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-   -   Direct Injected Rotary (https://www.rx7club.com/race-car-tech-103/direct-injected-rotary-456213/)

afgmoto1978 08-23-05 01:42 PM

Direct Injected Rotary
 
Does anybody know if Mazda has played with the idea of direct injection on a rotary? Theoretically if you do it right you could revert back to pheripheral and side ports make a whole lot more power, get better fuel economy (finner spray and more controlled) and still pass emissions. Plus you wouldn't have to worry about overlap because it would just be air, which is a way to cheat in reducing emission. If I win the lottery :p: I might see if this is possible.

grantmac 08-23-05 07:35 PM

I thought about making adaptors to mount common-rail diesel injectors in the trailing plug holes and then running a sequential injection controller and pumping fuel through them. Because there are existing threaded holes it should mainly be a question of finding a pump/plumbing and a suitable EFI controller. Of course you'd also need pretty beefy injectors in you only had 2 per cylinder, unless you ran staged and just used the direct injection at lower RPM and then added a second set of traditional injectors for high RPM. It's nice to dream but I dunno if the gains would justify the costs.
Grant

P.S. Direct injection does have great benefits for turbo applications.

neit_jnf 08-23-05 08:11 PM

?? how many threads about it you have? I replied to another one...

Mazda has several prototypes

rotarygod 08-23-05 09:15 PM

Racing Beat did it on their 3rd gen Bonneville car. 2 injectors per rotor flanking the intake ports.

afgmoto1978 08-26-05 01:21 PM

Two, just to get it out there.

What did Racing Beat think about it, how did they do it?

Snrub 08-28-05 10:54 AM

Here's some stuff on direct injection rotary prototype engines that Mazda has developed: http://www.geocities.com/jeffguilfoil/discmiller.html

I can't see why it wouldn't be a good idea: stratafied charges means increased fuel economy, less heat production, detonation resistance and emissions. It seems like it might open new avenues for more performance as well (eg. see what VW has done with their high compression turbo engines).

afgmoto1978 08-29-05 06:31 PM

The question is then is will we see examples in the near future? Wouldn't that be cool if we saw it on the new RX-7. I know some of you will say the RX-7 is dead, but a guy can hope can't he? Anyways next year if I can scrounge up enough money I might start playing with this. Snrub thanks, have you found any visual examples? Further, have you found if Mazda has played with direct injectors located anywhere else other than near TDC? then again if you do it right that would be the most efficient.

turbo80cid 08-31-05 09:15 PM

I drove a direct injection Audi A4 with a 2.0L turbo engine.
The compression ratio was 10.5:1 and I think it runs like 8-10psi of boost.
It’s a great engine:
Turbocharged DOHC in-line 2.0 liter 4-cylinder with FSI® Direct Injection, variable valve timing and intake manifold
Displacement: 2.0 liters
Bore: 3.25 in.
Stroke: 3.65 in.
Compression ratio: 10.5:1
Horsepower: 200 hp @ 5,100-6,000 rpm
Torque: 207 lb-ft @ 1800-5000 rpm

And with reprogramming the ECU you can get 252hp and 303lb-ft torque.

Oh ya, the new Mazdaspeed 6 ......the allwheel drive 2.3L turbo with like 275hp is direct injected!!!!!

neit_jnf 09-01-05 06:27 AM

We may see a direct injected rotary, who knows

The soon to be released Mazdaspeed 6 uses a 2.3 L 4-cyl Gasoline Direct Injected Turbocharged engine with 9.5 CR, 15.6 psi boost and produces 276 hp.

The most interesting info that I found about this engine is that it runs at stochiometric afr's !! The fuel metering of a direct injected engine can be so precise to allow a high compression, high boost engine to run like this with no detonation!

