Modified Carbs and Airbox Mods.

[koko64]

[/url]2013-10-30 21.34.41 by Tony Kokonis, on Flickr[/img]

2013-10-30 21.34.41 by Tony Kokonis, on Flickr

Hope that helps Gert.
Cheers

[koko64]

Pepe`...did you lengthen those manifolds?

Pepe said he used modified oem, so they must be cut n' shut.
They must be angled to avoid the cross braces I guess.

[ducpainter]

Pepe said he used modified oem, so they must be cut n' shut.
They must be angled to avoid the cross braces I guess.

I meant shortened...

The reason I asked is because Eric says the real power gains from using FCR's comes from the shorter manifolds. The FCR's on stock manifolds just provide better response.

[koko64]

That is true from dyno charts I've seen when Hord and Lofgren tested short manifolds. The torque curve gets moved up the rev range to make more hp.
I do like the long manifolds on a street motor.

[koko64]

https://www.hordpower.com/gallery3/index.php/Dyno-Charts/album07/manifolds

http://www.lofgrenperformance.com/carbs.htm

[koko64]

How are those split carbs going Pepe'?

[Speeddog]

I just noticed what he did there.

And I'm totally going to do that when I try this mod.

[koko64]

Angling the manifolds to clear everything is the issue. Easier on a Supersport so I'm waiting to see how Pepe' does it. I gave up on doing this on an M900 even after I seperated the carbs using two donor sets. I slapped em back together
I figure if I was going to all the effort of running split singles, I would use TM38's, TM40's or FCR's. No matter, me cracking the shits is no precedent for others more skilled and motivated like Pepe'. I'm glad that Pepe' is having a crack at it. Go Pepe'.

[pepeducat]

I have a friend who has cut down the piece of frame that hindered the assembly of carburettors in split.Il found no difference in handling of the bike.

http://ducati-mostro-forum.fr/index.php?topic=1383.msg66310#msg66310

[koko64]

Ah, I understand. I thought you had found a way to clear the frame spars with custom, angled manifolds.
Looking forward to your results with the split carbs.

[koko64]

Just my opinion. I try to mitigate the higher rpm restriction imposed by the long manifolds rather than lose the low rpm grunt by shortening them. I believe the long manifolds are not only too long but actually too narrow in diameter in relation to their length. I open up the inner diameter and port them to taper down to the inlet port to help flow and increase their total volume (and reduce unhelpful high rpm resonance). I also shorten the rubber V stacks and open up the volume of the airbox to counteract the restriction on high rpm torque imposed by the manifold length. It lessens the negative high rpm resonance and terrible eddying in the "right angle"airbox.

I only know this because of what I could extrapolate from others' testing and research who are smarter than me.

[koko64]

Gert
A 33-2060 panel filter fits nicely into the carbed airbox lid and just covers the snorkels at it's widest length while not being too long. I used a K&N filter guide searching via dimensions on their site (Speeddog put me onto it). .

[koko64]

Just a tuning update.
I ended up going for the softest CV slide springs available for that kit. I was using the oem springs with good results in the low rev range but this ported carb will not rise quickly enough in the 1/2-3/4 throttle and rev ranges with oem springs. It is either a change in resonance in the extended air box or the actual porting of the carb that is causing the need for soft springs. Either way, the carb feels great and has picked up a great deal if midrange torque. The response is very good possibly at a slight loss of response right off idle. With the absence of slide flutter with this mod I am very happy with the outcome. 37.5 pilot/slow jets, needle posn #3 with D 730 needles (stage 2 kit), 165 mains and IMS out 4 & 1/2 turns.
I have had to revise my use of stock springs which may still work better with 600 & 750 models in the 38mm carbs for those capacities. I would not bore these carbs even if I was equipped to do so in order to put corner exit response and acceleration as priority One over peak hp numbers. I can run the revs lower now and grunt out of corners on these cams and long manifolds.

These carbs feel really good now. I'm a little surprised how well they work.

[koko64]

Going to try Factory Pro needles and springs. They have a kit for open airboxes. Might just try the springs first on a hunch. Then test needle/spring combinations to set mixture  and slide opening speed over the midrange throttle range.

[Howie]

Anyone old enough to remember the SUs?  Tune rise by changing the weight of the oil.