Post-Turbo exhaust design

[Wideband mindeD]

Is there any interesting tricks of the turbo trade to talk about here? I understand how important proper exhaust design with wave timing increases performance, but would like to discuss this area of the new regs.

Any thoughts?

[flynfrog]

as big and as short as possible

[wuzak]

as big and as short as possible

But it isn't going to be short - the exhaust has to be behind the rear axle line.

[WhiteBlue]

as big and as short as possible

But it isn't going to be short - the exhaust has to be behind the rear axle line.

The answer is as simple as it is correct. You want to achieve the lowest possible pressure at the exit of the exhaust turbine in order to maximize the pressure differential over the turbine. The turbine entry pressure is dependent of the operating conditions of your ICE and the turbine design. The turbine exit pressure is dependent of the pressure loss in your exhaust pipe and the local pressure behind the exhaust pipe exit. So there are three things you want to do:

• make the pipe as wide as feasible to reduce aerodynamic friction
• make the tube straight and as short as possible again to reduce aerodynamic friction
• release the exhaust at the pipe exit preferably into a low pressure field (if available)

[wuzak]

• make the pipe as wide as feasible to reduce aerodynamic friction

I assume you mean as big a diameter as possible? The regulations specify a circular cross section, at least at the outlet.

The last 150mm of the exhaust pipe must be a circular cylinder.

The regulations specify only one outlet from the turbine/wastegate, but there can be two exhaust pipes.

The exit area for the exhaust pipe(s) must be between 7,500mm² and 14,000mm².

For a single pipe that means a diameter of between 97.7mm and 133.5mm. For two pipes it means a diameter of between 69.9mm and 94.4mm (assuming equal sized outlets).

I would imagine the would resist using two pipes, since the split from one to two would, probably, cause extra friction.

• make the tube straight and as short as possible again to reduce aerodynamic friction

I was wrong earlier. The exhaust outlet is forward of the rear wheel centreline - by between 30mm and 50mm.

It still makes for a lengthy exhaust pipe.

• release the exhaust at the pipe exit preferably into a low pressure field (if available)

The bodywork regulations make that difficult. However, the exhaust can be angled 10° from the car centreline, and from 0 to 10° up at the rear. These angles could help to make a low pressure area at the outlet (airflow will try to suck air out of the pipe).

[ringo]

The exhaust must be a diffuser; with a highly polished inner surface. The diffuser muss be frilled as well.
And even if bodywork cannot be behind the pipe, some upstream tricks can be used to lower the pressure.
The turbine needs lowest pressure at blades exit, which is achieved by a diffuser.
So for example if your turbine orifice is 3 inches, you need maybe a pipe diverging to maybe 5 inches. I'm not sure of the max allowed diameter.

[wuzak]

The exhaust must be a diffuser; with a highly polished inner surface. The diffuser muss be frilled as well.
And even if bodywork cannot be behind the pipe, some upstream tricks can be used to lower the pressure.
The turbine needs lowest pressure at blades exit, which is achieved by a diffuser.
So for example if your turbine orifice is 3 inches, you need maybe a pipe diverging to maybe 5 inches. I'm not sure of the max allowed diameter.

Max diameter for a single pipe is 133.5mm.

You can make the exhaust diverge to your 5", but then it has to remain constant for 150mm.

Bodywork cannot be within 40mm of the last 150mm.

Most of the upstream bodywork is the engine cover. This already has strict rules as to what can and can't be done.

Not sure what you mean by "frilled". In any case, the last 150mm must be circular in cross section.

[flynfrog]

i dont think the original poster was asking about F1 in particular

[neilbah]

but would like to discuss this area of the new regs.

seems they were. So are we saying a slightly expanding cone from the turbo outlet to the regulated exit area.

[Wideband mindeD]

I am deffinately talking about F1.

If there are the allowances of 2 pipes on exit, we may still see a coanda exhaust setup.

What about flanges on the end of the pipe to create a low pressure zone at the exit?

Could deforming the pipe in any fashiopn before the final 150mm help in any fashion? Like maybe a short resonance chamber???

Interesting stuff! Thanks for the replies so far!

[wuzak]

If there are the allowances of 2 pipes on exit, we may still see a coanda exhaust setup.

Can't. No bodywork will be near enought to achieve that.

[WhiteBlue]

If there are the allowances of 2 pipes on exit, we may still see a coanda exhaust setup.

Can't. No bodywork will be near enought to achieve that.

I thought you are only allowed one exit. Where did the second suddenly come from?

[wuzak]

If there are the allowances of 2 pipes on exit, we may still see a coanda exhaust setup.

Can't. No bodywork will be near enought to achieve that.

I thought you are only allowed one exit. Where did the second suddenly come from?

From the rules:

5.8.2 Engine exhaust systems may incorporate no more than two exits, both of which must be rearward facing tailpipes, through which all exhaust gases must pass.

Another interesting one:

5.8.1 With the exception of incidental leakage through joints (either into or out of the system), all (and only) the fluids entering the compressor inlet must exit from the engine exhaust system.

So there can be no air taken from the compressor to do diffuser blowing or double DRS-ing.

[Holm86]

Please read the updated regulations, they say :

"5.8.2 Engine exhaust systems must have only a single tailpipe exit which must be rearward facing and through which all exhaust gases must pass."

[wuzak]

Please read the updated regulations, they say :

"5.8.2 Engine exhaust systems must have only a single tailpipe exit which must be rearward facing and through which all exhaust gases must pass."

Oops, so I have an old copy here.