fitzwarryne

There are numerous options available for achieving 200rwhp in a daily driver. Assuming its to go into an early non efi RX-7, what are advantages and disadvantages of each one? After four years on the Forum I have my ideas, but would really value all comment from people who have tried an option.
12A bridgeport
12A carb with large turbo,
12A carb streetport with medium turbo
12AT with intercooler
13B carby 4 port with half bridge
13B efi 6 port with large aftermarket turbo
13BT with larger turbo

An output of 200 rwhp seems to be a watershed, and there are so many modification options available. Above this its various levels of 13BT up to 500rwhp and still streetable, below 200 the 12A appears to be a good option

Midwest 7's

iTrader: (4)

i say bridge a 4-port 13b with a 51 IDA.

85rotarypower

Swap a TII drivetrain in and carb it. Good for 200 hp easy (mabey more) and mid 13s mabey even low 13s if your a good driver and have good tires.

Oh yeah, I think it should be mentioned that bridgeports are generally not very good for a daily driver. Your gas mileage will SUCK (10 mpg, mabey 12 if your lucky), and it will be hard to drive. They also tend to like idling at 1200-1500 rpm.

Rotarx7

iTrader: (3)

why does everyone keep saying that bridgeports and pports are soo hard to drive???
yeah theyre louder and dont really have much low end speed but that doesnt make it HARD to drive does it?
i dont think so

85rotarypower

I think its the fact that they have so little low end torque that makes them hard to drive. I can't really say from experience, but thats just what I read when I was thinking of going with a bridgeport. Max power isn't made untill like 8500 rpm-9000 rpm, so you have to get special lightened and clearenced rotors and hardened stationary gears to handle the engine speed. You also have to underdrive the alternator and water pump to prevent damage. It may seem like its cheaper to just port your engine, and it is when your just streetporting, but when you get into bridgeporting or even a peripheral port, things get expensive fast. A turbo is much cheaper and will net more horsepower and slightly better gas mileage and you won't have to rev the engine out to 8500+ rpm to get max power.

moremazda

iTrader: (4)

I agree with '85rotorypower, in order to use a bridge port to it's full potential you must prepare the motor for high rpm use, and then use it in the high revs.

My oppinion for for a 200hp street setup would be a street ported 13b 4port with s5 rotors, a Holly down draft, and the Racing Beat dual exhaust. Take the extra money that you would throw at a turbo and put it into a nitrous oxide setup, to the tune of ~100hp. Now you have a nice reliable motor that will net you at least 13sec quater time, until you learn how to drive. After that you might very well be in the high 12's.

Ryan

peejay

200 horsepower at the wheels will have you in the 12's, unless you are really babying the thing.

Directfreak

iTrader: (2)

Maybe if he is an AMAZING Driver with PERFECT Traction,
and a Full Wet Weight of 2200 lbs or less (with Driver).

All Very Unlikely.

DriveFast7

iTrader: (1)

Because with so much intake/exhaust overlap the motors kick and buck below 4,000rpms. And to make good power gotta have loud exhaust. Spoken from experience and current owner, see sig.

diabolical1

iTrader: (3)

12A carb streetport with medium turbo

from your list, i think this would be your best bet for the street in terms of achieving your goals and cost. however, i think you have a few other 13B options than what you listed.

cosmok123

no answer here but where would one go to find out about turning a 6 port 13b into a turbo motor?

FB II

second gen section

peejay

200 hp at wheels is about 230-240 at the crank. (Bridgeport territory - a big street port might be able to squeak the number but will have a narrower power band)

I calculate that this should be able to net you a 12.8 at 107ish (comfortably in the 12's, no 12.999 which is BS) at 2500lb weight with driver and fuel.

At 2200lb, now we're talking low 12's, one-teens MPH.

peejay

Well you have a J-bridge, which is probably the worst possible scenario - large bridge ports have way lots more port timing than an equivalent-power peripheral port, because the ports are still mostly coming in from the sides so that needs to be crutched. The later closing (compared to damned near anything except a huge street port) hurts low-end power, the much earlier opening (even compared to a P-port!) hurts low throttle position power, which is exacerbated by exhaust restriction. Your exhaust ports probably open much earlier than stock (MFR P-port exhausts open *later* than stock!) which increases exhaust noise to boot, making the whole restriction problem even worse. To top it off, you have more runner area (than a P-port) so you have lower intake velocity meaning even poorer low RPM runnability.

