So, you want to build your own engine...
09-04-2013, 05:06 PM
#26
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I you want to talk about the idea or theory of such an engine being designed/constructed that is fine, but that is not what your title lends to your intention. "So, you want to build your own engine..." It bludgeons through the vision of a mad scientist in is garage/basement/methlab constructions some ridiculous monstrosity that he thinks is both ingenious and world changing just before he cranks it up and blows himself to pieces.
09-04-2013, 05:30 PM
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you want to get the people who make the parts together
aluminum rotors and titanium rotors have been done, aluminum side housings are being sold today. E-shafts have been machined custom too. some folks/companies have worked on the rotor housings. the problem is all these company's are small and secretive.
the high prices of stuff and scattered locations of shops have led to a lot of DIY and figure it out yourself mentality in the rotary community.
if some rich person purchased all the shops and had them work together there would be a "crate rotary engine" but for now I can't see it happening.
as far as new motors you can sign up for mazdaspeed racing or something and get engine parts with a hefty discount. still a reman at 2k with a 1k core exchange is hard to beat
aluminum rotors and titanium rotors have been done, aluminum side housings are being sold today. E-shafts have been machined custom too. some folks/companies have worked on the rotor housings. the problem is all these company's are small and secretive.
the high prices of stuff and scattered locations of shops have led to a lot of DIY and figure it out yourself mentality in the rotary community.
if some rich person purchased all the shops and had them work together there would be a "crate rotary engine" but for now I can't see it happening.
as far as new motors you can sign up for mazdaspeed racing or something and get engine parts with a hefty discount. still a reman at 2k with a 1k core exchange is hard to beat
You don't need to assume E85 as the base gasoline. All E85 does is allow higher compression. Mazda is achieving higher compression on 87 octane through a lot of really creative and ingenious methods. Are you ignoring those methods and benefits? Most of them can be applied to the rotary, and indeed, Mazda has officially noted that there is a "Sky-R" within the company.
09-04-2013, 05:42 PM
#28
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I did really write figure-8, didn't I? I wanted to write something like "round shape thingy with really squashed middle bit", which would have sounded really dumb, but at least would not have been misleadingly incorrect.
09-04-2013, 06:13 PM
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On a forum, we can only communicate text so what words you select to convey your meaning become quite important. 
All 13b engines use the same rotor width. The 16x design narrows it back to 12a width, though with a much longer stroke.
All 13b engines use the same rotor width. The 16x design narrows it back to 12a width, though with a much longer stroke.
09-04-2013, 06:45 PM
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Instead of adding rotors for more displacement someone might have made them and the housings wider. The question is of course which problems they ran into, because if Mazda is making them narrower for their new engine, then a "So, you want to build you own engine..."-engine should naturally search for a solution in the opposite direction. It is clear that it is postulated that Mazda is making the right decisions with wrong objectives. Otherwise, nobody would be interested in building their own engine in the first place.
09-04-2013, 07:14 PM
#32
The 13b is already to wide to begin with, hence the 16x is going back to the 12a width.
Making one rotor wider to keep the same displacement asks for more problems then its worth, one being harmonic balance. The other being seal flex and the failure to properly lubricate the entire seal width.
The longer this thread gets the worse the theory is butchered.
But at least it is amusing. Grab a simple text book and we are somehow smarter than hundreds of engineers who dedicated decades of R&D it's without a doubt in my and everyone else's mind that all these theories have been researched and failed to make strides because the basic mechanical properties are being ignored.
Just because the operation of a rotary engine is far simpler than a conventual combustion engine does not mean it is cheaper to produce. You are comparing barely 40,000 units per year in peak sales to over 1,000,000 V8 variants sold per year.
Again supply and demand dictates the market value, not the simplicity.
And although the engine functions simply the manufacturing process involved in producing an engine is far more complex and requires more involved processes.
Your argument is this box contains 40 parts and cost $1500, compared to his box contains 6 and costs $6,000 is an argument that fails to ask. What's in the box? You are not taking all variables into consideration
Making one rotor wider to keep the same displacement asks for more problems then its worth, one being harmonic balance. The other being seal flex and the failure to properly lubricate the entire seal width.
The longer this thread gets the worse the theory is butchered.
But at least it is amusing. Grab a simple text book and we are somehow smarter than hundreds of engineers who dedicated decades of R&D it's without a doubt in my and everyone else's mind that all these theories have been researched and failed to make strides because the basic mechanical properties are being ignored.
