The comprehensive GRiSO exhaust thread....

Axael wrote:

The pretzel midpipe is the part which is doing some "S" curve on the stock exhaust, right? Thanks for the advice, I didn't know that was so important.

That's it. You lose all your low and midrange torque if you remove it.

Many thanks for the info. I thought I already read that in this topic, but I didn't remember it. Nice of you to remind it to me before ordering anything :p

So, still in the game for me:
- the simple Agostini Conical exhaust (for the profundo basso)
- the Termignoni which I guess isn't bad
- the Arrow which seems fine as well

@Beetle: the simple conical Agostini is the one you call "Megaphone" on the GRiSO.org maps?

Any other recommandations?

My 2¢...forget the Termi.

As for the Agostini, the answer is "yes".

Short and clear answer, thanks!

I'll ask the price for the Agostini. I'm already a customer knowing I bought their exhausts for my MGX, si maybe I can have a bit of a discount.

Been running Ago Xblack, works well and had it mapped. Ago comes with removable cat and db killer
Don’t find it too loud. Weight is much less than the stock trombone.
Had the ago midpipe/pretzel but removed it long ago. Midrange torque is better and suits the GRiSO personality

Well just received an answer from Agostini. They're offering me the stainless steel conical exhaust for 500 euros tax and shipping included. That's a fair deal, so I think I'll get that one.

When you say you "had it mapped", I guess you mean the motorcycle itself, as you'd do with the GRiSO.org maps?

Seams like a good deal. Yes I had someone map my bike since I don’t have guzzidiag cables yet. Beetle Probably has a good one or place to start

For what it’s worth I found that the CAT had become loose in my Termignioni so I removed it - crikey what a massive improvement in bottom and mid range.

I have noticed that some of these exhaust silencers / mufflers, especially the underbody shorties are little more than just spark arresters. They cannot possibly supply any back pressure to an engine that was designed to run with at least a little bit. My fear in switching over to one of these is the possibility of sucking some cold air back up the very short distance to an exhaust valve on scavenge, and the havoc that may result from that! Am I over thinking any of this?

Apart from the fact that there is no such thing as 'Back pressure' no.

The head design and cam timing, especially on the 8V, do not favour a short pipe. They may look 'Cool' but they will gut the bottom end and midrange even with a suitable map. The exhaust harmonics are all wrong with a short pipe and the bike will run like a mad woman's shit.

Thanks Pete Roper for clearing that up and offering additional facts on shorty pipe performance.

Groovitz wrote:

Thanks Pete Roper for clearing that up and offering additional facts on shorty pipe performance.

He doesn't call a "spade a spade", he calls it a fucking shovel. And we'd have it no other way.

I just went for a ride with the Arrow, swapped directly from the esteemed Mistral hi-pipe...

My experience corroborates what's already been noted here repeatedly: the Mistral with dBk (and corresponding beetle map) provides the strongest low -> mid RPM acceleration. Removing the dBk (and changing the map) results in a noticeable loss of performance down low, but (much) greater thrills when you whack open the throttle above 5k RPM. I also felt a bit more vibration without the dBk (which seems understandable).

I'm actually shocked by how dissimilar these two setups are, it's a completely different bike switching from one to the other.

The Arrow performs similarly to the Mistral sans dBk. However, I *really* like the Arrow's noise vs the Mistral: a nice throaty growl between 3 and 4k RPM, the sound is very slightly louder and subjectively more pleasing, yet it's quiet while cruising--no obnoxious, farty drone like the Mistral sans dBk, which sounds a bit like my dad's '87 Honda Shadow with gutted factory mufflers...  

So far I'm thrilled with the sound, hopefully I'll acclimate positively to the performance changes with more miles.

Thinking exhausts one must remember we are dealing with impedance and definitely not back pressure - please keep the terminology right, or better, or not back pressure at least. Shut up Tony.

Yes. Shut up.

No such thing as back pressure. Please use the term "reflected pressure wave".


And use your dB killer.

I run the Mistral High Pipe in titanium finish, Beetle Map and the stock dB killer in, but i drilled out the smaller end hole to 8 mm equal to the holes on the sides. Sounds awesome and fueling is excellent! The Stelvio setup looks pretty identical to the BOS 2-1 SS system i had on my dear old Sporti, and the oil cooler in front. I love the way the GRiSO looks with the oil cooler on the side but then you see an 850 GRiSO and then the engine just looks so clean... life is complicated...

I have a 2017 GRiSO with an Arrow exhaust that is too loud for me. Suggestions on how to quiet the sound?

Does it have a dB killer? If not, get one. If yes, aftermarket dB killers can be found on eBay and other online retailers. You might be able to find one that has less or smaller holes.

I'm surprised by how loud the Arrow is as delivered with the insert installed--in a different league from the Mistral (also with dBk, which is similar to stock).

Personally, I absolutely LOVE the sound, it's really amazing and adds a lot of positive character to an already unique machine, and of course with Beetle's map it runs absolutely stellar. (In fact, I haven't ridden my Tuono in weeks now, as lately I prefer the GRiSO!) It is, however, just a tad too loud at times, though not enough to make me consider reinstalling the Mistral.

So are you still running the Mistral map?

sideshowbob wrote:

So are you still running the Mistral map?

Yes, I switched back to the the Mistral no-dBk map, which (according to Beetle) is equivalent (or nearly equivalent) to the Arrow map.

Performance is truly better than I expected. It pulls well from the bottom up to 4k RPM nearly as well as the Mistral with dBk. There's a very, very slight "fluffiness" from 4k to about 4.7k RPM, which I attribute to the nature of the more "open" exhaust VS stock and the Mistral, though this quality was actually more noticeable running the Mistral without dBk. (I've found that perfect valve adjustment and tb sync greatly minimizes this particular trait.) From just under 5k RPM to redline... wow! It's fantastic, definitely more top-end than the Mistral+dBk. (<-Perception can be deceiving here, so take this for what it is, though I'd confidently wager you'd see a small difference on the dyno.)

Both idle quality in summer weather and part-throttle acceleration/throttle response is better here with the fuel trim bumped to +1. Cold idle is a bit irregular, though this may just be the nature of the beast. If necessary, you can ride it from stone-cold with no hassle. Fortunately, I have access to ethanol-free gasoline in my area, this again makes a quite noticeable improvement.

All this during 90 degree weather, and at 4500 feet elevation. Would love to have a ride up and down the coast...

Well, I was going to buy the Agostini exhaust for my GRiSO considering your advices here. However, it looks like more and more EU countries are beginning a fight against motorcycle noise.

Long story short, some places now forbid motorcycles that are lourder than 95dB (measurement procedure varies from one country to another...), others are allowing motorcycles to emit the amount of dB that is written on their frame / homologation papers, and nothing more.

Soooo, it looks like getting an Agostini might not be a good idea anymore, since it's not EU Homologated, as far as I know.  However, it looks like the Mistral conical exhaust is...

So, question is: is the Mistral conical exhaust still fine when it comes to performance (without looking for the best performance possible, but at least as good as with the stock exhaust)?

EDIT:
Well, apparently the Agostini's (at least the ones for the GRiSO) are now homologated as well in EU. I'm leaving this message as it could help other EU people in the future.

Does anyone have an idea of what this is? I'm looking to maybe buy it but not sure the brand or anything and the seller isn't sure either. Any thoughts?[You must be registered and logged in to see this image.]

Could be a Mistral Stainless. Mind you the mistral has a welded bracket and not an adjustable strap. Mivv you don't get the extra length of pipe with it. GPR?

GPR, I think.