Breva 1100 exhaust mod

Sorry its not a GRiSO.
Just gutted and shortened std breva exhaust to lose weight and open up back wheel.i like the look and lost approx 8lb in weight.it has removeable baffle that i may need to alter i still have the collector box in place and have been running a beetle map with after market exhaust without issue but dont like the look of the aftermarket hence the project.all was ok until bike got up to temp then started spluttering and died off.wondered if this could be back pressure issue i will post pics
Cheers craig

Groan.


Say "back pressure" again, and you're dead to me.

The colostomy bag on the Breva does most of the silencing functions. Wot ever you hang on the back is almost superfluous.

Ok
Not sure why the bike died then.
Ran it up with my existing exhaust no issue.
Then swapped to modded exhaust and after 10 mins of idling it died off.
It is torrential rain here so no road test yet.
Any ideas people.
I believe my map disables the lambda.
Craig

I think it simply doesn't have enough fuel when it's hot. You can typically delete the collector box with a y-pipe, and it will run OK, but somewhat more lean with the stock pipe. Shortening the pipe has basically allowed the exhaust to escape at full speed ahead, and the incoming charge is probably being sucked right out of the combustion chamber. You need to either:

a) slow the exhaust gas down

..or

b) remap.

Hi beetle
I have 1 of your maps on it.
Can this be altered or is that a hassle.
It seems to die when left at idle.
It did this with baffle out.
I need to try it again with baffle in which is what i would prefer.the baffle in is a bit raspy i think it needs the tube perferating.
Cheers for help
Craig

Get the baffle right. It will help immensely. Once your happy, I can tweak the map. It's not a problem.

Hi Beetle,
If its not 'back pressure' then what is it, is it to do with the exhaust pulses. How does it work so you can write the maps etc that you do. Just trying to understand how exhaust mods effect the running of a bike, is running a 2 into 1 a good idea or is it better to run a 2 into 1 into 2, or keep the stock exhaust.
Also does the length of the muffler affect how a bike runs/performs etc, your thoughts please.

Regards
Alan

Back pressure* is a bad thing.

The 2 into 1 will produce more torque than a 2 into 1 into 2, and a 2 into 2 with crossover. What we want to do is control the exhaust gas speed. We want to slow it down at certain points in the rev range, and speed it up in other points. Now, you can do that with 2 into 1 into 2 (and 2 into 2 w/crossover) by changing the diameter of the pipe and adding bends at the right place, using reversion cones and the right sized dB killer. You also get a good note. However, it's not as effective for performance purposes, as the 2 into 1. And by performance, I mean torque. Pipe & muffler length, diameter, bend radius, & number of bends, all play a role in exhaust tuning. Each change in diameter, bend and even join will cause a reflected pressure wave, both of gas and sound. Each reflected pressure wave will impede the outgoing gas by a certain amount. That is why the exhaust design is keyed (well, it should be) to engine design.

Each exhaust cycle produces a packet of gas that travels at a speed determined by the RPM. Each packet of gas has a little area of vacuum behind it. The higher the RPM, the faster the gas, the more vacuum. We get the best scavenging effect at high gas speed. For drag racing, straight through pipes are best for high power at max RPM, along with fuel guzzling. No back pressure there. However, for road going vehicles, we want to keep the charge in the combustion chamber until ignition. For the 8V, slow exhaust, especially at low RPM is vital. For the 2V, it's not as critical.

A well designed 2 into 1 will compliment the engine by allowing the resultant exhaust gas velocity (after all the impedance affects) to result in optimum torque by allowing the 2 cylinders to work together. The 2 into 1 into 2 has the added complexity of extra bends and joins, which will create more impedance, but with the disadvantage the wrong timing. The 2 into 2 with crossover is even less efficient. No crossover? Just don't.



I hope this rambling makes sense.








*Back Pressure. Whiny know-all's please fuck off. For gas to leave the exhaust, the pressure at the engine end has to be higher than the pressure at the open end. The less work the engine has to use to force gas out, the more it can send to the rear wheel. Back pressure is working against the engine. Ergo, bad.

I think I almost understood that. Almost. Thanks Mark.

Thanks for the advice beetle.
I will play around with the baffle a little and see if i can get any were with it.
The exhaust mod was just an experiment but i do like the way it opens up the rear wheel.
Craig

I get it, and despite my apparent crankiness, I will help any way I can.

Any kind of crankiness is fine when coming from people who have the knowledge to back it up.just for the record my breva runs a beetle map that is fantastic this is how the bike should of been from new.but like a lot of us winter is a time for tinkering !!!

I guess i assumed with having the collector box still in place that most exhausts would work.the main difference with my aftermarket and my modded exhaust is position of baffle.aftermarket the baffle is at the front of exhaust just after link pipe.my modded exhaust the baffle is at the end of the silencer conventional also aftermarket baffle is perferated.
Craig

Hi ,
Dave here from Adelaide , and I just found this thread. Im a long time Guzzi tragic ( since 1984) - recent convert ( haha ) to fuel injected ones, well its been 10 yrs now on the 05 Breva1100 . so I am discovering via Forums like this + Guzzi Diag , morgan carbtune etc yes I can do all I need to service the bike.
I have successfully reset TPS , so now wonder about remapping ? I'm Old school mech , so one step at a time has been the way. Breva lost the colostomy bag a few years back with a Guzzitech y pipe , didn't help lose the heat on the ankles much tho. Last week I fitted a Dominator Muffler ( from poland) , its nicely made , lots lighter than stock. Bike runs fine it would seem - plug colour is still on the dark side . Seems wierd as it must be so lean to run so hot ?
on the Guzzi daig tells me my map is 2230BA10. Tips and comments all welcome
Thank you for all you do for fellow Guzzisti

Mark,
Thanks for the clear explanation of exhaust tuning.

Guzzitragic
Speak to beetle about a map very easy to install and brings the bike to life.

Just tried exhaust again with baffle in and the bike did not cut out.
Once warmed up it dropped to 800 rpm and ran rough but at least some improvement.altering the baffle later see if that helps then maybe a butterfly valve in the link pipe so i can alter flow of gases.
Thanks craig

Thinking something like this[You must be registered and logged in to see this image.]

Hi Mark,
Thanks for the info on how it works much appreciated, so I assume that this applies to all exhausts regardless of if the bike has fuel injection or carbies.

Regards
Alan