Farsyde

yeah that's the greddy Z. SCC has an article in the most recent edition on this, however i do beleive their dyno run only netted in the ~320 range. Which is still great. This is actually the first aftermarket twin turbo job i've seen since the rx-7 that actually gave great posistive results. Now all they have to do is gut that sucker and it'll be nice and fast.

EDIT: I'm really impressed they were able to safely setup the turbo's in a V6 environment

wakeech

here, kidmarc (welcome friend) posted this in the Tech Garage, i just had to C+P it

for those that missed the link, i suggest you check it out here:

http://www.babcox.com/editorial/us/us99814.htm

FritzMan

Having lived with a twin turbo RX-7 already, should I choose FI, I'd definitely go with a supercharger this time around. IMO, the problem with turbo are several:

1) They run hotter than superchargers, creating backpressure into the engine. Not only is the extra heat hard on reliability to everything under the hood, but it's also harder on the cat system (my FD melted and clogged). I saw over 1400 degrees on that car without trying too hard...
2) Boost is not linear to throttle, you can get used to it, but it's not as easy to drive at the limit
3) Should the wastegate be insufficiently sized, dangerous boost creep can occur on some days (cold ambient) and not others.

Personally, I'd love to see a 75 hp self-oiling centrifugal supercharger kit running 5 psi, hence no real need for intercooling. Packaging would be easier, overall kit would be light, parasitic drag would be minimal, running temps (although higher due to horsepower) would be reasonable, and throttle-to-power output would also be direct. Sure, there wouldn't be gobs of low-end torque, but I much prefer playing in the mid-high end powerband anyway.

wakeech

boost with a supercharger isn't linear with the throttle, and in fact is not throttle dependant at all (unlike a turbo): boost in a supercharger is entirely rpm dependant.

...an improperly sized wastegate is only the fault of the idiot that chose one that's too small, it's not a downfall of the turbocharging system.

FritzMan

Technically, you're correct in the sense that 50% more throttle doesn't give you 50% more RPM. However, it does become close to linear-like at higher RPM - and is still much more linear in delivery than a turbo which has a more variable RPM, throttle, boost relationship. Regardless of throttle, X RPM always delivers X boost on a supercharger, not so on a turbo.

That leads to another supercharger advantage, full boost in the lower gears. Typical turbo cars don't see full boost until 3rd gear when time and engine load are signicant enough to deliver it's full potential.

"...an improperly sized wastegate is only the fault of the idiot that chose one that's too small, it's not a downfall of the turbocharging system."

- hope you're not saying Mazda engineers are idiots!!! Cuz it's their design (FD) which used to overboost 100% OEM. Granted, it would be -20 outside (I drove the car year round) so I'm sure their engineers didn't figure someone would be driving a sports car in that temp. The super cool air would create a better burn to the rich mix making more exhaust than what the FD could handle. I do agree wastegates should be properly sized in the first place, but as I've shown it's difficult to anticipate all possiblilties. IMO, the dependency on a wastegate is a little scary, although they are reliable, I had a pop-off valve fitted to my car. With a supercharger the only way to overboost is to over rev.

wakeech

...they WERE the ones who tried too hard on the TT system for the FD.

babylou

Not true. If this was true then there would be no need for a throttle. It would also make it impossible to "cruise". I can see it already. At 80 mph the engine must turn 4,000 rpm, the car requires 16 hp to overcome losses but at 4,000 rpm the engine builds 10 psi boost and 160 hp. Since the throttle is useless there is no way to match engine power to required power. I guess we will have to turn on and off the engine periodically like they did in WW1 radial engined aircraft.

FritzMan

Not quite sure I'm following you here. Centrigular superchagers are forced to generate a specific boost for specific RPM due to the non variable direct connection to the engine (belt). Actual boost used by the powerplant is dictated by how much the engine is capable of ingesting at a given time (ie: throttle opening). Excess boost is bled off or recirculated into the system (FD blow-off valve bled back into the airbox). So cruising is possible by simply bleeding off the excess (kind of like a intake charge wastegate). It's a bit of a waste of horsepower really because parasitic drag had occurred to build that boost which could easily be thrown away. Most manufactuers have gotten around the problem of wasting power when boost is not needed by having a vacuum activated switch to free-wheel the supercharger's pulley until power is needed. Hence, engines can switch between normally aspirated and pressurized.

Efini 8

i think mr.supercharger is partial to superchargers... I personally would go turbocharger because it dont want boost at low rpms, and with boost at high rpms it is mainly for race application. however I firmly believe that the installation of a forced induction system as well as the quality of its design and performance should be the main concern

Ahura

This just came across my mind about turbocharging the RENESIS, and I think it's probably been speculated and tested by Mazda engineers.

Previously, rotaries are fantastic for turbos since the exhaust from the peripheral exhaust ports hit the turbine almost head-on (depending on the manifold, of course). Now with the side exhaust ports, the gas has to take a more convoluted path which takes away the advantages of an older turbo motor. This doesn't mean that can't turbo the motor, but it won't be as effective as before. Also, the peripheral ports also allow the use of huge A/R ratios (big high-end power) on the turbine without much ill effect. On the other hand, you don't have any overlap with the RENESIS, which is bad for turbos.

