rotarynews.com

Ok, being an engineer by training (all be it, Software engineer, but I had to take EE and ME courses too) , I've been doing some sketches of how and where a supercharger kit would be.

My conclusion is almost the entire intake system will have to be redone, from the block to the throttle bodies. Nothing like the cadmin kit could be done, because of space requirements.

I think the 3 intake tracts would need to be removed, the super charger placed between the injectors and the air sensor.

Attached a rough image of what I think a Cadmen -style supercharger setup would look like on the FE.

Red blocks are injectors, and this sketch isn't in 3dimensions, so the supercharger could sit closer and further down than this sketch indicates. A single large intake tube would be connected to the top of the super charger , and all vacuum could be drawn from there, At the end of that tube would be the modified Air flow meter. I would suspect a computer mod would needed to be done, maybe even swapping it out for a Haltech or otehr aftermarket ECU.


Now, again, this is just my back-of-the-napkin engineering going on... those 2/3 intake tracks have me worried about aftermarket supercharger kits, however.

Sputnik

I would think so too, and normally, a roots type (if that is what you are envisioning) is also usually downstream of the throttlebody too.

---jps

Schneegz

Is anyone else worried that a supercharger might throw off the car's inherent weight balance a little?

One of the beauties of the Renesis is that its diminutive size allowed the engineers to place it way back and way down inside the car, giving the car a more centralized weight distribution and thus a lower moment of yaw inertia. Bolting a supercharger on top of the engine would raise its (the engine's) center of gravity. Would this change be noticeable at all?

Also, would it actually be better to bolt a supercharger (along with more free-flowing exhaust) onto the 210hp version of the Renesis? If I have my facts straight, the 210hp version does not have the variable intake system, right? And you would probably have to remove all that stuff to bolt on a supercharger, right? So why not start out with a less expensive car that doesn't come with all the variable intake goodies you have to get rid of? Does the 210hp version come with a 6-speed tranny, or is that only reserved for the 250hp version?

I'm not very knowledgeable about superchargers, but I am a mechanical engineering student, so If you have answers to the above questions, go ahead and lay the technical stuff on me. I can handle it.

Sputnik

Another advantage to putting an SC on the 210 HP version is that since it has a lower rev limit, the SC setup will not have to be compromised as much to accomodate the relatively large rpm range.

As far as weight offset, I don't think that a simple setup would be a big issue, personally. For example, the Jackson Racing SC kit for the Miata weighs some 25 lbs, IIRC. Owners of that kit report that it does not affect balance at all (and it's a lighter car). Don't forget, you will have more of a weight shift than that between a full and a 1/4 tank of fuel.

Normally, a properly setup turbo kit weighs a bit more (turbo, manifold, IC, BOV, etc. etc.).

---jps

rotarynews.com

Well, a 4 port was used for Turbo2's while the 6 port was used for N/A 2nd gen FC RX-7s

I could imagine a larger 4port design for supercharged/boosted RENESIS's from the factory. But for the aftermarket, a solution has to be found for the 6 port, as that's what the majority will be in the US, at least.

RedRotaryRocket

As far as the aftermarket is concerned, wouldn't it be a big disadvantage to make a kit for the 210 HP version because of the auto tranny? Am I smoking crack, or do I remember reading somewhere that the auto tranny is not up to much more power than the stock 210?

zoom44

no i think you have it the wrong way around. the torque converter couldn't handle the 9000rpm. so the stuck a lower rev limiter on it. less revs=less hp

CraziFuzzy

and with less revs comes the need for smaller port area (less volumetric flow requirements) thus only 2 ports/rotor vice 3 in the 250. I thing the higher possible flow rates in the 6 port version will outweigh the benefits of greater simplicity of SC'ing the 4 port engine.

RedRotaryRocket

Oh, that's right. I remember now....then to answer my own question, I must be smoking crack

zoom44

just remember to put it down once in awhile and you'll be ok

N20SA22C

Why a roots type blower? With all that room in the front (when I pull out stock air box & emmisions stuff), a Vortech "S" type will flow better, and is more thermally efficent than a roots blower. Plus you can add a nice Front mount I/C and raise your boost threshold. I dont know as far as weight between the two units, but just use the bathroom & dont eat before you go to the track and you'll save 1/2 that.

Kyle Lancaster--Double Agent Salesman

CraziFuzzy

A roots type blower would be ideal because it is a possitive displacement pump. It would provide good boost at all RPM's. The Vortech unit is a Centrifugal blower, and it will provide almost no boost until the RPM's get up there. The place where the RENESIS could use the most help is in the low end, if for nothing else, to just improve drivability. That is why we are talking about a Roots... The advantage to a centrifugal, is they are much simpler to build, and are therefore cheaper, and you take less of a bite in efficiency, because, like I already stated, at low RPM's (read, cruising) it is not really doing anything. Newer Roots blowers get around this disadvantage by having a vaccuum actuated bypass valve, so when cruising, they too are doing nothing.

