rotarygod

Being the crazy **** that I am, I am going to rig up a system for my RX-7 that lets me completely shut down 1 rotor when cruising on the freeway. Basically the rotary equivalent of displacement on demand. I know this isn't an RX-8 experiment but I feel that since the experiment is rotary based, you guys would find the info useful. My 1st gen GSL-SE RX-7 will be the experiment vehicle. Since I do alot of highway driving, it will be easy to see the benefits. When at freeway speeds I am going to flip a switch that completely shuts off the fuel injector to one rotor as well as disable spark to that rotor. Spark will shut off first. This will turn the rotor into nothing more than a free spinning air pump. This car will be easy since there is only 1 fuel injector per rotor. I just need to install 4 seperate ignition coils so I can disable 2 on demand. Before you guys start saying that the extra rotor is going to be bad parasitic drag on the other rotor, just know that it is very easy to turn the engine over by hand by just pulling on the belts. Try this with a piston engine!

The idea, should it work, is to make a system that shuts off one rotor when the engine is below a certain throttle load level such as cruising. When the pedal is pressed down farther than this level, the other rotor comes back online like nothing happened. It will be there for acceleration since this is where the most power is needed.

My only concern is with the oil injection system. Since the rotating surfaces need to have a constant supply of oil, I know that oil will still get in there but how well will it mix in with the air to lubricate? Also how will it get expelled out the exhaust port? I am thinking that since the amount of oil injected into the housings is so small, the amount left in the inside of the combustion chamber and exhaust pipe will be negligible. The only time this may be an issue is on really long trips with the cruise control on. Regardless I volunteer myself to be the first to try it in a car. I say in a car because this is already being done on some rotary engine based homebuilt airplanes. This is where the idea came from. Apparently my oil injection concerns are not bad enough to be harmful. It is reported that mileage in airplanes is noticably improved. My RX-7 already has the ability to get mid 20's for gas mileage. I'd like to do better.

If the idea has merit and I can prove it to be worthwhile for the car, I would like to see someone do the computer work necessary for the same thing to take place on the RX-8. To me this would be easier since all we have to do is program the ecu. This shouldn't be a problem for people like Canzoomer and others who can actually build these units.

Anyways that is the idea. If all of your driving is stop and go type of driving, this wouldn't benefit you. It is really aimed at freeway speeds. What do you guys think? If it works well, would there be interest? If the increase is noticable, the savings in gas alone would probably pay for the unit in less than a years time. From there on out it is only savings.

Looking for feedback. Keep it clean, and on topic. Basically, good idea or bad idea?

swoope

iTrader: (5)

wow,
its like the cadilac 8-6-4, but might work. my thoughts are if it works it would be easy to program the cut rotor to run for a couple of cycles every x amount of miles/time to burn out the oil before it fouls the plugs.

i have been out of aviation for a while. do you a rotory aviation link or two.

beers
john stewart

StealthTL

iTrader: (1)

Hmm, most interesting.........

rotarygod

Rotary aviation link huh? How about this obvious one!

http://www.rotaryaviation.com/

Here's a good one. Lots of good pictures and links for great rotary ideas. This one is almost too informative to be true.

http://home.earthlink.net/~rotaryeng/ACRE.html

swoope

iTrader: (5)

thx,

probably sorry i asked. am a working outside my field / a@p. and i live about 30 mile from lakeland.

and i have not gone for 4 years. go figure

beers
john stewart

PhineasFellOff

Hey, this is what i thought about in that thread i started.

zyran

If only they could do this in some V10s or something. I know some have this feature.

robertdot

This is a really great idea. I think it'd be really difficult on a piston engine (since the pistons balance themselves out... anyone who has had a vehicle that doesn't fire on all cylinders knows it gets a little shaky), but the rotary seems to lend itself to this kind of mod. I spend about 1/2 my daily driving on the highway (granted it is only about 30 minutes total). It'd be nice to see how much it improves mileage.

I'd like to see a piggy back unit that would control this on the '8. The only problem I can foresee is convincing people to test it.

