My compression test.
01-16-2010, 02:24 PM
#1
My compression test.
So a friend let me borrow the Mazda rotary compression tester and I was able to get a few readings today.
4.9,5.0,5.1 @ ~220 rpm on the front rotor
5.1,5.3,5.6 @ ~225 rpm on the rear rotor
Depressing eh? I know the spec RENESIS threshold is something in the high 6's? So according to my numbers, I have a terrible motor. But the thing is, it really does NOT feel like it. I know people will argue that compression loss is not noticeable, and unless you have catastrophic failure, you wouldn't be able to feel it but it just doesn't seem like my motor is in this drastic state. So I'm left with either taking the results for what they are, accurate, or I screwed up the test. I have slight reason to believe that the compression tester itself may be faulty because at times it would give me readings of 0.0,0.0,5.1.. etc.. random readings on either rotor and I would have to power cycle it to get it to work again. Maybe the pressure transducer? Not sure.. but at this point I'm hoping the test I did was just fubar.
With that said, there are certain occasions were the car will dip rpm on idle to ~700 but then it pulls itself back up. Slight stutters. If there is a real problem I am thinking the winter and cold weather is masking the problem.
So at this point my plan is to wait a little while longer and see how my car behaves and if I notice anything. I don't have a CAT on, so that's what's stopping me from going to Mazda right away.. but ultimately that is what I will be doing.
Anyway, what do you guys think? You folks that have experience with compression numbers and their implications, how would the motor "feel" if the compression numbers were really that bad? Input?
4.9,5.0,5.1 @ ~220 rpm on the front rotor
5.1,5.3,5.6 @ ~225 rpm on the rear rotor
Depressing eh? I know the spec RENESIS threshold is something in the high 6's? So according to my numbers, I have a terrible motor. But the thing is, it really does NOT feel like it. I know people will argue that compression loss is not noticeable, and unless you have catastrophic failure, you wouldn't be able to feel it but it just doesn't seem like my motor is in this drastic state. So I'm left with either taking the results for what they are, accurate, or I screwed up the test. I have slight reason to believe that the compression tester itself may be faulty because at times it would give me readings of 0.0,0.0,5.1.. etc.. random readings on either rotor and I would have to power cycle it to get it to work again. Maybe the pressure transducer? Not sure.. but at this point I'm hoping the test I did was just fubar.
With that said, there are certain occasions were the car will dip rpm on idle to ~700 but then it pulls itself back up. Slight stutters. If there is a real problem I am thinking the winter and cold weather is masking the problem.
So at this point my plan is to wait a little while longer and see how my car behaves and if I notice anything. I don't have a CAT on, so that's what's stopping me from going to Mazda right away.. but ultimately that is what I will be doing.
Anyway, what do you guys think? You folks that have experience with compression numbers and their implications, how would the motor "feel" if the compression numbers were really that bad? Input?
01-16-2010, 03:04 PM
#3
It's Complicated
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Try testing again those number are not good. From my knowledge anything under 7 is doomed.
Let some of the Rotary doctors give their input here. But I do think you should check it again with a different tester
Let some of the Rotary doctors give their input here. But I do think you should check it again with a different tester
01-16-2010, 06:57 PM
#7
You need a hand man ?
also your starter seems a bit slow. weak battery or old starter ?
"normally", the compression should be in the mid 7 @ 250 rpm. 2 rotors should be within 1.0 apart.
Seriously, when Kevin told me my engine failed I was shocked too, but hey, it is what it is.
also your starter seems a bit slow. weak battery or old starter ?
"normally", the compression should be in the mid 7 @ 250 rpm. 2 rotors should be within 1.0 apart.
Seriously, when Kevin told me my engine failed I was shocked too, but hey, it is what it is.
Last edited by nycgps; 01-16-2010 at 06:59 PM.
01-16-2010, 10:26 PM
#9
Nature vs. Nurture
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alz0rz, at what mileage did you start premix and heavier oil? What kinda driving do you do on a regular basis? I started at 34,000 (just got the car) and drive 75% freeway Purposely run up the revs every drive. Thanks..
01-17-2010, 02:18 AM
#15
FLAME ON!
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Dude about 10k miles ago my car was feeling kinda luggy. So I ran the gas down to e toped off with shell and premix jumped on the free way around 2am on a cold *** night with no one out and gave her a hard thrashing as they say.
Even with my race pipe I could see the black smoke coming out from behind my car as I hit red line from 1st - 3rd gear. It got to a point where I could not see it anymore and was doing about 90 to 120 mph with a z06. I went from one side of town about 45 min then back home another 45 min. She has been running strong sence. So every weekend I give her a nice hot flame on run on the express way and she likes it.
GL
Even with my race pipe I could see the black smoke coming out from behind my car as I hit red line from 1st - 3rd gear. It got to a point where I could not see it anymore and was doing about 90 to 120 mph with a z06. I went from one side of town about 45 min then back home another 45 min. She has been running strong sence. So every weekend I give her a nice hot flame on run on the express way and she likes it.
GL
01-17-2010, 02:18 PM
#16
hey alzorz nycgps - let us know how this goes? I'd appreciate your qualitative description of the car if in fact compression is low. I'm thinking of bringing my car in for a comp test, my MPGs are slowly getting worse (plugs+coils are fine), starting is difficult especially when warm. Power feels fine but thats why i'm curious if you can really notice poor compression.
I'm almost at 8 years old, so I need to check this out soon....
I'm almost at 8 years old, so I need to check this out soon....
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