Snrub 09-01-05 03:24 PM

The interesting thing about a stratified charge is that the gas is not distributed evenly, it has an area of higher concentration. Persumably that's why it's able to run 'lean' as mentioned above?

neit_jnf 09-01-05 04:50 PM


Originally Posted by Snrub
The interesting thing about a stratified charge is that the gas is not distributed evenly, it has an area of higher concentration. Persumably that's why it's able to run 'lean' as mentioned above?

correct, also because the fuel is injected near or at tdc so there's no gas in the mixture while it's getting compressed, thus, no detonation

afgmoto1978 09-05-05 03:03 AM

Half step away from being a diesel. lol

turbo80cid 09-05-05 08:14 AM


Originally Posted by afgmoto1978
Half step away from being a diesel. lol

the one thing I didn't like was the sound, it had that diesel type of knock sound.

grantmac 09-05-05 08:32 PM

I like that sound! Besides, a rotary is so loud you'd be hard pressed to notice the injector noise. I think that of all the engines out there, the turbo rotary could benefit the most from direct-injection.
Grant

digitalsolo 09-06-05 01:31 PM


Originally Posted by neit_jnf
We may see a direct injected rotary, who knows

The soon to be released Mazdaspeed 6 uses a 2.3 L 4-cyl Gasoline Direct Injected Turbocharged engine with 9.5 CR, 15.6 psi boost and produces 276 hp.

The most interesting info that I found about this engine is that it runs at stochiometric afr's !! The fuel metering of a direct injected engine can be so precise to allow a high compression, high boost engine to run like this with no detonation!

That set of specs sounds an awful lot like a Miller cycle engine, using a turbosupercharger instead of a standard supercharger.

Interesting concepts no doubt, could help a lot with the drawbacks of rotary design.

turbo80cid 09-06-05 02:02 PM


Originally Posted by digitalsolo
That set of specs sounds an awful lot like a Miller cycle engine, using a turbosupercharger instead of a standard supercharger.

Interesting concepts no doubt, could help a lot with the drawbacks of rotary design.

I don’t know how the “Miller Cycle” works but I thought it was holding either the intake or exhaust valve open when they would be normally closed on a standard 4-cycle engine. (Intake or exhaust cycle)
I’ll have to look it up and read more about it.

rotarygod 09-06-05 02:13 PM

1 Attachment(s)
I took these pictures at the Racing Beat open house after last years Sevenstock. This is an actual housing out of the Bonneville 3rd gen. They rebuilt the engine right before Sevenstock. You can clearly see the fuel injector locations next to the intake port. In the top picture you can also see a standard Racing Beat peripheral port housings without the injector holes. They didn't have any idea about fuel economy differences since this was a single purpose race engine but it obviously worked very good for them. These were the only injector locations. The strange thing about this motor is that they have ground away all the aluminum from one side of the housing where it goes down to attach to the oil pan. Very weird. Both housings I saw from that engine were this way. Sorry for the low quality but at least you can see them.

afgmoto1978 09-06-05 02:30 PM

A true dry sump setup probably. Thanks for the pics. You didn't happen to see the housings with the direct injection setup at Racing Beat? Supposedly they been playing with this.

I wonder if they have the injectors spray after the trailing apex seal passes the exhaust port?

rotarygod 09-07-05 12:07 AM

Those are the housings with direct injection. The 2 small holes above the intake ports is where the injectors go.

neit_jnf 09-07-05 07:24 AM

those still inject the gas during the intake cycle so the compression stroke has air/gas mixture and the same afr's as port injection have to be kept. The advantage is better fuel atomization and mixing, and possibly fuel savings due to it.

The prototypes I have info on have the injectors next to the sparkplugs, so a stratified ultra lean charge can be attained without detonation concerns as the compression cycle only has air.

I haven't had time to scan the pages but I'll post them as soon as i do.

afgmoto1978 09-07-05 10:27 AM


Originally Posted by rotarygod
Those are the housings with direct injection. The 2 small holes above the intake ports is where the injectors go.

You right they are, sorry, I should have been more specific on type of Direct Injection. Did you see any housings with DI ports near TDC?

rotarygod 09-07-05 10:36 AM

Nope. These are the housings from the Bonneville car. As far as I know, these are the only ones they have played with. At least that they will disclose.

afgmoto1978 09-15-05 12:33 PM


Originally Posted by neit_jnf
those still inject the gas during the intake cycle so the compression stroke has air/gas mixture and the same afr's as port injection have to be kept. The advantage is better fuel atomization and mixing, and possibly fuel savings due to it.

The prototypes I have info on have the injectors next to the sparkplugs, so a stratified ultra lean charge can be attained without detonation concerns as the compression cycle only has air.

I haven't had time to scan the pages but I'll post them as soon as i do.

Find those pics?


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