WondrousBread

While I have my engine apart, I'm looking at what I can do porting-wise to pick up a little bit of power. My expectations are realistic (it's a Series 4 NA, I don't expect that much) but I'd be happy if I could maximize the power I can produce while remaining streetable and reliable. It seems obvious that I should remove the diffusers from the exhaust sleeves, but beyond that I'm a bit lost. There are different port templates from different vendors, and no clear advantages to one over another.

My requirements are that the car remains streetable down low (idle at or below 900, not sacrificing too much torque) and that I retain the auxiliary port actuators. It also needs to run on the stock ECU, but I imagine this isn't an issue on reasonably sized street ports.

I was thinking of just using the basic Mazdatrix intake port templates (here) combined with the Racing Beat exhaust template (here). I know Mazdatrix doesn't recommend porting the exhaust on a 6 port engine, but as I recall that was due to the diffuser in the exhaust sleeve (which I'll be removing).

Is this a good plan? Or is there something different I should be doing port-wise to achieve my goals? Thanks, Chris

Dak

That's pretty much what I did except I used Pineapple Racing's Templates. Mainly because at the time they came already cut out and I liked the holder alignment jig the exhaust templates came with. I think I did their medium street port on the exhaust IIRC. I didn't really touch the aux ports at all. Just the primary an opened the secondaries a little sooner. I'm still using the stock S5 ecu and it works fine. I think I lost a little below 4 to 5k but all my aux port stuff is gone so I'm sure that's hurting that some. IIRC my idle is in the 900 to 1k rpm range. Pulls strong from between 5 to 6k rpm to the 8500 rpm rev limit. Not sure if all this helps since you're S4.

Also you're correct Mazdatrix doesn't recommend porting the 6 port rotor housings due to the diffusers. If those are gone then port away.

WondrousBread

Thanks for the input, I appreciate it. Does the Racing Beat template not have the same alignment tabs as the pineapple template? How would you be sure it's located properly otherwise?

The S4 redline (stock) is 7k, I imagine revving much higher than that would require other supporting upgrades. The S5 got lighter rotors. I know the Rx8 got hardened stationary gears and multi-window bearings, combined with a lightened e-shaft and further lightened rotors, and they have a 9k redline (iirc). If I'm moving the new redline higher, presumably I'd need to include some of these upgrades to provide insurance at high rpm? I have a matched set of rotors (C), but I doubt that on it's own is enough to rev up there safely. Come to think of it, I'm not even sure what the stock ECU does after you rev way past the stock redline.

I also expect that the S4 intake becomes a restriction at some point, since the S5 intake was redesigned for the higher redline too. This isn't a terribly big deal though since the intake can be changed later on without taking the engine apart.

Also, how much louder did the engine become without exhaust diffusers? Is it something that can be mitigated with a straight-through silencer? I don't mind the car being a bit loud, but it's easy to "not mind" a loud car until you spend awhile driving in it.

lespaul166

I’ll say from what I’ve read in my adventures of trying to build a rowdy 6-port, and I can’t say much on actual ports because answers vary wildly, but from what I’ve found in terms of the Intake at least, the S4 is less restrictive in terms of shape but not passageways, the S5 is more restrictive shape wise but larger passages. So you’re better off opening up an S4 intake than opening up an S5 Intake, but if you’re going purely bolt on, the S5 Intake will take the S4

Obviously the S5 rotors and after that RX-8 rotors have higher compressions to. I can’t find any real concrete evidence to benefit one over the other, but I’ve loosely compiled that any benefits stop at S5, and you just see losses or neutrality going to RX8. I also believe that overrevving a rotary is significantly less bad than overrevving a piston engine. I don’t believe the internal components have any bearing on what your redline can be, except for maybe the bearings and stat gears. I don’t think the rotor or e shaft being lighter is going to make your redline potential increase, as after a certain point you have to start clearancing the rotors so they don’t clash with the irons on e shaft flex. I’m not sure if the RX-8 e shaft fixed this or not, I know they sell 2 piece e shafts that are supposed to mitigate flex at high RPMs?

like i said, in terms of porting the actual irons I have no real answer. My local rotary expert says no gains will be seen on a 6 port until you go full peripheral, Ive heard other people talk about picking up 20hp opening up their primaries. I’m not at the point of doing that yet as I’m still trying to feel out what my best options are (6 port vs 4 port, rotors, e shaft, etc) to get the 200bhp-whp mark, but I’m going to definitely follow this thread.


