increasing power, tuned intake and exhaust ?

[mobile_bob]

i have read what i believe is most if not all of the posts on this board, and i have seen mention of trying to increase power
on these engine's

it is a given that the limiting factor is how much air you can get into the engine, as fuel seems not to be the problem in
that they all reportedly begin to blow black smoke as they reach their rated power.

several years ago i bought a pair of engineering books on engine theory and there is a section with the related math
to calculate the sizing of intake runner length and exhaust header length. These calc's were worked out on a single cylinder
gas engine in a lab at MIT.

a couple of things come to mind, and based on memory, which maybe lacking
also would like to preface the discussion with the following, fixed rpm engines are very easy to calculate the runner lengths required, which
can increase the amount of air and power upward of 20%.  The only thing i don't know as of yet is the cam angle or overlap used on these engines. modern diesels have extreme overlap and dont gain much with this scheme if i remember right. i am thinking that being an old design the overlap is likely quite narrow if at all.

1. the intake runner length on these engines is far too short and on the twins is horrible.  the intake length will likely be much longer than what is customary on these engine's. these short runner lengths don't do anything to ram air into the engine until over 5k rpm or more. which is never going to happen.

2. the exhaust runner length is also far too short, and should empty into an expansion chamber of sorts.

if there is interest in this topic, i will dig out the books and if i can get some cam degree info from the board, i wll run the calculations for a particular engine.

anyone interested?

bob g

[cujet]

At 650 RPM, the 1st order tuning must be something like 72 feet

Seriously, take a look around the web. Intake tuning can simply a factor of length vs. RPM. Exhaust tuning is much more variable. I believe most automotive intake manifolds are tuned to a 4th order harmonic at the chosen RPM of the manufacturer. Generally around the peak torque RPM.

Chris

[BoldtsWagon]

Cam degree info:

http://listerengine.com/smf/index.php?topic=123.0

[mobile_bob]

thanks for the cam info

cujet:

i had it in my mind that the length might be upwards or 6 feet, on the intake runner. but you may be right and anything over that would be not practical.

going to have to dig out those books , just moved last month and haven't got everything unpacked yet.

seems like using tapered runners greatly reduced the required length of the runner also, but i gotta check that out.

would seem to be a useful excersize, for instance a 6/1 looks to be limited to around 3.5 kwatt electric, perhaps with intake and exhaust work 4 kwatt could be crossed without too much trouble, seems useful if you need to get a few more watts out of an existing installation.

has anyone here worked on this scheme?

bob g

[hotater]

We were waiting on you, Mobile Bob.  Welcome aboard.

An interesting excerize for those looking for something to fiddle with while watching your engine run....take off the air cleaner, load the engine to about 80% and experiment with a piece of poster board with funnels and tubes and baffles and watch the position of the throttle bar.  It  DOES make a difference, but not much.
 I *have* thought of building a filtered box mounted above the engine in the rafters with a dryer hose to the engine.  That would be a five foot run of three inch from an air box of two cubic feet.   A multi-stack of AC filters sprayed with K&N filter juice should last about a year!  I figured I could paint the inside of the box and it'd be easy to tell if dust were getting through and change back if it didn't work.         Muffin fan in the dryer tube to 'turbo' the Lister?
  I'm considering it.   

Another source of filter 'elements' are surplus vaccum cleaner bags.  They're a dollor an arm-load at Salvation Army.

[snail]

     I've been thinking along these lines, not so much from the power increase point of view, but to raise the compression pressures/temperatures for burning waste oil.I currently burn waste transmission oil. On a theoretical note,assuming that no extra fuel is injected, would there be a point at which compressing extra air would waste power?
    I have a 12/2 with the awful inlet manifold set up. The biggest restriction was caused by an undersized gasket between the airfilter elbow and the manifold. I didn't actually measure it but it was around 32mm. The elbow is 40mm dia and the manifold was a very mis-shapen 36mm diameter. After a bit of a touch up on the mill, I now have a 40mm inlet as far as the manifold branch.A bit of port matching also seemed in order.
     Was it worth it? Can't say conclusively but I doubt that the situation is worse than from the factory.
I'm glad someone's offered to do the calcs cos I've been thinking about making a couple of telescoping inlets from exhaust tubing  to find the sweet spot by trial and error.
    Keep up the good work guys!

