The RX-7 confirmed to be in the pipeline for 2017---RX-Vision Unveil!!
01-11-14, 09:31 AM
#976
If the new Miata is 200+ horsepower, I don't see the point in a 250 hp 1.2 liter rotary either. What happened to the "larger" 16x?! Slap a supercharger on the Miata's motor and be done with it.
Why bother? Again, Mazda is so ball-less.
Why bother? Again, Mazda is so ball-less.
Last edited by ptrhahn; 01-11-14 at 09:36 AM.
01-11-14, 09:43 AM
#977
How would they improve low end torque with a slightly smaller displacement? A few things:
1) Faster, more efficient combustion. The Renesis and older 13B's have very slow, very crappy combustion. The new combustion chamber shapes they have been exploring since the 16X concept will help with this.
2) Knock relief. This is helped by the faster, more efficient combustion, and will be helped by direct injection.
3) I know nobody wants to hear it, but a lower revving engine. I predict that any new rotary engine will be equal or lower revving than a Renesis. The Renesis had a 5 stage intake system (individual staging of primary, secondary, aux ports, + runner length switching and intake duct length switching). That's complicated, expensive, and unreliable.
Piston engines are moving toward lower revving with better combustion. It's unlikely that a new rotary would be too different from that. If you can simplify everything and make the engine lower revving, it will be easier to make low end torque.
Euro 6C, California LEV III, and CAFE regulations happened. Just to put things into perspective: The Renesis used basically every trick in the book to pass a very basic emissions standard (California LEV II-ULEV). It had a smog pump, air assisted port injection, staged injectors, HC trap catalyst. Those are VERY expensive technologies that are normally found in ultra-clean piston engines. They had to throw everything at the Renesis that was available about 12 years ago in order to make it pass California LEV II emissions.
1) Faster, more efficient combustion. The Renesis and older 13B's have very slow, very crappy combustion. The new combustion chamber shapes they have been exploring since the 16X concept will help with this.
2) Knock relief. This is helped by the faster, more efficient combustion, and will be helped by direct injection.
3) I know nobody wants to hear it, but a lower revving engine. I predict that any new rotary engine will be equal or lower revving than a Renesis. The Renesis had a 5 stage intake system (individual staging of primary, secondary, aux ports, + runner length switching and intake duct length switching). That's complicated, expensive, and unreliable.
Piston engines are moving toward lower revving with better combustion. It's unlikely that a new rotary would be too different from that. If you can simplify everything and make the engine lower revving, it will be easier to make low end torque.
Euro 6C, California LEV III, and CAFE regulations happened. Just to put things into perspective: The Renesis used basically every trick in the book to pass a very basic emissions standard (California LEV II-ULEV). It had a smog pump, air assisted port injection, staged injectors, HC trap catalyst. Those are VERY expensive technologies that are normally found in ultra-clean piston engines. They had to throw everything at the Renesis that was available about 12 years ago in order to make it pass California LEV II emissions.
01-11-14, 09:57 AM
#980
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I don't think that's an accurate comparison.
I've put over half a million miles on my piston-engined cars, most of which I've tracked regularly, and never had an unprovoked engine failure. I did run the Z low on oil at the track once, and wasn't running a proper baffled pan. That ended badly, spent ~$3200 on the rebuild (including some custom stuff like machining reliefs in the pistons and also a Nismo 8 quart pan with swinging plates). Then several years later one of the carburetor bolts backed off and i got an air leak and holed a couple of pistons, spent $1500 to fix that (other 4 cylinders were fine). Both of those were clearly owner/crew chief/operator (me/me/me) error, and didn't cost anything like $10k to set right.
For the record, the 240Z was by far my most tracked car (~150 track days), and while it a street car, it's pretty "high-performance". 3.1 liter, 11.5:1 CR, 3x2 45mm carbs, 255rwhp at 6500rpm, rev limit 7200. I should never have traded it for the FD, I should have scraped together more $$$ and kept it :cry:
Absent any neglect, the piston engines I've owned are known to last pretty much for fooking EVER. Meanwhile the rotary I owned (not tracked, only autoXed once) died for no external cause at 103k and not even the most diehard rotory-fans (of which I am one!) or apologists finds that unusual or remarkable. Because it wasn't. They just don't last.
12A might be a different story, but doesn't exactly have the beans to pull the skin off a grape, either...
