Possible 4-Port N/A Start?

[project86]

i didnt read all the posts but i think they issue with the rx8 rotors maybe because they are balanced for front and rear? could that maybe cause the timing issue you were thinking of? but then again if you had the whole assembly blanced it wouldnt matter would it?

[Buggy]

The drivability in my car is pretty good most of the time. It's still running WAY too rich, and it tends to cough and sputter a bit when you are cruising down the road under light throttle. I've still got some work to do on the weber. Otherwise it's awesome. I'm running a stock S5 NA flywheel which helps out as well. We'll see what it's like with the light one from tweakit if it ever shows up....

[Redshft]

It's my race car, not a street car (so streetability wasn't a consideration) but, figured I'd chime in. I'm running S5 4-port irons, full bridge port with RX8 rotors, e-shaft, stationary gears etc. and a Weber 51IDA.
Full disclosure, I've not gotten it properly tuned, as I can't seem to keep a transmission in the car (I changed it out 6 times in a year) but initial signs are promising. It does work, it seems to be promising power-wise so far.
With S5 rotors getting scarcer all the time, I think more people will start using RX8 rotors down the road, but, there are a few catches.

If you are going to port it, be aware that the side seals on an RX8 rotor are in a slightly different position than the RX7 rotor. So, in my case, my builder needed to tweak the bridge port template a bit as if he used his standard bridge template (which was Racing Beat I believe) the corner seal would hit the port. So, he needed to create his own.
The other thing is, the apex seals lands are not as deep on the RX8 since they have no peripheral exhaust ports and they don't need to be. We had my rotor lands EDM wire cut to accept Racing Beat RX7 apex seals and they fit perfectly.

[Silver86]

i shoulve searched before making my thread... cause this is also exactly what i plan on doing...

[infernosg]

So let's bring this back from the dead since my stock 6-port looks like it's in need of a rebuild.

Has anyone tried to run a 4-port motor in N/A form using the stock 6-port ECU and wiring harness? I'm thinking of picking up a 4-port motor in the near future and start my "long-term" engine plans rather than revuild my 6-port, but I don't exactly have the funds right now for a full standalone, ITB's, etc.. I'm curious if I can just use the TII intake manifold, throttle body, BAC, etc. with the N/A electronics just to have a running car while I save up for the other goodies.

[diabolical1]

this is something i should have done - fingers crossed - in a few weeks. for the most part my engine is built and sitting, but being the "winner" that i am, i brought all my engine parts up from FL except ... wait for it ... the bloody front pulley! so i need to locate one before i can do my endplay check and button up the front cover and oil pan.

i've been learning the hard way that there are a few slight, yet distinct, differences between the N/A and T2 parts. for example, the secondary fuel rail (which i need one as well). if you don't get the complete engine with manifolds and such (like i did), it can be quite frustrating tracking down little parts like that rail. another physical different is the fact that the intakes draw from opposite sides of the engine bay - so i'm not sure how i'll hook up the MAF to the intake tract just yet. throttle cables are different, but i know of at least one person that made the N/A cable work on a T2 block with manifolds.

as for the differences in sensors, unfortunately, i can't say yet. i have not mounted the engine in the bay so i don't know which sensors have different plugs or are simply not there. my gut tells me that it won't be an issue though.

that said, i don't see why the stock 6-port ECU would have an issue with running the engine - maybe not great/identical, but decently. honestly, i expect some differences in fueling, but i don't expect it to be drastic. i'll note here though that i built my T2 block with 9.4 rotors.

[diabolical1]

i realize that this is a year old, but it's the first time i've read this thread, so forgive my late commentary and questions.

as i understand it, the Renesis rotors, on paper, should make slightly more power than the 9.4s and 9.7s given the same setup with only the rotors being different. all the hard facts support it - lighter, higher compression, bevels, etc.

however, most reports from people that have actually put them in older engines have them making the same power at best, and actually making less power in the majority of the time. i've read a couple of theories on why - some sort of make sense to me, some don't, which leads me to believe if anyone actually KNOWS why, they're not talking about it. my guess is greater heads than mine are still working on it.

no doubt some people are not regretful for using them, and make decent power, but with the trouble of the extra machining and balancing, it comes down to personal choice really. i suppose it still carries a coolness coefficient with it as well. however, it doesn't appear that more power has been validated.

as for timing issues with them, i don't know if you'd call it "issues" per se, but they appear to tolerate (even prefer) more aggressive ignition timing when being tuned.

Originally Posted by vex

I don't believe there are any timing issues with the RX8 rotors. Same physical dimensions--just higher compression ratio and that comes in the tub.

more of an addition than a correction, but remember the Renesis rotors are beveled from the factory, so the intake timing for any older engine using them will be slightly different.

Originally Posted by vex

You can search for the exact definition of the half-bridge, but it's basically half the length of a normal bridge; hence why you won't have to cut into the water jacket.

half bridge is when you bridge just a half of the engine - meaning, there's one bridgeport per rotor instead of two (full bridge). convention usually bridges the secondaries only, but i have heard of a handful of people that for whatever reason, bridged only the primaries.

Originally Posted by NoDOHC

... but the 4-port stomps the 6-port above 1800 rpm. Meaning that you get better grunt, even on the interstate in high gear. Idle is good and mileage doesn't suffer much (35mpg 6-port -> 30 mpg 4-port with NA 5-speed, 25 mpg 4-port with turbo 5-speed).