Again, take everything I’ve said here with a grain of salt as I’ve stuff I’ve compiled over maybe 3 months of semi intensely looking into building a ripping N/A 2 rotor. I’ve got little experience in rotaries and have only owned one half a year, I’m just offering the perspective of someone who is focusing entirely on making N/A power because turbos suck and N/A is king in my shitty opinion

WondrousBread

I've seen some similar information, but the trouble is that I keep seeing different schools of thought on common things like port matching and smoothing runners. One school of thought says to port-match intakes, one school of thought says that anti-reversion lips are better. Another common thing I hear is "polishing" yields gains, but then I also read claims that the grainy texture of the unpolished casting causes turbulence that mixes the Air/Fuel mixture better. My gut tells me that a port match / polish won't really provide too much of a difference, but I have a spare set of intake manifolds so it's something I can definitely reverse if I need to.

The S5 intake is also presumably tuned around 9.7 c/r rotors, so it's entirely possible that it won't be suited for a ported S4 engine with 9.4 rotors.

I would imagine there are diminishing returns with higher compression ratio after a point, but my main reason for sticking with S4 rotors is just that I have them already. I had originally planned to run S4 rotors because I wanted to do a 6 port turbo later on, but the more porting I do the less practical that plan becomes. As an aside, I have to wonder why it's recommended to not use 6 port irons in a turbo setup (due to the late intake closing time) when bridgeported turbo engines are a thing. I'm sure it's not a 1:1 comparison, but a late closing on a bridgeport is still a late closing, right? And you would have the advantage of possibly being able to control the aux ports.

While it may be less bad than over-revving a piston engine, there has to be a practical redline. I'd expect the S4 redline is due to power falling off after 7k rather than a mechanical limitation, but the rotors and e-shaft lightening actually does make sense to me;

I'm going to preface this by saying I'm not an engineer. If you consider what could cause an e-shaft to bend, the likely answer is that at high rpm uneven weight causes it to flex back and forth, which would let the rotors hit the housing. Lightening and balancing the assembly would cause this to happen at a higher rpm, since the unbalanced weight is lesser. This is moot for me since lightening and balancing services just aren't available to me locally (or practical right now for me), but I could try and find a used Rx8 e-shaft and stat gears. That would at least lose some weight from the e-shaft and give me stronger gears with better bearings, as long as balancing isn't necessary since the e-shaft weight has changed.

I also hear the same thing from people, and I generally believe their experience since I've never done this before. But logically speaking, I can't see why porting wouldn't yield some sort of gains (to a point). I imagine someone finding that they don't gain any power at all from porting must also be due to factors like the intake no longer being optimized or porting too far and moving the powerband to a point that it isn't usable (ie, gaining power where you won't use it and lowing power where you will).

The advantage in my mind of using the 6 port housings comes from the auxiliary ports themselves. If keeping the ports functional (with the stock setup or otherwise) isn't intended, then practically there isn't much advantage to the 6 port irons over the 4 port other than availability. People looking for power also favour the 4 port irons and seem to have had more success in general, but I'll leave that up to those with more experience than myself to figure out.

The other consideration is that for years, the "go fast" recipe for FCs has been very simple: swap in a 13BT. This doesn't mean that people haven't experimented with porting (in fact, the massive amount of discussion about the topic is overwhelming) but it does mean there's been a simpler way to make power. I've met lots of people who have said that porting isn't worth it and turbo is the way to go, and in some ways I believe them. But I think from the standpoint of already having an engine open with the intention of rebuilding it and staying NA (at least for quite awhile), porting makes more sense.

EDIT: And not to knock your local rotary expert, but wouldn't the choice of irons (6 port vs 4 port) be irrelevant if going to a peripheral port? I may be missing something, but normally the intake ports are filled with epoxy in a p-port setup, since the intake is moved to the housing.