Just because the operation of a rotary engine is far simpler than a conventual combustion engine does not mean it is cheaper to produce. You are comparing barely 40,000 units per year in peak sales to over 1,000,000 V8 variants sold per year.
Again supply and demand dictates the market value, not the simplicity.
And although the engine functions simply the manufacturing process involved in producing an engine is far more complex and requires more involved processes.
Your argument is this box contains 40 parts and cost $1500, compared to his box contains 6 and costs $6,000 is an argument that fails to ask. What's in the box? You are not taking all variables into consideration
Last edited by Carbon8; 09-04-2013 at 07:18 PM.
09-04-2013, 07:35 PM
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On a forum, reading between the lines can also be quite important.
Instead of adding rotors for more displacement someone might have made them and the housings wider. The question is of course which problems they ran into, because if Mazda is making them narrower for their new engine, then a "So, you want to build you own engine..."-engine should naturally search for a solution in the opposite direction. It is clear that it is postulated that Mazda is making the right decisions with wrong objectives. Otherwise, nobody would be interested in building their own engine in the first place.
Instead of adding rotors for more displacement someone might have made them and the housings wider. The question is of course which problems they ran into, because if Mazda is making them narrower for their new engine, then a "So, you want to build you own engine..."-engine should naturally search for a solution in the opposite direction. It is clear that it is postulated that Mazda is making the right decisions with wrong objectives. Otherwise, nobody would be interested in building their own engine in the first place.
I have no problem with "new theories". But please, at least stand on the information of those ahead of you. I'm not interested in waiting 50 years for your version to make it to production.
Doesn't mean that I am saying to get blinders on and follow theories, but to at least use the practical real life information available. Lots of creative options out there. Mazda is nothing if not inventive with "wacked out" ideas that they figure out how to make work.
09-04-2013, 07:42 PM
#36
09-04-2013, 07:43 PM
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If you lump everyone on the forum into the same bucket, then yeah, it looks a bit odd. If you actually take a look at who is responding, and how they deal with new members in the past / other situations, no one here has yet responded out of character.
So nothing is odd yet imo.
So nothing is odd yet imo.
09-04-2013, 07:49 PM
#38
If you lump everyone on the forum into the same bucket, then yeah, it looks a bit odd. If you actually take a look at who is responding, and how they deal with new members in the past / other situations, no one here has yet responded out of character.
So nothing is odd yet imo.
So nothing is odd yet imo.
09-04-2013, 09:18 PM
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In order for a wider rotor to work, you need to add more spark plugs (or ignition sources, to be accurate since it could be laser driven) to ignite along a longer front. Otherwise you are just wasting combustion that isn't pushing against anything. The narrower rotor is as wide as you can actually go before you aren't gaining anything because the flame front isn't even getting to the edges of the apex seal as happens with all 13b engines. This didn't matter on the RX-7s, peripheral port, lower emissions, etc... The RX-8's side ports solve much of the problem of wasted fuel, but it is still wasting a fair amount that isn't pushing on anything.
I did not find any information in Yamamoto's book about the limiting factors of rotor thickness.
Some of the posters here are satisfied that Mazda didn't make thicker rotors and asking what would happen if one had thicker rotors is blasphemy. I would really like to know what exactly the problem was. Bending e-shaft? I doubt it.
09-05-2013, 10:01 AM
#43
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Going with 1 wider rotor instead of 2 narrower rotors of the same width doesn't save you anything since you still need the same number of ignition sources, fuel injectors, oil injectors, etc... All that happens is you subtract 6 corner seals, 6 side seals, add a bunch of weight to counterbalance it. And assuming you aren't ignoring the emissions regulations that exist today, you lose at least 25% of the exhaust port area with subtracting the center iron exhaust ports. You also lose the ability for 1 rotor to accelerate the air velocity on the 2nd rotor, which is a noticeable power gain.
09-05-2013, 10:32 AM
#44
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Hence another reason for my bewilderment of someone spending an afternoon on Wikipedia and suddenly thinking they came up with something that the engineers at Mazda (that have spent the last 40 years developing rotary engine) never considered.
No, the people that found a way to apply their ideas to the existing world shaped the world I live in. There are plenty of people with ideas that have had zero effect on the world.
If you lump everyone on the forum into the same bucket, then yeah, it looks a bit odd. If you actually take a look at who is responding, and how they deal with new members in the past / other situations, no one here has yet responded out of character.
So nothing is odd yet imo.
So nothing is odd yet imo.
Last edited by bladeiai; 09-05-2013 at 10:41 AM.
