I've had the RB CAI on my car for a few weeks now and yesterday I noticed for the first time that the exhaust tips aren't building up soot on them like they were before. I wash my car regularly, including cleaning the soot off the tips of the exhaust (I have the RB exhaust) so I'm used to having to do that each time I wash the car. Yesterday when I washed it I noticed the normal build-up wasn't there. There was a tiny bit on there but practically nothing compared to what it usually is (was). It didn't do this when I had installed the REVi a few months back, so the only thing that's changed the last few weeks is I added the CAI. I did switch to 2 tanks of 91 octane just prior to adding the CAI but had already gone back to 87 octane when I installed it.

Anybody else experiencing this? I use Shell gas exclusively.

 

Same thing happended to me. Really made me scratch my head for a bit. Almost no soot build up.

 

Does this mean the fuel is burning less rich? Can anyone explain it?

 

This is my guess, the first reason is it does help to slightly lean the car out at driving. The other reason is it helps reduce the intake temps, when your cars intake temps get too hot your ecu will dump more gas into the car running it richer to help cool down.

Now it is time to be critized and told my explination is wrong. Oh well

 

ok hang on a sec our cars are ok to run on 87 cause my fuel door says premium only so i've been paying like 3.45 /gal for nothing?

 

I would use Premium. Less carbon build up.

 

Actually it's the opposite; premium has MORE carbon build-up because it burns slower. This is why the gas companies put so many detergent additives in premium.

 

For best performance it is recommended that you use Premium according to Mazda, however you can use regular. Some RX8's (mine luckily is one of them) actually have better responsiveness with regular; many can run it without any detectable change in performance. A few apparently don't run well with it but that seems to be noticable right away if you put regular in it.

Try it. With gas prices climbing like they are little or no change in performance is no big deal if your car runs okay with regular. If filling up starts to exceed $50 per tank, any savings will help.

 

Big debate on this. Ole Spiff is of the side that 87 is no different than 91 (and may even be better). Other side (and Mazda) states that with 87 the engine retards timing and decreases performance of the car. Fine for everyday driving, but will affect high performance.

As to the original question, a few dynos have shown that when the people on this board installed the RB REVi, it did indeed lean out the engine a bit.