So when I started the car after work a few days ago, the check engine light started flashing and the car had a really rough idle. Car felt like it had no power and the only way to get it to move was to rev it to ~5000 rpm and feather the clutch in.

I had the car towed to a local rotary mechanic(Juni @ JRX Rotary), and when he first started the car, he could immediately hear a problem with the engine. It sounded like a "clunk clunk clunk". He did a compression test and here are the results (roughly):


Rotor 1:

Chamber 1: 117 psi
Chamber 2: 110 psi
Chamber 3: 112 psi

Rotor 2:

Chamber 1: 102 psi
Chamber 2: 100 psi
Chamber 3: 0

So basically from my understanding, rotor 2 has no compression in the 3rd chamber and thus the engine... well, basically is only half an engine now... My mechanic tells me this is because of a blown apex seal, and the engine will have to be rebuilt.

I tow it to Mazda the following day in hopes of having warranty work done on the car(she's got 65k on the odometer), and the tech there turns the car on(after about 4-5 seconds worth of cranking) and says ".... that sounds bad...". He says he'll have the tests done on it and will get back to me the following day.

Fast forward to today, and he tells me that the engine is ok. He says the spark plugs, coils, and wires are the problem and will cost ~$900 to fix. When I ask to see the compression test he claims the tech that was doing it left the results in his toolbox and that I can return tomorrow to look at them...Wtf.

Couple of questions:
1. From the results of the compression test do I need a new engine?

2. Is that tech full of ****?

Any advice on what to do would be greatly appreciated

 

well the rotor has 3 apex seals. each seal separates one chamber from another one. so if the apex seal fails you lose compression in 2 chambers.

what was the code for the CEL? and why would plugs coils and wires cost 900? plugs and wires together shouldn't cost 200 total. coils are about 31.00 a piece last i checked. so thats what 320 tops? he's going to charge you 600 labor to change plugs wires and coils?

 

zoom44 is right. You should see 0 on two chambers. I dont think I have ever seen a whole burn right through a rotor before. I have helped take apart and put back a lot of second gen RX7s. I cant think of anything that would cause a 0 on just one chamber.

 

well a side seal could

 

btb i edited my first post re read it if you read it earlier than now

 

I would wait for the compression test from the dealer...

There needs to be cranking RPM #'s to make them valid too

0 on one face is kinda difficult too

 

It would usually not be zero though would it...unless it fell out completely??

 

well he does have lower numbers on chambers 1 and 2 on the second rotor so an out of place side seal could be an idea. So yeah lets see what the dealer says in their compression checks. If they come back bad from the dealer I would think they would have to fix under warranty.

 

We perform compression tests on each motor after each event as well as a dyno pull to confirm what we left the track with. The higher frequency fault mode for our race motors running in Koni is side seal related. It is my understanding the other teams have experienced this rascal as the higher frequency failure mode also.

Compression tests on a motor gone sour (I did one today) reveal one low(er) pulse (or more) and during teardown we can typically trace it to a specific rotor and a specific side seal. We have experienced zero apex seal failures---all side seal related and/or non-apex seal. I have learned the side seal issue is way more prevolent in the Koni Challenge race motors than steet motors or boosted motors (unless someone can provide more info please). My CSI rotary gut tells me our road racing motor failure mode is higher rpm related. I digress.

Brother, I've experienced 9 engine failures in 2008. Nine. None of them has compression tested at zero. Repeat test. Repeat again.

A zero compression with my non-mechanical thought process (but tons of experience) would be catastrophic---like the engine won't run at all.

Can you be certain that the compression results are correct? Start with good data. Back it up twice. Assess.

Happy rotoring,

Eric

 

I didn't get a chance to see what CEL code was given because I was too busy sulking in misery

As for the compression test I had done at the independent mechanic, I can't really say if it was done correctly or not. I'll try to recollect what happened:

Towed the car in, mechanic pumps brake pedal a bunch of times. I stand there observing. He turns the car on, determines it sounds like **** and turns it off. He pops the hood and inspects a couple of spark plugs. He looks at 2 spark plugs(dipstick side) and says they look like crap, but he's gonna do a compression test anyways. He messes with the fuses and battery then hooks up a little box with 3 screens on it to random places around the engine. He turns the ignition and tells me to yell "stop!" when the number on screen counts down and reaches 1. When I yelled "Stop!", 3 numbers appeared on screen, which are the numbers i posted above.

