Whizbang

That is what i hope this thread turns into. Seeing the search feature rids many useful words in searching and the word port brings up some interesting things.

so there is the Peripherial port, Bridge ports, street ports and partial versions of everything in between. Obviously, your going to port the exhaust ports so i wont beat a dead horse.

But finding out what port would be best for a NA application or for a FI application. How big the port should be for what rpm or what boost level. etc. That is something i think that people on this forum can recommend.

for example:

what would be the best porting for a 13b using 9.4 rotors, and a BNR s3 at 16psi? you get many threads on people just porting but it seems like people port blindly and you never hear the results.

so can anyone share their expertise and results?

scathcart

Porting is always a compromise. A ratio of gains versus losses. Why not tell us what you want for power and drivability, and we'll go from there?

I always build an engine and turbocharger system for the intended goals. I never match the engine to the turbo.

Whizbang

seeing i dont have the finacial means to rebalance everything, the redline will be 8000. maybe 8500. not sure what the safe limit of the S4 balance is. This is planned to be the fun car. meaning it must be able to be driven on the street but it wont be often and doesnt need to be comfortable. idle, as long as it does idle. I dont have huge clumps of money so i would rather have it be able to utilize a BNR rebuilt turbo. I cant drop 2k on a new turbonetics and then by alot of crap to make it work.

I plan on porting the intake manifolds as well. (it helps). basically upper end power is the goal. though whole powerband improvement would be nice.

eriksseven

iTrader: (6)

Hmm... Can you elaborate a bit more? Are you saying you match the TURBO to the engine (instead of the other way around)?

Or are you saying that 'whatever the power goals', you mate the best engine/turbo setup to THAT...?

Hopefully 88integraLS will post up, because he seems to have a lot of practical 'port testing' under his belt...

My latest TII egine has an odd mix of porting... lol.

The exhaust ports have been opened up significantly, like an extension of the RB template and shape (although 'squared' a bit more on the opening edge. I also didn't 'widen' them very much either.

My secondary intake ports are not *very* extended, but are shaped quite nicely IMO.

My primary intake ports are opened up a bit more than 'mild' on top, and have been extended 'down' a little bit more too.

Haha... I just realized this post is USELESS without pics, lol.

eriksseven

iTrader: (6)

oooh... Maybe you're the perfect candidate for a bridgeport ... I'm VERY jealous, lol.

Maybe half-bridge?

Whizbang

that was one of my original thoughts.

i also saw this port.

slpin

iTrader: (9)

oh NO! someones gonna come in and stir crap and we will have another 15 pages of argument!!

scathcart

I match the turbo to the engine. I don't find a turbo and then build an engine to suit it... that's stupid. That doesn't take into account desired power or drivability.

Would you buy a t-100 thumper, then deicde you need a PP just to spool the thing, and then attempt to drive the car on the street?

No. You make a drivability/power goal, examine what you'll have to give up to get to that power level, build an engine to suit, then choose a turbocharger to fit.


The thread starter wants decent low-mid on an engine concerned primarily with top-end power. This is tough. HArd to make huge gains up top without sacrificing elsewhere, especially on the extremely limited budget he has listed.

How about some power goals? How about a total budget?

Whizbang

well i started the thread with the intent of learning how one can decide how to make such desisions. How do you know how each port will behave? I know that low end power is going to suffer. and i am going to accept that. But i dont want to move the power band beyond the limits of the turbocharger i have. i dont have a large budget to work with. so i would like to work with what i have. Ie rebuilt stock stock (BNR). The porting is all manaul labor which i can go for essentially free.

diagoro

how does porting affect redline?

Whizbang

no no no.

i dont want to exceed 8 - 8.5k as my redline. but you can port a motor to the point where the peak power is passed the redline. like a PP port. you can go crazy.

rotarygod

iTrader: (1)

Let's see here, huge honking port, RB header, full exhaust, intake:

https://www.rx7club.com/time-slips-dyno-128/dynod-streetport-today-393588/

Stock port with an S-AFC, intake and stock exhaust manifold with the rest aftermarket exhaust, removed 6 port system:

https://www.rx7club.com/time-slips-dyno-128/na-6-port-dynoed-152whp-details-inside-461424/

s4 stock ecu no piggybacks, stock ignition timing
s5 rotors and counterweights
t2 exhaust inserts (rotor housing)
t2 intake manifolds(this didnt seem to affect power, except its like having the 6 port sleeves removed on the NA manifolds)
stage 1 street port (not nearly as large as link #1. This is properly done)
racing beat catback
racing beat header
non resonated midpipe 2.5"

https://www.rx7club.com/time-slips-dyno-128/na-streetport-6-port-dynoed-182whp-details-inside-416012/

Update to the above with an S-AFC

https://www.rx7club.com/time-slips-dyno-128/na-6port-streetport-dynoed-195whp-update-418805/

Need I say more? I was never proved wrong in that other thread. Far from it!

