j9fd3s

iTrader: (3)

its not needed, stock fuel cut is like 7800 on an S4, and S5's have hardened gears stock.

diabolical1

iTrader: (3)

^ agreed.

also, just to piggyback off of j9fd3s' post. your intended redline doesn't warrant it. i mean, you can get them if you see them and the prices are right, but i wouldn't hold up the build, waiting on them for 7500 to 8000 RPM. so that's one thing.

another thing is i think you have to be a little careful looking for Rx-8 gears, because during the S1 run, i'm not certain the automatics (the 4 port engines) had hardened gears. the manual cars definitely did. they had the hardened gears and 3-window bearings. just something to look into if you're still thinking of going that route anyway.

question: that's all engines? i thought i had read that it was only the turbos.

j9fd3s

iTrader: (3)

For the S5's they all have the same part numbers, N370-10-E00C and N370-10-E10B
for the Rx8 they do have different gears for the manual and at, the automatic ones just use the same bearing as the FC does, so if one did decide to use these, they need to be the right ones to be an upgrade.

FD gears are hardened and multi window and all the good stuff, but will drop right in, so that is the easy option

GeenIdee

I'd like to drop in on this subject as I'm also planning a NA build.

My original plan was using an S5 TII engine and use 6-port front and rear irons. My thought process was for NA the extra aux ports would help the engine breath better but still retain somewhat normal drivability. But to me the intake looks restrictive. Also, I cannot find any information on comparisons between the sleeved 6-port and the non-sleeved 6-port. I can't even seem to find out when the sleeved version is used and when the non-sleeved version is used. I am guessing the sleeved version has bigger (manifold) runners then the non sleeved version but the sleeve and actuator rod take in some space also.

And for who doesn't get what I mean with the non-sleeved engine, it has butterfly valves in the manifold instead of the sleeve in the irons.

WondrousBread

The "sleeved" and "non-sleeved" you're referring to depends on whether it's USDM or not.

European 6 port cars have the butterfly valves in the manifold. This is the "non-sleeved", as you put it. I don't know offhand though if the irons are actually different though, or if they're the same irons.

This is a good point however, since a limitation with the aux ports is that they have a flat "wall" at the end transitioning into the combustion chamber and not a radiused bend. If the European 6 port irons have a radiused bend instead (since they don't have the sleeve occupying that location), then that could be quite interesting.

Not sure what the implications are for power vis-a-vis the USDM irons though.

EDIT: There are a few pictures available, but I'm still not clear whether the bends are just not machined out on the EU irons or if they're actually a different casting. Here:

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/aux-port-butterfly-valve-conversion-322606/

https://www.rx7club.com/naturally-aspirated-performance-forum-220/6-port-daily-driver-engine-1023918/page2/

Dak

​​​​​​​From everything I've read in this section of the forum Naturally Aspirated Performance Forum - RX7Club.com - Mazda RX7 Forum if you have a S5 TII engine and it has usable irons you would be better off to build it with a street port and set it up n/a. The 4-port engines are a better base to start with. Even though it looks like the 6-port would make more power from those secondary ports people make more power with the TII blocks ran n/a. More links
S4 Turbo Running NA or S4 6-Port on ITB - RX7Club.com - Mazda RX7 Forum
The video in this one is pretty informative:
Rotary Port Evolution - video - RX7Club.com - Mazda RX7 Forum

SPENT-IT

iTrader: (15)

Semi-PP housings
Fill AUX ports with Devcon.
Bridge port primary and secondary.
Call it a day.

If you want to get fancy put Semi port up at desired closing timing.

GeenIdee

Good find. Perhaps the us version is bored out to accept the sleeve?
I've had the LIM in my hands en the runners look pretty small though




That's what I've been hearing, and because that is being said, "it is the easy choice" for many i feel like. Also, because I overthink many things, I start wondering, is this literally the better choice or are these results because people cannot seem to port them the right way? Either due to knowledge or not having the ability to shape them the right way without blowing trough?

I've seen all 3 vids, lots of info very quickly and my head had a hard time keeping up. I probable need to watch it a few more times but most testing was done on stock ports and not necessarily on what can be achieved.
Runner shape is where it's at, same as with a cilinder head. But it's a difficult subject if your not working with it frequently.

diabolical1

iTrader: (3)

with all due respect, i'm sure just as many guys put work (blood, sweat, tears, and of course, CASH) into making N/A power with 6-ports, as there are guys that did the 4-port engines. if there was going to be a beak-through, it would likely have happened already. it's been 38 years - at least, here in the US since we've had them. that doesn't count the magicians in Puerto Rico, Australia and New Zealand. someone would have cracked the code if it were going to be cracked. actually, let me back up a second, someone did ... Mazda! however, that's a discussion for another time and place.

the 6-port has a place. it is a significant engine, and i have love for it. it does what it was designed to do, and it does it fairly well. it is flawed to some extent, but it will respond to porting. it will respond to changes in intake manifold design and intake dynamics. it just doesn't seem to do so as favorably as an equivalent 4-port.

Dak

From most posts I've seen on here most people seem to build what they have so there have been more ported n/a 6ports built than 4 ports. At least here in the U.S. Not many taking turbos off of TII engines and going n/a. The few that have built 4-ports seem to have better results than with the 6-port. I don't think it is lack of ability but that the 6-port is flawed. The aux port closing is very late, but the velocity is low so it struggles to fill the chamber so porting the aux ports doesn't gain much.
From what I've read the two small runners leading to the ports is part of the problem as well.
Basically, try not to overthink it. If you have a usable 4-port it is the way to go.

j9fd3s

iTrader: (3)

had to get the shovel out for these,
from https://www.rx7club.com/2nd-generati...3/#post1586101
and https://www.rx7club.com/2nd-generati...e2/#post352668

"Yes, we are running the E/Production engine to 10k -
Do NOT try this at home, experienced (not PRO, since it's amateur racing) driver on closed course.

