Possible 4-Port N/A Start?

[infernosg]

So for the longest time I've wanted to do a 4-port N/A build on my '89 GXL. I've found an engine locally for a good price that may be a good candidate, but I'm not sure. It's a '88 TII engine w/ 100k miles on it. I'm told it holds compression but the coolant seals are gone. I'm really only interested in the housings as my plan consists of swapping in a S5 front cover, RX-8 e-shaft and some S5 N/A rotors (RX-8 rotors would be nice, but I've heard there are timing issues?). Ultimate plan would be a streetported or bridgeported motor with ITB's and being controlled by a PS1000 or Sprint RE.

I'm just curious if I should be weary of the coolant seal failure even though I will be rebuilding the engine from the ground up. Also, are there other incompatabilities between S4 motors and the S5 chassis I should be aware of?

[infernosg]

So I'll want to hold onto the S4 front cover, water pump, water pump cover and OMP it seems. Either that or swap everything over from a S5, but I didn't want to have two engines pulled apart at the same time so I could actually still drive the car

Seller mentioned one or more of the coolant o-rings have failed, but that the engine still ran. Waiting to hear back from him so I can go check it out.

Has anyone else gone retro-active with a S4 motor in a S5?

[infernosg]

EDIT: nvm...

Why can't I delete my own posts?

[vex]

So for the longest time I've wanted to do a 4-port N/A build on my '89 GXL. I've found an engine locally for a good price that may be a good candidate, but I'm not sure. It's a '88 TII engine w/ 100k miles on it. I'm told it holds compression but the coolant seals are gone. I'm really only interested in the housings as my plan consists of swapping in a S5 front cover, RX-8 e-shaft and some S5 N/A rotors (RX-8 rotors would be nice, but I've heard there are timing issues?). Ultimate plan would be a streetported or bridgeported motor with ITB's and being controlled by a PS1000 or Sprint RE.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.

I'm just curious if I should be weary of the coolant seal failure even though I will be rebuilding the engine from the ground up. Also, are there other incompatabilities between S4 motors and the S5 chassis I should be aware of?
Coolant seal failure motors are a crap shoot. It could just be a simple seal gave out and it hasn't done any damage to the housing. However, when my coolant seal crapped itself, the actual housing that held the groove for the seal had been removed/fell out/eroded away. Depending on how the seal went bust the engine may have been over heated.

There is minimal incompatibilities between the S4 and S5 motors (I'm currently running an S5 rear plate since my S4 took a crap)
So I'll want to hold onto the S4 front cover, water pump, water pump cover and OMP it seems. Either that or swap everything over from a S5, but I didn't want to have two engines pulled apart at the same time so I could actually still drive the carYou can swap what ever you want from any gen 13B except the renesis. The trouble comes when you want to use alternate versions of the same engine. IE you can't go between an S4 and S5 front cover and oil pump/distribution block. A little research could help you out with the details.

Seller mentioned one or more of the coolant o-rings have failed, but that the engine still ran. Waiting to hear back from him so I can go check it out.

Has anyone else gone retro-active with a S4 motor in a S5?
It should be fine. It's the same basic engine, it's just the OMP is mechanical instead of run via a stepper motor (and a few other odds and ends).
EDIT: nvm...

Why can't I delete my own posts?

because you're not 1337! You has no powA' here!

[infernosg]

^^^ Figured as much. I know I could easily just swap the front and rear covers from the current engine in and call it a day. Only reason for considering the S4 front was because of the mechanical OMP, which I'm on the fence about keeping and I don't really want to have to pull the current engine and have the car down for the entire duration of the build.

The RX-8 rotating assembly is tempting - I just thought I read somewhere (probably RX7C) that the RX-8 rotors weren't necessary a good change, despite the increased compression, which is something I'd like to have.

Hopefully will be checking out engine today. May also be picking up the transmission as well (don't know if I'm going to use it or not though).