Cheers

Brian

[mobile_bob]

well i dug out the books and found the calc's and charts regarding tuned intake or rather intake length

i have to state the following

1.  650 rpm is hard to extrapolate from the charts given in the books

2. not having exact valve events, overlap etc makes it a bit tough to get precise results,

but having said that i have come to the conclusion that an intake runner of approx 1.5 inches in ID, and approx 60" in length will provide increases in the amount of air forced into the cylinder, conservatively i would expect perhaps 10% increase in Volumetric Efficiency or hp.

the reason for not having large intake and exhaust valves in these engines is they arent needed, the mach index or air speed entering the cylinder is not maxed out, minor gains might be made with larger valves only because of the nearly non existant intake and exhaust runner.

the intake and exhaust runner length on these engine's are optimized for 5k plus rpm, so it is apparrent that the design didnt take dynamic boost into consideration but rather a neat tight package dimension.

as for cam profiles, overlap is not a problem on a diesel as it is on a gas engine, as you don't have to worry about blowing fuel out the exhaust during overlap. there is no fuel to blow out in an injected diesel. perhaps larger overlaps might help to clear the spent gasses from the cylinder and provide a cleaner burn or more power because of higher percentages of o2 available.

i see no reason to go over 1.5 id on either the intake or the exhaust runners, especially at these low rpm's and perhaps a smaller id would work better, in either event i would try and match the runner id to the port size as close as possible, and port match the flange to the head port. one other observation would be  to use smooth piping to keep down turbulence and drag and to use a large chamber to draw from, with an equally large airfilter to cut down on restriction and smooth the transition.

did lister originals state the need for long exhaust pipes to be connected, seems i saw someone post something to that effect.

bob g

[GuyFawkes]

The _old_ rule of thumb was 1.5 x cylinder capacity for exhaust tract and 0.5 x cylinder capacity for inlet tract.

It doesn't give you the best of all worlds but it is good basic solution that works well with practically any motor, including 2 strokes, and focuses on power and clean combustion, _not_ silencing intake or induction.

"tract" = pipe, so measure up until the expansion chamber, anything after that is back pressure.

---------------------------------


regarding the valve timing of listers, I see a lot of people second guessing a design that stood for half a century, and making all kinds of assumptions based on different engines, different fuels, different rpm, different everything.

you _really_ think lister got it wrong for 50 years straight and nobody ever noticed or looked at this.

you _really_ think for the sake of changing valve timing they threw away free horsepower and therefore sale ticket price?

they build them that way for many reasons, one or two of the many reasons are overlap in a low/medium speed stationary engine is a GOOD thing, it purges the pre-combustion chanber for starters, it keeps valves / guides / piston crowns / pre-com chamber significantly cooler, it helps emissions, it helps fuel economy (no exhaust gas in the new charge) it increases the charge a naturally aspirated engine can draw (cold air is denser), and so on and so forth.

I recall a second hand tale of Farm Industries (a company that went bust yonks ago) putting a gas flowmeter on a Lister CS intake and actual volume of air drawn in vs cylinder capacity x rpm was as near as dammit close to parity.

[mobile_bob]

"The _old_ rule of thumb was 1.5 x cylinder capacity for exhaust tract and 0.5 x cylinder capacity for inlet tract."

well that will certainly get you and engine that run's, and at some particular rpm it will run well.
(having done the math your method results in a intake runner length of approx 72.5") with a 1.5 inch id runner

"regarding the valve timing of listers, I see a lot of people second guessing a design that stood for half a century, and making all kinds of assumptions based on different engines, different fuels, different rpm, different everything.

you _really_ think lister got it wrong for 50 years straight and nobody ever noticed or looked at this."

i for one would not suggest lister got it wrong! but...

i would suggest that they took comprimises as all manufactures do.  lets face it a 6-7 foot intake runner and a long exhaust runners is not going to make for a neat tidy package.  Cam profiles were not widely understood and the ability to test them scientifically back in the 30's was somewhat limited.

just because an engine has been around for 50 years of production certainly does not mean it has evolved or been optimized for a particular use, (rpm, load range)

another example if i may
the small block chevy v8, been around for 50 years and counting, and folks optimize them to do all sorts of stuff. whole industries have come and gone build parts to optimize these engines.

