Compression Test #'s
#1
Not the company
Thread Starter
Compression Test #'s
Just had a compression test done, and was wondering what the numbers mean, and are they good.
Rotor 1 FT. 10.1 Rotor 2 FT. 10.4 Rotor 3 10.6
Rotor 1 RR. 11.0 Rotor 2 RR. 10.6 Rotor 3 10.6
Don't know anything about compression tests, but a potential buyer wanted to see one done.
Thanks for any help.
Rotor 1 FT. 10.1 Rotor 2 FT. 10.4 Rotor 3 10.6
Rotor 1 RR. 11.0 Rotor 2 RR. 10.6 Rotor 3 10.6
Don't know anything about compression tests, but a potential buyer wanted to see one done.
Thanks for any help.
#5
Original Gangster/Rotary!
iTrader: (213)
I would go back and ask this advisor about the readings. Those are off the scale. As dave alluded to, perhaps they are in psi and you just have to add a zero and lose the decimal point, but that seems kinda odd.
#6
Not the company
Thread Starter
Originally Posted by BlueRex
Cranking rpm? Mazda tester? What shop?
Guess i'm calling on Monday since he won't be there tomorrow
#7
F'n Newbie...
iTrader: (6)
Quick question for my own knowledge...
What is the average compression *supposed* to be for the 13B-REW engine??
Assuming that 1kgf/cm^2 = 14.223 psi than this engine would be pushing:
#1 FT: 143.65psi #2 FT: 147.91psi #3 FT: 150.76psi
#1 RR: 156.45psi #2 RR: 150.76psi #3 RR: 150.76psi
I know that a stock configured car shouldnt be pushing less than 100psi (preferably). I think I remember reading somewhere that from the factory they were supposed to be around 128(ish)psi.
If the rebuild was done with 3mm apex seals would that effect the compression??
I did a search of the forums and didnt find much in regards to this subject.
What is the average compression *supposed* to be for the 13B-REW engine??
Assuming that 1kgf/cm^2 = 14.223 psi than this engine would be pushing:
#1 FT: 143.65psi #2 FT: 147.91psi #3 FT: 150.76psi
#1 RR: 156.45psi #2 RR: 150.76psi #3 RR: 150.76psi
I know that a stock configured car shouldnt be pushing less than 100psi (preferably). I think I remember reading somewhere that from the factory they were supposed to be around 128(ish)psi.
If the rebuild was done with 3mm apex seals would that effect the compression??
I did a search of the forums and didnt find much in regards to this subject.
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#9
F'n Newbie...
iTrader: (6)
Slightly lower than what is listed, or slightly lower than stock compression?
Hrm... that eliminates one possibility...
Has anybody run compression tests on a FD with high carbon deposits?? I've heard that this could be a possible result/indication of carbon build-up.
(Everything I say is pure speculation resulting from research in this forum... only engine I have ever *personally* worked on is the H22A1 in my 'lude)
Originally Posted by rizzxx7
with a streetport and 3mm seals it should be slightly lower.
Hrm... that eliminates one possibility...
Has anybody run compression tests on a FD with high carbon deposits?? I've heard that this could be a possible result/indication of carbon build-up.
(Everything I say is pure speculation resulting from research in this forum... only engine I have ever *personally* worked on is the H22A1 in my 'lude)
#13
Original Gangster/Rotary!
iTrader: (213)
Originally Posted by rx7twinturboboy
Here's another question to throw at you guys, the engine has about 12k miles on it, so compression shouldn't be an issue.
#14
F'n Newbie...
iTrader: (6)
Originally Posted by dgeesaman
Check the FAQ.
Originally Posted by FAQ
28) What should the compression be?
Compression test results are reported as six numbers: 3 per rotor. (This is not the same as the compression ratio). Higher, more equal numbers are best. The original Mazda specs dictate 8.5+ kg/cm² as new (121+ psi), with 6.0 kg/cm² (85 psi, 690kpa) being minimum acceptable. Maximum difference should be 1.5 kg/cm² (21 psi, 150kPa) from the highest to lowest value. It is important this test is carried out using proper equipment and under the correct conditions for rpm and engine temperature. Mazda dealers are generally reliable for performing this test, so long as they follow the procedures precisely.
Compression test results are reported as six numbers: 3 per rotor. (This is not the same as the compression ratio). Higher, more equal numbers are best. The original Mazda specs dictate 8.5+ kg/cm² as new (121+ psi), with 6.0 kg/cm² (85 psi, 690kpa) being minimum acceptable. Maximum difference should be 1.5 kg/cm² (21 psi, 150kPa) from the highest to lowest value. It is important this test is carried out using proper equipment and under the correct conditions for rpm and engine temperature. Mazda dealers are generally reliable for performing this test, so long as they follow the procedures precisely.
Is this an uber strong engine, or is it likely a case of some mechanic taking a pipe break before doin a compression test???
Last edited by fendamonky; 10-14-06 at 11:27 AM.
