ITB, how much more power?

[Dimman]

Originally Posted by 1660

What about the DI? Or are you talking about going regular FI?

I'm not super sure about that one. The problem is that it's not just Direct Injection, it's D4-S, which has basically normal and direct together.

But they are used in different situations. So tuning the fueling (assuming something like the Accessport or eManage Ultimate can do it) will require some new learning for the tuners.

However I don't think it will be much different than having two fuel maps instead of one, that are maybe used simultaneously (I'm just speculating/hoping here). So depending on load and the assorted variables, the port sprays a certain amount and the direct sprays a certain amount. In certain cases one may not spray but the other does, to take advantage of whichever is better for the situation. (I personally don't even have a starting idea on when it is direct and when it is port.)

I'm expecting a lot more expensive dyno time...

[Matador]

Or use DI most of the time and port to augment fuel.

[serialk11r]

Port is for low load since fuel mixes better when it passes through the narrow valve opening, direct is for max power as it allows more effective charge cooling.

[1660]

Originally Posted by MatadorRacing_F1

Or use DI most of the time and port to augment fuel.

This makes sense because the DI would have limits based on the stock TB. Putting a larger TB and cam would require more fuel. You could probably go to a larger injector to augment the DI.

Could you add a fifth injector and a piggyback?

[Dimman]

Originally Posted by serialk11r

Port is for low load since fuel mixes better when it passes through the narrow valve opening, direct is for max power as it allows more effective charge cooling.

I may have to check out some Lexus forums and see what they know about this.

The 'narrow valve opening' doesn't make sense here, as the valves go though their complete motion range regardless of load.

Maybe lets put in terms of intake air velocity and the ability to generate combustion chamber turbulence. At low rpm the air is coming in slowly and makes less turbulence. But Subaru uses 'TGVs', Tumble Generating Valves, and I think Toyota has adopted these as well. Their job is self-evident, trying to introduce more combustion chamber turbulence at the lower intake speeds.

Now what does this mean for fueling? I would have thought that the slower intake and poor turbulence would mean that a port injection wouldn't be as good at creating an even mixture? IDK... Research time.

I think, personally, I would tune it as if it were 'normal', controlling the more familiar port system most of the time and using the direct system at higher throttle positions (the acceleration 'squirt') and higher rpm (when richening it for power). Basically try to use the DI part like the old Additional Injector Controllers?

^ There is more to this but I am not a tuner. The acceleration 'squirt' has something to when you are rapidly opening the throttle there is some 'lag' in the injection that needs to be accounted for. And load is more than just throttle and rpm, Manifold Absolute Pressure (MAP) and intake air temp come into play as well. Argh, I need more knowledges! (This is Speed-Density method of airflow measurement.) But as far as I know my Legacy uses a Mass Air Flow sensor, and the MAP sensor is just for the transmission.

I really need to study up on tuning more in depth.

Sorry for the rambliness...

[serialk11r]

I think even with tumbler generating valves, the velocity is highest around the valve, which would explain why port injection would work to that purpose. I'm not 100% sure but this is the only way it would make sense, as port is definitely not as good as direct under high power.

I remember reading about how VW TSFI engines have high particulate matter emissions...sounds like poor combustion?

[Dimman]

Originally Posted by serialk11r

I think even with tumbler generating valves, the velocity is highest around the valve, which would explain why port injection would work to that purpose. I'm not 100% sure but this is the only way it would make sense, as port is definitely not as good as direct under high power.

I remember reading about how VW TSFI engines have high particulate matter emissions...sounds like poor combustion?

I'm generally talking about overall intake velocity, since the local velocity changes as the air moves through the various areas of the port, smallest being, as you mention, when the valve is coming off the seat. So yes it speeds up as it passes between the valve's circumference and seat, but if the intake speed is overall slow due to low RPMs it is still 'slow'. This was something that Toyota/Yamaha tried to solve with the TVIS system on the 4AGE and 3SGE. It changed the area by having two runners per cylinder, one of which would be closed at low rpm to keep velocity high.




TGV's seem to be similar in concept, by changing the area of a single runner.




Maybe.


But one thing with slow moving air with fuel in it (as from a port injector) is that the fuel can fall out of suspension. And this is why the low speed port thing doesn't make too much sense to me. All of these devices, seem to be swirling the air more than it would on its own, and I can only think that it is to maintain an even air/fuel mix.

But like I said earlier, this is something that I need a lot more research on...

[1660]

The technology at low load or RPM concerns emissions. If performance is the concern then AFR and fuel into the cylinder is more important.

If you're upgrading the cam, the last thing you're concerned about is emission.

[Matador]

Originally Posted by 1660

This makes sense because the DI would have limits based on the stock TB. Putting a larger TB and cam would require more fuel. You could probably go to a larger injector to augment the DI.

Could you add a fifth injector and a piggyback?

Pretty sure you mean a 9th injector

[Matador]

Originally Posted by serialk11r

Port is for low load since fuel mixes better when it passes through the narrow valve opening, direct is for max power as it allows more effective charge cooling.

This is in essence how it works stock. I think they also use port at startup/idle, or vice versa, can't remember and too lazy to check.

I was however referring to how we could use the system to our advantage in a tuned situation, with ITBs or FI and use the port injectors to augment fueling @ WOT or heavy load situations.

[madfast]

Originally Posted by Dimman

I personally don't even have a starting idea on when it is direct and when it is port.

lets hope the ecu can be easily tuned

[madfast]

more reading material to salivate over:

http://www.sae.org/automag/techbrief...1-114-1-17.pdf

[1660]

Originally Posted by MatadorRacing_F1

Pretty sure you mean a 9th injector

You're right! That's what happens when you can't count.

[Matador]

Originally Posted by madfast

lets hope the ecu can be easily tuned

If you believe in Santa, maybe it will.