Don Terrill’s Speed-Talk

Just look at this explanation of last MPFI Systems

On last gen NA F1 engines

http://www.racecar-engineering.com/arti ... l-systems/

Dave B.

I found this interesting. Very high pressure so probably very fine most and 40% duty cycle so they are only spraying into the moving air stream.

Injection pressure is limited to a maximum of 100 bar......

18,000rpm – before the limiter kicks in – the fuel injector is fired once every 6.6ms for a duration of 2.7ms at full throttle.

mk e wrote: ↑Mon Nov 12, 2018 7:45 am I found this interesting. Very high pressure so probably very fine most and 40% duty cycle so they are only spraying into the moving air stream.

Injection pressure is limited to a maximum of 100 bar......

18,000rpm – before the limiter kicks in – the fuel injector is fired once every 6.6ms for a duration of 2.7ms at full throttle.

The Honda papers show when they start/end injecting. Of course that was ten years ago...

mk e wrote: ↑Mon Nov 12, 2018 7:45 am I found this interesting. Very high pressure so probably very fine most and 40% duty cycle so they are only spraying into the moving air stream.

I would think, depending on how the injectors are placed and oriented, injecting when the air is moving would be the furthest from optimal, from an airflow standpoint. The injector stream can act as an air door.

Only dyno testing can tell you for sure.

Development of High-Pressure Fuel Supply System for Formula One Engine : www.f1-forecast.com/pdf/F1-Files/Honda/F1-SP2_15e.pdf

peejay wrote: ↑Mon Nov 12, 2018 7:12 pm

mk e wrote: ↑Mon Nov 12, 2018 7:45 am I found this interesting. Very high pressure so probably very fine most and 40% duty cycle so they are only spraying into the moving air stream.

I would think, depending on how the injectors are placed and oriented, injecting when the air is moving would be the furthest from optimal, from an airflow standpoint. The injector stream can act as an air door.

Only dyno testing can tell you for sure.

Spraying into the moving stream should produce the maximum air cooling effect. Any fuel that lands on the runner or port walls will cool the runner/port instead of the air so the effect is mostly wasted and you risk drops falling in which won't burn well.

mk e wrote: ↑Tue Nov 13, 2018 7:55 am

peejay wrote: ↑Mon Nov 12, 2018 7:12 pm

mk e wrote: ↑Mon Nov 12, 2018 7:45 am I found this interesting. Very high pressure so probably very fine most and 40% duty cycle so they are only spraying into the moving air stream.

I would think, depending on how the injectors are placed and oriented, injecting when the air is moving would be the furthest from optimal, from an airflow standpoint. The injector stream can act as an air door.

Only dyno testing can tell you for sure.

Spraying into the moving stream should produce the maximum air cooling effect. Any fuel that lands on the runner or port walls will cool the runner/port instead of the air so the effect is mostly wasted and you risk drops falling in which won't burn well.

Check the link I posted and they show exactly when there injecting in the cycle. It’s not just during valve open.

hoffman900 wrote: ↑Tue Nov 13, 2018 9:55 am
Check the link I posted and they show exactly when there injecting in the cycle. It’s not just during valve open.

But its mostly just during ivo and they say is for the purpose of air cooling. They appear to have been flow rate limited and kept ramping up pressure to increase flow.

mk e wrote: ↑Tue Nov 13, 2018 10:05 am

hoffman900 wrote: ↑Tue Nov 13, 2018 9:55 am
Check the link I posted and they show exactly when there injecting in the cycle. It’s not just during valve open.

But its mostly just during ivo and they say is for the purpose of air cooling. They appear to have been flow rate limited and kept ramping up pressure to increase flow.

I'll add that more interesting to me is that pretty much anyone can now have this same tuning control. Big well matched and characterized injectors are readily available as are ecus that are fast enough to handle this.

mk e wrote: ↑Tue Nov 13, 2018 10:05 am

hoffman900 wrote: ↑Tue Nov 13, 2018 9:55 am
Check the link I posted and they show exactly when there injecting in the cycle. It’s not just during valve open.

But its mostly just during ivo and they say is for the purpose of air cooling. They appear to have been flow rate limited and kept ramping up pressure to increase flow.

They reported a decrease in droplet size with higher pressures, that’s not a flow issue. They were also able to measure the cooling effects by the change in pulse timing due to density changes.

hoffman900 wrote: ↑Tue Nov 13, 2018 10:28 am
They reported a decrease in droplet size with higher pressures, that’s not a flow issue. They were also able to measure the cooling effects by the change in pulse timing due to density changes.

