New 2015 fuel flow Directive

[Mesteño]

"constant above a flow rate of 90kg/h."

Not native speaker, but I can see a hole in this.

[NL_Fer]

Charlie demands the fuelpressure te remain constant. What leds me toe believe, that under certain conditions, teams increase the injected fuel to exceed 100gr/h, but they limit the high pressure fuelpump to supplying 100gr/h max. This would lead to a drop in fuelrail pressure.

I think if you monitor the fuelrail, pressure is at 500bar at corner exit, than drops to say 250bar during acceleration, only to recover again in the braking zone. Maybe even later. Driver exits corner en floors the throttle, fuel pressure is increased to max, 500bar, then drops during acceleration.

[Yurasyk]

How it is possible to use less than 100 kg of fuel in 1,5-2 hour race with constant [instantaneous?] flow rate above 90kg/h ?

[Silent Storm]

It basically means there should be no fluctuation between 90kg/hr to 100kg/hr fuel flow. It should be consistent.

[enri_the_red]

How it is possible to use less than 100 kg of fuel in 1,5-2 hour race with constant [instantaneous?] flow rate above 90kg/h ?

Jon Noble's tweets are quite imprecise, he (wrongly) uses "fuel flow" instead of "fuel pressure", I suggest you to read the article from motorsport

[Yurasyk]

Jon Noble's tweets are quite imprecise, he (wrongly) uses "fuel flow" instead of "fuel pressure", I suggest you to read the article from motorsport

Thank you for clarification.

[Sevach]

This one is to be implemented immediatelly?

[mikeerfol]

According to Kravitz yes, Charlie may open any car's fuel system and have a look at it.

[ian_s]

there does appear to a lot of confusion in the media about this. the Autosport article says that the fuel pressure must remain constant, yet a lot of places are reporting that the flow must remain constant which is just absurd.

I think what's been happening,using totally made up numbers:
at full throttle the high pressure system is at 400 bar, using 100 kg/h
under low throttle openings, the pumps are still pumping 100 kg/h but the engine is only using 20 kg/h, and the pressure relief valve only flows 20 kg/h
the extra 60 kg/h has to go somewhere, so the fuel pipes balloon slightly, and the pressure rises to the maximum 500 bar at which point the pressure relief valve opens more to limit the pressure.
once the driver calls for full throttle again, the extra pressure pushes more fuel through the injectors for a brief time, giving more power. even if its just 10 HP for 1 second out of every corner, that's probably worth it. it all depends how much fuel you can store in the fuel lines

[Tim.Wright]

In my opinion, Autosport have interpreted it wrongly:

On Saturday, the FIA sent teams a further directive - which has been seen by AUTOSPORT - to clarify what they are allowed to do.

It specified that fuel pressure in the high and low pressure systems must "remain constant above a flow rate of 90kg/hr", meaning it must stay in the 90-100kg/hr rate at all times.

I haven't seen the original FIA document, but according to the quote from Autosport the PRESSURE needs to remain constant ONLY when the fuel rate is OVER 90kg/h.

The tweets from Jonathon Nobel are wrong in the same way - they have both then mistaken pressure for flow rate, and somehow deduced that it must be constant at all times...

[R_Redding]

I haven't seen the original FIA document, but according to the quote from Autosport the PRESSURE needs to remain constant ONLY when the fuel rate is OVER 90kg/h.

The Autosport text is....

It specified that fuel pressure in the high and low pressure systems must "remain constant above a flow rate of 90kg/hr", meaning it must stay in the 90-100kg/hr rate at all times.

Doesn't this imply that that the fuel pressure must remain at a level that would be needed to pump the 90-100kg/hr rate, irrespective of the actual comsumption rate (ie..off throttle idling).

Rob

[Tim.Wright]

No, it means it must remain constant when the rate is >90kg/h. Under that rate it can be variable.

Otherwise they would have simply said "fuel pressure must remain constant at all times".

[R_Redding]

No, it means it must remain constant when the rate is >90kg/h. Under that rate it can be variable.

Otherwise they would have simply said "fuel pressure must remain constant at all times".

Yes .. your right ... much clearer when reading Adam Cooper on motorsport ,than the article on Autosports web which is wrong.

Rob

[mikeerfol]

https://twitter.com/tgruener/status/597718345417392128

[Edis]

Charlie demands the fuelpressure te remain constant. What leds me toe believe, that under certain conditions, teams increase the injected fuel to exceed 100gr/h, but they limit the high pressure fuelpump to supplying 100gr/h max. This would lead to a drop in fuelrail pressure.

I think if you monitor the fuelrail, pressure is at 500bar at corner exit, than drops to say 250bar during acceleration, only to recover again in the braking zone. Maybe even later. Driver exits corner en floors the throttle, fuel pressure is increased to max, 500bar, then drops during acceleration.

Direct injected engines typically adjust fuel pressure depending on engine load, but normally you see the high pressures during high load and low pressure during part load. That's why the FIA demand that the fuel pressure must be constant only above 90 kg/h. That way lower pressures at part load is still possible.