guitarjunkie28

even though the sleeves aren't open, when the material is removed from the iron, it creates a "pocket" in which the exhaust gas can flow into the intake and vice-versa.
there will be some intake dilution, but i'm curious to see if it'll take away from the low end. i'd imagine it would a little bit, but to what degree?

guitarjunkie28

just for fun...

here's a port really similar to the one i put 300 down with 9 psi. in my fc with a stock-based hybrid turbo.

i'll try to find the dyno sheet--it's around somewhere. i think it had like 200 whp @ 3800 rpm. turbo wasn't big enough for the port, but very linear, VERY drivable setup. i may do something similar to that next tiem instead of the half-bridge.

naw....i'm gonna hit up a 3 rotor

rotarygod

No idea where you would find such a person here. :D

x-mann

lmao :D :D

guitarjunkie28

i want some renesis rotor housings for an fc project...i'll cut the exhaust port myself, i just really like the oil injector locations. :D

Petrus

How do you think the porting will affect the gasconsumption wich already is rather high?

twospoons_

Excuse my ignorance, but I thought that smooth surfaces was kind outdated when it came to designing for optimal flow. Has anyone experimented with implementing small dimples or other structural patterns to reduce the drag by intentionally creating a turbulent flow?

It somehow depends on how fast the air flows; if anyone can give me some average velocity of the airspeed it might be worth looking into.

/r

guitarjunkie28

petrus, i think snoochie is actually getting better gas milage now. look back a few pages-i think he said something aobut it.

twospoons, i'm not sure about that--maybe RG can help you out with the flow bench. i'd be curious to see how it works, but i don't have the equipment to design and test what you're talking about. in any case, outdated or no, the porting works. now if it can be made better, i'd be all ears to anyone who wants to give that a go and share the results.

in my own experience, i know about what my porting is good for--more or less anyway. there's a lot i do know, but there's a lot i have to learn. do you have any links to info on what you're talking about so i can do some homework?

rotarygod

You want surfaces smooth up to a point. You can overdo it. What you don't want is mirror smooth surfaces. The original reasoning behind this is comes from the days of carbs where fuel and air flow the entire distance. On mirror smooth surfaces, the air just wouldn't stick to the sides but would keep flowing really fast through the intake manifold. This sounds good but you have to remember that the air turns easier than the fuel does. What would happen is that air would flow nicely around corners but the fuel, through inertial forces, would get slung out to the outsides of the corners and would fall out of suspension. The solution to this was to have a rougher surface which would create more surface tension to the air. This would lead to a small amount of turbulence on the runer edges which would be just enough to keep the fuel off of the walls and in the airstream where it belongs.

This isn't really a concern if you have a fuel injected system that mounts the fuel injectors right at the entrance to the engine. You can make those runners as smooth as you want and be just fine. The key is that after the injectors you do not want a mirror finish. This is some of the confusion that people have with the Extrude Honing process. On many engines like Hondas, the injectors are placed at the very ends of the runners right behind the valves. A smooth surface on the manifold runners is just fine. If you take a V-8 engine that has a carb and try this process with their manifolds, you will lose power becuase fuel wil fall out of suspension.

I'm sure there is a point where you would always want some form of turbulence but if you just use this as a general reference, you'll be fine.

twospoons_

It makes sense that this would be somewhat hard to accomplish on the intake, what about the exhaust ports? Doesn’t the air flow at a very high rate?

A dimpled / pattern structure is only beneficial if you know that you will have separation of the laminar flow, something which occurs at a relatively high air flow rate. If you know that your air flow always will separate then you design for a turbulent flow.

guitarjunkie28

so even if a mirror finish flows better, it may not be the very best thing for the intake? i can always rough things back up. and if that's the case, i guess i'd rough up the entire secondary port (rx7 motor), but only the point after the injectors on the primary ports? is there a particular "grit" that you'd recommend?

but would i be correct to assume the "mirror" finish would be best for the exhaust--since we don't have to worry about air and fuel mixing together?

twospoons_

For the exhaust ports I think it might be beneficial to have a rough finish, but as stated, it depends on how fast the air flows. The only way to get good answers on this is to either measure exhaust air speed or to test different designs.

Again, I’m just into the theoretical part about this, so I might be completely off target.

guitarjunkie28

yea, i know what you're saying. it'd be nice to know in any case. i'm happy with the gains we did get, but if i can do it better and improve on it, i will.

Richard Paul

iTrader: (5)

RG is correct and explains it well, as usual. But the super smooth wall will also keep the droplets intact furthering the first problem. So what we have is "wet flow" and "dry flow". The surface as it was from grinding is a good point to stop. In other words it is no longer "port and polish" just porting.

dry flow can be helped with polishing so transfer from polished to ground surface at the point of injection makes sense. That is a thought I have had for awhile but have never tried it.

Polishing the exhaust port will slow down the deposit of carbon but not prevent it. Therefore it may be worth doing.

As to "dimpling" the surface, this was tried with wetflow testing at Airflow Research several years ago in combustion chambers but I never saw it take off. The thing is that in a race engine you have max velosity and tumble and swirl will only limit flow. There is enough going on with just the speed to mix the fuel here.

As to airspeed in the tract .6 mach is a number I hear from NASCAR people but I can't varify it. And I don't know where in the tract they get that. After all if something works they are not going to tell me. They may tell me last weeks trick because it is obsolete now.

