As we all know the 4 port Renesis engine as found in the auto transmission cars is the lower power version. I've seen many people inquire as to how power can be gained on these cars to bring them up to par with the 6 port engines and I am sad to say that the cars are stacked against you and you're almost out of chips. There are several reasons why this engine just isn't going to give you any more serious power. The good news is that you can change this with forced induction! You just can't get much more out of it unless you do.

There are some very technical topics that need to be dealt with that will fully expose the potential or lack thereof of this version of the Renesis. They are:

1: Port timing
A: Primary port size
B: Secondary port size
C: Exhaust port differences
2: Port area
3: Intake runner design
4: Air flow affects of runner area
5: Thoughts on forced induction

Since I as usual will be very long winded again I am seperating this into an outline fashion.

1: Port timing.
Total port timing has much to do with where the engine produces optimal power and how wide the power band is. The greater the total port timing, the higher and narrower the usable power band. Sounds kind of strange. The shorter the port timing, the lower and wider the usable powerband. On a rotary port size is directly related to port timing. Unlike a piston engine, we can not just install a larger set of valves for greater flow but still retain the same cam profile for the same timing. It just doesn't work that way.

A: Primary port size: The port sizes and therefore port timing of the primary ports is very different. The primary port open timing is the same between each engine at 3 degrees after top dead center. However the closing points are different. The 4 port closes at 60 degrees after bottom dead center whereas the 6 port engines port closes at 65 degrees after bottom dead center. Remember that a shorter opening time is better for a lower power band and is also limited in total power production.

B:Secondary port sizes: The secondaty ports as with the primaries are also timed very differently between both stlyes of engine. The Secondary ports as with the primaries open at the same interval of 12 degrees after top dead center. However once again the port closing intervals is different. The 4 port engine closes at 45 degrees after bottom dead center whereas the 6 port engine closes at 36 degrees after bottom dead center. It would appear that the secondary ports have the advantage on the 4 port engine. Maybe they do but the 6 port engine still have 2 more ports to go so the benefit ends at the top of the 4 port engine's powerband that stay open until 80 degrees after bottom dead center. Look at a dyno comparison of the 4 port vs the 6 port engine and see where the 6 port engine starts to make more power than the 4 port engine. Then look at where the 2 additional ports open up on the 6 port engine. Coincedence? I think not! Remember that the 4 port engine is tuned for greater average power down low than the 6 port engine and this timing scenario alone is a big contributor. The old 4 port engines has secondary ports that stayed open as late as 60 degrees. By default the older engines are more suited to better top end than the current engine bases on port timing.

C: Exhaust port differences: The exhaust ports aren't even timed the same between these 2 engines. They both close the same time at 3 degrees before top dead center. The opening point is a little different though. The 4 port engine opens at 40 degrees before bottom dead center and the 6 port engine opens at 50 degrees before bottom dead center. Again shallower timing and a later opening are better for low end power. Another strike against the 4 port in the power department. Remember that a port with less timing is also a port with less area and therefore flow which takes us to the next section.

2: Port area: By now you have seen that the total port area is less on the 4 port engine than it is on the 6 port engines. This also applies to the intake runners. The total port area on the 4 port Renesis is even much less than the old 4 port 13B engines. This smaller area helps to keep the incoming air velocity high. However we come to a point where too much velocity is harmful. We'll call this the Z factor. After air hits .6 mach or 60% or the speed of sound in the intake system, it begins to lose useful energy. I actually have a chart somewhere that shows this. Once the velocity exceeds this speed, no more or at least very little more power can be achieved. What will happen is that the air begins to heat up dramatically. Hotter air molecules are bigger air molecules. bigger molecules take up more area per volume and suddenly that pipe appears much smaller. Once you get to a certain rpm, you've hit an airflow brick wall. There is no point in trying to rev these engines higher to achieve more power. You had better be ready to increase total port area, total intake runner area, and decrease total intake runner length. The 4 port engine has a lower redline for many reasons but the fact that it can't inhale enough air due to velocity reasons for a higher redline should be reason enough to understand why it is where it is.

3: Intake runner design: As we all know an intake manifold can make or break an engine in the power department. The runners should be relatively straight with a minimum number of bends. A good manifold will have gentle bends where necessary and not conduct any excess heat. Luckily the Renesis intake manifold is the single best intake manifold that Mazda has ever designed. There are very many reasons why it shouldn't be changed. Upon first glance it appears that the only difference between the 4 port and 6 port Renesis manifolds is the fact that one adds 2 more runners. Oh how wrong could that statement be! Each manifold was designed specifically for that particular engine and it's powerband. Each manifold has a valve known a VDI which stands for Variable Dynamic Intake. The VDI valve opens at 7250 rpm on the 6 port engine and lower on the 4 port engine to bridge different runners together. This in essence lets the engine see a shorter runner than is what is actually there. We basically have 2 different runner lengths. Each set of runners is tuned to a certain rpm and by changing this the powerband is widened. So we not only have variable timing but also a variable length manifold as well. V-tech eat your heart out! The intake runner lengths between engines are as follows. I'll classify them into long and short to signify when the VDI valve is open and closed. Closed is long open is short.

4 port engine
primary runners long: 27.4"
primary runners short: 14.8"
secondary runners long: 29.1"
secondary runners short: 16.5"

6 port engine
primary runners long: 19.8"
primary runners short: 13.5"
secondary runners long: 20.4"
secondary runners short: 14.2"
auxillary runners: 17.3"

The auxillary runners on the 6 port engine are not tied into the VDI system on the manifold since they split off earlier in the manifold. Since they are only open for a short time they are tuned around this event. As you can see even the runner lengths are different between the 4 port and the 6 port engines. Longer runners promote better low end. Note that the primary and secondary runners for each rotor are siamesed together until after the VDI valve. The above lengths do not take into account for this but rather are measured to the point where the manifold splits between front and rear rotors. Since each runner can receive a tuning benefit from both primary and secondary ports due to the VDI valve also being siamesed, the VDI effect is over a broader range than it was on the later 2nd generation RX-7 where VDI first appeared.

