About to buy 04 RX8, compression test done
 

Hey guys,

I have lurked a bit and read through a lot of the stickied threads, I am going to be picking up a 04 yellow RX 8 GT with 120ish kilometers (Canadian) on either friday or saturday. I took it into Mazda and had them do a computer scan, used car check and compression test.

The compression test results say Rotor 1: 7.5 6.4 7.6 Rotor 2: 8.0 7.9 7.9 it says within spec but what do those numbers mean, I didn't get to talk to anyone as I picked it up late.

The air filter is dirty should I spring for a K&N drop in or OEM?

The left rear sway bar link is loose I saw some on Ebay cheap ones at like $50

2 REAR Sway Bar Links For MAZDA RX-8 04-08 RX8 | eBay

and some Agency power ones on there for $150ish. The OEM is $240ish, should I go with the cheap ones, stay OEM or the Agency ones? I figured it would be better to replace the set, should I consider doing the front links too or wait till they are worn?

The mechanic recommended I have tranny and diff fluid changed and made a note "limited slip additive for .... diff" that I will have to clarify.

I'm going to get a magnetic drain plug and in the future (spring I'm a uni student) the BHR ignition.

I also made a note asking about buildup and he recommended the engine/intake carbon cleaning.

For the compression results they should have given you a rpm number also. I don't know the exact amount that is bad but I know that you want the faces to be around the same compression. So having that one face more than 1 point below the rest can't be that great.

Agency power should be the cheap ones, I wouldn't trust some random company on ebay.

Your tranny already has a megnetic drain plug. Or it should...

And yes diff fluid is always a GREAT idea.. People will neglect thier diff fluid like its the red headed step child

those compression numbers means squad when u dont know the actual rpm numbers.

its best to drain and flush all fluids on a used car, no matter what the seller has told u.

for air filters, unless you are dedicated to clean it every 3-5 k miles, dont get k&n, get some aftermarket paper filters, works the same and its cheap.

one of the rotor face has lower compression usually means its side seal is going(and or the spring) but right now its not big of a deal.

never buy stuff on ebay unless you know what are u getting into. for that kind of stuff i would rather pay a bit more and get oem, but 220 seems kinda steep. ask mazmart and im fairly sure he can beat that price.

dont do any "carbon buildup cleaning" unless you are experiencing problems.

I will look into the rpm today, can a side seal be replaced? Estimated time line for the side seal getting worse enough to have to be redone, will it like inevitably get worse over time?

how long it will last? no one knows. u make it sound like its strange for an engine to die?

it could be replaced, but requires you to open the engine, and everytime u open the engine, all soft seals will have to be replaced. and. those are not cheap, not even talk about the labor

Side seal can be replaced, but it requires a complete engine overhaul in order to get to it. You are better off either just paying for a full rebuild of the motor at one of the best rebuilders right from now, or just doing an annual compression test on your car to see how the compression degrades over the years.

BC.

By full rebuild by one of the best builders I am guessing you mean send it away?

I was thinking of getting a junk yard RX8 motor and sending it away to be rebuilt just as away to prepare for an imminent disaster and only being without a car for a couple weeks as opposed to like 8 or whatever it would take to get my motor taken out shipped from Canada, rebuilt, shipped back and reinstalled. I can get an engine assembly from a junk yard for 1800-2000. What do they mean by engine core? I wonder if I could get one of those even cheaper than an assembly.

The service advisor said something about getting the injectors cleaned when I was talking about the compression, could there be blow by through an injector? I wasn't sure if that was even relevant to compression but he was like get the injectors cleaned and the motor decarbed.

I might call to get an estimate on what an overhaul would cost, like obviously it would be better to get a completely refurbished, ported and polished motor from a builder but I am curious as to what the price difference would be.

I wish it was like my old motocross bikes I used to race. I used to just do a tear down on the YZs every 10 hours, I don't know much about cars though.

Congrats..

Welcome..

Pictures Please... And, I recommend reading through the threads in my signature. One is written for people who by an 04 (like I did), the other is loaded with a ton of information.

Getting an engine from mazda works but you never know the quality of it. If you go with a reputable re-builder (mazmart is one) then you know the quality is good. Mazmart has their own section on this site in the vendor area, check it out and post in the sticky up top about reman engines Mazmart - RX8Club.com . If the link doesn't work just look in the vendors forums for Mazmart at the top of the main page.

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Will definitely be going through those $100 mods 04green.

A quick copy and paste from a recent email I sent:

The mazda rotary digital compression test tool measures compression in kg/cm^2, which is a metric pressure measurement similar to bar. Usually they should give you 6 values plus an RPM test value...for instance, rotor 1: 6.4, 6.2, 5.9, rotor 2: 5.9, 5.8, 5.4, @ 235rpm. If they can't give you those test results then I wouldn't have paid for the test, because I'm not even sure they did it. It is possible to do your own compression test using a standard piston engine compression test gauge, but you can't get individual face readings like that, only one reading per chamber...but that's still enough to give you a really good idea of where you stand.

You can convert the mazda test readings to a more familiar psi value by multiplying by 14.2. The mazda published lowest acceptable limit for compression in this engine is 97psi, optimal/new compression is about 125-130psi, anywhere over about 100-105 you should be in pretty good shape with this engine.

Its weird that one face (thats how I refer to it right?) of rotor one reads shitty and the rest seems really good, when engines lose their compression does they often do so unevenly like this?

No.

So for the next step of my RX8 journey I bought myself a winter beater today, 91 civic for $400 bucks so that the RX8 doesnt have to face the cold atlantic canadian winter and all the damn salt on our roads. It also means that when I get the money together (maybe next winter?) I can send my RX8 motor off to a builder... Lol also mildly looking into doing an engine swap on the winter beater over the summer if I can get something from a junk yard for 500 or so dollars (the current motor needs rings bad but should last through the winter).

So I guess now I will be looking into proper storage methods for the RX8. Its going to be outside but I am going to get a decent cover, add some fuel stabilizer and take the battery out, will probably put the battery back in start it up and move it back and forth a little bit in the driveway till its up to operating temps like every 2 weeks or 3 weeks.