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iTrader: (3)

the pinto motor in question makes 90hp and 134lbsft, in 88, when the na 13b only made a mere 140hp and 130lbsft. i looked, the 2.3 made 105hp in 92 when the 13b made 160. the turbo 2.3 made 190hp and 200lbsft, while the rotary made 182hp and 150lbs ft, in 1988.
the ford engine is a cast iron single cam engine that debuted in the pinto in 1970, it hasnt had a major redesign since. the rotary has been updated several times, 74 and 86, being the major ones.

mike

Defprun

He is kinda fucked, but whatcha want. The 2.3 litre TURBO engine in the SVO, Turbocoupe and MERKUR XR4ti all have the same engine, at aboot 2500rpm the engine produces 175hp and 150 (200 with exhaust?) pounds feet of torque @15pis of boost . The mustang SVO and Turbocoupes have different computer, have an intercooler and different VAM setup so they produce more horsepower, and since the mods make the turbo spool quicker its safe to say that these engine have quite more torque than the XR4ti and 200p/f torque is very realistic. I heard somewhere that the stock merkur was 175hp at 200 pounds feet of torque (with no exhaust) but im not sure about that source.

Anyone have dyno results from a stock Mustang SVO or thunderbird Turbocoupe?

Defprun

and i have no idea what this has to do with rotaries, but i did see a 2.3 swap into a first gen and my eyes freed themselves from their sockets and ran around screaming on the ground as they burned into ash. It was horrible.

wes2k3

I got the 2.6 from that fact that the rotary combusts 6 times for every rotation of the crank and a v-6 would combust 3 times, meaning that the displacement on a v-6 is measured for 2 rotations of the crank, and if that were done the same on a wankel you would get 2.6 liters. Due to this same principle 4 cycle motorcycle motors running in the same class as 2 strokes can be up to twice the displacement.

Don't freak out on me if I say something you don't agree with/like, I just want to learn more about this. The wankel is so interesting

neo_omega

this is the first time I hear someone say rotary is inefficient.

Defprun

Yes, i still dont get it? how can something that has three different parts of the combustion cycle going all at the same time be as inefficient as something that only does one part of the combustion cycle only once? I DONT GET IT!

wes2k3

if it's more efficient why isn't it producing more power for a given amount of fuel?

Icemark

Actually the Aspire and Festiva were both made by Kia which is 12% owned by Mazda.

You also forgot the Mercury Tracer which was a 86+ 323

And the Convertible you mention was the Capri made in Austrailia, by Ford workers that drank way too much Fosters beer at lunch. That Capri should not be confused with the late 60's to mid 70's European built Capri (which was a great car with the 2.8 v6 making 150 HP) or the 80's version of the Capri which was nothing more than a Fox body Mustang with slightly different sheet metal).

Icemark

Perhaps you should compare more closely to the other performace cars of the time.

For example the early to late 80's GM F body Z28 used a V8 that only got 15 mpg, and had only 160 hp until they brought out a HO version that got up to 190 HP.

Compare that to your 1.3L 146HP mid 80's non turbo 13B.

or even the early 90's V8 'vette or Mustang with their 15 MPG 220-240 HP V8 to a 200 HP 1.3L single turbo engine.

So to produce simular HP with slightly better HP/Engine weight out of half (by your rating) or one fourth displacement is considerably more efficent wouldn't you say???

BlackRx7

its all about tunning your car and not having a heavy foot then you can get good gas milage, last week I got 17 mpg in my TII!!!! thats some conservative driving

Project RX-7

I am not sure what came first, the Festiva or the 121, but they all had Mazda engines, yes they were assembled by Kia and sold by Ford here, but i have some pictures of the 121 ( http://members.rogers.com/sofronov/C...86Festiva.html )

wes2k3

My compadre declares (and I quote)

" maybe I need to join and tell BlackRX7 that I got 34MPG in my Turbocoupe yesterday on my Chicago trip, with a bigger, heavier car than the RX-7's and still could fry the tires outta every tollbooth! and 1/2 of the trip was loaded with tires. 13 or 14 of them!"

