Listeroid 18/1 actual power and the math

[DirtbikePilot]

I've been contemplating the listeroid 18/1 power relative to displacement and rpm. The displacement is 1.5 times that of the 6/1. The rpm is 1.53 times that of the 6/1. Multiply these factors by the original 6 hp, and we get 13.5 hp, far from 18. This assumes that the torque is linear between 650 and 1000 rpm, and the torque is directly proportional to displacement. There will also be a tiny increase from direct injection, so let's say theoretical hp is actually 14 at 1000 rpm. What does everyone else think?

[LowGear]

Are you trying to peek under the curtain?

Casey

[Quinnf]

How are they getting more displacement?  Is it just a bigger diameter piston or a longer stroke, or both?   

If the diameter of the piston is bigger, there's going to be a square function in the mix, so the scale up won't be linear.  The area of the top of the piston increases as the square of the radius, so that might explain why you're under-achieving the theoretical power of the bigger engine by simply multiplying displacement x rpm and applying that to the 6/1 numbers.  

Quinn

[mobile_bob]

larger bores (as Quinn alludes to) result in generally higher efficiency because they have less heat loss to the coolant, and more of the effective heat is converted to mechanical force or hp per unit of fuel consumed.

there are other less complicated to calculate factors as well

the main one is one of "hp rating"  that can be just about anything that the oem wants it to be!

the 6/1 is rated at 6hp via the oem, however it might well produce 6.5 or 7, or ?
the 18/1 might well make 18hp but maybe it is more toward the maximum rating rather than a conservative rating?

then there is the differences afforded by direct vs indirect injection, cast iron pistons vs aluminum alloy,  cam timing (although to a lessor extent),  how you hold your mouth when testing, what sort of fuels are used, ambient temperatures, and heaven knows what else.

the question to me boils down to this...

what do you really want to know? specifically

is your question one of differences in efficiency?  difference in actual hp produced?  or something else?

one answer might work for all, but then again it is likely there are as many answers as there are questions asked.

bob g

[dieselgman]

+1 on Quinn's comments. The power equation is not linear with displacement and the displacement in the larger unit is due to both bore and stroke.

dieselgman

[DirtbikePilot]

I was calculating it based on displacement, and yes I know the formula for that.  The 18/1 has a displacement of about 2.1 liters and the 6/1 is 1.4, giving a 50% increase. I also agree that the efficiency will increase with a larger displacement per cylinder, but I don't think its a significant increase given this difference in displacement. I have been wrong before. I suppose the only way to know for sure would be to actually measure horsepower output compared to a 6/1, but the likelihood of this ever happening is about zero.

I think Bob was right on with his comment about hp "rating" from the manufacturers. All I'm looking for is what other people think because maybe I missed something.

If we multiply displacement by rpm and divide the hp by that number, then what we get is some sort of number that relates to the volumetric efficiency of the engine. Maybe this will help shed some light on this.
I'm going to take rpm and divide by 1000 for all results to make these numbers easier to read. The relationship between them will remain the same.
For a 6/1: 6/(0.650*1.43)= 6.46
8/1: 8/(0.850*1.43)= 6.58
10/1: 10/(1*1.6)= 6.25
12/1: 12/(1*1.86)= 6.45
18/1: 18/(1*2.13)= 8.45 (let's pretend it's rated at 14 hp: 14/(1*2.13)= 6.57, which falls right in line)

See the drastic jump in supposed efficiency? Given the consistency of all the others, I'm doubtful of the rated hp of the 18/1 and I think it's much closer to 14 hp using the same standard used on other listeroids.

[38ac]

This brings to mind a question I have had for a long time. Has anyone ever properly dynoed a CS type or a clone? or is everyone going on Mfg's ratings? I know some have placed electrical loads of "x" amps and volts which can be converted to KW and then to HP but inefficiencies come into play here that I have only seen not accounted for in some tests or guessed at in others. The reason I wonder isEVERY Indian engine of CS type operates in what the original designer would call  over fueled mode if allowed to operate at full rack. Why? because the Indians deleted the rack limiter in their engines, at least I have never seen one so equipped?  If an original CS did develop 6HP at 650 RPM which I would say is very likely given the Brits tenacity for things proper, then any clone of similar spec and properly put together is going to develope more than 6HP due simply to the fact it can get lots more fuel. A Dursley 6/1 in good shape does not smoke at full load rack, but flip over the rack limiter to the starting position and it will smoke just like an Indian engine, (Imagine that? LOL)

Reason for all this ramble is HP rating, even when done properly, is somewhat subjective and your math could very well be a bit off  A standard CS clone likely puts out more than 6 HP due to the rack liimter being non-existent, direct injection adds a bit, RPM is a major variable as is what engineer A says is full continuous load isnt what engineer B is going to call full continuous load. In the case of India we can add in bald face lies.

