Just wondering opinions here. I am getting ready to do a ram air setup on my 12a with the RB intake and Holley carb. I have a buddy who is going to make the carb cover / air cleaner setup from aluminum. The plan is to cut the hood and put an air scoop I found on ebay that is inset so the hood line stays the same. The scoop will be directly in front of the carb with no restriction for air flow into it. The aluminum airbox will be airtight so the only air the carb will get will be outside air. We are also gonna try making the aluminum airbox the shape of the rotor. Has anyone done this with success? I would like some opinions on this in hopes that if I have not thought of something one of you all will. Will post pics once it is completed as well. Thanks.
Jim

 

ive thought about it, but the gruling work required to make it lightly press against the rubber seal on the hood with out being to much and miss aligning the hood or to little and not sealing completly. seams hard but worth it, its like a cold air intake +1

 

Easier to build it than it is to build it right. Usually you will just end up creating so much turbulence that you will cause more issues in the end...

Are you planning on attending the Lansing meet May 13th?

 

I thought that the hood reinforcement was there, so you cannot cut...???

You'd be better off to mount the scoop directly to the air box and let it protrude though an opening in the hood 'a la shaker' style.

 

I did a "sort-of" ram air setup with my old Yaw carb.Cant say it helped much with power,but I succesfully iced over my carb almost every time I hit the freeway.Unfortunately,its all too easy to ice a carb solid since the fuel is being distributed and evaporated well before the intake ports,in a reletively cool part of the engine.The evaporating fuel furthur cools the intake and carb to the point where the venturis can freeze up,even if the outside air is well above freezing.You need a certain amount of heat present to properly vaporize fuel.Hence,fuel injectors that fire onto hot intake valves,or in our case,a coolant passage that heats the passages in the intake manifold.

Also,if you do actually achieve some postive ram effect into the carb,it will change the air/fuel ratio,possibly for the worse.The older,early 90's sportbikes dove into the "ram-air with carbs" scene with the ZX-11.The cure for lean out was to have a pitot tube at the entrance to the ram air tunnel that lead to the float chambers.As the air in the intake tract pressurized,the tube would transmit the same pressure into the float chamber.That way,the pressures in the intake and float chamber were equalized and the mixture didnt go all to hell.

 

Dosnt RamAir only work when you get up to like 140MPH

 

This is exactly why I posted this thread. Thank you. I did not want to go cutting up a hood ( have 3 ) and setting this up to be extremely unhappy with the outcome. I was not sure how the air/fuel mix would be affected but I knew that there would be some changes. Icing the carb does not sound like an outcome I want to deal with. What about just putting the vent in for colder air but not creating an airbox ?

 

What time and where in Lansing? would love to get together with the fellow 7 owners. pm with directions and time and maybe we could head that way together since I have to go down M-6 to get there.

 

Cooler air will make more power since its denser,you just have to be prepared to disconnect it from the intake when the outside temps dip down.You just have to leave enough heat to properly atomize the fuel as it exits the carb.I had my water passage blocked off in the intake manifold,Im sure it didnt help things.

My "ram-air" consisted of aluminum dryer ducting routed from the right turn signal hole,directly to the stock airbox snorkle.In the winter and cooler times,I would just pull the duct off the snorkle and let the engine breathe the under hood air.
Icing over sucks.....your going along fine,and you realize your pushing harded and harder to maintain speed.Then the secondaries come online and the power is back.....until they freeze too.Then you come to a dead stop with no idle and no way to restart until the carb thaws.
I would see icing and loss of idle after only 1.5 miles on the freeway.It was exactly that distance to my old work and I drove it every morning.Took me about a week to finally figure out why my car would stall when I exited the freeway.The other times it froze up solid were during ski trips up the Sierras.

 

'ram air' is a waste of time. Even if you go straight into the intake from the front (no bends or anything) it still has to make a 90 degree turn into the carb - so it's not 'ramming' anything.

Cold, dense air is the goal, and if you can pulse the air into the ports through a dynamic effect chamber, so much the better. If anything, a DEI with its own cooled waterjacket would be the bee's knees.