OK

Orange!FD

What makes you think efficiency has anything to do with the number of "things" going on at one time? It doesn't. Efficiency has to do with how much of the fuel that goes in works to push the crankshaft around (in the case of fuel efficiency), or how much of the heat that comes from the burned fuel works to push the crankshaft around.
And if anyone is still in the dark about whether the rotary is efficient: It Is Not Efficient, relative to most piston engines, in either the fuel or thermodynamic senses. It's pretty efficient in the "horsepower per unit weight" sense, and that's why it's a good powerplant for a sports car.

flying taco

I agree with ya on that one... it is pretty thermodynamically inefficient... hopefully the renesis improves on this. I'd still rather have a rotary

Aaron

Josepi

I laugh at you. Your teh funny! I bet he shiftz mad quicK y0 right?

Buger

Hi Wes2k3,

Many people make the mistake that you are making. Each rotor will only have 1 combustion event per 1 revolution of the "crankshaft". Of course the rotary in the 84 rx-7 you were looking at has 2 rotors which would mean it has 2 combustion events (not 6) per revolution of the eccentric shaft.

In short, power can be increased by:
1: more displacement (diff in max vol and min vol per shaft rev)
2: better volumetric efficiency (more air/fuel in engine)
3: better thermal efficiency (better use of air/fuel)
4: better mechanical efficiency (less losses from engine)

I made a decent post explaining why the renesis makes more power than previous rotaries on the rx8forum but alas that forum is currently down because the increase of its use was bring the rx7club down.

Historically, rotaries have been less thermally efficient but more mechanically efficient than piston engines. Less thermally efficient mianly because the combustion "chamber" has more surface area that can disperse heat energy. This can be improved by the use of coatings that are less thermally conductive (ceramic alloys). This costs money but I believe it "cermet" was used in the rotary that won lemans. Rotaries have a longer expansion or power stroke than pison engines which mitigates the lessened thermal efficiency of the combustion area shape. The renesis engine has an even longer power stroke than previous rotaries because the exhaust port is opened later. This is one way that Mazda has improved the thermal efficiency of the new engine.

Rotaries are mechanically more efficient than piston engines. Of course most here are aware that not having camshafts and such means that a higher percentage of the engine power can be used to go to the driveshaft.

The overall efficiency of the renesis will be seen when the rx-8 comes out. It should be able to run leaner than piston engines at idle and low load conditions because there is no overlap in the intake and exhaust "strokes". Mazda has mentioned something like 15% more fuel efficient in real world situations which would translate to approx 19/28 mpg. The greatly increased voumetric efficiency (much larger ports) helps in higher end power although there is no overlap for scavenging.

As I asked in my earlier post, please research and advise how the 247 hp of the renesis compares to 2.6 liter piston engines?

Brian

KiyoKix

I'm a firm believer that the longer you have to study and reasearch an engine the better it will be...how long have they been doing piston engines...now how long has the rotary been around??? I'd say since we're staying with them in many things and kicking their asses in others we're doing pretty damn good for being infants.

Nathan Kwok

He is right, they are thermodynamically inefficient. I'm going to give another thumbs up for the combustion chamber shape, and also toss in the port overlap. Thats why they get such horrible fuel mileage. Without valves, you can't vary valve timing/lift like in newer psiton engines, so you have to make a compromise between port overlap and pumping losses . Big ports can make big power, but then you get horrible port overlap so low rpm operation is very inefficient. Small ports will work well down low, but then get choked out at high rpms. Renesis helps this a lot, but what would be really cool is implementing some way of dynamically changing port size/location/shape to maximize efficiency. The current workaround, at least on the intake side, is to have crazy induction systems with variable "stages" so you can at least tune the intake runner length, and multiple intake ports, but it'll still never have the same control you get with valves.

setzep

Who told you this? Turbos run off of exhaust heat as well as airflow.

Buger

Besides the renesis, what other production piston engine has no overlap? It may be misleading to point out overlap as a cause of previous rotaries fuel economy woes if all piston engines have overlap also?

