4-Rotor FC Build
11-02-11, 05:04 PM
#51
IFO Forced Induction Slo
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Great build. Hopefully one day 4 rotors that dont cost an arm, leg, and wife are readily available to the general RX-7 population.
A++
Also, great work on the exhaust inserts. That is the perfect design for exhaust velocity.
A++
Also, great work on the exhaust inserts. That is the perfect design for exhaust velocity.
11-02-11, 06:08 PM
#52
even $8-10k at the cheapest is unachievable by most people and it will never get any cheaper than that.
so about $20k to get it to make some noise, still not going to see too many of them around even though you can't get anything comparable still for that price.
so about $20k to get it to make some noise, still not going to see too many of them around even though you can't get anything comparable still for that price.
11-02-11, 11:13 PM
#53
http://www.pulseperformance.co.nz/in...p?page=product
11-03-11, 07:01 AM
#54
I don't think these engines will ever be suited for the average rotary enthousiast, because no matter how you do it, there is a serious amount of manhours involved which makes it expensive. I've kept track of the cost of the e-shaft i'm making. Should be a 3 digit number when it's done. Add in manhours though and the shaft becomes too expensive for pretty much anyone. Even without having to pay manhours this engine is going to cost me plenty, since there are things you just have to buy such as fuel injection compoments and engine seals.
11-03-11, 12:08 PM
#56
I don't think these engines will ever be suited for the average rotary enthousiast, because no matter how you do it, there is a serious amount of manhours involved which makes it expensive. I've kept track of the cost of the e-shaft i'm making. Should be a 3 digit number when it's done. Add in manhours though and the shaft becomes too expensive for pretty much anyone. Even without having to pay manhours this engine is going to cost me plenty, since there are things you just have to buy such as fuel injection compoments and engine seals.
even fabricating a brand new shaft wouldn't be too costly, mazda actually is almost more than reasonable with the price of each new e-shaft. then again they have a machine setup for each stage and they likely can crank one out in about an hour's time. for most smaller shops having to set up for each phase is a time consuming gruelling process measuring angles, depths, making jigs, adjusting the mills/lathes, etc, etc, etc.
Last edited by RotaryEvolution; 11-03-11 at 12:13 PM.
11-03-11, 01:12 PM
#57
Gold Wheels FTW
The only way to make them more mainstream / cost effective for the masses, is to cough up the money for forging dies. Forge them to 95%+ complete, then clean and bore the oil channels. It would take a while to recoup the cost of the die, but you could probably sell 4 rotor shafts for $1500 easily.
I think the biggest expense would be the thick center irons. Just the aluminum alone for one would be around $500 or so (last time I checked). Not much of a way to make the center iron besides cast or billet.
Figure a cost of around $2000 for a one off center iron, that's $4000 alone for a 4 rotor.
so yea, we're already up to pretty close to 6000, and we haven't gotten into the stat gears, but these could be forged to like 95%+ too. They're really good with cogs.
I planned to build one one day too, but it will definitely take a lot of planning. The only thing that slowed down my pursuit of the forged shafts was getting someone reliable to do the CAD work and not be over charged for it. I already had a local forge lined up to review the designs and prototype it.
I think the biggest expense would be the thick center irons. Just the aluminum alone for one would be around $500 or so (last time I checked). Not much of a way to make the center iron besides cast or billet.
Figure a cost of around $2000 for a one off center iron, that's $4000 alone for a 4 rotor.
so yea, we're already up to pretty close to 6000, and we haven't gotten into the stat gears, but these could be forged to like 95%+ too. They're really good with cogs.
I planned to build one one day too, but it will definitely take a lot of planning. The only thing that slowed down my pursuit of the forged shafts was getting someone reliable to do the CAD work and not be over charged for it. I already had a local forge lined up to review the designs and prototype it.
11-03-11, 01:16 PM
#58
mazda is the only one with the tooling already in place to mass produce them but still would require a whole new set of machines for the 4 rotors. i'm quite sure even their race 4 rotors were all hand made with only a few of the production assemblies used.
even at $1500 they may sell at most a few a month, not nearly enough of a market for it to even recoup investment.
even at $1500 they may sell at most a few a month, not nearly enough of a market for it to even recoup investment.
11-03-11, 03:41 PM
#62
Gold Wheels FTW
mazda is the only one with the tooling already in place to mass produce them but still would require a whole new set of machines for the 4 rotors. i'm quite sure even their race 4 rotors were all hand made with only a few of the production assemblies used.
even at $1500 they may sell at most a few a month, not nearly enough of a market for it to even recoup investment.
even at $1500 they may sell at most a few a month, not nearly enough of a market for it to even recoup investment.
You'd probably have to sell 20~30 shafts to break even on the forging die, but if your goal is proliferation and long term small profits, then it could be done. I'm much more interested in proliferation than trying to retire on overpriced products. You have to make money, sure, but to charge someone more than $5000 on a single shaft is ludicrous.
