rotarygod

Hopefully this thread won't get closed after over 1400 posts just because of one closed minded persons attitude.

Ajax

We'd probably need more than a weekend to do what needs to be done.. how are those exhaust runners coming?

Omicron

Ug. This was not intended to be a stupid question, nor get all the forum's "brainiacs" rallying together to effectively tell me how stupid the question is. Jeez, we normally agree with each other.

My POINT is that the Greddy turbo already on the market. There will soon be several others both turbo and supercharger on the market too. NO we don't have them to compare, this is all theoretical! The thing is a lot of people will wonder, since HP ratings will be all over the place, which kit is going to perform better, regardless of HP claims. I thought this would be an interesting topic.

BUT NEVER MIND. Jeesh. Think I'll go buy another RX-8 so I can just solve this damn problem myself.

Oh, and BTW, everyone back the hell off on Rotoman, he's trying to ask the same question as me.

<Omi goes away pissed>

Richard Paul

iTrader: (5)

Omicron is the man of the day. Keep going rotoman, You guys are helping catch up with Philodox. He has a hell of a lead, but if we all pull together we can retake the poll.

guy321

Should also add, the SC's are twin screw, or axial flow. Not Roots or centrifugal.

rotarygod

Omi: we aren't trying to **** you off. I guess we failed in that department. We really just can't answer that question accurately.

My personal take on the Greddy kit is that it is a small performance upgrade but far from optimal. The turbo is too small. This most likely translates into great low end power but will fall off at higher rpms. Greddy even admits that power falls off at higher rpm's. This is where the Renesis really starts to shine. I see the Greddy kit being a nice upgrade for the person who feels this car has no low end power but I don't see it as the right kit for someone who really wants a much faster car.

The Pettit kit I also see as being designed with the same purpose. They are using a small twin screw supercharger. This will do fine at the low boost levels they want and will have great all around power compared to stock. This is another system that I would consider good for those who complain the Renesis lacks low end power but isn't concerned with how ultimately fast their car is.

Hymee seems to want a nice drivable system that provides a nice overall increase in drivability but also the potential to make some great power in the future if everything is is done properly. From a race standpoint vs the other 2 systems, I'd give it to Hymee.

Richard is designing a system that is a nice boost in power reflective of the engine's current power curve. It should really just feel like a larger Renesis everywhere. The extreme low end power may be lower than some of the other systems but the mid to top end should be quite nice. Power increase should feel very linear as rpm's rise vs a turbo which will start to surge you roward once it spools up or vs a supercharger which will feel like you installed a V8 under the hood when off idle. This supercharger I don't predict to be the slowest of the group nor do I consider it to be the fastest. It will probably settle in somewhere in the middle. How much could be ultimately had out of it will really be dependent on how much extra airflow capability Richard has efficiently left room for above it's intended use.

The SSR turbo kit is a kit that is designed totally differently from the Greddy kit. It should have great mid to high rpm power and be easily upgradable in the future.

Ultimately out of the currently available systems and their intended design uses, I would actually give the win in terms of total potential to the SSR kit only because it would be the easiest to upgrade in the future. It uses a generic T-04 based turbo that can easily be upgraded. If all of the systems hitting the market are hitting similar goals, they should be really close in the performance department. Which ones will have the greatest future potential for upgrade is the real question.

Rotoman is not trying to get the same question answered. He is of the opinion that a turob will always win based on what a mechanic said. Based on my above very limited analysis he'll probably be very happy.

Personally I already own a turbo but am awaiting for the axial flow unit so I can convert.

guy321

I have the same question. I wouldn't be disheartened by thier answers though. I think the fact that they say "It depends" is a very good sign.

Yes, rotoman gave a definite answer, which would be nice to hear. Except that it came off very biased and uninformed. I've been reading other forums for other cars where FI is discussed, and you see countless threads of people saying turbo is always better. Usually these answers are typed by what looks like a 3 year old, and thier "facts" are just plain wrong. I apologize to rotorman for jumping to conclusions. However, you (and I) were looking for a factual discussion, not "so and so said.."

The "it depends" answer is a good sign because it IS possible (theoretically) that one of the SC setups is as quick as the turbo.

Now, back to checking my kitty for male bits.

Nemesis8

iTrader: (3)

I don't post in this thread often, but was there a reason Mazda North American "supercharged" their project car?? Just curious.

guy321

Hope you don't mind me asking this here Richard, but it increases the post count.. and RG mentioned it above..

I keep seeing reference to Pettit using a smaller autorotor SC than Hyme. I didn't read any specs anywhere on what one they are using, so I assume some of you guys saw it at 7 stock? Well, weren't they going to do a low and high(er) boost version? Could they not be using the same autorotor SC for that version? I've tried e-mailing them months ago with no reply =)

Just curious.

To stay on topic, any updates, Richard?

rotarygod

Yep saw it firsthand at Sevenstock. The preliminary info they had on low boost and high boost really wasn't that different. It would more accurately be termed as low boost and less boost. 3-4 psi vs 6-7 psi. They could use the same supercharger for both.

Ajax

I'm sure there was and I bet it was two fold.
First I'd say that the exhaust flow on the renesis is not nearly that of the 13B-REW because of the side ports. The exhaust gasses coming out of the car are just not coming as fast and as we saw at 7stock, there's major room for improvement in the flow out of those ports. As we've seen, the exhaust gasses coming out of those side ports are still pretty fast.

