Possible 4-Port N/A Start?
 

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?

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?

EDIT: nvm...

Why can't I delete my own posts?

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

^^^ 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).

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...

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.c...e-port-12.html

Their J-port is everybody elses Bridge port.

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.

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.

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

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.

I'm familiar with that site and their porting definition is the reason I asked...
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?