Ren-gen

I really don't think the stock setup will have maximum efficiency due to the explanation above (sound muffling). I do think, the only way to make decent numbers is by doing both intake, and exhaust. I think with an intake, exhaust, and ecu, the RX-8 will be close to 300hp (crank). I'll probably do some dyno runs with mine once I break her in. That might not be very soon....I'm looking at buying a 2005.

Sputnik

Shyeah, right...

---jps

lefuton

i think i'm with sputnik on this one. 53hp is a 21% gain...that's uh...quite a bit for just intake and exhaust...what an ecu would do i don't know power already drops off at 9k rpm would going to 11k help?

Ren-gen

I'm talking about a total replacement ECU not a piggyback. My Miata with intake, exhaust, cat, muffler, and Link ECU has 155hp crank from the stock 115hp. It's not impossible at all. I think there could be even more, with the RX-8, because of the multiport intake. Remember, these are "crank" numbers not rwhp. With a good ecu you can program the injector cycles, fuel maps, ignition, inj. %, rev limit. I don't see it being impossible at all.

Lefuton: do you have a dyno plot of the RX-8? Or a Japan website with one? I haven't seen one yet. The one in the FAQ just represents the crank power and just gives a general look on it's powerband. I think there is a good chance the hp can keep building with a higher rev limit. If the curve starts to dip @ 9K, that just proves my point that there's a restriction and the factory unit can be improved.

wakeech

but what we're saying is that the RX-8's hardware is already pretty optimized for the tune of the engine. the variable-length runner system on the intake side isn't holding back power, it's already optimized for upper rpm power, but can run the air 'round the long way for better low-rpm performance too.

"it's" not impossible, but you're making assumptions which i know are wrong; the thought that the RENESIS, with another 50 potential horsepower locked up in it, somehow choked down on both sides is fairly proposterous... i'm not trying to be an ***, but that power just isnt' there with this level of tune: it's not a Civic engine, there just isn't that much to free up with "bolt on"s...
to get the entire system up to spec to make 290hp, you're gonna need as much work on the engine itself as the ancillary stuff around it (ecu, intake system, exhaust).

the dynograph in the FAQ isn't an estimation, that's what the torque curve is like.

chance has nothing to do with power, it's all about the real specifications of the system: it's quantifiable, presice, and real.
the problem with your higher rev theory, which i've been building up to, is that you won't continue to see more power gains, even with "bolt on"s which are tuned perfectly to run those higher rpms, because of (arguably) the most important internal feature in an engine: the ports. the ports on the RENESIS have been tuned to make good flow at all operating rpm, which means that they're not going to do so well at 11k... in fact, Buger thought (at least at one time) that the ports might be the biggest restriction in the system at 9k, the biggest reason there is the beginning of the drop in the torque.
the first thing that need "less restriction" are the ports in the engine... with some nastay bridges, a 11k redline could be usable...

but to make 300 hp at 10.5k rpm, you're gonna have to generate 150ft/lbs, which is like 95% of peak torque... not impossible, as you say, but that's quite a feat, no matter who you ask.

Sputnik

Shyeah, right.

---jps

Ren-gen

Yes, I'm sure that Mazda made the RX-8 optimized for maximum hp based on emissions and everyday driving conditions. But they certainly DID not get Max hp out of this engine. There is NO way they can with today's emission regulations. Yes, this is just speculation but I do believe after working on several V8's, Vtec's, I4's, there is hp to be had. The variable intake works like VTEC (except no cams) so with the ECU, you would be able to program them to open @ different rpm's. So yes, it may have allot of gain with bolt on's like Civics. You would probably have to buy some dyno time but I don't think I'm "preposterous" in saying the RX-8 can attain an extra 50hp from intake, exhaust, and ecu.

P.s- If the dyno plot in the FAQ in correct the RX-8 has absolutely NO DRIVE TRAIN LOSS...wow, the Mazda engineers were better than I thought.

babylou

Ren-gen:

The Renesis induction system is not at all like Hondas V-Tec. V-Tec varies valve lift, duration and induction timing each time a cylinder aspirates. The newer IV-Tec also continuosly varies valve opening relative to the induction stroke. The Renesis does not vary duration or timing. I will agree that the auxiliary port can be considered an analog to variable lift.

Another point I want to make is induction tuning will have no effect on emmissions. Zero, zip, nada! In addition, induction tuning will have a miniscule effect upon fuel efficiency (pumping losses). This is simple ICE engineering. So Mazda did not make some sort of compromise between emmissions and performance or fuel efficiency and performance on the induction system.

