AgentNH

So just out of curiosity, what is the airflow of a 20b.

I know the 13b is only 1.3l, but has airflow that is close to a 2.4l - 2.6l piston engine.

I'm assuming it works the same way for the 20b, but haven't been able to find much info about it.

Thank you

hsmidy

Yes they do get compared to higher displacement engines like the 13b does but to give you an idea a 20b at 3000rpm will pump 208.3 CFM. that's not taking into account any volumetric efficiencies.

t-von

iTrader: (8)

20b moves 2.0 liters of air every revolution of the eshaft.

AgentNH

What would and air flow of 486.1cfm at 7k rpm be compared to for liters? Looking for superchargers so need the right displacement

hsmidy

google is your friend...

Havoc

Not that simple mate.

What type of SC
what type if inter cooling
E85?

So many other factors will affect the characteristics of the SC efficiency you need to take it into account. Id look / chat at others that have done it previously

Popular option in NZ by the way.

AgentNH

Thank you for reminding me, that completely went over my head. Sorry

Havoc

Lots of good reading on Rx7club.

Personally a root blower is the wrong type - but are relatily cheap.
Getting Ruthless, Blown Triple-Rotor Style - Speedhunters

this is a 6/71 on a 20B.

Not very big HP. if you want HP go turbo like 99% of all other builds do (turbo is significantly better on rotors than SC's) - you can close your hood as well

BLUE TII

iTrader: (9)

Takes a lot of air going through a rotary to make power especially if its ported.

Have you thought instead about just putting another 20B on top of the 20B instead of the blower that will be about the same size?

Just look at the hog in the link.
470rwhp out of a P-port 20b with a 6/71 that should get 470rwhp naturally aspirated. Yes, I am sure it makes more power than the NA 20B "under the curve".

C'mon, stack a 13B or 20B on top of that 20B instead.

BLUE TII

iTrader: (9)

Also, have you driven a S/C rotary before?

You would think they have great down low power, but they have even less power off idle than an NA rotary because of all the supercharger drag and still not much rotating mass.

My friend has a S/C 12A in a 1,500lb tube frame race car and its ok once you get going (except for the weird no top end in a rotary feeling), but man... positive displacement S/C doesn't fix any rotary driveability problems for sure. From a stop its like trying to drive a blown up turbo rotary with the AC on.

hsmidy

You may want to look into the actual dimensions of the charger required, I wouldn't advise using a roots type, which will leave you looking at something along the lines of a screw type, to get one that is the correct size it will most likely be longer than the engine itself.

You will also need to consider the rpm of the charger vs the engine, don't want to over speed the charger. A screw type should be good for about 18,000rpm (charger speed) but check with the manufacture.

Thirdly make sure you're aware of the chargers pressure ratio limit.