I am relatively new to the gen 2's. I am planning to use an s5 motor for a motorsports racing application. The engine must be n/a. Would there be a disadvantage in horse power gains by using a normally turboed motor as apposed to a normally n/aed motor. Thanks for your help.

 

you mean wether to take a S5 n/a or an S5 TII without the turbo?!
that would mean the S5 n/a is better 'cause it has 6 intake ports compared to the 4 of the TII, so the n/a has more potential!

 

depends what you do with it and the racing regulations

you can make better overall naturally aspirated power on the 4 port block if you port it correctly and use n/a rotors

 

How do you figure? Even when you port the 4-port to the max it still doesn't have as much port volume as a 6-port motor, especially a ported one. You would also have to mess with a custom intake manifold on the 4-port as well.

 

Thanks guys. You seem to have answered my question. I did not know that the turbo was only 4 port as opposed to the n/a's six. I do believe the n/a has higher compression rotors, is that correct?

 

they may have more port volume overall, and i'm not trying to dispute that because i simply don't know. however, two things: first, when ported, i think much of that deficit is made up over stock ports. second, in terms of flow, i thought the T2 housings, particularly the secondaries, were better when ported because of how ports 5/6 need to be handled. also, i've seen people use T2 engines (rotors included) in N/A applications and retain the stock manifold. it may not be the best for an N/A application, but i've seen dynos comfortably over 200 HP at the wheels when ported.


84-7GSL ~
yes, the N/A engines have higher compression compared to their T2 counterparts.

S4 engines: 8.5:1 vs. 9.4:1

S5 engines: 9.0:1 vs. 9.7:1

 

Really? The highest I've seen is Kahren's which was 196 or so with a custom manifold.
To the original poster, what do the regulations allow? Can you bridge it or use a standlaone, or does it need stock porting, or what? If its anything goes, I would say a 6port block with a full bridge, standalone, and ITBs is your best bet. Or a p-port if the regs allow it.

 

Wait wait wait. Sideways7...I'm almost positive the 4port, when ported, will wayyy overcome the 6port, when ported.

Now, if you CONVERT the 6port motor to a 4port via porting, YES, it will have more volume than the 4port(standard) motor.


Answer the regulations question, first.

What kind of racing are you going to be doing? Lots of straightaways? Very short straightaways, with most turns? Auto-X, etc?

 

Any type of porting is allowed. These guys know nothing about rotaries but I am going to make them allow me to use a rotary.

I am using a carburated stock motor or if I come across one that is ported fine, for simplicity and to find out if it is reasonably feasible to use a rotary for this. I will also need to get the most torgue that I can.

Its all out, full bore, hammer down and launch, similar to drag racing. I am using a rotary for its uniqueness and one-of-a-kindness that it will bring to this sport (please understand that I cant give full details on the sport) but at the same time I want to be competitive as well. Tim

 

I was under the impression that the 6-port can flow more than teh 4-port, but I've been proven wrong before. Anyone else care to shed their experience (not their blind guessing?)
To the original poster, since anything is allowed, it all comes down to how much money you have to spend. If you're on a budget (and you use the carb) then your best bet is a bridgeport. They can get expensive with FI since you need a standalone for them to run, but with a carb you don't need that. Be aware that it will likely no longer be very usable as a street car if you do that.
If you still want to drive it around town and such you should just get a large street port and call it a day.
Edit: just noticed that you said you were going to use the motor as is. In that case, get a header, some sort of cat replacement pipe, and pretty much any catback. If you carb it and get an exhaust system, the only ways left to get power are porting.

 

Thanks for the input people

I understand that with enough money and mods it can be made feasible but I want to see if I can be fairly competitive in stock form or with reasonably minor mods.

The vehicle will not be streetable and the exhaust will be totally open with no mufflers.

The hp increase of the stock s5 over the stock s4 is about 14hp. Would one see that kind of an increase in hp of the s5 vs. s4 by using the setup I want to use on those same motors (ie. carb and header)? Or would there not be that big of a hp increase in using the setup I described, between the 2 different motors.

