If you could go for forced induction...
 

If you could go for forced induction, what would you get?

I am curious as to your motives for considering each system.

IMO you should leave the superchargers to v motors

but i am a fan of vortech especially with thier S2000 kit

For some reason, I just think Supercharging would be a better fit for this motor. IF I decided to go FI, the SC would get my love.

SC, the renesis needs some torque early in the low end.

I put in my vote, but I'm a little biased now.

If properly sized, a turbo can provide torque just as early as a supercharger.

Either one, really. But the car does need low end grunt so the only one I really want to avoid is a centrifugal sc.

i personally would go with a supercharger. the reason i say this is because of the power curve this car has its just too linear and i think that a supercharger would better accomodate it. i wish procharger would come out with a kit or hell ever a vortech would be nice. the low end grunt doesn't bother me. other than puttin round town i'm not in the lower rpms too often lol

The only thing keeping me from turboing my car is the UPS man. I dint know enough to make a choice so I lurked for 3 months and woalah!! I still don’t know Jack. But it’s what everyone else is doing so it seamed like a god choice at the time. Pretty sheeple huh?

supercharger, as long as it's not centrifugal

supercharger for reliability. For turbo I'd get back into my FD.

Supercharger

basically for a lot of the same reasons stated here! It seems like it would be a good fit for the Renesis and the reliability!

According to Rotary God, supercharging is better:

That's actually a little backwards. The older peripheral exhaust port rotaries were more suitable for turbochargers. This was due to the suddeness of the ports opening. They reached full open much faster than in the Renesis which caused a very strong pulse that was perfect for moving a turbo with. The Renesis exhaust ports resemble a piston engines more in terms of their flow profile and rate at which they open.

A trubocharged engine and a supercharged engine also require different timing. THis may sound strange but with a supercharger you want less overlap whereas it isn't as critical with a turbo. The 13B's had some overlap as do all piston engines. With a trubo the added backpressure in the exhaust will help prevent the intake charge from getting blown through during overlap and out the exhaust. You almost always have more exhaust pressure than intake pressure with a turbo which is why this can't happen. With a supercharger you always have more intake pressure than exhaust pressure. This means that if there were an engine with overlap, you would blow some of the charge out the exhaust. The Renesis has zero overlap. This is perfect for a supercharger. The intake ports are also large compared to the 13B intake ports which helps even further. The exhaust pulses are also not as strong as the 13B's which would aid a turbo better. None of this means that a turbo can't work very wel on a Renesis. Due to the exhaust pulse energy difference, it would just require a smaller exhaust housing to get the same spool rate. This will become more of a problem at higher rpm's though as a smaller exhaust housing makes less top end power than a larger one. The 13B is just better suited to make big power with a turbo.


https://www.rx8club.com/showpost.php...&postcount=351

i'd like to go the turbo route as well..

Yeah, the argument that you get more torque early on in the rev band is only applicable to one kind of supercharger (Lysholm/Roots/Screw type unit). The other kind of supercharger (centrifugal) will provide you with similar, if not worse tq characteristics on the low-middle end of the rev range, but more power up top. Good & bad points about both types.

With my Greddy I can get full boost at as low as 3000 RPM.

Remember the White Supercharged Mazdaspeed Concept Car? Here is info to back up what Rotarygod said about the exhaust ports:

Bern posted these comments on Rotarynews.com:

"This is a development project that members of Mazda's R&D team have been working on. Because our engineers also happen to be enthusiasts, they're never completely satisfied and they're always tuning and developing vehicles one step further. This car is not for general sale now or in the future.

We're not ready to confirm when - or even whether - a MAZDASPEED version of the RX-8 is coming. We're always looking to improve the power, styling and drivability of our vehicles in each successive generation, and we're certainly looking at ways of adding the MAZDASPEED-DNA to RX-8, but we are not ready to talk in more detail about it.

Mazda touched on some details about this particular car, though...

* It is supercharged. Because of the location of the exhaust ports in the RENESIS rotary engine, it doesn't respond in quite the same way to turbocharging as earlier rotaries. Our team thought they'd experiment with supercharging for this project car.
* Virtually everything on the car is custom-designed and built, including the bodywork, interior trim, suspension and exhaust. Our R&D team saw this project as an opportunity to take the RX-8 as far as they could, while still maintaining its streetability."

With all due respect to those that have gone turbo on the Renesis, my vote went to SC.

I still prefer a sequential twin turbo setup although it sucks practically

You know... I can't stand the sound of superchargers... and all in all I think I just like Turbos better. I think they are on fairly even ground, but if you look at what we have seen, it would appear that there are a heck of a lot more proven turbo options available at this time.... 310WHP on the Greddy! 326 if you are willing to dump a boat load of cash on the SFR kit.

