ProtoConVert

Here we go,

Can someone explain to me why it would be difficult to replace the variable intake system and the air cleaner box with a turbocharger connected to exhaust and intake?

Is the air cleaner box necessary? What does it do and how does it do it(nontrivial answer please)? Why does it look humongous?

Would turbocharging or sequentially turbocharging a Renesis reduce the rpm limit? By how much?

Will a Garrett hydrocharger work better than an exhaust driven turbo? How does a hydrocharger work? Does it provide relatively constant boost throught the whole rev range?

What is the great thing about the current Renesis intake system? How does the whole resonance intake thing work, er, why does intake have to vary and be precise in length? Will a turbo mod preclude this?




I get the sense that there is a sort of hesitancy to discuss turbocharging on this board. I only ask because, you must understand, if Mazda had more torque in this engine without losing anything else, there would quite simply be no other cars on the road.

Hercules

Buger?

wakeech

before i start, i must personally thank you for taking an intrest ProConVert... :D this is EXACTLY the kind of thing i've been looking forward to in the Tech Section...

well, the reason is that it's difficult to fabricate turbocharging systems. :D
it's no more difficult for the RENESIS than any other engine, it's just that no one can get their hands on one yet, and make a system. also (as i'll get to later) you have to junk all that wonderful stuff Mazda put in there to get a really drivable engine in the RENESIS, a tradeoff most people probably won't make.

yup, the air cleaner is necessary for a daily driven "real world" car, 'cause our air is dirty and dusty. particles that are pretty biggish (like a micron in diameter) are suspended in the air everywhere, and would be drawn into the engine if it were not for the filter. this stuff, if not burned and exhaled sticks in the oil, and gets pumped throughout the engine... although small, these particles are numerous, and can cause all sorts of troubles, which is why the air and oil is filtered so heavily, to keep the dangerous particles out, and keep the smaller ones within tolerances.

the air cleaner box on the RX-8 appears to have a large volume for what someone referred to as an "air resevoir" a while back. they said that it was for those moments you want to mash the throttle, and having a resevoir of slow-moving, already filtered air helps reduce delay to throttle inputs... or so i hear.

first off, the sequential system is a neat idea, but practically speaking it costs too much to implement over the benefits you get, especially with newer, lower lag turbos (ball bearings, ceramic components, etc.) which would work just as well in a single turbo configuration.

wow, tricky question. really, really tricky.
with going to a forced induction system, you are placing a far higher load (force) on every stress bearing component in the engine. this increased force per revolution translates into more torque, and thus more horsepower wherever your're getting that torque increase in the rpm band. the problem is that things are only so strong, and that rpm's put stress on the engine too; so, i could tentatively say "yes, it will reduce your redline rpm", but it depends on how much boost you're running, and how strong the engine is, which is why i'm tentative to answer: i don't know any of the structural tolerances on the RENESIS, but it has been said (by upper level Mazda engineers to the press) that it "was built to take boost". how much? i don't know, but maybe this means some amount of boost to redline? so you see, i can't say for certain. sorry.

i know nothing about these "hydrochargers"... some kind of water cooled supercharging system?? i've only seen those in drag cars (which is the only place they'd be any good)

omg, best for last, eh?? wow...
okay, i don't know all my theory on this, so smarter people please fill in the blanks that i'm sure will pepper this reply.

the great thing about this RENESIS intake system is that you have a system which can vary the length of the path air takes to get to the engine statically, as opposed to the "trombone" variable length system the R26B (787B engine) used, which (obviously) needs a lot of space to work in, and has moving bits to get gummed up.

Varying the length and diameter of the path air takes on its way ot the engine can help increase efficiency immensely. Varying the diameter is easy to imagine, as when there is a low volume of air being drawn in, a smaller diameter path will move that volume at a higher speed, and a larger diameter will flow it at a lower speed (note: the amount of air flowing is identical, just the velocity is different). i'm not an expert on how much cross-sectional area for what rate of flow, as it depends on things like how the shape of the path, and flow characteristics of the boundary layer (the fluid rubbing on the sides) change with velocity, etc., but there are optimums: bigger is not always better (that's the reason econo-cars have "narrow" exhaust systems: to cope optimally with low rates of exhaust flow)

Varying the length of the path has to do with exactly what you said before: resonance. The pressure change pulses of the ports opening and closing at some frequency (# of times per s) at some rate of flow (into the engine, and then the negative pulse back) ads up to a certain resonance inside the path to the engine. if the lenght of this path is just right, so i'm told, the negative pulses will be damped, while at the same time the postive inward pressure pulses will reach thier highest magnitude at the beginning of the path, increasing the efficiency with which the air is drawn in.

alright, that's all fine and dandy, what does it do? well, increasing the efficiency with which you inspire the air at the front end, and the efficiency with which you move it to the engine has a big effect on how efficient the engine is at filling the combustion chamber on the Intake stroke. Filling it efficiently increases the total amount of air in there, and along with more fuel, equals more bang. The beauty of the RENESIS system is that it readily adapts to optimize this efficiency through a wide range of rpms and throttle angles, to maximize torque at all times, making the car easier to drive.

The short answer with turboing the RENESIS is yes, you'd wanna just rip all that finesse-y crap outa there to make room (and a short path with less resistance to the engine) for your sledge hammer (the turbo). it doesn't necessarily preclude this, but there's really not much point to having both systems try to work in tandem, as your turbo setup you may be drawing up in your head would probably grossly overpower it, and would be better off without it. The deal with the turbo is that you're going to get more air into the engine than you ever could with the NA systme: also, i'm not EXACTLY sure on the theory behind it, but none fo the turbo side-intake port rotaries have had ports which extend upwards past the primary por... it may have something to do with those negative pressure pulses, or that the smaller port area translates into a higher flow velocity which would help with efficiency, or it's just that much more waterjacket to aborb heat, or something... i dunno why i threw that last bit on there... it's late, and i'm tired... but seriously, please keep asking good questions, especially ones i don't know the answers to and haven't thought of yet.

Sputnik

Simply because it is so complicated. It's difficult, not impossible. Certainly not. Are they even available yet? A hydracharger is very similar to a standard turbocharger. The difference is that in the standard turbocharger, the turbine spins the compressor via a shaft. In a hydracharger, the turbine pumps hydraulic fluid through hoses to spin the compressor. So while the turbine and compressor have to be located next to each other in a standard turbo, requiring some fancy plumbing sometimes, the hydracharger compressor can be located far away from the turbine, simplifying plumbing, and eliminating some other problems. As far as spoolup and whatnot, it still acts just like a normal turbo. To put it simply, the great thing is that it changes itself to offer the most efficient intake path possible at the different rpm ranges, but that is for a NA engine. Under boost, a turbo or SC would basically preclude the multiple intake path setup. Drivability off-throttle and under cruise could suffer slightly, but that's the case when you install an SC or TC anyway.

---jps

wakeech

*shrug* okay :o

that hydrocharger sounds cool... i like the idea of some of the comprimizes presented.