zoom44

it means someone thought this was useful enough info to keep it stuck at the top of the page. it wont get buried by new threads until it is "unstickied". i dont start many of those

zoom44

agreed on the sucking water myth. but i did give rotarygod the chance at saying "Helmholtz" by defering to him when mentioning resonance tuning. apparently he decided NOT to take advantage of the oppurtunity, so the wrath of wakeech be upon him

wakeech

rotarygod

I do have a friend that sucked in water in her Z28 from a cold air intake. She was also dumb enough to follow a truck through a foot and a half deep of flood water.

I started the Helmholtz thread a year ago. It's funny how it still gets mentioned. I don't really need to post anymore on it. It would be a redundant book.

MazdaManiac

iTrader: (3)

If Hermann only knew we would use his math for something other than accoustics...

rotarygod

It is still dealing with acoustics.

RX4+30Years=RX8

I did it in a 94 T-bird. Careless, nope, it was a flash flood that came up to just below the top of the hood in less than 30 seconds as I was driving at about 30 mph down a street that normally does not flood. Sucked plenty of water in. Result was some nicely bent rods.

It does happen.

rotarygod

If the water level gets up to the hood, it doesn't matter where the air filter is at that point. You're still getting flooded. What I am referring to is people who have low filters who are afraid that a little splash from rain water or the ditch is going to kill their engine. It isn't. As I said earlier, you have to drive through a flood to hurt it. This you have proved.

RX4+30Years=RX8

To that I can definitly agree. A little splash from rain or from running over a puddle in the road will not kill the engine.

From personal experience, it takes a LOT of water. A good way to tell if there is enough water to cause a problem is to check the seat of your pants. If they are wet, you may have a problem.

Sure was a good thing that a fire engine came up behind me and pushed me to higher ground, that water was moving fast.

Japan8

Now I get to say it.. :D I posted about this recently in another thread. In the review of the changes made on the Mazdaspeed RX-8, changes to the size of the VFAD ducts is one. Mazda's goal with the MS RX-8 wasn't to tune for ultimate horsepower. They were tuning for more "reliable" power... power on tap easily throughout the rev range. I suppose another way to say it is an increase in driveablility.

So what's my suggestion for RB and anyone else for an intake? Work on the VFAD diameter and length. If you want to look cool too... have that feed into a heat sheilded box (not just aluminum box, but add insulation/sound deadening material) with a cone filter. I think this will achieve the goal of a fair power increase without the crazy noise and idling problems of the K&N Typhoon.

Indeed. I hate math, so I won't be doing those calculations.

BTW, GReddy claims that their intake is resonance tuned to increase mid-range power. We'll see how that is once people can get their hands on it and give it a whirl.

Nemesis8

iTrader: (3)

I have the SR Intake, and I wonder if it's length and diameter were calculated to match this??

shelleys_man_06

What effect would forced induction have on S-DAIS? I am assuming you would have to change the time at which each valve opens. Since the valves are vacuum-regulated, wouldn't they adjust to the pressure rise in the intake stream, or is the valve actuation independent of pressure changes? I think Mazda chose vacuums because electronics would make the car unaffordale. Is it possible to switch from vacuum modulation to eletronic control, such as using a stand-alone EMS to do so? After all of the thinking I've been doing about forced induction, I forgot about the intake tract :o.

rotarygod

I would set it up so that under boost, all valves are open. When not under boost, it would work normally. The VFAD duct would no longer be needed. This would be very easy to setup. The hard part is setting up an ecu to switch maps based on boost or no boost.

wakeech

that sounds like an even more costly endeavor than having a new manifold fabbed up for your turbo system (which would then give you more flexibility in the design of the system, and better boosted performance).

all you gotta worry about actuating is the tertiary port, and just have six runners at a tuned length to the engine from one plenum designed to resonate at X rpm.
i dunno, instead of complecating things even more, i move to simplify things a lot.