EDIT: Still debating between a small bridgeport (not cutting into water jacket) or large streetport for the motor. I've read a lot on both and am still not decided. Can anyone make a case for either?

[SLIDN2]

^^^ Figured as much. I know I could easily just swap the front and rear covers from the current engine in and call it a day. Only reason for considering the S4 front was because of the mechanical OMP, which I'm on the fence about keeping and I don't really want to have to pull the current engine and have the car down for the entire duration of the build.

The RX-8 rotating assembly is tempting - I just thought I read somewhere (probably RX7C) that the RX-8 rotors weren't necessary a good change, despite the increased compression, which is something I'd like to have.

Hopefully will be checking out engine today. May also be picking up the transmission as well (don't know if I'm going to use it or not though).

EDIT: Still debating between a small bridgeport (not cutting into water jacket) or large streetport for the motor. I've read a lot on both and am still not decided. Can anyone make a case for either?

Half Bridgeport TII engine NA (loving it).

[Buggy]

I basically have the exact engine you want to build with a half bridge. Only difference is I have old school 4 port irons and housings. The half bridge is nice, makes really good power even at lower RPM. Mine still isn't tuned 100%, but I'm still fairly happy with it. With ITB's and a stand alone you should be in nice shape. As for the renesis rotors there are issues running them in older engines. As far as I know there are slight differences in seal design and placement on the rotors that make fitting them in the older engines a problem. I think it can be done, but you'll have to do some more research on that one.

[infernosg]

Half Bridgeport TII engine NA (loving it).

I basically have the exact engine you want to build with a half bridge. Only difference is I have old school 4 port irons and housings. The half bridge is nice, makes really good power even at lower RPM. Mine still isn't tuned 100%, but I'm still fairly happy with it. With ITB's and a stand alone you should be in nice shape. As for the renesis rotors there are issues running them in older engines. As far as I know there are slight differences in seal design and placement on the rotors that make fitting them in the older engines a problem. I think it can be done, but you'll have to do some more research on that one.
So what constitutes a half bridge on a 4-port motor? I always assumed a half-bridge referred to bridging the primary ports on the 6-port motors.

Either way, I still don't have a motor to play with. The seller of this particular one flaked out (just never called me back) even though it's still being listed as for sale. His loss...

[vex]

So what constitutes a half bridge on a 4-port motor? I always assumed a half-bridge referred to bridging the primary ports on the 6-port motors.

Either way, I still don't have a motor to play with. The seller of this particular one flaked out (just never called me back) even though it's still being listed as for sale. His loss...

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.

http://www.rotaryengineillustrated.com/porting/bridge-port-12.html

Their J-port is everybody elses Bridge port.

[Buggy]

On my engine I just did an ordinary bridge port on the secondary ports (the ones in the outside irons) and just a streetport on the primary ports (in the center iron). I didn't have to cut into any water jackets on mine, but it is just a 4 port.

[NoDOHC]

Hey Buggy, I am curious what you get on the dyno with your setup. That will be interesting to contrast the power band of that engine to the one that I posted earlier from mine. You probably have a naturally better intake, but I am mostly interrested in low end, torque curve, etc. Also, what do you get for fuel economy?

To the original poster: Go 4-port FTW! I was worried about losing low-end going from a 6-port to a 4 port, 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.

The only thing I would do differently if I ever get a chance would be to use NA rotors instead of turbo ones. I don't know if the small weight savings and additional 3 point on the compression ratio makes it worth the expense for RX8 rotors or e-shaft.

[SLIDN2]

Just go with a TII engine with na rotors for high commpresion.
GSL-SE rotors are actually considered light and high compression.

[SLIDN2]

On my engine I just did an ordinary bridge port on the secondary ports (the ones in the outside irons) and just a streetport on the primary ports (in the center iron). I didn't have to cut into any water jackets on mine, but it is just a 4 port.