The SCCA rules dictate "street port" 6-port engine (meaning not bridge), so the ports are VERY large.

With VERY large ports, and absurd port timing, you get an engine that ONLY works at VERY high revs. That is why the exhaust is single, and large. -- but the dyno said it still wanted fairly small primary pipes.
Sooo - everything had to be done to attempt keeping it together that high.
Off the top of my head:
VERY lightened rotors (STARTING with lightest ones)
side cut rotors
ceramic apex seals
hardened gears
competition rotor bearings
3-window rear bearing
93 style front bearing
oil shooters in the eccentric modified
oil passages "flowed"
oil pump massaged
3 lb flywheel (yes, three)
lightened counter weights
5 1/2" double disc clutch
MSD 7AL's
Mallory coils
VERY balanced assembly
competition thrust bearings
2 oil coolers
HUGE radiator
52 mm IDA carb
very short manifold
it liked a VERY long exhaust
smallest eccentric pulley
largest water pump pulley and alternator pulley
restrictor in water hose

+ other stuff?

AND it STILL scrares the crap out of me everytime I see 10k on the tach !!

Dave Lemon
http://www.mazdatrix.com/faq/epconv.htm"

"Mazda (and about all other manufacturers) invented variable port timing (for us- 6-ports, 89 intake, etc)to spread the usable power/torque over a wider range.

In the race engines we do, the torque usually is peaked at the lowest rpm we are concerned about (meaning actually somewhere BELOW there). A "Pro7" 12A has a torque peak at 5000? (where we START the dyno run), and an HP peak usually about 7000. The E/Production 6-port we are testing now has a torque peak at 6000 (where we START the dyno run!!) and we (so far) can not find the power peak!! By this I mean my dyno tach only goes to 10,000 and the engine is still GAINING HP at that rpm!!

This all means that, in the Rotary (racing) world, we pretty much ignore the torque peak (too low to use), and work only with the HP/rpm curve.

The whole key (in semi-tech/math terms) is to maximize the AREA under the HP/RPM graph for the rpm spread you need for your specific RPM splits/drop between shifts. This gives you the most available/usable HORSEPOWER for the rpm range you are using.

A "Pro7" engine (for example):
RPM Torque HP
5.0k 127 121
5.5k 125 131
6.0k 121 138
7.0k 111 148
8.0k 92 140
8.5k 84 136

With those numbers, and needing a little more than 2700 rpm split between shifts, you shift about 8500 (136hp) and the next gear comes in about 135hp. Because the rules for that class require steel apex seals, we use about 8500 as the upper limit for hoping the engine stays together.

We are not sure what we are going to be doing with the E/P 13B 6-port. If we hope the HP PEAK is (only?) 10,000, and an rpm range of about 2000 (close ratio box) then we would need to shift somewhere about 10,600 ??? and we are not at all confident the engine will stay together at that rpm.
This last writing is basically in answer to the post quoting all my writing (done YEARS ago) on testing 6-port engines. Since we now have a reason to "waste?" all the time and $$ playing with it on the dyno, it is nice to know I was pretty much on the mark all those years ago. -- meaning the intake port timing is SO late, and the port volume so HUGE, the max HP is WAY up there in rpm.

And no,we do not "ignore" the torque curve/peak. By playing with all the variables, we are always trying to raise the peak as high as possible, and "flatten" the torque curve as much as possible."

"Been there, done that, DOING it right now ---
Big end ports, custom manifold (long runners, MANY hours to fabricate - didn't work), etc etc.
Literally just finished a run (1/2 hour ago) with SHORT primaries, BIG pipe, comp muffler (didn't work quite as well as LONG primaries, but not all that bad)--- there was no hp "curve" just a straight line -- starting at 6000rpm it simply just kept gaining power till I stopped the run at 10,000rpm!!

Oh well, I'll invent some more things to try in the next few days. We are trying to get it to peak about 9-9.5k with as much as possible about 7k.

Btw, this is all with a 52mm Weber IDA downdraft, with 38mm chokes (as E/P carb rules require - it is SO much simpler than the injection).

That last run actually HAD a torque peak -- 7k instead of the 6k we usually see where we start the "pulls". Nice find out about where the torque was.

Dave --"

GeenIdee

That's a fair point


I have nothing laying around besides 2 4-port reni's that I'm not going to use for this one.
So I can go all directions whether it is something proven or try something new. Try to give it my best getting high hp street car. No rules to worry about, budget probable lol


Wanted to stay away from P.P. to keep some low end, but actually, a valved semi-pp might not be to bad of an idea. But if I decide to go that route, what would be the best engine to use as a base (port wise).

j9fd3s

iTrader: (3)

just go full PP, its streetable and makes more power than anything else everywhere when the throttle is open. its part throttle low rpm where the PP isn't happy, but that is pretty much it

if you want to drive around at part throttle then the Rx8 engine is actually really good. there is a guy in the 1st gen section with a 4 port and holley its making 230rwhp... that is only 30hp away from the PP....
https://www.rx7club.com/1st-gen-gene.../#post12465083

Holdfast

I have a ida peirce manifold that is identical to the rb manifold. With throttle body injection low end power and torque is greatly improved. It pulls hard through the whole power band. Rotary's work really good with EFI. The engine doesn't have steady vacuum at low rpm. It has pulses. Carbs like steady vacuum to work well at low rpm. EFI doesn't need vacuum to work well. So power is great at low rpm with EFI