when Mazda added turbos to the 13BREW it was a game changer.

thanks primarily to the 50 mm peripheral exhaust port the engine can breath in a different zipcode than a piston engine of similar displacement.

taken to extreme, running methanol the 1.3 L 80 cubic inch motor can produce over 1100 rwhp! Ok, admittedly that's crazytown (but true) so let's take another approach to better understanding our motors.

i have posted some of this here and there so maybe you are rolling your eyes thinking here goes Howard again... feel free to turn the page.

here's a list of the heavy turbo and supercharged hitters for 2017 or thereabouts:

2017 Corvette supercharged 552 rwhp 378 cubic inches 1.46 hp/cu inch
2017 Camaro ZL1 supercharged 544 rwhp 378 cu in 1.44 hp/cu inch
2017 Nissan GTR Nismo twin turbo 510 rwhp 232 cubic inches 2.21 hp/ cu in
2017 BMW twin turbo I4 211 rwhp 122 cubic inches 1.73 hp/cu inch
2016 Ferrari 488GTB twin turbo 562 rwhp 238 cubic inches 2.36 hp/ cu inch
2017 Mclaren 570 twin turbo 477 rwhp 232 cubic inches 2.05 hp/ cu inch
2017 Porsche Turbo twin turbo 493 rwhp 232 cubic inches 2.12 hp/ cu inch

1993 Mazda RX7 217 rwhp 80 cubic inches 2.71 hp cu inch
1993 Mazda RX7 400 rwhp 80 cubic inches 5 hp/cubic inch
1993 Mazda RX7 500 rwhp 80 cubic inches 6.25 hp/ cubic inch
1993 Mazda RX7 600 rwhp 80 cubic inches 7.5 hp/ cubic inch

consider that the world of 100K+ supercars is ULTRA competitive, yet even in the 2017 world of titanium connecting rods and supercomputer ECUs the lines between hp greed and warranty expense cross.

it looks like they cross around 2.25 hp/ cu inch.

now consider our 13BREW powerplants... updated to FD spec around 1992... that would be 25 years prior. what type of smartphone were you using in 1993?

so if the line cross around 2.25 hp/ cu inch how do we now consider our "moderately" modded 5 hp/ cubic inch 400 hp motors?

hint: better consider them very very seriously.

what's that you say, you don't need AI because you are only running 400

no matter what power level FD you have, even stock, you have a beast that requires lots of respect.

Howard

 

Poignant illustration, but I just wanted to get in before the argument about whether the cubic displacement of a 13B engine is actually 80ci or 160ci or 240ci. There's some very good arguments to say that's the latter.

 

compared to a piston engine's breathing ability per crankshaft rotation would put our Rotaries in the 160ci spec. Even so, we're still outputting very high power densities.

217 rwhp 160 cubic inches 1.35 hp cu inch (comparable to supercharged LS3)
400 rwhp 160 cubic inches 2.5 hp/cubic inch
500 rwhp 160 cubic inches 3.13 hp/ cubic inch
600 rwhp 160 cubic inches 3.75 hp/ cubic inch

and we're only looking at displacement. Physical size and weight power densities are extraordinary as well.

 

those engines you mentioned all meet LEV III emission, and Mazda pulled the FD from the US because it couldn't meet the introduction of LEV I in 1996.

 

I think Howard has a good comparison on power density.

Yes, the rotary has 3 rotor faces working on the 4 strokes all at once, BUT it only has one combustion chamber/spark plugs set on the rotor housing side.

This means that the related material components are really getting punished.

Spark plugs and rotor housing at the spark plugs area.

I believe the spark plugs are what got Howard thinking about the power density of the rotary.



arghx
those engines you mentioned all meet LEV III emission, and Mazda pulled the FD from the US because it couldn't meet the introduction of LEV I in 1996.

This is true.
It is also true that the 13B-REW was basically the same 1960s engine as the 10A. Very little evolved in terms of sealing besides some tweaks to apex seals.

The new rotary (after the recent oil seal research and high speed combustion filming) is really going to be the first evolutionary step in the Mazda rotaries life.

Its like every rotary from 1967 to 2012 was a flat head V8 of varying displacement and now they are finally going to release an OHV V8.

If we are lucky it will be an LS and not an old small block Chevy.

 

Oh no. With no technical background I usually have to read it again and again, but I always enjoy it.
I'll probably be stealing some of these figures to annoy my Z32, GTR, Vette and Camaro friends.

 

Well said.

Everything about the FD is extraordinary, not just the elite engine, even in 2017 it is hard to find a better base production car for most any circuit course no matter your budget. Even with possibly the worst customer support ever provided in the history of the world, MAZDA can still boasts that it was a masterpiece.

 

Really nice point on the comparison to the available generation of rotaries to the flathead V8s. If we were going to compare the 13B to the OHCs though, I would have likened the Renesis to the first 3-valve engine, lol.