Another good feature of this manifold over previous manifolds is the use of composites for the upper half. Composites unlike aluminum dissipate heat very well. Aluminum is a great radiator of heat and will just grab it and hold it. This heats up the intake air. This isn't a problem when the engine is revved up as the airflow through the runners serves to cool down the manifold but the problem is greatest when the car is idling. While a total composite manifold would be best in regards to heat, at least half of it is. My only concern is how much psi will it hold should forced induction be applied.

4: Air flow effects of runner area: As I have previously stated we have a phenomenom known as the Z factor to worry about. How to optimize this though can yield some fantastic results and in this respect Mazda has done some homework. When only 2 runners are receiving air, the velocity through them is higher than if 4 were receiving air. Duh! This will yield superior power right up to the point that the Z factor hits .6 mach or so. This is a good rpm to open up another set of runners. Guess what? The Renesis does this! At a higher rpm another set opens up and power stays high all the way through the powerband. Brilliant! Too bad they screwed up with the ecu tuning. The 4 port engine runs into a very bad problem. It runs out of runner area. Basically it has the runner area of a 6 port engine minus the auxillary ports. That is alot less airflow potential. It doesn't matter if we make a shorter intake manifold that tunes to a higher rpm, we are still flow limited.

5: Thoughts on forced induction: Please understand that this next paragraph is using the 6 port engine as a baseline for potential so don't get too discouraged. Typically in the past the 4 port engines were thought to be the better choice in the forced induction arena. However the 4 port engines of the past also had greater runner area that was nearly equal to the 6 port runner area, they outflowed the 6 port engines on the flowbench, and they were simpler. All of this has changed with the new 4 port Renesis. The secondary ports are no where near as big as the older engines. The timing is not near as great. The total runner area is much less. This all adds up to an engine with less airflow. How does a turbo spool up? Airflow! If we were to add a turbo to the 4 port Renesis, it would be one with a very small exhaust housing that is designed for small gains. A lack of airflow through the engine will make it very slow to spool. A high compression ratio helps to combat this but we can't perform miracles. It would actually spool up faster if all the ports were open simultaneously by diabling the secondary shutter valves. This applies to 4 and 6 port engines. The faster we can get more air into the engine the faster we can get it out and therefore spool up the turbo. Remember that since we are relying on positive manifold pressure we just want all the area we can get so as much air gets in as fast as possible. Based on the fact that there is so much less runner and port area than the previous 4 port and 6 port engines, the new 4 port Renesis is not a good candidate for forced induction as the 6 port engine is. You could still get some very nice power out of it though so don't think it would be bad to use forced induction. You are just ultimately (somewhere over 350 hp or so) going to lose potential as compared to the 6 port engine.

The 4 port Renesis as well as the 6 port were designed to maximize performance in their respective power ranges. Through careful port timng, sizing, and runner lengths, Mazda has just about maximized the performance capabilities of these engine. Their tuning is insufficient though but once this engine is tuned properly, gains will be few and far between. There is always room for a little more power but gone are the days of 35hp gains from and exhaust. The 4 port engine has so much going against it in terms of pure power production that it should not even be considered a viable market for performance products. Gains would be too small to justify the product prices. Remember that a gain lower in the powerband equals less total horsepower than a gain at an engine designed to run at a higher powerband. If you have a mod that can add 10hp at 9000 rpm, it will only add about 4 or 5 at 7000 rpm. Performance gains for the 4 port engines will be much less. Sorry 4 port guys, if you are performance nuts hellbent on getting the most power from an RX-8 that you can, you bought the wrong model. Don't be discouraged though. Forced induction can still give you the speed and power that could still make this car a force to be dealt with by most other cars on the road.

Forgive me for not reading that entire post(data overload lol) but, what about the power potential of the this 4 port if it had a semi PP? I know this would be a serious mod but, think of the power potential. You could use a flapper valve (like the renesis aready uses)in the newly designed 6 port LIM to reduce the overlap a motor PP has to control idle but, the power potential should be phenominal in upper rpm's. What do ya think?

you just ruined my day

Originally posted by mikeb
you just ruined my day

HAHAHAHAH ....... this is your best one liner yet ! HAHAHAHA

Mikeb

No need to despair you are just going to get yourself a manual rx8, if you want to work on your performance.

Great post rotary dog (god in reverse) as u are a HOT DUDE with devilish ROTARY information.

Its always a pleasure all beith a long one to read your posts.

cheers
michael

one question. when did you get a crack at the 4port engine? i saw the pic in the other thread that i think started you on this path, but where did you find the info?


edit: off topic but did you see that thread in genereal auto about that new engine design from australia. the site mentioned that they were using wasted spark.

Originally posted by mikeb
you just ruined my day

short memory you have there mike! canzoomer said this in response to you in november:

I REALLY DOUBT that you could gain that much on the AT.

The AT does not even HAVE the 3rd set of intake runners that the MT has.
The AT makes peak power around 7,000rpm as a result.

On top of that the auto tranny sucks up some of the power.

Lastly, there is a damned fine reason they capped the AT power.
From what I have heard that tranny will break if you fed it much more power.

REALLY. You do NOT want to do this!

If you want a faster RX-8 sell the AT and get an 6MT.

That is the right way.
Without ANY modifications you will get an extra 30hp right off the bat.

Originally posted by zoom44
one question. when did you get a crack at the 4port engine? i saw the pic in the other thread that i think started you on this path, but where did you find the info?


I've had the info on timing and runner lengths for a while but was unsure as to the timing numbers. Based on past 4 port engines these made no sense. I also went to a dealership and stared at the intake manifold of an automatic car. The secondary runners visually appeared much smaller. Once I saw the internal picture of the 4 port in the other thread it all made sense and confirmed the suspicions I have had. The published timing figures can be found within the Mazda Renesis online training program that was floating around here somewhere. It wasn't actually part of the presentation but was rather a PDF file within the program. The intake runner lengths come from the RX-8 book by Jack Yamaguchi that many RX-8 owners have.