 

if i recall correctly, the thing that made Kahren's achievement so significant was that he left the ports stock - a 6-port. he made a custom manifold and used a stock TB, then tuned with a standalone. i may stand corrected, but i think that's what i remember. i have a photo on my computer somewhere.

also, i'll try to dig up a link or two for some of the other guys that used T2 blocks in N/A applications. i don't remember coming across one that was NOT ported, so those 200+ numbers were all streetports, at least. i know for sure that one of them was on this board. i think i saw the others over on www.ausrotary.com.

 

I thought if you have a 6 port, running no mufflers would be bad for lack of back-pressure?

 

here's one at 193 WHP. i'll try to find one of the 200+ ones, but i'm only going to search for another few minutes. if it's a really big deal to you, i can try again some other time, but i honestly have no reason to lie about someone else's (strangers to me) dyno sheets. besides, i think i've hijacked this thread enough.

 

You did not hijack the tread, you just got me thinkin more.

 

okay here is one. i just ran a quick search and this was one of the cars i was talking about. it got 230+ HP at the flywheel. that should be just over 200 HP at the wheels (assuming 15% loss). however, i think i saw an Australian car that got a few more. keep in mind he used Weber-style TBs.

 

Ok, so that one was a GSL-SE motor (4 port) with s5 rotors. I never thought of looking in the 1st gen section, but I guess they are 4-ports. Anyway, the one I am thinking of was where Kahren had made a motor to be turboed but the customer decided to keep it NA, thus the 4 ports. It was streetported, had a custom manifold made by kahren and was tuned with an SAFC. I'll search a bit and try to dig it up.
Also, its not really that big of a deal to me, sorry if it sounded like I was saying you were lieing (lying?, whatever). Once I get the money to properly rebuild mine I'm aiming for 200 WHP with a 6port and stock intakes, but who knows.
Edit: it was a 6 port with a turbo manifold, apparently. Not sure where I got the idea it was a 4-port. Oh well.

 

no worries, mate. it's just that i get so used to people being quick to yell bullshit at anything that is not mainstream, so i guess i kinda felt the need to prove what i saw since i brought it up. that's all ...

if that Kahren motor you're trying to recall is the same one that i'm thinking of, i can't remember if it was posted here or at nopistons, but i did find the pic on my hard drive - just have to figure out to post it without linking from my photobucket account. at any rate, i'm in awe with that thing. still demands my respect.

EDIT
success!!!

by the way, as i alluded before, this is Kahren's work and his pic. i hope haven't offended or infringed on him or anyone else by posting it - if so, my apologies.

 

Wow, thats pretty crazy. You ahve a link to the thread about that motor? I'm curious about what was done and what it made. It looks like it has some sort if ITB rigged up.

 

here's one that he did, but i never saw this until now. wow!

Kahren-built N/A 186 HP

 

okay, final post and then i've got to go research some things for one of my projects ...

i think THIS is the thread that goes with the pic i posted before. all the pics are red-X'd out, but i'm pretty sure it was this thread.

enjoy and feel free to PM me if you want.

 

you got that confused a little, the street ported 4 port one had a haltech, it was basicly all turboII stuff except no turbo, and had a stage1 turbo street port. if it were to be na stage1 it shoudl have made even more power, and if it were to have 9.7 rotors that would help bring the power up even more.
here is the link to that thread again,
https://www.rx7club.com/showthread.p...nifold+dyno%2A

the 6 port street port, that ran out of fuel due to stock injectors and stock ecu made 195 whp that was with 9.7 rotors and afc with turbo 2 manifolds port matched to the 6 port engine, which i wouldn't take up on doing again, and woulnt reccomend anyone doing this as it takes very long time to properly shape the runners to fit the 6 port engine, the only reason that was done is because the owner wanted to run the stock turbo on that 6 port engine and as you know you need the low profile turboII intake manifolds for the factory turbo manifold to fit. i dont know why he wanted to do this, as with the stage1 street port the stock turbo would have been way too small, its easy enouf to max it out with the stock ports.
here is the link to that thread
https://www.rx7club.com/time-slips-dyno-128/na-6port-streetport-dynoed-195whp-update-418805/