rotarygod

No it will not work. Not well enough to justify it. You do NOT want to overspin the blower. You will absolutely destroy your bearings. On top of that, you may as well run a blowtorch through your intake as well as the heat generated will be so hot that even a roots blower would seem like a refrigerator by comparison at that point. How is that a good thing? You really want to compensate for that with a larger intercooler? That's a bandaid solution at best. It would be far better to just use something other than a ghetto rigged centrifugal setup that is sized properly. You'll walk all over this all day every day. Do it properly. Don't rig it just for the sake of using a centrifugal. They are pure and simple crap superchargers for small high revving engines. It is physically impossible to change that fact. That's just the way it is.

You can not size it properly down low and then still have any advantage up top. The internal gearing is too extreme. You absolutely have to size it for max efficiency up top and take what it gives you. Centrifugals work one way and one way only in regards to sizing and gearing. If you don't want it to be efficient up top then you should lower your rev limit to account for this. If you try to size it for more flow at lower rpm's, you'll just run into surge issues. It won't work. The 2nd generation RX-7 used to have a supercharger kit for it that used a Paxton Novi 2000 supercharger. That is a supercharger that has the ability to flow enough air for hundreds and hundreds of horsepower yet on the RX-7 the best anyone could get was about 220 rwhp. That's it. It was in surge through the entire rpm range. The only way you can change that is to redesign the impeller. Waste of time.

Using what some Mustang owner ghetto rigged on his car isn't exactly a credible argument in this setup's favor. You may as well have told me that Billy Bob once raced his trailer home in a figure 8 destruction derby and therefore it's a fantastic setup to run at the track. There are far more terrible setups out there than there are good ones.

I understand what you are saying and in theory it would seem to be possible. It just isn't from any usable standpoint.

Red Devil

Ok, that's pretty funny.

As I wrote before, I wouldn't think of it myself, but again have seen it done to some degree of success. I saw the car drive around, and heard the blower going - that was about it. As far as it's practicality, using a pop-off valve like a wastegate was enough to convince me otherwise.

mac11

iTrader: (1)

I think we are all in agreement that it is not a wise idea. The fact remains that this type of setup is used and has worked before.

I also think if you are using a procharger, sizing it for production down low is stupid, so throw that out of the equation. Size it to deliver 60lbs on the top end and waste gate it down to 45-ish then spin the thing as fast as the bearings will reliably allow to make up for its low end deficiencies.

It's far from ideal and would never recommend it to anyone but it could be and has been done.

swiftrx8

Yeah I'm pretty sure there are a few turbo kits with higher output and a low price that run good. I like the kit but I don't want to pay $3-4K extra dollars for it to be in one pretty box. R&D, I just don't want to pay for that, they say over "100k" miles. I use to sell intakes and downpipes for RX7s and said the same ****, it wasn't true haha. I'd buy the kit for $5k!

rotarygod

No we aren't. It's called debating a topic. That's how people learn.

Which engineer do you know at Mazda? Give me a name and we'll ask him. Keep in mind several of us see the top rotary engineer every year. Turbos are not a waste of time on a rotary. Far from it. Rotaries respond very well to turbos. That's why they made turbo rotaries for over 20 years. If it was a waste of time, they'd have given up pretty quickly. The reason why they aren't using turbos now is twofold. The first is that they have advanced the engine enough without turbos to make the power they want. It doesn't mean it's the power level that everyone else wants of course. The second reason is that the 3rd generation RX-7 had an extremely unreliable track record. This was due to shortcuts in cooling design not to mention an overly complex twin turbo system that used 70+ vacuum lines and small turbos that spun up to 150,000 rpm at times. This was a design error. It had nothing to do with the fact that the engine itself does or does not like boost. It loves it but like any engine, if the entire system was designed like crap, reliability will suffer too. I assure you, they do know this.

Wonder no longer. Here's your answer! HIGH COMPRESSION! How many 10:1 compression 600hp 13B's do you see out there. Of the 600 hp engines you do see, what type of fuel are they running. NONE of them is running pump gas. How can you lower the compression on a Renesis since there are no other rotors that can be used?

I'm blown away that an intelligent person would think a centrifugal blower is a good match for a small high revving engine. It's just about the single WORST option out there in terms of average power. A turbo system designed to provide good boost at 9000 rpm would STILL make more power everywhere else in the powerband than a centrifugal supercharger does and it doesn't have to cost more to do it.

Nitrous is cheapest up front. In the longterm just remember that nitrous costs money. Air is free. Nitrous still needs to have some form of tuning but with the nitrous computers out there today I will agree that it doesn't have to be difficult to get more power with it. Show me a 600hp rotary running on nitrous!

