i just want to say if anyone know the actual top speed of the 20b......i know maybee u guys answerd this question but can u guys do the favor and answer it again i'm new to the site 2 days

 

1,054 MPH

 

Seriously, what kind of car is it in? What is it bolted to? How much is it modded? 200+ MPH is not out of the question for a seriously modded car with a 20B.

If you are talking about a stock 20B Cosmo, I think that it tops out at about 160 MPH.

 

In stock form, the redline is 7,000 rpm.

See "JC Cosmo"
http://www.dmrh.com.au/

 

Asking what the top speed of an engine is usually gets laughter. They normally need to be installed in a car to go anywhere.

Assuming you are reffering to it installed in its original home, the JC Cosmo. Mazda quote the top speed of the (20B optioned) JC Cosmo at 255kph.

All Japanese domestic cars have a 180kph speed cut, so that requires disconnection if you want your Cosmo out on the limit.

Fastest I have ever gone in a JC Cosmo is around 240kph with the speed cut disconnected. Was still rising on the tacho (6000rpm in 4th) but was starting to run out of road & they don't have the same braking power as the FD RX-7.

 

Top speed is only limited by:

engine power
gearing
aerodynamics

Just by gearing, stock top speeds for vehicles are:
Zenki FC3S turbo - 160mph, 7kRPM redline
Kouki FC3S/FD3S turbo - 190mph, 7kRPM redline


-Ted

 

A US spec FD with stock 4.10 gearing is limited to 182mph in 5th @7500rpm. Thats with the stock tire circumference.


What is Kouki?

 

Hmm, I always just assumed that the top speed of the engine was its redline. The original post asked for the top speed of the engine, not the vehicle.

Top speed of the vehicle also depends on...

engine rpm
wind vector
ambient air density (temperature, pressure, & humidity)
vehicle weight (mass and gravitational pull)
road grade and coefficient of friction
tire ground pressure, surface area, and coefficient of friction
tire diameter of the drive wheel (this is a sub-set of gearing, which was already mentioned)

That's all I can think of right now.

Zenki = early
Kouki = later

 

is there any reason that the 20b redline is 7000 and the 13btt redline is 8000? what did they change? is there much power left after 7000 in the 20b?

 

As I understand it, it's a matter of design. The 20B has smaller exhaust ports, which translates to more low-end torque. Therefore, above 7000, you're not accomplishing much. The 13B-rew rotor housings have larger ports, which gets you more power, but it comes higher in the rpm range.

One of the easy mods for a 20B is to go to 13B-rew housings.

When I talked with the chief mechanic for the Kudzu racing team, he said that they ran peripheral ported 20Bs at 9000 rpm all day long. (550 hp)

 

Must be an Oz/US terminology thing.

I would have taken it the other way had he asked "What is the max RPM of a 20B"

To get Lemonade, I have to ask for Sprite. If I ask for Lemonade, I get lemon flavoured cordial...........

 

Don't you use the EMS terminology of "speed density", where "speed" = engine rpm?

Hehehe, one of my colleagues asked for a "soda" in Tel Aviv, and got a cup full of soda water instead of the expected flavored soft drink.

 

so with the 13b housings do you end up changing anything (does it mess with the stock turbos?) thanks

 

You would have to re-tune your EMS, I think. You might want to check with Pettit. I believe their 20B used the 13B housings.

Either way, the stock turbos are going to "run out of breath". In the Cosmo, I believe they only ran to 5.5 psi. I run mine to a peak of 1 bar (14.7 psi), but that naturally declines as the engine speed increases.

 

20B rotor housings are the same as the FD 13B rotor housings with the exception of an exhaust sleeve which Mazda quoted was to quieten the exhaust, this suited the luxury tourer theme of the Cosmo.

In factory form, the boost ran to 9psi, sometimes 10psi on a cold night. Boost cut is at 14psi.

The lowest boost setting on a turbo Mazda rotary was the 12A turbo from the HB Cosmo. This was at 6psi. The 13B turbo from the FC RX-7 ran at 6.2psi

 

God damn.. you guys need to make a rotory trivia game and sell it..

Zenki FC's = 86'-88' FC3S in japan
Kouki FC's = 89'-91' FC3S in japan

 

Scoot done over 200mph + in a red FD3S in new Zealand on the roads and with raidal tyres with a 13B


ANY V8 WANA RACE EM EHEHEHEHEHEH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Easy mod?

I'm using the stock 20b rotor housings but with 13b-rew exhaust sleaves.

 

this way is easier/harder????
i thought change the housing were easier.

 

to use the 13B housings you just have to drill a couple of the torsen bolt holes a little bigger and your done..

 

My understanding from Cam is that using the 13b housings is required if you are looking for more hp. The way I looked at it was I had an extra 13b hanging around when I did the swap!!!

I will be trying for over 200 in Vegas Sept 21st when we have our next race.

 

the 20B housing is Identical except for the slightly larger torsen bolt holes in I beleve 2 positons, and the port sleve itself.. O' and the fact that it says 20B up on top.. Here in Japan they inspect the engine # during our anual 2 year saftey inspection, so I will definitly be using the 13B housings.. I will also be paying sombody off as well...

 

if i have the money right now will you sell the car?