Texak

I just tested my compression using a unit that TwistedRotors was kind enough to send me temporarily so I could test before I leave town. My actual unit will be shipped after he gets all the components assembled. I beat the hell out of the car for about an hour and then tested each rotor two or three times to find a repeatable pressure. I then waited about 3 hours and retested while it was still warm, and a final test the next morning after it fully cooled. My results are below:

Hot Test (oil/water temp ~180)
Front Rotor: 79 78 79 @320rpm/ 78 79 76 @323rpm
Rear Rotor: 83 83 82 @318rpm/ 83 83 83 @317rpm

Warm Test (oil/water temp ~110)
Front Rotor: 81 79 81 @307rpm/ 80 79 73 @271rpm/ 81 81 79 @307rpm
Rear Rotor: 85 86 71 @279rpm/ 86 85 84 @309rpm/ 86 86 87 @307rpm

Cold Test (ambient temp ~55)
Front Rotor: 76 76 75 @265rpm/ 76 76 76 @265rpm
Rear Rotor: 82 82 82 @266rpm/ 82 83 83 @267rpm

With the minimum allowable compression of 98.6psi, does this warrant a new engine?

TwistedRotors

Hey Texak,
I'm glad you got the prototype and that it worked out well for you. I like your thorough testing, it's a perfect example of what someone can do with this tool in their garage.
Unfortunately your numbers do look a bit low. Did you apply the correction factor? One point I'd like to raise is that when you're threading the tester in the sparkplug hole, make sure it's in good and tight. You should be able to get it tight enough just using your hands, but if the readings are abnormally low, it'd be something to check. I think we determined that the correction factor for the Mazda unit is 12.5%...if that's the case, then it looks like you may be eligible for a new engine.
-John

Texak

I have not applied any correction factors to the tests above. They are the raw figures from the tester. I have hand tightened them on for each test, but I think I'll wrench them down for this final test.

Texak

updated cold test this morning. The cold test was tightened with a wrench. It had a lower compression than either the hot or warm tests. I found that odd... i guess this really shows to not let mazda test your car on a warm engine, beat that car up a while and have them test immediately since they definitely won't do a cold test. either way, my results are all below the allowable compression. So does this mean i'm up for a new engine?

TwistedRotors

In my opinion based on the results you got, then yes, your engine is below the acceptable minimum. Even using the highest number you got (87psi) and increasing it by Mazda's 12.5% is still only 97psi. It must be noted that from looking at pictures, the Mazda tester has a larger internal "dead" volume than my tester. Therefore, it stands to reason that their readings would be even lower, prior to correction.
I'm curious...how is your car running? Does it start easily and still have good power?
-John

Edit: And all this is not even factoring in your crank speed, which is a bit high and should be raising the compression readings slightly.

Texak

The car is actually running very well. i just notice a lower power after i thrash it. also, cruising in 6th on the highway, there is a particular hill which i can no longer get up without dropping into 5th. this is a new development which began around january. i will send the tester back tomorrow and schedule an apointment w/ mazda. I'll post their compression results as well.

on that note, when i go into mazda, what should i say? Should i go ahead and tell them about my own testing and that i have low power, or play dumb? I have 62K btw and also a nitrous system which has never been used. it will be removed before i go in.

HeavyMetal699

Definitely below minimum spec.

If you play dumb they will probably just de-carb your engine and send you home. You can either pay to have them test it or tell them you had low power issues and tested it yourself.

Really depends on the dealership.

Texak

Well, they're not going to just trust my word that it has low compression, so they will test it anyway. Anyone else have experience with this?

And I decarbed it twice about 2 weeks ago. i thought that carbon buildup was the issue causing the power loss, but there was only a miniscule amount of white smoke briefly when i revved it. The engine was already clean before my compression tests.

teknics

here is your results (attached), used one of your warm tests and one cold.

you are definitely below spec, or i believe i read the tester needs a correction factor or something?

well either way that shows your current readings converted to 250rpm within .00001psi. so just apply the tester's correction (i think i read 12% or something) to those numbers.

kevin.

Texak

Thanks Kevin! Since you are a tech, will it help me to tell them i already tested the compression? I just don't want a song and dance since they have given me all kinds of trouble about tiny things like my rims and k&n intake. They actually made me sign a waiver to put on my aftermarket rims. they said that with the dsc, it could throw the car out of control and lock up the brakes. i get all kinds of bull like that.

Jedi54

iTrader: (7)

they'll always insist on doing their own compression since they cannot stand behidn someone else's equipement (no disrespect to Twisted) or someone else's process.

Let them do their own, they'll probably be worse then yours and you are most likely in store for a new engine.

TeamRX8

iTrader: (25)

The procedure calls for warming the engine first. A cold engine will always test lower.

The smoke from the decarb is from the decarb fluid, not the amount of carbon in your engine.

Texak

Team, you're right. They will warm the car up before testing. But from my test, it looks like it is best to heat the car up fairly well before having it tested. it has a marginally lower compression than just a warmed up engine (~3psi lower than warm)

I thought i read that the amount of smoke was contributed to the reaction between the carbon and the Zoom cleaner. that's why i said the engine must have been fairly clean prior to decarbonization.

For the guys that have been through this before, how long should I expect to wait for a new engine after they agree it's a goner?

.

shazy

I've heard that you should wait about 3 weeks to get your car back... that's what people said when they got their car back.

Anyway good luck and congrats on the second engine

nmarz77

Took about a week for them to "diagnose" and replace mine.

Nemesis8

iTrader: (3)

Is that the latest version of your software for OSX? Or is it the same as you posted here.

Hybrid G

Hey Texak

Did you get a compression test at mazda as yet with there official tester?

hybrid

elysium19

iTrader: (1)

When is this going to be available to buy?!?!?!?!?! I'm pretty sold as is. If you can do anything to calibrate it to have similar results as mazda's factory tester, then i'd be COMPLETELY sold.

Hybrid G

any news on the official test?

hybrid

teknics

thats the latest version, i update that topic whenever i recompile it with something new (after some testing of course)

version up in that topic is newest, working on a couple new features at the moment, graphing, memory of results etc.

kevin.

TheWulf

iTrader: (4)

Could anyone post the compression formula to adjust the compression to spec rpm? Also wondering if the same formula applies to older rotary engines or if they are different.

FazdaRX_8

iTrader: (1)

any news?

Texak

JUST IN FROM MAZDA...

Rotor 1:
94.105 psi Chamber 1
95.265 psi Chamber 2
93.38 psi Chamber 3
290 RPM
2.001 psi max rotor 1 - min rotor 1
4.263 psi max rotor 1 - rotor 2


Rotor 2:
99.615 psi Chamber 1
98.31 psi Chamber 2
99.035 psi Chamber 3
317 RPM
1.254 psi max rotor 2 - min rotor 2

shazy

So is that bad or good?

Texak

rotor 1 is under minimum spec of 98.6 on all three faces. Rotor 2 is borderline minimum spec. They haven't gotten back to me if this warrants a engine or not. they couldn't even find the minimum spec written anywhere!!!!