As far as the semi peripheral port goes, that goes well beyond the scope of bolt on performance. If someone is willing to go this far, they would probably be willing to adapt an entirely different engine to suit their needs also. I didn't get into porting at all but I'm sure there are some gains to be had from porting. The 4 port engines can't be ported out anywhere near what even the old 4 ports had stock. Even if the engines were ported, the auto would lose some of its powerband for the benefit of gaining more top end. A new torque converter would have to be figured into the package. If a semi peripheral port were used, I would use them instead of another set of ports not in addition to. Too much airflow is a decrease in velocity and only good for extreme rpms. We don't need any more. I would be more inclined to use only the side primary ports with a set of secondary peripheral ports and that is all. No outer side ports what so ever.

The 6 port engine would be the best porting candidate. The primary ports can't be opened any earlier or else the corner seals will fall into the intake runner. Their closing can only be adjusted. The secondary ports could be modified to open at the same interval as the primary ports but this is only 9 degrees earlier. The secondary ports on the 6 port engine can't be closed later since the closing side is the top and this is where the auxillary ports are. The auxillary ports could be closed a little later but with the rotating sleeve installed there isn't a whole lot of benefit to going any later. The sleeve will be the limiting factor in determining how high. Basically the most benefit will be from smoothing out the transition from runner to port opening. The exhausts are probably where the biggest benefit will be from as far as porting goes. They have thick steel inserts that really disrupt the airflow leaving the port. Their inner radius needs to be backcut for airflow reasons. These ports can probably be opened and closed a little later. There is only 6 degrees of dwell (non port overlap) on this engine so closing them later may actually get rid of this situation. They can't go very far though due to fears of a corner seal falling in. The past 6 port engines had small but noticable porting gains. I think the Renesis will have even less. I don't think streetable porting on this engine will yield an impressive gain. I bridge type of porting may hold some merit though.

Originally posted by zoom44
short memory you have there mike! canzoomer said this in response to you in november:

I REALLY DOUBT that you could gain that much on the AT.

The AT does not even HAVE the 3rd set of intake runners that the MT has.
The AT makes peak power around 7,000rpm as a result.

On top of that the auto tranny sucks up some of the power.

Lastly, there is a damned fine reason they capped the AT power.
From what I have heard that tranny will break if you fed it much more power.

REALLY. You do NOT want to do this!

If you want a faster RX-8 sell the AT and get an 6MT.

That is the right way.
Without ANY modifications you will get an extra 30hp right off the bat.


I was in denial back then

Originally posted by rotarygod

As far as the semi peripheral port goes, that goes well beyond the scope of bolt on performance. If someone is willing to go this far, they would probably be willing to adapt an entirely different engine to suit their needs also. I didn't get into porting at all but I'm sure there are some gains to be had from porting. The 4 port engines can't be ported out anywhere near what even the old 4 ports had stock. Even if the engines were ported, the auto would lose some of its powerband for the benefit of gaining more top end. A new torque converter would have to be figured into the package. If a semi peripheral port were used, I would use them instead of another set of ports not in addition to. Too much airflow is a decrease in velocity and only good for extreme rpms. We don't need any more. I would be more inclined to use only the side primary ports with a set of secondary peripheral ports and that is all. No outer side ports what so ever.




Well that semi PP idea was really meant for potential an aftermarket engine upgrade for other rotary powered vehicles. I should have specified before. My bad! I already understand that it would take a ton of work just to make something like this work for the auto Rx8 but this type of engine in some kind of Mazda racing car would be awesome. Anyways I still feel that if provides a really good "foundation" to be a powerfull power plant "if" put in the right hands.

man i didnt read anyones post, all to long sorry.lol

Rotary, what was the lengths of the s5 Rx-7 intake runners? CJ

I never measured the lengths of that manifold. I even had one for a while. I only know the S4 n/a lengths. I do know though that when VDI is actuated on the S5 manifold that the effective length is shorter than the S4 and hence more top end power.

So I guess thismeans that the auto Rx8 has the same mod capability as those toned V6 versions of the muscle cars had like the V6 Firebird V6 Camaro and V6 Mustang. All looks and no muscle. Youcouldnt do anything for those "little girl" engines exceptfor intake and exhaust to make them sound like they were fast. They came stock w/200 hp and I dont think anything could bedone to get that number over 207. Well there were always nitrous shots but Idont consider nos to be a "true" mod.

Originally posted by JeRKy 8 Owner
So I guess thismeans that the auto Rx8 has the same mod capability as those toned V6 versions of the muscle cars had like the V6 Firebird V6 Camaro and V6 Mustang. All looks and no muscle. Youcouldnt do anything for those "little girl" engines exceptfor intake and exhaust to make them sound like they were fast. They came stock w/200 hp and I dont think anything could bedone to get that number over 207. Well there were always nitrous shots but Idont consider nos to be a "true" mod.

what about turbo's and supercharges???

that will get me over 207

Yeahthose could but they are pricey they void your warranty and now after readingthis post it looks like the gains wouldnt be so great after all.

ANY1 wanna buy a 2004 AT brilliant black rx8 w/nav

:)

and by the way Mike, he screwed up my day pretty bad too. Back to the dealer i go.

