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TraviST185

Restrictor question?

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TraviST185

I am trying to have a restrictor made, but I need some clarification.

From the rule book, page 45 at the top, "The external diameter of the restrictor at its narrowest point must be less than 38 mm, and must be maintained over a distance of 5 mm to each side."

 

So at some point on the restrictor the outside diameter must be 38 mm or less, maintained for a distance of 5 mm. Right?

 

If anyone can explain or send me a picture with some dimensions that would be great.

 

Thanks

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wvonkessler

Travis:

 

John can probably address this. Unfortunately, he will be out of pocket until Cherokee is done.

 

Wilson

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Mike Hurst

The 38mm OD is used on restrictors which have a flange and bolt to the compressor housing. In this case, the OD of the restrictor is easily visable, so the FIA mandates the 38mm OD which makes it very easy to verify that there is in fact a restrictor in place. Of all the restrictors I've inspected this year, two have met this requirement.

 

Most US spec cars don't have a flange on inlet of the compressor housing, so the restrictor is usually just press fit into the inlet of the compressor, and the OD is not visable.

 

I am of course, in no way qualified to make a NASA rule interpretation.

 

Good luck to all at CT!

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Ivan Orisek
............and must be maintained over a distance of 5 mm to each side."

 

So at some point on the restrictor the outside diameter must be 38 mm or less, maintained for a distance of 5 mm. Right?

 

If anyone can explain or send me a picture with some dimensions that would be great.

 

Thanks

 

This is a somewhat unfortunate formulation of the rule, taken verbatim from FIA Appendix J, perhaps caused by the translation from the French original.

 

Fortunately, both in our NASA Rally Sport General Regulations for Rallies and in FIA Appendix J (from which our drawing is taken), this text is supplemented by the Drawing No 254-4 to be found at the end of GRRs. The Drawing No 254-4 shows clearly that "...maintained over a distance of 5 mm to each side" means for a total of 10 millimeters.

 

Ivan Orisek

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heymagic

I gotta ask...what does the outside diameter have to do with anything ? Does it have to do with air bypassing around the restrictor?

 

Still trying to learn about turbos...Gene ... OBTW, any restrictions on superchargers ?

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M Moyer
I gotta ask...what does the outside diameter have to do with anything ? Does it have to do with air bypassing around the restrictor?

 

Still trying to learn about turbos...Gene ... OBTW, any restrictions on superchargers ?

 

From an aerodynamic perspective, it obviously has nothing to do with it. However, I imagine that the FIA wrote that into the rules so that they could guarantee that 34 (or 32, for that matter)mm restrictor would be adhered to; ie, so they could make sure that something like the Toyota WRC "magic expanding restrictor" would never see the light of day again. Very clever piece of engineering, but obviously (& blatantly) well outside of the rules.

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