Bugger. When I saw this was a poll, I thought I might have been able to vote for myself. :aroused: :naughty:

Cheers,
Hymee.

Why Supercharger?
 

Boost is boost.
HP is HP.
Turbo for you,
SC for me.


/I really just like the SC sound better..... :lol:

yup, boost is boost BUT some methods are currently better at making boost then others.

ie; Pettit makes a SC BUT MM's turbo is making more power through almost the entire band.

Just comes down to what you're you looking for out of your car, what your end-goal is, and how much you're willing to spend.

All forced induction "sucks" or "blows"...
:lol:
Most turbos blow through as opposed to suck.

Get a used GReddy kit & MM's upgrade kit.

Nothing else can touch it for the money.

:worship:

We have not yet seen a single SC kit for the RX-8 that can make as much torque as the smallest turbo kit available for the RX-8.

Additionally, we have not seen a single dyno that shows any SC kit for the RX-8 make more boost or torque than the MazdaManiac GT3071R turbo kit in the low end, where the SC proponents claim the SC has an advantage.



That is the sound of inefficiency in motion. There's some new SC tech out recently that is more efficient, but lacks the sound.



I can think of zero advantages of the SC over a TC for the RX-8. The ONLY justification is personal preference. The SC loses in power, torque, cost, and anything else you can throw out at it.

Reliability? Please explain in more detail how you think a SC gives you more reliability. Boost is boost. It's poor tuning that gives you engine damage. Just ask all the people getting detonation with the Pettit kit recently. Remember, the install base of the Pettit kit is quite small compared to the GReddy. So even a 10% rate of problems on both sides will make it look one sided.

So mysql, you are saying all the supercharger people are unhappy and want to trade in for turbo? Well we know that is not true.

. The comparison chart between the SC and Turbo are not INDEPENDENTLY tested on the same dyno. The chart on this site is a reference.

. Power delivery and "feel" of the car would be different between SC and Turbo. This would be a factor.

. There may still be more to be seen and said about intake pressure and exhaust pressure, relative to the SC and turbo and relative to the longevity of the engine.

. The SC kits can meet the HP target of a lot of users.

. The Pettit SC kit can still be improved, just like the turbo kits.

. New Greddy kit + MM upgrade is at a price point close to the SC kit.

. There were a lot of people with massive problems and blown engines with the Greddy kit. To say one is not better or is better, you need to provide statistical proof. To simply claim you know of some detonation problems with the SC kits too, does not mean the SC kits less/more reliable than turbo. The SC kits may well be more reliable than turbo, the proof would be some scientific data like a customer survey.

. Would love to see SC kit vs turbo and at similar PSI on the drag strip or track. That would be a better reference point.

To claim a turbo kit would dominate in install, maintenance, engine longevity, etc.... is deceptive.

The greddy kit should not be used as a high water mark for all turbo kits... if anything it should be used as the absolute LOW water mark. If you had properly done your homework you'd know that the greddy kit has some serious flaws from the factory that need addressing.

And to the say the same thing about superchargers isn't??


Not to mention a lot of people that having issues with the Pettit kit and detonation (even blowing a few motors) aren't coming public and keeping it in their inner circles.

Not to mention a few of Pettit SC and flash cars are dyno'ing lower than factory rwhp and tq....

True, but the error, even if its 4% - 5% still puts the turbo clearly out front by an order of magnitude.

True, but is personal preference as mySQL pointed out.

Also true, but it is likely that both will suffer a load-based failure long before we find an answer to that question.

A point that can be reached for 30% less cash with a turbo.

That's like saying Jessica Alba is just as much a candidate for a make-over as Janet Reno.

Only if you consider $2500 close and want to drive an S/C without engine management.

Oh yeah, customer survey. Very "scientific".
There is no good way at arriving at a conclusion to your proposed survey. Certainly not once you understand that engine managemnt is all that stands between functional and non-functional.
The GReddy kit didn't blow engines - the tuning did.
Pettit got around that bit at first by pushing that choice off on the purchaser.
Eventually, they opted to pop people's motors for them.

On a drag strip, both suck - but the turbo would suck far less.
I would like to see the two in a carefully planned head-to-head, but using PSI as the reference would be ludicrous. Using PSI as the common denominator would be like using "brunette" as the point of comparison for the above-mentioned vixen.

Then the same would be true for the S/C.

I think the days where SC's have very clear advantages are over to a degree...especial centrifugal SC's...

