I'm reading a really interesting book about the development and design of the Ferrari 2000 F1 Car. It has some very interesting, info, pictures and details on F1 cars.

Most people would agree with the statement that piston engines improved their power efficiency massively over the 20th century, right? Here's an interesting comparison:

1913 Peugot 3L F1 engine: 31.5hp @2900rpm = 10.7hp/L/1000rpm
2000 Ferrari F1 3L V10: 800hp @ 17,500rpm = 15.2hp/L/1000rpm
2007 Honda Accord 3L V6: 244hp @ 6250rpm = 13.0hp/L/1000rpm
Honda S2000 2L I4: 240hp @ 8300rpm = 14.5hp/L/1000rpm.

 

This year's F1 engines were putting down 730-750hp with 2.4l atmospheric engines.

 

I havent really watched F1 since Automatic Transmissions, Traction/Stabability Control and ABS came out.

 

Sean, I thought you'd be up north by now.

 

A modern engine has better volumetric, and brake specific fuel efficiencies, is cleaner (emissions) and more fuel efficient than engines from way back when. They're also a hell of a lot more reliable. That's an improvement in my books.

I'm not really sure what the point in a power/(L*rpm) comparison is, so what if the 1913 motor made numbers 2/3 of those of today, it's a primitive, slow turning, low powered engine. I'd like to introduce the concept that power is power, it doesn't matter at what rpm it's made, the gearing can be adjusted to suit the engines power band.

 

Who cares about pistons... this is an RX-7 forum!

 

Funny you should say that seeing as your user name is Mazda code for the turbo 1.6L 4 cylinder piston engine from a 323 GTX.

 

While this is interesting... I'd love to see comparisons of how far the rotary has come. Probably not as significant of a leap as the piston engine, but considering only one company is doing development, it's amazing that they've made so many advances and managed to keep up. The Renesis is nicely engineered and the fact that they can pull 200+ hp out of an N/A engine while still being emissions compliant is a big achievement for rotaries in my books. I mean the '85 GSL-SE was an FI 13b and it only put out what.. like 130hp?

Not that I really need an emissions-compliant enigne

Jon

 

I was out last week for awhile. I was slated to goto Grande Cache (or some hell hole) this week, but Im going to a job fair in red deer instead.

Once people start heating their homes and bombing Iraq again, then the work rolls in full force.

 

Just an FYI that the S5 13B did produce 160HP. The Renesis is better, but I can't help think how good the rotary would be today if Mazda wasn't the only contributor.

 

Heep in mind the GSL SE put out 135 hp at about 6500 rpm while the Renesis hits it's peak at about 9000. I would like to see a dyno overlap of the 2 to really see the difference.

 

I thought it was of interest because we often compare piston engines to rotaries and whine about "imagine if lots of R&D was spent on rotaries." The 1913 example is amusing because they were so limited by technology. Horses were still reasonably common place! Essentially what it shows is that if they had reasonable materials, tooling, etc. they could have reved the engine and made decent power. That doesn't change the core ability of the design. The bottom line is that there certainly hasn't been anything in the last while that has drastically improved the power efficiency of the piston engine.

There's no question that fuel economy has drastically improved, but how much of that is due to the real core of the engine and how much of it is due to improved fuel delivery?

S4 n/a 146hp @ 6500rpm = 17.2hp/L/1000rpm
S5 n/a 160hp @ 7000rpm = 17.6hp/L/1000rpm
Renesis 232hp (I guess that's SAE corrected) @ 8500rpm = 21.0hp/L/1000rpm

Realistically it should be rated at 1/2 that when comparing to piston engines or 10.5hp/L/1000rpm for the Renesis, which is ~25% lower that a piston engine.

 

Comparing it to blocks of 1,000 RPM is unrealistic as different engines have different HP/Torque curves. To be better comparision, the area under the curves should be compared. This calculation rewards high revvers like the S2000 and RX-8 rather than comparing thier true powerband.

 

yes power bands is a huge deal, point proven with the TDI, diesels torque higher at lower RPM, there for use WAY less gas.. er ......fuel.

what i really admire about the rotaries is the potential, given that our motors are 2 stroke, 1 combustions per rotation. would kinda make us have to compare out motors with 2.6L and how many 2.6L have made upto 700rwhp? or to people that don't know better, tell them ur 1.3L produces upto 700rwhp.

 

Deisels generate so much tourque because of the mass of the rotating assembly. They use alot more fuel to get going compared to a piston motor, simply because of the forces required to move all that mass. However, at speed, they require less fuel because it takes less force to slow down the engine due to the huge amount of inertia.

*Takes sip of beer*

Correct me if Im wrong anyways.


The automotive industry is angling towards fuel economy. But realistically, Economy is more of less the same in most cars. Their tests are flawed because its not real world driving conditions. They stick it on a dyno and run it at 2 or 3 different steady speeds and measure. Slap a sticker on the side and away she goes.

Unless your Aaron Cake and use Half a tank from Toronto to Indianapolis.

But honestly, who here accually is concerned about fuel economy. I know Im not. I fill my car up when nessesary, using the same gas I always do, at the same place I always do.

 

Diesels are more efficient for 2 reasons:

1. they do not have throttle plates, so the pumping losses are less
2. compression ratios are enormous compared to the average spark ignition engine

Heavier rotating assemblies are less efficient and slower always and forever, including in drag racing.

Diesels are limited to low RPM's because the combustion is slower.