It's not that you have great ideas that makes you essential to this community, but that you actually follow through with them when possible.

Luftwaffle

That would be awesome if you can pull it off. My questions are:

Why would you want to shut down the spark plugs first? If extra gas gets pumped into the chamber, and does not detonate from a spark, won't that make the next injection increase the gas in the chamber? Or will the unburnt fuel just be pushed out when it gets to the exhaust valve?

If you don't wanna burn that extra injected fuel, will that fuel/oil mix be enough to lubricate the rotor? Oil and fuel is injected into the chamber, detonated and some unburnt oil is used to lubricate the apex seals, right? (I could be totally wrong on this.) Will the fuel/oil mix not combine into some sort of nasty, coagulating gel? I imagine that the inside of rotor housing is coated with a lot of oil and some unburnt gas. Not detonating would make it coated with oil and a lot of unburnt gas. What affect would this have?

Wouldn't it be better to detonate all the fuel/air/oil, shut down the intake and exhaust valves, cut power to the spark plugs and then somehow inject a small amount of pure oil into the rotor?

Sorry for all the questions. I'm a n00b.

OdinGuru

Wouldn't this result in too few ignition events to integrate well? Granted the rotary output pulses are wider than the typical cylinder engine, but cutting out a rotor would result in the equivilent of a 2-cylinder 4-stroke engine. The Cadilac system makes perfect sense bc at worst it's a 4 cylinder. Seems to me like this would be very rough, but perhaps if it's only while cruising it doesn't matter. How much presedent is there for running on less then "4 cylinders" of output pulses?

robertdot

I drove a ~60 HP 3 cyl Geo Metro for the last 4 years. Granted it is a hell of a lot lighter than most vehicles on the road today, I could get it up to 85 if given a long enough space / conditions. Sure, it won't win any road races, but it got at least 45 MPG on highway (I drove from Birmingham to Daytona, FL and back for less than $40 a few summers ago, and could have gone from Birmingham to Louisville and back on close to one tank of gas if I hadn't gotten lost outside of Louisville). Once you get up to speed on the interstate, you don't need much to keep you at that speed. RG's idea, it seems, would be to kill the extra rotor after getting up to highway speed, and operate on the single rotor to keep it at highway speeds. I think it would work pretty well. And, if it doesn't (if you found a big hill that needed more pull), turn the other rotor back on. No biggy. (If this was the question you were even asking...)

The work (what I guess would be a relativley small amount) involved would be worth it (at least as far as RG is concerned since he doesn't have to mess with ECU stuff) if it could get him to 40 MPG on the highway.

I wish I lived in Texas. This would be a fun project to help with / watch develop.

TheDosDog

I think there will be too many issues with a dead rotor. First, with out a compression release you'll be adding more drag than the other rotor can overcome and still provide the gains you desire. Then there are the effects of "pumping" clean air into the exhaust system. Even 1984 emmissions equipment may have a difficult time dealing with it. In addition rich exhaust from the other rotor may ignite when it encounters the clean air. Then there will be a lubrication issue. Oil wil continue to be injected at the apex and not combusted. Will this lead to fouled plugs when the rotor is reenabled? This seems like a great idea but I think there is a lot more engineering involved to make it work.'

PaulieWalnuts

Good idea. I'm interested to see what you come up with. A GSL-SE? Don't you have a junker FC laying around?

mysql101

How about we change the idea around slightly.

Rather than have one roter spining and burning, make the switch alternate between the roters.

So roterA will spark and inject one cycle, roterB does it the next. That will prevent build up and excess wear on any one roter.

rotarygod

Paulie: I had 2 RX-7's. The GSL-SE still exists. My FC went to that great junkyard in the sky. Parts of it live on though and the streetported turbo engine is still sitting on a stand.

