A HTC coated header runs incredibly hot and retains heat within the exhaust gases MUCH better than any cast iron manifold..........I disagree that "heat makes the spinny thing go around"......it is exhaust flow that spins the turbine and the hotter the gas, the faster it moves......however, retaining heat in the exhaust is only one factor in achieving high velocity........if you retian excess heat at the expense of good port velocity, then you are wasting your time worrying about heat..........we want the highest velocity with out ANY compromise to flow.........move the exhaust faster through the header and it WILL be hotter at the turbo.........I still maintain that good scavenging of the cylinders is essential in achieving peak power and efficiency and these manifolds do not allow for ANY scavenging of exhaust gases to take place..........unscavenged cylinders can have a lot of residual exhaust gases that dilute the cool, fresh intake charge and lower the combustability properties of the intake charge.......the problem gets magnified on a turbo charged engine because you have device force feeding air in but nothing to aid in speeding up the air out......

That is a very nice header but it is not the one I saw.........the header I saw mounted a single turbo in the stock location on a 2nd gen........

 

Jerry Jardine, Jardine Headers, told me, 2 years ago at May Maddness, about one he was going to manufacture. Said it gave the engine a whole new exhaust sound - like a V12.

 

Hmm.....I checked out the Jardine website and there was nothing there about a CTD header......

 

Don,
What are your thoughts about any benefits associated with equal volume "runners" from each cylinder tothe turbo in an exhaust manifold? Would there be any benefit from evenly timing the exhaust pulses to the turbo?
Mark

 

CTD Nut, you are both 100% correct and 100% wrong on separate points. A coated header is in fact just as you say.... PERFECT... it keeps the heat in the exhaust gas, 100% correct.


BUT... You are dead wrong about heat not driving the turbine. I know it is difficult to comprehend, but the turbine of your turbo is just that.... its a gas turbine. It works by extracting Enthalpy ( a unit of energy per pound of a gas or vapor) from your exhaust gas. It is a heat recovery device. The velocity is created in the turbine housing where the exposed restricted area of the turbine wheel opens up to the atmosphere. The rapid expansion and cooling of the exhaust gasses converts this energy change into velocity. This velocity energy is then converted to mechanical energy by reaction forces in the turbine wheel. This velocity created in the turbine is hundreds of times higher than the velocity in the manifold or header, thus making the manifold/header tube velocity negligible. The enthalpy is a direct function of HEAT. More heat, more enthalpy. More enthalpy, more energy available to convert into velocity in the turbine and thus make more power in the turbine, which thus drives the compressor and gives you more boost sooner. This is basic thermodynamics and is unarguable. Do some research on gas turbines or steam turbines, and it will explain it far better than I will attempt to in a post on the diesel forum.


AS for scavenging of exhaust gasses on a turbocharged diesel, this is myth. You are dealing with a system, which operates its exhaust system at high positive pressure. Any small negative pressure wave pulsations are totally negated by the turbine sitting there backing up pressure in the manifold/header. Thus exhaust velocity BEFORE the turbine becomes totally irrelevant. Turbocharged engine 'scavenging' comes from a positive intake runner pressure and an open intake valve occurring at the same time as an open exhaust valve, not from exhaust header negative pressure pulsations as in a naturally aspirated gasser.


Kevin

 

Good point. Hadn't thought of that, I was thinking more about steady state operation and efficiency than response time.

 

Kevin,

Thanks for the science lesson on turbines......I did not realize it was enthalpy alone that actually drives the turbine - I thought exhaust flow was a factor too.......I really do learn something new every day - especially here!

One point I do wish to debate further is the exhaust port velocity.........If you could run a larger exhaust housing that had a lower drive pressure, could this not take advantage of some increased port velocity that a header could give?........in other words, lower drive pressure could mean less of a choke on flow........In theory, you could deliver more, hotter exhaust gas to the turbine quicker and reducing the lag that a bigger housing can create.......

Also, when in the exhaust stroke is the intake valve open to pressurize the cylinder?.......Even though it is pressurized, could the exhaust port still not benefit from smoother higher flowing exhaust if the restriction could be reduced at the turbine?

