Hi,

I bought my '04 RX8 a few months ago from the original owner w/93 kmi. It was well cared for, included all maintenance records, etc. I thought the power felt a bit soft at high rpm, which was confirmed this Saturday at a local dyno day -



The blue plot is a 4th gear pull to ~8000 rpm, the red plot is a 3rd gear pull to ~7300 rpm - the dyno operator shut it down before redline due to obvious problems indicated by the curves above 6300 rpm.

Based on the strange behavior at/above 6300 rpm, I'm assuming this issue is related to a problem with the secondary intake runners not opening properly. Anyone know if this is a common/known issue? Any suggestions for addressing it?

(BTW, the car has new OEM coils, plugs, and plug wires w/ less than 1000 miles. Also, new OEM air filter, and the cat converter was checked via recall at 79 kmi and passed - not replaced.)

Thanks -
Keith

 

your ssv is gummed up with carbon! Take it for a couple WOT runs, and that may clear most of it out. Maybe even seafoam (though some ppl are against seafoam, claiming it's junk )
If not, here is a DIY that you can look at

 

That is the APV opening point.

Several possibilities there, but generally, most of them throw a CEL.

 

Your Air/Fuel ratio looks better than stock - is it possible your car has modied software?

 

No CELs since I've owned it, and I put my OBD2 reader on it and confirmed no stored faults either.

Can you comment on which possibilities might not throw a CEL? Thanks for any input / suggestions.

 

I would bet my last dollar it doesn't. It appeared to be 100% stock when I bought it, the previous/original owner was an older guy that clearly bought the car for its looks, took it to the dealer for all service, etc. - most definitely not the type to upgrade the engine software. And I haven't modified anything related to the engine / drivetrain - I'm quite sure it's 100% stock.

 

I've done about 40 autocross laps on the car since I've owned it - it's been at WOT and in the upper rev range a good bit during the past few months.

 

His lambda profile is exactly like stock - 14:1 until 5k and then a steady decline into the low 11's by 6k or so.
Also, dyno tailpipe lambda readings are usually 1/2 to a full point leaner than reality.

Bad CAT, partially disengaged APV valves, leaky or clogged P2 injectors, dirty MAF, etc

 

Thanks for your input MM. So am I understanding correctly that it's reasonable for something other then APV (i.e.: bad cat, leaky/clogged P2 injectors, dirty MAF) to have a major effect on power output only when the APVs are open? Or are you only saying these types of issues can cause reduced power without throwing a CEL?

 

Also, can anyone comment on whether or not it would it be a complete waste of my time to bring this problem to the attention of my local Mazda dealership in hopes of it being covered under the 100 kmi engine warranty?

 

just go there tell then you feel losing power. dont say anything about dyno.