Ram-air scoops???

[seanyb505]

On my 97 there was a little plastic panel in front of the intake and behind the headlight that I took out. The light it still there, but I can take it out at the strip pretty easily. I think on another forum someone was talking about taking one of the turn signals out and routing air straigt to the intake from there. I would see if you rig something up that way. As far as the plastic, try the getting the heating duct on a newer (I know mine has one) XJ that routes air to the back seat under the console. Its probly not exactly what youre looking for, but it might work with some modification. Food for thought.

 

[Darky]

What about a small hood scoop to put over the airbox area and then route a hose straight up to it? It may look a little odd, what with a scoop sitting in the corner of your hood, but I've always looked at mods done purely for performance as being cool-looking if not good looking...
Plus that'd keep it a little higher for the people who fear sucking water (which I have filled my engine once and I also avoid lakes. This was on a flooded dirt road with hidden ruts that were a lot deeper than I thought when I tried to make it across) and get you cooler air since it'd be coming from outside the engine compartment

 

[BBeach]

What about a small hood scoop to put over the airbox area and then route a hose straight up to it? It may look a little odd, what with a scoop sitting in the corner of your hood, but I've always looked at mods done purely for performance as being cool-looking if not good looking...
Plus that'd keep it a little higher for the people who fear sucking water (which I have filled my engine once and I also avoid lakes. This was on a flooded dirt road with hidden ruts that were a lot deeper than I thought when I tried to make it across) and get you cooler air since it'd be coming from outside the engine compartment

Thatd deff be a little odd. As far as sucking in water, whenever I hit a large puddle the water goes right over my hood...."sealed" inside the engine bay is prolly the best idea.

 

[badron]

Air scoops need to be on the front 1/3 or less of the hood on most cars/trucks in order to see ANY ram effect. Else most of the air just passes over the scoops at any speed that would supply a ram effect. OK if you go up 6 to 10 inches over the hood you will get back into clean air but Ohio don't like your vision block that much as well as many other states.
Also at speeds the stock filter stays cool anyway. Offing is a different story. But hood vents will help here as well as keep the engine compartment cooler in general.
Then there is (cow induction=CI). But CI hood mounted scoops need to be within 2 inches or less of the windshield to receive any real ram effect or else it just a backward scoop. Also any were on the rad support will give just about the same ram as the hood. It does NOT need to be visible.
(IMO) I think you just want a scoop on your hood, cool. So pick a cool looking spot and just do it.

 

[wolfpackjeeper]

Air scoops need to be on the front 1/3 or less of the hood on most cars/trucks in order to see ANY ram effect. Else most of the air just passes over the scoops at any speed that would supply a ram effect. OK if you go up 6 to 10 inches over the hood you will get back into clean air but Ohio don't like your vision block that much as well as many other states.
Also at speeds the stock filter stays cool anyway. Offing is a different story. But hood vents will help here as well as keep the engine compartment cooler in general.
Then there is (cow induction=CI). But CI hood mounted scoops need to be within 2 inches or less of the windshield to receive any real ram effect or else it just a backward scoop. Also any were on the rad support will give just about the same ram as the hood. It does NOT need to be visible.
(IMO) I think you just want a scoop on your hood, cool. So pick a cool looking spot and just do it.

Ram effect does not exist at speeds of less than 500mph. Air can safely be assumed to be incompressible at low speeds. It is one of the basic assumptions of subsonic aircraft design. Hood scoops will route cold air to the engine quicker, but the performance boost will come from the colder air not from any "ram air" effect.

 

[BBeach]

Ram effect does not exist at speeds of less than 500mph. Air can safely be assumed to be incompressible at low speeds. It is one of the basic assumptions of subsonic aircraft design. Hood scoops will route cold air to the engine quicker, but the performance boost will come from the colder air not from any "ram air" effect.

What he said ^^
Ive always used mach .3 which is 200-250mph or so. Obviously not happenin in an xj. One of my teachers always used to say "air isnt going to compress unless it doesnt hear it coming".

 

[badron]

OK change all ram to clean air.

