DESMO Discussions (continued, here) Thread

[graeme]

So this leads to the more interesting topic of improved cylinder filling.
(Please)
Which is where this is going anyway,,,,,
Graeme

[DewCatTea-Bob]

____ All the post-wording within the quoted-area below has now been rounded-up from recent past-posts (as far back as the 9th) by Graeme, as it's all stuff which I've been meaning to get-to but, this thread burst-forward at a rate which led to all this getting left-behind as far as it has. _ So I've had to gather it all together here, so that it doesn't get entirely forgotten before I can finally get-back to responding to it all.

I find it hard to imagine any gain (considering the amount of work involved to remove a large piece of lobe) as opposed to just lapping the closing lobes and forever more being done with worrying about any future binding issues?

____ Just so it's clear, even-though I've suggested that the majority of the closing-lobe serves no needed purpose (so long as all closure-springs are not completely eliminated), and therefore COULD be removed,, I've never really meant for it to be understood that such drastic lobe-reduction should ACTUALLY be done !
__ My intended-point for bringing-up the whole possibility, was merely to help MAKE-the-case clear that there's no real need to be very concerned with the minor-detailing of closing-lobe imperfections, when most of the lobe could be eliminated without making any performance-difference, in either case.



" Has anyone used the red/white Desmo cam?
Does it have a binding issue? "

____ I've set-up that 'Special 350DESMO-cam' in a 350D.head, and adjusted it well enough to be run but, I've never bothered to try to adjust it finely enough to see if it could possibly be set thusly so as to discover any binding-points.

Hi Bob,
Don't get me wrong here with my "devils advocate" comments. I find this interesting and thought evocing, and I see and understand your thinking re the un nessary complete closing lobe and letting the cylinder pressure seal the valve against the seat. And your thinking regarding the overlap where it may be possibe for an un controlled exhaust valve to blow back open to accept some charge that has escaped down the exhaust if the header and reverse cone end were tuned to allow this to happen. Forced back into the cylinder by the reversing of the pressure wave in the pipe.
BUT
This can be done with a specifically ground cam which could control the valves to allow this to happen at a given rev range, (with a tuned exhaust) without the valves being allowed to do as they wish.


But this thread is or was about Desmo cams that were produced by the factory, their faults, and other desmo cams that were produced by V2 etc. and I thought how to sort the problems.

Graeme

____ I've yet to finish with this remaining-part, later.
-B




"(Please)
Which is where this is going anyway,,,,, "

____ It's often difficult to discern if one's written-word is meant to express any sarcasm or not...
As I've already gathered that Graeme has been somewhat disappointed with the direction that this 'DESMO' thread has strayed-away (from HIS expressed expectation).
__ I do indeed agree that 'improved cylinder-filling' would be a great topic for discussion, (and I've LONG been meaning to start such a thread-topic myself, [but realized that wouldn't be good to get in-to without PLENTY of time to devote to it]),, but IT, would REALLY deserve it's very-own thread !
__ AND,, there's always the O'bugaboo of how 'deep' the topic should be handled... rather meaning should it be discussed as if seasoned-professors of the field were expecting to fully-educate an expected apprentice, or more simply on-the-other-hand, merely attempt to inspire some raw understanding of the more-pertinent 'basics' of the topic's field ??
I-myself would only be able get into the most-pertinent BASICS of it all, (as at my age, I'm not-REALLY interested in getting an engineer's detailed grasp on it all).

____ I don't know what Graeme's own inclination is but, I-myself later intend to replace this-post, (as it's nowhere near on-topic for THIS thread).



Hopeful-Cheers,
-B

[graeme]

Hi Bob,
My "please" was not scarcastic but genuine.
This subject of cylinder filling is the next step from the previous posts re cam timing and valve opening etc.
This is a very interesting thing to me, and I expect others. And there are people here who I would hope will share their knowledge.
Probably not all that important for 100% standard show bikes, but very interesting for anyone looking for a little more from their engine.
Graeme

[graeme]

Here is a standard 450 RT head.







Lots of improvements to make it flow more smoothly. ?????
(This is wet blast not bead blast)

[LaceyDucati]

Hi Graeme and all.

