Hey people i have been looking at this for a while. I have had a 88FC for a while now 114k on the clock never been rebuilt so i felt time for a little more grunt. Heres what i have in mind (and just ordered)

13B six port
Large street port
50mm individualThrottle bodies
Turbo II top feed injectors
Greddy E-manage on the fuel.
Racing beat dual headers and in house built exhaust for the rest.

Should be fun. Just waiting now for the bits to turn up so i can crack on.

 

the isc header looks better. it is a little straighter out of the engine, and it looks like its more equal in length, compared to the RB.

the car i tuned also has the expansion chamber thing, i didnt see tuning the ecu that it was doing anything different than anything else, but its not dialed yet either

 

3hp is also probably less than the repeatability of the dyno, or could be related to other factors.

I've only played with a chassis dyno once, using my car, and it lost 10hp from heat soak, and probably just plain entropy. No tuning changes.

Our engine dyno here at work uses a 1000 gallon tank of water for the load cell and for engine cooling, so the engine never sees over thermostat temperature, and the engine is outdoors, out in the open. (It's REALLY COOL to see a 500hp Pontiac engine running at full chat at night )


If you do want to give credence to a small change like that, also note that the peak torque dropped a small amount, and start to wonder what the powerbands are *shaped* like. The VDI might give a slightly lower but also longer powerband, which will end up being faster in the Real World.

 

I have read that the S5 na intake manifolds will have 1-2 psi of positive pressure at WOT. Someone with a functioning manifold should hook up a boost gauge and see if it's true.
Another question I've always wondered is why people don't build 6 ports. RB swears against them, and it's parroted knowlege not to build them. If they already have the late closing of a bridge port, then in theory, couldn't they develop close to the same hp with out the draw backs of a BP if the primarys are given an aggressive street port?

 

I agree here. I'm not sure I gained or lost anything (air temp, humidity, etc were different between those 2 days)

You are right with the powerband to, the dyno graphs show a slightly lower but longer powerband


I'm not sure how relevant it is, but my datalogs, which record the manifold pressure show up to 0.4psi with the S5 setup. I did see spikes up to 1.4 psi with my old S4 setup.

 

A bridge port closes its ports pretty much identical to a 4 port street port. Its the earlier opening time that gains the power. A 6 port closes later than nearly any other port, and really needs a VDI system to re-gain the back pulse created, and also creates positive pressure in the intake. This does not in my opinion make for a more powerful setup due to this pressure. Its just a function of the design.

 

one of my buddies had an s5, all stock except the true duals, and if he went WOT, while you're standing behind the car, you can actually HEAR a pitch change when the 6 ports open, and then again when the vdi opens.

i'm not sure how much vdi GAINS, but you can feel it when its not working

 

Stock S4 NA gets 100mmHg boost (nearly 2psi) according to the J. Yamaguchi book on 2nd gens.

Placement of the vaccum/boost reference line is going to have a large effect on how much of the dynamic pressure wave you are able to measure.

I know when I was running my TII w/ 3rd gen UIM on it naturally aspirated I had the MAP line on the primary runners right at bend before the LIM and I would see positive pressure.

I moved the MAP line to the throttle body location to help smooth the signal for ease of tuning.

 

Because of the late closing the rotor is now compressing the air in the cumbustion chamber and a little of that compressed air and fuel is pushed back into the manifold and forcing air into the begining of the opposing rotors intake stroke. Creating positive manifold pressure and a small boost in performance, but on setups like mine (48IDA 6port) where the rotors intake tracks are totally separate, the late closing is only hindering performance because of the unused intake reversion. Is this assumption correct? Is it time for me to trash my built 6port and build a 4port bridgeport? If so how was kahren able to make 200whp on a stock ported s5 na with that crazy custom manifold? Could the lateclosing still help get air into the primary runner on the same runner?

 

the most i made on a completely stock 6 port was 180 at the wheels.
the 195 whp was on ported 6 port, my stage 1 port, that also ran out of fuel up top and hindered power output, with enough fuel it should have made about 205-210 whp with that same port.

the stock 6 port late closing is not THAT late to actually create that much pressure to make that positive pressure, so as long as you dont make the stock 6 port closing ANY higher you are OK, if you want to use it. IMO everytime you have a chance to use the 4 port side plates you should, though the turbo 2 port runners are not very big on the secondary ports and that will hinder performance to a point, unlike the FD where the secondary runner is a good size.

i haven't dynoed a 4 port with na rotors yet, but my assumption is that it will make very similar peak power to a 6 port engine. the aux port just isnt shaped that well for flow and that hinders some performance, and the 4 port doesnt have enough cross section in its runner up to the port to make great peak power numbers either, but its a nicer shaped, one larger, runner then the 6 port secondary and aux.

so to sum it up
imo the 6 port properly ported will show a tad better peak numbers due to more area in the runners, and the 4 port a tad less, because of this, but it makes up some with the better shaped port. the 4 port engine will make more low end due to the port closing being much earlier, even ported some.

....

ms7 at http://www.motivefab.com makes some 6 port inserts to help the flow in the aux runner, would be nice to see someone dyno before and after this product

 

so what happened? did you abandon the project or are you still working on it? was it the pump? injectors? both? just curious ... i like your work/projects.

