That almost looks like an R56 front splitter? The curves are a bit odd and it looks a tiny bit short on both ends. Still looks good though. Always loved the G4 products.

I'm looking to do my own diffuser in the rear (have a front jcw bumper, and is too low for a splitter, and is an r56), but i'd have to commit to cutting the bumper, at least the plastic trim around it.

 

There's a bit of visual trickery going on, as the Droid phone has a very wide angle lens. The splitter goes right to the ends of the factory trim pieces. Note also the little winglets on that particular G4 test car (that picture is a splitter on a G4 R53, the diffuser's on my R53. I do have a G4 splitter but don't have pics yet).

 

Totally the idea and I've always been a fan of under trays and diffusers (vs. wings on hatchbacks).

Actually found it on Ecomodder.com and prompted me to search NAM:(http://ecomodder.com/forum/showthrea...nel-15189.html)

I think you're expeincing less drag as a result of stable flow under the car and exit, more than any effect of downforce (though your thought process is on target). Because most road cars ride much higher than race cars, the effectiveness of most diffusers are diminished. Additionally, the diffuser needs to be constructed of some "structural" material and mounted to the structure of the car (you went to the rear subframe; unsprung components are better- ie. control arms or wheel hub). Any downforce experienced would most likely cause the diffuser itself to deflect under pressure or push the rear subframe down, compressing the rear suspension.

Just food for thought.

I do plan on doing something similar to what you accomplished (especially the under tray). I'd probably mock everything up w/ the same material, then using as a mold for a glass or CF lay-up. One thing for sure, I'll bring the "end plates" (against the wheels) much lower in attempts to keep most of the flow from spilling over the sides.

I really like the sublteness of your diffuser as opposed to gaudy, gaping orfices that are out there.

 

Hey, I resemble that remark It's actually pretty interesting, with the dark color car the rear end doesn't look really gaudy, just serious, especially with the lower-offset (more "sticky-out") autocross tires on.

curv872, I did notice that while there is zero issue with heat buildup during 1-3 hour operation without a trailer on, during the 10 hour trip to MOTD this year I trapped a bunch of heat between the diffuser and the body, resulting in 140deg+ rear boot temps (and hence battery temps - yowtch!). Your rear screen idea was a great start - I actually just popped the rear plastic plugs and went screenless during MOTD and on the drive home. That dropped temps 20 deg or so, but still hot, and this with my straight-back exhaust, so no "cans' between the diffuser and body. Turns out even the small box trailer (top equal in height to base of rear window) gave me a huge "dead air" spot between car and trailer, keeping the area from venting. Without the trailer on and with the rear screens in (a $10 Home Depot mod that looks excellent), it's much better in the boot. I am going to add a center section to the diffuser, though, to keep that heat under the car and not allow any uncovered airspace above the exhaust pipe itself...

Doing the engineering on the exhaust and tweaking/testing the splitter/diffuser combination gave me new respect for the depth of engineering that goes into making a mass-market automobile as good as it is!

More on G4 coming... the company may be undergoing a resurrection...

 

Which diffuser are you using?

I was referring more to the ones that require a massive butcher project to the rear bumper cover.
Your's appears to be on target my level of agressiveness (styling)...LOL

 

Thanks for the kudos.

Yes, the clean airflow is basically reducing lift, not so much creating downforce, so structurally tying the diffuser to the chassis will not matter. Cars generally produce more lift as they go faster, so the diffuser does a great job of abating some of that.

 

to answer the very FIRST question on this post, isnt THIS what you are looking for?!

http://www.ebay.com/itm/221035622893...84.m1423.l2649

 

That said, the diffuser needs to have some firmness to the attachment points. The bumper cover is quite adequate for street cars, but for racing I'd tie that sucker (literally a "sucker", I suppose!) to the chassis via the rear bumper area.

The other thing to remember: That underbody area gets a TON of grit/salt/roadcrap thrown up, and both drainage and bodyrot need to be taken into account. You do NOT want to trap moisture, or solids like snow/ ice/ and rocks, in places they should be in. Also, all fasteners should be stainless or at minimum cad plated, with ample anti-rust coatings used. Likewise, diffusers are Large Things, and if your car ejects a Large Thing onto the road behind you, Bad Things will happen.

With few exceptions (typically spoiler lips), you can't just "peel and stick" aero aids on a car - there's a lot of force in play.