So, you want to build your own engine...
Some food for thought...
A new 350ci/260HP Engine is $1500 here: Chevrolet Performance 10067353 GM Goodwrench 350ci/260HP Engine & Packages A new RENESIS engine is $6000 and I believe that for that amount of money even a small group of twenty buyers can have a s***load of parts made for a dozen engines - each. Car manufacturers do not have the objective to build disposable engines that have to be replaced after a few 100 hours of operation, however the advantage of Wankel engines is that they are simple and should in principle be dirt cheap to make, especially if they haven't been designed to last as long as piston engines. Operating cost at $4/gallon of gas and 20MPG is $0.20 per mile, so an engine core that lasts 10000 miles and costs $500 adds only $0.05 per mile driven. Suggested reading: foxed.ca/rx7manual/manuals/REbyKenichiYamamoto-1971.pdf foxed.ca/rx7manual/manuals/REbyKenichiYamamoto-1981.pdf Dear mods: Maybe we could have a separate section discussing everything Wankel engines. I know there are (many) other places, but I suppose most people who own a car with a Wankel engine will own an RX-8. Flame away! :) |
no flaming permitted here, but many may disagree. The new price you quoted is misleading as there are no 'new' Renesis engines left. Remans have a list price of $2,001.
I believe that the cost of making your own internals is going to be far higher than you think. Tooling costs... Posted From RX8Club.com Android App |
I'm not sure I understand the point of this post? You are suggesting we get together and make our own internals?
We should put cheap Chevy engines in our cars? I am not trying to flame you, I'm just not entirely sure what you are getting at... |
This isn't a project for a new owner. So, I'm moving it to the appropriate forum.
The Chevy engine may be cheaper, but the total cost will end up being much more. Plus, you will be without the use of the car for a couple of months. |
Al, I think he is talking about building rotary engines, not the Chevy engine.
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I guess his intentions are unclear.
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I can agree with that.
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Originally Posted by RIWWP
(Post 4520048)
I believe that the cost of making your own internals is going to be far higher than you think. Tooling costs...
Peripheral porting allows very large ratios of bore to stoke with wide housings and rotors. The chamber could be made from elastic sheet metal with frames spaced every 15mm or so. Cooling would necessarily be circumferential, which has the benefit that we can directly pass coolant from hotter to colder areas. The wider the rotor, the less important is sealing the sides and corners. In theory, mechanical pressure (e.g. with bolts) to certain points of the frames should make the spring steel sheet behave like a cubic surface spline. The error of a cubic spline is smaller than 5/384 * h^4 * f'''' and an epitrochoid with moderately low eccentricity is already very smooth (f'''' is small). For illustration: squashing an elastic at two equidistant points, i.e. opposite sides, already gives us a figure-8 and the error decreases 16-fold when we double the number of points), so an 8-point spline gives us 1/256th of this (already low) error. The rotor could be constructed using similar techniques, the framing could be offset, forming a screw which moves oil through the core, possibly replacing the oil pump. The e-shaft could be constructed from two pipes with 6 bearings (two for the rotor, two for the shaft itself and two to keep the sides of the combustion chamber in place) . For balancing, the inner pipe could be weighted on the inside, opposite the rotor. P.S. In case my intentions were unclear clear: if we can get a 500lbs engine with block, crankshaft, 8 pistons, 8 connecting rods, 12 bearings, 2 cams, 16 valves, carburetors, etc. for $1500, then we should be able to get a 200lbs rotary engine with 1 rotor, 1 housing and 1 eccentric shaft for much less than that. |
I don't think I can adequately convey the number of problems I see with your idea.
Strength of materials, heat cycling, Mazda's proven results with various aspects of various iterations, the width of the Renesis rotors/housings already being too wide, peripheral ports can't meet emission requirements, lubrication needs still exist, etc... Math is great, but real world results shouldn't be discarded. Don't forget the thermal dynamics, chemistry, etc... of the rest of what happens with multiple fluids, temperatures of condensation and boiling, heat saturation, flame fronts, heat cycling, etc... |
Originally Posted by SIPSOIL
(Post 4520159)
P.S. In case my intentions were unclear clear: if we can get a 500lbs engine with block, crankshaft, 8 pistons, 8 connecting rods, 12 bearings, 2 cams, 16 valves, carburetors, etc. for $1500, then we should be able to get a 200lbs rotary engine with 1 rotor, 1 housing and 1 eccentric shaft for much less than that.
If you don't understand that, I suggest opening up an introductory to economics text book. |
Originally Posted by Carbon8
(Post 4520167)
Supply and demand, you can't compare the price of a GM V8 to a rotary engine no matter how hard you want to.
If you don't understand that, I suggest opening up an introductory to economics text book. If you don't understand that marginal unit production costs do not equal retail prices, I suggest you work on your functional literacy. If the goal is to make your own engine (hint: thread title!), would you attempt to make a single rotor Wankel engine or a V8? P.S. If one wants to have a couple thousand units made to spec, alibaba.com and kickstarter.com are your friends. |
Originally Posted by SIPSOIL
(Post 4520159)
P.S. In case my intentions were unclear clear: if we can get a 500lbs engine with block, crankshaft, 8 pistons, 8 connecting rods, 12 bearings, 2 cams, 16 valves, carburetors, etc. for $1500, then we should be able to get a 200lbs rotary engine with 1 rotor, 1 housing and 1 eccentric shaft for much less than that.
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Originally Posted by RIWWP
(Post 4520162)
I don't think I can adequately convey the number of problems I see with your idea.