But *anyway*, here's hoping for a new improved rotary-engined RX7! And a piston-engine MX-7 variant. But also a rotary RX-5. I'd like to see all of those
I've put over half a million miles on my piston-engined cars, most of which I've tracked regularly, and never had an unprovoked engine failure. I did run the Z low on oil at the track once, and wasn't running a proper baffled pan. That ended badly, spent ~$3200 on the rebuild (including some custom stuff like machining reliefs in the pistons and also a Nismo 8 quart pan with swinging plates). Then several years later one of the carburetor bolts backed off and i got an air leak and holed a couple of pistons, spent $1500 to fix that (other 4 cylinders were fine). Both of those were clearly owner/crew chief/operator (me/me/me) error, and didn't cost anything like $10k to set right.
For the record, the 240Z was by far my most tracked car (~150 track days), and while it a street car, it's pretty "high-performance". 3.1 liter, 11.5:1 CR, 3x2 45mm carbs, 255rwhp at 6500rpm, rev limit 7200. I should never have traded it for the FD, I should have scraped together more $$$ and kept it :cry:
Absent any neglect, the piston engines I've owned are known to last pretty much for fooking EVER. Meanwhile the rotary I owned (not tracked, only autoXed once) died for no external cause at 103k and not even the most diehard rotory-fans (of which I am one!) or apologists finds that unusual or remarkable. Because it wasn't. They just don't last.
12A might be a different story, but doesn't exactly have the beans to pull the skin off a grape, either...
But *anyway*, here's hoping for a new improved rotary-engined RX7! And a piston-engine MX-7 variant. But also a rotary RX-5. I'd like to see all of those
In the race world NA rotary engines last longer than NA piston engines and I'm sure we don't need to argue that one.
Your 150 day piston engine was either very low on compression or not driven hard. Even guys racing in honda challenge or your typical sm miata will need a new engine every 3 or 4 years with much less days than 150 days and guys on the podium every 2 years minimum.
Spec Miata Community: How Long will a "Pro Motor" Last?
Not buying what you are selling
01-11-14, 10:09 AM
#981
You may be right as well may never know the carbon effects or long term wear on ceramics. Now I do feel there is a major difference in how carbon sticking effects a 3 piece seal vs a 2 piece. On a 3 piece, the carbon can lock down the bottom piece leaving the top piece and corner piece to free float and bounce around the housing (not good). It's harder for carbon to lock down a 2 piece seal because you simply have less cracks and crevices for carbon to get into. So theoretically, a 2 piece ceramic seal "should" out perform a 3 piece seal When it comes to carbon sticking.
01-11-14, 10:22 AM
#982
Absent any neglect, the piston engines I've owned are known to last pretty much for fooking EVER. Meanwhile the rotary I owned (not tracked, only autoXed once) died for no external cause at 103k and not even the most diehard rotory-fans (of which I am one!) or apologists finds that unusual or remarkable. Because it wasn't. They just don't last.
12A might be a different story, but doesn't exactly have the beans to pull the skin off a grape, either...
We've both had bad experiences but I had great experiences as well. Now the reliability over the past 28yrs or so isn't what it was. That's a fact! However I feel that bad reliability is directly the result of Mazda changing the apex seals and not the engine design itself. That 3 piece design doesn't allow for that kind of long term durability. My fd rx7 made it to 108k on the original engine until I blew it from over boosting but, even I knew it was still a ticking time bomb. After pulling it apart, the top piece seal was uncomfortably thin so they were gonna give out regardless. Now I know of a rebuilt sequential twin turbo that was built by Rotary Performance with 3mm 2 piece seals that makes 330 rwhp and has over 100k on that rebuild. I drove it on the tail end of that mileage and that engine had zero signs of compression problems. To me that's astounding longevity for the hp that little engine is making. So the rotary design is very capable of having lots of power long term if built an tuned correctly. Also you remember know one said anything about power when we were comparing the long term durability of production rotarys that lasted over 200k. 12a may not have had the power to pull the skin off a grape but, so didn't every other performance car of that period as well.
01-11-14, 10:36 AM
#983
Full Member
No disrespect intended, you don't seem to have a good grasp of fundamental engine knowledge. There are several ways to skin a cat. Engineers know this, Mazda know this. Consider just how far outputs of piston engines have come in the last 15 years. Flywheel power of 250 hp compared to 240 for the reny is very much within reach.
What I tried to say (and the fact that English is not my mother tongue could be part of the problem) is that if one of their goals is to increase torque (and, thus also power) at every engine speed, reducing the displacement is not exactly one of the first methods that come to mind.
No doubt, they can do it though.
Andrea.
01-11-14, 11:36 AM
#984
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3) I know nobody wants to hear it, but a lower revving engine. I predict that any new rotary engine will be equal or lower revving than a Renesis. The Renesis had a 5 stage intake system (individual staging of primary, secondary, aux ports, + runner length switching and intake duct length switching). That's complicated, expensive, and unreliable.
