Would like opinions on why. I plan on testing various combos without the hood.
3.8 mph gain from no hood? Pics inside and input needed
- Thread starter gregsdart
- Start date
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Would like opinions on why. I plan on testing various combos without the hood.
33IMP
Well-Known Member
My only guess, and a wild-assed one at that, is from engine masters air cleaner test. They showed that direction of airflow can be important. They took a filter setup with a three inch element and a filter lid, taped off the three inch element, and made more power thru the lid only, cause the airflow was down into the carb, not across. They found the same with their "salad bowl" with the filter lid, and an old style velocity stack.
Maybe the scoop directs the air better/different without the filters?
Maybe the scoop directs the air better/different without the filters?
Sounds like your idea about airflow has a lot of merit. Another opinion offered thought my hood may have been pushing air up enough to affect entry.
I was thinking the same thing... great pressure, I'm sure, but need to defuse the hurricane entering the airbox.. (one would think the filters would do it..)
With that flat, solid top air cleaner, I would guess your scoop is doing a better job of catching air and slowing the car down, than it does forcing air into the engine. Those paper 2 and 3 inch filters arent doing any favors either.
I dont think you uncovered any aerodynamic secrets by removing the hood, but getting that solid lid out of the scoop, so it's not turning you scoop into a "open parachute" mounted to the hood, is probably the gain.
Turbulent air is a mother. Many large, prop airplanes will rotate the prop blades to help stop on the runway when landing. Rotating the prop blades doesnt cause them to spin backwards, it creates such turbulent air, that it's the equivilent of adding big " discs" to the wings.
Your scoop, with your filter lid in tact is a big ol air catch.
Bet with hood on, no filter lid, base in the scoop, is probably your best combo. For mph anyways.
Speedway motors sells the least expensive, quality filter top I have found.
I dont think you uncovered any aerodynamic secrets by removing the hood, but getting that solid lid out of the scoop, so it's not turning you scoop into a "open parachute" mounted to the hood, is probably the gain.
Turbulent air is a mother. Many large, prop airplanes will rotate the prop blades to help stop on the runway when landing. Rotating the prop blades doesnt cause them to spin backwards, it creates such turbulent air, that it's the equivilent of adding big " discs" to the wings.
Your scoop, with your filter lid in tact is a big ol air catch.
Bet with hood on, no filter lid, base in the scoop, is probably your best combo. For mph anyways.
Speedway motors sells the least expensive, quality filter top I have found.
famous bob
mopar misfit
Try putting air vents in the hood and running it , lots of air pressure under the hood on a fast car . Ever seen a hood raise up on the big end ?
Yup, I have 4 hood pins across the front of mine. But I also have a filter element top.
Thanks for responses, gentlemen! Every one has given me something to try.
Scoop only.
Nascar filters only, no hood or scoop.(they basically filter out larger particals of sand, rocks, foriegn objects)
Filter lid, tape off bottom filter, open nascar top filter, scoop, no hood.
There are more combos, plus scoop options. Lots to look into.
Would like more input/ experiances, keep this thread going as an engineering exercise!
Scoop only.
Nascar filters only, no hood or scoop.(they basically filter out larger particals of sand, rocks, foriegn objects)
Filter lid, tape off bottom filter, open nascar top filter, scoop, no hood.
There are more combos, plus scoop options. Lots to look into.
Would like more input/ experiances, keep this thread going as an engineering exercise!
I have thought of a stretched metal lid wrapped in home furnace filter material as a hi flow top. I also have a stretched metal dome that has door screen on it. I could wrap that with home furnace filter material.
33IMP
Well-Known Member
Maybe, just maybe, the scoop does provide a ram effect( you are over 150, after all !) that the filter and elements cancel out. The filters cost next to nothing on the dyno, yet you picked up(apparently) a bunch of power without them at the track. It has to have something to do with 150 mph airflow that is different from dyno airflow.
pishta
I know I'm right....