Sputnik

With an engine with a higher rev limit, a centrifugal SC actually hurts performance at lower rpms. At that's regardless of whether you are cruising or at WOT. Check out dyno results of centrifugal SCs on an S2000, and you'll see what I mean (make sure you know what you're looking at as far as other peformance mods too).

And you can install an IC with a roots type SC. You just plumb it similarly to the centrifugal SC.

---jps

MrWigggles

I think an Eaton 4th generation:



can fit here:

MrWigggles

The dimensions are here:



Please note that the length of the neck can have a wide range.

-Mr. Wigggles

Ps. you can get a clean engine bay pick from: http://www.mazdausa.com/MusaWeb/rx8/..._images_32.jpg

NashuaCLS

How about the piping of the SC...? How are going to route the in-out tubes?

MWG

I think a eaton supercharger will work if you change the intake manfold or with a Paton centfuigal supercharger will work with the stock manfold. I don't quite know where to put a a eaton super charger would god perfer it to a centfuigal because of the nstant pressure and then use a bypass value like it is used by Jackson racing.

Farsyde

it seems like b/c of the cramped engine compartment in the rear of the engine bay, would a turbo setup be "easier" to install since it doesnt need to tap into the engine belts anywhere it could be mounted farther toward the front of the negine bay, within reason of course.

CraziFuzzy

A turbo would not give us the low end torque that we are trying to achieve with the SC. There should be enough room back there for the blower.

Sputnik

That's a fallacy. There are differences in off-throttle response time, etc., but those depend on which turbo setup you decide to go with. If you go with a huge turbo for peak power, then it will take all day to spool up, and will be frustrating in street driving (and some forms of racing, for that matter). But if you size your turbo correctly, it will offer good low-end torque and quicker response than you'd expect.

Add to that the fact that you will not get as much low-rpm boost with an SC on the higher redline Renesis than you would with an engine that has say, a 6k redline, and the SC loses some of it's advantange. In the case of a centrifugal SC, performance at lower rpms will actually be worse.

At that point, it becomes a personal choice. How much power do you want to give up for throttle response (same question goes for turbo selection)? How much power do you want to give up for cost and installation ease? For what some people want, an SC will be a clearly better choice than a turbo, while for others, a turbo will run circles around an SC.

---jps

Farsyde

i like the ease of tunability of a turbo. I like having the option of adjusting the boost anytime i want without having to spend hours switching pulleys. I know it can be a much more expensive choice but nothing fun comes cheap.

Anyhow, this topic has been much argued before so i say base your choice on the sound! :D j/k, but seriously

AbusiveWombat

Jackson Racing has had very good results with the VTEC engines in the Honda and Acura line up. They use an Eaton SC. The Prelude kit gets 40% more torque across the entire RPMs. I'm sure they'll come out with an RX-8 kit. It seems ideal for what the RX-8 is lacking and it's from a well respected company.

They've got Dyno charts on their web site:
http://www.jacksonracing.com

CraziFuzzy

Jackson, while being very good at the design of they're systems, are NOT to great with customer service / relations. They make a very good SC kit using the Eaton M45 for the Ford 2.0L Zetec found in the Focus, but over many numerous emails and phone calls, they could not tell me why it wouldn't fit on a zx2. The only answer i was ever able to recieve from them was that it will only fit on the focus. Oddly enough, I have seen a couple zx2's with Eaton M45's AND intercoolers squeezed behind the Zetec. Even if it would take some modifications to squeeze it in there, I would have been willing to shell out the cash for their kit. But they're lack of information at the sales level really turned me off the idea.

gazita123

I got to talk with one of the Mazda tech guys at the Rev It Up event here in SF. He had some part with the development of the RX-8 and is up on who is doing what with performance upgrades.

One really interesting thing that he mentioned is that MazdaSpeed is developing a hydraulic supercharger. This would get around the mechanical limitations of the traditional pulley driven setups and would allow for a lot of programmability of the boost to match the need.

I know this is a completely new kind of system, but it really wouldn't be that difficult to put one together from off the shelf components. You can utilize a traditional blower design, but simply run it off of a hydraulic motor. You can get hydraulic pumps for almost any need, and the stuff in the middle is common enough.

CraziFuzzy

Honestly, the hardest part of designing a system is going to be the intake piping. The stock system is so complex, and with 6 intake ports, that are designed to kick in at different rev's, it will take a LOT of R&D to design a replacement system. The advantage of going ot the blower, is that it will keep the flat torque curve, but only if you can keep the programatically modified intake. Fortunately, with a positive pressure in the header, it makes tuned lengths less important, so I'm thinking that a simple air-box plenum with some butterfly valves for the individual ports will be acceptable... of course, it is starting to look like I will not end up with the resources / time to work on this... Some changes at work, so to speak... :/