Second, I'd say they did it because of the reputation that the 3rd gen had with problematic turbos. No, I'm not saying that all turbos in all 3rd gens had problems or that the turbos were the main problem of the 3rd gen (cooling was the problem) but people tend to play that off as what made the 3rd gen an unreliable car. Maybe mazda was trying to avoid producing a turbo rotary because they thought it wouldnt sell (in the US) because of that reputation.

Or maybe it was just because a supercharged vehicle was just less complicated and less expensive to build than a turbocharged vehicle.

They could've had any number of reasons but those are my guesses.

guy321

Ahh thanks! Well they could go the Starbucks route and have large and Venti .. High power and super power! I asked the diff before via email and hadn't got a reply. I suppose one is intercooled and one isn't :/

ctupton

Well on Mustangs here is what I've learned.. Turbo's are usually the fastest but they also grenade the engine the fastest... the twin screw's were almost as fast but are way more reliable... the centrifugal are sometimes reliable, and the roots are probably the most reliable, but as we all know is just getting to be too old of technology to have much improvement. now RP's intrigues me, because up until this site I'd never heard of his, but everything I'm hearing (reading) has me drooling... I personally predict (and well this is based off of comparing rx-8's to mustangs...I know not good) that both RP and Hymee's would be better than the greddy turbo as far as performance goes... if nothing else the cooler intake charge of both sc's would be a big factor.

Nemesis8

iTrader: (3)

So, with Richard's supercharger, I could do a mild street port, clean up the runners, install a header, and then supercharge this engine - That is my goal. RP does your supercharger retain the stock OEM intake box? Or have you not layed out the plumbing yet?

guy321

Just as a re-cap. Omicron's question was not which form of FI would produce the most increase in HP/power. But if Axial flow, or twin screw supercharging that dyno'd a lower total HP gain could actually be faster than a turbo that is rated slightly (10 - 15hp) because of the way power is applied over the entire RPM range.

Omicron

Ok guys, I feel better now. Thanks. I was hungry, tired and grumpy. Now I'm just tired. :D

Ajax

The answer to that question is yes.

RX8-TX

Not entirely. Don't forget that you want to integrate only the operating range :p

Ajax

blah.. give me a break here :b

RX8-TX

.... don't get me started with Fourier to analyze harmonics.....jeez! highschool...j/k

BTW, RP, how are we doing on the post count? We still have 6 pages to surpass Jon's thread.

Ajax

ok then.. how bout we discuss the resonance frequencies of RLC circuit designs and class c amplifier design?

would that be more fun for you? :b

RX8-TX

Ah....good ol' electronics. But RLC doesn't sound all that familiar (running a search on Google gave me Radio Link Control: what kind of?) Anything too high-tech is over my head ( highschool was a long time ago). Why don't we talk about discrete filters (LP, HP, MP, BP...) or even better, how to relate signal analysis to exhaust harmonic tuning? (that'd be more inline with the subject)

Am I becoming a postwh#$#?

Ajax

RLC = resistor inductor capacitor (band pass/ band reject filters)
lol..

like this: voltage source in series r in series with l in parrallel with c (r - (L || c))

so your s domain function where s = jw is something like this (R/((1/sL) + sc))/(R+((1/sL) + sc))

Now solve for your poles and zeroes, make your bode plot and calculate the resonance frequency of the circuit :b

Richard Paul

iTrader: (5)

Hey, hey, it's engines, I don't care if you put them in cars, planes or boats. But it's always about the engines. We don't do amplifiers and diodes or capasitors.
We don't do flowers or clothes. This ain't no girlie man thread.

As to the intake I don't know what you refer to. The manifold or the aircleaner?
At the moment I think we need some of the real estate that the air box now has.
Again we haven't even desided if the air will go in the back or front of the SC. It will depend on how it packages. We have the option of changing this althogh it takes a full redesign of the parts.

Since we are not in production yet it may change. All the prototypes have been axial rear inlet. This is the way I like it but most of the blowers I built in the past have been the other way 'round.

Rotarygod is worried thar I wouldn't leave him any headroom in the design. Now would I do that to you? I can't be sure of covering the range if there isn't something left. I am not going to max out every little bit that is in there right away. No matter what I do someone is going to force the thing to go faster. Now I can tell you where the theoretical point of going Mach is. I can design it so it runs well below it, yet there is going to be that one guy and you know who you are. That is going ballistic with it. I have no idea what will happen if you do.
I know it will not flow as much air and keep pushing less as more surfaces go sonic. It might get "blade stalls" little storms that stay in the blades and stop flow.

You might get one big bang when the air just stops. The damage may be limited to the blower but I doubt it. Supersonic waves are very strong, witness sonic booms. You don't have to actually go sonic to get some points on the blade to be supersonic. This is because air is going different speeds at different points on a wing. Remember how some WWll fighter pilots were having trouble controling thier planes when they got into high speed dives. Say a P-51 pilot go into a war emegency situation and his only way out is a dive at full power. He is climing on 500MPH plus. The wave pressure is already starting to move back on his control surfaces. When they get to thhe control surfavce he can't move them with his manual controls. Remember there was no power assist.

So are there little pockets around radius or such that go sonic before you are actuall sonic, yes there are. So use care, when you get ther you will have gone to far. Also the speed of sound is based on temp. It is slower when cooler. A car on the ground has to go faster then a plane at 30,000 ft to break the sound barrier.

Ok gotta go check my E mails now. You guys keep up the good fight.

Ajax

you cant really call electronics girlie man stuff.. 90ma will kill the average human being.. that's nothing.. and w/o electronics your modern engine would be worthless..

anyway :b

back on topic.