09-05-2013, 04:17 PM
#45
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I'm curious why you would have 1 rotor that is 160mm wide (current width of the Renesis x2) with 4 spark plugs for the rotor to get equal ignition across the entire width, AND having to figure out how to counter balance it, rather than having 2 80mm wide rotors with the same 4 spark plugs and no counterbalance problem?
Going with 1 wider rotor instead of 2 narrower rotors of the same width doesn't save you anything since you still need the same number of ignition sources, fuel injectors, oil injectors, etc... All that happens is you subtract 6 corner seals, 6 side seals, add a bunch of weight to counterbalance it. And assuming you aren't ignoring the emissions regulations that exist today, you lose at least 25% of the exhaust port area with subtracting the center iron exhaust ports. You also lose the ability for 1 rotor to accelerate the air velocity on the 2nd rotor, which is a noticeable power gain.
Going with 1 wider rotor instead of 2 narrower rotors of the same width doesn't save you anything since you still need the same number of ignition sources, fuel injectors, oil injectors, etc... All that happens is you subtract 6 corner seals, 6 side seals, add a bunch of weight to counterbalance it. And assuming you aren't ignoring the emissions regulations that exist today, you lose at least 25% of the exhaust port area with subtracting the center iron exhaust ports. You also lose the ability for 1 rotor to accelerate the air velocity on the 2nd rotor, which is a noticeable power gain.
Peripheral exhaust port area is proportional to rotor width. If the rotor is light enough, counterbalancing can be achieved weighting the e-shaft internally on the side opposite the rotor.
Even with one rotor, there still is always a power stroke. For comparison, the Ducati Panigale has two 112 mm × 60.8 mm pistons and runs fine with a powerstroke occurring only half the time.
Of course emissions regulations that exists today are only a secondary concern. An engine that doesn't run at all has no emissions. As soon as Lithium-Air power sources are available, internal combustion engines will be going the way of the horse, anyway.
If you want something worthwhile doing why do something a team of top engineers is already doing?
09-05-2013, 04:30 PM
#46
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Your argument here is rather ... flawed.
Agreed. But why do something that they tried 40 years ago either? Why not try something new? And if you don't know what they have tried, then why not research what they have tried FIRST, so you don't waste the effort on something that was already discarded?
09-06-2013, 06:47 AM
#47
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Regardless of how light the rotor gets, counter-weighting always means that additional weight is there. It doesn't have to be 1:1 of course, you can change the distance out from the rotational center to achieve the same balance with a different weight... but you are still adding weight, and that weight has a physical space to occupy, and has to have room to spin within additional space.
At zero eccentricity we obviously need zero balancing. Now, when we increase the eccentricity by moving the rotor center outward, we only need to balance by moving a counter weight into the other direction of that fixed axis. If the e-shaft is a hollow, this could be simply achieved by making the opposite wall thicker. The highest counter balance we could achieve is by filling half of an infinity thin-walled shaft with tungsten.
Please realize that even an engine with two rotors 180 degrees apart will require some form of balancing as the front and rear parts of the engine will otherwise gyrate around the center.
Wait, you are confusing the hell out of me. You only think this engine is viable because it doesn't exist? If you are proposing to actually build this engine to use, it needs to meet emissions regulations. I don't think Mazda would have gotten far if they made the Renesis Peripheral Port and then prevented the RX-8 from starting so as to prevent any emissions.
However, a $50 beaglebone black with a $20 ignition circuit can trigger a plug accurately every 250ns. Now, one of the features of the Wankel engine is that the rotor pushes the entire volume of gas past the plugs. Depending on temperature, throttle position and gradient, injector timing, etc. there will be an optimal sequence of firing each plug.
People like Carbon8 think they tried this (probably because they are so awesome that they had a time machine and could decide not to use a Motorola EEC III and EFI, because they tried it) as Mazda is not using multispark, and only an exceptionally stupid idiot like me could dream up something that exceptionally stupid.
I am not so sure.
Remember, the Cray-1 from 1976 has a processing power of 80 megaflops and cost $5 million. The AM335x system-on-a-chip with an ARM Cortex A8 uprocessor (the one on the $50 beaglebone) has a processing power of 1600 megaflops.
The general idea is that a leaner burn will require a higher A/F ratio around the spark plug and we could choose enrich the A/F ratio around the center spark plug(s).
09-06-2013, 07:54 AM
#48
At zero eccentricity we obviously need zero balancing. Now, when we increase the eccentricity by moving the rotor center outward, we only need to balance by moving a counter weight into the other direction of that fixed axis. If the e-shaft is a hollow, this could be simply achieved by making the opposite wall thicker. The highest counter balance we could achieve is by filling half of an infinity thin-walled shaft with tungsten.
