Turbulent Air Behind Car Causing Dirty Bumper

[hotplates34]

I have an R34 GTT and every time i take it for a drive the rear bar gets filthy, even on perfectly good days, take her to the car was and by the time i get home dirt has stuck to the water and has dried, i was reading that the shark like fins on bmw's are put there to keep the aero stuck to the car so the air isnt turbulent behind the car causing the bumper to get dirty, im sure there would be improvements in performance by removing this drag anyone know of a fix?

[Spurdo]

are you sure the dirt isn't oily? usually whenever i've seen this its because the car is losing oil somewhere and it tends to stick to the rear of the car because of the low pressure area there when moving. normal dirt & dust etc won't usually stick onto the paintwork unless there was oil there first.it will probably be especially bad if you've been driving at highway speeds.

i've seen it happen once when my parent's old subaru wagon shit it's transmission in the middle of nowhere on a long drive and there was an oily film all over the back of the car from it, and another time one of my first cars was using a shit load of oil before i rebuilt it, i drove down to christchurch and by the time i got there the back was covered in a thin film of oil, and yea, dust and debury was there as well because it now had something to stick to.

[The Bogan]

Happens all the time to me though not through oil loss, happens if your running a little bit rich.

[hotplates34]

its not oily or just around the exhaust, its like when you just polish your car and all the file fluff sticks to it but with dirt, know any ways to improve this low pressure behind car? like a roof spoiler or changing the tilt on the rear wing?

[drunkn snail]

i get the same thing on my car, its black so its easier to see, although it only happens when driving down dusty roads and my driveway

[greensa14]

Does your exhaust not come past the rear bar? If it sits in a little that could be the cause.

[GH05T]

dont know what spoiler u have, but lip spoilers move the "ball" of turbulence further back from the car, designed to make less drag but it helps with the shit too

[Humbla]

I allways get this as well,only way i can get it off is with polish and then put a coat of wax over that.It's a pain but works.

[GTR-N1]

Malco Nanotech Banana Cream Wax, will get that stuff off without the abrasion of a polish. PM me Genelle if you do make the SAU AGM, and I'll give you a bit if you bring a small bottle.

OP, how long since the car's last tune?

Does the exhaust tip extend far enough?

How rich is it running?

On cold start is there a lot of white particulate matter or dark?

[adamskill]

you really know your products terry!!