Post-Turbo exhaust design

[wuzak]

Ahh i misunderstod. But i do. Higher density means you can run lower boost. Lower temperatures mean you can run higher CR.

Higher density = more air = more fuel = more power. Not better efficiency.

[Holm86]

Ahh i misunderstod. But i do. Higher density means you can run lower boost. Lower temperatures mean you can run higher CR.

Higher density = more air = more fuel = more power. Not better efficiency.

Higher density = more air + same amount of fuel = less boost required. Less boost = more of the turbines work can go to the MGU-H.

Cooler temperature = later ignition or higher CR = higher efficiency.

[WhiteBlue]

But the issue was water injection into the exhaust, not into the air intake. So my question is still how water injection into the exhaust cools the air.

[wuzak]

Ahh i misunderstod. But i do. Higher density means you can run lower boost. Lower temperatures mean you can run higher CR.

Higher density = more air = more fuel = more power. Not better efficiency.

Higher density = more air + same amount of fuel = less boost required. Less boost = more of the turbines work can go to the MGU-H.

More air, same fuel = leaner mixture = less power,

[wuzak]

But the issue was water injection into the exhaust, not into the air intake. So my question is still how water injection into the exhaust cools the air.

No, the issue was water injection into the inlet to the compressor.

[Holm86]

Higher density = more air = more fuel = more power. Not better efficiency.

Higher density = more air + same amount of fuel = less boost required. Less boost = more of the turbines work can go to the MGU-H.

More air, same fuel = leaner mixture = less power,

No not if you decrease the boost as i said.

[Holm86]

But the issue was water injection into the exhaust, not into the air intake. So my question is still how water injection into the exhaust cools the air.

No one has talked about injecting water into the exhaust. This would be illegal.

I said injecting before the compressor intake.

[WhiteBlue]

But the issue was water injection into the exhaust, not into the air intake. So my question is still how water injection into the exhaust cools the air.

No, the issue was water injection into the inlet to the compressor.

Yes, you are right. I somehow had turbine intake in mind. No idea how I got that notion.
Water injection would be a legal possibility, but none of us knows the intricacies of the 2014 combustion process good enough to draw any conclusions how the use of water would influence the power to weight ratio. If you have a water system it must earn its weight by giving enough additional power.
Hasn't water been used in WWII aero engines?

[Holm86]

But the issue was water injection into the exhaust, not into the air intake. So my question is still how water injection into the exhaust cools the air.

No, the issue was water injection into the inlet to the compressor.

Yes, you are right. I somehow had turbine intake in mind. No idea how I got that notion.
Water injection would be a legal possibility, but none of us knows the intricacies of the 2014 combustion process good enough to draw any conclusions how the use of water would influence the power to weight ratio. If you have a water system it must earn its weight by giving enough additional power.
Hasn't water been used in WWII aero engines?

Yes it was used in aero engines. During take-off or dog-fights where additional power was needed.

And its not like you would need that much water. Its a small mist used at WOT. Perhaps a 10l tank would be enough for a race. If you could instead decrease the size of the intercooler perhaps it could be worth it.

[wuzak]

Hasn't water been used in WWII aero engines?

Yes, and in previous F1 turbos.

[Tommy Cookers]

(btw 'WI' in aircraft was always methanol/water, and not comparable)

speaking of true WI (if allowed) it would need engineering to evaporate mostly (and very consistently in that 'mostly' proportion) in the combustion chamber after compression has started
(that seems rather difficult, would an AFR probe be needed, and how then would all fuel be used at best efficiency ?)
though it would potentially allow increased CR at our chosen 'boost' pressure, which would contribute to efficiency, hence power
the octane-unlimited fuel may not benefit much in HUCR from the cooling of WI
and if the HUCR without WI is already very high it may be impossible to increase CR anyway, without constraining the valve motion
(current F1 engines are limited in CR by this)
any evaporation that happens prior to compression is displacing some of the induction air, and is rather counterproductive
(eg at minimising the supercharging power)

it's not clear that WI into the supercharger is of value in our fuel-limited formula ?
(WI into the cylinder is obviously better, but is clearly not allowed)

[Holm86]

Are we sure that the octane level is unlimited??

In the interview between Peter Windsor, Tim Goss and that Mobil1 guy they are talking about knocking reoccurring in the new engine formulae. And you reduce power by having to ignite later because of knock.

But I do think that WI could be a possibility on the new engines. I cant see that its forbidden.

[langwadt]

Are we sure that the octane level is unlimited??

In the interview between Peter Windsor, Tim Goss and that Mobil1 guy they are talking about knocking reoccurring in the new engine formulae. And you reduce power by having to ignite later because of knock.

But I do think that WI could be a possibility on the new engines. I cant see that its forbidden.

5.14 .2 Other than engine sump breather gases, exhaust gas recirculation, and fuel for the normal
purpose of combustion in the engine, the spraying of any substance into the engine intake air
is forbidden .

[WhiteBlue]

Are we sure that the octane level is unlimited??

In the interview between Peter Windsor, Tim Goss and that Mobil1 guy they are talking about knocking reoccurring in the new engine formulae. And you reduce power by having to ignite later because of knock.

But I do think that WI could be a possibility on the new engines. I cant see that its forbidden.

5.14 .2 Other than engine sump breather gases, exhaust gas recirculation, and fuel for the normal
purpose of combustion in the engine, the spraying of any substance into the engine intake air
is forbidden .

There goes the water injection, unless of course they inject the water into the exhaust and recirculate some exhaust.

[ozzimark]

The regulations do form an interesting loophole here.

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 we can't spray anything but fuel into the intake and there cannot be anything but the fluids entering the compressor exiting the exhaust.

However, since EGR and crankcase breather systems are allowed, that brings up the point that if an EGR system had some type of water injection, it could be allowed if creatively implemented. They key thing here is that spraying into the exhaust isn't expressly prohibited, but any sprayed fluids must go through the compressor inlet without being considered part of the intake stream.

The reduction in available oxygen per volume of gas is no problem, as there's no limit on airflow, but this would inherently increase the volume of gas that requires compression. It's hard to judge just through handwaving whether or not this system would actually allow higher CR to the point of being beneficial; water is heavy, these are all extra components that would be adding to the weight, and are susceptible to failure.