The rotary actually offers greater flexibility in timing the intake and exhaust ports. What about an small intake port on the peripheral housing that opens only at high rpms? No overlap at low rpms, but a little overlap at high rpms to take advantage of scavenging? The renesis has 3 optimized ranges by using the dynamic effect of the intake pulses. How many piston engines are optimized for 3 different ranges? I know the s2000 has cams that optimize low and high rpms but it has a horrible middle range and only about 3000 rpms at 90% or greater torque.

The miller cycle was specifically made to reduce pumping losses. Which company put the miller cycle into a production car? I know that the miller cycle rotary was supposed to be a near future design in the 90s.

We will have to wait to see what the fuel economy of the rx-8 is before assuming that the rotary is simply less efficient than the piston. If the rx-8 gets 20/26 mpg, it will match the s2000 which is a smaller, lighter car with an engine that puts out less power and torque.

I certainly think that there is more that can be done with the engine. Because of the larger combustion surface area, advances in metals and coatings will yield much bigger improvements in the thermal efficiency of the rotary over pistons. It may be possible that they can be used now if it weren't for cost concerns.

Brian

KiyoKix

What kind of car do you drive because your info says none...? Where do you get your info from on why it's soo inefficient (besides the person sitting next to you)?

Here's the best reason that I can give you on why it's "inefficient"...

How long have you worked on/ or studied rotary engines?

How long have you worked on/or studied piston engines?

Now think about the time difference there, it's not that the rotary is inefficient it's that YOU (no offense) don't know how to use it! You'll never get the proper work from something you don't know how to use properly no matter what you do. Once you study how it works, what it can and can't do, what works and what doesn't work, you'll learn how to make something work efficiently.

Take that how you will, I'm not "lashing out" it's just simply the truth.

Orange!FD

Uhh, Brian, what the hell are you talking about? Each rotor has THREE (3) combustion events per revolution of the eccentric shaft (the crankshaft). If you need to go to http://www.rotaryengineillustrated.com or somewhere to figure this out, then do, but until you've at least glanced at a picture of a rotor in a housing with the stationary and rotor gears showing, don't be shooting your mouth off and causing even more confusion than there already is around here.

KevinK2

Better study that link more. Brian is correct, each rotor fires once per crank/eccentric rev. Rotor spins slower than crank, takes 3 crank revs for one rotor rev, so ea rotor will fire all 3 faces in 3 crank revs.

To topic:

thermally inefficient ... mostly due to large large surface area for combustion heat loss. Think about it .... at BDC position, a piston eng still has same chamber surface in head, while rotary has a totally different (cooler) surface. This results in higher bsfc (fuel usage per hp).

2.6L is most correct piston eng comparo. This is what all pro race series have used.

Piston engine displacement is historically based on total # pistons x stroke, but it takes 2 revs for all cylinders to fire all the 'displaced' intake air, for a 4 stroke.

Mazda defines rotary displacement differently, based on total intake air movement (@100%VE) in one crank rev of the engine. Each rotor will displace .65L of intake air in one crank rev. , which gives 1.3L per rev for the 2-rotor, or 2.6L for 2 revs for boinger comparo.

afaik, 250 hp for the new engine is only beat by the 240 hp 2L S2000, regarding hp/L for na production engine.

Regarding torque, the crank offset is only .6", vs 1.5"-2" for most boingers. This is the moment arm for torque production. But the rotary is helped by an effective stroke that is 50% greater than for a piston eng, as the active rotor face chases the eccentric offset for 270 degress of shaft rotation, vs 180 degrees for a piston engine.

Orange!FD

Well HELL. You're right about combustions/rev, Kevin. And thanks for the description of how to arrive at the 2.6l often used as a comparison to boingers, and about where the wankel makes up what would otherwise be a severe torque deficit.

And sorry about the rant, to Buger.

/gets cold crow from fridge for late night snack.

Flamin' NOS

In the S4 (87-88) TII's, they made 182 hp and 183 lb ft at 3500 rpms. How do you get a rotary to make a lot of torque? Add a turbo
steve