mrrrkva

Just thought I would post some pics of the "Bare" car at Carlisle.

yellowray

What are those two devices mounted just ahead of the inlet to the mufflers, some sort of valve control to restrict exhaust at low speed?

mrrrkva

I believe this is the NPP option that Makes them Dual mode. Give you 5 more HP and louder in the track mode

ByByBMW

I also noted that the radiator is slanted forward at the top, IIRC the C6 was slanted back at the top.

Walt White Coupe

First the valves: They are on all models to deal with the sound of the exhaust in 4 cylinder econo mode to make the exhaust sound better.

The slanted downward radiator is in that configuration so the airflow is directed to the hood vent and produces added down force.

slief

If I'm not mistaken, those are used to close off some of the exhaust flow for when the car is in cylinder deactivation mode. They would in theory close/restrict the exhaust partially to create additional back pressure when running on 4 cylinders. These would function separate from the multimode exhaust valves at the exit of the mufflers which operate similarly to those found on the NPP exhaust of the C6.

kozmic

Looks to me from other pics that the NPP butterfly valves are in the tip tubes after the mufflers (like current the NPP, yet moved from the inside tip tubes to the outside tip tubes).

I am thinking that the valves ahead of the mufflers are related to the variable sound noted when changing the driving modes that also change the level of growl from the exhaust.

mrrrkva

Front lift is reduced by tilting the radiator forward, just like the C6.R race car. Gives more downforce. This eliminates the "gremlin" of front end lift at high speeds that the C6 had.

kozmic

That shows how much I know about aerodynamics... I would have though the exact opposite, that the slant (top-forward) of the radiator (and resultant direction air pressure created by it) would actually create lift... crazy...

yellowray

Sounds logical. Could also help hide the sound change from 8 to 4 cylinders. I don't know, would more back pressure help catalysts function better on 4 cylinders?

jvp

Clarification: the simple act of tilting the radiator forward does very little, if anything for aero and down force. What it does, however, is open up the possibility of adding air flow through the front end of the car via vents in the bumper and hood. That is what provides the down force, and significantly better engine cooling.

I Bin Therbefor

Yup, mrrrkva is right, that's the way it works.

A couple of good old references are Aerodynamics of Road Vehicles by Wolf-Hendrich Hucho and Race Car Aerodynamics: Designing for Speed By Joseph Katz. Available through your local library by inter library loan.

Jim Hall of Chaparall fame did an awful lot of work with whole vehicle aerodynamics. His story is worth the read.

Some early race car designs had the radiator parallel to the ground with a "bottom" intake and exhausted through the hood.

Note that the new Viper also exhausts through the hood. The Viper GTS-R has huge hood exhausts.

The trick is to exhaust into a low pressure area on the hood and pick up from a high pressure area in the front or underneath the car.

kozmic

Ah... that makes sense. Thanks!