New pipe and 'Lip'.

I had a Mistral Hi-Pipe on the GRiSO Pinko in the US and really liked it. A few weeks ago on a whim I decided to try one on the Green Horror.

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CF is ridiculous overkill but it does look grand.

I also am experimenting with a small 'Lip Screen' on the top of the large factory screen. It works quite nicely but its as ugly as a bucket full of bashed crabs!

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Pete

GRiS0's looking good Rope!

GRiSO always looks good. Even with me on it!

Pete Roper wrote:

GRiSO always looks good. Even with me on it!

With your helmet on right?   

I'm really tempted to use a dual high pipe like BOS but I'd have to engineer the clearance with my Givi mounts if at all possible...

did a Burramys parvus chase you up on the roof to take those pics  

Well, I just went out for a quick flog around the houses after taking the dB killer out of the Mistral.

The rule of thumb is that sticking a 90 degree bend in a pipe is roughly equivalent to adding a metre to the length of the pipe in terms of resistance. Seems to hold true! Unlike most pipes where taking the dB killer out turns the 8V GRiSO into a vibratory, thirsty pig the Hi-Pipe works very well with the killer removed. If anything it pulls even harder than the Termi with no increase in vibration and certainly not an offensive increase in noise.

Certainly with Mark's map, (I'm still running the DE 63 iteration.) it runs superbly. I have yet to fill up so I don't know what effect it will have on fuel consumption.

Pete

Pete Roper wrote:

Well, I just went out for a quick flog around the houses after taking the dB killer out of the Mistral.

The rule of thumb is that sticking a 90 degree bend in a pipe is roughly equivalent to adding a metre to the length of the pipe in terms of resistance. Seems to hold true! Unlike most pipes where taking the dB killer out turns the 8V GRiSO into a vibratory, thirsty pig the Hi-Pipe works very well with the killer removed. If anything it pulls even harder than the Termi with no increase in vibration and certainly not an offensive increase in noise.

Certainly with Mark's map, (I'm still running the DE 63 iteration.) it runs superbly. I have yet to fill up so I don't know what effect it will have on fuel consumption.

Pete

For fucks sake. If this is true, I'm going to have to fork out for this pipe too.     

When I ran the stainless version of this pipe on the GRiSO Pinko in the US it didn't come with the option of a dB killer as the pipe was already on the bike sans dB killer when I had it delivered to LA. Running the 68S map I was pleasantly surprised as to how similar its behaviour was to that of the Green Horror with the Termi and dB killer combination it was running by that time. It wasn't offensively loud either. I don't know whether the Mistral has a cat-con or not?

Pete

Pete Roper wrote:

When I ran the stainless version of this pipe on the GRiSO Pinko in the US it didn't come with the option of a dB killer as the pipe was already on the bike sans dB killer when I had it delivered to LA. Running the 68S map I was pleasantly surprised as to how similar its behaviour was to that of the Green Horror with the Termi and dB killer combination it was running by that time. It wasn't offensively loud either. I don't know whether the Mistral has a cat-con or not?

Pete

no cat...was that what had you on the roof when you took those pics?

The Mistral website doesn't have any info, but I would think there must be a catcon, otherwise even with the extra bend, it wouldn't run right.

I'm working on a map for a GRiSO with a Zard race pipe, which has a dB killer but no catcon. The bike vibes around 3000rpm, which I think is due to the lack of catcon.

Nah, if Rosie had a Camera she could of taken the pics, we had to put her down yesterday. Mind you, being Rosie I reckon she would of been going down not up

Pete

Hoi,

I have this Mistral pipe from the beginning on my G12.
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The only cat I have is... my gardian...
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The Harley is out allready.
With the original DB killer in place I had nearly 10 Hp less than without this thing.
Measurerd onto a powerbench...
I listened to the experienced tuner and made a Db killer myself.
It's bigger, more open, not blocking the flow (to much...).
It works, my G12 is not loud, substancial less loud as without the Db killer.
And the power feels good.
At this point I don't know how much power is gone by this Db killer.
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As far as noise is concerned my two wishes are that when I ride, with ear-plugs in, I should be aware of the sound of the engine but it mustn't be loud enough to become a nuisance or a pain on trips over half an hour in length. Secondly it must not be offensive to or interfere with the enjoyment of others. Noisy morons give me the shits. There is no need for anything even remotely 'Modern' to be noisy! Especially in built up areas I like to be able to creep along in 'Stealth' mode without annoying people or attracting the wallopers!

Also verboten is anything that makes a machine run poorly. Unfortunately this means the vast majority of aftermarket pipes run without a catalytic converter and dB killer on the GRiSO. I'm still open minded about some other models, the 1200 Sport 8V and Norge 8V have a huge collector-cum-cat under the gearbox and this seems to offer ample impediment to the charge transition problems encountered when 'Opening Up' the pipe on a GRiSO. Whether they will run better with or without a dB killer I hope to find out through the process of elimination over the next few weeks.