Turbo's are just better choices in todays world, think of how many OEM choose turbo over SC...in fact who still uses SC's any more

MB switched to NA instead of SC's
Mini Coopers switched to turbo instead of SC
Cobalt SS was SC'd but replacement HHR SS is turbo now


Other than the ford/jag/land rover SC v8 no one really uses them any more...oh wait the new ZR1........

No need to start pounding each other everybody.

Remember the poster asked which one YOU would like, not which one is better.

I for one am opting for an SC. I have some reasons, but basically, in this case I wanted an SC, and have nothing against turbos.

My friend has a greddy based setup and loves it.

Good rebuttal MM.

Still there is the Hymee SC, which is suppose to be released soon. It's very interesting what he has done with the throttle body and his calculations for incoming air.

By the way, I have my eye on the MazdaManic Turbo kit too. Of all the turbo kits, there is no way to ignore this one, no matter what side you are on. I know it will be a very good kit, even the present upgrade looks good. I'm just one of those that rather see it "detached" from the Greddy kit.

Though it seems beyond belief, I'm actually neutral. I'm more defending the "point" that there are 2 sides and SC have their place. I also lean towards maintaining the stock feel of the RX-8, just with more power.

I think the dust will definitely clear on this whole debate around a year or so. Maybe even by October...

The new S/C tech, would that be a Lysholm twin-screw compressor; or the Axial Flow S/C?
:eyetwitch

I never said anything of the sort.


I can't directly argue with this since I don't know the capability of the twin screw used in the Pettit kit, but I can also show you that the GReddy turbo is "perfect" at 6 psi. Higher levels of boost don't go over well since it cannot supply enough air to the engine at peak rpm ranges. The same can be true of the Pettit if they selected the compressor properly for the stage 2 and it cannot flow well enough to release the fabled stage 3 wheel. This of course, completely leaving out one of the huge advantages of going turbo - on the fly configuration. If your next argument is that adjustablility is bad because people might not know what they're doing - my reply to that is that they shouldn't be driving if they can't be trusted to touch their own car.


Are you not reading what I've been saying? I never ever claimed one was more reliable or safer than the other. That would be an absolutely stupid claim. What I have been saying is that anyone who claims better reliability for the SC is talking out their ass. Just because I do not agree with someone, does NOT mean that I take on the opposite of their argument. Come on!


Dude. WTF, seriously. When did I or anyone else here say that? Are you making this stuff up as you go or what?

I said the turbo beats the SC in performance hands down. SC's lose in torque, lose in low end power delivery, and lose in cost. Now, if you came up with install, maintenance, and longevity as my "anything else you can throw at it" statement, then I guess the SC can be equal in some regards, but you're really scraping the bottom of the barrel and putting words in my mouth.

Eaton's TVS, which came out in 2006.

"Meegan tells us that Eaton's Twin Vortices Series (TVS) supercharger uses four-lobe rotors in place of the conventional three-lobe units, making it quieter and more efficient. The parasitic loss to drive the supercharger is around 70 or 80 hp, but it would have been more like 120 hp with the old supercharger, Juechter says. For the LS9, the supercharger cranks out 10.5 psi of boost. "

That isn't a twin screw supercharger, as both rotors are 4 lobes. Twin screws have a male and a female rotor, with a different number of lobes. That Eaton is just a glorified roots blower with twisted rotors and extra lobes. It does not create internal compression like a twin-screw (or a turbo's compressor for that matter), hence it has lower efficiency. They are cheaper to produce for the OEM's, hence the marketing spin trying to make them appear to be twin-screw like. And it appears as if that marketing spin is working, as I just about fell for it myself!!

I love the argument about S/C losing out in torque. We made double the HP (hence torque) essentially from idle. That is not possible with anything other than a positive displacement supercharger. It is also the reason top-fueller dragsters don't sit on the start line bouncing off the rev-limiter before they launch with blistering acceleration. Turbo charged dragsters (and I'm not saying they are not any good - heck, I've pit crewed for a number of them) must, by the very nature of the turbo, sit on the line at high RPM while the thing spools up. Blown cars sit there, basically idling, then go blaaat....

Cheers,
Hymee.

It must be in the air... I never said it was a twin screw. lol.



From the few SC kits available for the RX-8, there are zero dyno results that show a SC making more power or torque even in the low end. I'd be pleased to see you do better, and wouldn't be surprised since I hear a lot of good stuff about yours.

Adiabatic is definitely higher on the TVS line vs. the previous MP series, but man is it expensive, at least at the moment...

Sorry - I didn't intend to imply that is what you said. I was just a little frustrated on reading it that the makers try to make out it is something wonderfully new with better efficiencies, and try to use terms that conjures images of twin-screw.

