small point you only get two exhost cycles per revolution so half the engine displacement volume - but it is at high pressure. Actually you should think in terms of intake charge and then the reaction with fuel to determine the exhost mass.

 

Any plans to make a remote turbo setup for the gen 1 xB I've been looking but haven't found any?

 

I find it hard to take someones advice who spells exhaust "exhost".

 

Ya know you are the first to mention that and I have been spelling it wrong for years and thought it look weird. Thanks! And there is a temperature drop when the pressure drops but the mass stays the same.

 

...

 

i can't wait to see some numbers on this kit! Get a move on

 

Ran into some fabrication issues but they have now been addressed. Hope to have some updates soon for you.

 

thanks for the correction Skee... I wasn't worrying about that level of detail though... I just wanted to get the point across that the turbo gets no benefit from the exhaust being hot... quite the opposite, as hot exhaust is inherently at a lower pressure, as it is trying to get out of the exhaust tube (an open-ended container) faster. Bernoulli's principle - fast moving fluids flowing through an open ended conduit such as a pipe are inherently at a lower pressure than slower moving flows. happens to be one of the founding principles of aerodynamic theory and fluid dynamics. pressure only increases with temperature when the fluid is heated within a closedcontainer, as it is inside the cyliinder of a piston type engine, or the conduit through which the fluid is flowing has some kind of restriction or obstruction that severely limits the flow rate (no a turbine won't count as such if sized correctly).

remember pv=nrt? pressure*volume=moles of the gas*real gas constant*temperature. that is the basis of everthing going on.

damn i need to get back into building rockets... havent done it in so long!

 

FINALLY!!!

but man... when it comes to stuff like this, you either have to give us some kind of updates at regular intervals, or just not announce *ANYTHING* until its all done, dynoed and ready to sell lol. that second option is out, since you announced it was in development, so you owe us at least a periodic 'yes, we are still here... dont worry' like above lol

 

So is it the pressure of the exhaust gas that spins the turbine or the velocity of the gasses that spins the turbine? I think both and hotter gasses would have more pressure so that an insulated header leading up to the turbo would retain more of the temp thus more of the energy in the gasses and provide more boost energy to spin the turbo. Your point of the cooler running turbo is also a good idea to minimize the heat exchange to the intake air through the turbo shaft and it also reduces the thermal load on the oil cooling requirements. With the cooler temperature gasses further from the engine I would think that the only down side might be more turbo lag but once spooled up there should be plenty of cooler gasses flowing to keep the boost high.

 

I'm curious too... more pic's yo

 

pressure has very little to do with the turbine spooling... it is the velocity and mass of the gases that do the work. all that higher temperatures do is force the molecules of gas further apart when in a tube like the exhaust pipe, making the gas less dense. under these circumstances it is actually harder for the gas to spin the turbine.

come to think of it I have a perfect example. with rocket engines, there is a term known as Isp or Specific Impulse. it is used as a means of determining the efficiency of an engine, and is directly related to the velocity of the exhaust gas. Basically, the higher the value of Isp, the higher the potential velocity an engine is capable of, and the less propellant it will use to get there. the trade off is that as Isp increases, usable thrust decreases due to a number of factors, one of which is that at those higher velocities the exhaust simply doesnt interact with the engine long enough to impart much momentum. for these reasons, high Isp engines are restricted to operating in space only, as they cannot generate the thrust required to get a rocket off the ground. fascinating eh?

to bring this back to earth, high temperature exhaust is at a high value of Isp, thus the molecules wont have much time at all to impart momentum to the turbine, while the lower Isp, cooler exhaust hitting a rear mount turbo will have much more time to do the job... it has alot more torque! This is the primary reason the rear mounted turbo doesn't suffer from the lag that most people expect - not only does the cooler exhaust spool the turbine faster, but it can drive a much larger compressor stage to operating speed than a 'hot' turbo would in the same time. Bigger compressor=more boost... sooner.

ok that should do it...

 

Simular thing happens in sailing - you get more lift from cold air than warm air. That all makes sense and the rocket motor too and they also have issues with nozzle losses too. I imagine making the opening too small and you get higher velocity exhaust but you also get more friction on the nozzle - then taken to the extreem you have the ION drive engines that use very little mass in the propellent but push the particles out at very high velocity to make a small amount of thrust which is great for deep space flights.

 

Since we're on the topic of the ideal gas law, mass flow does have to do with spool; there's no doubt about that. But flow only accounts for "n."

n is fixed throughout the system. R is fixed. V is also fixed, aside from the expansion of the walls which is neglible. That leaves P and T. They both change greatly over the turbocharger. The exhaust pressure is a result of the temperature so that leaves temperature. If heat had nothing to do with anything, the temperature change across the turbo would be the same as the temperature change across an equivalent amount of piping in the exhaust and that simply is not true.

True, some of the heat is soaked into the turbo housing and radiated into the engine bay which heats the air and IAT and yada yada but the rest of the heat goes into spinning the turbine and a lot more of that spool is heat powered than is flow powered.

Consider a log type manifold. It'll spool a turbo up faster than a tubular manifold but no one is going to argue that a log manifold outflows a tubular manifold. The reason is that exhaust heat and pressure is higher as it enters the turbo to impart more kinetic energy onto the turbine.