And once again: Revs and power are most important, provided the gearing is adjusted to suit. An extreme, unpractical example:

Assume an engine makes 150lb-ft at 8000 RPM. For an axle RPM of 1000, you would send that torque through an 8:1 gear, giving you an axle torque of 1200 lb-ft (ignoring drivetrain losses)

For a motor spinning at 2000 RPM to give the same axle torque at the same axle speed, it would have to put out 600 lb-ft, which would be sent through a 2:1 gear.

Now, here's where it gets interesting: Both motors are making exactly the same power at those conditions, 228.5 hp. So theoretically, both vehicles being the same weight would imply that they would accelerate at the same rate. The rub is that transmitted torque determines things like shaft diameters and bearing sizes, which in turn dictate the size and weight of the drivetrain components, which determine mount size, configuration, and support requirements, which affect body structure, and body mass, which affect suspension component size and weight, brakes, wheels, tires, etc....

So, practically, there is no way that a vehicle with 600 lb-ft could come close to the weight of a vehicle with 150 lb-ft, thus the 150lb-ft vehicle would actually be faster, due to its lightness. It's why a super7 will eat a corvette's lunch below 100 mph.

Yes: high RPM's will be harder on components, and require more finesse, but power is power regardless of location, as long as gearing is considered.

 

It doesn't really reward high revers that much as long as your comparing similar purpose engines. Look at the 1913 engine numbers, that's the best they could do and it's not that different from today. What will dictate the power curve is primarly basic parameters like valves per cylinder, compression ratio, intake/exhaust tuning and cam lobe profiles. The point is that they are all pretty close. In the past 100 years they've managed to gain somewhere around 50% efficiency. The calculation will reward engines that were designed mostly for HP rather than other considerations (such as those pure spike 400hp n/a 13B drag engines), but that's the focus of my comparison anyway.

Early 80s peripheral port 13B for endurance racing: 300hp @ 9000rpm = 12.8hp/L/1000rpm (making comparable to piston engines)
13G in the 757 (1987): 450hp @ 9000rpm = 12.8hp/L/1000rpm
R26B in the RX-792P: 650hp @ 8500rpm = 14.7hp/L/1000rpm
R26B in 787B: 700hp @ 9000rpm = 15.6hp/L/1000rpm
13J-M 767 (1989): 630hp @ 9000rpm = 17.9hp/L/1000rpm

 

you know wengines from way back then had gobs more torque too eh. For example a 180hp Diamler-Benze used in the Fokker D VII (1917-1918) is equivalent to about 350 modern aircraft hp.

Now a 350hp Lycoming is in peices at 3500rpm. Peak hp is probably at something like 2700rpm. On The Diamler Benze peak hp was at like 1800rpm.

However, 35hp and 3L is still very inefficent. That is at most 150ft/lbs of torque.

I hope what I said makes sence.

 

Heres a nice video of a piston engine

http://www.youtube.com/watch?v=Eo-9Io41bt8

for those who arent rotary biased .

 

I ******' love F1

Seriously, I don't care whether the inside of the motor is spinning or going up and down.........as long as its doing it at 17,000rpm, its fine by me

 

There are some beautful engines being made these days. The new Porsche Turbo engine, and the new BMW M5 engines are two that come to mind. Some awesome power levels coming out of these, and relatively speaking for the power they produce they don't have shortcomings in emissions and reliability, etc.

And as much as people can argue that pistons have had so much more R&D than wankel engines, i think the wankel is still fundamentally bested by the piston engine design in efficiency from a purely laws-of-physics perspective. Anyone care to elaborate further on this?

 

except for the super short "Stroke" of rotaries, and the port overlap, i completely agree with u coldfire. however i still believe every motor has it's place. pistons are for the soccer moms.

 

Great thing about Porsche is that nothing has really changed in 40 years. Its still a flat six. The motor grows and shrinks with every new performance discovery. After all, the Porsche 911 Turbo was the first mass produced turbo powered car.

 

Yes, and the freakishly long (almost eerily long) turbo lag was great supporting evidence - hehe

Well, I personally feel that with more R&D the rotary could come up to a (more) acceptable level of emmissions relative to size/power output. I mean, essentially, the engine has only undergone 4 configurations in its 40ish year stint on the road (with respect to mazda). Yes there may have been other layouts etc. tried in the labs or by wankel in his time with NSU, but really only 4 major designs were ever "road worthy" and were put into cars, a 10A p-port, a 12A side port intake, p-port exhaust, the 13B and 13BT (and TT) and the renesis. And when comparing the leaps made between 13B and renesis with respect to power level at the same displacement vs. emissions, it seems that we are FINALLY starting to really get somewhere.

But I still really do think they'll never be on the same level emissions wise just given the 2 stroke nature of its operation...but I have no doubt that with more and more tweaking to port design, ignition and port timing they can come to a level even closer than the Renesis.

One last thing, is the Renesis, when you really think about it - is probably more efficent emmissions wise than most piston engines were 15-20 years ago.....just seems to always be the case, the piston motor stays ahead by about the same amount of time that it was ahead from the get go.....

 

the HP/l/1000RPM is a kinda neat way to measure things, as rewards torquey motors that don't need revs... but it also rewards large, revvy motors that make power...

it actually just rewards forced induction...

The engines can only get sooo efficient N/A before they simply can't suck in enough air to produce any more horsepower per given RPM.