Also MAXvelosity is probably just prior to the valve seat or choke down point. OK OK you don't have those things called valves. But that is the only knowledge i have, use it with application specific interpretation. Poppet valve designers use this trick to get the airflow around the head of the valve in a good cone shape. It can also be used by the really good porters to aim the flow so as to get good blowdown.

350 fps is a number I use for the duct going from my SC to the intake manifold. Remember if I make it bigger it slows down. Everybody wants it bigger??

AvatarQAZ

you have me oddly intrigued with the work you have done guitarjunkie . I have a few questions concerning the fabulous port job you did on Snoochie's ride.

If these questions have been answered, I apologize. But after taking in 52 pages of material, one can not remember their own SSN let alone how many redundant questions got answers.

When you redid the exhaust, did you ever think about fabbing a custom pipe off the exhaust port to improve the flow. I know that the current exhaust system on the 8 has terrible flow... so it might makes sense, for the sake of prepping the car for say; a turbo, to fab a more linear exhaust system to include catback and such.

And is there any way you would fly to georgia for free room and board to port and rx8 ?

guitarjunkie28

imo,
the exhaust system on the 8 isn't all that bad. if you change the entire system from the header back to the muffler and only get 10 hp, it tells me mazda did a pretty good job.
we'll play with the exhaust on snoochies car and see what it yields after the porting, but in terms of actually designing a new header, i don't have the equipment or the knowledge to do so with confidence. i bet RG or some of the other guys could do a lot better than me as far as that's concerned. about as far as i go with that is welding mufflers on. i'm just not equipped for the cool stuff.

would i fly to georgia? if you think that highly of my work, sure. i've never been there before, so hook me up with the couch and show me what there is to see in your town. that'd be a fun week!

AvatarQAZ

Hmmmm....

One question I forgot to ask... have you started any other jobs besides the one you did for snoochie? i.e. built a better mouse trap?

If you would like to come to georgia, I am sure there is a way I can set such a circumstance up. The best time to come would surely be around the masters tournament (I know, golf, ick) as I live about 10 minutes from the course.

And from what I have seen from your work, I am thoroughly impressed. I would also rather trust someone who feels confident enough to allow about 50 rx8 owners to critique their work by presenting it, in near full detail, to a very hard to impress crowd... that in itself, demonstrates to me that you are confident in your work. That makes me confident in you .

You can even have my waterbed and the finest steak I have to offer.

guitarjunkie28

cool.

honestly, i don't have a bed--well i have one, i just don't use it. i like sleeping on the floor better. lol


i do have one more engine in my garage...it's the one i started with--the one i'm STILL waiting on parts for. that's the one i got the welding done on and the aux ports are a tad bigger. i have no clue when that thing's gonna go back together...i've been waiting for the parts for 2 months. it's starting to be an eyesore in my garage.

when were you thinking about?

AvatarQAZ

This is where we get fun

If you were to come to the Peach State, as I said, around the master's golf tournament would be the time to fully take in the scenery and atmosphere. With that in mind, it would not be until the week of 4 April.

I know that is a ways out, but gives you plenty of time to plan an prepare. In the meantime, we would surely have to work out all details to this project as I know the burden of just about everything would fall onto you.

With that in mind, send me a PM or email (jeremysim@hotmail.com) with all the details of the job as well as everything I have to do to accomodate you and make your potential stay here a healthy one. I will let you know that my job requires me to put in 10-14 hour days depending on the circumstances of the days events. It may just be easier for me to take some time off and drive to cali (where I have never been) and meet up that way.

Either way, still send me the details of your requests and we can match them up with my availability and weigh them against practicality to see if we can make this happen.

guitarjunkie28

ahhh...april.

you should have been able to tell i'm not current on golf-event-based calendar periods

plenty of time to plan... we'll be in touch

zoom44

hmmmm... i wonder if avatarQAZ and i have met? but he/she says they've never been to cali.....maybe we have a mutual aquaintance....

AvatarQAZ

Why do you say that zoom44? I do know many people that are from the cali/oregon area. But no one strikes my mind when it comes to this kind of subject matter and being able to relate mutual friends. I am intrigued, please explain...

zoom44

i met a couple of people from georgia at 7stock this past september. all rotorheads of course being where they were. reading your post reminded very much of talking to one of them in particular- i dont know why. something about the cadence of your posts( or the "sound" of your posts in my head) could just be my imagination. anyway one is a famous race engine builder, another one that came with them knew a thing or 2 about ceramics but the one im thinking of works at MazMart. if you know at least 50 8 owners and he knows a good deal of rotary owners in the state you probably have met.

AvatarQAZ

Interesting way of deriving things .

But, I moved to georgia in late August. Thus, I never had the chance to attend 7stock (they had it down here... amazing?) So the gentlemen in question, I probably do not know . Although I have been trying with much grief to find fellow rotarians down here since I made up my mind to buy an rx8 months ago and recently purchased one (best day of my life). Maybe I should hang out at gas stations more.

And that cadence you noted is either perfect grammar... or poor grammar. I hope it is the former or else my father would have my tongue wrapped around my neck.

rotarygod

I am having printer/scanner problems right now but I have that info in an engineering textbook. It is called " The Internal Combustion Engine in Theory and Practice Volume 1: Thermodynamics, Fluid Flow, Performance" by Charles Fayette Taylor. Look for it. When I fix the scanner, I'll post the relevant pages here. There is even a graph that shows how efficiency stays good until this point and then rapidly falls off.