Your right, rich can hurt the cat, and has caused problems also. I'll have to test the exhaust gas temps once I install the interceptor and see how bad it is when i lean it out in cruise mode. Scott said the Renesis can go as lean as 15.5 - 15.7 before the engine starts stumbling. I know people with FD's that cruise at 16-17 AFR, I have to imagine that would cook a cat rather quickly.

 

they're only cruising though, which means low total heat mass output. You're making assumptions ...

 

So, this was a catless tune, right?

 

^correct

 

OMG a one word answer from RG!! Goodby cruel world.

 

So where is the 3-5 more rwhp due to the exhaust system going to come from

 

they are using the OE manifold as req'd by the rules

you can get the same power with a cat, you just have to use the appropriate one

 

My disappearing curve is due to the dyno not picking up the RPM signal. But your right, the torque carries out pretty broadly I must say.

 

No cat and a better flowing muffler.

 

Trust me, you can get plenty of cat damaging heat at low throttle settings. On my RX-7, I've gotten a cat to glow red hot at idle from an improper mixture! I don't really think there's any assumptions about it. Your assuming that only higher throttle and load levels have the energy to hurt the cat and that's not true. The mixture itself has just a large effect on exhaust heat than the rpm and load level do.

 

The exhaust builder (not the team) hollowed out a factory cat and welded a 3 inch tube to the back of it. Pretty weak attempt considering you are not allowed to do much else to increase the power output.

 

Any updates - I know, it's easy to type on a forum keyboard as compared to the real World.

 

Hey Scott - I'm back it seems

I think I will hold off a few years for forced induction. The backroads around Aberdeen up around the Olympic National Park are a blast with my setup, so I think I will tune a NA further. Waiting on Brillos report. If I fly you up here, I need to know if you like the outdoors

 

^ When it looks like that, Yes! I might even try this "relax" thing I have heard so much about

 

You could use a little R&R maybe - that was Middle Mildred Lake that I hiked to last summer.

 

Yes, but it seems that you're talking about a grossly improper mixture and I'm talking about reasonably near stoich. plus glowing red can only be 1500-1600 degF. There are cats out there than can handle near 2100 degF continuous, so "glowing red" really doesn't mean much without an actual measurement. Further, the exhaust gases on the Renesis are lower than the previous RX-7 engines thanks to the new port configuration. If you pursue overlap porting this may change, but it remains to be seen.

There is still heat mass to be considered, this is simple physics. High temperature with low flow is more easily dissipated as opposed to high flow and high temperature. You'll have bigger problems than a fried cat if you try running that lean for anything other than the lightest load range.

 

As far as I know, Scott is still waiting to get critical ECu parts from Australia, I think I'm in the next batch? Believe me, I can't wait, I'd like to be able to use 87oct and get better mileage.

 

looking forward to following your progress, best wishes for your success

 

I am under the opinion that if we add overlap to these engines, we will lose horsepower and not gain it. I think overlap or lack thereof needs to be re-studied.

You are assuming that small changes in a/f ratio can't have large changes in exhaust temperature. Again not necessarily true. A lean cruising mixture can kill a cat as fast as an overly rich one. Mazda actually runs the car overly rich to cool the exhaust down somewhat and not the other way around. The cats are dying because they are crappy cats. The extremes on either side will result in a very hot mixture. We've seen cats fall apart just from bad materials that had nothing to do with extreme temperatures. Simple physics also has nothing to do with shoddy build quality.

I still say everyone should run around with no cars whatsoever and run as lean as they need to to make the best power and economy but some tree hugger would probably get mad at me for the suggestion.

 

OK guys, the last posts are about how a catalyser is dead by lean mixtures, etc.

Now, has anyone run an RX-8 catless with the interceptor-X and tunned for max power (or leanest mixtures) at any speed/load?

Any real figures of power, drivability and mileage?

Cheers

jird20

 

Quick question here sorry for being a newb but im not very technically inclined when it comes to cars but i would like to see some of the incresses that have been discussed here. How much do i have to know to get the interceptor-x.

 

You don't have to know anything to GET it, but you have to know "something" to use it...

Whether it be you that knows how to tune, or you knowing someone that knows how to tune. Buying one will be completely useless unless you can tune it.

 

yes,
that was the whole start of the thread.... my car was run with the cepter x with a borla resonated midpipe. max hp was 205 at the rear wheels, but it picked up over 22 hp in a large part of the midrange... is that the answer you are looking for???

btw, start reading at page 32 of the thread... all the answers are in that area.

beers

 

Logged some cat temps today with the CANScan.

Indicated 1650 degF with O2 oscillating between 0.99 and 1.01 lambda while cruising at 40 mph

I didn't have the opportunity to do any extended WOT checks, another day ... a couple of short bursts and it never went below an indicated 0.85 lambda, pretty sure the most recent flash is installed ...

 

1650 degrees is as much heat as most street piston engines produce at full throttle.