Piston engines are moving toward lower revving with better combustion. It's unlikely that a new rotary would be too different from that. If you can simplify everything and make the engine lower revving, it will be easier to make low end torque..
Piston engines are moving toward lower revving with better combustion. It's unlikely that a new rotary would be too different from that. If you can simplify everything and make the engine lower revving, it will be easier to make low end torque..
lower apex seal speed should = less wear.
if i was designing a rotary, i would have a ~7000rpm redline, with a slightly lower seal speed than a 13B.
01-11-14, 12:19 PM
#985
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Im just keeping my fingers cross they toss a three rotor in it. That's all they have to do to make an awesome car worthy of being the next gen rx7, I dont know why they ***** foot around with thoughts of putting in underpowered engines
01-11-14, 12:35 PM
#986
As for rotary turbo and reliability.
Most people who can afford a rx7 build 400+hp machines and the ones that are done right last a long time. A friends FD was tuned by an ******* with the original motor and ran 12.00@118 on street tires with a rookie driver. It had over 100k miles on the original motor and only suffered a pulsation damper leak. It's not the hp that kills the motor.
I'm sure there are a few well built 300whp rx7s that will live well over 100k on a rebuild because there well below the risk of knock/detonation.
Most people who can afford a rx7 build 400+hp machines and the ones that are done right last a long time. A friends FD was tuned by an ******* with the original motor and ran 12.00@118 on street tires with a rookie driver. It had over 100k miles on the original motor and only suffered a pulsation damper leak. It's not the hp that kills the motor.
I'm sure there are a few well built 300whp rx7s that will live well over 100k on a rebuild because there well below the risk of knock/detonation.
01-11-14, 01:58 PM
#988
As for rotary turbo and reliability.
Most people who can afford a rx7 build 400+hp machines and the ones that are done right last a long time. A friends FD was tuned by an ******* with the original motor and ran 12.00@118 on street tires with a rookie driver. It had over 100k miles on the original motor and only suffered a pulsation damper leak. It's not the hp that kills the motor.
I'm sure there are a few well built 300whp rx7s that will live well over 100k on a rebuild because there well below the risk of knock/detonation.
Most people who can afford a rx7 build 400+hp machines and the ones that are done right last a long time. A friends FD was tuned by an ******* with the original motor and ran 12.00@118 on street tires with a rookie driver. It had over 100k miles on the original motor and only suffered a pulsation damper leak. It's not the hp that kills the motor.
I'm sure there are a few well built 300whp rx7s that will live well over 100k on a rebuild because there well below the risk of knock/detonation.
You are right but still consider the 3 piece designs inherent flaw. Even if all the conditions are perfect, there is no way possible for that seal to last well into 100+k range. You can only wear that top piece down so much before it pops out of the rotor grove. They are a ticking time bomb when they get thin and brittle and I pray Mazda never uses them again.
01-11-14, 02:09 PM
#989
Manufacturers tune for all those conditions. Why do you think the factory a/f was so rich during WOT? Mazda new that the extra fuel saturation would suppress the potential of detonation if someone ran 87 octane. I actually had been driving with 87 in my tank for the last year and 1/2 before I blew that original engine. Had my boost levels stayed in the factory safe 10psi zone, my engine would have never blown that day. It was that spike to 12psi that did the damage.
01-11-14, 02:47 PM
#990
Senior Member
In the race world NA rotary engines last longer than NA piston engines and I'm sure we don't need to argue that one.
Your 150 day piston engine was either very low on compression or not driven hard.
The engine was driven very hard indeed, every shift near 7200rpm rev limit. 11.5:1 CR on pump gas with full ignition advance, but very conservative a/f mixture at ~11.5:1.
Not buying what you are selling
01-11-14, 03:31 PM
#991
my FC made it close to 80k/10 years with over 300whp on the last engine(still in the car, waiting on transplant). rebuilt with all parts having over 100k on them already. it isn't dead either but it isn't exactly healthy, but if driven modestly i'm sure it could go another 50k miles if i tried to stretch it out. of course all the often replaced items were replaced during the rebuild like all rotor hardware, bearings and soft seals in the engine.
the original engine died at 136k from electrolysis due to a poorly maintained cooling system, the rotor housings had to be replaced so i found a set of good used ones back before i started this whole journey into rebuilding these engines.
the original engine died at 136k from electrolysis due to a poorly maintained cooling system, the rotor housings had to be replaced so i found a set of good used ones back before i started this whole journey into rebuilding these engines.