I've been reading everything I can about this sort of thing for about 4 years, but that doesn't give me the practical experience that others have. I have a good theoretical understanding of what these modifications do, but a theoretical understanding isn't nearly as useful as practical knowledge of exactly how it pans out.

lespaul166

I’m sure the information is out there more concretely, it’s just hard to sift through the Internet experts sometimes. Like I posted about my first time here, you can find such wildly varied accounts of power, some people saying that 170bhp is the absolute limit for an N/A setup and it’s purely impossible to squeeze out more, to other people going “well so-and-so had a streetable S5 that made 250rwhp all day”, and trying to pick the facts from the fiction is a pain.

If you’re planning on going turbo, I’d just do it. Doing any sort of port work at this point seems fairly moot, as you’re eventually going to undo it, or have to get more components. I’m sticking to N/A strictly because I’m a stubborn arsehole who has a turbo car as a daily and it’s given me nothing but headaches and I’m just over turbos as a whole. I love all motor cars. I understand that forced induction has its place and is incredibly important in gaining power by today’s standards (no all motor engine will match a forced induction engine obviously). But knowing that what you’re putting to the wheels is a result of absolute optimization of every component of the engine and not just “I strapped a Hiroshima hurricane onto it” is my personal direction. I wouldn’t personally waste the time or money hunting for N/A power if turbo is in the future. It’s not for me, so Imma keep hunting

WondrousBread

The original long long long term plan (once literally every other aspect of the car was to my liking) was to go turbo, but that was back when I was under the impression I had a healthy engine. Once a rebuild became the new reality, the plans became somewhat more fluid.

The reliability aspect you mentioned is also important. I don't doubt that a mild turbo setup can be reliable, but there's something to be said for NA simplicity. Not to say that making a good NA is simple, but you don't have to worry about the extra oil and coolant lines, the intercooler, etc.

At a certain point, you just want to be able to get in your car and drive.

Dak

The pineapple has this nifty jig that attaches to the housing with a dowel pin and holds the template in place. https://www.pineappleracing.com/ep2a...-t13b-rew.aspx
I don't know much about the S4 ecu so I don't know where the sock rev limit for it is. maybe 7500 rpm?

As for the exhaust. Because of the time the car was apart when I did the motor I couldn't say how much louder. I don't think it's much. I have the Racing Beat collected header going into their pre-silencer the to this https://web.archive.org/web/20040708...com/e86-92.htm old HKS 50mm cat back. To me it's about right with this setup. I'd say the RB mufflers would be just fine as well but probably a touch louder. I think you'll definitely want their pre silencer in the system even if it is their universal one. I had some Ebay special mufflers which were 2.5" cores and virtually no packing for a while after the welds on the HKS rusted away and it had too many leaks to be usable. https://www.rx7club.com/2nd-generati...ement-1079600/ It was too loud. The tone was good but the volume was too much. Talking to a passenger is possible with the HKS setup but it's a moot point since it's been NLA for 15 years. Had a friend with no diffusers and the RB mufflers and I think it would be livable as well.

Dak

My butt dyno says he's wrong. It's not night and day different but it is noticeable. Is it worth tearing a good engine apart? Maybe not but if one is doing a rebuild it's definitely worth it. IMO. Of course keep in mind I went to a lightweight flywheel at the same time and port matched my header so my improvements could be from the total package.

Dirty_oil6

The factory (very old tech) ecu can't really compensate for the added flow. If you go standalone and get the car tuned then you'll see the actual gains.

lespaul166

Oh ****, you’re the guy who did the intake port write up im about to start following this week

Anything you’d change otherwise before I start plowing ahead with this thing?

WondrousBread

I would imagine that's part of it. My understanding is that the stock ECU is about as complicated as a brick, so it's not really practical for anything that deviates significantly from a stock setup.

One thing I'd add for sure is that there are seals for the shafts that actuate the auxiliary ports. I don't think them leaking is common (mine never seemed to), but as soon as I reassemble my engine I'm going to replace them and document it for that thread.

