Hydr0nium

Got a compression test done on the car I am interested in getting at the end of the month. Here are the results:

Front Rotor - 8.0, 8.1, 8.1
Rear Rotor - 7.7, 7.7, 7.8
at 328 RPMs

minimum compression is 6.9 and max is 8.5

If someone could help decipher these for me, I would appreciate it.

I know it is important to look at the numbers per rotor to see if the seals are wearing evenly, but the rear rotor seems a bit low to me.

This is a 2006 with 17K miles on it.

alz0rz

iTrader: (41)

Looks decent given the mileage, though I'd have expected a bit more with those RPMs. I'd bet a decarb would only help.

Charles R. Hill

iTrader: (7)

Here is a chart.

What is your idle vacuum and what is your altitude?

Hydr0nium

I don't have the idle vacuum, the current owner of the car took it to get the test done, so I don't have direct access to the car.

Altitude is ~5300 ft.

MazdaManiac

iTrader: (3)

That is a good compression test result for that altitude.

Hydr0nium

Great, thanks! Looks like I'll be getting this car at the end of the month then!

pistonhater

Please check your PM.

Thanks!

pistonhater

Sorry to hijack the thread, but I didn't want to start a new one on the same subject.

After reading these posts I decided to go back to my compression test results just for the heck of it. This is what I see on the paper:

Front Rotor: 7.0, 7.1, 6.9
Rear Rotor: 7.1, 7.2, 7.0

The test was done at 250 RPM.

Needless to say, I am very discouraged. Based on what you guys are saying, this is way too low - especially for a car that has less than 15K.


So....just to confirm....do I have very low compression?

Thanks a lot guys.

gwilliams6

You are right, from the posts here, the numbers should be in the eights at 250 rpm. (I have never had a compression test of my 40th Anniversary edition-but I bought it new and have had no issues. And since the Renesis engine is the highest compression NA 13B Mazda has made-my ownership of six previous RXs won't relate on the compression numbers) Give JPR a call right away and talk with him about your results. 856 227-1808

bse50

the min. acceptable is 680kpa at 250rpms so technically you're ok.
The fact that it's not "optimal" doesn't matter much to them apparently. If it's within spec, it is ok.

nycgps

iTrader: (1)

Front Rotor: 7.0, 7.1, 6.9
Rear Rotor: 7.1, 7.2, 7.0

if the test was really "DONE" at 250 rpm. like bse50 said, it's "OK" , but not Optimal.

your car is fairly new and the engine is already at "this" state ... it could be badly carbon up, especially if its in NY + the previous driver is a moron and drive it like a grandma.

Edited : Just noticed your sig and your location, you bought a used 40th annv edition? so u should have plenty of engine warranty left. and you're in NY/NY

Where u got ur 8 from?

as for trying to sue the dealership/Mazda for this, EVEN the engine has low compression it's pretty hard to do it, cuz there are so many ways to manipulate the compression test results. so you are going to have a hard time to proof ur case.

if for some reason you want to double check your compression numbers, pm me and I can help.

pistonhater

Cool, thanks. But damn, it is so close to be out of spec that it makes me wonder

Thanks for your response.

The car was probably driven like a grandma. I bought with 1311XXX miles on it. Kind of low miles for an almost four year old car. The car was in great shape, that's why I bought it.

I was not thinking about suing a dealer, but I would consider making a lot of noise because I happen to know a very good lawyer in Manhattan. I feel they lied to me, when in reality they should have said the compression was rather low. I do not appreciate being lied to. It is not professional practice for business.

I would be interested in another compression test if you can do that. Will send you a PM.

The dealer was Koeppel Mazda in Queens.

bse50

at 131000 miles you're lucky to still be on the original engine
If your quest fails you might consider taking some time to save up for a good remanufactured engine and have it tuned with an accessPORT and add new coils\plugs to the mix. Around 5k$ worth of stuff but you'll be good to go for a loooong time.
The better fuel economy could easily reduce the total expense over time.
Long shot for a car that's barely worth double of that, I know. Owning a wankel requires dedication :p

nycgps

iTrader: (1)

1311XXX ?! it has over 1 million miles !?!?!?!?!

well, assume u mean 131K miles, and it's just 4 yrs old, that means the car had like 30K something a year, it's probably all highway miles, not bad.

rofl Koppel Mazda. yeah I know those ***. I was forced to get my Mazda3 from them simply because they are the ONLY dealer in the tri-state area to have the color and trim that I want, and those fking ******* still owe me 130 something bux which they promised to send it back to me but they never did.

