My car goes for a compression test wednesday: 78,000 miles, one year left on the Rotary Core Warranty. If it were your car, what would you consider an acceptable compression result to justify keeping the car?

Obviously if it fails the test, I'll get a new engine under warranty and keep it. And if it passes easily (116+ for a typical new engine if I'm reading the posts correctly), I'll keep it.

But if it's 100, 101, 102... my fear would be that I won't be able to get it replaced before the warranty ends, yet it's likely to drop into the unacceptable range soon after.

I know it can't last forever, but if you were hoping to get another 30-45,000 miles from it before it fell below 100, what number would you want to see?

 

Guess you'll just have to make sure it fails the compression test before the warranty expires.

 

I never had an engine compression test done, but i did my research and found out that according to the workshop manual, there should not be more than a 14.5PSI difference between the two rotors. Hope this helps.

 

Maybe this is what you are looking for?

 

Anything over 98 is within Mazda specs and would pass a compression test. 100,101,102 is fine and means the engine is good has good compression. Good luck. I'm sure it will pass if it is running ok now.

 

My worry is if all engines lose compression over time, the question becomes what value would I want to see for a 78,000 mile engine if I wanted it to run well for another 45,000 miles before wearing down into the questionable range?

What's a normal value for a 78,000 mile engine? I assume higher mileage engines will normally have lower compression than new ones?

Mine runs OK, except for it stumbling a bit on hot engine starts (cold starts are fine), and a slight loss of power feeling when accelerating hard with a hot engine (not always though). Classic compression problem symptoms apparently, but could be a million other things too. We'll see tomorrow

 

^ please post your results and let us know how this turns out, I too have been pondering a compression test for an engine that seems to run "OK" but not great. I am interested in how this all works out for you.

 

How would you go about "making" the engine fail a compression test?

 

Just got my compression test done. I tested 120 all across. I was shocked an 04 with 67000 miles. Kinda dissappointed not gonna lie. I wanted a new engine before my warranty was up and I also had to pay for the test. But I was impressed

 

So I got a compression test done at a ex-Mazda dealer and this is what they gave me for results
rotor 1- 05.4
rotor 2- 05.6
rotor 3- 05.6
@182 RPM
now first i should of gotten 3 more readings but does this qualify for low compression?

 

Judging by the chart above it should be just over the minimum line.

 

There are several methods.

 

Your RPM's indicate you have the original slower starter. I would get the updated one ASAP.


To the original poster ask to go in the back and watch the test if they will not do that give them a pad / clip board to write down the readings. You will get three numbers per rotor and the @RPM speed the starter is spinning. If you do not request that you will only be told PASS/FAIL.
A box of doughnuts might help also. You also might get the results in kPa, not PSI, that is ok just post them in this thread.

 

You WISH you can get near brand new compression numbers.

but I seriously doubt that.

You can hope it fails, mine did, probably got raped by early ultra low idle OMP rate.

 

If you pass the compression test at 78k. I don't think you have too much to worry about for the next 78k. If you have not changed the plugs and wires in the last 40k that could cause some acceleration stumbles. Ignition coils too.

 

From what I'm reading, that's BETTER than a typical new engine

Congrats!

 

Thanks. I was really shocked.

 

Good news. Are you the original owner? Change oil frequently? I assume you closely maintain her? Oh, one more question. Do you premix?

 

It failed at 79,000 miles. New engine next week.

Roughly 8.0 for R2 (yay!?), but only 6.6 for R1 (boo)... at 270rpm.

So I'm in the New Engine Club. Not sure whether to cry or cheer. Both I guess. I love my 8, and that little rotary is it's soul. But financially of course I guess that's a relief.

No charge to me.

So tell me, what do I get? If a "remanufactured engine," what does that actually mean? It's not the same as a new "crate engine?"

And I assume it'll be a Series I from what I read? So subject to the same early failure vulnerabilities?

And no, I didn't "premix" or do any of the things many of you do special. Just drive normally, no modifications, regular oil changes at the dealer.

 

A reman engine is basically they take all the failed engines take them apart and use the parts that are still usable. So a reman engine will be a mix of old and used parts. And yes it will still be a series 1 motor so you still have to be careful. And it is possible it will be a new engine if they are out of remans. But not very likely. Also make sure you change your oil after like 200 miles when you get your car back.

 

If this is directed towards me then I answered most of these questions in my other thread. I will post answers to the rest too. I don't want to hijack this thread

 

There are a couple things that you might want to get done while the engine is out, these will cost you some money.

Do you have a 6-speed? Change the clutch, easy to do with the engine out.
You have an 2004 right? Check the engine mounts.
Have NEW belts and hoses installed.
Get new spark plugs if the dealer does not supply them.
It is advised to get new connectors for the fuel line.
I would check / replace the OMP lines.
Check the oil cooler lines, much easier to change with the engine out.

 

Thank you!

Doing engine mounts, coils/plugs/wires, battery.

I'll mention then the belts and other things. Great idea

 

what would a new or almost new engines compression numbers be?

 

116+ for a typical new engine, if i'm not mistaken.