guitarjunkie28

that's one of the reasons the porting was so conservative the first time around. i'm getting a little more ambitious for this one, but it's still on the safe side.

and i'm always reading as much as possible on the subject...i've had really good results with the stuff i have done, and i expect them to keep gettign better and better.

Zaku-8

Let me throw an idea out there just to see the holes in it.

I'm pretty sure I get why its not a good idea to totally remove the dividing sleeve. But suppose you did, and made the center shared exhaust port as free flowing as possible, using a flowbench and only one rotor (even though during operation the port is open to both chambers).

So at this point theres the problem with exhaust gasses blasting the other rotor chamber which is bad. However, would it work if there were some way to close off the interface between the port and chamber B when chamber A's exhaust is passing through the port?

I'm thinking a rotating drum consisting of a cylindrical or conical shell with appropriately timed gaps, which turns because its connected by a shaft drilled through the center intermediate housing and is connected by some appropriate right-angle gear to the e-shaft.

Or, suppose there are doors millimeters away from the chamber exhaust port that open and close with some sort of pneumatics maybe.

Please explain if this would or wouldnt work.

guitarjunkie28

i think it would work, but the cost-to-benefit ratio and reliability wouldn't be very good.
we may have more luck by just making the exhaust ports on the front and rear housings a lot larger than the ones in the intermediate--forcing most of the exhaust out the sides, instead of the center. there's virtually NO room to work with there anyway.

as soon as i get a pile of cash, i'll buy some extra front and rear irons and do some very serious mods to the ports, runners and water jackets. then i'll probably build an engine with only exhaust porting--no intake whatsoever, just to see the max benefit that can be had from exhaust porting alone.

rotarygod

You've got to remember that anything mechanical in the exhaust system has to withstand very high heat. If it's in the housing itself, it'll see damn near 2000 degrees. I don't think a valve will stand up to that. Leave the divider there. At some point after I get my Renesis, I am going to work on a new center sleeve that you just replace the stock one with. This will keep the ports completely divided just like the intake side.

Japan8

That's what I thought too (you beat me to the post).

What i want to know is what kind of cat-back is RG developing...

guitarjunkie28

i wanna see a back pressure sensative muffler with some kind of internal flapper valve.

rotarygod

That is an option on my proposed design but I have to test the functionality of the concept first. If it works I'll complicate it later.

Japan8: The RX-8 mufflers I am building are 8" diameter by 13" long. There are 2 of them. The are oriented very differently than the current systems and the sound deadening principle is different. I still fear it will be too loud though. We'll see. Like I've said, if it doesn't work out, I won't build them.

guitarjunkie28

out of curiosity, would higher backpressure in the low rpm range possibly help out the fuel economy of the hgher overlap engines?

i'd think more pressure would make it harder for the intake charge to escape through the exhaust, and maybe not waste as much gas. i'd like to see some testing done to find out at what point would be too much--ie: intake charge dilution.

guitarjunkie28

oh yea....had an interesting night last night

http://www.rotaryforums.com/forum/viewtopic.php?t=310

here's my new porting safety equipment (it won't make sense unless you read the other thread)

guitarjunkie28

i figure i'd route the snorkel into an fd airbox... the hose the smog pump breaths through is about the right size. high-flow respirator LOL

rotarygod

Actually that's backwards. Even an engine running at 100% volumetric efficiency will still have 10% exhaust gas dilution. Figure that one out! By scavenging, we are decreasing the amount of exhaust gas left in the engine to make more room for the incoming air.

Backpressure is a term that is used in this case to allow for more low end power. It's a little misleading though since the goal is to not outflow our needs. By adding some "backpressure" at lower rpm's, we hold the speed of gas a little higher and increase scavenging. Don't believe it? Put a 5" exhaust pipe on the car after the engine and see how much power you make. There's no backpressure. The smaller factory pipe has more backpressure and makes more power. The key is to have the least amount of backpressure with the highest exhaust gas speed. After you've reached the engine's max flow at that speed, anything larger will just hurt velocity and lower power.

therm8

kinda like shorties making more low end power on a V-8 and Long tubes making more high end while sacrificing low end?

guitarjunkie28

i usually have to read rg's replies twice to pick up whatever i missed the first time .

i am so gonna get him drunk and video tape him explaining something.

Japan8

No no.. RG has got something there. It is actually somewhat proven in the RX-8 already. Check out the old thread on the Leg Motorsports muffler. It has a vacuum actuator that is used to open up a second set of exhaust tips (4 total). The car showed a bit stronger low-end, especially at 500-100 rpm before the second set of pipes open up.

rotarygod

Why? Do you need me to describe things in more detail?

Richard Paul

iTrader: (5)

therm8, I think you have that backwards.

rotarygod

I was thinking the same thing.

therm8

lol, yep sorry :D

burnoutking999

Its ok, i can see where southern humor might not be appreciated everywhere. I wish i lived closer to you for another reason. I could have an awesome port job done! I guess ill have to wait till someone like racing beat gets their ducks in a row. All this waiting is frustrating though. Waiting for money.... waiting for problems w/ turbokit to be solved...porting...money.

guitarjunkie28

if you know how to put engines together, just spend $1200 on some irons and send them to me. i'll port them, send them back, then you can put your motor together at you liesure.

burnoutking999

that would mean that i have to get a car first or buy a motor before i can get the car and get it ready for installation. I might take you up on that last option but it will have to be at a later date.

guitarjunkie28

no problem.
i'm still looking for a test subject for the mecca-porting

robertdot

1) Florida isn't really the South. It's something else.

2) Even if it were, I'm from Alabama, which is def. the South, and I didn't get it. So, it must be Floridian humor.

3) My GF lived in Daytona, Florida for about 4 years, and she didn't think it was funny. So it must be Tallahassee humor.

Now that we have that sorted out, lets talk about porting

guitarjunkie28

aww, come on...it was funny. i got more pissy than everyone and i've got a sense of humor about it.

robertdot

I'm just hassling him. The winky-face at the end was supposed to justify it...