Hi everyone,

I'm new to rotary. Recently bought a 8.
Had the engine compression tested and it's 7 on both chambers.
is it ok for a 2005 rx 8 with 35000 miles on the meter?
Is there anyway to improve the compression of the engine?
I found out that it's quite hard to start my car (especially hot start), it needs a longer cranking time before it wants to start. When doing a cold start it needs less time but still approximately 3-5 cranking time.
Thought it's the battery problem so changed it but there isn't any significant improvement ( maybe a little bit better than before)
Any idea?

Hope you guys can help me out with these.

 

Get the full compression numbers. You need 3 numbers for the front, 3 numbers for the rear, and the RPM of the engine at the time of the test.

7.0 is 0.1 above failing if the test was at 250rpm or higher and compression loss is the issue. (6.9 @ 250rpm on any 1 of the 6 rotor facings is a failing grade)

If the test was done at 200rpm or lower, then 7.0 is incredibly good, and your starter is failing, causing the issues. (faster starter speeds increase compression)

If it was somewhere in between, then it depends on where the rpm was really.

 

The mazda dealer who did the test for me only gave one number for each rotors. when i asked them for the other two they said they were using the digital testing device which i dun really know what they meant. they were testing it with 220 rpm.

with 220 and the result at 7 does that mean the engine has a bad compression?

 

have you changed your plugs, wires, and coils. At 35k, it's possible that none have been changed and they are probably due. Coils can cause hot start issues too.

 

no havent change any of them yet and i doubt the previous owner did that.

p/s i feel so welcomed in this forum ^^ seems like a big family here. everyone is so helpful here ^^ enjoy it so much and happy that i got myself a 8

 

Such a contrast to this new owner here: https://www.rx8club.com/series-i-trouble-shooting-95/hot-start-failure-long-crank-times-225081/

Read it for some laughs, and the flip side of how we treat people.


Anyway, this is the chart you need to reference for compression results:


At 220rpm, your failing point is about 5.5, so a 7.0 is very acceptable. (My earlier quote was inaccurate I think, if the line means failure), so I'd say most of your problem has to do with the starter, and possibly also ignition. Your starter definitely cranks slow, and increasing the starter speed (with a new one) will increase starting compression and resolve much of your problem.

 

thank you so much RIWWP and rotarykillz ^^ lucky to have both of u here. i will try to get the starter check and fix soon ^^ thx a lot time to go to bed now ^^ enjoy

 

Always start with fresh maintenance items just so you know what has been done if problems arise later. The dealership should have shown the results of the test.

Welcome aboard. Generally if you do your research before asking questions and don't cop an attitude you will be helped out by many, many knowledgeable people. The only time I get annoyed is when people do not search and then ask questions that have been asked a million times.

 

sorry , i will try to do some search before i ask next time and anyway still thanks a lot for helping

 

No need to apologize, I wasn't saying you were one of those people, just making a general statement about noobs who just start new threads without researching at all.

 

welcome again,

Recommended reading in my sig. The $100 thread is a good place to start for a 6 year old car, I learned that stuff when mine was 6..

 

04green ^^ i like your post ^^ it rocks ^^ thx so much

 

Yeah...thanks for that guys. I wasn't exactly welcomed at first. Oh well. Not a new owner either RIWWP, was just new to this forum although I've been reading it for awhile. People are actually starting to help now that they realize I have been researching and testing.

Harry, if you have the cash, the BHR ignition kit would be a good purchase since you're looking to replace the coils and wires.
http://blackhaloracing.com/?page_id=...&product_id=19

 

I actually linked that thread more for the other guy that threadjacked your thread

 

The latest digital compression tester from Mazda has a dual readout. One for "Front" chamber and one for "Rear" chamber. It tests both chambers at the same time. It then displays 3 separate compression numbers for each rotor.
So I wonder why they supplied just one number per chamber.

Welcome to the RX8Club.

 

Thx jayp i will look into it ^^ gonna change it soon. And thank you everyone who posted here thx for all your suggestions and advises that means a lot to me ^^ thanks