Interesting thread ... and I'm sure rotarygod is accurate in his overall assessment. However, that being said, and I may be wrong, but I believe this new RENESIS NA 4-porter still "spanks" the previous NA factory 4-porters in the power department and does so with much greater EPA burdens to boot. The bulk of the potential has been reached, once you are at the end of the envelope, you're at the the end of the envelope. My uneducated assessment is I have a pretty sophisticated 4-porter that MAZDA has been willing to bring closer to that desireable edge, from the factory. All that means is there is not much room for those that like to tune (witness the intake and exhaust folks struggle), but those of us who are not "tuners" can be content in the knowledge that MAZDA has not cheated us the owners, but rather the tuners it would seem.

what do you think of the potential of = length "headers" to help with shortened exhaust runners, maybe not adding much hp but moving the usable power band down lower. And the possibility of doing a duel throttle body set up with two smaller tb's for each rotary on a shorter manifold which could produce a higher velocity lower volume air source to better match up the air flowing out and not bunch up the air. And adding a higher stall toque converter possibility with a different final drive gear to improve the 60 foot times. And smaller dimeter lighter weight rims and brake rotors to lower the moment of inertia need to turn the wheels also under-drive pulleys. I don't know, I wouldn't put a bullet in the head of the 4 port just yet, I think we need to let these creative after market geniuses play a bit first.

I dont know. I ran with a MT/G35 last week would have had him if not for the light. But then I just got out of a 3G/sporty and into a RX-8/sporty... Yea the RX-8 in: MT or sporty has way more HP then the 3G, so with some mods and a TB or SC you will feel da pow-wa in a sporty 8.
Or so I think.

I will still add a SC when tested and enjoy my 8. Still a wonderful car.

well RG, it sounds to me like you just wanna spite me on this one :P

considering how small the ports are on this motor, it sounds like there's a TON of room to go up and down on this motor to grow and match the 4 port version of this motor, especially knowing that this motor doesn't have that tertiary port, so you can still keep closure timing sane when you turbo this motor.

holes can me made BIGGER (especially when they're small, as you say), but hard to take away ;) the tertiary port is the 6 port motor's biggest knock against it, turbo-wise.

and that 6* of dwell, gotta go.

I remember when i got my cougar and hooked it up. The only regret i ever had about that car was that i didnt get a manual.

I couldnt live with myself if i didnt get the 8 in a manual no matter the traffic or the learning curve.

Wakeech: if the casting thickness is not large enough, how can you make the ports and runners equal in size to the older engines? The key is the casting. If you do this, the intake manifold no longer works and now you need a custom built one. Oh yeah, :P back at ya!!!

There really isn't much point in trying to use shorter intake runners. The intake already changed its effective length to tune for higher rpm's. Depending on how short the new runners are, the intakw will make far less low to midrange power but gain a little on the top end or it will lose ultimate top and bottom end due to incorrect tuning. We are really limited by ultimate flow through those small ports which is why we don't want to raise the redline. A shrter manifold would be useless without a higher redline. The car would have far less average power and would be slower and more lethargic as a streetdriven car.

The exhaust header needs to be treated very different than just large or short runners. You need one length runner for the outer ports and another length runner for the center port. No one is doing this yet which is why I feel that every header on the market is nothing more than an expensive paperweight.

ok, so using a turbo would not help. Now that doesn't rule out forced induction.

Granted the 4 port will never match the 6 port in volume and therefore power... But wouldn't a positive displacement blower increase power significantly?

Sure it would increase power, but some internals would have to be beefed up to withstand the boost, such as apex seals. Probably not worth it on an auto if you ask me.

You can still add a turbo or a supercharger and still get some nice performance. You can turbocharge a lawnmower engine! The 4 port engine will be fine. You just don't have near the potential of the 6 port engine. If you want a nice power increase, go for it. If you want a full on race car, pick another engine.

You would not have to change anything internally to just add forced induction. This is a very common misconception. The fact of the matter is that if you had to upgrade seals just to use boost, they would be inadequate for nonturbo use as well. Internal pressures aren't that high for low to moderate boost. It is when you run outrageously high levels that strength of parts is an issue. Proper tuning will do more for engine longevity than seal materials.

lucky for me I have the 6 port engine... I just feel bad for poor 'ol Mike
;)

^^^ouch

So can we sporty people go with a level-10 on the tranny and get a still get a SC?

Originally posted by rotarygod
Wakeech: the intake manifold no longer works and now you need a custom built one.


well duh, if you're gonna do something, do it right. fabbing and selling trick parts to the peoples is a good way to make a living.

btw, how is this different for the 6 port anyway?? if the IM for the 4 port would be next to useless in a modified motor, how does the 6 port's stand up in a turbo application??

I guess Im just going to have to take my buddy's advice... "If it don't go...chrome it!"

So whois going to bethe first guy onhere to turbo their automatic

hopefully me

I have an auto 8 and am not at all disappointed. I drove both the six and the auto extensivley before buying and most of the difference was probably the lower first gear in the six speed. Absolutely not enough difference to justify shifting gears all the time. If I feel that I need to gearhead there is always the manual mode.
The 6 and the auto weigh very close to the same and by the time you add all that extra crap i.e.(moonroof, leather, etc.) the 6-speed probably weighs more, (which is the way most of the 6-speeds were equipped that I looked at).
The only thing the auto trans might not be able to handle is the 9000r redline. The torque converter would be the weak point. The torque and hp output on the 8 is hardly enough to tear up a tranny.
As for mods for the auto-8, someone just has to develop them.
Be careful where you spend your money.

Just my piece.

Originally posted by zmzmrx8
I have an auto 8 ...
...Be careful where you spend your money.

Just my piece.

Be careful indeed.

I suppose if you can't feel the difference, than you should be happy.

However, I can't help but think that you will be mightily dissapointed were you to to attempt to keep up with the 6-speed RX-8 in your auto RX-8 under any circumstance.

They simply don't compare in any way when pushed.

If you add all of the GT suspension and braking goodies to an auto, you might be able to take the corners as well as the 6-speed, but you will be dusted every time on the exits.

I can't read jap but the top of this page amemiya.co.jp/rx_8/ it looks like they clame 70ps on the auto.
http://www.re-amemiya.co.jp/rx_8/

Originally posted by wakeech
well duh, if you're gonna do something, do it right. fabbing and selling trick parts to the peoples is a good way to make a living.

btw, how is this different for the 6 port anyway?? if the IM for the 4 port would be next to useless in a modified motor, how does the 6 port's stand up in a turbo application??

