Indeed, it is nice to know. We have a lot of hours invested to find this out!
You would think that, but the injectors have a lot more capacity than what is needed. That is not a bad thing, as it means that if people want to do more radical things later they will not have to worry about having insufficient fuel supply capacity. However what we see in general is that the stock ECU mapping delivers very little fuel in midrange.
Surprisingly too little fuel.
It is on the verge of knocking in midrange rpm, and they are retarding the timing to compensate. By slightly upping the midrange fuel delivery we were able to add almost 3 degrees of advance. This came as a big surprise to us, as we originally thought that the only significant gains were to be made at the top end.
In fact the power gains available are pretty linear from 4,000rpm and up. There is more torque potential lost in the midrange than in the top end.
To get the most from this motor you really have to provide a completely new map from 3,000 and up. I am not going to go beyond these generalities, as we have invested a lot of time, and intend to get some payback on our work!
Actually it is quite a bit more complex than that. They have three sequential intake sections coming online in sequence, but they also have 3 separate stages where intake runner paths, volume, and length are retuned along the way.
For example at 6,000 all the paths are open, but at 7250 a crossover path opens and shortens the effective intake tract length by half.
Heck yes! Along with exhaust temperatures, and now we are working on road condition ram air effects. There is significant gain to be had as the stock intake has a marked ram air effect, but it is being throttled by the exhaust.
The next step after the fuel/air and ignition is completed to our satisfaction is to re-run a lot of it with a less restrictive exhaust system. That will have significant effects on the maps. I can say that if anyone were to just bolt on a semi-wide open exhaust they will be rather disappointed with the results. The port tuning on the Renesis favour midrange power over top end. I expect to see best tuned horsepower will fall very close to best torque levels, in around the 5200-5500rpm range once fully utilized.
I also expect to see some gains to be had with dual path exhaust tuned like an expansion chamber.
The flow patterns of it are eerily similar to a 2 cylinder 2 stroke piston port motorcycle engine.

The potential of this engine is simply huge. When we started we did not expect it to respond as easily as it did.

I feel it is quite feasible to make 300HP on this engine naturally aspirated with no internal modifications. It flows very well.

Once people build up racing versions of this I expect to see a lot of surprised faces.
The biggest limiter on the potential is probably the transmission. RX-7's had a bit of a rep for having glass trannies, and I don't know how much stronger ( if any) this one is.
At 260HP it should not be an issue, but at 300+ ? scary.
Having a lot of fun in Edmonton!

 

One thing people should watch out for if they do any serious work on the RX-8 is to keep an eye on the exhaust.

After doing some hard runs with improved fuel/air, and ignition, we noticed a funny smell coming from the rear.

Let's just say that the accessory that you can buy that is a metal insert around the exhaust tips is potentially more than an ornament.

Take a look at this picture:

 

Alright, just a quick dumb quote...those have to be some darn hot exhaust gasses coming out.

 

I understand the need to keep the information you are doing the work for to yourself.

Thanks for sharing what you can!

Vince

 

Yes.

When we did this we had the cats removed and just the muffler on the exhaust.

The setup was fuel/air tuned and it had some advance on ignition.

The gases coming out were VERY hot. I would bet that with a racing exhaust and a tuned engine you would see flames coming out at least at night!

The plastic is too close to the tailpipes.

The part one would need to install if leaving the stock plastic in place and running a full race ehaust is this one:

 

That does it!!!

A big fat single flame throwing centre exhaust it the go ... just imagine toasting the pedestrian that walks behind your car ... literally

 

I'm confused about the lean midrange part of the maps. Doesn't this run counter to the concept of running it rich in order to save the cats? Or is all of that bogus too? :-(

jds

 

The situation with the heat would only occur on a car with essentially wide open exhaust and extensive installed performance mods.
In other words not what you would run on the street ( at least I hope not!)

Watch some GT or F1 races on TV or at a track and you see the same thing. Some of the endurance races, such as 24 hours of LeMans are a great example. Flaming exhausts, glowing brakes, sparks from undercarriages.. Cool stuff.

As far as the question about lean/rich situation and the cats, they run lean where the engine is at lower rpm, and flowing less volume of gases, as the cats are not getting as much heat from the exhaust ports at lower rpm.

When you open the throttle and increase rpm the total gas flow goes up fast, and they had to add more fuel to cool it down. This has resulted in bad gas mileage at higher rpm, loss of power, and that black smooty stuff we see on our tailpipe tips.

In essence the tuning is being done with a goal of keeping catalytic converters at their ideal temperature for maximum emmissions performance at all rpm ranges.

They are NOT being tuned for producing better gas mileage or horsepower.

While I am neither a tree hugger or an SUV driving gas pig, the emissions tuning they are designing for is for the most strict jurisdictions, such as California, and not for places with less strict regulations.

The work we are doing and soon will be offering to other owners is designed to operate within the specs for the majority of North American jurisdictions, and would not be legal in all places.

We are also tuning to work with mid grade or high grade fuel. In other words 89 octane or higher.

Mazda has tuned ignition timing and mixture to be safe and knock free even on 87 octane gasoline.

Different design goals produce different results.

 

Best post yet! Right on the money.

 

I've been meaning to post something about the economy/power/emissions issue for the last few days but haven't had the time to do so.

Mazda's goal for the RX-8 was for it to have much better mileage than what it currently has and they meant for the motor to run lean. They have spent years developing the catalyst technology to work with a lean running side port rotary.

