can u add a intake to the rx8 because it opens diffrent valves at diffrent rpms?. And if so it would prob sound like a vtec

 

...do some searching and research on this: you'll realize that a CAI (rolleyes... hard) probably wouldn't be a good comprimize for this car...

 

No it wouldn't.

 

becuase the hodas with vtec have diffrent timing just like the rx8 at a certain rpm range

 

Now, do you mean "sounds like" as in aurally, like a VTEC, then it's still no--piston and rotary exhaust notes are very different from one another, regardless if they are NA, FI, VTEC, or otherwise.

Of course, if you meant "sounds like" conceptually, then perhaps so, however still unlikely. The intake system on the 8, at the moment, seems to be tuned very well to maximize the engine's performance at each area of the powerband. A CAI may not have as big of an effect of performance on a RENESIS as it would on a VTEC'd piston counterpart.

 

Are you mistaking CAI (cold air induction) with the standard tube and filter that all the Ricers like to slap on their car? The reason I ask is a true CAI will drop the intake air temp and increase the density of the intake charge. A piston engine and a rotary will respond exactly the same to this density change. An ~7 deg F drop in intake temps will correspond to a 1% power increase.

Of course, the RX-8 intake system seems quite sophisticated and may already have CAI. If so, there will still be guys that make the old tube and cone filter. They may even get a few extra ponies on the top end but kill the low and mid ranges.

 

Why is a CAI a compromise? I currently have a 00 Jetta VR6 with an AEM CAI and it's increased my fuel economy and hasn't affected the pull at low engine speeds, but increased the pull at WOT during higher engine speeds. I would think that colder air is the goal for any combustion engine, which in turn would create a much cleaner, more efficient burn.

Please correct me if I'm wrong with the rotary engine. I've done a lot of research regarding the development and function, although haven't gotten into the modification scene of it all that much.

TIA
James

 

...Lou was reading my mind...

VWJet:

 

The tech rep at the Rev it up event said that one of the aftermarket guys (Racingbeat?) tried playing with intake mods (not FI) with no success. It sounds like the stock intake is pretty optimized across the board.

 

It's not an issue with the fact that it's a rotary. It's got to do with the way that the intake system in the RX8 is setup. The multiple intake paths, which are opened at different rpm speeds, could also be employed in a piston engine.

The reason why a standard CAI (tube and cone) won't work is because you eliminate all of the benefits of the multiple paths. It would be like removing a Honda's VTech, and replacing it with a single cam that is between the two VTech cams. One of the intake paths does already incorporate a "cold air inlet". And if someone can relocate the others without affecting the tuning, then there should be some benefit. But getting it just right will take alot of trial and error, and I don't see too many aftermarket companies doing that, because that extra R&D would probably price it out of the market.

---jps

 

Correct me if I'm wrong, but all of multiple paths for airflow are within the intake manifold. I don't think anyone is talking about replacing the mani... just replacing the stock intake tube and the stock restrictive airbox and filter. Get a higher flowing filter and lower intake temp and I can't imagine why you wouldn't see gains in power.

 

It sounds like the stock is pretty optimized, so that it would not really change anything.

 

if a after market intake would make 2 to 5hp more don't you think mazda would it done it . if you think about it is all a head game when it come to intake they make more noise and also for looks thats about it.

 

Mazda is to worried about reliabilty and emmission regs to push for any more power right now. I'm sure they got some more tricks up thier sleave. Its a dynamic market someone will find a way to improve on Mazda's work. It just might take awhile. I'll be waiting.

 

if there was any significant amount of power tied up in the intake, don't you think it would make a WHOLE LOT of sense to go ahead and make sure they get all that they can based on the capability of the rest of the system??? if there are weaknesses in the rest of the system, gross improvement through the whole system would maybe then warrant some "improvement" (read: more biased to top end comprimise) in the intake system.

yes, the RENESIS isn't at its highest and most fuel-consuming level of tune, but it has little to do with reliability. emissions may be a reason, but the largest is fuel consumption: what consumer really ACTUALLY cares about the emissions level of their car, unless (as in Europe) they have insurance insentives to get a car that has lower emissions?? rate of fuel consumption is a far more important issue to most consumers, second to power.

