Hey everyone! I just got my compression check done at my car at PFS.

What do you guys think? Bad? Decent? Good? i know the Rear rotor seams to have some fluctuations...

Does one rotor get more wear and tear than another?

Thanks!

Hmmmm i hope she still has good life in her for a while!

 

See my PM.

 

I couldnt read it clearly but does it say 7x psi on the rear rotor? If so, it is about rebuild time, you can either rebuild it now and know you have 2 good rotors to use, or wait until it pops and hope for the best. All depends on your future plans with the car and the miles that are on the engine. If it has 70k+ miles on it you wont want to reuse the housings any ways so just raise hell until it pops.

 

What was the cranking rpm?

Based on that, your motor is on it's last legs.

 

What did PFS telll you? It looks like one rotor is just about done. See post #3.

 

I freshed up the motor back in December before I sold the car to Josh. I used RA Classic apex seals, all new side and corner seals, side seal and corner springs.... Used housings with very minimal wear. Both faces had close to 100 PSI right after the rebuild. Pulled 17 inches of Mercury under vac.

What could have caused that much wear in that short of a timeframe considering PFS's compression test is accurate?

 

Like Goodfella says, you need to know the engine cranking rpm during the test in order to normalize the data to 250 rpm. The cranking speed can be calculated from the data you show, but the data file must be available in order to do that. However, even without knowing the normalized compression numbers, the differential between the rotor faces in the second graph looks out of spec. And that pattern is highly suggestive of a failing apex seal. It's not just the absolute compression numbers that are significant, but it's also the difference between the rotor faces and difference between the rotors that allow determination of engine health. So, as oo7 says, that rotor is "...just about done."

BTW, the tester used in this test was designed, built and sold to PFS by my company.

 

Hm, the RA seals raise a red flag for me.....

 

For comparison, the attached image is an example of what you would like to see. Notice the regularity of the compression peaks for all faces of both rotors. That evenness is more important than the absolute numbers, assuming the absolute numbers are at or above the engine mfg minimum compression specifications.

 

zkeller did an awesome job on the car and i got one heck of a deal. car is in perfect condition and couldnt say enough good thing about the whole deal..

As far as the compression is concerned, I asked PFS for the .WDQ... i assume this would be able to shed some more light.

only "mods" off the top of my head are -
1. Downpipe
2. PFS Exhaust
3. Greddy 3 Piece IC Pipes
4. Koyo Radiator
5. AST
6. Non-Sequential Twins
7. Ported Wastegate
8. New vac lines/oil lines
9. Nippodenso(sp?) Fuel Pump
10. Samco Coolant hoses

So im sure you guys can tell that only reliability mods where done and all (besides downpipe and catback) where installed at the time of rebuild. Dunno what this changes but more information is better than none!

Ill send Go48 the .WDQ file once i get this from PFS.

Thanks again all! I really hope that its "not on its last leg" - PFS said that it should run great for a long while... a little suspicious of that...

 

I've heard nothing but good things about PFS with Ray Wilson at the helm, so I wouldn't be worried about that.

What is the idle rpm, and what is the vacuum at that rpm? If that's really the compression, the car will not like to hot start, to say the least.

Maybe your cranking RPMs were very low......my Rotary compression tester I bought from Japan has a switch that you can flip and it automatically converts the readings to the 250rpm spec, pretty convenient

 

the number 200 is in the upper corner, no idea what it means.

compression does seem a little low, if its not going to see lots of boost and track time and such, its prolly ok for a while. any serious use, it should be rebuilt

 

I have always had good results in the past using RA seals. I assume that some of you had problems with them in the past?

 

I confess I have no firsthand experience with them, but I have read threads and posts in the past from users who had their rotor housings prematurely worn down by the seals. Not sure if there have been different iterations of RA seals, but I don't recommend them for customer motors.

 

Would the 200 at the corner mean the RPMs?

 

No, that is Max compression if i understand correctly. Just the Y axis measurement on the graph.

I should get more details on the test tomorrow from PFS. Ill keep you guys in the loop!

 

Thanks for the info Rich. That's the first I heard that.

 

Not to be a smartass, but what do you REALLY think the guys on the keyboards know more than Ray does about YOUR motor??? Really?? Come on dude, just close this thread.

 

Ernie. I respect your knowledge, but I do not respect some of your brashness.

I agree that some people will spout off only what they have read. But there are others that have experience and they relay it through this forum.

Congrats on your car, it is awesome. But I am still on the fence when it comes to the owner. You seem to be a bit on the arrogant side of things.

Oh, and in one of my grandfathers rotary powered experimental aircraft (pre LSA), the RA seals did wear the housings down much faster than the stock seals did. Just so you don't go accusing me of being just another nut behind a keyboard. However, premature housing wear and power loss over time is better than catastrophic failure when it comes to aircraft. If the engine seizes in a car... it is not nearly as bad of a situation as in an airplane.

 

And looking at the pulses.... I mean really???? does it look good to YOU??? I mean, c'mon... really???

Back to normal conversation:

Those pulses are uneven. That is a sign that something is wrong. There are 3 very different compression levels. Doesn't take a rocket scientist to determine that all three faces should be relatively balanced in compression.

 

The cranking rpm calculates to about 259rpm.

The main concern should be the pulses being even among each other. Having just one pulse lower then the others is normally a side seal issue, an apex seal will effect to adjoining pulses.

Nobody is going to be able to tell you what the life expectancy is going to be with this engine. It may run this way for the next 3 years, or the next 3 days. The only way to fix what you have is to actually disassemble the engine and repair it.

 

Since his question was answered now I guess he doesn't need the keyboard warriors, REALLY

 

I must say though, you sure are a good sport.

I take back the attitude in my previous posts.

 

i just received the .wdq file is and uploading it to another user who will analyze it. Either I or the other forum member will post findings. Thank you all! ill get back to you all asap! i know that uneven compression is not good, however the guy at PFS told me i should be fine as long as i do not push more power through the motor (which i don't plan on).

Ill post my findings asap. Thank you again!