if you look at his underpanel it looks like he tied up the front of it with zip ties...?

 

I finally got my Beatrush front underpanel installed last week. I bought it 'used' (never installed) and the mounting hardware and instructions were lost during shipment. Finally scored a copy of the mounting instructions which allowed me to figure out how it went on and more or less duplicate the mounting hardware.

First thing you have to do is remove the existing plastic undertray. Then the front of the Beatrush panel mounts right up without modification. I made my own holes in back so I don't have those extruded brackets hanging off the back end. 6 bolts (allen screws in my case), 4 in front and 2 in back, hold it securely in place. I cut the vertical 'wings' off the stock undertray and reinstalled them so that I still have full inner fender coverage. I did this to keep road crud from being sprayed all over the engine compartment. I highly recommend this to anyone considering this piece; it takes all of 5 minutes, time well spent IMO.

Impressions: First of all, it looks pretty cool under there. Of course you have to stand on your head to see it, but still. Once underway I noticed a tiny bit more exhaust 'boominess' in the passenger compartment, which makes sense seeing that the panel covers the entire bottom of the engine and transmission area all the way back to the front crossmember. I honestly consider the amount of extra sound to be inconsequential. I don't notice it at all anymore.

In normal driving I notice no difference in the car's performance or behavior. It drives just like it did before.

I do a bit of coasting in search of MPG improvement and I'd swear I can coast further now than before; however I don't have any way to measure so this impression will have to remain seat-of-the-pants.

Cornering at speed has improved. The front end has lost its fussiness when I hotshoe it into my favorite offramp (entry speed is 65MPH), and the car arcs more smoothly the rest of the way through. I haven't done the turn enough times yet to tell for sure but my exit speed should definitely be higher. This is not my imagination; the front end is definitely happier at speed in turns.

Another big difference I noticed just today when I played around in the slipstreams of several big rigs while moving at freeway speeds, 60-70 MPH. The car used to jostle around a bit when I was alongside a truck, especially near the front end of it where the airflow breaks over the trucks' front end. With the underpanel the car is very stable, no more jostling. The same thing is true when drafting 30 to 50 feet behind a tractor/trailer. Before, the car would get buffeted around, now it just sits there pretty as you please. In short, the front end is happier at speed when going straight ahead. The difference is impressive.

As for MPG, it's still a little early to tell. I did score 40+ MPG on two consecutive tanks for the first time ever so I'm optimistic. If there is an improvement it is in the ~2MPG vicinity, not enormous but better than nothing. Best of all, I don't have to change a single thing about the way I drive in order to get it. I'm tracking my mileage on cleanmpg.com so the chart will tell the tale over the next few weeks.

So far I'm happy with the purchase. It does at least as much as I expected and may even wind up doing as much as I hoped. Not bad for something you can't even see!

 

eh if u do mostly highway driving ya it will help some while at speed but city driving speeds are too slow. For track use this would be nice or just as another mod just to be different. I plan on just copying all the other ones out there and just making it myself not too much to it besides having to test fit and cut for perfect fit plus i wont spend a dime making it

 

All correct. True so long as you have a thingie to cut cooling vents. Use a thicker material, don't bend it much at all, and pay attention to the left and right edges and where the holes go in the front.

For this information I demand your eBay firstborn!!!

 

WDB, Thank you for confirming what I felt when I put my BeatRush panel on. I simply love mine and I did finally break the 41+ MPG with it on.

Thanks to you my placebo effect is now gone!!

 

Well I'll be damned. another semi-hypermiler. Thanks right back, friend.

What a piece, don't you agree? All good and no bad. What could be better.

 

Update: I'm going to credit the Beatrush underpanel with a 2MPG improvement. 37.7 average MPG for the 10 tanks before I put the Beatrush underpanel on the car, and 39.9 average MPG for the 10 tanks since then. 10 tanks is enough data for me to conclude that the underpanel makes a genuine difference. At $3.75/gallon for gas, the Beatrush underpanel will pay for itself in about 25,000 miles. That's a lot, I know. But I do more than that in a year, so it works for me. Plus the increased stability provides an 'intangible' benefit that is hard to put a dollar value on but is there nonetheless.

Conclusion: get one!

 

wdb can you take pics of how you mounted yours?

 

that actually looks really cool!

But I really don't think it's meat to help you get better MPG...the point of underpanel is mainly to create downforce, because when the air pass between the underpanel and the ground, it creates a suction effect, therefore sucks the car to the ground, at times, this force can be quite substential. Time Attack cars have seen up to few seconds of improvement from adding an underpanel. so at higher speed, it will actually only make you go slower on straights and lower MPG.

Now...all that is based on my understanding of physics, and track times I have seen on japanese car magzines...

