Howard Coleman

iTrader: (6)

given all FDs are turbocharged, it is so easy to make loads of hp.

it is less easy to make that output and enjoy engine longevity.

turbos come in all sizes, small medium and large and all we have to do is pick one and bolt it on.

medium is clearly understood as 400-450 hp.

here's a post from the board today that makes my point...

"So, I eventually want to upgrade my FD to single turbo...

Mods so far: downpipe, racingbeat duel tip exhaust, and upgraded airbox and ecu. All done by previous owner. I'm looking for around 500-700rwhp."


here's the point...

our motors displace 80 cubic inches

our motors displace 1.3 Liters

i have always used a number double the above as i was comparing the displacement of the combustive events in one rotation to a 4 cycle piston engine. the rotary does not have an every other non-combustive cooling event like any 4 cycle piston engine.

so, in addition to not having an every other cooling event, our motors actually are only l.3 liters actual displacement.

power is all about burning oxygen molecules.

period.

combine them w something that will burn and away you go.

turbos can cram huge amounts of oxygen into our motors.

further, while our motors are less efficient (VE) than piston motors per volume of displacement, our ports are much more efficient so we can make up for lower VE by better airflow in and out....

all of which makes our turbo efficiency really good. o k awesome.

all of which allows us to easily cram our motors w loads of oxygen.

all of which creates huge Combustion Chamber Pressure (CCP).

all of which creates huge Combustion Chamber Heat (CCH).

it is the AMOUNT of CCP and CCH which may not be fully appreciated.

let's put some numbers up. here's where the world's manufacturers in 2012 decided to draw the line. (consider being of more modern architecture all these cars have realtime ignition advance reduction under knock etc)...

Nissan twin turbo GTR 2.09 hp per cubic inch
Porsche 911 Turbo 2.15
Corvette ZR1 1.69

Mazda FD 3.18 that's stock at 255 FW hp

Mazda FD 400 rwhp (460 Flywheel hp) 5.75 hp per cubic inch
Mazda FD 500 rw (575 FW) 7.18 hp per cubic inch
Mazda FD 700 rw (805 FW) 10.06 hp per cubic inch

just to complete the picture and to show how well the rotary can flow air...

13B-REW 1000 rwhp (1150 FW) 14.37 hp per cubic inch

the obvious point here is that the turbo'd rotary, due to it's small displacement, has to be developing stratospheric amounts of CCP and CCH compared to a similar output turbo'd piston engine.

anyone who has properly modded a higher output turbo rotary has realised at some point that while the engine is extremely simple the systems needed to promote longevity are

numerous
sophisticated
expensive

if properly executed it is surprising how dependable a 4-500 hp rotary is given it's absolutely crazy state of tune.

it is tiny
it lacks an every other TDC cooling event

the rotary is not a fragile motor. as long as it is properly supported and tuned all is well but you have to know what you are doing.

recently someone lost his motor going for 500 hp. unfortunately he was running 550 and 1600s.

500 is generated by 960 CFM of air or 66 pounds of air.

at 11.3 AFR that is 5.87 pounds of fuel .92 gallons per minute or 3497 CC/Min.

injectors are rated at wide open. once they are at less than wide open they have lag, or slippage due to the mechanics... while it varies i recommend you use 15% flow loss due to lag so...

550 X 2 = 1100
1600 X 2 = 3200

4300 X .85 (lag deduct) = 3655 max net flow at 99 duty cycle

injectors tend to overheat above 85% so it is highly probable that the motor ran out of fuel.

running a 70+ pound turbo, which he was, w 550 primaries and 1600 secondaries was just asking for meltdown.

this of course is just one in a million learning experiences which many of us, including me, have acquired.

it is fortunate we have the board.

as mentioned, i have written on this before to the point where i have received some criticism (repetitive) but w the new year i thought i would trot it out again...

a 400 rwhp FD is miles past a 911 Turbo as far as state of tune. respect this or get schooled by reality.

howard

NVMYRX-7

iTrader: (24)

This is the kind of information needed when thinking out future rwhp goals. It would make our engines more reliable and prevent people from coming away from the rotary with a bad taste in their mouth; excellent write-up as usual!

Howard, you should be the build section mod

arghx

iTrader: (3)

I have been meaning to ask Barry Bordes what peak combustion chamber pressure he is seeing with his pressure transducers

RotaryEvolution

iTrader: (30)

but unfortunately the same is true with most other engine.

even honda guys are breaking close to or over the 1k HP range with teeny tiny motors.

http://www.youtube.com/watch?v=n4bYX_dzJI0

and bikes with over 600whp.. ***** of steel sitting on something that is likely to explode at that power level.

http://www.youtube.com/watch?v=7IUone3p5Tw


granted i love the feel and smoothness of these engines and the fact that they were able to hold this power decades ago even in stock trim blocks, but even the best will be soon forgotten with factory supercars pushing over that from the factory and v8 guys twin turboing their muscle cars. we're just a niche group still and always will be, with the random suprised faces who know nothing of this "rotary engine".