The Renesis is a great engine in terms of high powerband. As a small engine it needs to be higher in the powerband. Good port timing and intake design have allowed it to have a wide powerband. Many new engines today have a flat torque curve now though due to good design. That's engine evolution. There's nothing wrong with wanting more power down low on a small engine. If you are going to install a boost device that makes more power up top, why not just install one that also makes more power down low? That's a pretty good use of investment if you ask me. If low end doesn't matter at all, why not just idle the engine at 5000 rpm? F1 engines idle higher than that and they don't care about low end either.


You aren't rubbing me the wrong way. Im just pointing out all of the flaws in your logic.

rotarygod

Just because it HAS worked before doesn't mean it worked good.

If you design it to supply 60 psi up top, it will surge down low. Now you have no efficiency advantage anywhere.

Yes it CAN be done. It can't be done well and this means there is zero advantage to using it over any other system design.

mac11

iTrader: (1)

Agreed.

But since when has something being the worst possible option stopped some people from using it anyway?

rotarygod

Very true!

Brettus

iTrader: (2)

If this kit was 1/2 the price I would buy it before I would get the Greddy turbo - even knowing that it has big shortcomings at low rpm .....
Why - its good quality ,it is easy to fit ,it will last ,my motor will last and it has the bling factor .

mysql101

if I sold you a chromed dog turd, you'd also buy that before buying the greddy. So that isn't saying much :P

swiftrx8

I agree! Very easy install, self-contained oil, reliable set-up, great mounting location, great power (top end), and it seems to be reliable on other applications. But the bottom line as said is just the price. I know other kits are better but this seems to save a lot of headaches, if it were $4-5K it would be a good buy!

mysql101

^ really.... how many of you REALLY think you'd be happy with something that makes less power than stock until 5,000 rpm, and no real power increase over a stock car till it's over 6,000 rpm?

Red Devil

For a real track junkie...not too much of an issue. Then again, I'm a budding track junkie and I wouldn't tolerate that since I drive the RX-8 every day.

Astral

only the 6psi kit makes less power than stock until 5K.

Brettus

iTrader: (2)

correct - where can I get one of those chromed dog turds ?

Brettus

iTrader: (2)

You miss the fact that there have been several reports from people who have actually driven it who could not notice any difference at all down low - not exactly a problem . I think most would agree that it's not the optimum solution - all I was saying was that at the right price it would be worth having for a lot of people .

rotarygod

Just for the sake of argument lets say we were running one at 6 psi. If in fact it doesn't make anymore power than stock (less) until 5000 rpm, how many people here daily drive and shift higher than that? I guarantee that it's very few. Now saying that, in normal everyday driving you are getting no benefit. In fact you are losing power and gas mileage. I know there are some that don't mind this and that's their choice. However if I were going to spend thousands of dollars on an upgrade for my car, I'd want something that I notice all the time. I want a forced induction kit that feels like I've always got a bigger motor under the hood. If my gas mileage is going to suffer, I want the powergain to show for it. A twin screw supercharger could kill this everywhere in the powerband and match it up top. I just don't see the argument for not using one as opposed to a centrifugal.

Brettus

iTrader: (2)

like I said - if it were cheap enough .... It's not cheap so I have agree with rg and mysql

Highway8

iTrader: (11)

Here is my 2 cents about the DNA/Mazdatrix procharger kit.
$8000 is a little high but the parts are expensive, a c-2 blower is $2500, a powermod is $800, injectors $300, headers $700, so $3700 for an intercooler piping and brackets and R&D. I would like to see the price come down by about $1000.

There seems to be alot of talk about the lack of low end power. I have talked to the DNA techs, procharger techs and procharger users. Everyone agrees that at 2psi+ the engine will make more power then the blower will steel. Also, under normal driving conditions, the procharger should not drasticly decrease fuel millage. The parasitic load on the procharger is very low and the boost increases the efficency of the engine and therfore yields almost no change in fuel economy. Under identical driving conditions, I would expect to see a 1 MPG maybe 2 MPG decrease which is consistant with all the mustang/camaro procharger users I have talked to.

I do not agree/trust with the dyno comparision charts shown. If you look at the 303HP 10PSI chart on the mazdatrix and dna websites it shows 100HP at 4K rpm not 4700 like the dyno comparision thread. Also the dyno charts were with a australian RX8 which makes less power stock, I am not sure if it matters once a vehicle is boosted but I am waiting for mazdatrix to make there own dyno runs.

I think you could safely run this kit at 14-16PSI. It has been doen with turbo's and the procharger runs much cooler so it should not be a problem. If you ran 16 PSI I think this kit would start making serious power at 3500-4000 RPM at probably get to 375-400HP.

Ultimately it comes down to performance and reliability. I think everyone agrees that the kit should be reliable but before we can judge the kit on performance we need to see dyno charts from mazdatrix. The charts they show on the website are from DNA and only up to 10PSI.