 

It really does -- but you have to lay on the ground to see it.
I totally agree. But it does improve MPG nevertheless. We're not talking about racing conditions and speeds, just legal US highway speeds. At those speeds the car is noticeably more stable, particularly in fast sweepers such as exit ramps. I also no longer experience buffeting when the big rigs roll by. And my MPG is up by 2. Win - win.

 

I've been asked for pictures several times, and here they finally are. I was under the car changing the oil and wanted to change the mounting hardware around a bit, so I figured I might as well snap some pictures. Please note that the panel has been on the car for several thousand miles, so it's dirty!

First of all, here's the panel itself:



Here it is next to the piece it replaced. Note that I cut the vertical sides off the old "underpanel" and reinstalled them, more on that in a second:



Here are the pieces I cut off the old plastic undertray. They mount very securely, with two mount points at the top, one at the front, and one at the back, and they keep a lot of road gunk from being thrown up into the engine compartment. I highly recommend doing this. Left (driver's) side, then right side:






Next comes the mounting points. Important note: my panel did not come with mounting hardware so my setup will look a bit different than the Beatrush pieces. First the front: the holes I used are exactly the same as the Beatrush hardware uses, and are easily accessed once the old undertray is removed. Another important note is that the holes are directly beneath the radiator, so be careful that you don't use too long a screw or it could puncture the radiator! No I am not kidding. The mount points are circled in red:




At the rear, the Beatrush hardware appears to use a U-shaped extrusion to extend to the mounting hole (marked with an "X" below). I didn't have that so I did something very, very expedient: I drilled a hole straight into the crossmember and tapped it to the threads of my mounting hardware. It works quite well and is very secure because the crossmember is triple-thick steel at that point. My mount point circled below.



The Beatrush U-shaped extrustion lifts the back of the underpanel away from the crossmember, so I decided to add standoffs to my rear mount points just in case there was a technical reason (like airflow) behind the Beatrush mount. This is a shot of my standoffs, nothing more than a couple of pieces of ~1/2" thick plastic:




And finally, the moment you've all been waiting for:

 

WDB THAT LOOKS SOO CLEAN! Thanks for a very well written write-up!! And also the great pictures! +rep

 

Nicely illustrated! I will seriously consider purchasing this product...

 

what happened to the pics? I am thinking about it for chirstmas!

 

Try the pics again. I'm getting a bit frustrated with my image hosting service...

 

I'm sold! Thanks for the excellent pictorial on your installation - very clean and craftsman like.

I have the dealer do the oil changes for now. That will change, but for simplicity sake, could a smaller door be added to the larger panel to make for easier oil and filter changes. Maybe piano hinged? Possibly overkill, but if the service techs whine it may be worth the effort. Besides, I love tinkering.

 

Anything's possible I guess. But to be honest I think it would be overkill. You'd have to cut two holes (or one really big one, I guess) for the filter and the oil drain, then you'd have to rig up a way to open/close or remove/attach them. All that, when the whole piece goes on with 6 screws? I dunno.

I think the best way to deal with simplifying removal/installation is to go the route I took and make the bolts come on/off with the panel.

 

I installed my underpanel this afternoon . . . For anyone concerned about JDM vs. USDM fitment, don't be - the panel has 2 sets of rear holes drilled. One that matched up with my '07, and the other that (presumably) matches a JDM front end. The directions were, as others have noted, completely in Japanese. And even the diagrams I found to be mostly indecipherable. But the front 4 bolts can be figured out from the picture, and once the front 4 are on & holding the panel in place, you can use process of elimination to tell how the rest of the hardware bolts up. I'm not super impressed with the brackets supplied, they seem rather 3/4-assed. The 2 rear ones you'll wish you had a 3rd hand to get the mounting bolts threaded. That said, it's plenty solid once mounted, it'll hold fine. All told, it took me about 2 hours to install. And taking it on & off for oil changes will be easy - 10 minutes, tops.

I took it for a quick spin on the highway, didn't notice any stunning difference - but I'll wait for a windy day. As it is with my puny winter tires, it's downright scary at times. Hopefully this will cure some of the "lift-off" problems I've been experiencing. And, of course, I'll compare my mpg results to the first 12 tanks since I got the car.

 

Congratulations! I hope it helps with your stability issues as much as helped me with mine. You don't need to wait for wind, just mix it up with some semis and/or take an exit ramp with some gusto, and you should be able to feel the front end staying put.

As for it taking 10 minutes to remove for oil changes -- wow. I changed my oil two days ago; it took about a minute to remove, about as long as it takes to unscrew the 6 mounting bolts. It takes a little longer to put back up due to getting everything lined up -- I'll say two minutes. So maybe I'm glad not to have the Beatrush mounts.

Anyway, congratulations again and let us know how you like it.

 

For those w/ lowered Fits and the Beatrush underpanel......do yawl experience any scraping on driveways or speedbumps, etc. w/ the Beatrush underpanel?

Just wondering. Thanks.