"I recall a second hand tale of Farm Industries (a company that went bust yonks ago) putting a gas flowmeter on a Lister CS intake and actual volume of air drawn in vs cylinder capacity x rpm was as near as dammit close to parity."

parity is probably optimistic on these engines as built, but perhaps so.
if parity is the case then a proper length intake runner will increase the air charge above parity.

gotta get this 25/2 uncrated and mounted, and find time to work this out.
i have no plans on altering the cam profile of the original, as that seems to be alot of work and lets face it how much power do i really need from a 25/2?  outside of welding i will likely only see 50% capacity anyway.

bob g

[GuyFawkes]

  Cam profiles were not widely understood and the ability to test them scientifically back in the 30's was somewhat limited.

just because an engine has been around for 50 years of production certainly does not mean it has evolved or been optimized for a particular use, (rpm, load range)

oh boy, if I had a (insert denomination) for every time I heard that.

computers do the SAME sums as pen and paper / slide rule / abacus.... lots of the time (excel and P2 floating point errors) they just make mistakes faster and more repetitively.

what I see ALL the time now is fuckwits sat at computers running computer models of things and believing that they have anything more fancy than an arcade game in front of them, the CAD / CAM / CAE must be right and when the finished product doesn't work some group of "assholes" with a mere 40 years experience hands on engineering each get the blame for "doing it wrong" or some such crap.

[solarguy]

I will post one point for Bob, and one for Guy:

In support of Bob:  Some mathematical modeling of complex systems (like engines) can be neatly solved by fairly simple iterative computation, basically succesive approximations and getting closer all the time.  Computers are fabulous at this sort of work and can refine things to a degree that is difficult to replicate by manual methods.  There are certainly other applications where computer modeling has made the process of refining a design vastly easier and faster.  You can try a hundred designs on silicon before you build your first "real" prototype.

In support of Guy:  Computers are no smarter, and frequently orders of maginitude dumber than their programmers.  Garbage in = garbage out.  Back when we did things manually, with literal slide rules, the engineers had to have a pretty good grasp of what the answer should look like so he could get the decimal in the right place and with the proper sign.  He would also double check the result two or three different ways usually. 

When some designers got the first computers, there were some problems like roofs falling in on commercial buildings because the machine just spit a number out, and there was no "feel" for what the result "should" be.  The program and/or machine made a boo boo and there was no easy way to double check it without doing it manually.  And the whole idea was to eliminate all those manual calculations, so they just didn't do it.  Computers are just faster, that's all.  Not magic, and certainly no common sense.  A little computer in the hands of a little designer with poor common sense is a recipe for disaster.

Finest regards,

troy

[hotater]

There goes that rotating light and claxon again.....

My job is to battle engineers in Court...talk about FUN!  I usually win because I talk the jury's language instead of the text book's.....

....and, of course I'm right.    

[GuyFawkes]

this is a kinda pet peeve of mine I must admit.....

worked for a guy many moons ago who used to be in the overwater drilling biz, barges lifted off the water on spuds and then you drill cores, lot of work from people planning bridges and so on....

these barges were made so you could break em down and ship them by road in 40 foot sections.

the core of everything was the hydraulic power pack, a box frame containing a complete standalone diesel engine, fuel tank, battery etc etc, coupled to a hydraulic pump and a bunch of valves with quick release hydraulic fittings.

(at the time we would buy ford 6d diesels by the pallete from reading industrials for 1000 quid a pop, plumb in the fuel, connect the battery, and run them into the ground)

so this guy would design stuff on the computer, complete with performance diagrams and all sorts, and hand us to plans to build it, thing is never having seen a spanner in his life he'd design things you couldn't build, valve chests that didn't have any space around the unions to put a spanner on much less swing them, and when it came to hydraulics he was a right whiz in theory and could produce all sorts of colourful charts and suchlike, but he didn't really know the difference between a splitter or twin pumps and had no idea which was best for what application.

we had a choice, build it the way he designed it, in which case it would all go to the job and at that point you'd discover it didn't perform as required, or build what was needed, we built was was needed and used his blueprints as a tablecloth, you could show him the finished article and he couldn't tell that is wasn't the same as the thing he designed....  none of our shit broke down on the job though....

--------------------------------

it was while working there that a couple of guys from a very well known CAD software company came down, purpose being they worked with some customers to imrpove future versions of the product, and we were picked, they spent a week in the office with matey, then caame over the river to the workshops to see us

at the time I was younger than the other guys there, but they always let me call the shots on design issues, saying this was because the guy who trained me was so good, later I figured out they'd just as soon let the young un work hardest for his wage and be responsible for any cock ups, anyway, when these CAD guys came over they got pointed to me.

I was never and never have been a qualified draughtsman, but in order to read drawings you had to be able to make them, cos sometimes you had to alter them or even make them too, so I was bitching about the crap these drawings would produce, and wasn't getting through, so I thought ok, back to basics, and pulled from memory one of the example trick questions, you are given the top and front  projections (which look identcal, a square with a smaller square centred on the baseline, all solid lines, no hidden construction lines, nothing, complete the drawing by doing the side projection.

now this wasn't really a trick question.

it was a test, if you tried to visualise it you got it wrong, and drew something impossible, if you turned you imagination off and followed simple rules of draughtsmanship, you got it right, side view was a right angle triangle with a little box at the base sticking out of the hypotenuse plain.

