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 Post subject: Re: Next Level TMIC cooling - Spray & Fan - Build thread
PostPosted: Tue Apr 16, 2019 10:18 am 
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Vehicle: MY08 XT (SH)

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My understanding is that pre-turbo and turbo insulation tend to increase responsiveness (rather than maximum HP) - assuming we take heat-soak issues out of it.

The theory being that less exhaust energy is being radiated through the metalwork (or used to heat up cooled metalwork) so more is available to spool up the turbine - up until the wastegate opens.

Once the wastegate has opened that would be governing maximum horsepower by bleeding off a sh!tload of "excess" exhaust gas. Once those maximum conditions are reached, any excess heat lost through the metalwork would be incidental compared to the bulk energy being bled off through the wastegate.


Post-turbo insulation gets a lot more speculative in terms of theories of "hotter faster gas getting away quicker" and so-on.

Having said that, less under-bonnet heat is a good thing, particularly next to the brake actuation hardware and under a top-mount intercooler.


My general theory on car mods is that areas of proven gains tend to be well-established facts and are commonly used, while the more fringe theories and internet debates tend to exist around issues with barely-measurable gains. Regardless of the truth of a given matter, it can be a guide to what is good value (or not) for car mods.

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 Post subject: Re: Next Level TMIC cooling - Spray & Fan - Build thread
PostPosted: Tue Apr 16, 2019 11:59 am 
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I Say: Plan for tomorrow,Live for TODAY!
Vehicle: MY12 XT

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@Yowie..... are you getting technical??

Thanks for the feedback guys, I agree post turbo gains could be debatable. There are tests that have shown turbo blankets do provide faster spool (dyno tested diesel motor), so it is proven that you do get some gains through faster spool. i.e. power sooner, which makes you accelerate sooner, therefore faster.

My brain is still thinking why would a turbo blanket, which you would think is the last part would provide gains at all..... as it would be extremely hot anyway.... Which the proven experiments shows that it does.

So the question is why wouldn't a dump pipe blanket keep it a little hotter post turbo ?? which in effect would keep more heat passing through at higher pressures just that little bit longer.

@Tobyo - heat shielding and keeping the heat in in the pipes are different perspective. Shielding is to stop heat damaging other components. Keeping the heat in helps the heat dissipating requiring less shielding, but keeps the heat in for faster spool.

If interested, I can track down the turbo blanket research that shows faster spooling times for a turbo blanket for a diesel motor (dyno tested).

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 Post subject: Re: Next Level TMIC cooling - Spray & Fan - Build thread
PostPosted: Tue Apr 16, 2019 5:39 pm 
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Vehicle: JDM SF STi Pure White

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Location: Germany
I'm thinking out loud here, this is based on my understanding of physics, i might be missing something as i haven't really studied fluid dynamics.

What came to my mind is the question why hot air would flow any better than cold air. Technically, if the air is flowing at, let's say, 100L/min, it doesn't matter if it's hot or cold air, it'll still be 100L/min. Sure, the mass will be different due to change of density, but that doesn't really matter post-turbo. Or does it?

Now this is where it gets interesting. If we look at it from the other perspective, we know that a certain mass of air can have a different volume depending on the temperature. Colder air is denser air, which in turn means that a kg of air will occupy less space when cold (844,67 Liters at 25°C, 872,98 Liters at 35°C, dry air).

Now, knowing this, what's better? Trying to keep the air hot as long as possible? Or actually trying to cool it down so that you can shove more air mass through the limited space of your exhaust? Remember, we're talking post-turbo air, at that point it's of zero use to us, we just want to get rid of it.

Does anyone know CFD good enough to simulate this?