IMO, I think it would be more beneficial to go with a larger displacement 2-rotor in the future. No doubt you lose the tunability of forced induction, but you gain needed low-end power and keep the simplicity and reliablity of a non-turbo rotary.

wakeech

...side exhaust ports coming out into a turbo is still less convoluted than flowing in and out of a head (on a piston engine), or at least comparable (not worse).

A/R ratios have the same effect whether you have a P-port exhaust or not... RX-7 guys just like to think that because they port out their engine a LOT that the turbo spools faster (without a shred of quantitative analysis to prove this).

overlap is actually very bad for turbos, as with the high-pressure nature of hte system, you can end up with a lot of reversion (that means gasses flowing the wrong way) or a lot of charge flowing out the exhaust (just as bad for power as it is for emissions). what's actually bad for the turbos in the RENESIS is the long-duration intake cycle in the 6p motors.

:D yes. more displacement is better than less.

FritzMan

So does that mean I shoud refer to you as "Mr. turbocharger" then?

Don't know if I was being referred to here or not, but just so you know, I'm not a die-hard SC fan or anything. In fact, I've never driven a centrifugally charged vehicle. I'm simply posting the facts as I see them. As my previous posting stated, I've done turbo (and lived with it's woes) so I'd like to try SC. Who knows, maybe there's an equivalent list of problems with that setup... IMO, for my fictious application of 325-350 hp and some improved low-end I think SC would be fun to try. If someone were to ask me to the best way to make massive power, then by all means, turbo it is.

Efini 8

sorry I didnt mean any disrespect, I just thought your post was a little biast toward superchargers.

Supercharger

Turbo and rotary is not a good combination for a road car. Racing cars are a different story.

JSG confirmed that the engine bay is already very hot without turbo. Just think how much hotter it will get with a turbo. You won't be able to open the hood.

TerenceT

give them time and show them their demand

http://www.pes-tuning.com/oldsite/Im..._installed.jpg

they made aux s/c for the v6 A4 before, and eventually, remade the intake runners and making the whole system much more compact and efficient

i have no idea how or where they'll put one for the 8

they might go with a centrifigual s/c which is as compact as a turbo but doesn't have the lag of a turbo (a la spoon race s2k)

http://www.imagestation.com/picture/...2/fbf6577c.jpg

jmanolov

http://www.miataforum.com/cgi-bin/ul...&f=11&t=012506

bern

http://www.rx8forum.com/showthread.php?s=&threadid=4948

AJatx

If you'd like to keep the intake manifold stock, then there really isn't much room at all.
The intake manifold is bigger since the intake tracts run wider to have a smooth curved shape instead of the traditional sharp bend on the bottom of the LIM.

I can see a small turbo being placed somewhere near the front passenger side wheel well, but the manifold design would be complex for it to be efficient.

We'll see what the aftermarket folks have for the RX-8 soon.

J

TurboSE

Actually, the turbo does spool quicker when the exhaust is ported on the 13B. The earlier opening of the exhaust lets more unburned fuel escape which helps the turbo to boost higher and quicker.
As for the renesis, the exhaust pulses don't have the same kinetic energy as the earlier p-port motors and the temp is also lower making it a better candidate for supercharging.

Efini 8

ok I have seen the rumors in several car magazines such as Sports Compact Car, etc. that report Mazdaspeed is developing a turbo kit for the RX-8. Also many people are speculating on the boards about the possibility of a forced induction system.

I have confirmed with Mazdaspeed that they are not currently developing a turbo kit. If they do decide to develop one, much r&d is going to be required. The turbo most likely will be prototyped on a Mazda race car in Japan first - maybe the JGTC? That is just an educated guess.

However, this is what Mazdaspeed knows about the capabilities of F.I. on the Renesis:

- Can Handle Minimal Boost Pressures (5 psi or so)
Compression Ratio for RX-8 is 10.0:1

- Mazdaspeed is heavily studying and working with the Renesis as well as the RX-8. Performance is in mind.

- Mazdaspeed is working along side other companies to develop certain parts.

Again, the Mazdaspeed TURBO KIT is just speculation and nothing but a rumor. I just wanted to clear this all up. They might decide later to build one, but according to the my sources, they are not actively pursuing a F.I. solution currently.

MrWigggles

They are not actively pursuing a turbo or not actively pursuing FI in general?

sixspeed

Details in a UK magazine on the future RX-7 say that the next gen will produce around 300bhp using a modified Renesis platform (wider rotors, increased capacity to 1.6l) ....

If that's the case, then I wouldn't be surprised if they use that to form the basis of the MPS RX-8?


-andy-

Sputnik

Well, we do expect the MPS RX8 to share a bunch of things with a possible upcoming RX7. Engine upgrades (we do know that 300 hp was a goal, we don't know the method), possible SMT (we know that they were at least working on that), etc.

---jps

Jt-Imports

My Mazda guy here in Japan is quite hooked up, if he doesnt know he will spend a week trying to find out hehe.

SOOOOOOO i will ask if there is any info flying around, or just BS

JT

wakeech

water spray, 12:1 fuel maps , big *** IC's, and race gas/xylene rich :D