Direct fuel injection?????
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From: Ohio
Direct fuel injection?????
ok has any rotary ever had direct injection or has anyone ever done this???? in piston engines it can add up to 15% HP and 30% fuel effecintcy because it allows the engine somehow to run very lean 50:1. but if it has be done let me know, cause it might be the project i start if it hasnt been done, i dont know how the new rx-8 fuel control is but my guess it isnt direct inject. thanks if anyone has any info 
I'd say direct injection would need to be right near the plugs. The injectors could be installed right above the trailing plug where the knock sensors are. This would allow some time for advancing the timing and all that.
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From: Wayward Hayward
I've thought of this idea myself... Has this been done?
I know that efficiency gain would be the main advantage, but a rotary engine is very different than a boinker.... I know that some of the other cars I've read about that do this, have a very sophisticated fuel management system, and a very high pressure fuel system to initiate lean burn zones.
thats my 2 cents...
I know that efficiency gain would be the main advantage, but a rotary engine is very different than a boinker.... I know that some of the other cars I've read about that do this, have a very sophisticated fuel management system, and a very high pressure fuel system to initiate lean burn zones.
thats my 2 cents...
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From: Saskatoon, SK & Montreal, PQ
With piston engines, direct injection allows the air/fuel to mix in the chamber.
In ultra-lean mode (most normal driving conditions, up to speeds of about 120km/h) fuel injection occurs at the latter stage of the compression stroke and ignition occurs at an ultra-lean air-fuel ratio of 30 to 40 (35 to 55 when EGR is factored in)
When a GDI engine is operating with higher loads or at higher speeds, fuel injection takes place during the intake stroke. This optimizes combustion by ensuring a homogeneous, cooler air-fuel mixture that minimizes the possibility of engine knocking.
What these have in common is a compression & combustion chamber that stays in one spot relative to the injector, regardless of the stroke action of the piston.
In both cases the GDI engine has a slight difference in piston and port design over a conventional engine: The GDI engine has upright straight intake ports rather than horizontal intake ports to direct the airflow down at a curved-top piston, which redirects the airflow into a strong reverse tumble for optimal fuel injection.
With the arc of compression in a rotary, GDI becomes far less practical. You'd need a fuel injector near the air intake port (pretty much where it is now) and another further along the compression path, meaning yet another hole in the housing, a second fuel rail, and a valve and control mechanism to determine which injector sprays the fuel in. And the shape of a rotor and housing doesn't allow much in the way of air-tumble management.
you would NOT want to inject the fuel by the plugs, because that would mean spraying cold wet fuel into the already compressed air. This would leave no time for the air and fuel to atomize and mix.
This takes away the main benefit of direct injection. In a piston engine the fuel can be sprayed in near the spark plug. This puts the greatest concentration near the plug, so when the spark ignites the fuel most of it instantly explodes.
A rotary, in contrast, would still have the fuel travelling on pretty much the same path, in the same curved collapsing chamber, prior to combustion and the same fuel pockets at the back of the chamber (rear apex).
Thus there is little to no benefit to a GDI rotary that is not negated by the added parts and complexity.
In ultra-lean mode (most normal driving conditions, up to speeds of about 120km/h) fuel injection occurs at the latter stage of the compression stroke and ignition occurs at an ultra-lean air-fuel ratio of 30 to 40 (35 to 55 when EGR is factored in)
When a GDI engine is operating with higher loads or at higher speeds, fuel injection takes place during the intake stroke. This optimizes combustion by ensuring a homogeneous, cooler air-fuel mixture that minimizes the possibility of engine knocking.
What these have in common is a compression & combustion chamber that stays in one spot relative to the injector, regardless of the stroke action of the piston.
In both cases the GDI engine has a slight difference in piston and port design over a conventional engine: The GDI engine has upright straight intake ports rather than horizontal intake ports to direct the airflow down at a curved-top piston, which redirects the airflow into a strong reverse tumble for optimal fuel injection.
With the arc of compression in a rotary, GDI becomes far less practical. You'd need a fuel injector near the air intake port (pretty much where it is now) and another further along the compression path, meaning yet another hole in the housing, a second fuel rail, and a valve and control mechanism to determine which injector sprays the fuel in. And the shape of a rotor and housing doesn't allow much in the way of air-tumble management.
you would NOT want to inject the fuel by the plugs, because that would mean spraying cold wet fuel into the already compressed air. This would leave no time for the air and fuel to atomize and mix.
This takes away the main benefit of direct injection. In a piston engine the fuel can be sprayed in near the spark plug. This puts the greatest concentration near the plug, so when the spark ignites the fuel most of it instantly explodes.
A rotary, in contrast, would still have the fuel travelling on pretty much the same path, in the same curved collapsing chamber, prior to combustion and the same fuel pockets at the back of the chamber (rear apex).
Thus there is little to no benefit to a GDI rotary that is not negated by the added parts and complexity.
Last edited by Manntis; Oct 31, 2003 at 01:28 PM.
Oh, ok. I must have been thinking of diesel injection for a rotary. The injector would be a bit different than what we're used to. It would consist of a small orb on a pedestal inside of a venturi with compressed air blown over it. This would atomize the fuel well enough to place it near the plugs. Thoughts?
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From: Ohio
the gdi's opperate at 1200 psi averadge, and the price of one of those injectors would be around 100+, but you would only need two.... and manntis i dont know if i can completely agree with you but you do hold words of vast wisdom..... i think it could be a great break through or flopp in the rotary world.... so incontrast it never hurts to try...... except for the money thing 
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From: Cloud Nine & Peak of God
Have a look at what Hitman has done to put efi on a 12A. His site lists all the parts needed including using a 13B housing to get about 180rwhp with a mild porting job. Its a little on the costly side but well worthwhile if you are looking for a good power range. You can get at least 40hp qver the best carb modification
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