LOL! The manifold for the 4 port would only be useless if you enlarged the ports and the runners to the point that they were much larger in area. You don't want small manifold runners feeding large engine port runners and ports. If you just did some port work but didn't enlarge the engine runners at all, it would be fine.

Here's the thing about the autos. For you guys that have them and want to turbocharge them, go ahead. The runners are limited in area when compared to the 6 port engines which simply means that you are also limited in max rpm as compared to the 6 port engines. Last I checked you already were. Nothing changes in that respect. You can still easily get the same low to midrange potential as a 6 port engine using forced induction. The tradeoff will be above 7000 rpm where you simply can't go. In reality since you guys will not need the larger turbo of the 6 port engine, you will have the ability to get much greater low to midrange power than the 6 port engines. Combine this with the transmission shift points and this should make you very happy. It will feel like a low end torque monster compared to the 6 port engine. The turbocharged 6 port engine however will feel like a high revving race engine by comparison.

The guys that typically buy the 6 port engines (in the U.S.) do it for the top end and greater overall performance. The people that buy the auto 4 port engines typically buy them for ease of driving around town with the occasional spirited driving. For the 4 port standard owners in other countries, what are you guys thinking? As far as forced induction on the U.S. spec cars, I don't see how both camps wouldn't be very happy with forced induction. Yes they will feel different. Don't they already?

i really wanted a 6 speed but my wife cant drive as stick :(
we had to settle for an automatic. i dont mind it, i just shift it in manual mode so i have more control. it doesnt feel the same though! im using to racing my 5 speed mustang!

In normal driving (1-4k rpm), you can't notice a differance, but when you are above that, you notice. But who drives in the upwards of 6k rpm on a normal driving day anyway?


Troy J.

Originally posted by JeupRX-8
In normal driving (1-4k rpm), you can't notice a differance, but when you are above that, you notice. But who drives in the upwards of 6k rpm on a normal driving day anyway?


I do. All the time.

The real questions is: who drives at 1k RPM ?!?:(

Originally posted by MazdaManiac
who drives at 1k RPM ?!?:(

me, when driving other people's RX-8's :)

i drive at 6k rpm or higher every day. i have also driven it at nearly 1k in traffic. i find my car wont really go along at 1k. more like 1100-1200 @7 or 8 mph in traffic.

At 7 or 8 MPH, you should be in first.

All the fun begins at 6k :D Why would anybody drive at 1 to 4k? :confused:

The faster you can acclerate from 1K to 4K rpm, the faster you can get to 6K rpm.

Originally posted by MazdaManiac
At 7 or 8 MPH, you should be in first.

thats what i'm saying.

oh boy

Very nice write up rotary god kudos. Thats why i have put my auto rx8 for sale :)

It's still not a bad engine. It just has less performance potential. Remember that smaller is better only until you max it out and need more. Mazda did pretty good and only used what they needed.

It's still not a bad engine. It just has less performance potential. Remember that smaller is better only until you max it out and need more. Mazda did pretty good and only used what they needed.
Yah you know i love reading your posts. Your wisdome is infinate, you know everything and i just love how you put everything in perfect detail. You broke this post down into sections lol you should join me at uni and write some good papers for me :) LoL yah i have contacted 4 ppl on used rx8s now im just waiting on their replies :)

Hitmann - so after a year of ownership youve had enough? Fed up w/the lack of power and gas mileage? The stellar cornering just isnt cutting it for you anymore eh?
Sorry to hear that - see I thought I had you pinned as one of the members on here that would definitely end up installing a turbo on his automatic.

By the way - Imnot quite sure why this thread was resurrected from May 04. The information it contains still seems pretty accurate but theres already a member onhere who has installed the turbo on his automatic and has cut his 0-60 down by nearly 2 and a half seconds (8.8 to 6.4). I find that somewhat impressive given all the barriers the automatic has going against it (based on what rotarygod has stated here).

You can always make an engine faster with forced induction. Even the 4 port. How high you can ultimately take it will not be as high as the 6 port engine though. You never know, the point that it can't be made to go any higher may not be until 400 hp or more. It's not saying this can't be a fast engine with some work. It just can't get the ultimate power that a 6 port engine could. In no way do I think the auto owners should be discouraged with their engines. Add forced induction. You can go alot faster. Without forced induction they will have a harder time getting power.

Keep in mind that even the 4 port engine makes more power than the last nonturbo rotary did stock. 197hp RX-8 vs 146hp '86-'88 RX-7 and 160hp 89'-91' RX-7. People have done no more than just throw on the stock turbos from a Turbo II RX-7 onto these nonturbo cars and have gotten 275 rwhp. Remember that the 4 port is starting from a higher number. Getting this low power engine over 300 rwhp shouldn't be an issue with a turbo if you can tune it.

So I guess maybe the thread title should now read, "Why the auto 8 has less potential for power"
:D

That would probably be more appropriate.

RG, mine is a JDM 5sp. So my engine is the same as the auto 8? If I were to go FI, my yields would be that of the auto 8 as well right?

They should be.

What about that sc that claims to have 325 lbs of torque that too has no potential?

What about that sc that claims to have 325 lbs of torque that too has no potential?


I don't think I read even once in this thread that there is "no potential" for improvement, only that said potential is lower in the 4 port engine. In fact, Rotary God has said numerous times in this thread that FI (Super- or Turbocharging) holds great performance potential for both engines. The 6 port engine will have higher relative gains (i.e. a 4 port may gain 15% more power from a given mod whereas the 6 port might gain 20% from that same mod)

Feel free to correct me if I've missinterpretted.

RG, mine is a JDM 5sp. So my engine is the same as the auto 8? If I were to go FI, my yields would be that of the auto 8 as well right?
It's the same engine as a auto one but the ecu tuning is different.

I own an auto rx-8 stock and my 0-60 time is 6.6....

