Hi all,

As we all know people have been getting different results with the same orfice (inner hole restrictor size). Some overboost at 1.20 mm and some underboost at 1.20mm. Does the length of the restrictor matter I wonder ?

I mean the factory restrictor was about 1/3 inch long, the one I replaced it with was about 1 inch long. Someone has said the length does not matter; however, the more I think about it the more I think that this may be the reason for diff results with same cars, same mods and same restrictor orfice sizes.

Thoughts ?

Cheers,
Ray

 

It will matter, the restriction is also a function of length, possibly proportional to length, can't remember off the top of my head.

John banks has done all the work, made restrictors etc.

I think last time round, we agreed that length could be used to fine tune the restriction between drill sizes.

Paul

 

Interesting,

I thought this may be the case. Do you know if longer restrictor = same as making hole bigger (ie: limiting boost) or is it the other way around ?

Cheers,
Ray

 

longer is same as a smaller hole, but much less pronounced effect.

think the overall restriction to flow is proporional to the squareroot of the length (maybe even cube root)

paul

 

Really ?

I thought it would be the other way around ie:

Longer = less boost = bigger hole

Can you confirm that it is indeed the opposite way around.

Cheers,
ray

 

Well, let me put it this way, when I talk about restriction, I mean just that, flow through the restrictor.

Longer restrictor = more restriction

I don't know the velocity involved, but there is a good chance the flow throught the restrictor is laminer. If so, the pressure loss accross the restrictor is proportional to the length.

This is the same as the flow through a long hose being less, due to pressure loss over the length of the hose.

I don't use restrictors, because I have a 3 port solenoid.

Making the restrictor longer will have a similar effect to using a restrictor with a smaller hole. Feel free to use that statement however you wish.

Paul