...in regard to the "performance aftermarket" industry: the people that work at these places aren't even close to the cream, as the top of the top all go to work for the factories, designing miracles like the RENESIS, not "designing" the shape of a tube (dictated by the existing architecture of an engine) and throwing a cone on it.

[/rant]

to really make significant improvements in the HIpower engine, you're gonna have to get that sucker apart, as by 9k rpm, the ports are already starting to choke the engine down, not to mention if you really wanted to make serious power, you'd have to get the revs UP... like another 1k or so: then you'd really have a beast.

...sorry racer... ... don't mean to go picking on people.

 

The multiple paths of the intake system go beyond the manifold.

---jps

 

I think the aftermarket will design something other than the intake system to boost the performance of the rx8. I remember when SCC tested the 350z and tryed to build a custom titanium exhaust...they lost hp...but after much r&d ... japanese tuners and other rotoary experts will come up with something.

 

I think a proper CAI can make more rwhp, but at the expense of more sound (which is a good thing with some people). There are usually 2 resonators on the intake (maybe more with the RX8). One for sound, and one for back pressure (caused by port closure). The harmonic resonator (1st res.) causes a restriction. Some power can be made here. Intake length reduction will also add power (as long as you’re not pulling in hot air). But the key to keeping the low end power and adding to the high end power, is keeping the 2nd resonator. Most of today's aftermarket intakes take advantage of shortening the intake track and removing the harmonic res. but remove the 2nd resonator. That's why allot of aftermarket kits will gain high end power at the expense of low end. I proved this with my Jackson racing CAI (for a Miata) mounted on a 88 RX-7 with the 2nd resonator plumbing still attached. I gained back the 5rwhp between 2500-3800rpm I lost when I put the entire kit on originally. This also worked on my Miata. (this same kind of back pressure is caused by valve closure).

Although, I firmly believe that the best "power adder" for the RX-8, other than a turbo or SC, will be a programmable ecu. It will be able to optimize the port opening, fuel map, inj %, rev limit, etc. Hopefully something like a LiNk or Haltech, that allows the user to change settings with a laptop or a onboard control pad.

 

can you explain or direct me to a website that explains the theory behind intake resonance, and how resonators actually do what they do?

 

exhaust resonators I know dampen the sound and air flow of exhaust fumes. however I have never heard the term "resonators" referring to a chamber or area that pertains to the intake system... maybe its different for rotary

 

first, yes there are such things as intake resonators, and secondly, the wankel motor isn't an entire universe of difference: outside of the box, it's all the same.

anyhoo, the intake resonators just keep the intake noise down (at least they do on Ford Escorts... *sigh* if you must know i kinda started with that particular motor as one to learn about tuning on)...

exhaust resonators are your basic baffle-type muffler (same deal). intake resonators are (yes) a muffler for the front half, as far as i know (i could be very wrong, never really looked into it, as they're pretty damned useless).

 

The second resonator is right before the intake manifold. It's an external (sometimes part of the intake piping) plastic box with a pipe leading to it from the intake track on most cars. I know the Escort GT has one- here's a pic.

 

Here is my current setup on my Miata. Intake plumbing was reduced by 3 feet, intake "rams" cool air (which I believe the RX-8 already applies) and I modified the stock intake track to keep the 2nd resonator.

 

Oops, sorry for the poor text in the image. This should be better

 

On the RX-8, the variable intake duct is BEFORE the air cleaner (it's a two-headed snorkel, one is a curved primary with a straight in secondary where the duct opens at 7250 RPM), so unless the aftermarket integrates this into their product, they would basically be screwing with the volume and velocity of air going into the intake manifold throughout the RPM range. The aftermarket piece would likely not be worth the cost of R&D given these considerations and the likely negative affect on performance.

Looks like a K&N panel filter will be the only cost effective intake mod for the RENESIS.