Quote:
Originally Posted by bill dedman
I was GOING to suggest that the rationale behind open or closed-off scoops would logically lay with the engine's original horsepower factor; if the engine was out of a car that had fresh air, then the factord HP rating would reflect that, and in a different chassis, then it would be legal with an open scoop (fresh air.) That made all kinds of sense to me. Anything else, and you're not being true to the original operational parameters that gave the engine that particular factor in the first place.
THEN, before I made a complete fool of myself by posting something that had a hint of logic to it, I decided to go and see how much factored HP difference there was in the so-called "Ram-Air" (fresh air) packages that used open scoops, and the ones that didn't (otherwise identical engines, like the early Cobra Jat Mustangs, some of which had "Ram Air".)
Guess what??? NO DIFFERENCE! At some point, NHRA has decided that a fresh air package is worth NOTHING in terms of factored horsepower... but, they stilll list the different (fresh air or no) combinations.... they just give them identical horsepower.
Admittedly, I only looked at a few examples, but it was obvious to me from what I saw, that NHRA had gone through the list and either cut the fresh air motors back to the closed-in, no scoop models' factored HP ratings, OR upped the rating on the no-scoop models to match the fresh air engines' factors.
I must not have been in class that day.... That phenomenon has come about totally without my having noticed it.
Beings that there's no difference in the ratings, why would they CARE which engines have operational fresh-air systems??? I can't imagine that they would.
So, this is one in which there IS no argument that I can see, that scoops that were on a car would have to be closed off, because as NHRA has shown us in their sacred Classification Guide, they aren't worth even ONE HORSEPOWER.... Check it out...
Admittedly, I didn't check them all, but I did look at several combinations that had both underhood air vs. fresh air, and all the ones I looked at had identical factors.
It is a mess...
Bill
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Sorry Bill, that occured maybe 20 years ago? I'm not sure when but it was a LONG LONG time ago. It's a technicality as to when and why but I'm under the impression it was a result of 428 CJ racers changing hoods from flat (Q code) to shaker (R code) and NHRA seeing it didn't seem to affect performance one way or the other. I can only offer my own experiments on my '70 AMX. I was curious in D/S what the affects were. Sealing off the scoops (which probably aren't much more; if any, effective of something like a mopar / ford shaker), and even running with and without a K&N filter I found no ET one way or another and MAYBE as much as (point) .2 MPH. And that's on a 124-125 MPH stocker.
I'm sure a 145-150 MPH SS car like a SS Dart/Barracuda or SS/AMX would see different results but NHRA has, as Bill pointed out, set the bar across the board that it doesn't seem to matter.
I still contend the scoop is a body part not an engine part and if NHRA allows cars like Hale or Teuton (non-hemi in '68 hemi A-body SS/GT car), then it should be across the board. That would include the SS/AMX scoop and the L-88 Corvette scoop.