DIY Ram air questions

[clunk]

I am wanting to build a Ram Air intake for my 1990, but in my 1990 XJ I have a Thermostatic Air Cleaner on the front "rectangle" off the stock airbox. I'm wanting to remove this entire "rectangle" and replace it with a piece around twice the size as well as enlarge the opening beside the headlight to allow max. airflow, as per this website: http://jeep4.0performance.4mg.com/ramair.html

Can I just remove the T.A.C. completely? What should I do with the hose for hot air that comes from the exhaust manifold/heat stove passage? In the website, it doesn't mention the T.A.C, but from what I gather it pulls hot air from the manifold to speed in warmup..as well as really restricting the airflow to the stock airbox!

[Gerr]

id say just unhook and let it be the way it is from there, well thats what I did :)

[clunk]

ok, thanks. No problems with the engine warming up quickly?
I also read this website, pretty interesting:
http://www.omninerd.com/articles/Improve_MPG_The_Factors_Affecting_Fuel_Efficiency

[Gerr]

engine warming up is mostly by the thermostat so I havent noticed a differnce

[xjh3]

I did something almost identical to this (if I'm reading your description correctly.) Mine's a 97 so I didn't have the TAC or whatever. I made a whole new box that almost completely seals to the hood, which was a real b*tch. Then I cut out the little plastic cover in front of the stock airbox and then cut out and made it about twice as big of an opening. When I get a chance, I'll post some pics.

[DirtyMJ]

With EFI it's really hard to understand why they used a stovebox/alternate air system. It simply doesn't work with EFI, especially MPFI with the injector only an inch from the intake valve. The reason they had it on carbed engines was it'd prevent the carb from icing and limit fuel drop-out.

I think it's another stupid jeep thing that belongs in the trash. You'll notice no problems with warnup without it.

[clunk]

So I just "built" my Ram air intake--I used a 4" to 3" PVC pipe coupler, enlarged the stock airbox opening and fit it in there. I then cut and bashed some sheet metal from behind the drivers side light to allow more air flow. I made a micky-mouse heat shield to prevent any air from the engine back from getting in there. I'll make a more permanent setup later, for now I'm just experimenting a bit. It sure doesn't look too pretty, but it should have increased airflow considerably.

[Dr. Dyno]

I am wanting to build a Ram Air intake for my 1990, but in my 1990 XJ I have a Thermostatic Air Cleaner on the front "rectangle" off the stock airbox. I'm wanting to remove this entire "rectangle" and replace it with a piece around twice the size as well as enlarge the opening beside the headlight to allow max. airflow, as per this website: http://jeep4.0performance.4mg.com/ramair.html

That article looks vaguely familiar to me. ;)

[wolfpackjeeper]

1) ram air does not work the way most people think, talk to a mechanical or fluid engineer, they will tell you why. ram air does not equal "cheep forced induction" mainly what it does is bring colder air into the throttle body. There is a writeup on the camaro sight I am a member of, I will try to find

2) the stock airbox is the way it is to keep water out. it is really hard to hydrlock a motor with the stock airbox, and really easy to do it with an open element filter. Ive done it....

-If by ram air, you mean "colder air charge, and easier access for the manifold to draw air" then you would be correct.

-if by ram air your mean "effect by which the air is forced into the manifold at a higher pressure, increasing the air charge and adding horsepower" you are wrong. Fluid dynamics doesn't work that way

[old_man]

The thermostatic air intake is there to prevent "carb" icing. In areas of low humidity that is not a problem, like here in Colorado, but back east it is a major issue.

[1bolt]

Old_man I think his point was that there's no carb to ice up, his fuel injected Renix air cleaner housing has a heat riser off the exhaust manifold. I never could figure out why they did this except that it was the 80's and they were still thinking carburetors.

The same sort of lax engineering that made the Carter BBD and late CJ/ early YJ emission system. With pulse air "resonant" tubes, primitive computer controlled stepper motor carb, EGR into a wet intake manifold and all sorts of insanely ludicrous bafoonery... :twak: Not coincidentally the same bunch that were asleep at the wheel while Toyota and Datsun were stealing American car buyers "heart and minds".

[1bolt]

BTW if you're throwing out your factory air box and putting a cone filter in the engine bay then hand your self a :dunce: cap :)

Underhood temps are as much as 60* over ambient on my stroker. That's roughly 5hp lost... (at each 10* hotter = 1% horse power loss) on a 4.0 if your cone filter is good enough you might be breaking even.

If your cone filter sucks and it's just attached to that lumpy soft flexible (turbulent) factory rubber air tube you're probably losing power.BTW that's an average, taken at sustained highway speed.

[clunk]

Although I don't have any real dyno tests to backup the results, I can really feel a difference in throttle response driving around. No comment on mileage since I have not run it enough to get accurate numbers to compare to my usual driving. The jeep *feels* like it's breathing better, no longer does it feel like it's having a hard time pulling air in, plus I don't mind the increased noise when I get onto the throttle :). Now, I'll have to do something about the factory cat sometime down the road..

[old_man]

Old_man I think his point was that there's no carb to ice up, his fuel injected Renix air cleaner housing has a heat riser off the exhaust manifold. I never could figure out why they did this except that it was the 80's and they were still thinking carburetors.

The same sort of lax engineering that made the Carter BBD and late CJ/ early YJ emission system. With pulse air "resonant" tubes, primitive computer controlled stepper motor carb, EGR into a wet intake manifold and all sorts of insanely ludicrous bafoonery... :twak: Not coincidentally the same bunch that were asleep at the wheel while Toyota and Datsun were stealing American car buyers "heart and minds".

If you notice, I put carb in quotes for a reason:doh:. Intake icing is a problem on carbs as well as TB's. As the air goes past the venturi/throttle plate, it speeds up. Boyles Law comes into play and the air rapidly cools. Any moisture in the air condenses and can cause a layer of ice.