Fuel restrictor.

[Glee]

All rally cars are equipped with an air inlet restrictor. This is to limit the power and level the playing field.

This is an simple and easy manageable solution.

But what if there was an restrictor to the fuel consumption instead of the air intake?

This would be to promote more fuel-efficient engine and less pollution.

A fuel restrictor (wo did limit the fuel consumption to a specific quantity pr. second) would be a lot more difficult to make tamperproof, but it wold give rally a greater image as an environment friendly sport.

This is something witch only will be more and more important. Rally Norway was CO2 neutral. Read more: http://www.rallynorway.com/en/pressr...-advocate.html

[Sulland]

I tried to find a good dicussion that was going a while back, regarding how much difference 1 mm will represent.
I could not find back to it, but found this old one on the same topic.

Rally3 went up 1 mm from 30 to 31, and got 20 hp more. So it is closing in on Rally2 that officially has 290 and now Fiesta Rally3 with 235 hp.

So my question would be:
If a Ford Rally3 with 1500cc engine was given a 32mm restrictor, how much power would that one gain from 31 to 32mm?
I am guessing that the calculation would not be 100% linear, and we have a difference of 100cc as well.

Is there a simple way to calculate power increase to an engine type, if you increase the restrictor with x mm?

[ictus]

it also depends on how much boost are you running

[Mirek]

I tried to find a good dicussion that was going a while back, regarding how much difference 1 mm will represent.
I could not find back to it, but found this old one on the same topic.

Rally3 went up 1 mm from 30 to 31, and got 20 hp more. So it is closing in on Rally2 that officially has 290 and now Fiesta Rally3 with 235 hp.

So my question would be:
If a Ford Rally3 with 1500cc engine was given a 32mm restrictor, how much power would that one gain from 31 to 32mm?
I am guessing that the calculation would not be 100% linear, and we have a difference of 100cc as well.

Is there a simple way to calculate power increase to an engine type, if you increase the restrictor with x mm?

Very roughly you can compare areas of the restrictor because that is the main limiting factor of the air passing through. IMHO it should work quite well for cars within the same class where the boost is limited to the same value.

30 mm - 706,5 mm2
31 mm - 754,4 mm2 - 6,8% more than 30 mm
32 mm - 803,8 mm2 - 6,5% more than 31 mm

20 Hp power gain by raising the restrictor from 30 to 31 mm does not seem likely to be caused by the restrictor alone. IMHO it shall be less. Maybe the Rally3 Fiesta was limited by other factors as well through this season (let's not forget that the first Fiesta R5 didn't use full turbo boost until faster opposition arrived purely for reliability reasons). Maybe Br21 can say something about that.

[Steve Boyd]

The thickness of the boundary layer means the effective bore will be a little bit smaller than measured bore and it will be the same thickness on big and small restrictors. The benefit of increasing the bore will be a little bit bigger than the ratio of the areas - just don't ask me by how much, it has been a very long time since I studied fluid mechanics!