To add to this, if Mazda does release the SkyActiv-R 16X and reaches their 400BHP goal, they'll have attained a pretty astounding 4.1BHP/CI. For a vehicle straight from the factory with a warranty and such, that's a lot of confidence that the engine will handle that much stress reliably.

Mazda must be cooking up something interesting for how they plan on tackling the spark plug bosses to handle that.

On that subject, does anyone have a thermal camera video of a 13B at the spark plug bosses? I was thinking about asking in a separate thread, but this thread caught my attention.

 

I think its important to compare oranges to oranges

• The 13b rotary have 2 rotors, with 3 sides each. The eshaft move at 1/3th of the speed of the rotor. The result is 1 ignition per rotor per revolution. In total 1308cm2 of combustion per crank rotation.
• The Nismo GTR have 3.8 liter V6. Pistons ignite every 2nd rotation of the crank. That means that the Nismo GTR only have 1900cm2 of combustion per crank rotation.

Since power as we measure it, is a product of Nm and RPM, actual combustion chamber volume per rotation should matter.
But even if we compare the sizes like that, the rotary have a 30% smaller combustion volume than the Nismo

Am i just rambling or is it any sense in this?

 

This is basically the point that neit_jnf made. It's why people often say 13Bs are like 2.6L 4 cylinders. So it's true that if we were to really compare apples to apples (or oranges to oranges), this would be a more accurate description from a VE standpoint. Nevertheless, 1.3L is what the SAE eggheads determined, and I'm sure there's a reason for it. Anybody remember why?

 

Its the displacement volume per crank rotation. Its the same for piston engines, but they only use half of it for combustion (and hence, they suck )

 

There's a great 11 page discussion on this on AusRotary. This post really summed it up best: http://www.ausrotary.com/viewtopic.php?f=16&t=33795&p=356811#p356811

Mazda's methodology is to multiply the displacment of a single combustion event in one rotor housing by the number of housings. This really doesn't provide any useful explanation for what's really happening and ignores that for each housing, 3 combustion events (one for each rotor face) must occur for the engine to complete a cycle. Measure displacement by reference to a single crank revolution and the answer is diffetent again.

In summary, for a 13B
(1) Mazda's capacity = 1308cc
(2) Capacity rated as displacement with respect to rpm = 2616cc
(3) Capacity rated across complete engine cycle = 3924cc

number 2 is arguably the most useful for comparing to engines that employ different cycles.

 

"here's a list of the heavy turbo and supercharged hitters for 2017 or thereabouts:

2017 Corvette supercharged 552 rwhp 378 cubic inches 1.46 hp/cu inch
2017 Camaro ZL1 supercharged 544 rwhp 378 cu in 1.44 hp/cu inch
2017 Nissan GTR Nismo twin turbo 510 rwhp 232 cubic inches 2.21 hp/ cu in
2017 BMW twin turbo I4 211 rwhp 122 cubic inches 1.73 hp/cu inch
2016 Ferrari 488GTB twin turbo 562 rwhp 238 cubic inches 2.36 hp/ cu inch
2017 Mclaren 570 twin turbo 477 rwhp 232 cubic inches 2.05 hp/ cu inch
2017 Porsche Turbo twin turbo 493 rwhp 232 cubic inches 2.12 hp/ cu inch

1993 Mazda RX7 217 rwhp 80 cubic inches 2.71 hp cu inch
1993 Mazda RX7 400 rwhp 80 cubic inches 5 hp/cubic inch
1993 Mazda RX7 500 rwhp 80 cubic inches 6.25 hp/ cubic inch
1993 Mazda RX7 600 rwhp 80 cubic inches 7.5 hp/ cubic inch"

while all of the posts above are fine and break no new ground for most of us whether you choose to think of our motors as 80 or 160 cubic inches, 1.3 or 2.6 Liters the fact remains:

our motors are way more stressed than we think. if we chose to use 160 cubic inches, 2.6 liters we end up w the following:

"here's a list of the heavy turbo and supercharged hitters for 2017 or thereabouts:

2017 Corvette supercharged 552 rwhp 378 cubic inches 1.46 hp/cu inch
2017 Camaro ZL1 supercharged 544 rwhp 378 cu in 1.44 hp/cu inch
2017 Nissan GTR Nismo twin turbo 510 rwhp 232 cubic inches 2.21 hp/ cu in
2017 BMW twin turbo I4 211 rwhp 122 cubic inches 1.73 hp/cu inch
2016 Ferrari 488GTB twin turbo 562 rwhp 238 cubic inches 2.36 hp/ cu inch
2017 Mclaren 570 twin turbo 477 rwhp 232 cubic inches 2.05 hp/ cu inch
2017 Porsche Turbo twin turbo 493 rwhp 232 cubic inches 2.12 hp/ cu inch

rated as a 160 cube motor:
1993 Mazda RX7 217 rwhp 80 cubic inches 1.35 hp cu inch
1993 Mazda RX7 400 rwhp 80 cubic inches 2.5 hp/cubic inch
1993 Mazda RX7 500 rwhp 80 cubic inches 3.12 hp/ cubic inch
1993 Mazda RX7 600 rwhp 80 cubic inches 3.75 hp/ cubic inch"

a "moderately" modded 400 rwhp FD is in a much higher state of tune than any of the above supercars.

add to this there is no every other TDC cooling cycle!

take your pick as to how you wish to measure displacement. let's discuss aspects of making life easier for our motors.

