Hello guys and girls!

I have some concerns and I hope you can help me. I live overseas, in Germany, and bought an 8 in July. So far I really enjoy this car! It had set from November '11 until July when I bought it. I decided it would be best to take it to a Mazda Dealer and have it checked. I had the entire vehicle checked, as well as the Cat and the compression of the rotors.

Well when I went to pick up the car, the mechanic told me that the car had some minor issues (since they check every nook and cranny, I was not surprised) but then the mechanic confronted me with the big BUT! He said the rear rotor had a low compression rate. He went as far as saying that I should give the car back.

I had signed up for a local RX 8 forum and they all told me the numbers are low but nothing to worry about. But I just find them to be very unfriendly at forum so I hope I can get some better advice from you guys.

I am a person that drives short distances (about a mile to work) and once in a while I will drive a long distance. The Germans told me that I should not keep the car if that is "all" I do, but I want to keep it. I do follow the regular procedures, such as letting it run a bit before I drive and to not punch it when it is still cold. I use Premix and I make sure to check the oil. What do you guys think?

Also I had a question about the fuel consumption. I know this car eats a lot of gas! But when I fill up my 8, its about 50L or about 13 gallons. Now with a full tank and the drives I do, I get about 167 miles (270km) until I have to get gas again. I expect a lot of fuel usage, but this is a bit too much isn't it? I already changed spark plugs, cables and I use premix. I understand short distances will cause high consumption, but when I even add in a longer distance, I only get shy of 300km (186 miles).

Well I hope you guys and help me with my "worries" and not make me feel weird like they do here in the German forums haha

Thanks!!!

 

Buying a car with low compression on the rear rotor is not a good idea unless you are budgeting for a rebuild. That mileage is horrible for a stock RX-8, I don't see that you ever changed the coils, you should do so. Also, they tested the car but what were the results of that test?

 

Well, since your trips are so short, one thing I'd do is schedule some nice, longer rides regularly - several times a month, if not more. Just for fun. (I mean, that's what a sports car is really for anyway, no?). Who knows—this might improve your car's performance. And it would be interesting to see how it affects your fuel consumption.

 

Low compression is low compression, it will only get worse and usually is worse in the rear due to heat.

 

+1 on that ^

 

Hi - I have a 2003 RX8 auto. It has deloped a leak and the water is pooling in the rear driver's side (r/h side) passenger foot well. There are no signs if water running down the foot well
sides only pooling so I am assuming either there is a leak from the floor pan OR something like the sun roof drain pipes are somehow running into the (RHS) footwell.

Can you please give me some advice as to where I should start my inverstigation?

Many thanks

Swant2 (RichardS)

 

Well when I bought the car, I was not aware of the low compression. From what I was told the numbers ae not too low. The rear rotor had a compression rate of 6.5 Bar U/Min, which is the rotations a minute... I hope that makes sense, as it was a German dealer.

Yes, I was going to change the coils next. I basically had a CAT test done, as well as the compression test. Both were fine except for the rear rotor. The front rotor is perfect.

Could it also be that the car was setting that the compression may go down? I have been driving it from July on.

I know the miles I am getting are pretty low, and I hope they get better... I want to keep this car

 

Maybe if you cross your fingers and wish upon a star the compression will get better

It is what it is and will only get worse. Do you have a copy of the results of the compression test. There should be a value for each side of the rotor face along with the speed of the engine. So there should be three values and rpm for the first rotor and then the same thing for the second. If you post these numbers it would help to know how bad your compression really is.

Something like this:

Front rotor:
5.6 Kg/cm2
6.0 Kg/cm2
5.9 Kg/cm2
RPM= 285

Rear rotor:
6.2
5.9
5.8
RPM= 269

 

6.5Bar would be about 94psi, which would be below spec if the test was done correctly.

http://www.flickr.com/photos/9krpmrx8/4497702781/

 

9k, correct me if I'm wrong, but driving just short distances too will be hard on the motor since there will be a lot of carbon build up since it won't get a lot of heat to burn it off, unless he drives it like an autox course.

 

Generally yes driving short distances is bad. I have to let my 8 warm up for a good 10-15 minutes to get the oil temps up to temp. So if you just hop in and drive a a mile or two your oil will never get up to temp and none of the contamination in your oil will ever burn off. Some of the additives in modern oil don't "activate' until the oil heats up so if you never get it up to temp you might as well be running the cheapest oil you can buy. So if you must drive short distances and do not warm your car up each time then you had better change it often.

 

Well.. if its heavily carbon coated, seafoam or mazda zoom zoom stuff would improve compression a bit, no?

by heavily carbon coated I mean, seals are sticking.

 

No.

 

Damn.

 

Well here are my results for the compression test. Again they were done here in Germany so I hope you know what it means :P

Rotor 1: 7,4-7,6-7,7 266U/min
Rotor 2: 6,5-6,5-6,7 267U/min

Well I don't just hop in and drive. I let the car run for some minutes, or until the idle goes down to 1250 RPMs. When i drive I don't go over 3000 RPMs until the tempature is at optimal.

 

Oh goodness, driving a car (any car) cold, and shutting it off cold is the worst. Fuel contamination in the oil and all that. I'd say just ride a bike, with that short of a distance.