I don't think you'd need a lot of specialty machines. Most forges will offer finial "cleaning" of parts for a pretty small fee comparably, but at most, you would need a pretty deep boring mill to make a factory like oil supply, be able to bore out the oiling jets, and then just a cnc lathe to mill the finial few microns of material away from forging. could probably stamp out, and finial machine a shaft in a couple hours, and be more or less automated with a good forging / manufacturing company. You'd probably want to do runs of like 10 or more at a time to be cost effective too though. It would be a very long term investment for sure, but I have other ideas for it other than just older RX7 / 13b support.
I think ideally, you would want a CNC lathe, and a long boring mill, and a shaft balancer in house, and have the rough cast forgings done and delivered in small bulk runs, then machine and ship as ordered / sold. I don't think Billet is the way to approach it. Too much labor involved for mas production, but good for a prototype or one off anyway.
I still hope to get some quotes on some forging dies one day. I just have to get a complete CAD drawing of a 3 and or 4 rotor shaft before I can go any further. My 3D modeling skills are poor at best... lol. I'm more a programmer than a modeler. I've been screwed by 2 modelers in the past. One even stole my reference parts. So needless to say, I've had issues with reliability.
The housing and rotor are far more complex than the shaft.
11-03-11, 04:32 PM
#64
IFO Forced Induction Slo
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Yeah you guys are right...I'd still want one though. Hopefully one day either the price will go down or my disposable income will go up. 
Great job anyway though.
Great job anyway though.
11-04-11, 05:25 PM
#68
Did some more work, modified some oilholes and added some new ones.
I'll get the shaft ready for annealing tomorrow, still have a few small things to do.
Here's a picture of the shaft now, this also clearly shows why I work with metal for a living instead of wood
Also got some fuel injection stuff today, injector dynamic ID1000's and a bosch 044 fuel pump. I've been thinking about injector placement a lot lately, and in particular semi-direct injection like the new 16X engine has. I think it can be done, the conditions in this area aren't that bad, the maximum pressure here is around 3 bars, but the average pressure is much lower. There aren't any combustion pressures or temperatures, so the fuel injectors should have no problem injecting fuel here, it's really a total different story from direct injection gasoline GDI engines that have to operate at insane amounts of pressures.
I think the long port overlap of the PP engine lets some incoming mixture and therefore fuel escape through the exhaust. This would be avoided by placing the injector further upstream. The downside is that there's less time for the fuel to mix properly with the air. I don't know how important this factor is though. Anyway the ID1000's should have a good spray pattern which helps, and I should be able to set it to a decent fuel pressure with the bosch 044 pump. I may need to use a sequential injection setup because of the fluctuating pressure in this area. Me and some friends of mine have our own chassis dyno
, so I'm able to do some dyno time and test the difference in power output and fuel consumption.This is what it would look like:
More interesting, a youtube clip of the rotating assembly, look at the point where the exhaust port closes, and the point where the injector is at.
The only reason I'm doubting to go ahead and try it is that I haven't seen others do this. If it has benefits it would have probably been done already, I'm sure mazda thought about it back in the day when they were designing the 787B, and I'm sure other rotary enthousiasts have thought about the idea aswell, so why hasn't anyone tried it? It can't be a horrible idea because the 16X engine has it. Maybe it's good for economy but not optimal for power, or maybe it has something to do with the quality of fuel injectors which has gotten a lot better over the last 20 years.
Youtube vid:
http://www.youtube.com/watch?v=tBqp83qzCOw
Last edited by John Huijben; 11-04-11 at 05:28 PM.
11-04-11, 05:31 PM
#69
most people have poor results because the injector timing has to be spot on, compared to mixing with the air before entering the engine. technically you can phase injector timing to whatever you want outside the running engine, once inside if it isn't injected right at the perfect time, results turn to crap.
11-05-11, 05:00 AM
#71
most people have poor results because the injector timing has to be spot on, compared to mixing with the air before entering the engine. technically you can phase injector timing to whatever you want outside the running engine, once inside if it isn't injected right at the perfect time, results turn to crap.
11-05-11, 04:17 PM
#74
Makes sense, I guess I could try using the injector bungs I already have, which are in the peripheral port sleeves, and setting up a sequential injection system where the injectors open when the exhaust port closes. It would probably be a small difference to normal non-sequential injection but it's something I can test without any difficult mechanical modifications.
11-06-11, 11:30 AM
#75
IFO Forced Induction Slo
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it's an option, you can always cap off the ports in the housings and move them to the PP runners if the results don't wind up being what you expect. better to attempt it while the engine is apart than to try to attempt it later. but this is a big undertaking in one step, i'd at least get the 4 rotor running and see if it itself has any issues that develop first. perhaps make the inserts for both in the rotor housings and in the PP runners but start with the injectors located in the runners first.