The only reason that I want to cut fuel first is because I'd rather have the chamber go rich for a second rather than lean and detonate. I'm not scared of detonation on a nonturbo vehicle, but this just seems a little safer. I'm not talking about a few seconds difference. I just want spark to cut out a fraction of a second later. Once everything is cut off to the chamber, no fuel and no spark equals no detonation. You have to have an air/fuel ratio and not just air to get detonation. The small amount of unburned fuel would just go out the exhaust. Bad idea, maybe but this is still an experiment. Ideas change as you learn. If I can cut everything out at the same time and have it work good, then I'll just do it that way. This is the easiest way. Understand that as an experiment on a 20 year old car, I will physically have to flip a couple of toggle switches while I am driving just to test the idea. Very low tech experiment but if it works it will have high tech results.

One rotor engines exist in homebuilt aircraft and other things. Atkins rotary has a 1 rotor riding lawnmower. They still run just fine. The other spinning rotor would still balance the assembly out. The biggest difference you would notice when the rotor cuts out is that the engine tone changes. A 1 rotor engine sounds totally different than a 2 rotor. I actually don't like the way they sound but this is about mileage not tone.

I don't foresee any issues with just letting one rotor free spin and working as a giant air pump. Sure it will be sending air into the exhaust. If anything this will help burn any unburned gasses by adding more oxygen. This is what the airpump does. It does nothing more than add air into the exhaust to help burn any remaining gasses and clean up emissions. I think if anything the engine will burn cleaner this way.

I'm also not too concerned about the additional drag of the nonrunning rotor. I do not expect to get 50% better economy because one rotor is running. I know there will be a little loss from the extra drag. The goal is a 30% gain in mileage on the freeway. A gain is a gain. The rotary is a very easy engine to turn over. I see this idea working much better on the rotary than on piston engines which is where it has and is still being tried. Go outside and put your car in neutral. Reach into the engine bay and grab the main pulley itself. This is where you physically have the least leverage since you are grabbing close to the rotational centerline. Turn the engine over by hand. You can do it. It isn't that hard. Now imagine having to turn over just a little more than half that much. I say more because you are turning all of the engine acessories. This isn't very difficult and shouldn't present much of a load on the remaining rotor. Most of the power is used to get the car moving, not to keep it moving. At cruising speeds when one rotor shuts down, you'd have to increase fuel to the remaining rotor just a little bit but it wouldn't be near the amount that would be needed to keep the other rotor going.

My only concern is with the oil metering system. Since this same principal is being used on certain rotary based aircraft, I'm not too concerned. Those guys don't take any chances. They go up in the air with redundant systems. If I were 10000 feet off of the ground, I wouldn't do anything to my engine that might be fatal. Altitude changes the rules a bit. These guys are still doing it which makes me believe that we can too. If fuel is needed for it to mix then we could program the rotor to come back online for a few rotations every once in a while. Since this rotor isn't doing any work, just freespinning, it has different loads and therefore different lubrication requirements. They are less. We still want lubrication to them though but it shouldn't be alot. This is why I believe the aircraft people make it work.

As I said, I do have some concerns but this is just an experiment. This is how we learn. If it doesn't work then I'm the only one to have wasted the time and effort. If it does work you'll love me! If I hurt my engine, big deal. As I stated at the beginning, I still have my streetported, turbo engine from my 2nd gen RX-7 sitting on a stand waiting for a new home. This is why I'd rather try it on a 20 year old car rather than a new one. I'll learn the answer to these issues soon enough. I need to get a compression tester to check compression before I cut off one rotor. This way if I am having lubrication issues with this rotor it might show up in the form of lost compression. Anyone have a better idea? I also will be watching the condition of the spark plugs to look for fouling. I am thinking about cutting out the rear rotor. This one typically runs hotter than the front due to the location and the fact that water flows through the engine from the front. I'd like to give this rotor a rest. We'll see. Maybe it will work, maybe it won't. The idea is good though. I just hope it is as good in practice.

rotarygod

Since I am doing this with toggle switches on the dash, this would be very difficult. I'll have to let someone else try that. If there is concern about uneven wear between rotors then the ecu could be programmed to shut either one off at it's convenience. Sometimes the front shuts off, sometimes the rear shuts off. With ecu control, any form of programming is possible.

