Hey guys I tried to search for my specific questions but didn't really find it. I've owned all generation rx7's including 4 GSL-SE's. I really can't get over the 1st gens especially the SE. Now I want to get another 1st gen but I want some more naturally aspirated power. I was thinking to get another GSL-SE and get it street ported and add some bolt ons, or get a GSL (84-85) and swap a S5 (89-91) naturally aspirated motor and get that street ported and add the bolt ons. Now the extra power I can get from the S5, would I be able to match that power with the SE 13b motor with internal mods? like putting S5 rotors in it? Which route is better overall?

Thanks!

 

the S5 is basically a revised version of the GSL-SE engine. there are only about 2-3 things that the S5 has that you couldn't add to a GSL-SE engine.

the S5 has larger ports and runners, the S5 (all FC's) have a larger diameter oil pump.

the S5 also has higher compression, lighter rotors, hardened stationary gears, and better tension bolts, but all these go right into a GSL-SE engine.

i had an FC engine in my GSL-SE and really liked it, then i put a GSL-SE engine in with an S5 rotating assembly and power was down by like 15hp... so i'm thinking the FC ports > higher compression rotors.

 

cool man thanks for the info!

 

starting with the complete S5 engine as a base. i have nothing against the S3 13B, but evolution is a good thing!

 

not sure if you know, but around how much would a swap like that cost including the labor?

 

Just our the whole s5 keg in there or for originality if you put the s5 rotating assembly in the s4 keg your gonna have to find 2 blocks one s4 and one s5.. each block could cost 500 on a good deal but who knows when one of those will show up. Master Rebuild kit-1000 and another 1000 in labor if you choose to go that way. Better port that s3 block too-800 Do it yourself man you might learn something. And save a whole bunch of cash.

 

That will be a nice build Goodluck!

 

S3*

 

honestly, i have no clue.

i really don't know what S5 blocks go for these days. i've had no reason to look in a long time. also, keep in mind that you're looking for at least the engine, ECU and harness (unless you plan for a standalone). a rebuild may or may not be necessary, but you won't know until you get the engine and know the circumstances/history of it. as for labor, given the fact that your conversion would include wiring and the inevitable odds and ends that that will bring, there's no way to predict even if you were to figure ... say ... a $75 per hour shop rate.

a few other things to consider:

getting an SE would be beneficial because then you don't have to "find" an oil pan or front cover.

if you don't plan on doing the complete S5 ECU or a standalone, then it doesn't much matter which 6 port you start with.

if you do go with the S5 ECU, you'll have to find a way to get around the "missing" MOP.

 

My understanding is that the 4 port from the S4 and S5 Turbo is better to use in NA form because you can port it out more than the 6 ports. If this is true, S5 Turbo engine minus the Turbo with S5 NA rotors, port the crap out of it and upgrade the fuel system (pump, injectors) and get a standalone ECU. This should yield the best possible NA results right? 250-300 NA hp?

 

Opposite. Less port duration. The 6-port engines have too much duration, ports close way too late, the powerband that the port closing would indicate is beyond what the airflow capabilities of the engine are. 4-ports are more in harmony of what the port window vs. airflow capabilities are, and harmony in design results in harmony of driving and long story short the 4-port kicks *** and pwns face over the 6port.

Although I do wonder what a 6 port engine could do if you have 8.5 rotors in it for better high RPM internal airflow and a good intake manifold. Maybe crack 250whp with it, for the ten minutes that it could run between rebuilds. RPM Ruins Peoples Motors even rotaries.

 

ohh man you guys are jerks now that I read this forum I am looking for an S4 and S5 assembly LoL

 

depends on labor rate

the 89-91 engine can run all the GSL-SE external accessories, which makes this basically the same amount of labor to do as a stock GSL-SE.

the part where it gets pricey is when you want to run the FC's ecu, which is fairly involved to install, and this could be something like 40+ hours by itself.

best combo is the FC engine with GSL-SE intake/ignition/ecu and some kind of aftermarket exhaust, it runs great, and is very easy to do.

the stock FC injection is picky, complex and you always need to find some weird/expensive/rare part

 

Great info guys! I appreciate it

 

j9fd3s,

So there is not a problem using an engine block designed for four injectors?

 

the blocks themselves can be adapted to any 6-port setting, 2 or 4 injectors, because for the most part, the intakes are interchangeable.

 

only two injectors are on the engine, the FC's have two more on the intake, so if you keep the GSL-SE intake, then you keep 2 injectors

 

Got it. Thank you