That about sums it up. Any thoughts?


The dealer said $96 bucks for the testing fees(non-refundable since the work required is not under warranty) + $80 for wires + $200 for coils + $140 for plugs + labor + tax

But thanks for the good advice guys, I''l update you on what the dealer says.

Oh and this was Clippinger Mazda in West Covina, Socal if anyone is curious

Anybody in Socal wanna teach a bum student how to change plugs, coils and wires? I got around $380 in my checking account, so whatever doesnt get spent on parts can go into your pocket

 

Eric, makes a good point. Have the test run a couple more times to verify the issue. I have to agree with Eric about the side seal issue, we have seen our fair share of engine failures this year also. Side seals and coolant seals seemed to be our culprits most of the time.

Eric, I remember almost all the teams lost a motor at Lime Rock this year. Didn't Riley, Maxwell Paper, and BMR lose motors that weekend? Ya'll lost two that weekend if I remember...and hell we lost a car. Rough race that was!?

 

Plugs are $80ish, coils are $110, and wires are 80ish....

Should be a lot cheaper than the dealer prices

 

yeah, that 0 just screams an error in the test.

 

Dan you know the dealer rapes everyone. Got a quote from my dealer, same as what he got. Most dealers have 25-50% mark up. Ofcourse I decided against that and bought everything myself, including my LS2 coils for just under $250.

 

No 0 is definitely bad testing i agree. as Eric and Al say it screams "do it again"

pumped the pedal before turning it over? WTF?

 

Even if an engine has destroyed side seals (from a spun bearing that lets the rotor grind into the iron walls) it will generate more than 0psi.

The normal mode of failure for older rotaries is to have 100 or whatever on the front, and 0 on all 3 faces of the rear.

The normal mode of failure for renesis is to simply have declining numbers across the board.

All rotaries tend to have slightly more wear, and slightly less compression, on the rear chamber as time goes on.

I would say that it would be near impossible to accurately obtain a zero psi reading on a single face.

 

Don't you qualify for a free (warranty) replacement engine?

The 8 year 160K

 

RotaryRes----I've seen this lower compression trend on the rear rotor as well. In fact, I track the crap out of compression numbers on each of our motors before, during and after our races, test events and dynos as a way to capture some type of data to infer any type of conclusions. Ultimately we end up using it to predict that a motor is going South. This is generally validated on a dyno and then at engine dissassembly.

Some of our motors make 130 psi and others 110 and either of these make about the same power. I've always wondered why this was. Any ideas?


The compression test for me

 

Hey Adam,

Yep, we toasted 2 motors at Lime Rock. I think you're right about the above teams losing motors---crazy. One motor was totally our fault, the other one is still being investigated by Scooby Doo and the Mystery Machine gang.

My little bit of research has revealed that the street guys aren't seeing ANYWHERE NEAR the side seal failure modes us Koni Challenge guys are seeing. Most engine builders I talk to can only guess why this is.

 

Its his third rotor its not working right

 

IN my experience/opinion, you do not see an actual loss of power until the engine compression drops below 100psi, or there becomes a disparity between chambers of over 10psi. I used to have the rebuild debate with some rx7 forum guys who swore by using new rotor housings in every build, meanwhile I could build with used housings and make less compression but still make the same or more power by putting the money saved into other areas of the engine or car.

This is speaking more in terms of pre-renesis engines, as I have not had my hands on enough running renesis' to form a conclusion about their tendencies.

 

yeah a 0 is def a problem....I would see the test from mazda and see....with a misfire it prob is time to change plugs/wires/coils but if ur motor is gone then that would not b worht it would it?

 

I call test schenanigans.

 

OH DUDE ILL DO EM! i even got the right socket, + extension, did mine like 3 weeks ago

 

interesting thread; what about the engine core warranty?