k on the motor and still reads 120+ psi. all around.

Unless the gauge or information is wrong, 80 psi isn't a good score. Period.

FYI, when I obtained my FD it read 80 psi. I didn't even try to run it. I immediately started tearing it down for a rebuild.

As far as holding the throttle open, in my experience it makes a difference. ~10 psi or more on my gauge
important thing is that how much should regular piston engine tester read?
Reply
Old Jan 29, 2008 | 06:46 PM
  #30  
danny hahn's Avatar
Senior Member
Tenured Member 15 Years
 
Joined: May 2001
Posts: 297
Likes: 0
From: laurel, md usa
I'm surprised this thread is still going. Even if you had good compression today, apex seals may break for a few reasons including age factors. do you have no miles on the car?

Originally Posted by wb123
I beleive my asking price of $22k is a fair starting point....and does show a small bit of obsolence on the exterior and engine, but it runs fine for someone who is looking for a nice partially stock rx7.
Are our cars that much now?
Reply
Old Jan 29, 2008 | 08:32 PM
  #31  
Thread Starter
Rotary Enthusiast
Tenured Member 10 Years
 
Joined: Jul 2003
Posts: 823
Likes: 0
From: Toronto
Originally Posted by danny hahn
I'm surprised this thread is still going. Even if you had good compression today, apex seals may break for a few reasons including age factors. do you have no miles on the car?



Are our cars that much now?
My mistake 8.0 all around was the final outcome.
The car has 77k miles on it,.
Reply
Old Jan 29, 2008 | 08:33 PM
  #32  
alexdimen's Avatar
TANSTAFL
Tenured Member 15 Years
iTrader: (13)
 
Joined: Oct 2003
Posts: 3,770
Likes: 128
From: Richmond, Va.
Originally Posted by beqa16v
important thing is that how much should regular piston engine tester read?
Why shouldn't it? Pressure is pressure. If the gauge is calibrated and the sealing surfaces are absolutely perfect, then you should see (compression ratio)X(14.7 psi).

Of course this is all theoretical. No ones surfaces are that perfect and most gauges are probably off a few psi.

When you leave the throttle closed the reading will be lower because the rotor will be compressing air that is at less than atmospheric pressure.
Reply
Old Jan 29, 2008 | 10:18 PM
  #33  
GoodfellaFD3S's Avatar
Original Gangster/Rotary!
Veteran: Army
Tenured Member: 25 Years
Liked
Loved
iTrader: (213)
 
Joined: Mar 2001
Posts: 30,804
Likes: 646
From: FL-->NJ/NYC again!
Lightbulb

Originally Posted by wb123
My mistake 8.0 all around was the final outcome.
The car has 77k miles on it,.
Well, then your FD has stellar compression.

/thread.
Reply
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
ZacMan
Build Threads
4
Sep 19, 2015 09:20 PM
BLK 93
3rd Generation Specific (1993-2002)
11
Sep 9, 2015 10:56 AM
SCinfidel
3rd Generation Specific (1993-2002)
4
Sep 8, 2015 05:36 PM
ZaqAtaq
New Member RX-7 Technical
2
Sep 5, 2015 08:57 PM
doritoloco
New Member RX-7 Technical
7
Sep 5, 2015 12:41 PM




All times are GMT -5. The time now is 09:29 PM.