They didn't reduce the injector size to get constant pulse time with varying pressure. Yes the droplets were smaller but the injection pulse was also shorter and more complete at ivc. They appeared to specifically avoid spraying near ivo.

The only conclusion possible is that higher pressure helped.....

Fuel injectors without air are very poor for atomization and providing a burnable mixture; at a clear disadvantage to a carb which has emulsification. One of the ways to improve the inherent poor fuel spray quality of a pressure atomizing injector is jack the pressure to the moon. That and the nozzle location for heat of vaporization is making up for the inherent fuel injection disadvantage for power.

Ken_Parkman wrote: ↑Tue Nov 13, 2018 12:27 pm Fuel injectors without air are very poor for atomization and providing a burnable mixture; at a clear disadvantage to a carb which has emulsification. One of the ways to improve the inherent poor fuel spray quality of a pressure atomizing injector is jack the pressure to the moon. That and the nozzle location for heat of vaporization is making up for the inherent fuel injection disadvantage for power.

Honda reported they were able to reduce fuel droplet size to <20μm* by increasing pressure, which increased power and reduced adherence to port walls. In Phase 5 development (2009), they were able to increase the injector plate pressure from 4.7 to 8.9 MPA (despite a rule imposed ceiling of 10 MPA for the feed), and achieved an average a droplet size of 17μm.

<20μm = <0.000787402". For reference a red blood cell is ~5-8μm, so this is very tiny.

This is also interesting...

"The relationship between penetration and the phase of intake air pulsation was also sutdied. As Fig. 8 shows, there is a peak in the intake air phase delay, indicating the existence of an optimum penetration for the achievement of increased intake air cooling efficiency. If the level of penetration is low, the spray will approach the center of the port due to the effect of the intake air. If the fuel is carried too high, the amount of fuel adhering to the walls of the port will increase".

So in short, Formula One doesn't need textured ports because the injectors are atomizing the fuel so well. No carburetor is coming close to that. They're actually using the phase delay of the intake pulse to measure the atomization and charge cooling effect and were able to tune it. Not bad for being over a decade ago

I would love to know where they are at a decade later.

mk e wrote: ↑Tue Nov 13, 2018 10:36 am

hoffman900 wrote: ↑Tue Nov 13, 2018 10:28 am
They reported a decrease in droplet size with higher pressures, that’s not a flow issue. They were also able to measure the cooling effects by the change in pulse timing due to density changes.

They didn't reduce the injector size to get constant pulse time with varying pressure. Yes the droplets were smaller but the injection pulse was also shorter and more complete at ivc. They appeared to specifically avoid spraying near ivo.

The only conclusion possible is that higher pressure helped.....

At IVO the air is probably not moving fast yet (you think?) and weighing the air down with fuel would make it more difficult to get the air moving. By spraying toward the end of the event, they would be spraying into fast moving air and the added mass could be helping things along, inertia-wise, past BDC.

I also wonder if there is not a benefit for having the fuel in the "last air" into the cylinder. The last air in to the chamber may end up being closest to the plug. Given fuel limitations, they're under pressure to maximize fuel efficiency. The only documentation regarding THAT that I have ever read was that Honda had been running in the region of 1.1 lambda at max power... My assumption is that is an "overall" lambda figure and the mixture was considerably richer closer to the spark plug.

peejay wrote: ↑Tue Nov 13, 2018 8:04 pm

mk e wrote: ↑Tue Nov 13, 2018 10:36 am

hoffman900 wrote: ↑Tue Nov 13, 2018 10:28 am
They reported a decrease in droplet size with higher pressures, that’s not a flow issue. They were also able to measure the cooling effects by the change in pulse timing due to density changes.

They didn't reduce the injector size to get constant pulse time with varying pressure. Yes the droplets were smaller but the injection pulse was also shorter and more complete at ivc. They appeared to specifically avoid spraying near ivo.

The only conclusion possible is that higher pressure helped.....

At IVO the air is probably not moving fast yet (you think?) and weighing the air down with fuel would make it more difficult to get the air moving. By spraying toward the end of the event, they would be spraying into fast moving air and the added mass could be helping things along, inertia-wise, past BDC.

I also wonder if there is not a benefit for having the fuel in the "last air" into the cylinder. The last air in to the chamber may end up being closest to the plug. Given fuel limitations, they're under pressure to maximize fuel efficiency. The only documentation regarding THAT that I have ever read was that Honda had been running in the region of 1.1 lambda at max power... My assumption is that is an "overall" lambda figure and the mixture was considerably richer closer to the spark plug.

I thought it was interesting that they were still spraying AFTER IVC.