It's the same engine as a auto one but the ecu tuning is different.

that is not true....the 6sp is 6 port and the auto/5sp mt is 4 port...

also the VFAD intake is not on the auto/5sp as there is no need for further aspiration since the engine tops out at 7500rpms

that is the reason why at 7500rpms things start getting loud and furious for the 6sp mt owners

would you like the tech module that goes into detail on the engines and the differentce between the standard power (auto/5sp mt) and high power (6sp) it is very fascinating to learn how complex the renesis engine is

that is not true....the 6sp is 6 port and the auto/5sp mt is 4 port...


That's what he said.

So, is it worth putting money out for $300 intake filter kits really?

not really but I love the way it sounds

Rotary God, You are the most negative person on this site. I rarely see you post anything that doesn't rain on someone elses parade, what gives?

Negative? About what? Is the big problem that I'm raining on someone else's parade alot, or that they had higher expectations than what is realistic and they just found out? I try to tell people what they need to hear, not what they want to hear. That's usually the opposite of alot of false advertising. That's what my negative side is generally aimed at. People do have the right to not agree with me if they choose not to. It won't hurt my feelings.

Rotary God, You are the most negative person on this site. I rarely see you post anything that doesn't rain on someone elses parade, what gives?


Learn to respect the knowlege of God ;) , when he speaks we all listen .

cheers
michael

Learn to respect the knowlege of God ;) , when he speaks we all listen .

cheers
michael

except about politics ;)

cheers
jason :D

Perhaps that is the case, just seems to me you're always unneccesarily knocking a lot of things.

You're right, rotarygod when you say "the AT RX-8 engine has less power potential than the 6MT" , i mean just the gearbox alone could make everyone agree to the fact... but... " the Auto RX-8 has little potential for power" is debatable. RE Amemiya beefed up an auto RX8 to 256whp/325 lb-ft. Greddy's working on the turbo version as well which should at least match those figures or even exceed them.

But DAMN, wouldn't it be nice if us auto 8 owners have a 6-speed gearbox instead of 4?

Im still very hopeful

You're right, rotarygod when you say "the AT RX-8 engine has less power potential than the 6MT" , i mean just the gearbox alone could make everyone agree to the fact... but... " the Auto RX-8 has little potential for power" is debatable.


That's why I went back to rename the thread since I felt it was a little misleading to begin with. Unfortunately when you go back in to edit a thread to change the name, you only change it in the first post. The overall thread title does not get altered. The system wouldn't let me do it.

EDIT: Wait a minute. I'm a moderator. I CAN change it!!! Thread title is now more appropriate.

That's why I went back to rename the thread since I felt it was a little misleading to begin with. Unfortunately when you go back in to edit a thread to change the name, you only change it in the first post. The overall thread title does not get altered. The system wouldn't let me do it.

EDIT: Wait a minute. I'm a moderator. I CAN change it!!! Thread title is now more appropriate.

You are a moderator? :p g-d help us all...oh wait you can't have those goofy little sayings under you screename anymore can you....ok I don't mind your new status now :p :D

But DAMN, wouldn't it be nice if us auto 8 owners have a 6-speed gearbox instead of 4?


The new 6-speed auto in the MX-5 will be finding it's way to the RX-8 probably next year.

WONDER IF IT WILL BE POSSIBLE TO TRANSPLANT THE 6SPEED AUTO BOX FOUND IN THE UPCOMING MX5 TO THE 4 SPEED RX8 AUTOS ;) Dindnt mean to yell oops :p

Thinking of maybe buying a cheap used 4 speed Auto for the wife and putting in the new 6 speed Auto if possible :) , as i believe the 4 speed Autos will losse value as soon as the 6 speed Auto is released .

cheers
michael

You are a moderator? :p g-d help us all...oh wait you can't have those goofy little sayings under you screename anymore can you....ok I don't mind your new status now :p :D

Oh yeah? Actually your signature only appears in the first post when you start a new thread. You have to insert it for any other posts. Kind of like this...

WONDER IF IT WILL BE POSSIBLE TO TRANSPLANT THE 6SPEED AUTO BOX FOUND IN THE UPCOMING MX5 TO THE 4 SPEED RX8 AUTOS ;)
I would love to see that done. If it had paddle shifters that are more like the Ferrari's it would be very fun.

The '89-'91 nonturbo RX-7's and the 1st generation Miata's shared the same transmission with only very minor differences. Even the manual RX-8 transmission is nothing more than the Mazdaspeed Miata transmission with minor changes. I don't see why it would be too hard to install the 6 speed auto into an RX-8. They are good at using the same parts over and over again.

I own an auto rx-8 stock and my 0-60 time is 6.6....
Oh Yeah! Mine is 6.5...
(Not really... :) )
I'd like to see 6.6 with an AT!

Rotarygod

The replacement / alteration of the paddle shifters might constitute a bigger problem than the actuall 6 speed gearbox replacement , i will follow this idea closely and see were it leads .

Could 2 extra gears be added to the existing 4 speed gearbox ???

The Ford 6 speed Automatic gearbox coming out i think is the same as the New MX5'S , MAYBE SLIGHTLY reinforced to handle extra torque.

cheers
michael

Oh yeah? Actually your signature only appears in the first post when you start a new thread. You have to insert it for any other posts. Kind of like this...

I am aware ;) :p

Rotarygod

The replacement / alteration of the paddle shifters might constitute a bigger problem than the actuall 6 speed gearbox replacement
I didn't say it would be easy or would ever happen. It doesn't mean I can't dream though!

Rotarygod

The replacement / alteration of the paddle shifters might constitute a bigger problem than the actuall 6 speed gearbox replacement , i will follow this idea closely and see were it leads .



The gearbox is easy ... it's the supporting logic that needs to be developed. The ECU is programmed with shift points and torque management and numerous other parameters that would need to be updated to support that engine/transmission combo. The paddles just send a signal ... i.e we are in 3rd, just got an upshift signal from the left paddle, shift to 4th. Of course, it needs to know what to do when there are 2 more gears to play with.