I haven't posted a formal dyno chart yet as it was early developmental days, but I have posted videos on the dyno, and also a frame where you could see the MASSIVE extra torque/power at the bottom end. It was something like 40 or 50 HP increase.

https://www.rx8club.com/attachment.p...1&d=1205849949

The red line is the stock baseline. The blue lines are blown runs. I hope that dispells any myths.

Cheers,
Hymee.

What price for instant, no-lag boost?

How much do you call expensive for one of these TVS roots blowers? I'd like to compare to how much the Autorotor's are.

Cheers,
Hymee.

I think the myth that a supercharger is more reliable is because a supercharger has no wastegate hose to pop off, and you rarely hear talk about somebody "blowing" a supercharger like the turbo guys talk. I suppose from the standpoint that a supercharger has less components and moving parts, it's more reliable in theory if you take it in isolation. But that doesn't mean its not capable of engine damage.

As for me, I'm not casting a vote yet. I've been eager since SSX for Hymee's kit to hit the market, and if it puts up good numbers and more importantly has a good power curve and price, that's the one I'll buy. But MM's looks like a great alternative as well.

I'm afraid my prices would definitely be skewed as compared to yours...as prices quoted to me for all these positive displacement SCs were msrp equivalents, or something in that ballpark...also the TVS line hasn't been fully developed for the smaller units that would be appropriate for the Renesis, or that was the last I was told...but if you'd like to take it further shoot me a pm...

Although I was quoted earlier, I actually like both types of systems. It just depends what the intended use is. I do think it's funny how people will argue that a turbocharger is better than a supercharger and then try to give reasons for it. The fact of the matter is that a turbo is not always better than a supercharger. No it doesn't always do everything better although turbo proponents would have you believe they are always superior and will argue this to death. Having owned a turbo rotary in the past I can tell you that yes they are lots of fun and I'd gladly own one again.

My dream forced induction system for a street rotary is Hymee's twin screw kit. It's beautiful. It's a much better piece than Pettit's kit and I'm sure capable of far more. He hasn't taken any shortcuts and there are so many things about it that are much better engineered. It's a better implemented system and what I really like about it is that it's easy to use an air/air intercooler. The air/water systems are really holding the Pettit kits back on the street. For drag use they're fine. I suppose you could change this but Hymee's would be very easy. Yes it's expensive and this is one reason why people argue in favor of turbos. That's a very RX-7club argument though and not one that should have any relevance if you really love your car. Other people's budget opinions shouldn't effect your choice if you can afford it. If you're cheap (or poor!) then yes a turbo is a better choice. There are so many reasons why I love twin screws but I'm not going to list them because I don't need my reasons rebutted with bullshit. It's all an opinion at the end of the day anyways and again, I've owned a turbo rotary and yes I'm a fan of them.

Here's one simple reason I will say I'd favor the twin screw for street use. It makes it feel like you have a larger engine under the hood. A turbo system, even a "properly" sized one still feels like you've added a turbo to a small engine. It's hard to describe but you just need to drive both to understand. Yes there are downsides to a supercharger system but in my opinion for street use there are far fewer of them than there are for a turbo system. I'll let the rest of you argue about that statement as I'm not going to even try to justify it.

You mean more moving parts, right?



I don't talk theory in these types of discussions.

I talk strictly in the present time. What do we have available NOW. So if you go back and read what I've said, I think my argument is sound.

I actually was considering a Pettit SC at one point in time. But once you dig deeper....

I wasn't actually directing it at you. It's just a general statement. I've been involved in these types of discussions/arguments on the 7 forum way too many times so my statements aren't directed at anyone in particular anymore.

I agree with RG. Just looking at Hymee's kit will let you know what a top-notch job he's done. It's a gorgeous piece of machinery, shiny chrome and black, and feels solid enough to withstand a bomb. It's designed for an intercooler and can even fit under the stock engine cover for that "sleeper" look. SSX was the first time I had seen Hymee's and Pettit's, and Pettit's looked like it was made in high school shop class next Hymee's. It seriously looks like he stole it off of a dragster.

oh yeah. I knew that. :) I guess we need to make a standard disclaimer in our sigs so that no one misunderstands anyone else.

And now, a haiku:

whines like a banshee
instant torque and horsepower
superchargers rule
:lol:

+1 mysql

There is not even one SC that makes more torque than even the base Greddy $3200 kit. The Turbo's all make torque just as early as any super charger. The only thing "better" about a SC is its easier to install.

You also can turn up the boost on a turbo with the turn of a knob or a setting in a electronic boost controller. You can set it for low boost and take a long drive or crank it up and use race fuel for drag strip.

Nothing wrong with SC's just Turbo's are more preferred if you want higher torque gains.