__ALL__ the other guys are nodding, they have all had some sort of apprenticeship or other and seen this one.

the CAD boys are looking as blank as ever.

it dawned on me then, people who write CAD software (and prolly most other software too) are computer programmers, they know absolutely fuck all about draughtsmanship

-----------------------------------

nowadays they start in on the computers at primary school, nobody actually touches a spanner or metal, that's for the scum of the earth, so everyone is playing around with computer models and simulations and projections and so on and so forth, npbody gives a shit how anything in any of the models compares to real world things, that comes LAST and is made to fit the models....

I had a real flame with a guy on a CNC machinery list a few months ago, he was claiming his machinery (which had x y z axis of about a metre) had REPEATABLE accuracy of the order of a few atomic diameters... I did all the math, showed him 0.001 degree celcius temperature change in the bed would blow that right out of the water by orders of magnitude (this was after I had to prove to him that the bed which he claimed had a zero coefficient of thermal expansion merely had a low coefficient.

bottom line, how did he know for a fact his CNC was that accurate?

well, it had that accuracy on the readouts you see, and in the sales bumph.

if it SAID 13.725389 mm then by golly it WAS 13.725389 mm

hey, it was a *fabulous* machine and extraordinarily accurate (and expensive) but still on a different planet from what he believed.

ok, now I'm going to have a coffee and a cigarette and calm down

thx for the therapy 

[GuyFawkes]

it dawned on me then, people who write CAD software (and prolly most other software too) are computer programmers, they know absolutely fuck all about draughtsmanship

the point I was trying to make her and lost....

CAD software is shit, because you can design things that cannot be made, but draughtsmanship rules stopped you doing this.

if you doubt me, draw a bimetallic strip in CAD..... think about it.

[kpgv]

Hi All,
I'm with GUYFAWKES on this.

Facts and Observations:

1) Rod Ratio for a Lister CS = 2.18 :1.
    a) This is a little unusual in design terms, and "usually" only found in large "stationery" engines (Where "Size" is less a consideration), and "high RPM" racing engines (and probably Aircraft engines).
    b) The effect of a high rod ratio is to increase the "Dwell" time at TDC, and BDC, AND (Most important for Us) to REDUCE the "side thrust load" on the cylinder walls. It also increases "Piston Speed".

2) Harry Ricardo had a hand in designing the "CS" head.
    a) Harry Ricardo was, AND still is considered one of the preeminent design engineers ever for internal combustion engines.
    b) The assertion that "cam" design was less than the best then, and is now obsolete is not likely.

3) Don't make the mistake of believing ANY "Hot Rod" engine software can assimilate and render a useful conclusion for these engines.
    a) These engines are a "contradiction" in normal design terms any way you cut it.

4) We don't know how the "India" cam compares to the "Original" profile.
    a) The original Lister Company made more than one cam profile. Which one do WE get, or is it also different?
    b) Does anyone out there have "real" detailed drawings degree by degree and thou. by thou. to compare?

5) Cams and Valve trains are better now.
    a) Thanks for the update!
    b) Why do you suppose Listers and Roids have Dual Valve Springs?
        1) The Origonals and the Roids have two. Is that because they want to do the extra machining and make the second spring just to "Impress" Us?
        2) My "Guess" is that they at least mitigate, if not eliminate any harmonic problem.
        3) They provide a lot of "seat pressure" and a lesser "rate" which is best for steady low RPM running.
        4) One could probably apply some "modern" high tech design and materials and do it with one, but what will we GAIN?
    c) Some think Mushroom tappets are "inferior" to roller tappets.
        1) EVERY NASCAR engine runs "Mushroom Tappets" every lap, every race.
    d) Yea but the "Injector" tappet on a Lister has a roller.
        1) That is because it WON'T OIL over there.
    e) My belief is that NONE of the improvements you can identify with respect to "modern" valve train systems will make a measurable, tangible improvement as applied to a Lister(oid).

6) Perfect BEFORE Modifying.
    a) Do your Valves "Seal"?
    b) do your Rings " Seal"?
    c) Is your Valve Train Geometry and Setup "Proper"?
    d) Have you worked out the "Balance" problem?
    e) Do your tappets spin?
    f) Is your "Rack" free.
   

Just MY Opinions,

Kevin