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More reliable than,... what exactly? If you're running the stock EFI, then there's not much more reliable than that. I mean, every Rx7 made after the SE has electronic fuel injection that's essentially bulletproof.
Maybe you can tell us some more about what you have today and where you're looking to improve it.
I want a little more power and to go carbed like stated in the first post. Maybe saying I wanted added reliability was what i meant in a sense that which carbed setup will be more reliable of the two. Holly or Weber. I will be going full exhaust front to back and would like to switch to Holly or Weber setup from racing beat. What kind of power gains can I gain from either on stock porting and which would have better throttle response.
And yes at the moment I'm running stock EFI, intake and exhaust minus the magnaflow muffler
I think in this case I would recommend a set of pineapple racing 5th and 6th port sleeves and a Racing Beat exhaust system. Carburating an SE almost seems barbaric for the minimal power gains from the conversion. As LongDuck stated, the EGI system with the dynamic effect intake system is extremely reliable and fuel mileage isn't awful on the highway. The car will feel sluggish at higher rpm if the 5th and 6th ports are stuck or the pressure tube that runs from the main converter to the intake manifold is not connected. With the dynamic effect intake system being disabled, the car will be reasonably slower. You'd be surprised at how quick the car is with the system functioning.
Can we revisit reasonable upgrades for the GSLSE engine? As I understand it, a six port intake manifold will bolt on. The S4 intake primary runner casting does not extend low enough to cover the EGR casing on the center plate. But it does have the throttle body with the mechanical OMP lever.
The S5 apparently has no lower intake manifold fitment issues ( as I recall reading) but has the electronic OMP. Also it has the VDI which is explained elsewhere on the forum. VDI could be controlled by an RPM switch. not sure if the standard aux port tube coming off if the split air tube would provide enough back pressure to operate the VDI.
What would the performance/ drivability difference be between using a FC intake, retaining the two GSLSE injectors and omitting the secondary injectors or running a DCOE carb or Holley?
We're getting a little off topic, but I hope the OP doesn't mind, as it speaks to EFI modifications which may interest him in the long run,...
The S5 intake will bolt up to an S3 GSL-SE engine, as the auxiliary ports are located identically. This gives the additional "breathing room" which the S5 cars are known to have just due to better tube dimensions, flow porting, and the Variable Duct Intake (VDI) switching which opens and closes butterfly valves between runners to tune the Dynamic Effect Intake to RPM and load. Essentially, this makes a more efficient intake timing pulse whereby the velocity of the air stack coming into the engine is timed to hit the rotor which is coming up on the Intake rotation at exactly the moment when the air pressure is highest hitting that port. When that intake port closes abruptly as the rotor swings by, the velocity of the air is switched to the other rotor just as it's intake port opens, and the high pressure wave serves as a natural supercharger. This bumped the HP numbers from an SE at 135bhp to the S5 cars nominal 150-155bhp stated power, but also improves torque substantially, flattening the curve and making torque much more usable across more of the RPM range.
It's not like a turbo or anything, it's just a few extra PSI of push at just the right moment, and given the rotary nature of the rotors spinning, it works to maximize intake flow, which can be matched with fuel for better power. Searching on "S5 intake into SE" will give you some results, and as you mentioned, the VDI circuit needs an RPM switch to function properly. Also, working out the staging of fuel injectors of which the S5 has 4 (*and the SE has only 2) is solved through ECU swap, along with wiring harness, and the different impedance fuel injectors to match. It's pretty staight-forward, but not a simple swap. Note also that 6-port operation is Air Pump controlled on an S5, but you can use the air injection tube from the stock SE setup, and not touch the 6-port operation; as it will still work correctly off of exhaust backpressure, as Mazda designed it.
Here's a good image of the underside of an S5 intake showing VDI air circuits and the associated switch (center);
Dynamic Effect Intake is a pretty elegant design once you understand how it works. Separate barrel carb throats can't accomplish this, obviously.
Last edited by LongDuck; Jul 11, 2022 at 06:45 PM.
Thanks LongDuck. I’m just trying to offer alternatives to” throwing a carb on it” I thought I had read people using the S4 intake and throttle body but keeping the existing GSLSE computer and injectors.
