Velocity stacks, ram air and cowl induction.....

[JeffYoung]

Carburetor section of the ITCS prohibits these, and (as we all know) requires the pick up of intake air within the engine bay or stock location. However, the ITCS ALSO says that all pipes, resonators, tubing, etc. forward of the carburetor (or AFM in an FI car) are free.

Ram air and cowl induction I therefore see as being prohibited and consistent with the pick up in the engine bay/stock location rule.

Velocity stacks? Why are they, or air horns, prohibited? Seems inconsistent with the "free ahead of the carb" rule? Anyone with "IT History" who can help me out with the thinking here?

Full disclosure: Pegasus Racing catalog just showed up with "new" air horns for my carbs with claimed 6-8 hp increase. Sure would like those, and since I'm still picking up in a legal location, having a hard time seeing why something like this shouldn't be free as a pipe, resonator, tubing, etc.

Thoughts? Is this a vestige of an old rule that should have been deletd once the intake track forward of the carb was freed up? Or is there a good reason for it?

[turboICE]

Actually in the Reciprocating Engines section.

I agree with you, based on glossary terminology the specfic exclusion of ram and cowl induction remains internally consistent with the current language. The exclusion of velocity stacks is is internally inconsistent with the remainder of the rule and explanations that were given here - unfortunately the glossary terminology is sufficiently well presented to potentially enable someone to say the exclusion of a defined element negates the subsequent freedom to substitute.

One of two things are needed, either the prohibition on velocity stacks needs to be moved to be an explicit exception to the freedom to substitute rule rather than implicit, or more approriately in line with the discussion regarding the change on these boards (i.e. attach any dang thing you please, in the engine compartment, without air metering modification) the velocity stack exclusion should be stricken.

Send a letter to the CRB and ITAC.

[pfcs]

check out the cast aluminum "sub stacks" from an MGB w/dual 1 1/2" SUs that was the base of the airfilter assy mtg. They're certainly not velocity stacks, but I'll guarantee you they'll have the same effect on airflow.
(see David Vizards "How To Modify Your BMC A Series Engine) Al ittle work with a die grinder and some creative drilling to vent the lower piston chamber and they'd work fine. PS: IXNAY the grose jets.

[Andy Bettencourt]

Jeff,

I understand your point. I think that what the rules makes want to prohibit is a 'air intake velocity accelerator' for lack of a better term.

Velocity stacks are effectively forcing more are in the car than any 'open' filter would.

[zracre]

I have seen a few cool z cars in the past with a nice airbox hiding velocity stacks...i wondered about them but began racing a FI car. Most of the intakes I see sold have a similar tapered orfice built in to them...what is the ruling on them? The one I run is a basic APC cheapie filter with no tapered stack inside...id love to run one if it is legal...

[JeffYoung]

Thanks to everyone for the responses.

Andy, understand your thinking. Counter-question (and hitting on what Evan said):

1. Couldn't I modify my pipes/tubes/resonators to speed up air flow into the carb? When does this cross the line into illegally becoming an air horn/velocity stack? Seems we have a grey area here.

2. What if I put a small high speed fan in the tubing -- not prohibited per se and arguably legal under the theory that anything in front of the carburetor is free?

I probably will write to the CRB on this one. Evan, I too have seen "shaped" connectors between the carb and the filter that certainly looked like air horns. In fact, I think I have seen them on the Z car I own with Ron that we bought last year.....

[Ron Earp]

Thanks to everyone for the responses.

2. What if I put a small high speed fan in the tubing -- not prohibited per se and arguably legal under the theory that anything in front of the carburetor is free?

[/b]

Yeah, a small high speed fan. That's it! A small high speed fan driven by, hmmmm, let's see, how could we drive it..........hmmm, I know, we could power it with an exhaust turbine! Yeah! Now, I wonder where we could get one.....hmmm, www.turbochargers.com maybe?

I don't think that is going to fly bubba. Next thing you know you'll want to spray some "gas" in the intake as a free modification!

[lateapex911]

Well, Jeff has hit, as you would expect a sharp eyed person of his background to, a pretty large contradiction in the rules, and I suspect that his idea of the velocity stacks being not considered when the "Anything goes up to the carb" rule was written, is likely the case.

Interestingly, the SIR is pretty much the same thing! A device designe by CFD to flow the maximum amout of air through a certain defined opening at the limits of theoretical possibility.

[Joe Harlan]

Well, Jeff has hit, as you would expect a sharp eyed person of his background to, a pretty large contradiction in the rules, and I suspect that his idea of the velocity stacks being not considered when the "Anything goes up to the carb" rule was written, is likely the case.

Interestingly, the SIR is pretty much the same thing! A device designe by CFD to flow the maximum amout of air through a certain defined opening at the limits of theoretical possibility.
[/b]

c. Air cleaner assemblies may be modified, removed or replaced.
Velocity stacks, ram air or cowl induction are not permitted
unless fitted as original equipment. Air intake source shall
be within the confines of the engine compartment or stock
location. Air intake hoses, tubes, pipes, resonators, intake
mufflers, housings, etc., located ahead of the carburetor/
throttle body may be removed or substituted. On cars so
equipped, the air metering/measuring device (i.e. air flow
meter, air mass meter, MAF) must be operational and shall
not be modified.

I think if you can't prove that they came from the factory with velocity stacks or cowl induction (zcars all did) then you may be stuck. No legal part can perform an illegal function. I would say that would include a free intake tube.

[lateapex911]

True, but it's a fine line between a smooth taper and a velocity stack, in certain theoretical cases, isn't it?

[JeffYoung]

Jake, thanks -- you made my point in a much clearer fashion than I was. Why are air horns/velocity stacks illegal but a tapered tube running to the carb not illegal?

I will do a letter to the CRB on this, especially since there seem to be gains for me here!

[Joe Harlan]

Jake, thanks -- you made my point in a much clearer fashion than I was. Why are air horns/velocity stacks illegal but a tapered tube running to the carb not illegal?

I will do a letter to the CRB on this, especially since there seem to be gains for me here!
[/b]

Jeff, Rather than waste a letter. There are plenty of ways to get the HP yuour looking for without having to change the basic rules of IT.

Jake, While I don't disagree if in a protest a reasonable arument can be made that the intent of the tube was to work as a velocity stack I think you loose. I really try to follow the book are close to what is written in these kinds of things.

Back to the basic rule: no legal part shall perform an illegal function.