Off this thread! Much as I would like to share information concerning improved cylinder filling / porting, I simply haven't the time to at the moment. Posting advice and sharing info is great, but it always leads to seemingly endless discussions. For me as a practical engineer, my forte is doing things, three dimensional thinking, thinking outside the box and trade skills. Writing and making myself understood is unfortunately not one of my fortes!
As for theory, yes an element is important but my experience is, the magic element is observation and getting on with it. I've come across plenty of Graduate / theory engineers who can quiz me and spout theory, but clever as they are, most (if not all) fail to do better. My advice is read Tuning for speed by Phil Irving and Performance Tuning in Theory and practice (four strokes) by A. Graham Bell. Some of the theory is out dated, a bit sketchy or not wholly relevant, but in those books are the basis of all my developments. Both you may note I think are Australians! As you go on you discard some info and gain your own theories more relevant to your engine. You will also quickly note that some basic fundamentals of Ducati Singles fall outside of normal theory. With the benefit of 50 years of development it's not surprising Dr T's theories are outdated. Bearing in mind the time, available materials and production requirements / restrictions the man was still a genius! There are other books, some more modern and others like Phil Irvings Motorcycle Engineering that are full of good sound theory. I will try and find the time to post some info and pictures relevant to the 480 if a new thread starts, though it will unfortunately be limited due to having to run a business!

Greame, on a personal note if you find yourself in the UK you can always come for a visit and chat, I find information transfer is massively greater with the interactive spoken word!

Best Wishes Nigel

[Harvey]

Hi Graeme and all.

Off this thread! Much as I would like to share information concerning improved cylinder filling / porting, I simply haven't the time to at the moment. Posting advice and sharing info is great, but it always leads to seemingly endless discussions. For me as a practical engineer, my forte is doing things, three dimensional thinking, thinking outside the box and trade skills. Writing and making myself understood is unfortunately not one of my fortes!
As for theory, yes an element is important but my experience is, the magic element is observation and getting on with it. I've come across plenty of Graduate / theory engineers who can quiz me and spout theory, but clever as they are, most (if not all) fail to do better. My advice is read Tuning for speed by Phil Irving and Performance Tuning in Theory and practice (four strokes) by A. Graham Bell. Some of the theory is out dated, a bit sketchy or not wholly relevant, but in those books are the basis of all my developments. Both you may note I think are Australians! As you go on you discard some info and gain your own theories more relevant to your engine. You will also quickly note that some basic fundamentals of Ducati Singles fall outside of normal theory. With the benefit of 50 years of development it's not surprising Dr T's theories are outdated. Bearing in mind the time, available materials and production requirements / restrictions the man was still a genius! There are other books, some more modern and others like Phil Irvings Motorcycle Engineering that are full of good sound theory. I will try and find the time to post some info and pictures relevant to the 480 if a new thread starts, though it will unfortunately be limited due to having to run a business!

Greame, on a personal note if you find yourself in the UK you can always come for a visit and chat, I find information transfer is massively greater with the interactive spoken word!

Best Wishes Nigel

I really do hope Nigel, that these remarks are not aimed at my last post. I am 73 years old, and have been in Auto work all my life. I do not hold a Degree or any other form of superior credentials, but bikes have been my passion, having started on a BSA Bantam 125. I have not tried to spout theory to impress anyone (not my style). I have trod the same path as every one has, but having had an enforced retirement from riding and working with bikes 17 years ago, I have had the time to look at what it is all about.
It is my belief that knowledge is wasted if it is not passed on.

Looking at my shelf, there is PIs “Tuning of speed”, PIs “Motorcycling Engineering”, Harry Ricardo’s “The High Speed Internal Combustion Engine”, and Philip Smiths “The Scientific Design of Exhaust and Inlet Systems”. I learnt most about Sonics and pressure pulses, from working on two-stroke systems that are applicable to the four-stroke engine.

I now find that using CAD programs, I can experiment with any change to the cylinder, with out actually doing it. Good bad or indifferent, it does allow you to look at the pressures that are happening in the engine at any time to gain a better understanding on how to match the engine to capture the best result. The program that I use is a freeware one from Lotus Engineering http://www.lotuscars.com/au/engineering/engineering-software. You can only build a single cylinder engine (unless you pay for the wholly program) but you can try any modification, then watch the pressure waves acting in the pipes to see the results.
The pictures of your angled inlet port save a lot of writing.

Cheers Harvey.

[graeme]

Hello Nigel,
I understand that you are running a business as well as giving your valuable time to help people out of business hours and I (and I'm sure others) appreciate your knowledge and experiences.
I agree that point and tell is better to learn and easier to understand than written word. I'm not the best at the Queens English either and also find it hard to explain what I mean.
I would love to have the chance to visit the UK and Europe, maybe one day.
I certainly agree than Dr T was a genius as were other engineers and designers of earlier days before computer programs and the internet was available. I only need to look at (for example) a single engine dismantled to realise that this engine was drawn on a drawing board by someone that worked out all the dimensions of cases, gears, and every small part to make it all fit together, then for those section drawings to be actually cast or machined into actual parts that fitted and worked,,,,, this is mind boggling. No cad or 3D modeling to see if it all fited before it went to the machine floor.

