what are your guys opinions on turbo heat wrap? i've heard the stuff is both bad and good but never heard any reasons for either. any input would be appreciated.
It makes sense to me that one of the purposes in the exhaust system is to carry heat away from the engine. The best way to do this is by NOT allowing much of it to escape through the pipes.
The problem with the wrap on the turbo is that it's large and is a thick metal...so it absorbs a lot of heat. Therefore I think you'd shorten the life of the turbo to wrap it (turbine side)
I notice you don't mention the lifespan of the turbo seals.
You also don’t address the fact that the hotter the turbine side is, the hotter the compressor side will be…and the hotter the intake air will be.
Thermal expansion is NOT the biggest factor in creating energy in the turbo. FLOW is the biggest factor. If you disagree, try this:
Get a turbo on a bench and put on an intake pipe and a downpipe. Then heat the turbine with a torch to the point it glows red….and see if the turbine will even turn one time on its own. Flow is most important, not heat.
You will gain much more energy by worrying about keeping intake temps lower than you will by worrying about thermal expansion. And to keep intake temps low as possible, you need to keep the exhaust heat in the exhaust gasses…and send them through the pipes, out of the area.
Technically, thermal energy is a bigger contributor to the complete equation. The flaw in that "bench" test is that with no flow, it will not work at all. The engine will always flow something, though, as long as it is running. It also produces a great deal of heat. Coating piston decks, valve faces, and wrapping primary tubes helps to deliver more of that energy to the turbine, as opposed to heat soaking engine components. Flow is a big part of the end result, but heat enery is bigger. Try flowwing huge air through your turbo using tight primaries and placing it several feet further away. Without insulating that heat, you'll hardly get the turbo to spool. Even if you corrected the pipe size to reduce pressure drop over distance, it still wouldn't do the trick. Heat energy drives the turbo hardest. Wrapping will enhance performance, but it may distress parts more, leading to shorter service life. Pick your poison.
John
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Wood/Anderson Racing Development: j.anderson@wardev.com
The example I gave above was to show that the thermal expansion of air inside the engine, turbo and piping will NOT turn the turbo at all. It is the flow of air through the turbo that turns it.
If we claim thermal expansion is the energy that turns the turbo then it must be that the air in the combustion chambers becomes hotter as it gets into the turbo and expands, creating more pressure to turn the turbo. Is this your side of this theory?
I don’t know if you’ve read Maximum Boost, but I don’t see ANY mention of a turbo getting its energy from thermal expansion…but I do see mention of turbo inlet pressure and flow rates.
I never said thermal expansion; I said thermal energy. Heat is the contributing factor, not gaseous expansion. I do have the book; as well many other books. It makes mention of thermal energy and its contribution to enhanced turbine efficiency. Apart from the heat issue in the turbine side, the compressor side of the turbo does not suffer from heat soaking all that much. An intercooler is the key to pulling the added heat of compression out of the charge air, as is using a cold air intake to pull in the coolest air possible, anyhow. The air in the compressor side is there only long enough to absorb a small amount of heat from the surrounding surface; the heat it does possess is a function of the air molecules friction with one another due to the great amount of work performed on it. These are all very elementary physics and thermodynamics concepts that any other engineer could validate. Added heat on the turbine wheel means added work on the turbine wheel. The more work put on the turbine, the more work performed by the compressor; period. The torch on the undriven turbo is just plain out of left field. Try driving it with a given volume of gas with given specific gravity, then do the same thing with the same turbo, but with the gas at 400 degrees higher than previously. Nitrous doesn't just do a great job of spooling big turbos because of the added combustion pressures, but also (more so) because of the added combustion temps.
John
__________________
Wood/Anderson Racing Development: j.anderson@wardev.com
Last edited by king_johnthegreat : Aug 7th, 2003 at 12:27 AM.
Originally posted by king_johnthegreat I never said thermal expansion; I said thermal energy. Heat is the contributing factor, not gaseous expansion.
Ok, then explain to me how heat energy, without flow or expansion, will turn the turbo.
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Originally posted by king_johnthegreat I do have the book; as well many other books. It makes mention of thermal energy and its contribution to enhanced turbine efficiency.
Page number??
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Originally posted by king_johnthegreat Apart from the heat issue in the turbine side, the compressor side of the turbo does not suffer from heat soaking all that much.
So you’re saying that the compressor side gets too hot to touch just simply because it’s a compressor? Do you really think that a compressor making 7psi will generate that much heat.
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Originally posted by king_johnthegreat An intercooler is the key to pulling the added heat of compression out of the charge air
That’s after the fact that the compressor side of the turbo puts heat into it. And that heat is primarily generated from the exhaust side of the turbo.
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Originally posted by king_johnthegreat Added heat on the turbine wheel means added work on the turbine wheel. The more work put on the turbine, the more work performed by the compressor; period.