The engine also briefly drops torque before an upshift to smooth out the shift, that would all need to be programed. I'm thinking that a retrofit will not be so easy.

The new 6-speed auto in the MX-5 will be finding it's way to the RX-8 probably next year.

Let us pray to the rotarygods at Mazda bless us with that - Amen! :rolleyes:

But then... we're gonna have to sell our 8s to get the new one! :mad:

Well, unless mods can be done to add 2 more gears like you guys said. :p

I KNOW! I'll buy the new Miata and then switch the gearbox with my 8! :D

Expo dredged this up and its a definate good read. Way to much info for my brain to compute right now but does explain alot of what I already thought. Though the last few post's about a tranny swap does interest me slightly.

Wow, talk about digging up an old thread.

wtf necromancy

This thread gives me flashbacks. I was still smoking back then. :angel:

Now here is the funny thing about the 4 port and 6 port RX-8 Auto sold in Japan.

The 4 port RX-8 Auto was rated at 210 ps (about 205 HP). And how much more powerful was the 6 port RX-8 Auto?????????????????????????????? OK, I will stop it.

The 6 port RX-8 Auto was rated at 215 ps.... that is just around 5 HP more.

So when it comes to NA, there does not seem to be a big advantage.

The limiting factor appears more to do with the auto transmission not being able to handle the rpms.

Now, I'm no rotarygod. I'm nowhere near his level. But...

I question the advantage of the VFAD and somewhat the auxillary ports.

The VFAD is often replaced by Cold Air Intakes and ram air intakes. With the ram air intake, it appears you are getting slightly higher HP. The standard engine would appear able to compensate, by having a ram air intake. The faster you are going than the more air in. They both have a VDI, so I don't see much difference there.

I think the bottom line is that for major HP gains, you need to go turbo or supercharger with the RX-8 Auto. But, you can still make improvements with ATF cooler, 2nd oil cooler, air intake, etc.... I've had my rev limit cut and go up to 8,000 rpm and nothing has broken so far (have ATF cooler though).

Lastly, I think many people would be fine with 300 HP to 350 HP on the Auto. I don't think there are that many trying to get to above 400 HP or are trying to drag race at a pro level.

The 6 port engine has the advantage of having a higher rpm range than the 4 port. This is true when installed in the manufal transmission cars. The 6 port autos have the same redline. It is this higher redline on the manual cars that gives the engine the need for the more complex porting and intake manifold than the 4 port. VFAD is for noise control and nothing else.

rotarygod, excuse me, but I read that the VFAD was suppose to allow for more air at higher RPM. I think it was at above 5500 RPM. The VFAD has 2 sections. The 1 section is open at lower speeds and the 2nd section is opened at higher speeds. It appears this is suppose to help when the auxillary ports ports open up (on the 6 port) at 6250 rpm. The VFAD is helping let more air in.

The reason that only 1 section is open at lower speeds is also to limit noise, but I believe the VFAD does have a purpose besides noise reduction. Mazda's info. is showing that it is used for increased air flow at higher RPMs and speed.

The purpose of the VFAD appears to overlap with that of a ram air intake. That is why I believe people are able to achieve some additional HP gains, beside the air being a little bit colder by being taken in from outside the engine bay. Example replacement intakes that use this concept is the racing beat ram air intake or the odula ram air intake.. The ram intake by itself is suppose to add more HP at higher RPM. Unfortunately, the effect of the ram intakes can't be measured on a dyno, because your car needs to be moving through air, and your car is staying still on a dyno when power is being measured. But many people report the effect of increased speed with the ram air intakes and have measured faster 0-60 to 1/4 mile times.

on NA cars, I question how much of an advantage that the auxillary ports are making too. If it was such a big advantage, I would expect the 6 port RX-8 Auto to have a larger HP advantage. In Japan, where the emission laws are different, the difference between the 4 port and 6 port RX-8 Auto is only 5 HP. So it looks like the limiting factor is RPMs on the tranny and having the extra ports is not doing much.

The only way to compare on the street is to take the rev limiters off on a 4 port and 6 port RX-8 Autos, slap a ATF cooler on them with upgraded AT fluid, and see what happens. I'm thinking if you put a ram air intake on the 4 port, that the difference would not be much. In a 0-60 and 1/4 mile race, so many things are happening in a short time scale. So the auxillary ports may need more time to show any effect, time which it does not have in short runs. Furthermore, in a short race, the 4 port and 4 speed would only need to shift once, to 2nd, in a 0-60 and maybe once more in a 1/4 mile. The 6 port and 6 speed Auto, would need to shift more. I think the extra shifting can have a negative time effect or at least introduce the chance of mis-shifting in manual mode. If that is the case, than its a non-issue on NA cars. You simply are not getting an big advantage.

I do think it is smarter for Mazda to go to 6 ports on the Auto though, since they are standarizing on 1 engine configuration and most of the same aftermarket parts can be used between the auto and M/T. Of course, if they worked on the tranny problem, they may have done more. I would be interested in seeing the 0-60 and 1/4 times of a 6 port auto with the rev limiter cut and ATF cooler and different AT fluid.

In any case, the 4 port and 6 port Auto, could use extra horsepower from FI and/or a better tranny to allow them to rev higher.

The VFAD duct is simply a bypass of the primary intake sleeve.
It doesn't really flow any more air (its path leads into the existing intake port on the airbox) and it pulls air from the same place as the primary duct, so it is no colder.
It is merely an intake noise countermeasure.

so moon_asaad's car doesn't have any power?


He is SCed. From what everyone says it is very impressive

so moon_asaad's car doesn't have any power?


He is SCed. From what everyone says it is very impressive

I think the point is not that the AT can't make power, just that, dollar for dollar the MT will make more. So, moon's car might put down great numbers. For the same amount of work, he might be putting down more on an MT though. Is it really important to have the most HP possible? Meh, I think it's more important to find the car you like the most and make it into the car of your dreams. My other car is an auto. There are many benefits.