Barry Bordes

Another good article Howard.

Arghx, I am only running about 14 psi so my pressure is still low but I have seen a max of about 1100psi.

If you look at this chart notice a few things:
- how hot the exhaust gases are when the exhaust port opens (EO-1100 deg C).
- how fast the burn rate is (slope of purple curve).
- a double hump for climbing pressure (blue line).

Rambling thoughts-

- If we could use more advance and eliminate the double hump the peak would be higher and the exhaust gases would exit cooler. (watching out for detonation)

- If we could speed up the burn rate the EGTs would be lowered (probably the best approach).

- What we do inadvertently (or on purpose) is to keep the pressures down to save the motor by flowing more air and fuel (boost) through the motor to make big HP but not using it to its full potential.

- There is a mechanical limit that cannot be exceeded. If we knew what that pressure was we would be miles ahead. It would be great to monitor some drag rotaries for pressure.

Barry

arghx

iTrader: (3)

Interesting. That's about 75 bar. I have referenced in another thread a paper by Ford engineers which claimed a "structural limit" of 100bar on the 3.5 Ecoboost, or at least the prototypes they were using at the time.

And this makes me wonder what the curves looks like on a bone stock FD. It also makes me wonder what they would look like with a fuel that isn't knock limited for that level of engine load, like E85 or racing fuel. Going back to that paper on the Ford Ecoboost, one of the tests they did was comparing 0% ethanol 93AKI/98RON pump fuel and E85.



With the E85 the timing did not really need to be retarded, except at very high loads to keep the cylinder pressure from exceeding 100bar so the engine wouldn't fly apart. The middle chart shows the crank angle at which 50% of the combustion chamber mass is burnt. On pump fuel it comes later and later as the timing is retarded for higher loads, while for E85 it barely changes.

I have seen the double hump on piston engines, completely stock modern boosted ones. A rotary engine, or at least the ones we are dealing with, may also be prone to it due to the combustion chamber design and the use of two spark plugs.

shetlen

iTrader: (2)

As usual a very great write up from Howard! I've been reading your posts since 1993 and have learned a lot from all the knoweledge you have shared. Thank you!

BLACK MAMBA

iTrader: (58)

great write up,

indio84

iTrader: (7)

Nice read

Howard Coleman

iTrader: (6)

thanks for the kind comments...

and thanks for the two follow on posts with data.

Barry actually has been charting rotary internal combustive metrics. i note peak torque/pressure is at about 47 degrees at 14 psi boost. peak EGTs (i think the purple line is EO/EGT) peak after since they are somewhat cumulative.

it would be really interesting to see how the data moves around at 20 psi.

the data on alcohol (E85) V gasoline is amazing.... i actually am aware of alcohol's magical powers but just look at those charts...

note how alcohol retains a huge knock resistance even under significantly higher pressure as evidenced by the nearly horizontal timing advance w increased boost.

gasoline timing has to drop from 34 to 11 while E85 timing goes from 35 to 33!

timing curves are all about knock resistance and you can see how superior alcohol is in this regard...
.

while the burn rate is fairly similar...

timing alcohol at -33 gets half of the combustive pressure at 7 degrees for a 40 degree period.

gasoline timing at -10 gets it's half pressure at 27 for a 37 degree period.

all 3 charts are related...

look at the cooler alcohol EGTs... that's primarily because the combustive event happens 20 degrees earlier!

alcohol is magic as AI...

but so is water, just in a different way.

our teeny turbo'd motors need one or the other or both.

hc

arghx

iTrader: (3)

^ Yes, one thing leads to another. Improved knock resistance means that the timing can be advanced (or not retarded, depending how you think about it). Advancing the timing means combustion finishes earlier and thus you don't have nearly as hot of exhaust temps. Cooler exhaust temps mean you don't have to be as concerned about damaging things that come into contact with the exhaust, and you don't have to be concerned so much with having hot exhaust gases blow back into the combustion chamber under certain circumstances.

Most of the other ways of improving knock resistance have to do with factors beyond our control--redesign of the combustion chamber for example, or a drastic change in the fuel system (adopting gasoline direct injection). So improving fuel quality and/or improving cooling inside the combustion chamber help a lot.

Barry Bordes

Raymond in this study do they also show HP for the comparisons of E83 and 98 RON gas?

I think we are seeing more of an increase in burn rate for the gas and subsequently the retardation of spark event.

Why do you think E85 behaves so differently?

All knock related?

Barry

Liborek

X axis of chart shows BMEP, which directly corresponds with torque. Coupled with rpms (2500) and you have power. You just need to know displacement. (3.5 litres?) If my math is right, at 21 bar BMEP, they produced 209 HP and 439 lb.ft of torque. Pretty good Points directly above each other ie same BMEP are making same power. But then I must wonder if airflow was increased with gasoline tune. In second graph, there is indication that for creating mean best torque, 50% of mass fraction must be burned around 6°ATDC, and with spark retard its not happening with gasoline. With lower peak pressures, higher airflow must make up for lost efficiency otherwise I canīt see how it could create same work ie power.

