and the numbers are.....

at 250rpm on a hot engine, i got

R1
6.7
6.8
7.1


R2
6.7
6.4
6.9

factory spec is around 8.0 new and minimun is 6.9

so, um, shes uh, erm.....ugh......yeah.


which is weird bc it doesnt idle bad, starts easily and has no real runnin probs. but some of u may remember a thread a few weeks back about me runnin it on the dyno and gettin 160 whp at 6,000 rpm as my PEAK. after replacing the coils i wanted to run a comp check to see where i stand....

um....yeah....there ya go.
its an 06 MT with 29k had the 4206f recall done in november of 06.....

any thoughts?

 

Looks like you are just borderline of meeting factory specs. Did you do this compression check yourself?

 

yes

 

You have a Mazda compression tester?

 

yes

 

Are you running pre-mix?

 

i did for like 3 months about a yr ago but was afraid of what itd do to my fuel pump so i stopped. i used pettits mix. didnt have any issues, in fact i still dont, but the way the power trailed off after 6k on the dybno made me think twice about the compression.

i work for mazda so gettin my hands on a rotary compression tester is as easy as walking 12 feet and opening a drawer.

im pretty sad about this bc i love my rx8 and its little wankel wonder....i hope its warrantied!

 

if you work for Mazda, cant u just make some bs up and Mazda will cover it ?

 

How have you treated your engine over those 29k? Any mods?

 

intake. UR pullies. those r the only engine mods, i went heavy with chassis tuning. changed the oil every 1-2k miles, shell v power (93), saw high rpm daily

 

Only with the rx-8 did mazda raise their minimum compression standards to ~96psi. With all previous rotary models it has been 85psi. IN my experience, rough idle and hard starting tend to happen in the 90-95psi threshold. This explains why mazda raised the standard. You guys are actually lucky that this happened, otherwise more of you would still be running weak engines until they dropped below the older minimum spec.

The change in spec is not due to the renesis design changes, none of which affect static compression generated.

 

I remember reading your other thread about the lower than expected numbers from the dyno run and it makes me wonder how my engine is doing as well, since I have never had it dynoed before.

 

I would put it back to stock and take it to the dealer for warranty repair. The cost of the RX8 rotary engine would make it worth it.

 

seeing as you can do the test so easily - how about getting some decarbonizing cleaner (like bk44 ) and give it a real work out then a retest .

 

First fix your power issue. The compression you have does not justifies the bad performance of 160whp. I have seen a lot rexs with your compression having 185+whp. So check your coils, spark plugs, gas pump, cat. Then dyno again your car and if your numbers are good go for a descent red line couple of times and THEN take a compression test.

 

ok, im likin the input ppl....

i changed 4 coils, the leading plugs (went back to re7c after using re6c, the 6s are a hotter plug and unneeded for crazy driver me) chekced my cat, its front:rear switch ratio is 0.5xx and max is 4.xx so its fine....

i ran the dyno when i was on sunoco 93, the only reason i was on sunoco was for that one tank bc there were no shell v power around when i was empty....i use shell v power 93 but not on that dyno...maybe it knocked and it pulled timing? dunno.

when i ran the comp test i brogutht he car into the shop stone cold, so i let it idle for about 10 mins to get hot, then did the test......think i should beat the hell out of it to get the mop flowin before i do the test again?

that sounds like a good idea bc i was taught if some rx8s were readin low comp after the test they wanted me to run the mop at its highest step ( 60 ) for about 5 mins and then let it idle for a few mins then do a retest.....they wanted the added oil to go in and lube it up real good then do a retest....maybe thats what i should do.............any thoughts

 

How did you run the MOP at high output?

 

I want to know how you turn up the MOP up to 60 also. I was watching the factory laptop, and under full load I couldn't get anymore than about 23.
If you can answer this you will have solved one of the great mysteries.

 

also, wouldn't that kind of be cheating on a compression test?

 

Dumping oil in on a compression test will of course increase compression. Due to a better seal (oil).

 

yea, thats what i mean. Thats like doing a "wet" test on a piston motor. But that is generally onjly done as a troubleshooting measure, not a technique to get a motor to pass a compression test.

 

The WDS (or whatever its called now; MDS?) has a menu for cranking the MOP all the way open. That is part of the recall test procedure.

 

did you tun off the TCS system and pull the room fuse when on the dyno?

 

That's it? Darn.

 

Not necessary.