Pete

Beetle,

I have a 2013 8v GRiSO with about 400 miles on it.  I've been reading your and Pete's work with great interest.  I'm not a fan of the stock pipe look so put a Zard on it (no catcon, but has db killer).  Your remark of vibration at 3000 rpm is spot on with my 100 miles of experience so far with it.  Very distinct at that rpm (even vibrates the instrument cluster).  Overall, while I'm not satisfied with performance below 4000 rpm, it fuels ok.  It just sounds "off" below 4000.  It's like an old 2-stroke getting on the pipe once it hits 4000 rpm - feels and sounds like it is finally running well.

Again, thanks for all of your and Pete's work and look forward to hearing more about your map tweaks for a Zard-piped 8v.

Ted

OK, so no catcon in the Mistral. Even with the extra length and 90 degree bend, I reckon the charge transition problem would be evident. It may be that the silencer itself is more restrictive in it's design than the Termi. Yes?

TRw1 wrote:

Again, thanks for all of your and Pete's work and look forward to hearing more about your map tweaks for a Zard-piped 8v.

Ted

Stay tuned Ted!

Hard to tell exactly what it is. Both physical attributes and harmonics are going to vary from pipe to pipe, some just seem to work better than others. Overall length is greater with the Hi-Pipe as well which is another factor to consider.

Pete

A longer pipe creates a higher impedance - it also lowers the resonance, as you have said Pete. Back in the dark ages (the era of pommie bikes) it was a well known fact that if you lengthened you pipe(s) the power comes in at a lower frequency (rpm) - or so I have been told - I am not old enough to remember pommie bikes, or the blokes that tuned them. Mind you I did have the odd BSA or three - and they were odd!

Tony - my $0.02 worth

Speed of sound is effectively a constant so the time it takes for a pressure wave to reach the end of the pipe and return to the exhaust valve remains pretty much the same. As the engine speed rises and falls the length of the engine's cycle increases and decreases meaning that the returning pressure wave may or may not coincide with the closing of the exhaust valve meaning the point of peak volumetric efficiency will vary with engine speed and pipe length, (And with four strokes to a lesser extent than two strokes with pipe shape.)

The vibration felt at 3,000-ish RPM with some cans without a dB killer or catalytic converter, (The converter in and of itself will fragment the pressure waves making 'Back Pressure' less of an issue.) is IMHO probably a result of this being the point at which the sonic pressure wave that at certain speeds will be trying to force the egressing fresh charge escaping past the exhaust valves back into the combustion chamber is in fact doing the opposite and actively creating a low pressure area in the exhaust port which will be dragging the fresh charge out. This will result in low volumetric efficiency and a leaner mixture and hence the vibration and harsh feel at that point.

The use of a honeycomb cat will decrease the effect of this over-scavenge as will a dB killer while at the same time adding physical resistance and a higher overall pressure in the pipe which in turn will dissuade fresh charge from simply transiting the chamber, something it is very want to do with the Guzzi 8V due to its side-draught head design, narrow included valve angle and long valve overlap.

As I have said before one has to look at the entire engine from airbox to tip of exhaust holistically. Simply trying to address one issue or relying on a sole input to make tuning decisions means you are on a hiding to nothing.

Pete

I was going to get one of these Mistral pipes and then spent the money on new valve covers. Well, I'm bloody well going to get one now!

  

The Mistral isn't some sort of 'Tin Miracle' and I'm sure that there are many other pipes that will work similarly, I haven't tried them all by a long chalk. What I have found is that the Mistral does work very well and for whatever reason doesn't seem to suffer in anywhere the same degree from the problems that many other cans do if run without a dB killer.

Universally though I've found that the louder and 'Less inhibited' the pipe and the more the airbox and air filter are screwed around with the less pleasant the bike is to ride and the poorer the fuel economy. The worst example of this was the Guzzitech pipe which was of very large diameter, un baffled in any way and ear-bleedingly loud, it wasn't helped by the fact that it was too large on the inlet to run without a gasket but not large enough to run with one so air ingress screwing with the O2 sensor input while running closed loop would of made it run like a dog. It would of been ten times worse with an open airbox I'm sure! Its a great shame as I loved that pipe, itlooked fantastic and was beautifully made. It just was all wrong.

To a lesser degree I've found the same to be true of all the 'Straight' or 'Conical' mufflers I've tried. Run them without a dB killer and you get a bomb-crater sized hole in the midrange, vibration and lousy fuel economy! In the case of some of them even if you prefer 'Loud' the tonal quality is shit! The Staintune can is a typical case in point. Remove the dB killer and its a lot louder but it still somehow sounds harsh and 'Tinny'! I have no idea why? Perhaps its something to do with the gauge of the steel its constructed from? Thing is very similar cans on a V11 or VTR have the most gorgeous 'Basso Proffundo' thunder, once again I have no idea why.

At the end of the day what will work and what won't can only be discovered by experimentation. Gotta go. Chores to do...

Pete