Turbo Heat Shield

[khunjeng]

if the turbo is hotter how will the actual exhaust gases be hotter? its coming from the engine and spends 1 millisecond in the volume of the turbo - after which it may be 0.1 deg hotter but thats not going to matter since the gas has already done its work.

The larger exhaust works to increase the speed of the gas because there is a larger volume for the gas to expand into as it passes through the turbine - nothing to do with the temperature (except for the fact that the gas will be cooler due to the expansion).

there would be no reasonable way to make the exhaust gas hotter since it gets its heat from the compression and combustion within the engine cycle.

hotter was bad word usage...hotter in comparision to a turbo without the insulator as it just radiates heat...thats why you might want a shield and the initial question.

nothing to do with temp? when the gas expands and cools down...where does the heat go? in fact what do you think the heat is used for? ...its no suprise it expands..its deisgned to do it. The gas will be cooler...but thats not the aim...the aim it to turn the turbine using, partically, the heat generated during the process.

You seem to have some idea...so do you want me to go into the relationship between Heat/Pressure/Volume? we have sort of covered it...all of these are used to make the turbine spin. Its fact,mate...designed many years ago by people smarter than me and I even looked it up in my old physics book to be certain.

In short, gas temperature, pressure, and volume are all related. Compress a gas (reduce the volume) and pressure and temperature goes up. Let it expand, and temperature and pressure go down. Increase the temperature, and the pressure goes up (in an enclosed space) or the volume goes up (it expands). Finally, gases want to flow from a high pressure area to a low pressure area, and the greater the difference, the bigger the push. (Pop a baloon, little bang. Pop a welding O2 cylinder, big bang)

read up on the The Ideal Gas Law. then relate it to the otto cycle in a 4 stoke engine...it will answer the aparent mistery.

[SKY 34]

kunjeng is correct on the temperature volume and pressure relationship

in diesel engine you don't need a spark plug as the diesel will detonate on its own due to the pressure..

if you have water under high pressure it'll boil on itself

however I'm not sure if heat loss is going to affect the energy change much...the exhaust spends only a split second in the housing before going out and the housing and dump pipe would eventually gets close enough to the exhaust temperature under operation, so will the dump pipe...

maybe as the engine go from cold start there is a large temperature gradient across, however at constant operation I'd think the difference is hardly noticable

unless you kinda go hard acceleration and sudden slow down... and hard acceleration again...sorta cycle thing unless on track don't think will ever go into such extremities

with heat shield the temperature across will be higher.... without heat shield the temperature will be lower, gradient remains the same

I think the main key to turbo operation is the nozzle size, the inducer and exducer ratio, how small the size of the nozzle when exhaust come into the housing and how big the exducer is..and the exhaust to compressor ratio...

and with regards to the blanket cracking the housing, that will happen if you dissipate heat too fast...if you pour hot water into a glass, empty it and immediately put ice in it..the glass will crack, try it at home~~...so retaining the heat and slowly dissipating it will not cause the housing to crack...if temperature is too hot, it'll melt but I think housing are of course design for these temperatures..

[khunjeng]

Its all about keeping the air in a high energy state to allow easier transfer of kinitec energy.

I dont have a blanket...dont care...this is all just theory. Remembering that many people use these.

it might be more bewteen runs..to keep the turbo hot rather than while driving.

[AndrewD]

The larger exhaust works to increase the speed of the gas because there is a larger volume for the gas to expand into as it passes through the turbine - nothing to do with the temperature (except for the fact that the gas will be cooler due to the expansion).

lol have you considered the mass conservation principle? cause that statement is wrong.

essentially in a closed system (e.g. a pipe without leakage) the mass of the substances remains constant.

it follows then that the mass flow is also constant (i.e. now fuel or air is either injected or lost between the inlet and outlet of the turbo).

hence: massflow at point 1 = massflow at point 2

also: massflow = density x velocity of gas x cross sectional area of pipe.

so what actually happens when you increase the size of a pipe for the same mass flow is a REDUCTION is gas velocity, which is accompanied by a reduction in pressure drop for the same length of pipe in comparison to the smaller pipe.

and as far as turbo blankets design for turbocharger performance is also crap. they limit at best the engine bay temperatures. cause increased temperatures within the bearing centre and oil coaking on shut down. WHICH is BAD! however if you have a water cooling circuit it will be ok, however take longer to cool.

Edited November 14, 2006 by AndrewD

[khunjeng]

so what actually happens when you increase the size of a pipe for the same mass flow is a REDUCTION is gas velocity, which is accompanied by a reduction in pressure drop for the same length of pipe in comparison to the smaller pipe.

thats right. so the reason this helps ur turbo spool is because you just increased the pressure differnece between the inlet and outlet of the turbo...Heat/Pressure/Volume its all related.

as for the blankets...yeah I rekcon you just need a shield for shield heat from ur bay...lol I think that was the topic of the post...

[AndrewD]

doesnt mean that increasing the pressure differential is a good thing. yes it helps 'spool' the turbo, however the pressure ratio may now be such that the turbine operates in an inefficient range.

[nizmokid]

http://www.horsepowerinabox.com/ and $198 and if you say you are from SAU they give you a small discount. well they did me!

[khunjeng]

doesnt mean that increasing the pressure differential is a good thing. yes it helps 'spool' the turbo, however the pressure ratio may now be such that the turbine operates in an inefficient range.

its all theory mate. ..but I would assume the mods we are talking about are only minor and wouldn't have a massive impact in the presssure ratio and therefore not move the compressor efficency a huge amount...but I'm no expert.

[Cubes]

Ask Roy what happens when you don't run a heat shield and a heater hose develops a small pin prick hole spraying a fine mist of coolant/glycol.

Coolant/glycol just happens to be flammable when sprayed in a fine mist.