So if you have a car on a dyno and boosting, then put a torch onto the turbine housing, you will be making the turbine work more, therefore making the compressor side work more?
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Originally posted by king_johnthegreat The torch on the undriven turbo is just plain out of left field.
The point is that heat, without flow, will not turn the turbo. PERIOD!!!
Originally posted by javierb14 a well designed turbo exhaust manifold will optimize everything that gives a turbo better performance.....heat, pressure, and flow. to say flow is the biggest contributor isnt correct. if this were true then "log manifolds" and the poor flowing cast OEM manifolds wouldnt work that well
They don’t, compared to a better header type of setup.
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Originally posted by javierb14
[b]u should read the introduction of corky bells book....
"a turbocharger is a simple device. it is nothing more than an air pump driven by energy remaining in the exhaust gases as they exit an engine.of the energy released in the combustion process, approximately 1/3 goes into the cooling system, 1/3 becomes power down the crankshaft, and 1/3 is dumped out the tailpipe as heat. It is the last third that we can use to power the turbo.
So you ignore the word dumped in that paragraph? Dump is a verb. I won’t resort to defining this as a way to insult your intelligence, as I do not mean to in any way. Anyway, it takes energy to dump the heat.
In short, as I’ve heard before, energy cannot be be created or destroyed. The fact is that the turbo is not a heat exchanger.
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Originally posted by javierb14 basically, optimize the energy transfer (heat, pressure, and flow) to the turbine and u will get better performance.
Transferring heat to the turbo is important to get it away from the engine, but likewise, you need to get it through the turbo as efficiently as possible also. I do notice you say optimize, rather than reduce or increase…I agree with you on that point.
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Originally posted by javierb14 i like a good flow.....thats why we use a real merger collector in our manifolds.
I agree here also…I feel that flow is most important, as that’s what turns the turbo.
About your pics…they look pretty nice compared to most I’ve seen. However, if you want to see some welds on the that look even better, send me the parts for one and I’ll work it up for you J
I can see that the fit is nice prior to welding. Why don’t you just purge the inside and put a full penetration weld on it?
hey javierb14, i would take engloid's offer on this! he does some awesome work and fabricating. i've seen some pictures of some intake manifold work he's done for the vg30et on the earlier 300zx's and it is top notch.
The few lines of mine you didn't quote stated in no fewwer words that the turbo will not turn over most efficiently (In terms of generating boost) without either flow or heat. I never said heat would turn the wheel by itself. I said that it would make the greatest contribution to making the turbo more efficient and responsive. You ask where in Maximum Boost this mentioned; here you go: Pages 117, 119, and 129, just to name a few.
You quoted someone else who paraphrased a passage from Corky Bell, trying to correct them for saying that exhaust heat is a portion of raw energy dumped out the lait pipe; I ask you: how much energy it takes to exhail? None is the answer, you relax to let the gas out. The engine does not work to allow gas to escape, the exhaust system operates off of residual rotational motion from the crank, and reciprocating motion of the rods/pistons. Heat energy is much easier to lose than maintain, as well, so the fact that exhaust exiting the tail pipe is still warm means that there is more energy left over that the turbo could possibly have made better use of. He (Corky) also states boldly that heat energy works to eliminate a large portion of the lag a turbocharger encounters while spooling to create viable boost pressures. Without the heat (As I tried to explain with my bench test), you would suffer from horendous lag. Again, you tried to use the torch for a testing tool; not smart. Let's just stop with the pyromania. That whole energy cannot be created nor destroyed thing; that's actually a quote about matter. Matter can neither be created nor destroyed. Energy has no mass, so you don't really create it; you generate it, expend it, transfer it, store it, lose it, or gain it. It can be conducted, inducted, insulated, shared, so on and so forth.
Yes, the compressor side gets very hot to the touch because even without using hot exhaust gases to drive the comp wheel, compressing air generates a great deal of heat. The less efficient the compressor wheel, or the more pressure you ask it to generate, the hotter it will get. 400 degrees is possible from a T04E wheel generating 30 psi. My T04E 50 trim can make 248 degrees at 18 psi. You think that might burn your hand? That is from an electrical shaft drive for flow testing, too, not because of the turbine side. The bearing housing has oil and water running through it on many turbos, do you think the oil would withstand coking if the turbine side could heat the compressor side to that temperature? Not likely. Try sticking your hand on the valve cover after a long drive, and then blame it on the exhaust gases in your crank case when you burn your hand.
I could start using equations to explain my points further, but you'd probably try to use a torch to solve them. The point is, unless you can pay someone to agree with you, anyone with half an engineer's whit would likely not. Thanks, though.
John
__________________
Wood/Anderson Racing Development: j.anderson@wardev.com
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