Fuel restrictor.

**Glee** · 21st February 2007, 22:15

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

**kernel_gdi** · 21st February 2007, 22:21

dush

I think it would be stupid to create such a rule. WRC cars may contribute to contamination in the Earth in 0'0000000000000000000000000000000000000000000001 %.

surely is worse for environment a typical 15-year old van...

**Glee** · 21st February 2007, 22:34

Originally Posted by kernel_gdi

dush

I think it would be stupid to create such a rule. WRC cars may contribute to contamination in the Earth in 0'0000000000000000000000000000000000000000000001 %.

You are quite right.

But you are forgetting 2 things:
1) With this facts are nothing, image is everything!
2) Technology developed for rally could be incorporated in road cars.

**cosmicpanda** · 22nd February 2007, 03:34

It would increase development costs, which would make the manufacturers unhappy, and also make it difficult to compare cars with the fuel restrictor to cars with the air restrictor.

**Magnus** · 22nd February 2007, 07:45

It is actually easier to control a airrestrictor. As you maybe know :when airflow reaches a certain speed you get what is called "a critical flow", you can´t get any more air through how hard you try. Air-restrictors are therefor a simple way of regulating the output of an engine.

A fuelregulator, apart from some more complex homologisation issues, is a more complicated device since you can alter the flow by turning the pressure up and dow. And since the fuel is so energy-dense it is very important that you have en exact equal amount of fuel injected into every engine. This may altered however by:
- Pipelength and path (altering the temperatur and pressure)
- The position of the pump (altering the temperature of the pump thus making it more or less efficient.)
- The position of the measuring device (heatrelated; gives different results depending on the temperature of the devise)
- Different engines require different fuelpressures, so different designs are anyway required to cope with the control.

There are some other issues as well, but let´s not dive into the but simply acknowledge that airflowrestrictors is the best we have. You simply can not burn more fuel than you have got air. Besides it is so very easy to control compared to a fuelregulator.

When it comes to mother nature: well that is a nother very complex question. IMO the sport as a whole must lead the development of creating a environmentally sustainable sport. Alternative fuels, carbondioxide-neutral rallies and so on. What ever it takes. The on going discussion and the effect us humans have on the climate will at some point jeopardize rallying itself. All action must be taken, NOW, to avoid that, not through fuel regulators though

There is another issue related to the unholy bond between air and fuel though: that is HC. The emission of HC will however be much better when the new S2000-cars gain ground. The turbos need heaps of cooling, heaps of cooling equals HC.

IMHO

**bowler** · 22nd February 2007, 08:56

air restrictor does the same job. no moving parts (well normally anyways :-))

as magnus says, this restricts the fuel automatically.

**Sulland** · 2nd December 2021, 06:31

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** · 2nd December 2021, 10:26

it also depends on how much boost are you running

**Mirek** · 2nd December 2021, 16:46

Originally Posted by 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?

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** · 2nd December 2021, 23:21

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!