Thanks LongDuck. I’m just trying to offer alternatives to” throwing a carb on it” I thought I had read people using the S4 intake and throttle body but keeping the existing GSLSE computer and injectors.
I think this is the simplest of the two swaps and has been fairly common. I had considered this for my 84 SE that I'm restoring but I'm not entirely sure what I want to do yet.
Thanks LongDuck. I’m just trying to offer alternatives to” throwing a carb on it” I thought I had read people using the S4 intake and throttle body but keeping the existing GSLSE computer and injectors.
my friend did one, and it does add a bunch of power, mostly up top. fuel system has a tough time keeping up
you are correct about the emissions ports, the GSL-SE and S5 are the same, and compatible, but the S4 is weird. it is actually possible to use the S5 lower and S4 upper, there is one stud in a different place.
the S5 upper needs some grinding to fit on an earlier engine, on the upper inspection plate/top mount starter boss, the old engines have spots for 2 bolts. the S5 and newer engines loose one of them to make room for the intake.
my favorite setup is still the FC engine (S5 is ideal, because the ports line up), and the GSL-SE intake with the RB street port system, its like a street port. it makes power everywhere, with a peak around 6800. its great on the street
We're getting a little off topic, but I hope the OP doesn't mind, as it speaks to EFI modifications which may interest him in the long run,...
The S5 intake will bolt up to an S3 GSL-SE engine, as the auxiliary ports are located identically. This gives the additional "breathing room" which the S5 cars are known to have just due to better tube dimensions, flow porting, and the Variable Duct Intake (VDI) switching which opens and closes butterfly valves between runners to tune the Dynamic Effect Intake to RPM and load. Essentially, this makes a more efficient intake timing pulse whereby the velocity of the air stack coming into the engine is timed to hit the rotor which is coming up on the Intake rotation at exactly the moment when the air pressure is highest hitting that port. When that intake port closes abruptly as the rotor swings by, the velocity of the air is switched to the other rotor just as it's intake port opens, and the high pressure wave serves as a natural supercharger. This bumped the HP numbers from an SE at 135bhp to the S5 cars nominal 150-155bhp stated power, but also improves torque substantially, flattening the curve and making torque much more usable across more of the RPM range.
It's not like a turbo or anything, it's just a few extra PSI of push at just the right moment, and given the rotary nature of the rotors spinning, it works to maximize intake flow, which can be matched with fuel for better power. Searching on "S5 intake into SE" will give you some results, and as you mentioned, the VDI circuit needs an RPM switch to function properly. Also, working out the staging of fuel injectors of which the S5 has 4 (*and the SE has only 2) is solved through ECU swap, along with wiring harness, and the different impedance fuel injectors to match. It's pretty staight-forward, but not a simple swap. Note also that 6-port operation is Air Pump controlled on an S5, but you can use the air injection tube from the stock SE setup, and not touch the 6-port operation; as it will still work correctly off of exhaust backpressure, as Mazda designed it.
Here's a good image of the underside of an S5 intake showing VDI air circuits and the associated switch (center);
Dynamic Effect Intake is a pretty elegant design once you understand how it works. Separate barrel carb throats can't accomplish this, obviously.
This! This is what im looking for! In doing this can it be pair with the Pineapple racing 5/6 port sleeves? This is great information and im going to reread this tonight and do more digging.
This! This is what im looking for! In doing this can it be pair with the Pineapple racing 5/6 port sleeves? This is great information and im going to reread this tonight and do more digging.
No problem using the 6-port sleeves from Pineapple Racing. They are suitable for all 84-91 6-port engines .. regardless of which combination of S3, S4, S5 intake systems.
I just read an old article from Racing Beat. Think it was on their website because I was looking at swaybars, but they did a comparison between a Holly, Mikuni and Dellorto on a 6 port 13B, the Holly made the most HP. Seems to work well on a 6 port.
Last edited by lwrobins; Jul 19, 2022 at 09:18 AM.
So, in light of this new information - what would the parts list look like for the S5 intake manifold swap look like besides gaskets?
Will my upper manifold from my GSL-SE be swapped to the S5 intake. Do the 3/4 injector holes get plugged or can they be used with an ECU swap as well. If the ECU is swapped is it a whole harness swap or does it plug into the existing plug replacing the old one.
