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JDM FC3S S5 TURBO.
ATTACHED IS THE RESULTS FROM THE COMPRESSION TEST. TESTS WERE TAKEN BOTH HOT AND COLD WITH SIMILAR RESULTS.
IS THIS ACCEPTABLE? DO I NEED A REBUILD?
Well the compression specs in the '89 (S5) FSM says the minimum acceptable compression is 589 KPa or 85 PSI or 6.0 Kg/cm^2, @ 250 RPM, so in that regard it looks like your front rotor has one low chamber - possibly just a carbon stuck side seal. The FSM also has a differential compression spec (i.e., difference between chambers) of 147 KPa or 1.5 Kg/cm^2 or 21 PSI between the lowest & highest face on the same rotor. Both of your rotors look good there.
But before you crack open the keg to rebuild, I would re-do the compression test, double-checking a few things when you do it....
1. I see that you're reporting the comp #'s measured at 207 RPM, not the comp #'s that RCT tester pictured should have calculated for you that are normalized to 250RPM per the FSM spec. Those comp #'s should be a little higher for both rotors than the comp #'s reported at the actual 207 RPM cranking speed. Did you record those #'s? If so, post them up, otherwise definitely do the test over again.
2. Just to verify, did you have the throttle wide open while cranking to test both rotors? If not, it will result in much lower comp #'s.
3. You say you tested with engine hot & cold, which is good - the only comp #'s that matter though are the hot ones.
Since the rear rotor looks healthy, and front doesn't appear too far off, I'd try a de-carbonizing treatment before you retest. When the gas tank is close to empty, like <1/8 tank, dump a can of Seafoam in there and drive the snot out of it - get the car up to operating temp, then do a bunch of high RPM pulls until the tank is on fumes. You can also try the distilled water de-carbonizing treatment - this basically steam cleans your combustion chambers/rotors & seals. It involves running the car at a high idle (>3K RPM), while you draw the distilled water into the combustion chambers via one of the vacuum ports that lead to both primary intake ports. While you're doing this, the car will want to stall; regulate the water flow by pinching the hose and apply more throttle to keep it from stalling - do it until it sucks up about a gallon of distilled water and turns it to steam out the exhaust.
Well the compression specs in the '89 (S5) FSM says the minimum acceptable compression is 589 KPa or 85 PSI or 6.0 Kg/cm^2, @ 250 RPM, so in that regard it looks like your front rotor has one low chamber - possibly just a carbon stuck side seal. The FSM also has a differential compression spec (i.e., difference between chambers) of 147 KPa or 1.5 Kg/cm^2 or 21 PSI between the lowest & highest face on the same rotor. Both of your rotors look good there.
But before you crack open the keg to rebuild, I would re-do the compression test, double-checking a few things when you do it....
1. I see that you're reporting the comp #'s measured at 207 RPM, not the comp #'s that RCT tester pictured should have calculated for you that are normalized to 250RPM per the FSM spec. Those comp #'s should be a little higher for both rotors than the comp #'s reported at the actual 207 RPM cranking speed. Did you record those #'s? If so, post them up, otherwise definitely do the test over again.
2. Just to verify, did you have the throttle wide open while cranking to test both rotors? If not, it will result in much lower comp #'s.
3. You say you tested with engine hot & cold, which is good - the only comp #'s that matter though are the hot ones.
Since the rear rotor looks healthy, and front doesn't appear too far off, I'd try a de-carbonizing treatment before you retest. When the gas tank is close to empty, like <1/8 tank, dump a can of Seafoam in there and drive the snot out of it - get the car up to operating temp, then do a bunch of high RPM pulls until the tank is on fumes. You can also try the distilled water de-carbonizing treatment - this basically steam cleans your combustion chambers/rotors & seals. It involves running the car at a high idle (>3K RPM), while you draw the distilled water into the combustion chambers via one of the vacuum ports that lead to both primary intake ports. While you're doing this, the car will want to stall; regulate the water flow by pinching the hose and apply more throttle to keep it from stalling - do it until it sucks up about a gallon of distilled water and turns it to steam out the exhaust.
08-16-19, 05:05 PM