SAE article 950454 : "The Characteristics of Fuel Consumption and Exhaust Emissions of the Side Exhaust Port Rotary Engine" has a wealth of information regarding the economy, emissions and power performance of a side-port rotary. You can find it on the web although people that buy it aren't supposed to put it up for public consumption.

Be very clear that emissions regulations are what has drastically lowered the power of the RX-8 (from the original 280 of hte RX-Evolv). The main problem is that the new regulations for new and upcoming cars require that they be able to pass strict tests at 50,000 and 120,000 miles.

Mazda has made great strides in catalyst technology in the last 10 years. They developed the "world's 1st 3-way catalyst for lean-burn engines" and in 1998 developed another 3-way catalyst that "starts to purify pollutants from a 70 degree (C) lower temperature than current catalysts" and has a heat resistance "100 degrees (C) higher than current catalysts".

The side-port rotary actually produces more power at the leaner ratios. (See attached graph) Mazda has also released info (a year or 2 ago) that states that "the RX-8 operates with a lean mixture even during high-speed high-load operation."



Despite the the capabilities of the Renesis and the advancements Mazda has made in catalyst technology, we are not seeing the full potential in power or fuel economy of the RX-8 because of catalyst longevity.

For those people that do not believe that the renesis is running rich to preserve the catalytic converter, please also note the below which was released several years ago by Mazda regarding catalyst longevity:

"Current three-way catalysts are located as near as possible to the engine in order to make the temperature of catalysts rise sooner. But, under engine conditions such as high-speed driving, deterioration of the catalyst accelerates due to the high temperature of exhaust emissions from the engine. Usually, the temperature of emissions are lowered by injecting additional amounts of fuel into the engine's combustion chamber."

The potential in fuel economy and power IS there. The RX-8 has the potential for great power increases and fuel economy improvements with the lean mixtures it was designed for. As mentioned before BWOB has written about how difficult the EPA testing process is. Hopefully, Mazda's engineers can take the RX-8 to the next level if they can overcome the catalytic converter longevity problem.

Brian

 

Canzoomer:

Am I right about about how the secondary injector contributes?

Curious in Auburn...

Vince

 

So assuming you can lean out the mixture to produce more power then you're running the risk of destroying the cats prematurely and not being able to pass emissions? Anyone care to venture a guess on when that might happen? How much are replacement cats?

 

If I read correctly...
The cats were moved up close to get them up to temp quicky for Cali emmisions test. This results in higher Cat temps at higher RPMs.

So, Why couldn't someone not concerned with the quick warmup issue, move the cats back. This could allow us to run less rich at higher RPMs while still keeping the cats cooler.

Is this not an option?

 

well, you "couldn't" because it's illegal to change the distance of the cat to the engine (thanks DOT!!)

anyways, if you really want to save your cats, you could always replace them with a straight pipe for competition, then put 'em back on later for normal driving... or whatever, leave 'em off other than for tests... *shrug*

best way to save cats is not to use them...?

 

Except that running without cats would probably throw a few CEL codes.. and if you ever get caught, in the Toronto area anyway, they pretty much give it to you up the pipe, so to speak. Big crackdown around here on those kind of mods.. $5000 fine I think for tampering with emissions systems?

Also if you've ever seen a city under a smog alert that alone should convince you to not run without cats.. I wouldn't do that just to gain 20 hp.

 

The cats are moved up close because of EPA testing that measures emissions just after startup. I believe this is a national issue not a California issue. Manufacturers have to be concerned with the quick heating of the catalytic converter because the EPA says they do.

Like it or not, emissions regs are getting tougher every year (in the US and worldwide).

Unfortunately many engineering goals are contradictory in nature. The cats need to be hot at startup so that they can start working... but they can't be too hot at high revs or they will deteriorate faster. You can see that the close cat placement and the double-skinned exhaust manifold before the cat help startup emissions but end up hurting high end power if cat longevity is a goal.

Brian

 

First let me say emmisions is a joke.Ever been behind a 20 year old dumptruck as they drop 20lbs of carbon in the air before they even move.Second how the hell do you ever get caught running without a cat?Personally i cant see your average traffic cop getting on the asphault to look even if he knew what he was looking for in the first place.

 

They do look in Cali, then it's a call to the REF to get your car inspected.

A lot of times, it's just inspections for "rice" looking cars, or people they can actualyl pull over at the illegal races.

 

you go to get your emissions testing done and you don't pass. they see that you don't have a cat. and i have seen cops lay down and look under a car to see if the cats and/or mufflers have been removed.

 

You are absolutely right.

It realy depends on who you are and what you look like and where you are.

I am 47, white, and live in Alberta. My chances of an inspection are slim to none.

If I was Asian, 21 , and lived in California i would drive ONLY stock, and probably a K car!

 

Sorry officer, I guess i was not paying attention to the change is speed sign back there.
Thanks for the warning. I will not do it again.

BTW Officer Pete, are you and your wife coming out to the golf club this Saturday?

 

Canzoomer, thanks for the chat the other night.....love to see the car when you get the fuel controller hooked up.........I will be buying one when I get my 8........another 20-25hp only adds to an already great car!......went out today in a G-35 coupe with a friends who picked it up today.......nice car, but made me more thankful I got the 8.....probably just as fast stock, but with 25hp more, there is no comparison.....just my opinion.......

 

Just don't get a blue one!

I am getting used to the exclusivity around here..

 

don't worry, my 8 will be black!..........I'll touch base with you in a week or so, and maybe we can go for a spin........you have me curious how much more zip the mods give it !

your car looks great!

 

nice pic canzoomer