TeamRX8

iTrader: (25)

ah, my bad

rotarygod

I know what it is!

Renesis_8

whoa RG speaks. maybe i have a clue now too. haha. but chances r i m wrong =/
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Avandia Attorney

Japan8

I have a strong suspicion that I know too... a certain member has dropped several hints about development of it...

Senna

I wouldn't mind seeing a MS CX-7 but I don't want to see Mazda neglect us Rotary sufferers either!!!

rotarygod

I don't think so. I don't remember saying anything about who it was. Then again I also know who is helping Mazda develop direct injection in the rotary too!

lesper4

iTrader: (3)

great shot too bad i didint see ony of these people at SS, i needed this picture before the event

lazi

come on now! how did you miss all of us? lol

Red Devil

Just some thoughts, if and when a DI rotary is released, what do you see as the capability to put that in the current RX-8?

They'd both be drive by wire, but the fuel architecture and pump layout may be a real pain. Especially given the PCM control, or am I making this overly complex?

Tirminyl

Yeah, I would think fuel and pcm will be the big challenges so your definately not making anything complex. It is complex in itself.

patrick_andraste

Di Fuel Pressures are very high, and the fuel system has to be built around that in one way or another. the motorcycle people have a standard 45 psi fuel pressure to the DI Injectors, then at the injector assembly there is a high pressure system to raise fuel pressures even higher. I do not know the pressures, but I can find out if you like.

rotarygod

It wouldn't be an easy job. You'd need an entirely different engine, ecu, and fuel system. That's pretty complex. There are still some pretty big things to work out before we see one hit the road. I'll have to wrie up a tech article talking about DI and what I know about it. Not as much as I wish I did but I could write enough to get people brainstorming with how to potentially work around certain issues. Basically I know many of the things that have been tried in the rotary and what current problems are being faced. I'm not sure how to fix them yet but then again if anyone else did right now, we'd have one!

Red Devil

I don't know how Mazda does their fuel delivery, but I take it that VW and Pontiac for DI use a pump that uses the crankshaft to maintain effective pressure - from my understanding almost like a built in pressure regulator. Don't recall how high it was on either of those, though.

The other issue, at the moment, I've seen with DI applications is that there are no parts really available to up the psi of the fuel to add say more boost.

edit: Also looking into this, I've noticed like how BMW is running 10.5:1 compression @ 8.5psi on their 335 twin turbo. Or Mazda is at 9.5:1 on the MZR @ 13-14psi. Obviously, the cooling effects of DI are really advantageous for efficiency, and boost. What I've also read is that the mixture stays cooler before combustion due to the fuel not hitting the cylinder walls, whereas in port injection the fuel still "splashes and tumbles" into the cylinder and is heated as a result.

rotarygod

On the DISI 4 cylinder, Mazda runs somewhere around 1400 psi of fuel presure. I may be off a little bit but it's up there. By comparison standard cars run 38-43 psi or so. Give or take a few. When you think about it, what are chamber pressures like at different points in the combustion chamber? Pressure changes very dramatically. It had better. If it didn't, we wouldn't have any compression! The intake manifold or on the intake/exhaust side of the engine is low pressure. This is why even a few psi of pressure from a carb can get fuel into the engine. The farther the rotor moves after the intake ports, the more and more pressure build up. The farther around the top of the housings you move the injectors, in other words the closer you get them to the spark plugs, the greater chamber pressure gets. This means we need more fuel pressure to overcome it. That is the first hurdle. It sounds simple. Just raise the pressure an equal amount. It's not quite this simple though. Instead of writing this all out here, I'm just going to save it for a new tech article. I'll get into more detail there.

Mazmart

iTrader: (12)

1800 psi is what the DISI runs. Great seeing you and hanging with you again Fred.

Paul.

patrick_andraste

the direct injection thing has me perplexed though as to increasing horsepower.

I see it's advantages to increasing fuel efficiency and emissions, but on the racing motorcycles, we have gone the opposite direction from standard port injection and have gone to what is called a shower head. the fuel injector is actually about 1 cm before the velocity stack.

drawbacks are
cold start SUCKS.
poor idle
poor fuel economy at idle
best to use downdraft velocity stacks

advantages are more horsepower.
Lower fuel pressures throughout the system for more reliability.
better fuel atomization.
lower octane needs for high compression motors.

this is accomplished by using the fuel spray to cool the intake charge before it even goes through the throttle bodies.

there is a significant enough improvement in horsepower that the local Alfa Romeo guys are trying this tact. Their first attempt is to supplement the port injectors with shower heads that come into play at about 5k, or when the intake camshaft advances.

rotarygod

Fuel pressure has a huge role in atomization. Look at carbs at only a few psi of pressure. They are closer to water fountains than they are atomizers. DI raises the pressure to atomize better. Without this you need to vary the injector location to help it mix with air. At the same time you have to balance out distance. Look at new diesels. 20,000+ psi of fuel pressure and it does it over a very short amount of time. That is what we need for DI on gasoline. There's more to fuel mixture than just injector location. Where you put it, how you time it, and how much pressure you get all are important. DI tries to focus the fuel into one spot perfect for combustion so that there is as little waste as possible. we don't want spots where fuel can get to but not burn away. That's bad for emissions and it doesn't help power either. Without DI, we don't really have any control over where the fuel goes inside the combustion chamber. If we could focus it to use more of it, we should make more power. As is, when the spark leading spark plugs fire in a rotary, there is a richer concentration of fuel at the trailing side. That's why we fire the trailing later. We need to instigate flame front travel and then the trailing cleans up everything that was missed when the leading plug fired. Negative spark helps this but that is another topic altogether.

Renesis_8

"DI tries to focus the fuel into one spot perfect for combustion so that there is as little waste as possible. we don't want spots where fuel can get to but not burn away."

I am curious as to how the DI will work with 2 spark plugs in a rotary combustion chamber. Would a DI rotary incorporate only 1 spark plug? Since most of the fuel injected by DI should be burned right away near the spark. I cant wait to read your DI techie thread
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MEDICAL MARIJUANA

Mazmart

iTrader: (12)

This topic is one of the most interesting. There's so much to consider as to injector location, timing etc in the piston application. There are a lot of differences when this is applied to the rotary world. I'll make sure Fred is one of the first to know of what I find

Paul.

Spin9k

Here's an interesting application of DI, using ethanol to virtually suppress knock 100% during combustion in a gas engine with high psi FI, and high compression ratio, all the while increasing fuel economy by 20-30% and power up to 2x a standard engine. Could be something to learn here for a a rotary DI application.

http://www.autobloggreen.com/2006/11...efficient-eth/.