forced induction & torque converter

[phaedrus]

All well said Guy. Nice to see you again, so to speak.

There were (are) two ideas here about tuned intake and exhaust. One is to make an Nth engine more efficient, the other is to make more power. I am not interested in making more power as the 6-1 is not designed to make appreciably more than 6 hp at 650 rpm and my observations are that if it does it's dangerous. And then too, 6 hp is plenty, imho.

I agree with what you said, but would point out that making an Nth engine more efficient saves fuel. By transferring the pumping work from the flywheel to the waste acoustical energy a saving of something like 750 watts of power may be possible. This figure is mooted as an estimate only, but it's not simply a guess.

Most of the fluid loss in a diesel occurs in the exhaust - hence a tuned exhaust is the most profitable aspect to address. In an ideal engine one would exhaust to vacuum. In the case of the lister type 6-1 exhausting through 2" schedule 40 pipe the numbers for my setup seem to be as follows: exhaust event = 325 hz ,  pipe crossectional area = 3 sq inch, exhaust pipe length = 4.345 inches, exhaust temperature = 400C

I used the cavity resonance calculator found at

 http://hyperphysics.phy-astr.gsu.edu/hbase/waves/cavity.html#c4

and the numbers I give here are a little rough - for example the area is not quite precise. The cavity in question is the cylinder itself - and I'm making assumptions about valve timing and overlap, etc. - the pipe length calculated is only approximate - but it gives an idea what is, I think, realistic. A second chamber, or "cavity", is obviously desirable for practical reasons - and it ought to be possible to calculate that so that it interacts to improve resonance and efficiency further as well as silences the gas pulses to minimize noise.

I am a bit out of my depth in this matter - but at some point in the process it may be that I'll either determine that tuning the fluid flow paths is useful or not - and, if worthwhile, by what number, ie how many watts are there for free. I pay over a grand for a couple of hundred watts of solar panels - this looks like it is worth investigating and, if the numbers crunch right, physical testing of theory and so on.

It's an evolving process...  Best,  P

[mike90045]

The cavity in question is the cylinder itself

 
I thought (since the piston "force evacuates" the cylinder) that the next thing in line (exhaust pipe) would be the item to "tune" so it could help draw from the cylinder, and relieve the engine of that exhausting work.

Or maybe I'm not following this exactly.  Mike

[lev-l-lok]

I know its gas motor tech, but, would a stepped diameter (header) type exhaust pipe work? It could reduce pipe length, and arrive at the same torque / RPM point, before emptying into the expansion chamber / muffler. Are there any programs for this type of exhaust?

Paul

[Doug]

NOx production is a byproduct of high temperatures, to minimise NOx production you are really cutting the mechanical efficiency of the motor...

As far as charge tuning goes, the CS has relatively slow piston speeds (easy to work out with a bit of math mean and peak piston speed) and relatively low mean and peak gas induction speeds...

Tuning intake and exhaust works better at higher gas speeds, think japanese 2 stroke motorcycles, put a spanny chamber on the exhaust and at the right rpm range (don't forget piston valve 2 stroke = wads of valve overlap too) you can actually suck intake air in with the exhaust gases...

I have to ask this then Guy:

At lower power levels when we are burning less fuel we have more oxygen than we need for complete combustion so how does a little dilution hurt? And it requires heat energy to fuse N and O so by reducing the the amount of free O ar we realy doing that much to reduce efficiency? We are still going to produce X number of BTUs in combustion are we not?

Doug

[GuyFawkes]

NOx production is a byproduct of the heat of combustion inside the engine.

A well tuned engine chucking out the power produces a lot of heat, and therefore a lot of NOx.

Limiting Oxygen intake ALWAYS effects combustion, you can't guarantee that every droplet of fuel will meet a suitably sized clump of oxygen atoms AT THE RIGHT TIME if you do anything to limit oxygen, eg EGR, so you get a DIRTIER exhaust in all other areas except NOx and lower power.

Limiting Nitrogen is the way to go, but since it constitutes 70% of intake gases.........

My take, NOx on a 6 bhp diesel simply ain't that bad, there are worse byproduct from a badly tuned engine IMHO.

CO2 is the new NOx, just a boogeyman

[Doug]

OK you make sence.


Doug

[phaedrus]

Yes, Mike, you got it - the idea is to use the energy in the exhaust to "suck" the piston up. Simarly the idea in the intake side is to push the piston down using the same waste energy. In actual practice it may still use energy from the fuel-combustion-flywheel source, but it will use less. This would, of course, result in slightly less fuel used to make a given output, and provide a bit of altitude compensation - also with slightly less fuel used per kwh. Like I said, I pay over a thou for a couple of hundred watts of solar PVs - it's worth checking out this much cheaper "source", I think.

I found a german engineer who designs exhaust systems and am trying to interest him - I'm way out of my depth here. He has clearly got this area of engineering down cold.