I bet it's still big fat ear to ear grins

BTW - Mazda recommended a 1000rpm idle for the MFR-housing engines. And they'd do it fairly smoothly to boot. All the port face area without the excessive timing, and good port velocity.

- Pete (not that I'm championing peripheral ports or anything we're taking bets that mine could idle well at 800-900 if I wanted it to)

calvinpaul

iTrader: (2)

Hey peejay, have you gotten that thing on a dino yet? I am trying to deside between bp and pp, but I don't want to pay for the crap that comes with revving over 7-9k.

peejay

I'll probably never run on a dyno. That costs money, one dyno session can pay for two or three rallycross events, or six-eight drag race events! You can learn a lot more from six to eight test and tune nights than you could from one dyno session.

We might be getting a dyno cell at work, though. If we do, I might wheedle into getting some time on it every now and then! I'd have to make my own adapters, though, I don't think Superflow or whoever makes a Mazda rotary bolt pattern adapter.

And before it does anything, it needs to be completed and assembled I *was* shooting for April 1 as the deadline for the engine to run on the run stand, but now I'll be happy if I get it in the car by late May.

calvinpaul

iTrader: (2)

Oh, I thought you had it running already...sorry to hear. So you will not tune it on a dyno? What do you use to tune besides a timing light and a wideband? And how do you set the timing on a pp or bridge?

peejay

WIDEBAND? Eh???

Sorry you must have mistaken me for someone with more money than sense! And given that a lot of people say I have very little sense, that should tell you how much money I have available to put into a car...

Rough tuning can be done by ear/feel, after that it's time to go to the dragstrip and quantify what the engine likes. A little scientific method and you WILL get the thing tuned better than you ever could on a dyno, or at least a dyno real people could afford! Why is that? Because on the dragstrip your tuning *automatically* takes into account the car's acceleration through the gears, aero loading, chassis idisyncracies, etc, because you are tuning for what makes the car QUICKEST and FASTEST, not what merely makes the most power. You are ALSO going to be tuning the chassis, and MOST IMPORTANTLY you will be tuning the DRIVER! See Directfreak's comment re: perfect driver. NO driver is "PERFECT" but you can get damned close just by practicing, and learning, and you don't get driving practice and knowledge by throwing money at the dyno operator. And being a good DRIVER is key, since cars don't drive themselves.

Riddle me this: How often do you see cars post huge dyno numbers but on the track they get waxed left right and center?

RexRyder

iTrader: (10)

just go with a 13bt

diabolical1

iTrader: (3)

this should be put in NEON lights on the home page ...
i'm not going to swear off dyno-tuning, because i simply don't have the same knowledge-base as peejay - and i doubt many people do - but it is so refreshing to see that i'm not the only that thinks dyno-tuning is overrated! the stench of the elitism that goes with numbers chokes me to death in the Gen III forum and on the MR2 forum. as i said, i'll probably do a few runs when i get the MR2 out of storage next year, but the Rx-7 probably won't see a dyno until the EFI goes in.

DriveFast7

iTrader: (1)

I tuned my carb and set my timing to best power in 8 dyno runs. I do like dynotuning.

It would have taken several weekends on the track with my air/fuel meter to do the same. Dyno $ was worth it for me. I don't brag my hp $, just simply state it and move on.

mikey D

direct freak is right


200whp will not run a 12 second quarter

i had 250whp good traction and ran 12's@113mph in a very very gutted car
about the weight direct freak specified.

if your using a calculator thats why your wrong.

they dont consider drag, drivers, suspension, traction, weight of spinning things like wheels, flywheels, gearing, which all make a huge differance in the performance of a car.



Why does no one ever consider a streetport 13b 4port with 90 High compression NA rotors....that will give great power, great drivability and great longevity.

DriveFast7

iTrader: (1)

Agreed, that's what's in my REPU except for stock heavy lower compression rotors

camocarl

iTrader: (5)

Seems to me, appox 200 HP could be achieved with a streetported 91 S5 engine with a good induction system and exhaust? And be reliable? Thoughts? Thats what Im doing right now, I rather avoid turbo all together because of the problems that come with them and expenses.

85rotarypower

yes, 200 FWHP is definately attainable. According to RB website, a stockport 6 port 13B is capable of 180 FWHP with a holley 600 carb and proper exhaust. Depending on how big the ports are, port timing and all other variables, I think 220 FWHP is possible on a 6 port 13B. Possibly even 230 if your real good at tuning.