I did the exact same thing normal bridgeport on the outer plates and a big street port in the inner one, also I ported the exhaust ports and pinned the engine just incase I wanna give it a nice NOS shot later on, remember rotarys love nitrous.

[Buggy]

I did the exact same thing normal bridgeport on the outer plates and a big street port in the inner one, also I ported the exhaust ports and pinned the engine just incase I wanna give it a nice NOS shot later on, remember rotarys love nitrous.

Ya, I completely forgot to mention that I played with the exhaust ports as well. I'm actually curious myself as to what my engine can do. I need to get it to a dyno and do some pulls. The weber still needs some tuning but it still pulls pretty nice. In 4th gear (which is all I've got) you can stomp on it at 60mph and it just pulls away untill you hit speeds that are relatively unsafe with 34 year old brake and suspension technology.:) The only thing I may change is to go with a different carb. The 48 IDF is a bit small. It feels like it's choking out at the higher RPMs. I was toying with the idea of a dual 40 IDF setup. Might make things interesting.

[infernosg]

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.

http://www.rotaryengineillustrated.com/porting/bridge-port-12.html

Their J-port is everybody elses Bridge port.
I'm familiar with that site and their porting definition is the reason I asked...
Just go with a TII engine with na rotors for high commpresion.
This is pretty much my plan - the RX-8 stuff is really just speculation at this point.

Thanks for all the info everyone - I'm dead set on doing this, but I still need an engine with which to start! So, although I'm not too concerned because it really isn't a daily driver, but to those with half bridges, how the driveability on the street?

[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.

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.

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.

... 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]

... 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.


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).

http://i594.photobucket.com/albums/tt25/NoDOHC/6-4portComparison.png

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]

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]

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]

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
http://i594.photobucket.com/albums/tt25/NoDOHC/P3100254.jpg

Modified 6-port sleeve
http://i594.photobucket.com/albums/tt25/NoDOHC/P3100253.jpg

Modified 6-port sleeve
http://i594.photobucket.com/albums/tt25/NoDOHC/P3100256.jpg

Polished 4-port sleeve
http://i594.photobucket.com/albums/tt25/NoDOHC/PA110558.jpg

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.

[NoDOHC]

So why did Mazda even make a 6 port?


If you look at my mileage numbers above you will see that they were better on gas. They also would probably make better low-end torque if that awful mess of an upper intake manifold were to be replaced with a decent aftermarket one and some ITBs.

Some day I intend to build a max-effort 6-port with a custom upper intake manifold. I saved 2 sets of irons to practice with for the porting (filling the top of the aux ports will probably prove to be the most difficult part).

[RETed]

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...

Be careful of the comparison...
The 4-port was using a "heavily modified intake setup" - that's already a big advantage.
Most of us know the stock intake manifolds are pretty restrictive.


-Ted

[My5ABaby]

Be careful of the comparison...
The 4-port was using a "heavily modified intake setup" - that's already a big advantage.
Most of us know the stock intake manifolds are pretty restrictive.


-Ted
Ah, missed that part. :icon_tup:

[NoDOHC]

I apologize that I don't have numbers for a stock 4-port, I have one right now (slated for a friend), but it is too much work to put it in the car (and I don't want to give up the power). I do know a guy who put down 185 WHp @ 7200 rpm and 145 Wlb-ft @ 5100 rpm on a carb'd 4-port (with completely stock ports on a Mustang dyno). However he was not running a stock intake manifold either.

The comparison is not very fair, but the 6-port did have 9.4:1 rotors while the 4-port was running 8.2:1. They had similar tunes (same ECU). I would love to see some dyno curves from built 6-ports.

I have one from a friend with fully ported 6-port, custom intake w/ ITBs, MicroTech EMS and stock ignition. I can't scan the curve right now, but it made 142 WLb-Ft @ 6600 rpm and 195 WHp @ 8400 rpm (Dyna-pack dyno).