Akaviri

iTrader: (1)

Currently assembling my S4 NA to run on a standalone Haltech. I've been reading about the RX8 injectors - they have the same dimensions as the FC injectors but achieve greater atomization. They need slightly higher fuel pressure, so an aftermarket regulator may be necessary. Has anyone successfully done this on an NA? I'm on the fence, willing to do it while I have the manifolds off if its a boost in efficiency and power.

WondrousBread

I haven't done that myself, but I did do a bit of investigating on this before. My conclusions so far:

- You want the yellow Rx8 injectors (I believe the flow rate is actually 420cc instead of the stock Rx7 460cc, but we won't exhaust that on an S4 NA). I think this is the one you're looking for

More info here

- The Rx8 injector top and bottom look to be a direct fit in the FC fuel rails and engine. I'm not sure about the exact height, but that also looks to be right. It can be deceiving because the Rx8 injectors are skinnier.

- You'll need to take out the plastic injector diffusers and break off the diffuser part and its "legs". This leaves you with a spacer with an o-ring, and the old diffuser is no longer necessary. I imagine leaving the diffuser intact would negate any gains from the improved spray pattern. Be very careful not to break these in the engine, they're super fragile. The secondaries are easy because you can take them off with the manifold, but the primaries you need to reach into the primary port on the engine and gently push them back out the top.

- The connector looks the same, but photos of other Rx8 injectors show a different connector. This could be something that was only implemented later, or you might need to change the connector on your harness.

What I don't know:

- Is it worth it? Since you have things apart already, and you can tune your fuel, it might be worthwhile for you. For me, I'd be replacing four working injectors with four working injectors, and need to invest in a wideband + SAFC or similar (if not a full standalone) to take advantage of this modification.

- I'm not personally aware of anyone who has actually done it yet. In theory it looks good, but I haven't seen any testimonials or dyno sheets from stock-ish setups with Rx8 injectors.

Dirty_oil6

I'd say it would be worth it for other engines with lower cc injectors stock. only advantage I see is maybe a couple degrees of cooler intake temp, but lower cc tbh I don't think that's worth it. you'll have to swap them for any forced induction mods or even better flowing intake (porting). IMO. They are cheap as hell so give it a test if you feel like it! I'd rather make a cheap little meth injection for the same money and better temps and ability to adjust timing a little more

Rotary Police

I as well have use the templates several times and how they attach makes it impossible to make mistakes.

WondrousBread

So after doing even more research, I have a tentative plan of approach on this thing. There are a few really useful threads here with dyno sheets:

ITB'd Stock Port 6 Port NA Dyno : Stock block with ITB's and port matched manifold, RB exhaust, standalone - 169.6 whp, 140 ft-lbs tq. Aux ports open all the time, of course.

So we know that using a different intake setup and a freer flowing exhaust, plus a standalone to tune for the new setup, you can get ~170hp at the wheels. To get a rough estimate of the power at the flywheel, lets assume 15% drivetrain loss (is that reasonable?) and get 170 / (.85) = 200 hp at the flywheel. Compared to the stock 146hp at the flywheel, this means that between the better flowing intake with shorter runners and the less restrictive exhaust, djSL picked up 54 hp. The stock ports are seeming a lot more capable now. This still doesn't include possible gains from smoothing the castings and removing the exhaust diffusers. It's also worth noting that those figures are at 6800rpm, and the dyno sheet looks really linear.

For a comparison with a streetported engine:

184 RWHP S4 6-port : Moderate Pineapple streetport (enlarged upon further, no pictures of the final port), S5 TII housings (no diffusers), 6 port inserts with ramps instead of sleeves (aux ports constantly open with the transition smoothed), all intakes ported smoothed and matched, RB exhaust ported to match exhaust ports. Stock ECU with an SAFC-II to allow fuel tuning - 184.9whp, 152tq.

So we know that changing from a stock port to a (moderate / larger) streetport, port matching everything, smoothing the aux port transition, and a free flowing exhaust gets you farther than ITB's do on a stock block. It's arguable that ITB's on the streetported block might even get you farther. But if we consider that it's "only" a 14.9hp gain over the stockport block with ITB's, you end up shifting the powerband up a bit to get there. The dyno sheet looks good, but the power falls off at ~7500rpm (OP mentioned that they were having trouble getting the ECU to drive the injectors hard enough to go farther).

