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I'm trying to use a series 6 rx7 block but run it NA. I'm wondering if any one here has done it or knows of any info on making this work with no adapter plates needs to be as smooth as I'm setting up a street drag car and wana know all about this.
any help I'd appreciate it or a steer in a direction.
Welcome. I moved this into the new member tech section. You'll get more responses here. Also do a search and see if the question has been asked in the past. If not, try posting in the 3rd Gen tech section as well.
I can't help you on import rules and exchange rates to New Zealand, but you do have a few bolt-on options.
1. complete OEM intake
2. You can get a Weber IDA manifold from Racing Beat or Mazdatrix (it's RB either way)
3. You can get Holley-type intakes from a couple sources. RxParts is one, and I know there is at least one other out there, but it's been a while since I've had to think about these things, so I can't remember the company.
4. Of course you can always use the Xcessive or OEM lower and have a custom upper built to your specs.
I have no idea what your plans are, but I guess it's worth mentioning that both Xcessive and RxParts offer manifolds for semi-PP setups as well, so I'm just putting that out there.
Stock cleaned up 13B-REW intake doesn't actually do that bad NA on stock ports, but weighs 20Lbs.
Projay has several style intake manifolds for the 13B-REW. These are meant for big turbo drag cars, but would work for NA. The lower intake manifold and a 4150 TB would probably provide the best throttle response VS a big single plate TB.
You can fill in the auxiliary semi-peripheral port on the intake manifold if not using it.
A simple/cheapest set-up would be a
$255 JW lower intake manifold https://www.jegs.com/i/JW-Performanc...97002/10002/-1
$160 PCE138.1002 4150 throttle body (on ebay)
$100 boost hat (many styles)
$100 primary fuel rail for EV14 injectors (many styles)
$350 2x 1,000cc to 2,000cc EV14 injectors or even stock primary rail modified for the stock 850cc secondaries (limited to ~220rwhp depending on fuel pressure).
$1,000 ECU of your choice
another possible option?
I don't know how this will pan out once driving- self learning ECUs haven't been able to add enough "throttle pump" in the past for big throttle transitions when driving.
$255 JW lower intake
$1,400 Holley Sniper/Stealth ECU/TB
$100 boost hat
I believe the wrap around Webber DCOE style intake manifolds can make a bit more power, but I can't recall seeing one for 13B-REW. Would have to cut modify to fit. I think the Star Mazda one is the best base.
Rotor compression ratio over 13B-REW 9.0 won't help peak power (actually lower is better for high rpm power), but will definitely help throttle response/driveability.
Are you thinking stock port/unopened 13B-REW or with some port?
Anniversary Racing Factory (A-RF) specializes in NA rotaries.
You can get a feel for how much aftermarket intake manifold helps over the stock 13B-REW from this dyno page that lists mods-
FWIW since you intend to go N/A, the REW was only 9.0 compression. The earlier N/A engines were higher. ,IIRC, either 9.4 or 9.7.
And “street drag car”?
You'll definately need S5 NA rotors at the 9.7 compression ratio. 89-91 years
Then a rebuild kit, resurface housings and irons
Also a standalone ECU Haltech, Adaptronics, etc. Possibly a street port?
Exhaust, Intake. You have enough fuel from the stock FD fuel system.
Its possible to make a 200+ RWHP 13BREW NA but cost money. It will be loud. NA rotaries are loud.
For the money spent you could go for a single turbo conversion over the stock twins.
Then again RX8 is a modern day non turbo FC. Better chassis and suspension over the FD RX7.
Again, you can skip the 9.7 rotors if it means spending $ in places where it will make more power such as intake manifold or exhaust. The 9.0 13B-REW are already the lightweight rotors like the 9.7 rotors and I believe the newer '99 up high power 13B-REW has narrower rotors already so they are even more reliable at high rpm.
The high compression rotors do help throttle response, will help midrange power and fuel economy.
Compression ratio on the rotary doesn't work the same as compression ratio on the piston engine because the rotor tub is also the transfer port on the rotary to get the compression stroke trapped above the pinch in the rotor housing (trailing plug area) across the pinch in the rotor housing (to leading plug area). At higher rpm the gains in power from increasing compression are lost in the additional pumping losses of flowing the charge through the restriction in the smaller rotor tub.
Here are some Mazda charts. See how BMEP gains from increased compression ratio are negated after 6,000rpm? Most NA rotaries will make peak power well after 6,000rpm.
That sort of fits in line with what I have casually observed before on two points:
1. I have seen several motors with the 9.0s making good power in NA applications - both in numbers and in the curve
2. I remember when everyone and their mother were scooping up the MSP rotors for their NA builds and the numbers were not spectacular. In fact I recall at least one case where the person eventually ditched the Renesis rotors and put some 9.7s and then made more power.
Also, just an aside ... JW was the one I was trying to remember earlier.
12-05-18, 03:00 AM