 I also found some hotrodder sites with calculators - and these together with some physics of wave stuff that I've read says that a 6-1 running at 640 revs ought to have a header pipe 58.567 inches long, if it's made from 2" ID pipe. I think that, at the opening in the header a cone at about 10 degrees of convergence ought to transition over another 12 inches or so to a large chamber - 100 gallons or more, and from there to the exhaust stack. I think that a large conventional muffler with the inlet axis at 90 degrees from the cone-header axis ought to lead into the stack from that chamber. The cone reflects a low-pressure wave back down the header to the piston crown... It appears that the header-cone area ought to be insulated to keep it hot - all at one temperature because the speed of sound's important to the calculations and depends on temperature. "Rogue" waves inside the tank ought to be damped , perhaps with large pieces of perforated sheet metal. This is preliminary and largely opinion at this point.

[Doug]

Been reading the same sort of things as you but the nukber I read lead me to believe the exhaust header should be a lot longer.

Different formulas lead to wildly different lengths for intake and exhausts I'm confused.....

[phaedrus]

Me too!

I have noticed that new problems, new to me anyway, tend to follow a pattern, In the beinning they are deep mysteries, then they break into pieces and confusion and seem hopeless, and then, if you keep pounding on the problems, they gradually clarify and resolve and re-unite to seem quite simple.

The empirical formulas are, most of 'em anyway, are made for hotrod engines with lots of valve overlap, and for performance, eg power only, not for economy of fuel usage.

In this case one would desire to have a long duration low-pressure wave reflected back into the cylinder through the still open exhaust valve with the peak of the low pressure wave coinciding roughly with mid-stroke, so that the lever arm of the crank can transfer the energy to the driven load most effeciently. - That's just got to be a formula specific to low speed diesels...

[biobill]

Back in the day...... I remember reading in either the Piper Tuning Manual or Scientific Design of Exhaust and Intake Systems, the author bemoaning the fact that you could tell when you had your plumbing perfect because there was no practical way to fit it on your vehicle. He mentioned how nice it would be to tune a single speed stationary engine where 20 odd foot intake/exhaust runners wouldn't be a problem. I was all about hp/lb back then so "stationary" didn't compute, but it might provide some good mental exercise. If successful, should it be relabeled a 6.73/1     

[Doug]

uh hum.....

So I'll keep reading and looking for a formual that produces a long runner on a high compression low speed engine.

[aqmxv]

I understand some of this branch of physics from exposure to music instrument and tuned intake theory (on small two-strokes).  You're barking up the right tree with your tuning ideas.

As for header length, remember that different formulas will probably be assuming a different desired harmonic for the header tube length calculation.  Car engines commonly use second or fourth harmonics for the header pipe length just because they don't have room for the amount of pipe required for a first order harmonic system.  The lower the harmonic order, the more energy you'll have available to get the exhaust gas out of the engine.

Remember also that you want the low pressure area to be at the exhaust valve when the valve is opening, and that you're using closed pipe formulas, not open pipe formulas, because the cylinder (on the other side of the exhaust valve) acts as a resonance damper.

[Doug]

Thank you:

The latests calcuations call for a 35.5 foot long intake runner using the primary wave. 1300 RPM


This is realy long, even if EMT is only 15 dollars for 20 feet.


More thought and theory required

[aqmxv]

Yes, I estimated it at around 30 ft without doing any math.  35 ft strikes me as likely close to the right number.  FWIW, you'll get more performance/efficiency improvement from doing the intake side first (only have 15 PSI maximum pressure differential to work with, so anything you can do on the intake side is worth power/efficiency).  Advantage to doing the intake first is that you don't have to run metal pipe the whole length (can use thinwall PVC after about 5 feet or so), and there's no funny physics due to the speed of sound changing in the exhaust gases as they cool off while going down the pipe.

[mobile_bob]

fella's,

in theory your 30-35 ft pipe should work, but in practice it won't
the problem is the frictional losses in that length of pipe will overcome any gains you hope to gain.

If you do a search i think you will find that GuyF wrote a piece on this topic a year or so back
that sites the frictional losses of a long pipe.

the above relates to the intake runner

the exhaust runner will also be problematic for the same reason of frictional losses, and the loss of temperature
alters the flow.

probably easier to gain the hp by just buying a larger engine to start with, or turn the rpm up 50 rpm, if your flywheels can handle the extra
speed.

tuned runner lengths seldom achieve a 20 percent increase in power , more likely maybe 10%,
a 6 hp improved to a 6.6 hp engine is something you probably are not going to be able to measure anyway.

might be easier to get the same net effect in power, by improved drive systems, improvment in generator efficiency,
maintaining a high coolant temp, improvements in injection, optimizing timeing etc.

30 plus ft of tubing is a lot of stuff hanging around, and my bet is a net loss in power.

bob g

bob g