Alak

iTrader: (9)

Okay, so I been researching alot and now its time to get opinions.

Im going to be building a High RPM (Not Power) Motor and I need advice and opinions. Motor WILL BE N/A and Carbureted.

Rotating Assembly is going to be S4 N/A as I already have one with lightened rotors, Etc.

My first build was going to be a 4-Port Turbo block Bridge-Port pri and sec. Obviously using Hardened gears etc.

I did some research and some guys are using a 6-port setup. The secondaries are 'Street Ported' and the primaries are Bridge-Ported. They say the advantage to the 6-port setup is that the timing of the sec. ports is better for high RPM (10k+) applications.

Would some of you be inclined to agree? I mean, 4-Port (as we all know) flows like a hooker on the rag. But if timing is so important, would 6-port be the way to go? Im not looking to crack HUGE HP numbers here, but 200+ HP would be acceptable to say the least. (I've seen Carbed BP push over 300).


Any thoughts from anyone? And no, Im not going turbo. :smiley_12

I wanna do this once and right.

Rancid7

Just curious .. why do you need to build a high rpm engine ? do you want 200 hp or do you want to rev high ? i dont see the point in overreving an engine if you can get peak power at say 6500-7000 why do you need to rev higher ? what benefits do you gain from this . Im not trying to flame im just trying to understand what it is that you want to accomplish from a "high" revving engine that produces 200 hp at 6500-7500 wich i dont consider high revving for a rotary . i dont see why you need to rev past 8 grand to see 200 hp . most likely at 8k power would start falling off and i'd be a waste . maybe im lost .

Apathy

Maybe he wants to build a nice drift car with a higher powerband... but then he should keep it turbo? I dont know... I know that when I rebuilt the engine on my last rex, all I did was a mild street port and 3mm atkins apex seals and that was good enough for reving to 11k, wasnt turbo though. With proper tuning, it had steady power all the way up to 10k. Plus having a high rpm engine, with a lightened flywheel will make for crazy accel.

Rancid7

yeah but a power band is a power band , what does rpm have to do with it . If you peak at 6500 are you saying that isnt any good to drift ? do you need to be a 8000rpm or higher to drift ? im really not understanding this thread . and you were revving to 11k but where you making any power up there ? i don't think you were . im really not flaming . I JUST WANT TO UNDERSTAND .

Rancid7

to try to answer you question . Im no expert but if you want to build a "high" rpm na . I'd use rotors out of an 89-91 na and since you want it to be carb'd maybe get a weber ida set-up . I'd also throw in a clutch and flywheel that can handle the revs that you plan throw at it . Im sure there are some internal mods that can be done to the engine to keep the oil flowing smoothly etc etc but unfortunatley i'm not eductated enough in rotary engine building to advise you further in that area . anyway good luck with your project , hopefully better educated and experience rotor heads can reply to this thread and advise you better .

Apathy

I was making significant power to 10k. Like I said, having a higher rpm engine w/ a lightened flywheel made for better accel. b/c you can hold the gears longer and the revs dont drop as fast. If you drift, you will know what I mean by dropping revs... Rev dropping is killer when you are dynamic drifting or shift lock drifting. Look at any of the D1 drift cars and you'll see that they are all high rpm cars. As for him not wanting the HP, I dont know about that. Its a combination of high HP, torque, and a nice steady high powerband that makes for perfect drifting. But I said drift car, b/c he only wants around 200+hp, my FC only had 210hp & w/ it stripped and lightened it wasnt too shabby for drifting. When I grad. from college, Im gonna build a real nice drift car.

Rancid7

ok thats makes sense , but like you said its a combination of high hp , tq , and a higher power band . i dont see how your power band can be so high with only 200 peak hp . Maybe with a bride-port and a weber ida set-up . OK im starting to see how this can happen .

Alak

iTrader: (9)

This will be a street car mainly. Im looking for a very high peak RPM/HP number. With a liniar powerband.

Example only, 250HP @ 12,000RPM.

Im not concerned about HP as I have an extremely fast miata to boot around in as my daily driver. I just want a different approach to HP in a rotary.

I have a Lightened S4 Rotating assembly including Aluminum Flywheel and whatnot. If I were to go S5 rotors, I might as well go RX-8 rotors.

S4 9.4:1 Compression
S5 9.7:1
RX-8 10:1

Its cheaper to get RX-8 rotors too if you buy em new. Im going to be using a 4-Barrel carburetor to maintain some low end performance and drive-ability.


So whats better for RPM performance? 6-Port or 4-Port?

Rancid7

i just went back and read the post and he's talking 10k+rpm though ! and yet 200 hp . This is an intersting thread . Hopefully the guru's will come in . I wanna see where this goes . maybe i'll learn something .

Alak

iTrader: (9)

I dont care how much power it makes. It could make 150 or 500HP. I thew that 200 in there for like an example. I just want the peak WAAAAAY up there. I want this motor to climb.