Atacdad

My two cents worth would be to see if you could find an old, almost shot rotary to put on a stand (not your good FC one). If you're old car is still in good shape, it'd be a shame to blow it up. Of course, if the old car is not much more than an engine stand for a nearly worn out old rotary, then bring on the explosions!

TheDosDog

The way it was explained to me, a rotary engines compression is different than a piston engine. When the engine is off, air can seep past the apex seals and the motor is relatively easy to turn over. However when the oil is injected at the apex the compression increases. This is part of the reason a rotary takes longer to fire on startup than a piston motor.

robertdot

It looks like it is in good shape (assuming the fire is behind it, and not in it ).

rotarygod

lol!!! Yep the fire is behind it.

The car itself is in good shape but the engine in that car is a streetported 6 port engine that I built. It is literally the original engine opened up, ported, and then put back together. It still has all the original seals. I was lazy and had other options should it fail. The streetport turbo engine is on the stand waiting for a home. My best friend also has 2 Turbo II RX-7 engines sitting on the floor in his garage so I don't have a shortage of engines if something happens.

There isn't much oil injected into the engine by the metering system so I don't think the small amount will cause any compression issues. You need to add a good amount to get to that point. The engine will still compress the air regardless but it just kicks it back out. Like I said, you can turn the engine over by hand. This isn't that much of a load issue.

If the idea works I am going to toy with the idea of having the one rotor off any time the engine is under 20% throttle. In other words it would idle on 1 rotor too. I would let the engine start and get warmed up with both rotors though. I am thinking that we'd benefit from better idle fuel consumption as well. This is all just speculative right now and may not work at all. It's a fun idea though.

PaulieWalnuts

rotarygod, do you have an idea of how long a rotor will run without oil injection before seal or compression failure happens? I mean under normal conditions like as if the oil injection system fails and the car is driven normally.

binnung

RG I live in Spring, Tx and have enjoyed many of your post. I see only one problem with your idea. Though you can move the engine by hand the combined compression cycles of the rotor that is turned off will put a load on the engine. Just a thought.

rotarygod

I know it will put some load on the other rotor which is why I don't expect a 50% increase in economy. I know it will take a little more fuel to keep the other rotor providing enough power to keep the car moving. I am hoping though that the extra amount needed for that one rotor is less than the amount that would have been needed to keep the other rotor running.

Since I am not disabling the oil injection system, the rotors will still get lubrication. Also, since the rotor is not under any load, the amount of lubrication needed is decreased which helps us a little. The stock metering system (computer controlled cars, not mechanical like my RX-7) injects oil into the engine based not only on rpm but also load. Most of the oil injected into the engine is during accleration and hard driving. Even then, how much oil do you have to add every 1000 miles? Not much. I am thinking that the small amount that still does enter this rotor will not have any negative effects. It will still lubricate but shouldn't be so much as to leave deposits. If I use a seperate reservoir for the oil metering system that uses 2 cycle oil, it definitely won't leave deposits.

Like I said all of this is just speculative on my part and you guys are expressing valid concerns which I also have thought about. It is being done on rotary aircraft though and this leads me to believe that it isn't an issue. These guys don't want to risk their lives when they are up at altitude. They are some very creative people. They treat a 2 rotor engine as 2-1rotor engines. Each rotor is computer controlled independently of the other to adjust for variations during each rotors combustion. They also run redundant systems in the event of failure. The way I see it, if you are going to copy someone elses ideas, copy the most **** and careful people you can. If it still doesn't work the way I hope it will, then at least we learned something. This is just for fun until it works. If it does, it becomes a serious project. I do like the comments and concerns though.

buzzwordenabled

The mixture of air and fuel helps cool the rotor. Simply disabling the supply to one rotor will likely cause some cooling issues with the "idled" rotor. Alternating between the rotors might be more workable, but the resulting power delivery might not be particularly "fun".

T-von

The way I invision this alternating set-up working is every other rev and "NOT" having either front of rear completely shut off. The ecu could easily alternate the spark and fuel pulses for every other rev of the engine to make this work effectively. This way both front and rear are running just at half duty. This would keep both chambers equally warm and lubricated.


Wait a sec......can fuel injectors pulse like this?