high exhaust

[tomislavp4]

It was inplemented first in 1998 but what is it for. WHY? Aerodynamics or...

[DaveKillens]

Traditionally, the teams just ran the exhaust towards the rear of the car. And of course, the lower anything is on a race car, the better. So we wound up with cars having the exhaust exiting the car low down and far back. Then along came ground effects and diffusers, and slowly the engineers realized that all that hot air pumping out the back could upset the balance of the car because it had a direct effect on the diffuser. Step on the gas exiting a corner, and the car's rear end behaved totally different than not stepping on the gas.
So now we see the latest trend, where all that hot air is pumped out rearwards and along the top rear of the sidepods.

[Steven]

Apart from Dave's explanation, there is another advantage for the high exhausts. As the exhausts are shorter than before, it is advantageous for the engines. More specifically for the high rpms that are achieved these days. A shorter exhaust pipe equals a higher frequency and allowed higher rpms.

See more here: An article on F1t about exhausts

Anyway, the aero advantage in the beginning was not that obvious, in fact it might have been the opposite. However it gives the car a more equal behaviour, no matter how much the throttle is pushed.

McLaren even tried low exhausts later on with their MP4/18. However, the car was troublesome and never made it to a race

[Tp]

Well the periscope-style exhausts seen on the Ferrari '02 - '04 allowed the bodywork around the inside wheels to be pulled in tight with the transmission, to improve the aero efficiency of the car.

[zac510]

The design of the high exhaust has changed in recent years too, previously it was cut short inline with the bodywork but lately they have switch to the periscope designs with shrouded bodywork around the leading edge.

[mini696]

Its to do with packaging mostly these days.

Teams used to use the exhaust exiting into the diffuser to improve its downforce, although there isnt too much advantace to that now.

[DaveKillens]

Imagine the long, fast corner at Indy. A car picks up speed, then just entering the turn sees a big problem right ahead. But the driver is at full throttle, and as soon as he lifts, there is abrupt oversteer, and he does a Ralf into the wall.
That's the scenario if they still had the exhaust coming out down in the diffuser.

[gcdugas]

Imagine the long, fast corner at Indy. A car picks up speed, then just entering the turn sees a big problem right ahead. But the driver is at full throttle, and as soon as he lifts, there is abrupt oversteer, and he does a Ralf into the wall.
That's the scenario if they still had the exhaust coming out down in the diffuser.

I think you have that exactly backwards. With less exhaust gases to fill the diffuser, down frce would increase in response to the lo pressure zone. But this is beside the point, the exhaust used to exit beside the diffuser, not actually in it.

[kilcoo316]

I think you have that exactly backwards. With less exhaust gases to fill the diffuser, down frce would increase in response to the lo pressure zone. But this is beside the point, the exhaust used to exit beside the diffuser, not actually in it.

I was under the impression the exhaust exited below the diffuser, and "blew it" - that is, dramatically increased downforce when on throttle.



This would also be undesireable as it would force a higher ride height for going down the straights, but force a higher c.g. position for the corners.

[mini696]

I think the exhaust exiting into the diffuser helps more in high speed situations (or high rev).

My understanding of diffusers is that you want the hole to be 'empty' of air (at low pressure), therefore with no throttle (braking) the pressure is lower, therefore the downforce created is higher. At high revs (acceleration) the exhaust 'fills' the diffuser, and therefore creates less drag.

[Rob W]

...and as soon as he lifts, there is abrupt oversteer, and he does a Ralf into the wall.

Don't you mean "does a Sato into the wall." ?

Rob W

[gcdugas]

I think the exhaust exiting into the diffuser helps more in high speed situations (or high rev).

My understanding of diffusers is that you want the hole to be 'empty' of air (at low pressure), therefore with no throttle (braking) the pressure is lower, therefore the downforce created is higher. At high revs (acceleration) the exhaust 'fills' the diffuser, and therefore creates less drag.

A wing has high drag to (negative) lift ratio. A diffuser almost gets its down force for free. That was the beauty of ground effects cars. They want high down force at all times. The exhaust never filled the diffuser. It would hurt the lateral grip exiting corners. It was on the sides of the diffuser. Think about the plumbing issues getting the pipes back to the center line. The gearbox is also in the way.

[DaveKillens]

Technically, there can be as much as seven jones in a diffuser. Centerline, and as much as three on each side. The exhaust on older designs would exit somewhere, but definitely in the diffuser. The exhaust produces hot gases, but also when it exits the pipes, high velocity. That high velocity would boost the rest of the air velocity in that diffuser area, adding downforce to the rear.
But no matter what, shifting revs or sudden movements of the throttle would unsettle the delicate balance in the car.

[gcdugas]

Technically, there can be as much as seven jones in a diffuser. Centerline, and as much as three on each side. The exhaust on older designs would exit somewhere, but definitely in the diffuser. The exhaust produces hot gases, but also when it exits the pipes, high velocity. That high velocity would boost the rest of the air velocity in that diffuser area, adding downforce to the rear.
But no matter what, shifting revs or sudden movements of the throttle would unsettle the delicate balance in the car.

Au contraire. Anything that fills the diffuser would only detract from the low pressure zone and coresponding downforce.

[DaveKillens]

The concept of entrainment works here. A good example is the eductor pump.
So the air being ejected by the exhaust pipe entrains the air in the diffuser and helps accelerate it rearward.

http://www.1877eductors.com/tank.htm