Different exhaust temps

[utopia]

Yep, points taken .. I concede.
It does look like the rear header favours the right hand silencer to a fairly noticeable extent, and even the front one does to a small extent too.
A picture speaks a thousand words, eh ?
I should have gone into the shed and studied my old headers instead of working from memory.
I must admit that I was already considering that the initial bends towards the right hand side might mean that the gases would tend to hug that side of the pipes, even though they straightened out further along (memory says this might be called the Coanda effect).

Anyway, yep ... it does look like the flow favours the right hand silencer.
Which tallies with Alan's experience of that can feeling hotter than the left hand one.

[Mr Gazza]

Originally Posted by utopia

Yep, points taken .. I concede.

Now I feel like I have bullied you into submission! Which was not my intention... Sorry.

I've often pondered making a new cruciform out of mandrel bends and then transplanting it, by making a jig to hold all the pipes in position before cutting the old cruciform out. I can't help thinking it could be a recipe for disaster. I have found a more practical looking DIY idea whilst searching Google images. I daresay a few will have seen it before, but the idea appeals to me.. How hard can it be?

[utopia]

Originally Posted by Mr Gazza

Now I feel like I have bullied you into submission! Which was not my intention... Sorry.

Not at all .. you have merely presented a more clarified rationale, which has deservedly won me over.

However, I'm inclined to agree with "350" that the modified crucifix you refer to will only result in the exhaust flow from each cylinder fighting each other.
Mind you, I have cut up a std crucifix and the bifurcated exhaust tracts ( oo'er) within it do look extremely narrow and constricting ... and very tightly curved too.
It certainly looks like it would benefit from modification of some sort.
For an off the shelf solution the MADASL headers are probably the way to go .. if you want to retain both cans.

[Mr Gazza]

Would both of you please pay more attention!.. now I am bullying you..

I didn't think the pictures required any explanation but I've found another which shows a piece of box in the middle. The first pictures clearly have a "star" shaped piece here made of 4 bits of pipe section. So it's still working as a cruciform but with less restriction.



As it happens the images come from another forum and were posted by our own Nasher.
Gilps from here too, commented that the mod did not work on his and other's 600 and 620 DD racers and did not recommend the mod.
However on yet another thread someone tried this on an SS1000 and claimed better low down and mid range power at the expense of top end. (Hence why they didn't like it on the racers I imagine?)
I am mildly tempted to try this on a spare exhaust, and maybe even try and position the "star" to bias the rear exhaust to the left a bit.
Many other comments claimed that the original cruciform is not restrictive at all and is carefully designed for the best performance.
I would kind of go with that to some extent as, if you are going to bifurcate a pipe, then each bifurcation needs to be half the area of the main pipe to retain the same flow. this is what appears to be happening in the standard cruciform, so a big part of me is saying if it ain't broke...

[Dukedesmo]

Originally Posted by Mr Gazza

I have found a more practical looking DIY idea whilst searching Google images. I daresay a few will have seen it before, but the idea appeals to me.. How hard can it be?

I modified mine in this way, here's a pic of it finished;



But although it (must have) flowed more freely due to the bigger bore it still noticeably blew harder out the right pipe than left - perhaps more so?

I have since replaced it with a Spaghetti style crossover (from Madasl) which is definitely better flowing, plus at 45mm it's 5mm oversize;



I meant to get to the dyno to get things checked but never got round to doing so but it's definitely an improvement.

[Flip]

Yep replaced mine too with a pre-Ducati Performance, Gio.Ca.Moto set of front pipes bought new old stock years ago.

Not quite as intricate as a full spaghetti system but a much less restrictive join.

I'm not sure what the gain (if any) might be on this but the long since unavailable Sil-Motor spaghetti system used to quote a 5bhp gain all through the mid-range on a 900 motor.