Shaka, have you worked on stuff applying rocket science to our gasoline engines? I don't know nearly as much about rocket engines but as far as I understand, rocket engines work based on the principle of action/reaction, where subsequent gas molecules push off against previously burned gas molecules.

In terms of a car engine, being that exhaust isn't the driving force but a waste product, cooler gases at the end of the exhaust pipe would become back pressure and cause pumping losses. But since we're talking about turbo itself, which is driven by exhaust as a rocket is driven by exhaust it would seem relevant, except that the exhaust is a product of the rocket engine whereas exhaust is definitely not the product of the turbo so a low "Isp" wouldn't help the turbo drive itself. One thing that needs to be said is that hotter gases in the exhaust tract don't get less dense due to greater heat. They can't. The pressure of the gas is fixed until they reach the atmosphere. Thus pressure goes up as heat increases.

Well that's my explanation.

 

yay!!! late-night physics brainstorming!!! sleepy...


ahhh... remember though that we are talking about a flow rate... it shouldn't be just n but n/second. the addition of that one item changes a great deal...

you are going to have to enlighten me as to how heat is going to directly spin a turbine wheel... if *alot*more of the spool is heat driven than flow driven as you say, one should be able to get substantial spool even if there is minimal to 0 flow.

I am not going to pretend to know much about manifold types or their flow characteristics....

[EDIT]
damn... it just came to me after writing the last section.... it is likely that a tubular manifold behaves much more like a proper expander nozzle than a log type, at least at that point in the exahust system. that would explain why it flows better than a log, but cannot spool a turbo like a log.
[/EDIT]

now... I am in dire need of sleep(forgive me if this whole post is seriously disjointed), but it seems to me that you aren't seeing the system in the right perspective.

the thing is, that a car engine and exhaust system are directly analogous to a rocket combustion chamber and nozzle... the only real difference being that a car engine extracts most of the generated power to drive wheels (via the pistons) instead of directly generating thrust (matter of fact, with a little work, a car engine can in fact generate substantial thrust directly, but that is a topic for another time - hint: PDWE). all the driving principles are the same, only the minutiae of their application differs - there are certain classes of liquid fueled rockets that do in fact harness their combustion cycle to drive their fuel pumps (in most cases these are turbopumps ironically lol, though piston pumps are used in some). since the generation of thrust via the exhaust is of no importance, a cars' exhaust system can be a straight pipe, instead of an expanding nozzle (the purpose of which is to extract maximum momentum transfer from the exhaust to the engine by expanding the gas to match the ambient pressure outside as closely as possible) for example. you shouldn't be thinking of the car engine exhaust as a waste product... rather it should be seen as propellant/reaction mass that hasn't had as much momentum absorbed from it as possible due to poor nozzle design. if the car exhaust pipe was a proper expander type nozzle, there wouldn't be enough momentum left in the flow to drive a turbo.

ugh.. I trust you will let me know if this all made some kind of sense or is sleep-deprivation spawned gobbledy____... I'll probably see this post tomorrow night (the next time I'll have a chance to look... working ALL day) and say 'I can't even READ this!!!' trust me... it's happened before.

[/i]

 

Oh, it's comprehensible enough to me so no worries. I'm multi-tasking so I was afraid I was being incomprehensible.

Anyways, flow alone will move a turbine the same way that one of those spinning fan things would spin when you blow on it, and heat alone, with no flow, would NOT move. It's just that the heat gives a lot more energy to the moving turbine, and heat transfer only occurs because of the flow of exhaust over the turbine. You can't separate the two. You can, however, give one importance over the other. The majority of the energy in a unit of gas flowing through the turbo is in the form of heat energy. Consider the case of a turbo diesel. I don't know too much about diesels but some diesel engines run without throttle bodies. Effectively, they're at full throttle at all times yet don't boost full at all times. They only boost based on the load on the engine which generates a hotter exhaust.

But you know, in essence, I've come to think that we're saying the same thing. On a molecular level, the flow of molecules over the turbine would be super small collisions and the action/reaction couple would cause the turbine to spin. As heat is the kinetic energy of molecules, the transfer of kinetic energy is the transfer of heat. I know it's not quite so simple but on a larger scale, it seems right to me.

If you see differently, please post up. I'm liking this discussion on rocket engines.

 

sooooo anything new ?

 

The Test car is a friend of mine up here in Detroit. I havent heard anything for awhile from him. Maybe I'll give him a call and see whats up and how its coming along.

 

WOW! AWESOME KIT! Have you guys calculated the cost yet?

I hope there is a Mitsubishi Turbo option, I haven't done my research on this Brazilian turbo assembly yet... But still, it should be good since you're installing it in your R&D tC.

The one and only thing that gives me the "creeps" on that turbo is: That it might get seen by crooks and jack it off the car since it's mounted outside the engine bay...

How can this kit be "hidden" from thieves eyes??? (Insurance won't cover it...)

I'm WATCHING THIS THREAD!

 

just wanted to let you guys know.. Im still here.. just been too busy to post the last few days... lots of work drama has had me stressed out...

but just to add my $.02... if they see the turbo is outside the bay, they will just steal the turbo. if they realize it's in the bay, they steal your car. hmmm... I wonder which option I would prefer lol