I think that this kit has its pros and cons. I am waiting for all the facts before I make up my mind.

mac11

iTrader: (1)

The wholesale cost of a procharger is dirt cheap. Compare it to a twin screw, they are not even playing the same game let alone in the same ballpark.

You apparently don't know how a centrifugal blower works.




16 psi....and 400whp. yea, ok.

do you know what the static compression of this motor is?
have you looked at the compressor maps for this blower compared to the lyshom units?
Have you seen what kind of parasytic drag is created by spinning this blower at that speed?


obviously not.


There is a reason for that. And its the same reason there are no other kits on the markt that are going to go beyond 12psi without auxiliary injection.

rotarenvy

the more boost you run at the red-line with a centrifugal the better. it will improve the lower rpm directly. although they are defiantly better with low rpm range cars. you can always gear a centrifugal SC to hit the same max boost lower in the rpm range 8-8.5k and use another rev limit. this would improve the boost threshold.

the over-spinning argument is crap. fit a bigger SC that can handle the flow/PR at the rpm.

over-heat the air? only if you have chosen the wrong SC and your pushing it off the map.

isn't surge a light throttle issue? and moving the throttle body is the solution?

Highway8

iTrader: (11)

The c-2 has a max out-put of 1100CFM and 24PSI, correct me if I am wrong but that should be more then enough for the RX8.

Can an turbo RX8 handle 12PSI? If so, a procharger can run 14PSI-16PSI (No where near max PSI) because the inlet temp is much cooler.

I do not think you are going to over spin a c-2 at 14-16PSI the question is what other upgrades must you do to handle the power. Can someone explain why they think a c-2 is going to produce too much heat at 14-16 PSI? It will still be much cooler then a turbo at 12PSI.

Who actualy know what the parasytic drag of a c-2 compressor is? I have tried to find the statistics but the best I can come up with is that a centrifical supercharger has less drag then positive displacement supercharger.

I will say it again, Ultimately it comes down to performance and reliability. You must look at what you want your car to do. For me, I want more power, but if I can not take my car to the track because it overheats then it is not worth it for me. The astralians have been road racing there DNA equiped RX8's and I have heard about no problems, that is why this kit appeals to me.

rotarygod

I still don't think the overspinning thing is setting in. If you spin it to provide good boost down low, due to the internal gearing and the rate at which boost rises with rpm (it isn't linear), you'll be WAY high in boost up top. Then to limit the amount of boost you want to bleed off pressure to bring it back down to a lower level? If you spin it to give 15 psi of boost at max rpm but then bleed off pressure to hold boost at lets say 8 psi, you do have 8 psi but at the air temperature of 15 psi out of the blower. This is far less efficient than 8 psi out of the blower without bleeding it off. The efficiency would be bad enough that now you may as well use a roots blower with no intercooler. Why would you do that? Then you want to compensate for this with better intercooling? Come on! How about better intercooling with a properly designed system.

I guarantee that anyone that does this type of setup, I can beat with almost any other alternative at less boost. Now why is that a good idea again? Get over the centrifugal crap. They only belong on large engines that have lower redlines. That's what they match well to. A turbo can be made to match up with any engine and have a nice powerband so can other forms of supercharging. This particular type is just terrible for a small high revving engine. Don't get caught up on peak numbers on a dyno. That's great for selling product but not too useful in the real world.

rotarenvy

I agree the bleeding off of boost is a band-aid fix. it will heat the air and would get to a point very quickly where it isn't worth the power loss at high rpm.

still there is an argument for a centrifugal set-up even if it isn't the same as a PD sc or turbo.

A centrifugal SC will deliver more power up to than a PD SC. just look at the peitit. great down low but pathetic up top.

it will do the same as a turbo up top if not better and can rev to the limit not a cut back level like the turbo kits.

it's delivery will be smooth and predictable akin to the mazda engineering ideals of why they left the rx-8 NA in the first place.

while the DNA sc may not be bang for your buck a centrifugal sc isn't so bad if you understand what you will get. don't expect the world but you will get a motor that feels more powerful than std at mid to high revs.

rotarygod

Don't judge a pd blower solely on Petit's kit. I have my opinion of it but needless to say it's not the be all end of of PD supercharger kits and wasn't meant to be. My money would say the DNA will have nothing on Hymee's when it gets done. If it does it'll only be on the extreme top end right before the shift point which would be irrelevant as it would be staring at tail lights long before then anyways. A centrifugal has NO business being on a small high revving engine when there is another alternative available. DNA couldn't convince me of it and neither could a ride in one. I'd basically say that was fun but next time use something better and I'd make no reservations of telling that to the creator. That's the whole truth and nothing but the truth. A centrifugal can never get cheap enough (free) to justify it's existence on a small high revving engine. IF you could somehow find a race series that only allowed centrifugal supercahrgers and nothing else, then it would be viable.