wakeech

that sounds like an even more costly endeavor than having a new manifold fabbed up for your turbo system (which would then give you more flexibility in the design of the system, and better boosted performance).

all you gotta worry about actuating is the tertiary port, and just have six runners at a tuned length (you could choose to go either with a comprimise setup where the runner to each port resonates at a different velocity and has a different diameter, or the full-out performance setup where they all resonate at one rpm and are of a larger diameter) to the engine from one plenum designed to resonate at X rpm.
i dunno, instead of complecating things even more, i move to simplify things a lot.

shelleys_man_06

wakeech, rotarygod, I found some of your old threads about making power with the RENESIS. Why did they die off?

Mag66

Zoom44, (or any of the other more 'techie minded' people here)

Is the data you gave at the very beginning of this thread only applicable to the MT or does it apply to the AT too? Or, did they change at what rpm things occur to take into account the lower available rpm to the AT owner?

(Sorry if this is both a dumb and obvious question... but I'm curious given I own both an MT and AT and am trying to learn as much as I can about the tech side of these cars..)

shelleys_man_06

I think that diagram only applies to the high-power (6 M/T in the United States) RENESIS. I do not think that the AT is VFAD-equipped.

rotarygod had a thread a while back explaining the 4-port RENESIS. Try a search . It might help solve your question.

rotarygod

Yep, the auto does not have the VFAD duct or the tertiary ports. the rest it does have. The lengths of the intake runners is different though and even the VFAD duct is longer. The principles are the same between both engines. The auto just has less of everything.

Japan8

Shelleys_man_06 has got it right. The A/T has the 4 port engine instead of the 6 port engine. The two engines are quite different with the 4 port motor lacking auxiliary ports and the port timing is different. To simplify the explanation that RG gave in another thread... the 4 port motor simply cannot "breathe" as well as the 6 port motor. However, as RG has pointed out... the intake system is still a resonance tuned system... just one built to flow less.

Wakeech has often said that the 4 port motor is a better FI candidate than the 6 port. RG has argued the opposite. The Renesis engine with the side port "can be set to less than 0 overlap" according to Seiji Tashima, Mazda lead rotary engineer.was built essentially without port overlap (if I understand my JP article correctly). This is how it make better emissions. This also has an effect upon how good it is for FI. RG would need to jump in to explain this better, but apparantly some port overlap is good for turbo applications.

zoom44

wow i got included with the "techie minded" people here!! not sarcasm here- that is a great honor for me to be included in that group. thank you :o

wakeech

'cause there ain't so many people interested in discussing these things.

IKnowNot'ing

EXCELLENT summary, thanks. Can you however explain where does the 122,74 mph optimal speed for intake air come from?


Re some other posts in this thread : water ingestion through the intake pipe (spout) is definitely not an urban myth. The intake pipe had to be redesign on the Escape / Tribute program before production due to this issue of water ingestion!
Now, it means that car manufacturers carefully check their intake systems against this issue and it should not be an issue any more on your production vehicle.

shelleys_man_06

IKN, I believe if the velocity exceeds 122.74 mph, the flow losses through the intake will dramatically increase. Why *shrugs shoulders* ? If I am wrong, which in most cases I am , I am sure rotarygod would be more than happy to make any corrections, because I am starting to wonder the same.

wakeech

this may have been a mathematically derived number (backwards from all the known meausurements), but theoretically it would be a speed where at maximum engine speed (WOT, of course) the comprimise was such that velocity could still be maintained at lower engine speeds (where marginal efficiency loss at some point in the higher end equals the marginal efficiency loss at some point in the lower range). the "terminal velocity" would change based on the shape of the path to the engine, and the surface over which all that air was travelling, not to mention the kind of comprimise you're trying to strike in the design.

i'm not sure how he came up with that number, though, as it's far less than half the speed of sound (some arbitrary number i read once on an F1 tech forum).