Compression tested out to be around 70ish with the engine cold on both rotor.
Does this need a rebuild??

 

110 good
90 getting bad
80 bad
you probably need a rebuild soon if not now

 

if i warm up the engine and do another test, will it read fairly higher? or not neccesarily?

 

a warm engine will yield lower (worse) results. Your motor has very low compression.

 

if a motor is around 90 to 100. anyone know how long it will last.

saying you drive it carefully.

 

whats good in terms of 8.0, 9.0 etc?

 

Mine was tested at 90 psi on both front and rear housings 20k miles ago but it still runs and starts up with no probs at all. Vacuum is a bit low at 12-13 but I'm not worried.

 

hhhmm... so how long will it last with those kind of readings?

 

Also, the compression check method was done with a normal compression gauge and sumwhat modified and itll blow off preassure each time, so not sure how accurate can it be... it can only be higher if it is off right? or no?

 

If the engine starts fine when warmed up and idles fine then your engine is fine don't worry about it.

 

readings after warm up were around 80ish and slightly lower....will it at least last me 20k?

How much would u pay for this car?

BTW: all this info is given by the seller of the car im looking into

 

The owner did say the engine starts fine, idles fine, no hesitation, boost is fine (but at rare times it feels like the 2nd turbo doesnt kick in), never gave him any problems, never died on him, always starts.

 

Get the engine properly compression tested at a mazda dealership with a rotary compression tester. You're crazy if you buy the car without having done that. both 70 and 80 psi mean 'needs a rebuild.' anything under 6 bar (about 90 psi) is an old, tired motor.

 

If you in the SF bay area take it to RE and have Chuck to test it for you.. he has a rotory compression tester.

 

Did you hold the throttle wide-open while cranking? Leaving it closed will give false low numbers.

 

not sure, the owner said he stepped on it, not sure about wide open though