rx-7 obsessed

hey guys haven't been here in a while no play all work lately. happy new year as well lol first time i have been here in the new year anyways i have a 1987 t2 motor and the front rotor is stamped RE96 and the back rotor is FB59 does that mean my motor was rebuilt in 96? there is no paint or colored bolts and no marks of any kind. all i know is there are indications of the motor being rebuilt but i am not shure. the car did have 220K on it so i am assuming yes but just thought i would ask for imput

DavidHolmesIII

Unless that engine was a miracle, it probably has been rebuilt or replaced at some time. My engine replacement (new as of 03) was not painted and was otherwise just like the engine taken out. Different numbers of course. As of how to tell when or where it was rebuilt or replaced I have no idea from the numbers. I purchaced the car with the new engine, which was located and installed by a local Mazda dealership. Sorry I dont have any more info for ya, Good Luck

Atkins Dan

That is a Mazda Reman and was done in 96..

Mazda used to stamp there engines with a year of when it was rebuilt now that have a metle plate that that glue on and thay have been doing this about 99- and on...

Dan

rx-7 obsessed

thanks dan lol that made me feel alot better about all the work i am putting into my NA to t2 swap the car had 221 but the motor has 31k lol is 98-101 psi per rotor face for both rotors good for a turbo?

DavidHolmesIII

icemark told me 125psi is optimal for the NA. Turbo <>?

rx-7 obsessed

ya i know that but i thought the turbo would have lower compression because of the turbo lol

ericgrau

iTrader: (1)

Atmospheric pressure is 14.7psi absolute, or 0 psi gauge (gauge pressure is always relative to atmospheric pressure). When you compress the air, you decrease the volume by the compression ratio and you increase the pressure by this same ratio.

Assuming constant temperature*:
NA = 9.7:1 = 127 psi theoretical max (9.7 * 14.7 - 14.7 = 127)
turbo = 9.0:1 = 116 psi theoretical max (9.0 * 14.7 - 14.7 = 116)

So, assuming constant temperature, 125psi is "impossible"* on a turbo. 115 psi is probably optimal. Even on an NA 100 psi is still okay, though not optimal.

*In reality compressing the air greatly increases its temperature. If this is done rapidly and/or using a hot engine then not as much heat will escape. The added heat allows pressures of up to 9.7^1.4 * 14.7 - 14.7 = 339psi and 9.0^1.4 * 14.7 - 14.7 = 304 psi. But under these same conditions the temperature would reach over 800 F, so I'm betting that most of the heat does escape and it is better to assume a (relatively) constant temperature. During actually operation things move faster and the air does get pretty hot. What's worse is that the spark plugs must fire before compression is finished (or the fuel won't finish burning soon enough), igniting a small portion of the fuel and adding more heat. That's why ECUs and gasoline must be designed to avoid spontaneous detonation. ECUs run rich for extra cooling, octane rating measures resistance to detonation. That's also why arbitrarily leaning out you fuel or advancing your timing is stupid if you don't know what you're doing. Even if it doesn't detonate now, it might some time later. Then all of the sudden, <pop>, there goes your apex seals.

rx-7 obsessed

im leaving it stock lol but thanks for the imput i just thought the compression should be higher for only 31k on a Mazda rebuild

pfsantos

iTrader: (1)

Who let the engineers out again?

Check the FSM (see sig. below) - it has a chart based on starter RPM's and elevation, IIRC.

Atkins Dan

No problem & your welcome...

Thoes compression #'s are ok and you should be ok far after the tuneing is all done..

Dan

Fc3s_d1jp

Is this what ya'll are talking about? My gxl has 198,000 miles and runs perfect!

BC-FD3S

iTrader: (2)

yup, that would mean it was rebuilt in AUG of 99