Rancid7

porting changes timing , and from what i've read on the forum the 4 port 13bt engines flow better than the 6 port na . And porting techniques are diff between turbo and na 13b . In theory if you ported a 13bt 4 port with na porting techniques then the outcome would probably be what your looking for . I think .

Rancid7

you ad a short runner intake like the racing beat and a 4 barrel and imm sure its gonna peak up high how you want .

Alak

iTrader: (9)

I read that the 6-Port has radically different timing. You could port the 4-Port and it would flow better, but the 6-Port still has more timing needed for RPM. At least thats what I read.

I'd like to use the RX-8 as an example - Transmission excluded in the example:

197HP @7500 RPM in the 4-Port version of the engine

238 @ what like 9000RPM? in the 6-Port verison.

WonkoTheSane

iTrader: (2)

Can't help you with the 4 or 6 port question, sorry. I can tell you for that range of power you're more likely to find a stand alone EFI solution that will give you a better tuneable/useable low end power than carb.. For example; I know my Megasquirt can control somewhere up to 22,500 RPM or 25,000 RPM or something of the sorts.. I'm sure a Haltech or MicroTech could do the same, but I've never got to see one.. The point is, by using EFI and staged injectors, you could really get a good flow going, then stage your larger secondaries for when you kick into powerband (~7500 RPM)?

Rancid7

We need some experts dropping knowledge on this thread . Now you have me intrested in wich is more effecient at making power at higher rpm's in NA trim . 4 or 6 ports , that is the million dollar question . I think Karen is the forum memebers name that was running a 13bt engine Na with i think a haltech and he was putting down almost 200 hp But i can't remember at what rpm . I think it was also a road race car and and obviously his goals were totally diff then yours . Im gonna try to find that thread .

Alak

iTrader: (9)

I'd do PP but the wear and tear is ferocius on the engine.


I think a goal of 300HP at over 10,000 RPM would be a start.

I'd do EFI, but its too complicated right now. I want to see what I can accomplish carby. Then go EFI after if I choose too.

I like to keep it simple.

Rancid7

https://www.rx7club.com/showthread.p...ighlight=karen
page 2
this might help . It also seems like Karen is the man to talk to . But i dont think 300 hp is going to be realistic without the "ferocious" PP BUt maybe 250 with a bridge . Who knows ! I bet Karen does . Pm him about this or send him a link to this thread .

Rancid7

Im thinkin a 13bt bridge ported to be na with 9.7:1 rotors , racing beat intake and your 4bbl or t2 manifolds with a stand alone might be your best bet .

Alak

iTrader: (9)

Im intruiged by this 6-Port Idea. I wish I could dig up the articles off these other sites that I read with these guys doing it. No power levels listed.


I think the 6-Ports flow is only inhibited when forced induction is involved.


I would also like to mention I've seen a PP 13B S5 do over 350 at the wheels on the dyno. BP isnt far behind in 4-Port fashion.


Anyone ever heard of anyone bridging a 6-port iron?

scathcart

Ask me some specific questions and I'll do my best to answer them.

A few quick thoughts, after glancing this thread:
1. RPM is RPM. Seals are seals.
12,000 rpm on a PP engine is going to wear out just as fast as 12,000 on a side-port/BP engine.
Only thing is, the PP will make more power.
PP's are far more reliable than Bridgeport engines. Bridegport engines are built when race rules don't allow for a PP. If you want a high-revving engine with a USABLE high-rpm power band, PP is the only way to go.

2. Full bridge 6-ports do exist. I have built one. I didn't like it.

3. If I had to keep side ports, I would go with a full bridge-4 port. But then again, for a engine who's only point is to rev, I'd build a PP.

Alak

iTrader: (9)

PP housings cost as much as my arm.

Home made PP housings last about a long as it takes to get them from the machine shop to your garage.

PP means I can't do alot of things I wanted to do and will cost SIGNIFICANTLY more $$.

I think a Bridge Primary plate and 6-port street port secondaries would be an interesting Idea running a 4-barrel carb. Then I dont have to track down 4-Port plates.

SonicRaT

iTrader: (6)

The 6ports have more port timing, the intermediate plates are the same. Yes, you can bridge a 6port secondary plate (I have, dDub has, Aaron Cake has, Ito, etc). In N/A form the 6port plates would be ideal with a nice short intake (IDA or similar would work very well)

Alak

iTrader: (9)

So the 6-Port High Revving motor would be a plausable Idea then?


Any more input anyone?


Forgot to add if theres any pics lying around.

scathcart

Home made PP housings not lasting is usually indicative of the builder making acute errors.

You think all the PP housings out there are MFR's? Everything is is essentially "homebuilt".

Alak

iTrader: (9)

All the Homemade PP housings around here are trash with the exception of one guys motor, which has 2 years of summer under its belt.

I've seen MFR's go for much longer.


I just dont want to buy another $400 header really. Or ruin good Irons. Or go weber intake. $$ adds up fast.