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Old 09-10-2016, 04:02 PM
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Air intakes?

So I was wondering if those who have cold air intakes would recommend having one and what you got from it? Brands also.

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Old 09-12-2016, 01:03 PM   #2
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Personally I think cold air intakes are a gimmick. I don't know about FI, but on a carbed motor the intake is already cold air intake if the rectangular tube is connected from the grill panel to the air cleaner.
The best thing you can do for intake is make sure you have a clean air filter.

Other posters with FI should chime in. I'm curious about their results.

Good Luck, L.M.

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Old 09-12-2016, 02:35 PM   #3
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They are kind of a gimmick. Your HP gain is going to be really small at best. We're talking less than 5%. That said, if your OEM box is a piece of crap like mine was, and all the latches magically fell off, then a new intake system is probably better than trying to replace the OEM box.

I put mine together using some off the shelf plastic pipe and rubber clamps from Autozone (specter?) and a K&N cone filter that I already had. I also made up a splash guard from some 18 gauge sheet stock I had on had. This setup allowed me to raise the air inlet over the fender, so there's a bonus. I put a vent in the hood just over the filter location to try to get more "cold air" to the inlet. I doubt it makes a significant gain in power, but it sounds cooler at WOT, and the filter can be cleaned.

I don't think I've taken any pictures of it. If I think of it later I'll post back.
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Old 09-12-2016, 03:31 PM   #4
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The 4.0 will not see a bit of performance increase through a new intake. It's already sucking more air than it can use. If your looking for more power from the 4.0, you can either stroke it or replace it, any other mods aren't going to do much of anything except lighten your wallet.
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Old 09-13-2016, 06:53 AM   #5
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That's how my set up turned out. The "box" is mounted to the inner fender in pre-existing holes. I had some 16 gauge 1.5" wide steel laying around, so I bent a couple quick supports and tacked them in place. Then you can either through bolt them or tap them.
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Old 09-14-2016, 12:20 PM   #6
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Kind of a hot air intake don't ya think?
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Old 09-14-2016, 02:37 PM   #7
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No. The stock box pulls air from the bottom of the box right next to the power steering pump.

This setup has a vent in the hood right over it. So it's not really drawing anything hotter than it was.
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Old 09-18-2016, 06:37 PM   #8
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Forgive me, but I did first read multitudinous posts. I would like to know if my 2001 Jeep Wrangler with a 2.5 would benefit from a cold air intake. I am not necessarily looking to make it run faster, but more efficiently. The Jeep was born, so to speak, in Arizona, and I bought it Wyoming. I was looking for just a little more performance while it's being driven in CT. Will it help? I also looked into a Jet chip, but no one seems to think that's worth it.
Many thanks,
Tom
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Old 09-18-2016, 07:56 PM   #9
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I installed a vacuum gauge on my Jeep so I can monitor the vacuum as I drive it to learn more about it.

From how I understand it, you want to maintain vacuum in the air intake even at wide open throttle. Now, when I stomp on it, and the RPMs are high, the gauge reads zero to the point where I assume there would be pressure.

It seems as though when I keep the throttle as open as I can while still maintaining a few inches of vacuum, the Jeep has better pick-up. By expanding the air intake, there is less vacuum. This is the same concept as straws... You can get a regular straw with a small diameter, a straw from McD's, or a PVC pipe. The regular straw is too restrictive, the PVC pipe cannot get enough vacuum, and the McD's is just right.

Stock air intakes are just right, they restrict the air flow just enough for good vacuum. Now when your engine isn't stock, that's when you upgrade the air intake. Not having the right intake for the right engine will trip the TPS and MAP sensors, thus having an inefficient timing advance and fuel injection pulse. Basically making it run lean...

Put a vacuum leak in the engine, just unplug a vacuum line while it's running. See how crappy it runs? That's an exaggeration of low engine vacuum. In terms of air "temperature," I think the factory intake is cooler than anything in the engine bay.
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Old 09-19-2016, 09:27 AM   #10
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None of that made any sense what so ever. Manifold vacuum is created by the pistons during the intake stroke while the throttle is partially closed. When you open the throttle, vacuum drops because the throttle blade is letting the atmosphere push more air in. That's why the engine speeds up, more air and fuel.

When there is restriction at the intake (before the throttle), air moves slower into the engine. The restriction causes more drag on the rotating assembly. This is a parasitic power loss, because it takes power from the engine as it pulls against the vacuum. If the vacuum isn't as strong, it takes less energy to pull against it.

When the engine is operating normally, there is an expected MAP to whatever throttle position. If you pull a manifold hose, you're letting in more air AFTER the throttle. The engine controller sees an idle position at the throttle, but a much lower MAP value and can't adapt to it. If you let more air into the engine by reducing the restriction BEFORE the throttle, the engine controller can learn this change(which is really small, hence the negligible power gains) via the MAP sensor. That's why you can take your fuel injected Wrangler in the desert, then drive it later that day at 12,000 feet on a mountain and it still runs more or less just fine. Even though the air is much thinner at 12,000 feet, the MAP sensor is there so that the engine controller can detect the change in atmosphere and adjust the fuel trim. The engine will constantly re-learn the throttle position, fuel, MAP, etc to maintain optimal running conditions. These are called adaptives.

In addition to all of that, fuel injected vehicles with a mechanical throttle have Idle Air Control. The IAC's job is to increase or decrease air flow independent of the throttle blade at idle. This why the idle is the same at 1000 feet or 10,000 of altitude. And yes, the IAC operation will affect MAP.

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