Howard

 

Bingo. It's a 1.3 liter that aspirates its displacement every crank rev, like a 2-stroke piston engine. The 6.8 liter LS3 in my FD only aspirates 3.4 liters per crank rev, which makes me sad

The rotary loses a lot to heat, though, so the power-equivalency formula is more like 1.5X rather than 2X, hence the 9000rpm 1.3 liter RX-8 only made the same power as the 9000rpm 2.0 liter S2000 (a bit less, actually).

 

The 6.8 liter LS3 in my FD only aspirates 3.4 liters per crank rev, which makes me sad

Don't be sad.
Put a 2 stroke V8 in your FD!

 

Ha ha! Pretty cool...

 

Is it 3.6 liters or 7.2 liters though?

 

the flathead to rotary thing is a pretty valid way to look at it.

the rotary has a weird combustion chamber shape, and the closest piston engine equivalent actually IS a flat head.

also adding the old timeiness, the rotary uses iron pistons, you have to go very far back to find a piston engine with iron pistons (but when you do you find out that they like to randomly fail because iron does not conduct heat)

and then the rotary uses three chambers and one port, or set of ports. there are many piston engines that have two, like an A series in a Mini, or B series in an MGA/MGB.

so a 13B is a bit like a Siamese port flatheaded 4 cylinder with 654cc chambers and iron pistons. the Rx8 engine is much revised, but the fundamentals are still the same.

i think you can make a fair comparison to an LS engine too, the 5.3 engines have 662cc chambers....

 

Why do people still elude to the misconception of the 1.3L 13B-REW.
If you compare it to a 4 cycle engine of 2 revolutions of the crank, there are 4 firing pulses.
Thus the engine is a 2.6L when comparing to normal 4 cycle piston engines.

Using 1.3L is just blowing farts up your nose!

 

cewrx7r1
Why do people still elude to the misconception of the 1.3L 13B-REW.

Because the 13B is a 1.3 liter Mazda rotary engine.

Mazda has made this engine and rates its displacement as 1.3 liters.

Others compare the 13B rotary engine to piston engines with an equivalency rating as you are doing.

If you compare it to a 4 cycle engine of 2 revolutions of the crank, there are 4 firing pulses.
Thus the engine is a 2.6L when comparing to normal 4 cycle piston engines.


No one ever rated engine displacement by how many "firing pulses" there are.

If they did, they would take the rated displacement of 4 stroke piston engines and divide it by four!

Compare a 1.3 liter 4 stroke to a 1.3 liter 2 stroke.
Interesting, no one cares about "firing pulses" when it comes to displacement- the holes in the engine block have the same volume.

Racing bodies come up with their own 4 stroke displacement versus 2 stroke displacement versus rotary displacement versus piston number or piston layout equivalencies based on the politics of racing.

If you want to argue a 650cc 2 stroke has as many firing pulses per dislacement per crank revolution as a 1.3 liter 4 stroke or that a 1.3 liter rotary has as many firing pulses per displacement per crank revolution as a 2.6 liter 4 stroke piston engine or like a 1.3 liter 2 stroke piston engine- you are correct.

But firing pulses do not factor into displacement.

Piston engine displacement

Engine displacement is the swept volume of all the pistons inside the cylinders of a reciprocating engine in a single movement from top dead centre (TDC) to bottom dead centre (BDC).

Mazda rotary engine displacement

Mazda rotary engine displacement is the swept volume of all the stationary combustion chambers in the single movement of the rotor face from top dead center (TDC) to bottom dead center (BDC).

 

^

 

"Iron pistons"

So basically the metallurgy of our engines is still basically pre-war. Well damn. What would it take to have an aluminum rotor? Or maybe steel is the best we can hope for.

As for equivalences to piston crown development, the closest thing I've seen with rotaries are expanding the bathtub for lower C/R or splitting it in half so there was a bathtub for each plug. No idea how that last idea worked out though.

 

true. my boss told me about the Honda RC-166. in the mid 60's Honda wanted to go GP bike racing, and everyone else was running a 2 stroke, 250cc. Mr Honda wanted a 4 stroke.

the engineers made a 6 cylinder 250cc engine, that simply spins twice as fast as the competition. 62hp@18,000rpm. 248hp/liter and this is in 1965.

apparently hearing this thing in person is bucket list material.