 

it was on stock s4 ecu, and i guess it only lets the injectors run up to like 80% or so, since 460 should be enough for more then 195 whp. here is the link to that thread i talk about it there, https://www.rx7club.com/time-slips-dyno-128/na-6port-streetport-dynoed-195whp-update-418805/

there just aren't a lot of 6 port ported rebuilds that i do due to low demand and there are very few that are willing to go to the dyno. Most people build a turbo car and spend more money on that and i can only spend so much of my time and resources doing he testing on my own.

ps
i actually have one of these 6 port engines for sale with the stage1 port that is good for 200+ whp with proper setup https://www.rx7club.com/2nd-generation-rx-7-1986-1992-parts-194/fs-s5-na-engine-800880/

 

oh yeah ... that thread is one of my staple references! thought it was another project you were working on. i honestly didn't realize that it wasn't your own car, which is why i asked what seems to be a retarded question in my last post.

 

Those are the inserts that motive fab sells. Now why would theirs be any better than pineapples. Those things have been argued to death and noone had ever dyno'd before and after them and noone has ever flow bench tested them.
So why am I getting such low numbers then? My tq falls flat on it's *** at 5500 RPM

My Tq falls off at 5500 rpm. that's with 13.2:1 afs all theway through. 13b s4 internals, Gslse end plates and housings, 12a Y plate intermed. 48 ida, RB header, presilence, 2.25 silencer back straight through exhaust. light fly, Mallory DF ignition w/ FC coil.

 

Is it my exhasut that's causing my tq to fall off like that?

 

the pineapple inserts go inside the 6 port sleeves themselves, the sleeves themselves take away from overall cross section of the aux port runner diameter, since they fill some of the space where air could be traveling, plus the fork that actuates them and the shaft that is on the 6 port sleeve that the fork goes onto.

the motive fab doesnt go into the 6 port sleeves, it goes inside the 6 port runner, and the 6 port actuation is no longer functioning loosing some low end, but making up for it up top. i like this more, in this case i would sacrifice some low end for the better top end.

peak power is usually right around 12.8 afr, i found that you loose power from 13:0 and higher, negligible but you do start loosing it, if you don't, then your timing curve is not optimal.

the gsl-se aux port is smaller then the fc aux port, that looses some power, if the intermediate plate is stock 12a thats also pretty small, the twin 48mm is also smaller then the stock fc throttle body (3 of 40mm plates equates to more area then twin 48)

2.25" exhaust is probably the least restrictive thing here, but i find less then 2.5 inch starts to loose power around 150-200 whp on rotary.

so if you sum all this up you can see why the tq starts falling off early, check your timing, if you are running 87 octane, 25 deg at wot is a good place to start.

 

The 12a Y plate has huge ports and runners, thats why it was used in the build. 12.8 afrs huh, ive always heard people say they made the most power at 14.2 At my most recent dyno I picked up 3 ftlbs and 5whp @5k by leaning from 12.8 to 13.5. Are you saying to set timing to fire 25* BTDC? Im running a dizzy w/o vac advance, just the mechanical is working, but I set timing at 3500 rpm its fully advanced by 2800. I still for the life of me cannot figure out advance and retard, or what they do...

 

s5 13b with street port
weber 48 IDA
free flowing exhaust
158 rwhp and 117 tq

..... in a miata

 

Talking about the six port here.

I don't know if this is entirely true when the aux ports are open, Rotary God had another explanation. He seemed to believe, unless I misunderstood him on this, that the closing of the primary end plate port caused a back-up of pressure that then forced air into the aux port right above it (when open).

If this effect is true, I wonder if the effect could be capitalized upon be removing the division between the aux port and primary port in the LIM. Thus giving the wave of pressure a shorter path into the aux port. Just a thought.

 

that would be the first place to look....

how long is the header? what kinda muffler?

air fuel seems to vary a bit car to car, and port to port. USUALLY the (stock carb 12a's, stock efi 13b's) like to be in the mid 12's in the low rpms, and lean out into the low 13's up top. i have seen some combo's that are different

timing is going to vary a little too, better the ve the less you're going to need, generally. a stock efi 13b likes to be about 26btdc.

mechanical advance is simple. there are a couple of weights and springs, when rpm goes up, centripetal force forces the weights out and advances the timing. how much and when depends on the distributor # you have.

the do this cause the best timing at idle is different that it is at high rpm.

 

The carb might also be choking the engine. Remember that the stock TB has 3x45mm butterflies, MORE area than a 2 barrel 48mm one, which will have smaller venturies, potentially limiting the engine.

 

It's just a regular rb street header with a presilence, then 2.25 to a resonater and an Apex N1.. really loud and straight through! lol... I think My timming might be off. I think L is at 20*btdc and t 12*btdc at full advance. no vacuum just mech advance.

 

Locate the Vacc solenoid on the distributer responsible for trailing. It will be the one closest to the driver shock tower. loosen Both screws, and pull the trailing to 15-16* btdc, with the leading at 20*. This will put you at 4-5 degrees split. And as Kahren already stated, 22-25 degrees is most likely where the engine will make good power.

 

Hey Kahren, would you want to sell that SR flywheel separately?

 

Can someone try to explain how the rotary split makes more power and what numbers are good in that sense. Thats the only area I'm not sure about.