I’m building an SE EGI with my son. I figured since the engine is apart it can’t hurt to clean-up the ports. Then I thought, while I’m in there I might as well open it up a bit.

I just want to say in advance, I’m not starting this thread without many hours of research to try to find an answer about this. I can’t seem to find anything for an NA, injected solution. Lot’s of talk about turbo applications with porting but no specifics about compensating with injection for NA applications. Maybe it just needs more injector volume or maybe it’s fine; the ECU will compensate with sensing more volume with the MAF and basic O2 sensor? It’s a pretty basic injection system. I mean it only uses two fat injectors for the whole RPM range.

What sort of modification is needed for the injection? The EGI uses two 680cc injectors. How much port will the stock injectors and ECU support? Any? Thanks in advance and I understand if nobody has an answer for me. I’d rather stick with the stock ECU. Can I? At least to run a street port?

 

Lots of questions. Here's one statement; Racing Beat won't port 13b EFI housings after finding that Mazda already designed the ports very close to the water jacket and they ruined many housings figuring out that the expertise wasn't worth the marginal performance gains. Porting with the 6-ports accounts for all of the Air intake timing you need for a flat power curve compared to the 12a.

Many have tried to improve on the stock 13b RE-EGI system, but most end up going to a later gen engine with staged (4) Injectors instead of being limited to the flow volume at 100% duty cycle on the 2× 680cc SE injectors. If you intend to use the stock ECU, that's what you're mapped for.

Lots of discussion on what can be done if you search on my Username and SE EFI. Over 20yrs of my posts are here,

 

imo, the stock ECU is one of the limiting factors in getting more power, it doesn't drive the injectors very hard or run very rich to start with, so modded GSL-SE's end up fuel limited
i think the injectors are ok for a little more power, maybe with a bump in fuel pressure (stock is ~36 i'd go to ~45)

for the engine the easy button used to be to run an S5 NA engine. its plug and play, even the emissions ports line up (the S4 NA has weird emissions ports)
the FC engines have larger ports, with more timing, lighter rotating assemblies, better seals, etc

so it used to be the easy button, S5 engine, GSL-SE everything else. mine had an RB street port exhaust and power curve was v8 like, fat power band that started around 2500 and peaked about 6500
it would still be a little fuel limited, 25 years ago there were band aids. i'm considering doing it again, and i'd run an aftermarket ECU for sure

 

I’m grateful for the replies. This helps. I was actually surprised to finally figure out that there was only two injectors on this engine. When I picked it up from the barnyard it was sitting in for years, the engine was have disassembled, missing parts and the rest (almost all of it) sitting in the cargo bay. Is it possible to use the 6-port SE engine but simply swap out the intake to get the 4-injector setup? Seems more efficient and accurate than trying to compensate for the AFR through a single port.

BUT now that I think about it more, I figure I’ll focus on cleaning up the ports leaving them mostly the same for the time being. As simple as this engine was to pull I guess I’m not to frightened to pull it again later when we decide to do something more radical. I think having it run is more important for me than performance for my first rotary build… and the SE engine looks pretty good inside. I guess ‘a bird in the hand’.

I really appreciate the confirmation for what I was thinking intuitively. There is a lot of information about the act of porting out there but relatively little by comparison about what will be required for injector size and tuning. Great to have input from your experience. I’ll definitely dig into your historic posts. Looks like you’ve got over 20 yrs of them to look through. LOL. Thanks team!

 

the last GSL-SE i did was just a stock engine with a light flywheel and exhaust, it doesn't sound like much, but on the race track we had more power than the average car which was nice
improving that would have required some old fashioned tuning, try different plugs, timings, maybe lower temp thermostat, etc