Ducati Sporting Club UK > DesmoDue Race Series > DesmoDue - General Questions and Chat > decision on big bore ???

[antonye]

Originally posted by dickieducati
*** CORRECTION ***

you were quicker than me at the first meeting.


*** CORRECTION ****

Three times....

[TP]

Originally posted by fil2

Moaning my arse mate..........

:P

[Edited on 3-5-2005 by fil2]

You got me before I edited - re-read it and see if it makes more sense.

If not then I'll just STFU.

I'm tired ....

[dickieducati]

mickey mouse bloody circuit anyway!



no, its a fair cop you beat me fair and square.

suppose, you're going to open a can of whupass on me at snetterton too.

[fil2]

Originally posted by TP
I think the benefits of the 620 big bore are being overstated. I was speaking to Geoff on Sat night and his bike is making 62 bhp at the rear wheel. Any well sorted 620 is making the same. Geoff may have a better curve, I haven't seen it, but I don't think the difference is that much.

Big bores on a 620 are expensive and IMO the marginal gain is not worth the cost.

Another way of looking at it is this. Geoff's bike and mine are the same horsepower (well mw's bike was dyno'd at 62 and they were setup almost identical so mine would be the same) so I don't think the slightly better power and torque curves he has would give him the 3 to 4 seconds a lap he had on me on the woodlands circuit. He's just a much better rider - simple.

If I had chosen a 675 as my weapon of choice I'd have done the carb mods that no-one seems to have done as well, all the tuners say that this will even the performance between the 675's and the 620's. I have no idea how much this mod costs but if I was one of you lot I'd be looking into it.

If Phil and Ali had this mod I wouldn't be surprised to see them go past me and Nick and gap us, as it's fairly even between us at the moment.

Now stop bloody moaning! (Caveat - humorous dig, not a stab at anyone before my head gets bitten off)



[Edited on 3-5-2005 by TP]

LMFAO..its all i can manage at that tony..sorry m8

[TP]

I think I might just STFU anyway ....

[ali]

Originally posted by TP
I think the benefits of the 620 big bore are being overstated. I was speaking to Geoff on Sat night and his bike is making 62 bhp at the rear wheel. Any well sorted 620 is making the same. Geoff may have a better curve, I haven't seen it, but I don't think the difference is that much.

Big bores on a 620 are expensive and IMO the marginal gain is not worth the cost.

Another way of looking at it is this. Geoff's bike and mine are the same horsepower (well mw's bike was dyno'd at 62 and they were setup almost identical so mine would be the same) so I don't think the slightly better power and torque curves he has would give him the 3 to 4 seconds a lap he had on me on the woodlands circuit. He's just a much better rider - simple.

If I had chosen a 675 as my weapon of choice I'd have done the carb mods that no-one seems to have done as well, all the tuners say that this will even the performance between the 675's and the 620's. I have no idea how much this mod costs but if I was one of you lot I'd be looking into it.

If Phil and Ali had this mod I wouldn't be surprised to see them go past me and Nick and gap us, as it's fairly even between us at the moment.

Now stop bloody moaning! (Caveat - humorous dig, not a stab at anyone before my head gets bitten off)



[Edited on 3-5-2005 by TP]

If I had a 620 this would be my view too. It would also be a steaming pile of do do!

Three BB 675s have been dyno'd and not one has made more that 51.8bhp. By your own admission MW's bike is making 62bhp. I have spoken to just about every Ducati tuner in the land, and couple in the US/Aus, and every single one of them say the same thing:

"The difference is valve diameters is so great that the only way you'll ever get close to a 620 is to do some serious head-work"

Believe me, I've looked at:

shorter inlet manifolds
keihin 39mm flat slides
dialling the cams
advancing the timing
using bellmouths
forced air induction

and the most optomistic estimate is 1.5 - 2bhp improvment.....for £1700!

Given that I believe none of us have £1700 to bin on mods we'll all be sticking with 51.xbhp, while the 620s will all be on 59-62bhp.

If you think that's a level playing field then you need a new spirit-level!

Sorry about the thread hijacking.

Cheers,

Ali

[antonye]

The Flatsides route is a fair comment BUT - (a) you have to source them and (b) you have to pay for them and (3) you have to get them fitted and spend time getting them setup.

