Finally was able to get my car in for a compression test, car has 155k kms on it now, engine was replaced at 109k. I just purchased it about a month ago, unfortunately my compression results do not seem good. They did say I am in very desperate need of new plugs and a tune up though, but I just couldn't justify paying how much the dealer wanted. I believe I do still have 5k of warranty left on the engine but the results are as follows:

Rotor # 1

710kpa, 680kpa, 680kp @ 250rpm
750kpa, 720kpa, 720kpa @ 288rpm

Rotor # 2
680kpa, 700kpa, 680kpa @ 250rpm
720kpa, 740kpa, 720kpa @ 285rpm

They said compression is at or above minimum spec and all they recommended was a tune up but I am definitely concerned with those numbers, should I take it back in right before I hit the 160k kms mark? Its a 2006 MT btw

Thanks,

 

tune up is very easy to do and a fraction of what a dealer would charge. ill let someone else chime in on your comp #s

 

Looking at this chart and you numbers I'd say your border line but I'm no pro at compression numbers with the rotary. Hope the chart helps.

 

285-288RPM on a s1 starter? I don't think that is even possible. Mine with the brand new S2 (09+) starter design cranks at about that.

 

Thats what it shows on my sheet, not sure if its been updated. I have only had the car for a month.

 

Also no hot start issues or anything like that, if anything it takes longer to start when cold then hot. When its hot its pretty much instant.

 

There was an update on the S1 starter to a 2KW version but even with that starter it would not hit that high. The 09+ starter is not a dealer installed part for the 03-08 RX-8.

Seems fishy to me, I have see agazillion S1 compression results and have never seem cranking RPM's that high on a S1 Renesis with either of the S1 starters. And how it would jump that much between the first and second test just doesn't make sense, the number usually drops, not increase.

 

I am assuming the 288 is actual and the 250 is what they normalize it to but just a guess

 

With the factory tester, it gets hooked up VIA USB to the WDS system or a laptop with the installed software and then the numbers are processed. These results make no sense. Dealers have been know to be lazy and just do the test, not hook it up, and just jot the numbers down. and they have been know to completely muck up the test as well. Did you get a print out of the results? If not then that explains it.

 

Just the numbers were printed on my invoice along with the techs ID, there was an original print out though I believe because when I got there they showed me the results on one piece of paper then said they are also on my invoice.

 

Hmmm, it still doesn't explain the jump in RPMS, I would have to see the results.

A jump in RPM tells me that they had it on a booster or something and so that basically falsifies the results. Often, as you do the test, the battery generally weakens and the RPM decreases. With a solid battery and starter, the cranking RPM typically stays the same thru a few tests but will always drop eventually and then you need to recharge the battery if you want to do more tests.

 

So far, I don't think i've ever seen a compression test reported on the forums that had a big RPM jump between the rotors that wasn't eventually confirmed to be a typo.

They may exist, but...

 

Rotor 1 is 3 rpm faster than rotor 2...288 VS 285

I'm having a difficult time figuring out what your issue is?

 

The first test was at 250RPM (exactly, which is possible but odd), the second at 285-288RPM. the 35RPP jump is odd and I have never seen an S1 crank that high both with my buddies (dealer tech) mazda tester/ laptop and my rotary diagnostics one.

 

Which is why it is likely a "normalized" result like the OP said ;-)

 

We have done at least 20, probably more cars here and I have never seen an S1 crank that high even with a new battery and starter. And the way my buddies Mazda tester and laptop did it, it did not normalize it to 250RPM. I have pics of the Mazda software, let me find it.

 

They have a software window on the tech site...you plug the #'s into it and it gives you normalized results. Used to be like that anyway

I do agree that the 288 is a bit high ...but there is no guarantee that the starter hasn't been replaced...or they didn't have a booster on it...and it could have been outputting 14V+ if that was the case

 

Starter rpm or not I think I should take it in for another one in a few k . Not happy with those numbers, instead of a tuneup I woulda preferred them to say they were going to replace it lol

 

My bet is on a booster but then that is cheating. On my buddies Mazda laptop setup (not sure how different it is from the WDS) it just gave you a read out in the software for each test and then you could print it. he said those reading were already normalized and that is what they give to Mazda.

So then maybe the first line is the normalized results and the second line is the actual with it on the booster.

 

Yes because if they do it off a booster at normal RPM range (230-260 depending on the condition of battery and starter) those numbers would be pretty different.

 

That makes the most sense....I've never had one hit 250 in a test, and never had both rotors read the exact same either...and for them both to be 250 doesn't make sense

 

I think they are trying to get out of giving you a reman.

 

Oh, and just for ***** and giggles, we put a 2009+ starter on my buddies RX-8 that had a blown engine (10psi on shitty tune) and it would start right away with the 2009 starter. It would not start at all with his newish 2KW S1 starter.

 

Pretty sure the 250 is normalized... the @288 results are 40kpa above the @250 result for all of them. It's the only thing that makes sense.

Based on the Mazda graph for these things: https://www.rx8club.com/attachment.p...6&d=1266716801

720kpa @288 is just below passing, as is 680 @ 250. I'd push for a new engine now.

 

This is very frustrating as its a very reputable Mazda dealer, I guess I will phone them up tomorrow and ask them.