Hey guys, ported my first iron tonight, and i think it Went pretty well. I used the RB streetport templates, a 22,000 rpm air die grinder, double cut carbide bit, and a 80 grit sandpaper roll. I found the double cut carbide bits jump a whole lot less than the single cut bits. It took less time then i expected, maybe 45 min - 1 hour. My questions are, is the runner radius on the top of the port good? Also what methods are the best is smoothing out the transition from the runner, to the wall going to the port? All in all, I still have a bunch more smoothing out and sanding to be done, but I found that just taking your time, being comfortable, and supporting your hands on something sturdy produce the best results. Ear protection and glasses are a must as well, and mechanic gloves make the job more comfortable as well. Take a look and tell me what you think,
Thanks, Matt

 

well im no expert on porting but from what ive seen it looks pretty good.

 

i dont know much bout porting etc but looks pretty good
did you have sum idea of what to do like how deep and what kinda tunnel it needs
is that a street port?
im just interested could save me money on proting and do a diy-port

 

Now just break out the dremmel and cleanit up get the runner nice and smooth make sure yo get those humps out of the airpath. I'm not refering to the casting, but the humps in the runner path from your porting.

 

Keep at with the 80 grit sanding rolls until all of the irregularities are gone. For final smoothing, you can use stones. You will need to add a little more bevel on the edge where the side seal runs across it.

 

Good job Matt.

I'm no porting expert but I like what I see!

Best place for port feedback is probably the "Rotary Engine Rebuilding and Porting" section over at nopistons.com - They've got some awesome guys over there.

Jon

 

Jon is right on with NP, that's where I learned all of my porting from.

You need to smooth the rest of the runners to where the intake mounts too. I bought a long carbide bur to do that part, along with the longer mandrel for for the sanding rolls.

 

Yes adding the bevel is very important! Looks real good. Nice work!

 

Other than moving large irregularities, and burs and such. DONT SMOOTH IT, leave it with a cross hatched pattern, make it rough in that intake!! The more uneven and irregular the intake ports are, the better fuel atomization you will have. In a port and polish job, the polishing refers to the exhaust port, not the intake....

Sorry if this is something you guys know, but you would be surprised how many people simply dont know this. BTW Looks great!

Chris

 

Yeah, I remeber hearing somthing like that from my uncle when I was helping him port one of his 12a's.
He finished the job but I learned a bit from it. Thanks for the reminder

 

Should i use 80 Grit sanding to rough up the runners then?

 

That should be fine, just make sure the runners are free of all metal shavings and debris when you finish. I would just use some paper towels and carb cleaner to clean it with.

The idea behind this is that the intake charge will bounce around more with those irregularities and in effect achieve a more even mixture that will be closer to the coveted 14.7:1 stoiciometric ratio at which an engine would be running at a supposed 100% efficiency, barring heat and frictional losses. Its like chocolate milk, the chocolate and the milk will slowly seperate so you want to shake it up or stir it so you attain the best flavor.

 

"Other than moving large irregularities, and burs and such. DONT SMOOTH IT, leave it with a cross hatched pattern, make it rough in that intake!! The more uneven and irregular the intake ports are, the better fuel atomization you will have. "

This is good advice. I would recommend you do not sand the intake ports with 80 grit paper. The rough finish from the die grinder should be good. A friend of mine who was in the business for years had a visit from one of the research and test engineers at Mazda, and he recommended just that. He said don't sand, just use the die grinder unless you are planning to race at LeMans! As an Aero engineer myself, I can understand the importance of maintaining a turbulent boundary layer in the intake, to prevent fuel puddling.

Also, for street driving, just minor porting and smoothing up the exhaust is sufficient. The main effect of seriously enlarging the exhaust is to make more noise.

For both the intake and exhaust, there are two separate subjects here. One is the timing, which is determined by the size and shape of the opening at the surface of the rotor. The second is the size of the flow path from the port to the carb or exhaust manifold. It doesn't take much work to open up the timing, but removing the material over the entire length of the flow path can take several hours.

Choosing the right housings helps too. The attached photo shows some cast irons from an old RX-4, which have been seriously ported. Someone here may know what year they are - some years had really big ports.

 

look at the intermediate plate, is it just me or does the left port have a higher arch than the right? and if so what does that effect?

 

Maybe it is an optical delusion! I will have to look - these are sitting on the shelf in my storage building. I know they were used in a 13b that had a Holley and produced more than 250 hp on an engine dyno. It was in an RX-3 and was FAST.

IMG 1689 shows the intake porting on those housings, slightly larger than the RB street port template. They have been resurfaced, ready to go, but I don't know if I will ever build another rotary. I have two freshly built ported 13b engines sitting there, so I am set for any future projects.

The porting shown at the beginning of this thread is very rounded, which does not optimize the flow in my opinion. The Racing Beat street port template has the cutoff in a straight line as shown in the attached photo with the die grinder. This is in a 12a my current 84 GSL, and I only did this porting on the secondaries, with just minor cleanup on the primaries and exhaust. That way, it runs and drives just like a stock engine until I go to full throttle. Uses an RX-4 carb, dynoed 130 HP to the wheels, peak HP at 7,000.

 

The idea behind not smoothing the intake runners is that the rough surface creates a boundry layer of turbulent air flow, swirls/eddys would be be the easiest laymans terms. This turbulence helps prevent the fuel saturated mixture from making contact with the surface and helps prevent the liquid fuel from sticking/depositing on the surface.

Flow velocity through a round/oval pipe is similiar to a bell curve used in statistics. The cross section of the path follows the bell curve with the center of the cross section having the highest flow velocity and the edges/surface, the slowest. The slower the velocity, the more fuel deposition occurs. The bell curve becomes skewed when turns or changes in direction are encountered.

The fuel doesn't actually puddle, but it will stick to the surface, which smooths the surface and can cause more of the fuel mixture to stick.

 

What kind of exhaust porting is recommended with the RB street port and weber 48 IDA carb on a daily driver, without concerns of noise? I was thinking just lowering the exhaust port a bit and giving it more of a radius, will this do?

 

Here are the Racing Beat street port patterns, at least this is what they were using 15 years ago. My method is to cover the port area with a thick plastic tape, lay on the template, then cut out the tape with a sharp blade, leaving the outline as shown in my previous post. Don't take a chance on damaging your metal template by trying to port with it in place.

I don't port the exhausts this big on motors I have done in recent years. Everyone who is in the business says, if you only do one thing to a stock motor, install a RB exhaust header. That tells me the exhaust ports are not a limiting factor in the performance. Whatever else you do, install one of these headers.