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THOR Cowl Intake Thoughts


NAXJA Forum User
I just installed my Thor cowl intake last night on my 96 XJ. It was an easy enough install and I have a few thoughts after driving it last night and to work this morning.


I had read almost every review on these prior to buying and almost all said that its noisy for the first minute or two of startup and then quiets down, which is true. But every time I give it throttle it sounds like someone is sucking through a giant straw behind the glove box, and also a bit of a whistle at times! Yay! The only time it isn't sucking loudly is when coasting, at idle, and wide open throttle - which makes the 4.0 sound beastly, but is also really loud itself. My wife may never ride with me in this Jeep again, she didn't like how loud the Jeep was before this intake was installed.


This Jeep has a 195 t-stat and always runs a hair under 210 in everyday driving conditions. I am now closer to 200 post cold air intake. Not sure how it could affect it that much but it is. I watch my gauges like a hawk and immediately noticed this. Nice surprise I guess?

The reason I installed this was to free up space for a secondary battery but I don't know if I'll ever get past the noise. Any suggestions on what could be done to reduce the sucking sound or do I just accept it or remove it? I read something on another post about applying some kind of sound deadener inside the cowl?
Before spending money on sound attenuation products it is worth buying a smartphone app that can do frequency analysis (spectrum analyzer) particularly Fast Fourier Transforms (FFT). This will enable you to see visually in a graph what frequencies you have to deal with. Then with each product you try, you will see how effective or ineffective they are. For human's, frequencies in the range 500Hz to 5Khz are going to be what you are interested in.

There are a number of things you can try, heavy rubber mat, inverted cones, bonding triangulated frameworks to panels to increase rigidity and reduce the individual resonant panel areas. The fact is that if you have the open end of an engine intake pointing at your ears, pointing it in another direction would be a better idea.

Noise cancelling technology might be an option but it isn't cheap.
I have a Thor intake, but I have not installed it. There was a similar thread some months back. I think the tube in the Thor is steel. As Vince leads to, this could be channeling sound to your firewall. So, a few thoughts. First, thy and replace the tube with a PVC pipe and some rubber 90 degree bends. Another, with the sound deadening material at the firewall, is to put a plastic shield between the air filter and the firewall. I wonder if any of the ones running a Spectra or K&N setup has these issues. I think both of them have a plastic tube from the TB to the firewall.
No didn't insulate the pipe. I drove it around in the heat of the day today with temps in the 80's with similar results and a bit lower run temp than normal. Could it be that there is just better air flow in the engine bay without the stock airbox? I noticed I was starting to get used to the noise already which is good I guess.

Yes it is a steel pipe so maybe the PVC and rubber elbows will help, as well as placing some rubber or plastic in the back of the cowl like you guys suggest.
I just bought one of these today............ Interesting timing on this thread to say the least.

I think we will have to live with most of the noise?
Sound will travel through open seams, or cavities easily. You have to remember that the fresh air setting on our HVAC systems opens up into the cowl.

When I get mine I will look to see what can be done too? But I don't think much can be done???
I am putting a second battery on the drivers side, and I have to mount my PSC power steering res. over there too.
Report back after you install yours! From the posts above and everything I've read it doesn't seem like there is an easy solution to the noise. It is what it is basically. Here are my pros and cons so far.


Frees up a lot of space in the engine bay.
Gives a snorkel type effect by raising air intake.
Hopefully added a little horsepower.
Simple install.
Sounds like a monster at WOT- also a bit of a con to me.
Engine running cooler? I'm highly skeptical of this but my temp gauge is slightly lower since install.


Sounds like Darth Vader is in my glove box.
Whistles at times too.
I've had a Spectre intake for several years and can confirm pretty much everything you've given for pros/cons. Maybe with the exception of reducing coolant temps.

I've really been rethinking the intake recently because of the noise. For me, its mostly the whistle at certain throttle body valve positions. Also, I'm skeptical that everything is sealed up properly downstream of the filter, and that the filter itself is even big enough.

I feel like there's no way to get away from the noise with a cowl intake setup. Its pulling a ton of air right next to a tube that goes directly into the passenger cabin. I've thought about putting a 90° turn up and out the top of the cowl to make a H1 style mushroom top snorkel. Hauk Offroad makes kits like that, just not for XJ's.