Originally Posted by RIWWP
(Post 4520162)
Strength of materials, heat cycling, Mazda's proven results with various aspects of various iterations, the width of the Renesis rotors/housings already being too wide, peripheral ports can't meet emission requirements, lubrication needs still exist, etc...
Originally Posted by RIWWP
(Post 4520162)
Don't forget the thermal dynamics, chemistry, etc... of the rest of what happens with multiple fluids, temperatures of condensation and boiling, heat saturation, flame fronts, heat cycling, etc...
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Originally Posted by SIPSOIL
(Post 4520212)
difficult =/= impossible
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He's not getting it, subbed for the amusement I guess.
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I think it's more that he just finds the challenges trival.
I wish him the best. Maybe he will make it onto Mazda's rotor development team and we will have figure 8s instead of doritoes. |
Originally Posted by bladeiai
(Post 4520203)
You do know we have 2 rotors right? Also do you have any idea what it cost to R/D an engine? Especially a rotary engine? Carbon is right about the economics involved, you are comparing apples to snozberries.
However, I did spend a day researching papers on epitrochoids. It appears that even this very limited amount of knowledge makes me the expert among the three of us. So far the total cost is $0 + the cost of figuring out who's going to be on my ignore list, which is approximately 30 seconds/ignoranus. |
Sorry if our skepticism shows a bit when you talk about making a rotary out of sheet metal. :)
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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 |
Since when does theoretical knowledge ever directly transpire to real word results :dunno:
Spout your derived theory all you want, without the real world results its just banter Under derived theory the rotary engine was perfect 40+ years ago, thats been proven to be quite false to todays standards. Apparently your 1 day research unearthed some knowledge that eluded Mazda's top engineer's for over 40 years |
Originally Posted by SIPSOIL
(Post 4520221)
I have no idea, I have never R/D'd an engine before. But neither have you or Carbon8.
However, I did spend a day researching papers on epitrochoids. It appears that even this very limited amount of knowledge makes me the expert among the three of us. So far the total cost is $0 + the cost of figuring out who's going to be on my ignore list, which is approximately 30 seconds/ignoranus. 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. In your self-discovery of the incredible genius that is you, did you ever stop to ask "did anyone ever consider my stupid idea before me?". The perception of genius without humility is worthless. |
Originally Posted by Carbon8
(Post 4520232)
Since when does theoretical knowledge ever directly transpire to real word results :dunno:
Spout your derived theory all you want, without the real world results its just banter Under derived theory the rotary engine was perfect 40+ years ago, thats been proven to be quite false to todays standards. Apparently your 1 day research unearthed some knowledge that eluded Mazda's top engineer's for over 40 years Mazda's top engineers have put in a lot of effort over the last 40 years, yet no Mazda Wankel is currently in production. Do you think the engineers are incompetent? Do you think they enjoyed wasting their time? Or do you think that Mazda management might have demanded that they solve the wrong problem? I think they might as well have told them to make a large gasoline engine to compete with a marine diesel. So, instead of wasting a lot of resources on marginal improvements to the shortcomings of Wankel engines, let's look at what we can do to improve the strengths of Wankel engines. 1. Wankel engines are less complicated than reciprocation engines. This makes them cheaper to manufacture. 2. Awesome power to weight ratio. However, a fully tuned ZX-14 engine generates 200rwhp and weighs 50lbs less than the RENESIS engine and a Mazda reman engine costs $500 more than a brand new V8. I think it's possible to easily beat both of those, if we cheat a bit and declare E85 to be standard "pump gas" and design the engine to run on 115 octane. So, the real questions are: 1. Can we make a Wankel that we can carry a spare in the trunk or even the engine bay? 2. Can we design so that we can swap in the spare in the same time it takes to change a tire? 3. Can we design to make rebuilding the spare cheap in parts and labor? |
The real question is, why run a rotary when there are butt loads of Isuzu Rodeo V-6's out there?
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You sir should have stopped while you where ahead, I can't seriously construct a retort to what I hope is a sarcastic response.
Starting to think we are getting trolled :suspect: Nobody can be this dense. |
Originally Posted by SIPSOIL
(Post 4520255)
Mazda's top engineers have put in a lot of effort over the last 40 years, yet no Mazda Wankel is currently in production. Do you think the engineers are incompetent? Do you think they enjoyed wasting their time?
Or do you think that Mazda management might have demanded that they solve the wrong problem? The latest interation is also only the ... 8th? production iteration of the wankle. Hardly a huge backbone of development to lean on. It's a pretty tiny team in a very small manufacturer that has collectively done all the work. It didn't help that Ford was largely running Mazda during the R+D of the wankle.
Originally Posted by SIPSOIL
(Post 4520255)
1. Wankel engines are less complicated than reciprocation engines. This makes them cheaper to manufacture.
2. Awesome power to weight ratio. However, a fully tuned ZX-14 engine generates 200rwhp and weighs 50lbs less than the RENESIS engine and a Mazda reman engine costs $500 more than a brand new V8. 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.
Originally Posted by SIPSOIL
(Post 4520255)
1. Can we make a Wankel that we can carry a spare in the trunk or even the engine bay?
2. Can we design so that we can swap in the spare in the same time it takes to change a tire? 3. Can we design to make rebuilding the spare cheap in parts and labor? 2) Yes, but the cost to do so is significant. The Freedom Autosport Grand-Am team has their 2.0L engines installed and prepped in such a way as to be able to do an engine replacement in about an hour. It sure isn't cheap to do. 3) You have mentioned a "10,000 mile engine" before. You can get that for around $200-$300 now with the Renesis. Pull it apart, replace some seals, put it back together, and you can expect it to last 10,000 miles at most. I don't see what you are gaining? |
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