Last edited by RotaryEvolution; 01-11-14 at 03:33 PM.
01-11-14, 06:39 PM
#992
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A lot of 13Bs in the FC and RX-8 lived a very short life as well. Including mine
I won't try to because I don't have any info on that, other than that it was at an autoX event where my FC's engine expired.
I looked back at my results with the club, and 150 track days (rough estimate based on average 8 track days/year back to 1995) is embarrassingly far off. I did 52 2-day events with COM in that time, but only 31 of them in the Z, +15 non-COM HPDEs in the Z, so only about 75 or so track days on the 240Z, with the one total rebuild (precipitated by running it low on oil before I had a baffled pan) back in 2003. Typically get at least an hour of track time per day, fwiw.
The engine was driven very hard indeed, every shift near 7200rpm rev limit. 11.5:1 CR on pump gas with full ignition advance, but very conservative a/f mixture at ~11.5:1.
I'm certainly not buying the idea that rotaries are as long-lived or reliable as decent piston engine cars, at least for dual use. For developed racing engines, I don't have enough info to have an opinion. But my money would still be on an L6 over an NA 13B at similiar power levels, NA vs. NA or turbo vs. turbo.
I won't try to because I don't have any info on that, other than that it was at an autoX event where my FC's engine expired.
I looked back at my results with the club, and 150 track days (rough estimate based on average 8 track days/year back to 1995) is embarrassingly far off. I did 52 2-day events with COM in that time, but only 31 of them in the Z, +15 non-COM HPDEs in the Z, so only about 75 or so track days on the 240Z, with the one total rebuild (precipitated by running it low on oil before I had a baffled pan) back in 2003. Typically get at least an hour of track time per day, fwiw.
The engine was driven very hard indeed, every shift near 7200rpm rev limit. 11.5:1 CR on pump gas with full ignition advance, but very conservative a/f mixture at ~11.5:1.
I'm certainly not buying the idea that rotaries are as long-lived or reliable as decent piston engine cars, at least for dual use. For developed racing engines, I don't have enough info to have an opinion. But my money would still be on an L6 over an NA 13B at similiar power levels, NA vs. NA or turbo vs. turbo.
No arguing that the LSX is a good engine but they are also known to die at the track especially at your power levels.
I think the RX8 GT car was known to be the most reliable of the class so my guess is it would outlast the LS6. As time goes by I think I'll eventually have a nice reliable engine in my car that's not cobbled together along with a tried and true setup which I pretty much already have and I believe I'll get into p car reliability like 5 or 6 years on an engine. These days I get about 3 seasons which isn't too shabby and the last two engines still had compression they were just getting tired from warped apex seals (too much heat) if I can get that figured out (possibly just use ceramics) the engine should be very durable but it's a turbo so I still have to deal with all the other mess.
I'd drop an LS6 or 7 in my car BUT by the time I'm done dealing with all the BS attached to making 400 HP and 400 plus torque IE; wide body, wheels, braces, brakes etc...etc... I'd just buy someone else's well prepped VETTE and give the engine a proper home although if one of these days I find a really well done FD then hey I may pull the trigger (you selling....jk hehe)
01-11-14, 07:00 PM
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How would they improve low end torque with a slightly smaller displacement? A few things:
1) Faster, more efficient combustion. The Renesis and older 13B's have very slow, very crappy combustion. The new combustion chamber shapes they have been exploring since the 16X concept will help with this.
2) Knock relief. This is helped by the faster, more efficient combustion, and will be helped by direct injection.
3) I know nobody wants to hear it, but a lower revving engine. I predict that any new rotary engine will be equal or lower revving than a Renesis. The Renesis had a 5 stage intake system (individual staging of primary, secondary, aux ports, + runner length switching and intake duct length switching). That's complicated, expensive, and unreliable.
Piston engines are moving toward lower revving with better combustion. It's unlikely that a new rotary would be too different from that. If you can simplify everything and make the engine lower revving, it will be easier to make low end torque.
Euro 6C, California LEV III, and CAFE regulations happened. Just to put things into perspective: The Renesis used basically every trick in the book to pass a very basic emissions standard (California LEV II-ULEV). It had a smog pump, air assisted port injection, staged injectors, HC trap catalyst. Those are VERY expensive technologies that are normally found in ultra-clean piston engines. They had to throw everything at the Renesis that was available about 12 years ago in order to make it pass California LEV II emissions.
1) Faster, more efficient combustion. The Renesis and older 13B's have very slow, very crappy combustion. The new combustion chamber shapes they have been exploring since the 16X concept will help with this.
