Jonathan11

So I finnally had a compression check done on my car, turns out the loss of power is due to a cloged cat. Prior to the test im pretty sure my car was warm enough, and I say this because I spent almost all day at the dealership and when I finnally got my car back the water temp read 160F it was also cold yesterday about 68-70F. So I figured they let warm up suffice before running the comp test. I took my car to Ocean Mazda here in Doral, good service took long, but the service writer seem to know what he was talking about, and they didn't hassle me for my after market mods. But anyways here are my numbers if something looks wrong or out of place let me know guys please!

Rotor 1==#1) 7.9 #2) 7.5 #3) 8.3
Rotor 2==#1) 7.5 #2) 7.4 #3) 7.5

All readings are in KGF/cm2 @ 250rpms

Heres the conversion to "psi" if I made a mistake let me know please.


Rotor 1==#1) 112 #2) 107 #3) 118
Rotor 2==#1) 107 #3) 105 #3) 107

All readings are in Psi @ 250rpms


Another thing I want to know is how come they take three readings? The readings are all within spec of what Mazda requires ; but if anyone has some more info on what exactly these readings mean, so I can better understand why its done to check for a bad engine I would greatly appreciate that as well.


Thanks

alz0rz

iTrader: (41)

Average. Ideally you'd want all 8's but mid 7's is fine.

Old Rotor

Go to the bottom of this page and read "check my compression" I think this will answer your questions.

Jonathan11

So three test, one for each chamber got it. But dam im mid sevens, meaning im not making as much power as I could be. I sea foamed it last year around this time, maybe I'll do that again. Theres not much you can do to help out these numbers huh? This is a decreasing number unless you get a rebuild or new engine right?

CyberPitz

Some people have said premixing helps your compression numbers a bit.

I'm staying neutral in that discussion, just giving you some ideas

In the end, though, a rebuild is the only way to regain all of the compression you've lost.

kersh4w

iTrader: (3)

i've read that some rx7s had low compression, but even compression, across all faces, and had normal horsepower.

a dyno is really the only way to check if you have actually lost horsepower.

alz0rz

iTrader: (41)

Correct. The seals wear. All rotaries will naturally lose compression.

ganseg

iTrader: (5)

Do you mind if i ask how much they charged? I got two quotes from two of the three dealers close to me. $150 and $250.

All, I am torn between spending this money and only learning my compression or spending $75 and getting 3 dyno runs. I think if they dyno runs give a reasonable result, I can assume my compression is fine. I would also learn where my HP peak is so i can plan my shift points for the track. The straight at Brainerd is almost a mile long because it doubles as a drag strip. I want to get maximum speed for turn 1. In my E36 M3, i would reach 125 for an entry speed starting at about 65mph exit speed from turn 10.

On a different note, i would stop premixing before a compression check because my hope would be that they would say I need a new engine.

Jonathan11

150 is what I paid for a compression check and diagnostic, I had some other minor things that I told them about that they also fixed. Its worth the price bc/if you engine is bad and under 80k guess what you get a new one. Its also piece of mind to know your engine is in good shape, I'd say maybe there are places that are cheaper than others but hands down I would of taken it in for the check up rather than a dyno. Just my two cents worth.

And yeah I thought the same so I stopped premixing like 2 weeks before I took it in.

olddragger

iTrader: (3)

just do a vacuum test--if it is 16 or under go get a compression test. Read up about the barometric changes in vacuum--i dont know where to live
thats what i would do 1st.
OD

nycgps

iTrader: (1)

Just Curious.

Did you use the Mazda's tool to do the Vacuum test?

Cuz I have it since 4206f recall, but I never had the chance to use it (too lazy on my part, lol)

olddragger

iTrader: (3)

nope regular old autozone vaccum boost tester.
just use one of the lower nipples on the lim
read up on the proper way of doing this and how to interprete the meanings
its not hard , you just have to do it the correct way to get data that is useful.
OD

nycgps

iTrader: (1)

hmm ok

Well cuz i was thinking what the mazda tool actually do, i got it for lie 20 bux but i have no idea what the numbers mean ...

Jonathan11

What unit of measure does the gauge read NYC

Nemesis8

iTrader: (3)

I did it here