 

Well, if you ran a larger exhaust housing, it does lower the drive pressure. And lowering the pressure in the manifold will increase the volume of gasses flowing. Since mass flow is constant, and the pipe size is constant, this would increase the velocity in the runner and exhaust passageways. But, this is still such a totally small percentage of the velocity generated when the gasses expand in the turbine section that it is negligible. To put numbers to it, the velocity in each runner of the manifold is around 50 Ft / sec, while the velocity leaving the tip of the turbine blades is approaching 1,100 Ft/Sec and depending on the diverging section of the housing could perhaps exceed this amount.


And as for less choked flow ( the flow is not actually 'choked' in thermo terms, since that would mean its at the speed of sound, but I know what you mean, restricted lets say), the lower drive pressure would make this worse, double. Double worse because now the velocity is higher AND the volume flow is higher. To use an example from the power station, two main steam lines carry steam from the boiler to the turbine at 2,750 Psi and 1,000°F. These lines are each 12" ID. Now after the High pressure turbine the steam is taken back to the boiler to be reheated before coming back to the intermediate pressure turbine. The mass flow is the same, but now the pressure is down to 600 Psi. To have the same velocity, these intermediate pressure lines are now 30" ID. Taking it further, after leaving the intermediate pressure turbine the steam goes to the low pressure turbine at 175 Psi, now the line is 5 FEET in inside diameter......

When mass flow is constant the following is always true:

Pressure drops, volume increases, and with constant pipe size then velocity increases... so to keep a reasonable velocity the steam lines had to keep getting bigger and bigger.

On our trucks, considering a given mass flow and constant exhaust pipe size, dropping exhaust manifold pressure increases volume flow and velocity, which would cause higher friction flow losses. But lowering exhaust manifold pressure (drive pressure) however GREATLY reduces the pumping losses the engine incurs and so it usually results in more HP, but at a cost of a more laggy turbo (hint, all of the information why the turbo is more laggy with a bigger housing is in the above info too …)


Kevin

 

Yikes!!......I had to read that post a couple of times over!! ........I get it, though!.......Very interesting read........

Are you suggesting that perhaps the only possible gain that a header could offer over an iron manifold on our CTD's is that the header would retain more exhaust heat to deliver to the turbine? Is the added heat retention enough to justify a header or is it negligable?

I'm interested in your thoughts as nobody here has touched on this topic to my knowledge.

 

Yes, about the only real gain is the retained heat in a header.

While it is moslty true that a header cant be tuned with a turbine in the way, it is not 100% true. Some gains can be tuned but the gains would be for a specific engine, rpm level, and parts combination.

When we add in late fuel dischare with say a pulse duration that is to long.... we always pick up turbine rotor speed and boost. The reason is the fuel is burning later in the stroke and adding heat. Heat moves the turbine.

Don~

 

Never thought about that, but I guess that's holding true for the common rail's isn't it. Those duration boxes are smoking turbo's left and right
Chris

 

Yes I do think there are other advantages than heat retention and heat response. At the higher power levels, I feel the exhaust port and manifold do in fact pose a restriction. I don’t think that a header would be much better than a manifold on a 350 HP unported engine. But 600+HP with a nicely ported exhaust port, then the manifold could pose an unnecessary restriction. Manifold restriction is totally disadvatagous, since you incur additional puming losses, but the turbine does see any additional pressure/temperature (enthalpy) cause it was lost on the way.

You need to make sure that there is enough volume in the header though so that each cylinder's exhaust pulses are smoothed into a more steady state flow for the turbine. That is the one concern I have with the way that gentleman made his on that web page.


Plus it'll take about 20 Lbs off of the front of our already too heavy pickups
Not to mention they are gorgeous.


Kevin

 

Headers are notorious for cracking, same with our stock manifolds. What's going to happen to these thin walled headers that heat up and cool down super fast unless a guy can figure a way to let them move without cracking?

 

Stainless Baby, Stainless!!

 

Duh, I never thought of that. Good point don.