2) Knock relief. This is helped by the faster, more efficient combustion, and will be helped by direct injection.
3) I know nobody wants to hear it, but a lower revving engine. I predict that any new rotary engine will be equal or lower revving than a Renesis. The Renesis had a 5 stage intake system (individual staging of primary, secondary, aux ports, + runner length switching and intake duct length switching). That's complicated, expensive, and unreliable.
Piston engines are moving toward lower revving with better combustion. It's unlikely that a new rotary would be too different from that. If you can simplify everything and make the engine lower revving, it will be easier to make low end torque.
Euro 6C, California LEV III, and CAFE regulations happened. Just to put things into perspective: The Renesis used basically every trick in the book to pass a very basic emissions standard (California LEV II-ULEV). It had a smog pump, air assisted port injection, staged injectors, HC trap catalyst. Those are VERY expensive technologies that are normally found in ultra-clean piston engines. They had to throw everything at the Renesis that was available about 12 years ago in order to make it pass California LEV II emissions.
I'm certainly not buying the idea that rotaries are as long-lived or reliable as decent piston engine cars, at least for dual use. For developed racing engines, I don't have enough info to have an opinion. But my money would still be on an L6 over an NA 13B at similiar power levels, NA vs. NA or turbo vs. turbo.
Last edited by Bwarrrrrp; 01-11-14 at 07:06 PM.
01-11-14, 07:30 PM
#994
Senior Member
No arguing that the LSX is a good engine but they are also known to die at the track especially at your power levels.
I think the RX8 GT car was known to be the most reliable of the class so my guess is it would outlast the LS6.
For similar power potential to a hot LS build, you need a 4-rotor, turbo 3-rotor, or *severely* turbo'd 2-rotor!
These days I get about 3 seasons which isn't too shabby
I'd drop an LS6 or 7 in my car BUT by the time I'm done dealing with all the BS attached to making 400 HP and 400 plus torque IE; wide body, wheels, braces, brakes etc...etc... I'd just buy someone else's well prepped VETTE and give the engine a proper home although if one of these days I find a really well done FD then hey I may pull the trigger (you selling....jk hehe)
LS3 would be the way to go, though, IMO. Better basis than the older LS6, and with just a cam you have LS7 horsepower for WAY less money! When/if I ever have to rebuild (knock on wood) I'd probably just buy an LS3 hot cam crate motor from GM and sell my old engine.
01-11-14, 10:43 PM
#995
And you would be wrong. They may not have the same resistance to running cold that piston engines do, but they are virtually bulletproof engines and can run at full throttle all week as long as it gets enough life saving air to stay cool. Don't believe me? Put a stock sr20 or 2jz in a plane and see how long it lives.
Really loving that example.
01-11-14, 11:02 PM
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01-12-14, 04:17 AM
#998
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01-12-14, 05:48 AM
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Lycomings and Continentals, yes - dedicated plane engines. Car engines not so much, which is the only way to compare apples to apples. Like I said, find me a plane with a sr20 or 2jz installed.Edit: some experimentals have EJ22, EJ25's installed, they are much easier to cool.
Last edited by Bwarrrrrp; 01-12-14 at 06:13 AM.
01-12-14, 07:26 AM
#1000
Senior Member
I'm seeing subaru engines, Honda Fit, air-cooled VW, Mercedes Benz turbodiesel, a fair number of car piston engines in aircraft. Several articles I found on the subject of automobile engines in aircraft didn't even mention rotaries. I wouldn't bet on rotaries outnumbering pistons for car engines used in aircraft.
But the point is moot at best. We may as well also consider how many automotive-based rotary engines you see vs. automotive-based piston engines in powerboats.
There may be some compelling argument for rotaries in applications where high-power constant-speed operation is the norm, which would argue for their use in aircraft, but not be relevant for use in cars.
Again, I should state that I'm a fan of rotaries and hope to see new rotary cars from Mazda or others. I just don't see a need to argue that they're necessarily *better* all-around, or that they're more reliable. My impression remains that they have been LESS reliable and shorter-lived in production car applications.
But the point is moot at best. We may as well also consider how many automotive-based rotary engines you see vs. automotive-based piston engines in powerboats.
There may be some compelling argument for rotaries in applications where high-power constant-speed operation is the norm, which would argue for their use in aircraft, but not be relevant for use in cars.
Again, I should state that I'm a fan of rotaries and hope to see new rotary cars from Mazda or others. I just don't see a need to argue that they're necessarily *better* all-around, or that they're more reliable. My impression remains that they have been LESS reliable and shorter-lived in production car applications.