 

ooooooh you can make such cheap set up like this, the car i drag race has such a cheap set up on it. ill do it to my car once its on the road

 

I have heard enough to make the decision to not build the airbox and "ram" air into the carb. The 7 runs great now and it seems like a ton of effort for a very little increase of noticable power. I instead will use the two air scoop insets to bring colder air into the engine bay in an effort for cooler engine bay temps. Plus I think the hood will look great. The scoops are very similiar to the older datsun air scoops. Someone mentioned earlier that the hood supports are in the way. If you look closely there are two perfect areas to cut without affecting the the original design of the hood.

 

I'm in the process of building a TII hood that will bring a lot of cool air into the engine bay, thought about the ram air effect also but decided against it for the same reason. Hell, my Mikuni has coolant lines to stop the freezing but its still a very small gain.

 

I was thinking of the TII style as well but I really like the hood line without any protrusions. Nice clean look. I spent about a year looking for the right air scoops that inset into the hood and finally found two. Actually were built for a lear jet but will fit perfect with little work for a smooth look.

 

Ram air isn't really ramming air into the ports, they use it to pressurize the air box that sits on to of the carb.

 

Possibly a Cold Air Intake which taps into the air at the base of the windshield would be a better benefit/cost ratio.
By this I mean the grill area where the windshield wiper linkage is located.
This area tends to be a high pressure area and you could just redirect the air cleaner snorkle to the rear and connect with a suitable clothes dryer duct hose.
All that should be needed is about a 3 inch hole and a few clamps.
The main benefit will be cooler air not much real "ram" effect.
There should not be any problem with lean mixture since most float bowl vents are in the same area as the venturies.

 

I think a better approach would be to install some vents to extract the hot air.

 

Still learning the whole concept of air in or vent out. Would bringing cool air in not do the same as exhausting hot air out. Reducing engine bay temps. What is a more efficient way. Is this because of drag ( areodynamics ) created by vents facing forward.

 

I like the idea of a cold air intake, if done properly. But like I said, properly setting up a ram air intake is not easily done.

Personally, I think a higher priority would be to remove the hot air from under the hood. I would like to do a turbo scoop, or maybe the Z car cutouts, something along those lines.

 

I too like the idea of cold air intake. I had a setup on my stock carb similiar to many I have seen on here. Good ol' dryer hose from the radiator enclosure fitted into the air cleaner. Noticable difference. The ram air idea is not bad if I could get a shutter valve incorporated into it to reduce air speed into the carb at higher speeds. The faster you go, the faster the air speed into the carb. This would obviuosly affect the air/fuel mix. If somehow I could regulate it too maintain the same amount of air speed into the carb no matter the speed of the 7 it would work nicely. I do like the idea of just cold air into the carb and using a sort of cowl induction to create a constant pressure with a sealed airbox. That kind of setup would have a more steady air flow I think. I am currently in the first step..thinking ! I do know this, I only want fresh cold air going into the carb. Kentetsu, we should get together and maybe you will have an idea I have not thought of yet.

 

I had my airbox setup the same way as Steve did and I also had carb icing problems.

I think that overall the cold-air effect is ultra minimal at best. A better option would be to get a better flowing airbox, like the RB unit, and forget about cold air induction altogether.

 

I've been thinking about this also, I have been pondering some ideas to streamline the airflow out of the exhaust area also, like a heat shield which flows the hot air under the firewall or out of some side fender vents.

Its just an idea now but getting heat away from the engine would appear to be the bigger advantage for longevity and consistency.

 

I have the RB unit and it does flow much better than the stock. However, even with the heat shield over the header I am still drawing air from a warmer engine bay versus fresh outside air. That is my thinking as far as cold air into the engine bay. The cooler dense air does create some difference, even if a marginal difference, as far as fuel / air mix. The horsepower gain is not what is driving my thoughts cuz that is very minimal if any. Isn't it true that colder denser air will reduce fuel consumption slightly or create a more fuel efficient mixture ? Either way, a simpe solution for colder engine bay temps wouldn't hurt anything.