Montego

iTrader: (1)

Me thinks you missed Howard's point.

oo7arkman

iTrader: (2)

Another great writeup howard. And i love the "respect this or get schooled by reality" comment.

RotaryEvolution

iTrader: (30)

the double hump in this application is likely the placement of the probe getting feeback from the face of the rotor as the "bathtub" crosses the breach.

i do that alot, it's a heavy bulky engine for "1.3 litres of displacement" and the argument that the rotary phases a firing cycle each pass will always cause arguments of it's displacement. even for a 2.6liter it still isn't king and has plenty of engineering flaws that still are being worked out many years later.

it generates too much heat, it eats too much gas, the block design has inherent flaws. some of that won't be overcome.

Montego

iTrader: (1)

Oh well...

adam c

iTrader: (2)

The motor is indeed small.

Many years ago, I ordered a new 13B engine from a Southern California engine builder. The engine arrived in a crate on the back of a delivery truck. The driver was a big strong guy. He picked up the crate, and put the engine in the back of my pickup truck. It was shocking to see him do that.

arghx

iTrader: (3)

Yeah that pretty much covers it. They don't explicitly mention horsepower for any of these charts. There is a section that mentions as a side note how the flex fuel 2009 F-150 using the 5.4 (3 valve per cylinder, naturally aspirated) goes from 365 lb/ft of peak torque to 390 lb/ft because it was specifically calibrated for more spark advance with E85.

I suppose that's possible. It's hard to say for sure.

It's important to keep in mind that the 13B came out in what, 1974? And hasn't really changed much since then. It's the same basic engine. Outdated engine is outdated.

Josh18_2k

iTrader: (3)

whats the record for hp/L anyway? afaik, its 1964 technology, aka 426 Hemi @ >1000hp/L

Supernaut

iTrader: (83)

Street motor?

NA, the s2000 is the highest.
FI I believe the 13B-REW is the highest.

RotaryEvolution

iTrader: (30)

i've said plenty that i love how competetive the design is and it still is as archaic now as it was then, many of the casting moulds mazda uses might well be 35 years old with minor changes to the pattern over the years.

the 16X aluminum block would be more comparable as a lighter version, but i just don't consider the rotary engine to be as compact and light once you bolt everything necessary to it, still lighter than a small block aluminum V8? yes. smaller than most import 4 bangers? nope, they're pretty damn small too. think you could pack a rotary as tightly into a hayabusa? they're still about the same displacement even if you disregard the stroke differences.

i just don't foresee aluminum block rotaries being common anytime in the near future so unfortunately i just choose to take the high road and just be an enthusiast without tricking myself into believing the engine is superior in some form aside from the fact that the basic technology is close to half a century old with very very minor changes over that span.

the engine does have one strong point and one i would rather emphasize, it has superior sealing characteristics as RPMs increase. even an old beat to snot rotary engine feels like new once you get it off a roll, even chipped seals still create boost smoothly once up to speed.. endurance engines rev, rev, rev some more then rev until you run the car out of fuel. they are great endurance engines if set up properly. the best endurance engines if setup properly.

j9fd3s

iTrader: (3)

a stock hemi is 425hp, so its 1hp per ci, or 60hp liter, its gross too, so when you put things like a water pump and oil pump on it, its more 50hp liter.

Mercedes had a 131hp/liter in their 1938 speed record car, they still have the record too, 268mph on a public road http://en.wikipedia.org/wiki/Mercede...25_Rekordwagen

the honda Ra-168E, the F1 turbo engine from 1989 was 920hp from 1.5 liters, 613hp/liter. the Ra-167E, from 1988 was 4 bar boost instead of 2.5 did 1200hp from 1.5 liters. 800hp/L, and this is what they admit to.

the early S2000 is 240hp/2 liters = 120hp/liter

shoot the Rx8 is either 180hp/liter or 91hp/liter depending on how you classify the engine size....

edit: oh stupid me, Hemi architecture; top fuel car, 500ci/nobody makes a dyno big enough, call it 5000hp. at least 588hp/liter?

Liborek

It is outdated, but there really isnīt anything what could be done to make significant improvement in efficiency or power production with regards to geometry and rotor pocket design. 16X geometry indicates faster burn rate and higher heat generation rate than older geometry, but these tests were conducted at low loads and low rpms with combustion stability in mind - emission purpose. Other already examined technologies can be retrofitted to existing designs. So only complain we can have is in regards to structural integrity of engine but we already know what kind of power and torque these engines can hold - assuming there isnīt abnormal combustion. Better control is everything what can be done. So its just up to people why they choose 10 years old ECU and not even utilize available safeguards

Gorilla RE

iTrader: (1)

Howard, why after all these years, you're now saying it's a 1.3L? I thoght your mathematics said "2.6L".....

-J