RotaryXTypeSH

I'm worndering what is the difference between the automatic version of the RX8 and the stick shift. I know the difference is the transmission but how about the engine. I thought the engine is the same? with the same engine one is detuned right and the other is a higher verison (performance version)


My question is this:

Automatic Version: 210hp/7200rpm , 164 torque/5000rpm Redline: 7500

Stick Shift (performance version): 250hp/8500rpm , 159 torque/5500rpm Redline: 9000

If the automatic version has a computer chip to limit the rev for the RX8 and if a performance was swapped then would the Automatic version can gain more hp (like the stick shift??)


Thanks

Hercules

It's the same engine from my understanding, but the lower powered one is just detuned.

I am not sure what you are asking otherwise.

RotaryXTypeSH

my question is that the automatic rev limiter is at 7200rpm, if i could increase the rev then is it possible to gain hp?

lefuton

the auto renesis has 4 ports and the manual one has 6 ports

RotaryXTypeSH

then what difference does it make? how could i gain hp if i'm getting an automatic one?

RotaryXTypeSH

does it really make that much of a difference in performance? then i would consider getting it turbo charged

lurcher

The engine block itself is the same AFAIK, however the intake system is physically more elaborate on the high power model (3-path vs. 2) so a chip alone wouldn't do it.

HEVNSNT

The block is not the same. Auto:4 ports, High power:6 ports. The front and rear side housings would then be different.

Buger

You could "make" the engine in the automatic rev higher but it will not make very much power at higher rpms because the lack of the extra ports and the lack of the high rpm dynamic effect path mean that the engine will not breathe very well at higher rpms.

Even if you could make the engine breathe better, the torque converter of the automatic would not handle the added rpms well.

wakeech

the auto is a better candidate for FI tuning, as the smaller 4 ports are more efficient at moving a lot of pressurized air at lower engine speeds...
so, you could try supercharging or turboing it... but yes, there are many differences between the two engines which make the auto unfriendly to rpms.

cueball

Like buger and Wakeech said, you could make it rev higher, but the reason mazda limited the RPM was because they kept blowing up the torque converter. But if blowing up a torque converter is worth the extra RPM be my guest.

MrWigggles

I still don't understand why you think the higher reving 6 port design is going to be hard to FI and harder than the 4 port version.

Jackson Racing using Eaton superchargers has had good success with VTEC engines that rev all the way to 8500 RPM.

-Mr. Wigggles

wakeech

and...??

you can't compare a B16 or a K20 with the RENESIS... they rev high (although not nearly as), but obviously aren't the same in most other ways, other than they burn complex hydrocarbons and atmospheric oxygen to turn the wheels of a car.
you can set pulley ratios for low end pull, or high end pull, or somewhere in the middle with a supercharger, and still never get EVERYTHING you want...

in any case, my point was that the four port layout of the automatic engine block is better suited to forced induction tuning than the high-power six port layout... it has little to do with the lower redline, although when looking at it from a supercharger point of view, this lower operating range will be easier to tune to as well. :p
i'm not saying you can't do it, i'm saying the low-power engine is better for it.

lurcher

FWIW, the low-power engine is attached to a manual 5-speed transmission in Europe and the rev limit is the same as on your auto model AFAIK.

HEVNSNT

I agree with you. And to add. The quantity of air entering the engine when pressurized is different than when ambient. An NA intake system is designed around the air velocity of the intake plumbing. A FI intake system does not need increased velocities. The complexity of the 6 ports also affect fueling during transition. Mazda turbo 13B's have always been 4 ports.

MrWigggles

I think the port number is irrelevant once forced induction is added to the mix. The stock method of trying to accoustically tune the intake with just the right air volume with valve and intake length manipulation will be irrelevant. Wether a supercharger or turbocharger I bet the the first ECU mod is for an FI system will be to open all ports, period. (especially for the high boost apps since the values designed for 1 bar might not be designed for the added pressure of say an additional bar or so)

To me the 6 port will just allow for better breathing over the 4 port design.

-Mr. Wigggles

Sputnik

Will the 6 ports make forced induction impractical? No. But if you had a choice between 4 and 6 ports, the 4 port will actually flow better for forced induction (why do you think FC NA rotaries were 6-port, and why the FC turbo engines were 4-port?). Tuning an intake path for NA is very different than tuning for FI.

---jps

RotaryXTypeSH

Thanks guys for all the great infos

wakeech

THANK you... sheesh.

as i was saying before, the smaller port areas allow the pressuruzed air to flow at a higher velocity at lower eninge rpms. this helps maximize your volumetric efficiency in a system where your charge is being crammed in there continuously, as opposed to drawn in by partial vacuum.

MrWigggles

If you think 4 ports will work better than they simply won't use the last 2 of the 6 port engine, cap'em off. But the tuners will use all 6 ports and people will buy the FI kit. It is interesting you are quoting a totally different engine from over 10 years ago in your analysis.

The number of ports just isn't going to matter.

It isn't worth arguing this anymore.

-Mr. Wigggles

wakeech

it's true that the solution would be to wire/fill the tertiary ports, and use the higher revving motor, but Sputnik and i aren't incorrect in saying that using only 4 ports is a far better solution than the 6... the lower velocity of the charge air (plus the necessarily longer length of the intake, plus more complex path to the engine) does nothing but hinder your compressor in doing it's job... or at least doesn't help it any.

in any case, what i wanted to point out is that the 13BREW isn't a 10 year old engine, and has been continually developped and produced for the JDM up until the middle of last year. they have never used anything but a 4 port layout for FI wankels, and they probably always will. there is a reason to it: just 'cause the RENESIS has a different expiration port layout doesn't mean it's "totally different"... the inspiration side hasn't changed much, other than the intake runner system: the valves and ports are nearly identical (albeit relocated on the housings)

MikeW

The ports also affect the timing of intake charge too.

Having all the ports open all the time is bad.

Sure the engine will fill well at low rpms, but the air/fuel will not mix well.

So leave the ports to open up at their proper rpms, 3750 6000.