Do rear bumper diffuser's work? By work I mean is there any effect on trap speed and/or et? Now I dont wanna here any opinions, FACTs only. Have real facts to back up any claims you may make, ie they do or dont work. No they look ricey or other Opinions like that, lets talk aerodynamics

 

Anything that smooths out/speeds up airflow underneath the car will help with aero efficeincy. Sounds like your refering more to drag racing. I think diffusers are more of a roadracing thing, helps with high speed stability.

Wrong section BTW. This doesn't have anything to do with engine/turbo/drivetrain.

 

I am talking about drag racing, Im not talking about the average car trapping 100-120 but a 9 sec car trapin 150+. Say for example will a car that ran a 9.x at 150mph without a diffuser see any gains in et and/or trap speed?

Didnt really know where to put it as its more performance related than anything else and this is the performance section.

 

i have one for sale if you get your information and want one let meknow its a varis.

 

You could try the drag racing forum. Some guys there may have the info your looking for.

https://www.evolutionm.net/forums/drag-racing-16/

 

A diffuser won't do much at all with having turbulent air being fed to it.

Diffuser by its self, kinda pointless.

Diffuser and proper entire under-paneling = yes.

 

Im not talking about this type. Im talking about the long bar with holes in it that alot of hondas use.

 

Personally, I wouldn't call that a diffuser, I call that a bumper with holes in it to let air out. Try posting a pic so people know what your refering too.

 

Read first post, NO OPINIONS.

 

But as theres differnt types, which ones work and which dont? That is if any actualy work. This is the type Im referring to

 

I'm with grillpt, that's not a diffuser and calling it such is misleading.

I have a couple friends that have used them. None of them have found any gains with them though.

 

Well they dont make the kind like the 9 comes with for eclipse's so this is my only option. What was their et/trap? My thinking is it will only help on high trap speed cars 150+.

 

140+ mph civics

If this is a drag car, I'd consider cutting out the spare tire well and doing a full blown diffuser.

I saw an N/A civic at one point that did a full underbelly and rear diffuser. That car was trapping like 130 and running like low10s/high 9s and it picked up like 5mph. It made a BIG difference on that car, but it was a full underbody.

 

Ya I was just on hondatech, it seems at 120mph a car will pick up 1mph, at 140 they have gained 3mph in a 1/4 mile. With almost the same 1/8 mile. Thats just a rear bumper diffuser like the pic I posted. With that said a 150-160 car would pick up even more say 6+mph.

 

You can't correlate what other cars pick up to what an Evo or eclipse may or may not pick up. Different aerodynamics for a given car means different results. For a 150mph civic it might be a 6mph gain on an 150mph S2000 it might be 2 it would probably hurt a 150mph supercar to blast 4" holes in the rear bumper cover.