So to sum up I say yes it is "preposterous" to believe that 50 hp can be had from simple induction, exhaust and ECU mods. Please understand, we all wish it were possible and would all do it if so but it just ain't so.

neit_jnf

Well, I think that instead of a 3-path variable length intake we could have a continuously variable length intake system something like the one on the R26B?

Ren-gen

Actually, intake induction has everything to do with emissions (at least on OBD II). The AFM is responsible for telling the computer how much fuel to feed the motor, to give a good a/f ratio for the current rpm. The computer gives this mixture a tolerance...if this tolerance is broken, (readings via the two o2 sensors) your engine will lean out its mixture to meet the computer specs for emission purposes. That's why it's very rare to see any gas mileage loss in induction tuning. This is typical for Mazda ecu's (they are not very learnable). With a programmable ecu, you would be "allowed" to get the extra fuel and air into the engine.

The new "Jet air" system the RX-8 posses, also has me wondering why Mazda didn't go with direct injection. Why would they engineer an air pump to air push fuel through the ports when direct injection would do the same thing but with better efficiency (mpg, hp, emissions) and fewer parts to boot.

This argument can go on for ever until someone starts tinkering with their new RX-8 which I doubt will happen for awhile. And until then, I'm still standing ground on my 30rwhp from bolt ons.

babylou

Dude, you are simply mistaken and in more than one area. The freaking AFM (likely a hot wire anemometer) is gonna stay if AEM or whoever does their cone filter on a tube setup or if someone made some sort of continuosly variable induction system. The AFM is part of the ECU system and will not go out of its zone of authority from some simple induction modifications.

Also, the ECU does not "allow" extra air into the engine. The engine draws in the air based on throttle position and the AFM senses the mass of air drawn in. The AFM then signals the ECU as to the mass of air inducted and the ECU draws from a map as to how much fuel to inject. During part throttle operation only the ECU will also refer to the first O2 sensor to fine tune the process. The second O2 sensor is only in place to test the effectiveness of the catalytic converter.

OBD2 has nothing to do with any of the crap you are spouting. OBD1 systems respond exactly the same as OBD2. The second O2 sensor is part of the OB2 setup but as previously stated has nothing to do with engine control.

What do you mean you stand by your 30 hp. Wasn't it 50 hp?

Ren-gen

Obviously my posts aren't getting read by some people. I'm NOT stating the RX-8 can make 50Rear Wheel HP!!!!!!! 50 CRANK...yes....not 50rwhp.

The AFM is controlled by the factory ECU....if this factory ECU is "R-E-P-L-A-C-E-D" by an aftermarket unit (example: Haltech, Link, AEM), the AFM runs on the new code....YOU ARE IN CONTROL. Fuel maps, rev limit, etc etc. As far as letting in more air, you are right. I meant increased air from stock. The ECU has fuel map tolerances....if there is extra air beyond this tolerance, the fuel will not be factored in. Now whether an aftermarket intake will go beyond that tolerance, that's doubtful, but a Supercharger would definately cause this.

OBD I systems acted very differently from OBD II. OBD I's have a physical flapper AFM door which obstructs the intake. OBD II runs on the hot wire. OBD I has a 1 wire O2 sensor which isn't as accurate as today's OBD II 4 wire. OBD I's have only one o2 as opposed to OBD II's two. And yes the 2nd o2 have everything to do with how the engine runs. It doesn't just test if the CAT is working.

I'm not going to get in a pissing contest over this. I'm just stating there is extra hp there, emissions and noise aside.

Sputnik

Either you're backpedaling, or you have a unique calculation for drivetrain loss.

---jps

babylou

You say we do not read your earlier posts but you seem to change focus quite quickly. Pissing away:

Now you are saying that the OEM equipment is not good enough for a blower. What happened to just changing the intake, exhaust and ECU?

There are tons of OBD1 cars that came equipped with hot wire anemometer air flow meters. Aren't 94-95 1.8L Miata's equipped with a hot wire AFM and are OBD1? There are tons of other cars that have bben equipped with hot wire AFM for 15 years.

The ECU does not "control" any AFM. As previously stated, the AFM simply measures the mass of air entering the engine and relays this measurement to the ECU.

Do you know what all of those extra wires on the O2 sensor are for? I thought so.

And you are freaking wrong the second O2 sensor crap too but I am simply too bored to deal with this one.

Goose

easy guys,

I am pretty sure there should be some improvements possible by modifying the air/fuel mixture. Now this could either be because of an improved (if possible) intake, or to the detriment of the emmissions. With the restrictions of the emmission laws over here and programming for premium fuel i'd say these should be very noticeable on the high power model.

BTW who manufactures the ECU's for the RX-8? I am hoping for a few extra ponies myself (low power ). Judging by your low power power, and our emission laws i'd have thought 500rwhp should be easily possible. I will then bide my time until I get it supercharged to power levels more befitting a £20k 4 seater.