I think the point is not that the AT can't make power, just that, dollar for dollar the MT will make more. So, moon's car might put down great numbers. For the same amount of work, he might be putting down more on an MT though. Is it really important to have the most HP possible? Meh, I think it's more important to find the car you like the most and make it into the car of your dreams. My other car is an auto. There are many benefits.


I figured as much.

Pettit's kit gained more on the AT than on the MT at 4 psi. We'll have to see where the AT stops making power, though.

I think it comes down to the right mods and what you want from your car. The right combination of mods on the RX-8 Auto, will do a lot. Who knows, a tranny solution for the RX-8 Auto may be around somewhere or around the corner in the future. Furthermore, what will work on the Auto, may be something different than what works on the M/T. So it may require those people that believe they can do more with the RX-Auto and chase the right mods and solutions.

The RX-8 Auto is not as limited as some people would like to believe. I think certain people are just die-hard M/T and the word "auto" sends them into orbit. The reality is that technology is relative. There will be advantages and disadvantages to everything. Just like there are advantages and disadvantages to having a M/T or an Auto.

The RX-8 engine still has a while to go, before its full limitations are known. Nobody, has come out with a kit that they can claim has achieved the MAX performance on an RX-8. Though, somehow, Mazsportscott's turbo kit seems to be making a run for that title at least. But, personally, I prefer a Supercharger (Twinscrew or Axial Flow(if they can do 4 ports)). In the meantime, there is nothing stopping RX-8 Auto owners from improving their cars overall, including their straight line performance.

I still question how much the Auxillary port is having an effect in 0-60 and the 1/4 mile, due to the limited time frame and distance. Obviously, at sustained high speeds the Auxillary port would have its advantages. But once you are going over 110 mph, who cares, unless you are talking at the race track and a distance race? There is not many public roads that you can push an RX-8 to 120 to 150 mph for sustained period of times and there is not a lot of people that want to, outside of the race track.

It seems to me that the manual is "taking it to the auto" at short distance because of the tranny and by doing higher rev launches. Having my rev limit cut (please get a new ATF cooler and new AT Fluid before doing this) produced faster 0-60 and 1/4 mile times for me. I will often go to 8,000 rpm (for short bursts) with no issues, so there may be a little more in the RX-8 Auto's tranny if taken care of the right way.

Also, if we are talking about getting more air into the 4 port, than it would seem there would be a number of solutions (like ram air intake and maybe others) to help do that. So it would seem that a way could be found and in most cases people are just talking about the effect it would have in the 0-60 to 1/4 mile.

I don't know i'm happy with my AT, atleast for the fact that i'm not replacing the clutch every 10k miles.......... clutches are a pain, mod it out.................and go from there.

I just got my RX-8 (early august) and I love it, but now I am trying to learn more about it. From what I seem to be able to find, the AT and MT now have the same 6-port engine, but have different power due to the transmission. (Which makes the first part of this thread very confusing if you don't look at the posting dates.)

Anyways, I was wondering if the 6-port engine was added for late '06 models, or do all '06 ATs have the 6-port? and, if the engine is the same, will the turbos/SC for the MT work with the AT. I figure I should start saving now if I want to be able to afford these when I'm ready to void my warranty.

Feel free to slide this into any other thread that would be better fitting if this is the wrong place.
Thanks

I believe all 06 ATs were 6 speeds. One reason I got an 05 4 speed was because I could get it for dirt cheap, I imagine because it was a leftover and the 06s were coming out soon with the better engine and tranny.

Absolutely fabulous information. Very appreciated RG.

The VFAD duct is simply a bypass of the primary intake sleeve.
It doesn't really flow any more air (its path leads into the existing intake port on the airbox) and it pulls air from the same place as the primary duct, so it is no colder.
It is merely an intake noise countermeasure.

I recently removed mine (to fit the RB duct) - Agree that it is for noise control but it does actually flow more air when it opens .

Closed : sleeve only supplies air
Open : sleeve + secondary duct supply air .

that second post kills me every time

*sobs* i just wanna cry!!!

This doesn't mean give up on the engine. Even the 4 port makes more power than any 13B street engine did without a turbo and I've seen completely stock 13B's boosted to over 600 rwhp before. You are merely starting from lower on the totem pole than the 6 port engines and will ultimately have less total performance potential.

Just curious RG, what do you think about the higher torque output the 4 port has? Why is that? How do you think it will effect boosting a 4 port? Any ideas on why Pettit's charger produced higher gains (though lower overall numbers so far) than the MT engine?

Obviously there's some uncertainty here since there aren't many boosted 4 port renesis engines, but I'm interested in your opinion.

The port timing is more suitable for lower rpm power than the 6 port. The 4 port is still different than just a 6 port engine with 2 less ports. There are port timing differences between them as well and this affects powerband. The intake runners are also longer which is also better for lower rpm power.

another issue is that there will never be as much research put into the 4 port because the new autos are 6-port.

i guess there are some other 5-speed 4-ports in other countries

Here's another thing I'm wondering. How will certain power addings mods affect the 4 port auto differently? Meaning, how would something like a midpipe affect a 4 port compared to the gains on a 6 port? This one has me thinking a lot.

Here's another thing I'm wondering. How will certain power addings mods affect the 4 port auto differently? Meaning, how would something like a midpipe affect a 4 port compared to the gains on a 6 port? This one has me thinking a lot.

Yes! very GOOD question! :ylsuper:

I was thinking of getting one.

The port timing is more suitable for lower rpm power than the 6 port. The 4 port is still different than just a 6 port engine with 2 less ports. There are port timing differences between them as well and this affects powerband. The intake runners are also longer which is also better for lower rpm power.

That definitely makes me want to keep the 4 port over upgrading to the 6AT. I don't have a problem with the power the engine makes up high, it is the off the line punch that i would like to improve. Hurry up, Petitt... :)