So if Im getting compressions of 70 front and 65 for the Rear is it time for a rebuild and a port job ?

Im getting 340rwhp, no cold or hot start issues, she runs a bit rich and does go through spark plugs pritty quick.

But I hear everyone say how 110+ is good compresion so how gone am I ? OR just run her till she dies (been running 14 psi for last 5 yrs now)

Thanks

 

Who did the testing? Was it done warm/cold, at WOT?

 

not really sure, my mechanic did it, but I was under the impression is was done warm.

they where really surprised with the numbers I got and didnt expect me to get them... but they did, so Im happy..

Im just wondering what my next step is.... go the next step or be happy :P

 

Those numbers are definitely low if they are accurate...anything below 90 is pretty bad I would say. I might think about a second compression test though. Those numbers seem suspect to me because usually you will at least have some hot start issues with compression that low. But if you're not having any problems with the engine and power isn't down, I don't see any reason to rebuild right away.

 

70/65 is about 15-20psi below the minimum spec in the FSM. 65 is almost so low it leads me to believe there's a cracked seal.

 

well if I had a cracked seal she wouldn’t be running right ?

what other things should low compression cause me to have ? loss of power ? etc etc ?

but yeh I guess I have convinced myself to just keep her going as is..... I really just want a excuse in my head to pull her apart and get more power but cant really justify it.

 

It depends, if it's just a chipped apex or collapsed side seals, it'll still run fine and seem pretty normal.

 

Unless he cracked two apex seals per rotor he wouldn't be getting even pulses.

 

What I've commonly seen for 'equal' pulses, is collapsed side seals that get collapsed in the center, usually from detonation/high RPM shifting as far as I can tell, but I've seen all 3 apex seals chipped too, so *shrug* it's hard to say.

 

eek, them numbers are pretty low, and if the engine is good now, the best bet is to take it apart now and rebuild and more parts will be reusable.. before it eats a apex and u have to buy more expensive parts for it such as rotors and housings

 

well if she does blow (hmm out of context that sounds suss..) but if she does blow I'll go all out and port and upgrade her..

thx for the input

 

a word of caution alot of time when the motors blow the apex seals shatter and fly threw the turbo!, which can really mess up the viens on the exhaust side of the wheel.

get it retested using a mazda tester to be sure, how many miles are on the engine??. its alot cheaper to rebuild before it blows than to have it blow and need to replace rotor and housing and a turbo...

 

A collapsed side seal will still only affect one rotor face. I'm not discounting the fact that he may have damaged multiple seals however when you've got even yet low compression you're usually going to find that the sealing surface (housing or irons) is worn or damaged. Either way, get it checked out again to be sure then if you're still low start building a new engine

 

Hey, does anyone know what is acceptable for compression in metric units? I saw a reading from a freinds mechanic, tested on a mazda rotary compression checker, and it was read in kg/cc^2, I think. Enlighten me if you guys know please.

 

This is for an S4 car BTW.

 

those numbers are definitly low.. I would take it to a rotary machanic and have it done with a rotary compression tester and a fully charged battery.

If your car is running and smooth as your say.. I find it have to believe that you have such low numbers on the rotors. And Since you only have 1 # for a three faces.. that leads me to believe it was done with a pistion tester..

So get it checked right before you do anything drastic.

 

If you wait until it blows you'll be replacing a rotor and rotorhousing due to apex seal damage. That thing is ready to let go anytime now...but hey, if money is no object, go ahead and destroy it and pay the extra costs later.

For some reason people think that any core is automatically going to be 100% rebuildable, and that simply paying the cost of the rebuild and seal kit is going to make it new again. They generally are wrong.