The 4-port is easy to work on (all kinds of space where the turbo is supposed to go), runs cooler (could be from the lower compression ratio) and is much simpler to tune.

this is going to sound way more confrontational than i mean it to be, but where are you getting this from? i'm MOSTLY interested in the parts i bolded, but i'd like to know for the sake of curiosity and/or possible learning, about everything you mentioned.

[NoDOHC]

Originally Posted by diabolical1

this is going to sound way more confrontational than i mean it to be, but where are you getting this from? i'm MOSTLY interested in the parts i bolded, but i'd like to know for the sake of curiosity and/or possible learning, about everything you mentioned.

You will certainly have to sound a lot more confrontational that that before I will interpret it as anything other than seeking clarification.

The numbers for the torque curves are slightly skewed, as I compared a mildly ported 4-port with a heavily modified intake setup to a stock 6-port with 195,000 miles on it. The 6-port did have a higher compression ratio (9.4:1 vs. 8.2:1 - in defense of the fairness of the comparison).

Preliminary data (halted by an inopportune failure) would indicate that the 4-port makes more torque than the 6-port at 1,000 RPM if they have the same compression ratio.

I compared the torque curves from dyno runs of the two engines and computed the VE curves from known injection durations from the datalog taken during each dyno run and the AFR which was logged during the dyno run. Same dyno, same AFR gauge, same ECU (the numbers may be wrong, but they are consistant for comparison).

The following torque chart is made in Excel, but the numbers came from two dyno charts (in this case they were both from the G-Tech on the same stretch of road).



The mpg data is taken by me as I fill up a tank of fuel. I keep a running average (with outliers discarded) for each car, so I was able to simply extract the data from the chart and present it above. Actual data (with more miles on the 4-port) is: 6-port = 32 mpg city, 38 mpg highway, 4-port = 22 mpg city, 29 mpg highway (numbers above were early in the 4-port engine's life and I was babying it at the time).

EDIT: Actually, I forgot that early in the 4-port's life I was using NA drivetrain, which gave a 0.69 Overdrive. I am not sure if I was babying it or if the NA drivetrain was that much better for mileage.

Higher compression rotors help the 4-port, but I don't have enough data to express exactly how much.

My first seven tanks on the new build:
18mpg (mixed driving/idling/tuning)
24mpg (3/4 mixed driving 1/4 highway, low-speed VE improved significantly towards the end of the tank)
27mpg (1/2 highway, 1/4 mixed, 1/4 city)
28.5mpg (3/4 highway, 1/4 city)
31mpg (All highway)
31.2mpg (3/4 highway 1/4 mixed)
30.8mpg (1/2 highway, 1/2 mixed)

For running temperature, I am only looking at the ECU data logs and observing that the 4-port ran about 4 degrees C cooler on average than the 6-port. The two engines used the same water pump and thermostat, as I had already tapped it for the Haltech sensors, so this to me was a marked change.

For ease of tuning, you didn't have to worry about where the ports open at various throttles (which makes a difference when you are tuning with speed/density).

I hope this helped you some.

[diabolical1]

wow! someone's been busy.

this actually helps a lot. it gives fairly simple parameters that can be replicated easily. however, it gave me context. when i originally read your post, i was thinking this was all put forth as general information as opposed to your car/engine and your own data collection.

whenever my current project gets off the ground, i will likely try to collect the same data you have for added comparison. thank for clarifying it all for me.

[NoDOHC]

Any additional data will be useful - a sample size of 1 is not a very complete indication.

The 4-port making more power than a 6-port is relatively common knowledge, that is why I opted to buy and build a 4-port rather than upgrading my 6-port.

I know a guy who spent several iterations of porting on a 6-port and managed to get 192 WHp on a dynojet out of it at 8,400 rpm. I was impressed until my nearly stock 4-port put down 216 WHp at 7,500 rpm on a Mustang Dyno. If I had done as much to my 4-port as he had to his 6-port it would probably have beat his numbers by quite a bit more. He is now building a 4-port.

[infernosg]

So... has anyone got one? Pending the condition of my housings I suppose I really only need the irons and the exhaust sleeves.

[My5ABaby]

So why did Mazda even make a 6 port?

[j9fd3s]

Originally Posted by My5ABaby

So why did Mazda even make a 6 port?

because everyone complains that the rotary has no low end torque! only an automotive journalist would drive under 2000rpms, and ignore the rest of the tach.....

[My5ABaby]

Originally Posted by j9fd3s

because everyone complains that the rotary has no low end torque! only an automotive journalist would drive under 2000rpms, and ignore the rest of the tach.....

From what it appears at least on the above dyno, the 4port basically only makes less torque than the 6 port at idle. If it's around 1k that they equalize it's pretty much the second the gas pedal gets looked at...

[NoDOHC]

Originally Posted by infernosg

So... has anyone got one? Pending the condition of my housings I suppose I really only need the irons and the exhaust sleeves.

Look on eBay and craigslist in your area for the irons. The NA sleeves can be cleaned up to almost meet turbo flow numbers.

Modified 6-port sleeve


Modified 6-port sleeve


Modified 6-port sleeve


Polished 4-port sleeve


If you can find the whole engine for cheap, go that route, I got a complete engine for $250.00 with carbon-locked apex seals - a little cleaning up and it was good as new.