As one of the very few places that sell them as a kit charge nearly $800 (less shipping and taxes, vat and import duty!) you're talking in the region of £600 for parts alone.

My understanding from the beginning of this was that a big-bored 600 *WOULD* be competitive with a 620. End of story.

Now it's becoming apparent that I should have just bought a 620 in the first place as getting a 600 competitive will cost more anyway!

Yes, I am moaning. I feel like I've been fed false information and it's already cost me points in the championship - that's what I've entered for.

[mw]

i believe all this histeria about a big big bore kit is rider perception not fact ...

the 620 big bore kit gives only v v slight power increase but it does give a wider power band and slightly more torque ... all to keep it on a par with a v well set up big bore 583 (it is not just about fitting a big bore kit and instantly getting the power to be on a par with the 620's you have got to sort the carburation (shorter inlets and flat slide carbs) and set it all up correctly ).

the rules were formulated to allow people 2 choices either don't fiddle and fettle and buy a 620 or buy a 583 and work to get it on a par ... infact the feeling is that the big bore 583 with correct carbs and set up would beat a 620 on power and torque ... hence having the big bore 620 option is important as this would (if you wanted to spend the money) allow one to get even ... it's all v close thou' so the extra expence probably wouldn't be worth it unless running v close to winning the championship ...
the expected power outputs of a sorted big bore 583, standard 620 and big bore 620 are all around 62 -65 bhp however all this about different dyno figures is also very misleading as each dyno has a different reading to the other ... they are useful in evaluating dif engines run on the same dyno as a comparison but not worth it between dif dynos.

also look at sigma's article on the desmo due rules to see the background.

i was overtaken by geoff at the old hairpin near the end of the 2nd race and i was overtaken by the dls/dlc bikes at barn ... eg all within a short distance. geoff has a lot of local knowledge which i suspect the others haven't ... in qualification he was 0.6 secs a lap faster, at end of race 1 he was 7.12 secs clear (about 0.6 a lap faster) and at the end of the 2nd race he was only 3.35 secs clear which means a less than 0.3 sec a lap advantage ...i don't believe that's a power advantage .. that's local knowledge ... and what everyone seems to have forgotten ... rider ability (he is a v good rider who used to race against the baines's and beat them!) it all seems to me a great shame that everyone is concentrating on the hardwear issues and taking away from geoff what was a well earned and deserved win in both races.

for what it is worth i believe changing the rules so quickly as a knee jerk reaction would be wrong ... it's just too soon ... we need to see how it goes at the next race at the v least before looking at any changes...

riders also need to look at their riding and not their machines for the fact that they were slower than the bike infront ... alan johnson on a 583 came 5th and 6th.

[ChrisBushell]

Folks,

I have spent all of today since 08.30 working on this issue, beleive me the phone bill is going to be horrendous!

We are making progress and should be able to come back to the racers before lunch time tomorrow. I have a series of further planned phone calls to make this afternoon to obtain a conclusion!

We will be back to you as soon as we can, "keep the faih"

Chris

[TP]

Originally posted by ali
If I had a 620 this would be my view too. It would also be a steaming pile of do do!

Three BB 675s have been dyno'd and not one has made more that 51.8bhp. By your own admission MW's bike is making 62bhp. I have spoken to just about every Ducati tuner in the land, and couple in the US/Aus, and every single one of them say the same thing:

"The difference is valve diameters is so great that the only way you'll ever get close to a 620 is to do some serious head-work"

Believe me, I've looked at:

shorter inlet manifolds
keihin 39mm flat slides
dialling the cams
advancing the timing
using bellmouths
forced air induction

and the most optomistic estimate is 1.5 - 2bhp improvment.....for £1700!

Given that I believe none of us have £1700 to bin on mods we'll all be sticking with 51.xbhp, while the 620s will all be on 59-62bhp.

If you think that's a level playing field then you need a new spirit-level!

Sorry about the thread hijacking.

Cheers,

Ali

If that's the case then my comments above were based on a misapprehension. My understanding was as I said - that these mods would make the 675's competitive. If that's not the case then I humbly retract my comments above.

I would also add that this changes my view of the riders over the weekend and my hearty congratulations go to you and Phil for what in reality were fantastic rides. And a standout effort from Andrew Johnson on a 583.