The numbers are just a little low and the difference between 6.7 (95.3) and 7.0 (99.5) isn't very much so I wouldn't be too worried. The engine you said averaged 8.0 just after rebuild and so the compression has slightly dropped. Drive it for a couple thousand miles and see if the compression comes up. Also check to make sure your OMP is working correctly.

FYI: I have seen variances between compression testers which may or may not have been the case in your situation. Also, did the same person do the test both times?

 

nah, run about half a can of carb cleaner in each of the UIM ports on the passenger side of the engine bay with the engine RPMs running just high enough to keep from stalling out while performing the treatment, after done let the engine cool down for about 15 monutes then go run the **** out of it and recheck the compression to see if there was a difference. more often the answer is no but the only cost is a $3 can of carburetor cleaner and a little effort in knowing if it is something curable or not.

 

Just drive the car for a couple thousand miles and see if the numbers come up.

 

those were my beak in instructions for the first 2500 miles to keep the warranty...

 

That break is is *extremely* conservative. Whose warranty is it? Even with new bearings, 1500 miles is long enough for a break in period. As Rynberg so eloquently stated, a little boost won't hurt the motor one bit. These things aren't made of glass

 

There is no warranty! Streetport (considered race engine) voids any warranty by Mazdatrix. The only builder that I know of that has a warranty is Pineapple Racing. I have not heard back from Pettit Racing regarding porting and warranty.

Mr Rx7 tt - As stated in this thread, compression has gone down. If it's gone down after the first 5k miles, it is not going to go up by driving it another 5k miles.

Went back to RR&R for another compression test. This time Nick did the translating since they use the ancient paper based unit. He said it translated to about 7's and/or peak of 85PSI. Nothing acurate given as to each face. So $80 + $50, i'm pissing away money on compression tests since it won't be rebuilt under warranty. I was told by Nick it's acceptable to drive but he is unsure if he would tune to 15lbs but he is shure I would have a significant power loss and more then likely be under 350whp instead of over 400whp.

 

Your math isn't adding up. A 7 bar reading is equivalent to over 100 psi, which is a healthy motor. I'd call up Nick and ask him to clarify, there's a big difference between 85 psi and 100 psi.

Mr. RX-7 TT knows his stuff and has built many stout motors over the years, so don't dismiss his advice lightly. Use your PFC commander to make sure that your OMP voltage is within spec, you can check to make sure it isn't highlighted within the 'sensor/switch' area under the 'etc' menu. If it's highlighted, you've got problems---a faulty OMP will most certainly cause declining compression.

Also, Ihor and I warranty our ported engines for 1 year.

 

^ good to know, thank you!

I didn't intend to sound rude or bashing taking my frustration out on him. I just figured he only read the last page. I was told the same exact thing (drive it and it will get better) when the engine was rebuilt and I got all 8's and I was expecting all 9's.

I have no idea how to interpuit the readings and neither did Mazdatrix which is why they asked me to have Nick do it. The printout looks like a stocker ticker from the 60's and prints like a heart monitor or lie detector. The first time, the paper showed 4-5's but I was told it was 6-7's. So I figured they would just retest for free, actually. Otherwise I would have paid Mazdatrix since that's who needed to know and they have the new compression tester. The 2nd test is between 5's and 6's. On the side of the paper it shows PSI I beleive. Nick told me I was peaking at 85PSI. I can scan the printout but the ink is so light it may not scan well. I'll try tonight though. I should have just bought a tester at harbor frieght and done it myself. I also have an appointment with XS Engineering next month and i'm shure they will test before doing a tune.

I have a brand new harness with this engine and I do check the etc menu. There is nothing highlighted and last time I checked voltage for mop was fine. I also premix with red line.

 

You can't buy a rotary specific compression test at harbor freight, it's an expensive proprietary mazda specialty tool.

Mazdatrix doesnt know how to interpret compression readings

85 psi is not good, that's less than 6 bar, like 5.8 or 5.9.

P.S. You're welcome

 

a regular gauge type can work if u wan to just get a close look if your motors blown or not lol. just yank the valve out or if it has a peak hold button make sure it's pushed down so bounces for each rotor face...

 

Right, but that's not the case here........

 

yea i know

 

I know you can't buy a $750 Mazda tester at harbor frieght but you can get a piston tester and remove the valve as stated. I'm sure I could have bought one for less then the $130 for the two tests.

There's no ink on the paper only impressions which won't show when I scan it. It shows between 6 and 7kg/cm2 on the front rotor and at or slightly above 6kg/cm2 on the rear which doesn't make any sense since the first test showed lower front compression. On the side of the paper the same line that has 6kg also shows 85.3lb/in2.

 

Hey guys, make sure you're units make sense. There's a slight difference in the values.

1 bar = 14.7 psi = 1 atm (atmosphere @ sea level)
1 kgf/cm^2 = 14.2 psi (so 100 psi ~ 7 kgf/cm^2, 85 psi ~ 6 kgf/cm^2... consistent with shop manual's conversion)

 

Allow me to correct your correction

1 bar = 14.503 pound/square inch
and
1 atmosphere [standard] = 14.695 pound/square inch

so bar and atm aren't equal

 

Damn, you got me