Dont the props change pitch so in essence, the props are working backwards, ie. directing the thrust forward? A C-130 can stop like a semi in a combat landing. 'Brace for short landing' is no joke!
There’s an old racers trick of adding spacers between the rear of the hood hinge and the hood to create a gap at the cowl. It gives the air being forced through the grille someplace to go and can be worth a tenth or two.
As far as filtering, I would be tempted to try one of these, if you have the scoop clearance.
[URL]https://www.summitracing.com/parts/knn-58-1200[/URL]
And combine it with one of these
K&N X-Stream Airflow Top Plates 66-0901
There’s a taller element height available, too. You could potentially get several different height 9 inch paper filters to see what works best with the X-Stream lid.
The optimal filter height should be a balance between the airflow through the top and airflow through the outer filter. You don’t want to restrict airflow, but you do you want enough air coming through the top to have enough velocity to help air from the other element “make the downward turn”.
As far as filtering, I would be tempted to try one of these, if you have the scoop clearance.
[URL]https://www.summitracing.com/parts/knn-58-1200[/URL]
And combine it with one of these
K&N X-Stream Airflow Top Plates 66-0901
There’s a taller element height available, too. You could potentially get several different height 9 inch paper filters to see what works best with the X-Stream lid.
The optimal filter height should be a balance between the airflow through the top and airflow through the outer filter. You don’t want to restrict airflow, but you do you want enough air coming through the top to have enough velocity to help air from the other element “make the downward turn”.
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A little off topic but interesting. https://www.hotrod.com/articles/new-tech-land-speed-race-car-design/
33IMP
Well-Known Member
Next trip back to the track, I would do the exact same a to b test. Hood and filters in place, then a back to back with just the scoop, see if that 4mph reappears. If it does then you have a confirmed starting point for more testing. FUN!
I actually graduated with an aviation degree, and yes, there Is some minimal forward thrust, BUT that's not what slows/stops the plane. It's the "trash can lids" as we called them. It's the same as the plane momentum having to push big solid discs through the air.
In the sim we used to go full beta prop setting (to see if we would actually get enough reverse thrust to move backwards. It was just enough to get the slightest movement....and then...the engines would blow
famous bob
mopar misfit
I actually graduated with an aviation degree, and yes, there Is some minimal forward thrust, BUT that's not what slows/stops the plane. It's the "trash can lids" as we called them. It's the same as the plane momentum having to push big solid discs through the air.
In the sim we used to go full beta prop setting (to see if we would actually get enough reverse thrust to move backwards. It was just enough to get the slightest movement....and then...the engines would blow
Back in the day , I had 3 pins on each side and a carb stud that went thru the hood for 9th hood pin , guess which did the most good on a race weight fiberglass hood / was a cheap one , fiberglass has probly come a long way sinse then .
This is the style lid I was thinking off. IDK if there is room for a stack.
This is really interesting.
i looked at the incrementals and from the 60 ft clock forward there was gains like you would expect from ram air virsus disturbed, turbulant air. Very small gain 60 to 330, 330 to 660 more gain, over double from 660 to 1320.
I’m curious if this would make a difference
K&N Flow Control Air Cleaners 61-6000
Unfortunately, when your experimenting with parts made for a dominator, expenses add up quickly. I think some of it’s a combination of letting air pressure off the front and more high pressure air hitting the scoop opening. But no doubt getting the air filter out of the way of the incoming air is helping, too.
K&N Flow Control Air Cleaners 61-6000
Unfortunately, when your experimenting with parts made for a dominator, expenses add up quickly. I think some of it’s a combination of letting air pressure off the front and more high pressure air hitting the scoop opening. But no doubt getting the air filter out of the way of the incoming air is helping, too.
All combos are on the table for testing. I do log afrs with an RPM DATA LOGGER. The afrs on the run without hood show a definately leaner run. I will overlay a couple of runs and see if i can learn from that.
pishta
I know I'm right....
@Johnny Mac , check this guy out. Short stop and all! I wonder if it went 'beep beep beep' when backing up? Ha
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