What have I done???

[passenger0_0]

I think anyone following this little diversion to Shaun's original posting must be getting bored with us banging on with our opinions on tuning a Vincent so I'll cease going down that road. We all are right in our own way but it's just a shame that once we've spent our cash on hot up spares and irreversible mods that if in the end it when doesn't meet our expectations we get bitterly disappointed and usually onsell our dream. I have wasted many years and more money than I care to remember listening to the "experts" trying to find the high horsepower numbers often quoted for Vincents. I agree anything can be done - just look at what Steve Hammel has achieved, but, these are experts who know more than most. It is not fair to compare Ducati hp to a Vincent since peak values are produced at much higher engine speeds - if you look at the torque it will be significantly lower than the Vincent value, remember hp = torque x revs. Phil Irving used to quote bhp/litre/1000 rpm which is by far a better way to compare engine output. My suggestion for going to bigger cubes gives improved torque etc... but no need to rev the engine to an early death since crank inertia loading increase to the square of the crank speed. Regarding my power output being 80 hp at the crank you're likely correct but if we consider total energy delivered to the combustion chamber then my engine makes 240 hp - knowing that this power is distributed approximately to 33% crank power, 33% thermal loss & 33% exhaust loss. Great for pub talk but the only real measurement that counts is where the rubber hits the road. I appreciate this stimulating discussion and hope that I haven't offended you or anyone else with my opinions. I've included a picture of a 71 hp working out my rear tyre. Cheers David

 

[John Appleton]

David, how right you are. In the early 60's I was given all sorts of goodies to bolt onto my recently aquired Rapide. The donor was Dave Knightbridge, who had dabbled in racing on the old Boreham cicuit and other circuits in the south east. I am eternally greatful to Dave (who was a life member of VOC) for introducing me to Vincents, but I learned my lesson regarding hot cams, hot pistons, big bore carbs etc. I had built a machine that was faster than my capabilities , was unreliable , a pig to ride in town and totally unsuited to what I really needed. It wasn.t until I bit the bullet and detuned the engine and modified the gearing that i was able to enjoy what I had bought--- a bike capable of travelling thousands of miles, started when I wanted it to, and was still faster than my capabilities. It just goes to prove that the Phils knew best what a road bike should do.

John

 

[TouringGodet]

There must be alot more potential in the Vincent motor , I've seen 750 Ducati Bevel motors with almost 90 BHP and 900SS Bevel motors with over 100 , with really wide power bands. OK the 900 is a Desmo head so it can have wild cam timing , but even so , the Vincent 1000 could get close.

Steve Hamel's Bonneville Vincent is 1000cc on petrol, and he has had it dyno'd at over 115 rear wheel horsepower, that figure might even be one or two years old. He finds a few more every year. Sure, his original Bonneville motor had pretty extensively modified heads, but he has been working on another design that doesn't require as much modification, that is getting as good or even better flow.

 

[passenger0_0]

Hi Steve D., I agree with you that Steve Hamel is getting very high hp and it's a credit to his skill & knowledge, especially with his bike running on petrol. On youtube video I've seen suggests even higher hp readings but at an rpm would make most Vincents engines explode like something out of the film The Hurt Locker. My outfit The Fast Lady is also on youtube for anyone interested. Ducatis and the like all produce peak power at what - say 8,000 - 9,000 rpm plus, good luck with making any Stevenage Vincent reliable at these speeds. Don't get me wrong, the potential is there as proven by the Irving-Vincent team in Australia who have Vincent-based bikes reliably producing 165+ hp but these are not 60 year old engines with fragile 1" crank mainshafts etc..... Extraordinary Vincents (and not mine I might add) give extraordinary performance but require extraordinary skill to build and are not just simply an assembly of off the shelf performance parts. I'll sign off now from this thread as I've gone on much loner than intended but will leave an open question anyone considering hotting up a Vincent needs to consider - do they possess this skill? If so then good luck in keeping the legend alive. Happy tuning - David

 

[Tnecniv Edipar]

I think anyone following this little diversion to Shaun's original posting must be getting bored with us banging on with our opinions on tuning a Vincent so I'll cease going down that road. We all are right in our own way but it's just a shame that once we've spent our cash on hot up spares and irreversible mods that if in the end it when doesn't meet our expectations we get bitterly disappointed and usually onsell our dream. I have wasted many years and more money than I care to remember listening to the "experts" trying to find the high horsepower numbers often quoted for Vincents. I agree anything can be done - just look at what Steve Hammel has achieved, but, these are experts who know more than most. It is not fair to compare Ducati hp to a Vincent since peak values are produced at much higher engine speeds - if you look at the torque it will be significantly lower than the Vincent value, remember hp = torque x revs. Phil Irving used to quote bhp/litre/1000 rpm which is by far a better way to compare engine output. My suggestion for going to bigger cubes gives improved torque etc... but no need to rev the engine to an early death since crank inertia loading increase to the square of the crank speed. Regarding my power output being 80 hp at the crank you're likely correct but if we consider total energy delivered to the combustion chamber then my engine makes 240 hp - knowing that this power is distributed approximately to 33% crank power, 33% thermal loss & 33% exhaust loss. Great for pub talk but the only real measurement that counts is where the rubber hits the road. I appreciate this stimulating discussion and hope that I haven't offended you or anyone else with my opinions. I've included a picture of a 71 hp working out my rear tyre. Cheers David

I used Ducati as a reference because they do share a similar architecture with Vincent engines. Roller bearing bottom end V twin. Would have to disagree on torque , the Ducati will produce more peak torque due to a better BMEP , but the torque band on the Vincent may be wider.
My experience in engine tuning has taught me that any engine can be impoved in performance , some more easily and more than others. One facility is essential to extract the best from any engine is a dyno , anything else is whistling in the wind ! It's by far the best way to determine exactly the correct ignition timing and fuel , and also to asses the improvement of any modifications. Anyway , over and out on this , don't wish to bore anyone any further.

 

[Bazlerker]

Thirty, Fourty and Fifty years ago there were a great many folks who sought by many means to make their Vincents faster - by any and all means...we have them to thank for the great repository of knowledge that is available to us...and because not a few Vincents were destroyed in the process we also have a few of them to thank for the increased value of the Vincents that are left...We are now talking about 50+ year old machines..their horsepower output in stock ( or close to stock ) configuration is more than enough for the rider who seeks a fast touring machine..In other words exactly what they were designed for.
We are all but caretakers now, responsible for maintaining not only the machines, but the legend..I say treat both with equal care. Change the oil regularly, run it up to "the ton" whenever you want but leave the pursuit of absolute speed to those very few, very skilled, very wealthy individuals who are most qualified and who most often do it with repro cases, heads etc etc..

 

[roy the mechanic]

Hi, shaun, as your motor is 62 years old, the last thing you need to know is-"how fast it goes"! If, with the help of trusted professionals, it becomes reliable thats about all you can(should) expect ot the poor old thing. WE are only the custodians, one day we all have to hand them back! I reckon stand back, consider whatYou want, build with the future in mind. most of all- enjoy, REgards, roy.

 

[Tnecniv Edipar]

Some inspiration for you :-

 

[Howard]

Hi, shaun, as your motor is 62 years old, the last thing you need to know is-"how fast it goes"! If, with the help of trusted professionals, it becomes reliable thats about all you can(should) expect ot the poor old thing. WE are only the custodians, one day we all have to hand them back! I reckon stand back, consider whatYou want, build with the future in mind. most of all- enjoy, REgards, roy.

Good advice.

I've put my Egli back as it was in the 70s. It's not as fast as the best sports bikes, as it was then, but it's great fun.

H