Love the freed up engine space, increased intake height, and performance gains. Don't like the noise, and the potential for leaks downstream of the filter.
Another thing I've been 'working' on, is adapting the 'Resonator' or carb hat from the WJ. Also, looking at other options from different vehicles. The WJ Resonator sit a lot higher. I took off at least 1/4 from the opening that sits on the TB. There is a rubber seal and clamp there too. I am going to try and take about 1/8th more. Still, there is a round 1/2 tube protrusion that is on top of it. It contacts the XJ's hood. I plan to cut that down and a plate to cover the opening made. Still, I'd have to adapt the oval intake opening to some type of filter arrangement.
I have seen some more traditional 'carb hats' at the PnPs. I think the one is from a Ford SUV or truck. The tube to the TB is a bit big for the XJ's TB. Still, thinking of adapting. Just throwing this out there.
I installed one earlier this year and it definitely makes some noise. It would be annoying if the Jeep was my daily for sure.
One thing I was wondering about today is,,,,,,
When my HVAC is on "Vent" will the airflow be reduced with the cowl intake???

I guess I will find out soon enough though.
I run the Thor and have contemplated some dynomat or similar inside the cowl where it's reachable.... honestly some rubberized undercoat may do a little... the sucking noise will be there regardless though....
My jeep is a beater, so I don't really mind... when the windows are down and I'm running 40 I can't hear the intake due to wind and tire noise... but a daily or even regularly driven xj does not need this intake imo

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I have been running the THOR intake for around 3 years on my rig, and you get use to the sound. I don't even notice it anymore. When we had my XJ on the dyno this spring while tuning my 4.7L stroker we did it with the THOR connected and just with the open throttle body. The THOR intake actually added 5 HP of performance over a completely open throttle body. We looked at the data and the gain was because of the cooler air it was drawing into the engine vs the open throttle body, even with the hood up. I expect the gains are even more when the hood is down and the restrictive nature of a stock airbox. Based strictly on performance, there is a benefit that the intake provides in being able to continually pull in larger volumes of cooler air. I guess you have to choose the performance trade off vs. the sound.
When we had my XJ on the dyno this spring while tuning my 4.7L stroker we did it with the THOR connected and just with the open throttle body. The THOR intake actually added 5 HP of performance over a completely open throttle body.

HAHA I have 4 angry squirrels under the hood, and I'll take what ever I can in that department!
You know it's bad when VW busses pass you up on the HWY.
Past experience with other cars, I only put a metal cone type filter on a car (made a short ram but still using oem plastic/rubber tubing) and it made the loud intake sucking noise. If there is a filter but all rubber/plastic this may cut down the noise. I know they make it just don't know any brands off the my head its been years since I was in that tuner scene.
A bit late to the thread but like others, I noticed a fair bit of noise with my cowl intake. I thought I'd add share my latest experiment.

I did a DIY cowl intake years ago that worked much the same was as the THOR. It was loud and whistled under hard acceleration.

I've had my Jeep for 13 years now, and having realized that I never submerge the hood under water I figured I don't really NEED a cowl intake. One thing I do need though, is space for a second battery. So what I'm trying now is an air-cleaner ( used in carb applications ). I know all about heat-soak so there is that to think about. Hood vents may help if I find it a problem.

Anyway, here is a pic of my recent "upgrade".
- upgraded intake manifold
- upgraded throttle body to 68mm
- swapped to an Edlebrock air-cleaner (easy DIY fabrication project).

I haven't had it out on the road yet but I expect it to be much quieter.

It would be good data to see what your intake Temps are with that setup...

I want to see a setup with the filter being outside the cowl on top. Similar to a hummer.... similar to the Thor but in theory no noise

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It would be good data to see what your intake Temps are with that setup...

I want to see a setup with the filter being outside the cowl on top. Similar to a hummer.... similar to the Thor but in theory no noise

Sent from my SM-A426U using Tapatalk

Yeah the intake temps will be the thing to watch when I get this back on the road in a couple weeks. A few thoughts on that:
1) I'm leaving the hole in the cowl as it essentially acts as an engine bay vent. The cowl vents to the outside so hopefully it will help keep engine bay temps down
2) I will consider hood vents if I have to ( and only if I have to as a last resort )
3) it's a trade off between what should be a better flowing intake vs air temp. I don't imagine the cowl intakes with all their bends and inline cone filters flow all that well compared to a filter sitting directly on top of the throttle body. EngineMasters did a dyno comparison of 19 different air filters and I found it eye opening: https://www.dailymotion.com/video/x693421