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 Post subject: Re: Next Level TMIC cooling - Spray & Fan - Build thread
PostPosted: Tue Apr 16, 2019 5:48 pm 
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Vehicle: MY08 XT (SH)

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Perhaps lower mass of gas in the exhaust pipe saves on gross vehicle weight by a hundredth of a gram for better acceleration :P

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 Post subject: Re: Next Level TMIC cooling - Spray & Fan - Build thread
PostPosted: Tue Apr 16, 2019 6:24 pm 
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Does this mean I need to design a A/C evaporator to squeeze inside my exhaust system :dontknow:

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 Post subject: Re: Next Level TMIC cooling - Spray & Fan - Build thread
PostPosted: Tue Apr 16, 2019 6:41 pm 
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Vehicle: JDM SF STi Pure White

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Make your exhaust look like this?
https://vulcanfinnedtubes.com/wp-conten ... -thumb.jpg


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 Post subject: Re: Next Level TMIC cooling - Spray & Fan - Build thread
PostPosted: Wed Apr 17, 2019 2:00 am 
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Alternatively - It may have the hot air ballon effect.... It makes the car lighter with the hot air so it goes faster!.

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 Post subject: Re: Next Level TMIC cooling - Spray & Fan - Build thread
PostPosted: Wed Apr 17, 2019 10:28 am 
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Location: Brisbane
:lol:

----

Edit - perhaps Tobyo could rig his AC-powered exhaust chiller to only kick in when the extra downforce from extra mass is needed on the race track? Kind of like the banned active aerodynamics from those days of Formula 1 except pointless.

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 Post subject: Re: Next Level TMIC cooling - Spray & Fan - Build thread
PostPosted: Wed Apr 17, 2019 12:27 pm 
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I Say: Plan for tomorrow,Live for TODAY!
Vehicle: MY12 XT

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Phrewfuf wrote:
I'm thinking out loud here, this is based on my understanding of physics, i might be missing something as i haven't really studied fluid dynamics.

What came to my mind is the question why hot air would flow any better than cold air. Technically, if the air is flowing at, let's say, 100L/min, it doesn't matter if it's hot or cold air, it'll still be 100L/min. Sure, the mass will be different due to change of density, but that doesn't really matter post-turbo. Or does it?

Now this is where it gets interesting. If we look at it from the other perspective, we know that a certain mass of air can have a different volume depending on the temperature. Colder air is denser air, which in turn means that a kg of air will occupy less space when cold (844,67 Liters at 25°C, 872,98 Liters at 35°C, dry air).

Now, knowing this, what's better? Trying to keep the air hot as long as possible? Or actually trying to cool it down so that you can shove more air mass through the limited space of your exhaust? Remember, we're talking post-turbo air, at that point it's of zero use to us, we just want to get rid of it.

Does anyone know CFD good enough to simulate this?



Just responding - Hot air at high temps provides greater pressures. So a cold 100L uses less space than a hot 100L, that is it has a hotter air has greater volume. This is great for spooling turbos, BUT not for intake it works the opposite way due to oxygen volumes. The colder denser (less volume) air contains more oxygen which is great for power.
The hotter expanded ( more volume) air is larger, so creates greater pressures to spool faster.
Nothing to do with fluid dynamics for this part, just simple physics.

But you are right, in that post turbo, it would be great to see what the effect of maintaining the pressure/heat has on upstream flows.

Hence my original question of why a turbo blanket works (which has been proven on a dyno), which still baffles me to be honest.
With the following question of why do I feel a difference after the down-pipe blanket ??

The discussion has been great so far !

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 Post subject: Re: Next Level TMIC cooling - Spray & Fan - Build thread
PostPosted: Wed Apr 17, 2019 12:43 pm 
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A turbo blanket works because the hot exhaust gas is still capable of useful work while it is in the "snail shell" of the cast iron turbine housing (yet to finish pushing the turbine blades).

Absent a turbo blanket, the spool-up will be slower because some heat energy is being used to re-heat the cast iron housing.

With a turbo blanket, the turbo housing has retained more heat from immediately prior engine operation in the first place, so more of the exhaust heat energy from the current stab at the throttle contributes to spool-up.

(once at peak power the wastegate is determining how much exhaust energy is converted into useful work on the turbine, with the heat lost through non-insulated turbine housings etc being incidental).

--

On a related note, running high coolant temperature contributes to better fuel economy because less burning fuel energy is being lost in heating up the (already hotter) head & cylinders. That's why OEM passenger cars run high coolant temps.

Racing engines run cooler coolant temps as knock-control and to improve air density for maximum power.

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