The standard RT head pictures was meant to show what standard head ports look like, not to ask how to make it better. I've already tidyed (?) it up and it's being used.

Graeme

[graeme]

"The pictures of your angled inlet port save a lot of writing. "

Hello Harvey,
If your comment is, I assume, refering to the inlet port on the RT head, the steel manifold seems to me to be more of an issue with its sharp edged curve?
But this port and manifold would be needed to fit the engine and carb into the frames that were used. Keeping in mind that these bikes were not built for racing only.

Regards
Graeme

[LaceyDucati]

Hi again.

Firstly Harvey my comments were not in any way directed at you, only from my observations and experiences in life and from competition. I have no doubt that there are many engineers out there with greater knowledge than myself who could extract more power from a particular design. I have looked at a few modelling programs and I would agree that they are very interesting and useful for starting points. Thank you for the link. But my research back ground tells me that computer modelling is limited as I am sure you know. There are certain details that are very sketchy in the programs I have seen. They assume certain aspects of things like port shape and position being ideal etc. My opinion is that there is a point when theory has to stop and reality with all it's real world imperfections takes over. Flow bench testing and dyno work will then give more information as it is far more specific. Concerning books I think we have a similar collection!

Graeme my comments were specific to improved cylinder filling and your request for info relating to the 480 engine, which I would like to share time permitting. I do know and appreciate that help is mostly appreciated. You are correct that road bikes have different requirements and many people make poor decisions relating to modifications for the road. Any modifications made should be made with a calculated and thought through objective. Improvements for the road really interests me and given the time I want to start a program of development more suited to "real road" performance modifications. Most of my development work over the years has been with racing and I think I've nearly come to an end of any significant interest or gains there.

A recent visit to the dyno with a customers 350 road bike highlighted the need for more investigation into road equipment. Amongst various other things, we tested an original 750 Conti silencer against 2 replica ones, all were effectively straight through. Between the best to the worst there was about 3 to 5 bhp different through from 4.5 to 8k. Even after rejeting we couldn't make much improvement. The original Conti was the best by far, just an example of what a small and not obvious (at first sight) change can make.


Sorry if any of my comments have been taken the wrong way. Again another example the limit of the written word to to transfer full meaning and intent!

Yes, off subject again (before it's said!), just trying to round up, I've nothing further to add on the Desmo subject. Any further discussion regarding the above will have to be else where (new thread).

Best Wishes Nigel

[DewCatTea-Bob]

" Firstly Harvey my comments were not in any way directed at you, "

___ I for one, didn't have any such connection occur to me (until after Harvey asked).



" A recent visit to the dyno with a customers 350 road bike highlighted the need for more investigation into road equipment. Amongst various other things, we tested an original 750 Conti silencer against 2 replica ones, all were effectively straight through. Between the best to the worst there was about 3 to 5 bhp different
The original Conti was the best by far,

____ Something I've noted-of before with those type mufflers, is the particular-design of the sound-absorbing/silencing-louvers... I believe the louver-openings within the replica-versions face the opposite-direction as those of the real Conti-mufflers (which thusly have THEIR louvers faced in the most 'streamlined' direction [for exhaust-flow]). _ And although I believe that that seemingly minor difference would indeed more-greatly interfere with otherwise less-disturbed airflow, (incidentally, not too-awfully dissimilar in manor, from that as I have proclaimed-of in my recently-mentioned excessively-higher valve-lift, result-expectation),, I would not have actually expected that airflow-interference difference to result with such a large difference in BHP (with a mere 350). _ But if there's no OTHER differences (in any of those muffler's dimensions), then there can be nothing-else left to suspect (for the power-output discrepancy, [expect perhaps things like atmospheric-pressure changes, if the tests weren't all done on the same day] ).
(This idea of louver-shape orientation possibly being responsible, ought-not be of any big-surprise to anyone who can conceive which way a 'funnel' should be faced in order to disturb airflow the least.)



" Yes, off subject again Any further discussion regarding the above will have to be else where (new thread). "

____ Yes, that probably ought-to be the case, IF it's certain that the topic-diversion all on it's own, is actually worthy of more than one-page of thread-posts.


Duke-Cheers,
-Bob