Crashmaster

Every time someone mentions some modification to their grille, there are always those who pop up quickly stating that this will disable the CMBS system. It appears that sometimes they are right and sometimes they are not. Instead of making blanket statements about what will or will not block the radar sensor, here is the low down. I spent most of the night researching this and if you find better or newer information, please add it below.

CMBS which stands for Collision Mitigation Braking System which is part of the Advance TLX package.

This system utilizes a millimeter wave radar sensor that can scan up to 330 feet of the road ahead (See picture below). When it detects something and calculates that a collision might be possible it progresses through three stages of action being: (but might not use all the stages depending on the circumstance).

STAGE 1 = Flashes a brake warning in the dash (BRAKE) in RED along with a Heads Up display on the windshield flashing 3 lights. Depending on the distance, an audible alert might also be heard.

STAGE 2 = All of the above will continue plus the vehicle will apply light braking. It will also slightly tug on the driver’s seat belt.

STAGE 3 = All of the above plus stronger seat belt tension along with heavy braking.

The CMBS can be adjusted. Going to SETTINGS, then choose VEHICLE SETTINGS, then DRIVER ASSIST SYSTEM SETUP, then choose FORWARD COLLISION WARNING DISTANCE. It will then give you the option of LONG, NORMAL, or SHORT. You also have the option of turning the system totally off by pushing the CMBS button to the left of the steering column.

Millimeter waves occupy the frequency spectrum from 30 GHz to 300 GHz. Just a few years ago, this part of the spectrum was essentially unused simply because few if any electronic components could generate or receive millimeter waves.

What can affect millimeter waves? Water (rain or snow) can cause the signal to deteriorate as reflections from rain or snow can be mistaken as echoes. Eight cm of fresh snow on the grille can cause a 20% less detection distance rate.

Millimeter Radar can be blocked, reflected or absorbed. Metal reflects or blocks radar. If the TLX beak was replaced with metal, most signals would be blocked, but some would be bounced around the metal beak and get around it, but there would be a tremendous loss of signal distance. If you painted the beak with metallic paint, it would also show as a deterioration of signal, but it would depend on the amount of metal flake, how many coats, etc. etc. Millimeter radar can go through many substances but with each added layer, there will be a loss, and it is the amount of loss that you need to be concerned with.

As for carbon fiber, the only reference I could find on the Internet was carbon fiber boating sails. Carbon fiber sails reflect radar, but it varies due to thickness and type. For the most part, carbon fiber sails will block either completely or partially the radar waves. Most sails are made of Dacron which is transparent to radar.

http://www.rfcafe.com/references/electrical/dielectric-constants-strengths.htm

Above is a link for a chart for the technically advanced that lists the loss tangent of many substances. For the most part, here are some substances which are OK. Plastic, cardboard, paper, clear glass, non-metallic paint, Teflon and non-metallic plastics, etc. Again, anything placed in front of the beak will cause some loss including the plastic beak, but it is the amount of loss that you are concerned about.

Things that are NOT ok are: most all metals. Metallic paint.

NOTE: Just because carbon fiber acts as a reflector and blocker of radar, I would not go ripping off the carbon fiber just yet. I would do a few tests first. The weaving, density, and mix components of the purchased carbon fiber might allow the signal to get through. As for the 3m plastic sealer, I previously checked with 3m who told me that it would block no more than 5% of the signal. When you add the paint on the beak, I estimated about a 10% loss, which to me is minimal and I can live with that especially by adjusting the distance from NORMAL to LONG which should make up for the 10% loss.

Being that the ACC (Adaptive Cruise Control) uses this same radar, you can easily test the radar blockage of your beak by setting your cruise at various distances to make sure it can still follow the vehicle ahead of you at various distances. If you want to experiment with using different substances, you can easily place something in front of the sensor to test the blockage ability. For example, wrap a piece of cardboard with carbon fiber and put it in front of the sensor and do a few test runs.

My background is engineering but not this type, so if anyone has a question or comments please feel free to jump in.

kongx7

How about everyone just don't rely solely on your car's safety features all the time. Take control of the car and be a safe driver!

Great research and post though.

kongx7

Lol. Forgot to mention, that it would be nice to know your safety features work since you paid for it. Thanks again for the research!

Stew4HD

Just an FYI, we were told by Acura to not block the radar behind the shield

Rocketsfan

I think the car itself may show nag messages in the vehicle/MID when it detects "enough blockage". In any case, I would rather not do anything that could potentially block it. What if there is some algorithm that applies braking relies on distance detection and the resulting weaker signal strength interferes with that somehow? What if I'm full of crap? What if ... eh... I'd rather not take the chance. lol.

mapleloaf

It's times like this that I'm glad I don't do these types of mods…..although I only have a Tech package and have less to worry about. I like my silver beak with the SSM.

Crashmaster

I fully understand about leaving things alone. But then there are some of us who want to try out cross drilled rotors, different mufflers, tires, and playing in the forbidden areas of the software. Nobody is telling anyone to make these changes to your TLX, but many want to make changes and it is this gathering of information that helps others.


Acura makes cars for the general public. They don't go too far to the left or right with performance, handling, and styling. Their goal is to sell cars to the general public and they make a vehicle for this purpose.


There is room for modifications without sacrificing safety or drivability. Granted that when playing with a safety feature such as the CMBS, brakes, tires, etc. you must research and decide if your modification will cause any adverse affect. Millimeter radar is relatively new and I'm still experimenting with it. As I find out more, I'll post it to the board.

oracion

There's a change that that may cause some radar interference. Check out the "CMBS GRILLE DIFFERENCES" section this doc: https://techinfo.honda.com/rjanisis/...BN%2051802.pdf. It says that "a special black coating
is used on the back side of the molding". My guess is that additional coating or changes to the grill may affect the function of the unit. Hope that helps.

Crashmaster

Yes, I was aware of that; as when I removed my grille I noticed that the back of the grille was painted a sort of flat black. I looked it up and found that radar tends to reflect off of shiny or glossy colors. Flat black tends to allow radar to flow through it much easier. My guess is that the back of the grille beak on a normal TLX or TLX w/Tech is silver’ish.