 

[Skits]

Ram effect does not exist at speeds of less than 500mph. Air can safely be assumed to be incompressible at low speeds. It is one of the basic assumptions of subsonic aircraft design. Hood scoops will route cold air to the engine quicker, but the performance boost will come from the colder air not from any "ram air" effect.

Old post...but have a counterpoint.

All modern sportbikes see a pretty substantial gain in speed on straights with the ram-air ducts on the nose. Its a proven and repeatable fact, and it does pressurize the airbox on them...carbed bikes even have tubes running to the float bowls to the airbox in order to even the pressure differential between pressurized airbox and atmospheric of the bowls.

So ram air does have a significant effect...you may not be getting 14lbs of boost, but it does increase performance.

 

[wolfpackjeeper]

if ram air could work then bernoulii's principal would not. One or the other. The NA intake system for an automobile can be pretty closely compared to the water glass setup used to demonstrate the principle.

And everything sees a substantial gain in speed on the straits, it is more a matter of control than one of ram-air. You might see a few mm of Hg increase, but not enough to add HP. You go faster on the straits because they are the straits, you slow down in the curves to maintain control

 

[Skits]

What does Bernoulli's Principal have to do with forced air intake? Works lovely for carb venturies, but has no relevance here. The air is not increasing in speed, only in pressure.


Sport Rider magazine did a test on several different bikes ( http://www.sportrider.com/tech/146_9910_ram/index.html ) and found around 25-30 millibars of pressure do solely to the ram air, and a 5-7 hp gain. The bike they tested that didn't have ram air had 27 millibar vacuum in the air box. So that is about a 55 millibar or 1 psi improvement for the ram air. A 5hp gain on a 100hp bike is substantial and real, and has nothing to do with the effect of cooler air, since they are always drawing air from the nose of the bike at ambient regardless of speed.



You need to let every Formula 1, MotoGP, and NHRA team know that those big scoops are doing them no good whatsoever. They're going to be really pissed they spent all that cash on wind tunnel testing....

 

[wolfpackjeeper]

except that they drag air into the motor in a cooler more efficient manner. And were you not just talking about a carbed bike setup in the post above? Then you bring up F1, and NHRA stuff that we have already established earlier operate on the bare edge of the speeds at which you can compress air, and their gains are still marginal.

None of which operates even close to the range you will be running your jeep at. The whole topic is irrevelant to the jeep situation

 

[Skits]

My mention of the carbed bike was simply to illustrate the point that there is enough of a pressure differential to require pressurized float bowls in order to maintain fuel flow (because ram air pressure in the intake tract exceeds the ability of the previously improperly referenced Bernoulli Principal to draw fuel out of the carb circuits...). I know you're a youngin and carbs may be foreign to you, but trust me.

F1 and NHRA still operate well below the point of 500mph that you mentioned...in the case of F1, 200mph max. So even at 40% of your theoretical no-gain barrier, there is enough potential horsepower that they spend small fortunes optimizing it. Cut that number in half to 100mph, and there is still a gain, with the numbers increasing exponentially from there. I personally know of cases where guys had to re-gear a motorcycle after adding homebrew ram air because they were bouncing off the rev limiter before the end of the straight due to gains in top end power. I don't remember seeing vortices or any other evidence of near-supersonic speed...but I was probably distracted by umbrella girls at the time.

In the case of aerospace applications like turbine engines, I can see how the 500mph point could be true. You'll have to forgive my ignorance on this point, because my last aeronautics class was in about 1989, but it seems reasonable that any pressurizing effect to a turbine could be largely ignored. A ramjet or scramjet is obviously not going to operate below that point, and if I'm thinking right both require true supersonic air. I have no doubt that you're much better educated in this area than I...I'm just a dumb blue collar guy after all.

Are you likely to gain substantial HP in a Jeep going 3mph at Moab? Nope. Would I go to the effort of designing and building a ram-air system for a 175hp square-assed SUV? Nope. Did I once suggest that you were going to see a large HP increase? Nope. But relevence to a Jeep is not and never was my point. What I've said is absolutely correct, and is accepted as fact by engineers everywhere.