I always wondered what effect there would be if the resonance chambers protruding from the intake were eliminated. In short, under normal driving there is no difference in sound. A wider throttle openings, the sound is similar to stock but louder and meaner! It's not deafening, but noticeably louder and harder edged. I love it.

I simply used some expanding polyurethane foam to fill the voids. It's messy but perfection is not necessary. Check out the pics. A crazy mod like this required a little liquid motivation. Once buzzed, everything became clear!

Mike
2004 XJR

Note: I have always had an open element air filter which lets more sound out than stock. With a stock airbox the sound improvement may not be as noticeable (or maybe it will be more noticeable).

 

Hi Mike:P !

A very interesting and creative idea! Can you tell any difference in torque?

My understanding is that Jaguar's stated goal for the use of the Helmholtz resonators was to control noise as part of its overall NVH strategy. But from what I've read about resonating chambers in air intakes, they are often designed to increase the volumetric efficiency and torque of normally aspirated engines. However, they reportedly have no effect on the performance of a supercharged engine, only the noise. Can you give us any additional thoughts on any perceptible difference in performance, or is the only difference the increased noise?

Thanks! Don

 

There is a less-ghetto way to achieve this result, and we know that they are worth around 10HP at the wheels as well as freeing up some of the blower whine...

https://www.jaguarforums.com/forum/x...ailable-83959/

 

I did a bit of studying of Helmholtz resonators in relation to engine intakes a few years back. I can tell you that the placement of these resonator chambers (tubes actually) are strictly for noise by virtue of the fact that they are upstream of the throttle and, therefore, farther from the "action" than, for example, the intake runners, plenum, cross-over tubes, etc. I am pretty sure there is essentially no performance boost from my mod except, perhaps, if I inadvertently smoothed the intake flow and reduced pressure drop ahead of the supercharger.

In one of the pics you can see that I had a vacuum gauge stuck to the intake tube. Its original purpose was to tell you if your air filter was getting plugged. I installed the gauge downstream of the filter (my custom gauze filter surrounded by a foam pre-filter) and airflow meter and snorkel tube. Even with the total restriction of the three, the gauge never moved past the "medium dirty" mark. The lack of restriction makes me think that the rest of the intake tube was probably only a limited source of pressure drop.

Regarding the custom intake tube for sale, I must give credit where it is due; I now recall that the wheels (in my head) got turning when I saw it a while back. It's a pretty nice device. If it delivers a 10BHP boost, that's great. I should add, though, that my main reason for the ghetto mod, other than the fact that it cost $5, is the joy I get from experimentation. If you knew the crazy stuff I've done over the years...

Mike

 

Mike,
When I got my first XJR and saw these "extra tubes" coming off of my air intake, I thought about drilling and filling with "Great Stuff" like you did. I keep a fresh can around the house all the time JIC (We know why it's got to be a fresh one). I had this thought as I installed a K&N FIPK on my Dodge Durango 5.2L back in 2003 (57-1509-1 - K&N 57 Series FIPK, Performance Intake Kit) and it dyno'd out at a gain of 10.74 HP @ 4580 RPM. It is a "clean" tube with no chambers. As I could not locate a commercial cold air intake for her as I did the Durango my mind started churning!

I thought I could fill them just as you did. My main concern, and I'm hoping you can help me out with this one, was how I could smooth the inside of the tube for cleaner air flow. I also immediately realized by doing this, even getting the intake smooth, I would be adding weight to the car. Granted, it’s not much, but in comparison, a 10 HP gain to a 400HP engine isn't much either, but we still WANT it! lol So I was working up a way of sealing the chambers without adding weight and making cleaner air flow.

My thoughts then shifted removal of the chambers with my Dremel, Skil saw, jig saw, Sawz-all, etc but leave enough plastic protruding that I could trim it in such a way that my soldering iron and eat gun allow me to manipulate the trimmings in such a manner that I could cover the holes smoothly and, essentially, welding the plastic leaving a clean path for the air, no extra chambers, and reducing some weight.

I’m very pleased to see your work as I’m looking to get a custom stage 1 tube from here and you've given me more ideas as I enjoy tinkering (no offense to anyone if that did because “tinkering” here doesn't mean the same as it does in the UK). To sum up my questions, how did you clean the foam out of the main tube for a smooth flow, did you weigh the piece before and after and if so, what are the results? You did go as far as to install a vacuum gauge to get more data and clearly thought about this quite a bit, so I am curious to learn the other particulars, if there are any.

My 04 XJR (Betsy) had a tragic end and I’m now working with my 05 XJR (Anya) and my thoughts are here at the moment. First: Order the Stage 1 tube and then after it arrives, try your way (weighing before & after) and try to measure the air flow, sound, etc. Second: If I cannot get it smooth, the start chopping and “welding” the openings followed by a weigh in and testing. Third: If I can’t get close to the sound, feel, seat-of-the-pants results, then I have the Stage 1 tube available and if I DO get good results, then I’ll have the Stage 1 readily available for future use if needed.

I’m looking for input for anyone & everyone as to what I’m thinking. I’m not presumptuous enough to even consider that I was the first person to think of this and I know there has to be others out there that have done all of these, either by different folks or one person and this is the perfect thread to ask these questions and learn more about what you've worked hard on. So hit me with em! lol

Rags

 

I used some aluminum tape to line parts of the inside of the tube prior to filling in with polyurethane foam. Some foam leaked past, but it came off by hand or with a little trimming with a razor.

In terms of weight, the foam adds virtually nothing. What will add weight is if you go the metal route. Cutting the chambers and plastic welding the hole will be messy and very Frankenstein looking. Also, it may be more difficult to smooth the inside; the chambers have a very radiused entrance that is hard to smooth without the help of the foam.

One interesting observation that I made is that there is a strong resonance at around 3200RPM. As the tach sweeps past 3200 the supercharger gets very loud then quiets down a split second later. I don't mind it in the least, but I'm sure Jaguar when they designed the intake specifically wanted to get rid of it! It would be startling and uncivilized for some XJR drivers! This leads me to another thought: what chamber length do we need to make more noise? I'm guessing based on my recollection of physics that you can achieve the opposite effect of the chambers by either adding 50% more length or cutting the length in half.

Mike

 

Thank you Mike!!! You addressed all of my concerns very well.


R,
Rag