#16
Original Gangster/Rotary!
iTrader: (213)
Originally Posted by fendamonky
Is this an uber strong engine, or is it likely a case of some mechanic taking a pipe break before doin a compression test???
#18
Not the company
Thread Starter
Okay, just spoke with my service advisor and the numbers are in kgf/cm^2 which means that yes...it's an "uber strong engine" as fendamonkey put it. There's nothing wrong with the numbers for a new engine.
#21
formerly chillin_rx7_guy
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When I first bought my MB car, the compression test came out to something in the 10's or 11's but the rear's were in the 6's cranking around the 250 RPM's.
They tested it out like 3 times.
You can ask Atkins Rotary since I took it to them.
FYI, they used a Mazda Rotary Digital Compression Tester.
They tested it out like 3 times.
You can ask Atkins Rotary since I took it to them.
FYI, they used a Mazda Rotary Digital Compression Tester.
#23
F'n Newbie...
iTrader: (6)
Yeah, I *was* the potential buyer that asked for compression tests (owner switched buyer last minute... It's a business deal, whatev... I have cash and time, another car will come along so I'm not worried or upset)
HOWEVER, I was quite curious as to how this anomoly would occur. I called RP Performance (of Manassas, VA) yesterday (they are the guys that did the rebuild) and explained the situation, along with the compression numbers.
Their baseline assessment was that compression in these numbers can occur (though very rarely) when there is a LARGE amount of carbon deposits in the engine. These numbers occur more often in the 2nd gen n/a engines when the drivers treat the car like they are granny driving to church all day, everyday... RP P went on to say that this can be bad (pretty sure I remember this right, I made the call after a 14 hour work day and didn't write anything down) in that it can screw up the springs on your Apex seals. Best way to check and see if the springs/seals are busted or not is to take the car out for a drive. It's a sports car, drive it like one.. "flogg" the engine for a good 20-30 min of spirited driving to break up and spit out the carbon (the second gen forum confirmed this tactic for cleaning out carbon build-up). After that turn the engine off and let it cool (after a cool down period while driving, back to the whole turbo timer vs. being responsible debate) down, but not completely cold. Re-start the engine and feel the idle. If it's rough and *obviously* not happy than you have fucked up apex seals/springs.. if not, lucky you.
Would any of the more experienced forum members like to comment on this? I would love to hear the general consensus on this subject.. if nothing more than as a clear reference point for the future in case somebody else runs into this problem..
Thanks,
Levi
HOWEVER, I was quite curious as to how this anomoly would occur. I called RP Performance (of Manassas, VA) yesterday (they are the guys that did the rebuild) and explained the situation, along with the compression numbers.
Their baseline assessment was that compression in these numbers can occur (though very rarely) when there is a LARGE amount of carbon deposits in the engine. These numbers occur more often in the 2nd gen n/a engines when the drivers treat the car like they are granny driving to church all day, everyday... RP P went on to say that this can be bad (pretty sure I remember this right, I made the call after a 14 hour work day and didn't write anything down) in that it can screw up the springs on your Apex seals. Best way to check and see if the springs/seals are busted or not is to take the car out for a drive. It's a sports car, drive it like one.. "flogg" the engine for a good 20-30 min of spirited driving to break up and spit out the carbon (the second gen forum confirmed this tactic for cleaning out carbon build-up). After that turn the engine off and let it cool (after a cool down period while driving, back to the whole turbo timer vs. being responsible debate) down, but not completely cold. Re-start the engine and feel the idle. If it's rough and *obviously* not happy than you have fucked up apex seals/springs.. if not, lucky you.
Would any of the more experienced forum members like to comment on this? I would love to hear the general consensus on this subject.. if nothing more than as a clear reference point for the future in case somebody else runs into this problem..
Thanks,
Levi
#24
Not the company
Thread Starter
Guess i'm lucky then, cause that's exactly what i did yesturday, and there's no problems at all with the car. Boost is normal, no rough idle or anything.
Edit: Should add that a potential buyer told me about the carbon build up thing, and suggested that i run the car hard like it should be and do the whole cool down thing and check the idle.
Edit: Should add that a potential buyer told me about the carbon build up thing, and suggested that i run the car hard like it should be and do the whole cool down thing and check the idle.
Last edited by RE-Amemiya; 10-19-06 at 07:46 AM.
#25
just dont care.
iTrader: (6)
it is not physically possible to make that many psi with a 9.0:1 rotary.
this means physics wont allow it.
i dont think you're lucky. i think you're unlucky -that you dont know how to do a compression test- or find someone who knows how to do one correctly.
and as for the carbon buildup, that would have to be a SHITLOAD of carbon. enough to **** something else up before the compression numbers got 25psi higher than brand new (~125psi).
this means physics wont allow it.
i dont think you're lucky. i think you're unlucky -that you dont know how to do a compression test- or find someone who knows how to do one correctly.
and as for the carbon buildup, that would have to be a SHITLOAD of carbon. enough to **** something else up before the compression numbers got 25psi higher than brand new (~125psi).