 When added all together this means that it is very possible that the 18/1 will develop 18 HP, it is also possible that it wont same as any other non-standard clone.  I wouldn't lay much of value against either case. Something can be told about them when one is belted up to say a 10KW head and amps and volts become knowns. We will know for certain when somebody belts one up to a dyno and gives it a run, a toy I would love  to have in the shop

[Quinnf]

One of the manufacturers sites used to have a photo of a 3rd World rendition of a Prony brake attached to what appeared to be a '6/1.  It appeared to consist of a loop of heavy 3-strand nylon rope wound around the flywheel, holding a weight.  I suppose something like that could work, but nylon melts with heat, so the friction would increase as the rope warmed.  Seems to me they had a water hose keeping the rope wet.  But it looked pretty crude.  It might have been in the same video that showed the assembler hammering gib keys home with a big sledge hammer.  

On the other hand, as with any DIY venture, if you get the right person running the brake I'm sure you can get useful information from it.

For those of you in Rio Linda, here's a Prony brake:  



Here's a pretty good article about it.  Clicking on the link will automatically download a .pdf of the article to your download box:  http://www.google.com/url?sa=i&source=images&cd=&cad=rja&docid=Z5kpw8-kScnJNM&tbnid=qzmbUZ2NH0SzoM:&ved=&url=https%3A%2F%2Fwww.mnsu.edu%2Fcetl%2Fprograms%2Fpdfs%2FPDF2007%2FCraigEvers-AET364.pdf&ei=f5BmUoCLKMipiALhy4GABQ&psig=AFQjCNGgICg7mF2cluH9iyZhDcTgXCIe8A&ust=1382539775716945

The last paragraph from the author's article explains what he calls Maximum Horsepower:

"The maximum horsepower of an engine is determined by achieving a braking horsepower equal to the output of the engine and basically stalling the engine."


Quinn

[dieselgman]

We have a proper dyno for engine load-testing at our Kansas shop... and have also intended to do some real testing for these types of questions on some of the Listeroids when we can get the chance. Our problem has become one of priorities and available time. We do not have any fully trained personnel spending full-time there and I am having a hard time with the work load in Alaska. So, difficult to say if and when this project can come to fruition. 

dieselgman

[Quinnf]

Gary, it looks like you've got to get your priorities straight.    What's more important than answering these questions that have been bugging us all these years?  (I know, putting food on the table, for one).  Seriously, I've long wondered how conservatively that 6 BHP figure for the 6/1 was measured all those years ago.  Running a genny can be a pretty good proxy for a brake.  After all, that's the primary load the users put on these engines, so simply saying the engine can produce appx. 3000 watts before smoking excessively is useful.  But it's still subjective.   

[millman56]

Depending upon how its running my 6-1 seems to be all out and up to the anti overload stop at approx 238 volts, 10 amps,  48. 5 HZ and 640 rpm, with visible but not excessive smoke, if the injector is carboned it smokes at 1/4 of that load, the serpentine belt and  alternator losses are an unknown factor.      It is fitted with a Kubota style PM battery charging generator driven via a slack vee belt, this can be stalled by hand and the belt allowed to idle freely with little drag, it speeds the whole caboodle up by 0.50 HZ when not driving this generator and back down again when driving it.   

I would reccomend building yourself a digital Volts, Amps and HZ meter, one of these takes the guesswork out of generator performance measurements and makes comparative tests a breeze.

Mark.

[Tom]

Millman, that's only 2300 watts. My 6/1 will make 3125 watts day in and day out with just a touch of grey smoke when cold. This is measured via the metering on a set of Outback vfx3648 inverters. Altitude is 1036' above sea level. The ST5 gen head is powered via a serp belt.

The 6/1 is rated 4.4kw, figuring an 80% efficiency on the gen head nets 3.52kw. So it's not to far from the theoretical max. It will output more than 3125 watts, but that results in lots of black smoke.

[millman56]

Well Tom,  thats all it will do and I can only tell as I find,   just bear in mind that miine is running on hyd/trans oil and that the original 6-1 SOM sets were only rated at 2500 Watts continous duty.       Mines in pretty good order but on its present diet will not develop full power until warmed up, its fitted with a glow plug combustion chamber which I understand to give a comp ratio  approx half way beetween high and low comp settings on the changeover fitted ones.

Mark.