So, I'm going to be starting my project here soon and I was wondering if anyone could give me some pointers on how to get the most low rpm torque out of an n/a.

Is there any port design that will increase torque in that area?
I'm guessing as far as intake goes ITBs are the best way to go but since it isn't a race car is there a manifold I can source out/modify a little bit to get shorter runner lengths w/o having to go with a carb?
Fuel management, I've seen quite a few dyno sheets of the gains from running a SAFC/wideband on an n/a.
Also, I know the six port system is supposed to help high rpm power and when you remove it low rpm drive ability is affected. (Don't try and argue otherwise because I removed the working vdi system off of a s5 and it felt horrible.) However, is the 4port design better for low rpm torque or is it best to stick with a six port/vdi system?

Any other ideas or thoughts on the matter are greatly appreciated.
This is in no way a race car, drift car, thrasher, etc. I'm going baby this one, but since it'll mostly by dd I want it to have enough torque to not feel like I've got to pound the gas to pull out in traffic.
Thanks.

 

Get one of these Euro LIM's





Instead of the rotating sleeves operated by exhaust backpressure, this LIM has these nice valves.

More info on the subject --

 

What The **** Is this ****?
4 Injectors,,, but Vacuum dizzy??
what other kinds of crazy are out there...?

 

If you want low end torque, you would want longer runners for the intake manifold, longer runners for the exhaust, seperated as far back as you can until it collects, and keep the stock ports. Any porting will move the powerband upwards in the RPM. ITBs and carbs will shift the powerband way up the rpm range. You will also have to have a smaller diameter pipe if you want more low-end compared to a bigger diameter. For low-end, long and small runners, for high end, short and big. Ive forgotten the diameter of the stock n/a intake, but the length of the runners are about 22inches??

Its all about trade offs, make the diameter too small, it will choke at high rpm from air resistance, but at low rpm, it will have better velocity for low-end grunt. Same thing with making it too long. And then theres the problem with the plenum, smaller one will resonate the air more pushing it into the chamber when it is open. I would think the effect is less dramatic if you had a VDI, which basically does the same thing.

pretty sure there isnt a huge difference between the 4 port and 6 port at low rpm torque wise. Many people use the 4 port for n/a because when ported the aperture and the bowl area has more working area to port out compared to a 6 port before you start hitting the coolant jacket, hence more power than a 6 port.

You can go read more into it in the N/A performance section of the Forum. More knowledgeable people there.

 

Check my Build Thread for more info on this

 

#1 is chamber sealing. compression leakage is why the rotary is down on low rpm power vs an equivalent piston engine in the first place. so this means new rotor housings, and if the budget allows rotors and irons too. its not cheap but it does work better.

if you stick with the 6 ports, the factory S5 intake non VDI path is already really long, making it longer will help the low end, but the midrange will get even softer.. i think with a 6 port doing a proper exhaust and ecu tune would be the best choice.

the 4 port engines with a small street port should have 200rwhp potential, the sub 2000rpm region will be softer than a 6 port, but from 2000-8000 the 4 port is better.

the best low rpm Tq setup is actually the PP, you have problems with noise and part throttle, but my 12A pp makes more Tq at 2000rpm than a stock 12A does at its peak, i could tow with it.

 

Do you use a semi pport or full pport though. I'd imagine full.

 

mine is full. unless its a turbo i don't see the point of going semi, the full P port drives better than you'd think with a carb and locked ignition, so an EFI P port should almost drive like stock

 

I remember seeing that in another one of your threads. Btw, respond to my pm :P

On topic: since that is the case, a custom long-runner ITB setup with staged injection might be a good starting point or no?

 

Whoops, had my intake logic backwards. Sorry.
But like the above poster said, long runner itb?
How is the driveability affected by itbs?

 

Stock NA parts are what you want for maximum low rpm power as this is what Mazda really concentrated on with the NAs. 6 port induction, VDI, stage throttle plate opening, long runner manifold- all that is for low rpm power.

A race pipe instead of the cats does help though as Mazda was stuck using cats to pass emissions.

Look at what Mazda did on the RX-8 to further address 13B low rpm torque when putting it in a heavier 4 door/seat sedan-
further refinements to the above mentioned systems and crazy rear end gear reduction to multiply torque at the wheels.

Use the highest ratio rear end you can afford (after 4:30-1 it gets expensive) and the smallest diameter wheels/tires you can fit over the brakes.

Decrease as much rotating inertia as possible in the drivetrain and wheels/tires.

It may seem counter intuitive to decrease flywheel inertia, but once the clutch is out and you are on the gas lighter components will help the car accelerate.

But if your idea of "low rpm power" is being able to sidestep the clutch without the engine dying at low rpm keep the heavy flywheel.

 

I've learned a lot, but now I'm going to research Peripheral ported rotaries. I was pretty sure that this hurt the life time of the engine. This is going to end up being my daily because my current dd probably won't last more than two or three months.

 

a P port might be a little hardcore for a DD, although its been done. the two things a PP does least well are be quiet and go slow. so if you live where all your driving is 10mph under the speed limit stuck behind a toyota, then the P port isn't a great choice.

if you live where its open, and you have room to run, then the P port would be awesome

this whole "lifetime of the engine" thing is bogus, how long are you really expecting to drive a 30 year old car? my P port got assembled in 2008, and it doesn't have many miles on it, but 90% of them have been on a racetrack, and it couldn't be happier

 

Well, I'm reading up on them right now. I'd love to do it but I need to make sure I can come up with the funds and resources to do it.