One thing that complicates things is that the stock intakes are designed with super long runners for torque, compromising flow. In my case, I want the stock ECU and some low-end torque, so the intakes work to my benefit (even if I don't make use of some top-end potential). Another thing to consider is that even if the streetport sacrifices a bit of low-end, grinding out the diffuser seems like it would yield gains across the board. It isn't just that it's a restriction, I imagine it causes significant turbulence (since it's basically a silencer) which would be detrimental at any engine speed.

Since my prerequisites were decent low-end and stock intakes / ECU, I feel like the logical plan is to do basically what Dak suggested near the top of this thread, combined with some of the intake improvements from the second thread I linked. I think that this plan should yield the mix of low end streetable + slightly extended high end that I'm looking for:

• Very mild exhaust / streetport, focusing mostly on cleaning up and smoothing the existing ports.
• Grind out exhaust diffusers.
• Port match / smooth all intake manifolds.
• Keep 6p actuators, possibly upgrade to the ramped ones sold by Atkins.
• Headers.

And unrelated to the actual power-making modifications, a lightened flywheel would probably help make the car more lively.

From what I can tell that should put me in the ballpark of what I'm looking for. A SAFC and a wideband might be required to get the full potential of the port, but that should be reasonably happy on a stock ECU for the foreseeable future.

These plans might end up changing before I actually commit, but I think I'm going to proceed with this unless more data / other suggestions come up.

Akaviri

iTrader: (1)

I'm about ready to pull the trigger and order some RX8 injectors. However, there are a few different flavors with varying output. The 420cc seems sufficient but I wonder if they will be maxed out eventually. Considering the rich factory tune I'll likely be stripping out fuel, so the 528cc might be overkill. I'm new to a lot of this; would it be smarter to run the blue injectors at a lower duty cycle or use the yellow injectors for a more fine resolution of adjustment?

WondrousBread

I'm also new to this, but I expect that the 420cc would be perfectly fine. To my knowledge the stock S4 ecu runs rich, and still doesn't drive it's injectors very hard. I think as long as you stay NA you probably won't max out the 420cc injectors. There are injector calculators to calculate how many hp you can run with a given injector setup. This calculator says that you can run up to 272hp (at the crank) from four 420cc injectors with an 85% duty cycle. I don't know the accuracy of that calculator, but since crossing 220-230 flywheel hp seems unlikely it looks to be a safe margin.

If you're worried about exceeding that (though I doubt an S4 NA will get there easily), get 420cc primaries and 528cc secondaries, then stage them so that you aren't using the secondaries when driving around town (the stock ecu stages the secondaries at ~4000rpm iirc).

lespaul166

This thread has made me so much more confident in my build. I sometimes get worried that I’m chasing a lost cause, but hearing 186rwhp on a street port setup and stock ECU is possible really brightened my day lol

ablesnead

iTrader: (1)

our champ car does 190 at the wheels with a mazdatrix street port and a standalone , our exhaust is not very good , so possible losses there..my track car with isc street port intake and exhaust , factory s4 ecu , turbo injectors , feels near the champ car , but no dyno , it has a awesome maximized exhaust system , no baffles or auxillary ports....

WondrousBread

This might be a slight change of topic but it should fall within the scope of the original question I posed:

Are you able to use Rx8 stationary gears with the stock FC E-Shaft, or do you need the Rx8 E-Shaft?

I know you need to machine a groove for the o-ring in the rear gear, and you need to oval one of the oil supply holes. But I read that the clearance for the journal bearing is different, so I don't know if the FC shaft will work with the Rx8 bearings.

I'd like to avoid getting the Rx8 shaft because my stock shaft should be fine. I do need new bearings and since I don't have a press I'd be only a little bit shy of the cost of new Rx8 gears w/bearings anyways, so that seems like a worthwhile upgrade. And from what I read, the front stack should work fine with the Rx8 gears.