wb123

I got a compression test last summer by my mechanic, who is very in tune with the rotary engine and has alot of history with working with them.

He said my engine was in good shape, with an 80PSI all around test score.


Now i come on here and post 80Psi and i here the my engine is more or less on its way out...

The car pulls hard and does not give any indication that it needs a rebuild.

danny hahn

Perceived bad compression is the least of your worries especially when the numbers are the same.

wb123

Well..?
are you saying i have nothing to worry about ?

spandy

iTrader: (1)

At this very moment, I wouldn't worry about anything, but I'd be sure to get prepared just in case because even though those are not completely terrible numbers....they aren't good either.

GoodfellaFD3S

iTrader: (213)

If you're worried, have it tested again with a mazda rotary compression tester.

80 psi is very low, but perhaps the numbers aren't correct.

When the car is warmed up and idling, what is the vacuum on your boost gauge, what is your idle rpm, and do you have stock ports or not?

wb123

The engine idle is 750,
boost guage is sits around -16 to -18psi
the engine internally is complete stock..

dontlift

It's pulling good vacuum. btw that's inches of mercury, not PSI...

alexdimen

iTrader: (13)

From my experience, anything below 90 psi also pulls low vacuum and has starting/flooding issues.

BTW, are you sure it's psi or is it mm/Hg?

(-18) pounds per square inch = -36.6525786 inches of mercury

stock is 17 in/hg...

wb123

yea is is in/hg my mistake.

wb123

So if my car idles fine at 750rpm. and its holding good idle at vacuum i guess they didnt do an accurate test im assuming.

dontlift

I think the only way to know for sure is to get it comp tested again. But with no symptoms, it may not be necessary except for peace of mind. Was there a reason why you had it tested in the first place?

wb123

To sell the car.
I did tell the person who was doing the compression test I was looking to sell my car.

They basically said 80psi all around and told the buy to call them if they had any questions....


He knows his **** well but isnt really that helpfull and doest like to be asked alot of questions.

wb123

I beleive the test was done with just a normal compression tester

i got this quote from a web site
. "A simple tester can be made by using a standard automotive compression gauge. Remove the one way check valve, and install the tester into the leading (lower) spark plug hole in the front rotor. Make sure your battery is fully charged, remove the EGI fuse, then floor the pedal and crank the engine while an observer looks at the gauge. You are not looking for excellent numbers, just three even bounces above 70 PSI. If the rotor has lost one apex seal, you will get one strong bounce followed by two very low bounces. If all seals are damaged, then you will get three bounces that barely register on the gauge. Repeat for the other rotor. "
http://www.aaroncake.net/rx-7/blown.htm

Seems to me like 80psi is very good from reading this.

GoodfellaFD3S

iTrader: (213)

The motor's fine.

He doesnt know his ****, at least not when it comes to testing compression. I'm sure yours is higher than 80 psi based on your vacuum. If it'll help you sell the car quicker, might not be a bad idea to have the motor tested with a mazda rotary compression tester. I have one, but i'm not too close to toronto

Mahjik

iTrader: (1)

Yes, that test is not "exact". It just used to get an "idea" of the compression. Typically for a sale, you'll want an "exact" compression test done.

wb123

Well they have driven the car and stuff and also this compression test.
They say the engine is in good shape.

What is this supposed to mean? =)
THey are reputable, and have been around for 20 years.

dontlift

He's saying the test method in the web site that you quoted is only a very crude test. The page is titled "is my engine blown" -- I'm guessing it was probably intended for an engine that won't start...

wb123

Ok so im looking to sell my car.
I go to my "shop" they do me the test.

I come on here and then i start hearing "man that things going to need an overhaul soon"

I dont beleive that my mechanic would tell me my engine was fine when its not...

They have driven the car and said engine pulls hard still, and is good shape.

What other test is there ?

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.

Smitter

go get a real compression test done. that will be your determining factor for any buyer of the car.

beqa16v

mine showed about 90psi on regular automotive gauge. i guess i should be happy with results. pulsations were perfectly even

Prometheus

iTrader: (2)

I have heard that doing a compression test with the throttle to the floor (opening the throttle body) gives you a more accurate reading...

has anybody else heard of this?

Mahjik

iTrader: (1)

That should be a normal part of the process:

http://www.rotaryresurrection.com/3r...ion_check.html

Smitter

i have tried both with throttle open and closed.
the last time i tested my car with a mazda tester it made an average of +.2 bar difference with the throttle open.

Six Rotors

iTrader: (17)

hey,look if you are really worried about it,contact me when I get back from Florida and I will do a proper compression test with a Mazda tester,no charge-just beer.
I will be back from Florida about March 6th.
By the way who tested it?