I mean that's ok, it's just that no matter what happens, I will never Buy another car from them, that's all.

I only had 1 Experience with their service department, when I was still a noob with my 8, they gave me a load of bullshit and charged me an hour of labor for doing nothing. things might be "better" now it's been like 6 yrs, but a compression test coming from this dealership ... I wouldn't trust them UNLESS I see them doing it in front of me.

how much u paid for the car anyway ?

pistonhater

I made a mistake about the miles.

I just looked over my bill of sale.

The car had 13179 miles, LOL

Sorry for the confusion.

I would consider all the things you mentioned, but I have a **** load of warranty left on the car. Beside the standard 8yr/100,000 engine core warranty, I have another 70K on power train.


Sorry, once I again, there was a typo on my post.

The car only had 13,179 miles at the time of purchase. It has 14,959 as of this morning. So in 3 1/2 years the previous owner barely drove it. I started pre-mixing and redlining the car everyday ever since i bought it

The car was barely driven as demonstrated by a recent engine code - misfire on the rear rotor. A local Mazda service department found one of the spark plugs "dirty" and the tech told me I needed to drive the car "harder" to keep the engine clean, and that it seemed like the previous owner didn't push the car enough.

And yes....Koeppel Mazda sucks big time. They sell so many cars that in reality they don't care about a "personalized" buying experience. Would you believe me If I tell you they made me wait 4 1/2 hours the day of the closing mostly because they had so many people buying cars that you had to literally wait in line. Ridiculous. I almost walked out but didn't since I really didn't want to let the car go.

I would NEVER buy from them again nor would I encourage anybody to waste time going there.

The only reason why I went there is because they had the only 40th Anniversary Edition available in a 100 miles area with such low miles. It was the car I wanted for the price I wanted. And quite frankly, minus some normal road rash on the bumpers and some wheel scratches (previous owner didn't know how to park, LOL), the car was in excellent condition. As you know, pre-owned certified cars are usually in great shape. To me, the car looked basically brand new.

I paid slightly under $20K - including the Mazda Pre-Owned Certification. At that price - at the time of purchase - the price was almost $3k below book price, so it was a "decent" deal considering it came with the extended warranty from Mazda. I checked with many people and online sources and everybody told me the price was right, so I bought it

But I am now nervous about an engine that is border line below compression standards

However, as I said above, the car drives great, no hesitancy, no issues with hot/cold starts, etc. As far as I can tell, the engine pulls and behaves as it should.

I just want better compression numbers!!!

77mjd

Anyone know how to convert the psi# to the 2 digit number? The readout I have only shows the rpms and psi number for each chamber.

Hydr0nium

I believe you are looking for kilogram-force per centimeter squared.

1 psi = .0703 kgf/cm^2

77mjd

Thanks...then here are my results at odometer 99,300 miles (about 66.5k on 2nd engine). I just wanted to get it checked before the warranty expired.

Front rotor: 8.5, 8.5, 8.4 @268 rpm

Rear rotor: 8.4, 8.3, 8.2 @266 rpm

I replaced plugs, coils and wires around 90k. Now at 114k and still runs like a champ. Basically, I've been problem free since having the engine replaced around 35k. The biggest issue I have now is the lips on the rear wheel wells starting to rust.

gwilliams6

Good post here of what the compression numbers are, what they can be, the Mazda specs, how it is measured and calculated and also the incidence of error in the Mazda testing. There are many variables besides the rpm and intake manifold pressure. Things like altitude, temperature of the engine, mileage , the type of instruments used , etc. There was also a recent post where a rotary compression testing instrument manufacturer was offering a group rate to RX8 club members on his latest electronic unit. It was around $300 for the very nice unit. If I can find the post, I will repost it.


https://www.rx8club.com/showpost.php...6&postcount=41

Hydr0nium

After doing some more research, it looks like the altitude variance for my elevation is .853 of a sea level test.

So my adjusted results (in psi) would be:

130.5, 132.2, 132.2
125.6, 125.6, 127.3