I just want to know what most people get for compression.
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my FD has 150psi ... :bigthumg:
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most people don't even do these compression tests correctly.
Slapping a compression gauge on a spark plug hole and just cranking the starter does not equate a valid compression test. You need to be able to confirm what RPM (with some level of precision) the motor is cranking at before your compression readings can be conclusive beyond the level of 'ok it's not a blown seal'... many people tell me things like 'OMG you got 85PSI thats HORRIBLE?!' without even knowing what RPM the test was done at. 85PSI @ 200RPM is just fine and dandy. Just something I find annoying with people, on the other forum especially. |
Originally Posted by vosko' date='Jan 15 2003, 06:12 AM
my FD has 150psi ... :bigthumg:
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don't most engines rev the same speed with a fully charged battery. generally speaking ?
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Originally Posted by pengaru' date='Jan 15 2003, 01:22 AM
@what rpm?
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Originally Posted by vosko' date='Jan 15 2003, 06:22 AM
don't most engines rev the same speed with a fully charged battery. generally speaking ?
there are quite a few variables, some major ones are: state of the starter motor, old ones from 1980's cars will not crank like they did in 87. state of the electrical connections wether the other rotor had both spark plugs installed or was not producing compression at the time of the test (this effect RPM significantly) you can count the spikes on the compression gauge during the test over a 15 second period and just do the math to figure out the RPM... my friends 87 T2 gave ~90psi@200rpm... check out the shop manual, there is a compensation chart for this purpose, look up compression testing in it. |
Originally Posted by pengaru' date='Jan 15 2003, 01:28 AM
simply put, NO.
there are quite a few variables, some major ones are: state of the starter motor, old ones from 1980's cars will not crank like they did in 87. state of the electrical connections wether the other rotor had both spark plugs installed or was not producing compression at the time of the test (this effect RPM significantly) you can count the spikes on the compression gauge during the test over a 15 second period and just do the math to figure out the RPM... my friends 87 T2 gave ~90psi@200rpm... check out the shop manual, there is a compensation chart for this purpose, look up compression testing in it. |
I got about 85 1 mile above sea level at about 250 rpm. Is that good?
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According to my 1988 Rx-7 FSM,
Code:
Compression: Compression vs. Cranking Speed compensation chart (67U01X-023) http://sevatech.com/cars/rx-7/compre...-rpm-small.jpg Compression vs. Altitude compensation chart (67U01X-024) http://sevatech.com/cars/rx-7/compre...-alt-small.jpg See the links/URLs for the larger size charts /Seva |
The compression numbers given in the FSM are for when the official MAZDA tester is used.
I am not too sure about these numbers when you use a regular compression tester (witch schrader valve out) from autozone or the likes. hugues - |
it shouldnt matter what tester you use as long as you convert the units correctly
mike |
over 125 psi on both in my 91 n/a
T2 tested at just over 100 on both |
the t2 should be lower because its got a lower compression ratio
mike |
dont make a huge deal over compression numbers. They can sometimes vary. its not a piston engine. if it starts and runs. Its fine.
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you mean if it idles smoothly its fine
mike |
i have 13456433 gazzillion psi, or three whooshes
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Originally Posted by ChainSawOnSteroids' date='Jan 17 2003, 01:45 AM
i have 13456433 gazzillion psi, or three whooshes
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no ,,, that was at 27,430 rpm right before i was gonna shift mad quick yo!
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first time I did a compression check on my 7 (6 months ago) I took out the leading plugs, grounded the leading coils, left the trailing plugs hooked up (wait, this gets better) screwed the ol compression tester into the L2 hole, had a rubberband holding the release valve on the tester, angled it in such a way that I could see it from the drivers seat, turned the key and the car started... no ****. ran like crap and sat at about 200rpms, but F%$# me man, it took a minute of disbelief before I shut her down again. had to buy a new compression tester though, wasnt sure if it'd still be good after that.
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4 year old thread ftw
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as long as you remove both plugs F and R rotors and crank with valve removed on a full batt and good starter its purrrty accurate. ive yet to see over 110 though but then again they were on garage rebuilts with used housings so .........
party on garth |
failocaust
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