Well, I did read the book by Kenichi Yamamoto and they tried a lot but certainly didn't try everything. For example, manufacturing the chamber out of a steel sheet and pouring aluminium around it does work, but applying a thin layer of chrome decreases the wear so significantly, that omitting the electroplating step hardly makes any sense.
However, a $50 beaglebone black with a $20 ignition circuit can trigger a plug accurately every 250ns. Now, one of the features of the Wankel engine is that the rotor pushes the entire volume of gas past the plugs. Depending on temperature, throttle position and gradient, injector timing, etc. there will be an optimal sequence of firing each plug.
People like Carbon8 think they tried this (probably because they are so awesome that they had a time machine and could decide not to use a Motorola EEC III and EFI, because they tried it) as Mazda is not using multispark, and only an exceptionally stupid idiot like me could dream up something that exceptionally stupid.
I am not so sure.
However, a $50 beaglebone black with a $20 ignition circuit can trigger a plug accurately every 250ns. Now, one of the features of the Wankel engine is that the rotor pushes the entire volume of gas past the plugs. Depending on temperature, throttle position and gradient, injector timing, etc. there will be an optimal sequence of firing each plug.
People like Carbon8 think they tried this (probably because they are so awesome that they had a time machine and could decide not to use a Motorola EEC III and EFI, because they tried it) as Mazda is not using multispark, and only an exceptionally stupid idiot like me could dream up something that exceptionally stupid.
I am not so sure.
Your arguments defy the basis of mechanical properties and real world applications, their is really no need to prove your statements wrong as most contradict each-other.
Maybe you should have spent 2 days reading that text-book instead of one, or better yet why don't you grab a wrench and actually take a look at one of these engine (presumably for the first time)
Then Im sure you would be able to build a motor that defies the principals of mechanics
Last edited by Carbon8; 09-06-2013 at 08:00 AM.
09-06-2013, 09:05 AM
#49
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For a rotor with central symmetry the center of mass is fixed at a point offset from the e-shaft. I took me a while to realize that this really is the case. It's rather obvious when you ignore everything else and mentally replace the triangular rotor with a disk.
At zero eccentricity we obviously need zero balancing. Now, when we increase the eccentricity by moving the rotor center outward, we only need to balance by moving a counter weight into the other direction of that fixed axis. If the e-shaft is a hollow, this could be simply achieved by making the opposite wall thicker. The highest counter balance we could achieve is by filling half of an infinity thin-walled shaft with tungsten.
Please realize that even an engine with two rotors 180 degrees apart will require some form of balancing as the front and rear parts of the engine will otherwise gyrate around the center.
At zero eccentricity we obviously need zero balancing. Now, when we increase the eccentricity by moving the rotor center outward, we only need to balance by moving a counter weight into the other direction of that fixed axis. If the e-shaft is a hollow, this could be simply achieved by making the opposite wall thicker. The highest counter balance we could achieve is by filling half of an infinity thin-walled shaft with tungsten.
Please realize that even an engine with two rotors 180 degrees apart will require some form of balancing as the front and rear parts of the engine will otherwise gyrate around the center.
In practical application, it actually becomes everything about it.
Well, I did read the book by Kenichi Yamamoto and they tried a lot but certainly didn't try everything. For example, manufacturing the chamber out of a steel sheet and pouring aluminium around it does work, but applying a thin layer of chrome decreases the wear so significantly, that omitting the electroplating step hardly makes any sense.
However, a $50 beaglebone black with a $20 ignition circuit can trigger a plug accurately every 250ns. Now, one of the features of the Wankel engine is that the rotor pushes the entire volume of gas past the plugs. Depending on temperature, throttle position and gradient, injector timing, etc. there will be an optimal sequence of firing each plug.
Mazda has made several hints that they are investigating laser ignition, to be able to target specific locations within the mixture to ignite, dynamically if needed. This will already be superior to any spark plug based ignition. The challenges are again practical in nature, as it's a harsh environment and consumers demand long life spans from components.
This isn't helping to clear the confusion on that point. You can already ignite an incredibly lean AFR, so lean in fact that your engine isn't producing much power at all. Do a search for a thread called "lean burn with negative split timing". Lots of lean burn testing that a member did. He didn't need different plugs or deliberately inconsistent AFR mixes to fire AFRs as lean as ...17:1?
09-06-2013, 09:28 AM
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