:D

Ren-gen

30 hp is typical drivetrain loss for the Miata. Since the RX-8 has a similar setup, (PPF, transmission) but with a bigger clutch and beefy rims I'm guessing it would be more....only the dyno will tell the truth. Mazda's hp claims have been proven to be a bit dramatic at times (2002 Miata...155hp), but Mazda corrected this later in the year. With 30 hp drivetrain loss, yes I would be backpedaling because that would be only 280hp crank. (220rwhp + 30 rwhp +30hp crank loss).... I'm sorry.

Babylou: yes 94-95 had hot wire afm's on the OBD I system....I stand corrected. The OBDI and OBD II do have there differences though.

As for the control of the AFM....The aftermarket ECU uses this to gather the info for the mixtures that is controllable by you (not the voltage signal coming from the AFM, but the fuel itself through the fuel map.) Richer mixtures would have better hp numbers...simple fact. (at the cost of mpg, and emissions). This is only 1 factor too. There’s still rev limit (which may or may not give more hp based on port size), inj cycle, inj %, ignition zones, TPS, EGR control (turning the EGR off, to allow WB02 sensor tuning)

The 2 extra wires on the 02 sensor are for heating (one power, one ground). This allows them to get up to operating temp. quicker to allow the ECU to receive accurate readings sooner during cold start.

If you think the 2nd o2 sensor is just to make your engine light go on when your cats not functioning, you’re wrong. Try and straight pipe an OBD II and you'll know what I mean. (KA-chunk!)

bureau13

Does anyone know what the differences are between the engine in the RX-Evolv concept and that in the RX-8? The Evolv supposedly put out 280 bhp. Now, I realize it wasn't a production car, but I thought it was a drivable test platform. My point is they must have made some compromises to get from 280 down to 250...maybe they can be unmade in the aftermarket?

jds

babylou

The Evolv engine was a fantasy engine with a fantasy hp number. How many show cars that enter production actually match the quoted power at the show? About none.

bureau13

It was not a fantasy engine, it was a real engine that underwent extensive testing, not just in the Evolv but well before that. The reasons why production engines don't generally make the same numbers as the concept predecessors is because production cars need to be concerned with things like emissions, noise, fuel economy, drivability by "normal people," etc. The point being that people who make aftermarket modifications to their cars in the quest for more power are not usually "normal people" that care about many of those other factors...they just want more power.

jds

FritzMan

After looking closely at the Cdn RX-8 brochure, I've noticed a couple of things. The muffler is longitudally mounted with exhaust pipes exiting from each side. Nice for packaging and the apparently compulsary dual exhaust (=sporty) look, but nowhere near as efficient as a couple (why not just one?) straight-through cannister mufflers. Also, the log-style manifold and pre-cat seem to be integrated into one unit. Switching to individual runners (and bypassing the precat) would surely make more power. While I don't encourage cat removal, I don't care about precats so much because they are primarily useful for just the first couple of minutes of engine operation until the main cat is warmed up. Kind of ironic how our society feels that having lower emissions on start up justifies the measurable decreased fuel efficiency from it's equipment, what causes more harm in the long run?

Rotaries like to breath (don't know if it's more or less with the new side ports though). My guess is that 25-30 crank HP (with a main cat) can be found simply through uncorking the exhaust.

babylou

That's why I say it is a fantasy engine. The specs were for an engine that was not production feasible. GM could just as easily put a 700 hp SB engine in a show car. Of course this engine would never pass emmissions, etc.

bureau13

I thought we were talkinga bout power potential in the aftermarket? I could care less about noise (to a point), startup emissions, etc, so that lost power is available to me through the aftermarket. I thought the whole point of the discussion was whether or not that power was available to be tapped. I don't care if Mazda taps it or GReddy, as long as it is available to *me*.

Sorry if I misconstrued the original point.

jds

JerryLH3

Anyone who has ever worked on previous generations of rotary engines knows there is a good bit of power to be had by exhaust mods alone. You could keep the main cat, too, or switch to a "hi-flow" cat. Someone will eventually come out with a collected header to keep exhaust pulses separate longer (here comes the argument about exhaust scavenging - I swear I'm not a trouble maker :D ).

Intake mods may not be as useful, sometimes they never are.

rotarygod

Here's why the factory airbox works like it does:

http://www.rx8forum.com/showthread.php?s=&threadid=5710

It is under the general discussion forum.

SPDFRK

I went looking somewhere other than this forum while I was online (weird) and found this...

http://www.racingfashion.com/mazda_rx8_parts.htm

They need an RX-8 in the LA area to use as a guinea pig for their intake. Figured somebody might want to take advantage of this and maybe have a little input to the process.