-another guy

88IntegraLS

Just because peak power occurs above your target redline for a certain port doesn't negate the fact that the observed power at that redline might still be more than a milder port which does peak at that point.

Drivability, emissions, fuel economy and the need for a loud a$$ exhaust are the drawbacks of wild ports, their advantages are obviously more power than stock or mild ports.

Fluid dymamics in a pulsing system like a rotary engine is not easy science, it's really kind of a land of sketchy empirical data (ie. this port shape did this, that one did that, etc). The simpler theories I have found to be true in my port jobs are this:

low overlap = low emissions, high fuel economy

late closing intakes = good boost in power, low loss of fuel economy / drivability

early opening intakes (street ports, not bridge) take away some fuel economy and off-idle torque but add a good bit of power above 3k rpm and above.

A good mild exhaust port job = opening the port about 2mm lower than stock, this retains the stock power band with late closing intakes pretty nicely. 27mpg is my average freeway mpg with this setup.

my largest exhaust port was 2mm later, 4mm earlier than stock and it really shifts up the power band (less torque under 3k rpm, much more above 5-6k)

The bigger the exhaust port, the more necessary it is to get a header and free flowing exhaust to take advantage of it.

And lastly, don't take the port out so far toward the water jacket that the leading tips of the opening side seals aren't sitting on at least 1mm of metal, and make the closing edges have a scissor angle with the closing side seals.

These rules have proven themselves in my own experiences, but I don't claim to be an expert, this is just what I have observed after messing with my ports several times.

88IntegraLS

The combined secondary / aux port style has proven itself in more than one person's car, Ddub being one, Judge Ito who ported some other car like that being the other.

Even Paul Yaw of Yaw Power has tried this port. the problem most of the failed combined secondary / aux ports have is they violate a cardinal rule in porting: big timing is good, big volume usually isn't without extreme intake manifold mods. I never take my ports down, only up and out toward the water jacket, hogging them out makes them flow like crap unless the manifold runners and complete intake system are matched, and even then a larger runner / port volume only gets substantial flow velocity at insane CFM levels that rotaries won't see in normal street rpm ranges.

So yeah, like anything hard to understand, porting isn't always what it seems.

rotarygod

iTrader: (1)

Yep the key is in the manifold setup to go with it and in tuning. Just hogging them out into one large port and then using all stock components is a waste of time. Paul Yaw and Dave Lemon from Mazdatrix both have done this port. They also used new induction systems and did it for race use. For street use where you will retain the stock ecu and intake system, it's a waste of time. There's place for everything.

Whizbang

i like what 88 posted. good reference for port desgining.

my own goals set aside emissions and fuel economy. my other 7 already is hampered by that so this is not going to be.

i should pm Ddub about how that port worked out.

rotarygod

iTrader: (1)

He pulled that motor out and is doing it differently now if that tells you anything.

Whizbang

yes. yes it does

i guess i could try to swing a half bridge and see what happens.

rotarygod

iTrader: (1)

If you want to try a bridge on the aux ports only, you will still need to do some work. First off you will need a custom manifold that spearates all 6 ports. Otherwise you'll get some interference from different tunings of the secondaries and aux ports. The stock ecu won't be happy with it either as the stock intake is too restrictive for a bridgeport. If you intend to keep the stock intake, stay with street porting. If you are willing to change everything over to aftermarket parts and ecu, you have many more options.

full-cruise

iTrader: (5)

What's the real point in going with a big port on the stock turbo.. your just going to run out of boost before the motor gets tired.

i put a stage 2 hybrid on and picked up lag, im rebuilding the motor now with a ITO's streetport in hopes to make up for the lag..

Whizbang

i was at nopi this weekend talking the only rotary team there.

seeing they where into the 7 secs, i decided there info is good. Apparently they are running a mostly stock motor with a streetport on a 4port (other than that who knows the size and whatnot). Anyhow they use alcohol and run 48psi. They use OEM everyting else and just clear the rotors to prevent a stuck seal. they get like three to four runs before they have to rebuild but that is the name of that game anyhow.

then again, i can use 48 psi. ill be using like, oh say less than that. so IDK. i might try to just do a proper streetport and see how it goes.

88IntegraLS

Street ports have a ton of potential. The really wild ports like bridge, j, PP, were invented for NA race applications; once a compressor is installed upstream the ports, huge overlap isn't as necessary for huge power.