More Engine Theory
 

For some time I've been surfing around the net, looking for modern engine design theories and practices-- Just for random fun.

Recently I came across a really interesting area of engine research: Making use of solenoids to open and close exhaust/intake valves instead of (what I consider) primitive, old-ass cam shafts. I'd hope that a reliable way of using this technology comes to play soon, as I figure this allows for substantial simplification of an engine-- Fewer moving parts/belts/chains, etc. which would otherwise be needed to spin cam shafts. Also, under computer control, it would be a lot easier to control valve timing to optimize fuel/power efficiency. Cam shafts can only go so far, and I think we should bag that lame-ass technology in favor of something that is infinately variable; not limited.

Anyway, a point of curiosity on my part. I've thought the idea is pretty cool, and am actually surprised it wasn't thought of earlier. Wonder why the hell no one is building engines like this yet. ??? :wtf:

Active valve actuation without cams I believe is already being done in F1. I thought I read that BMW will also be using a similar feature on some upcoming car.

Ah, Yes!
 

Indeed, I had forgotten about rotaries. Although in theory I understand that they have fewer moving parts and should be more robust, I thought I heard that one of the reasons Mazda discontinued the rotary in previous generation cars was because of reliability issues. I could be wrong about that, but I thought that's what I heard (along with rotaries being less fuel efficient).

In any event, getting rid of cam shafts makes a lot of sense, and I guess maybe that kind of technology is, well and true, starting to come out in production engines...

Yeah, baby! :D

The rotary engine, in stock form, was very reliable. However, people who don't know much about them tried to increase their power like a regular piston engine. The stock internals of a rotary can handle many times more power than they are tuned stock. Add slightly more robust internals and these little 1.2L and 1.3L engines could easily handle over 1,000hp.

The problem people have with them is overheating. Since a rotary is all aluminium with carbon-graphite apex seals, they are very sensitive to overheating. A rotary engine burns much, much hotter than a piston engine. The fuel-air mixture is still expanding when it leaves the exhaust ports. There is no cooling stroke for the spark plugs... they are constantly firing. There is no way to get coolant to the rotors or eccentric shaft (rotary equivalent of crankshaft)... they must be cooled by oil, and only from the inside of the rotors. The rotor makes 3 full revolutions to make one eccentric shaft revolution. Add in a turbo (13B-RET) or the sequential twin-turbos (13B-REW), and you have one hot running engine. Throw in some really aggressive tuning and boom! You have one overheated engine. You must always concentrate on cooling with rotaries. This is why so many people have blown the twin-turbo engines... they just turn up the boost with stock cooling.

As for solenoid-actuated valves... they have been in research for many, many years. I believe they have found some use in industrial engines and diesel engines. The problem with them is actuation speed. They can't handle really high rpm. It's a promising technology, but it still requires a lot more research!

Ford had nothing to do with Mazda not importing the RX-7 to the states...IT was the almighty dollar...the car became so expensive,they just couldnt sell enough of them to justify bringing them here...R.I.P. Rx-7..'sniff:(

Hmmm... Every single 3rd Gen I've seen towed into the dealership was modified... typically with a piggy-back system or ECU rechip to raise boost levels. The other 3rd Gens I saw were in for scheduled maintenance or minor repairs.

But, there are plenty of people out there who swear the rotary engine is a POS and anyone who buys one is an idiot. For those of us who have actually owned one... we think totally differently. I had less problems with my 20 year-old RX-7 than I've had with my '99 Protege.

Re: More Engine Theory
 

Ducati Desmo system. http://www.ducati.com/bikes/techcafe...hnical&artID=2

Been done for some time now. Quite slick.

Don

funny how when i go to the Mazda Dealers and look at the employee parking, 90% of the Techs have RX7s, older and newer, go figure

i guess you have to know what you're doing to own a rotary engine, morons need not apply, thats why i dont have one.

My brother has a 3rd gen RX-7, and from hearing him talk, his biggest problem is finding a qualified mechanic to work on the damn things. So much so that he finally said screw it and got his hands dirty. His car runs much better now that he's in control.

Probably a lot of people are suffering from getting their cars done by people who *think* they know what they're doing.

Well, it depends what you call a "maintenance nightmare." If checking and adding oil once a week and letting the engine warm up before driving it is a "maintenance nightmare", then a rotary engine is not for you.

Those are the two biggest things people do (in terms of maintenance) that destroy these engines. Rotaries inject oil into the rotor housings. Rotaries use metal (carbon-graphite) apex and side seals, which are spring-loaded and constantly rub against the rotor housings and side housings. The only way to lubricate them is to inject small amounts of oil into the rotor housing. This means that you must check the oil level frequently and add oil when needed, since the oil metering pump pulls directly from the engine's oil pan. It also means you must change the oil frequently (3,000 miles) to ensure only clean oil is getting into the engine. You must also use dino-oil and not synthetic. Dino-oil burns totally away, where synthetic will leave a film which will keep building and you'll lose compression.

Rotaries do not like to run cold... at all! Not letting them warm up to operating temperature means incomplete combustion of the fuel and incomplete burning of the oil which will lead to heavy carbon deposits and clogged monolithic, primary catalytic, and secondary catalytic converters.

Personally, I do all of the above with any car I own... so a rotary's maintenance is not any different for me than a piston engine. However, there are so many people out there who never check their oil and never let their car warm up... and they destroy rotary engines and then tell everyone they know that Mazda's suck and rotaries are stupid.

I know plenty of people from the local RX-7 club with 3rd Gens with over 100,000 trouble-free miles on them... And 1st and 2nd Gens with well over 200,000 trouble-free miles. And when the RX-8 hits the market in 6 months, I'll be jumping on it! There's nothing like driving a rotary!

No one has mentioned rotary valve technology. It's way more efficient than poppet valves (what we have now) and does away with the whole valvetrain. The only thing that remains is a 'camshaft' of sorts in the cylinder head that spins. I read a big article on the man that designed the a system a couple years ago. He even built a factory to produce the cylinder heads for current GM, Ford and Chrysler. He was getting 1/3 more power out of all the engines that he built while maintaining low emissions, smooth idle and factory driveability. Last I heard he was going to build some stuff for a European car company but the big 3 didn't want to pay for his technology even though he had demonstrated well over 100,000 mile durability without a 'valve' job.