Power Flat Spots

[dlaing]

Of course, it's easy to suggest the solution: putting it into practice is a little more involved...

Yeah, that is why I suggest a crossover as CURE for the flat spot.

The Quat-D and Mistral were compromises, but the Stucchi and FBF had gains just about everywhere.

[Ryland3210]

I am tempted to do an experiment without having to shell out big bucks. There is a plethora of economical aftermarket mufflers and pipes available for Harleys. I'd like to hear an opinion from you guys with more experience than me by far in exhaust modifications, on what might be expected (in 50 words or less, if possible) from the following:

 

Rip off the entire exhaust system, leaving only the exhaust pipe directly connected to the engine, then attach dual exhaust pipes and aftermarket Harley straight through mufflers (not just straight pipes, but with some sound absorption). I think they might look great and sound great, and save weight as well.

 

My local Harley dealer has a dyno setup, but says its a problem getting a good f/a signal with the stock mufflers. The Harley mufflers would make it possible to tune the map easily.

 

Thanks in advance,

John

[docc]

No crossover?

[Skeeve]

Rip off the entire exhaust system, leaving only the exhaust pipe directly connected to the engine, then attach dual exhaust pipes and aftermarket Harley straight through mufflers (not just straight pipes, but with some sound absorption). I think they might look great and sound great, and save weight as well.

 

The go-fast boys in hotrods & dragster & the moonshine-runners [the nascent beginnings of NASCAR: why do you think the cars have to *look* stock?] figured out half a century ago that individual pipes work great for airplanes, where the engine is turning mostly at a set rpm well below redline for long periods of time, but that for serious power, using the exhaust pulse from one cylinder to help evacuate another by using a properly designed 2->1 [or in the case of V8s, 2x 4->2->1] header works better.

 

IIRC, the V7 used individual exhausts. Tonti & Todero added x-overs to their specials that they used to set speed records w/, & they've been on Guzzis ever since! As far as x-overs go, I have to say the one from the V7 Sport or V750S are probably the best looking models; no idea about performance, but they sure look the part!

 

And for any twin w/ a firing interval of less than 180 degrees, being able to share muffler volume is going to be an important factor in performance. So getting away w/ individual pea-shooter muffs might work o.k. on a BMW or Triumph, but on Harleys & Guzzis? Just more noise w/ less performance...

[Ryland3210]

No crossover?

 

Right, the idea is keep it simple.

[Ryland3210]

The go-fast boys in hotrods & dragster & the moonshine-runners [the nascent beginnings of NASCAR: why do you think the cars have to *look* stock?] figured out half a century ago that individual pipes work great for airplanes, where the engine is turning mostly at a set rpm well below redline for long periods of time, but that for serious power, using the exhaust pulse from one cylinder to help evacuate another by using a properly designed 2->1 [or in the case of V8s, 2x 4->2->1] header works better.

 

IIRC, the V7 used individual exhausts. Tonti & Todero added x-overs to their specials that they used to set speed records w/, & they've been on Guzzis ever since! As far as x-overs go, I have to say the one from the V7 Sport or V750S are probably the best looking models; no idea about performance, but they sure look the part!

 

And for any twin w/ a firing interval of less than 180 degrees, being able to share muffler volume is going to be an important factor in performance. So getting away w/ individual pea-shooter muffs might work o.k. on a BMW or Triumph, but on Harleys & Guzzis? Just more noise w/ less performance...

 

I understand the advantages of creating a scavenging effect from the kind of header you describe. What I don't get is the less than 180 degree firing interval comment. Firstly, I thought the Guzzi con rods shared the crankpin. If so, the shorter of the two firing angles is 270 degrees, no?

Secondly, sharing muffler volume if firing is unsymmetrical seems to me to create inequalities in backpressure and/or scavenging between the cylinders, so keeping the exhaust systems isolated avoids that interaction, no?

[dlaing]

I understand the advantages of creating a scavenging effect from the kind of header you describe. What I don't get is the less than 180 degree firing interval comment. Firstly, I thought the Guzzi con rods shared the crankpin. If so, the shorter of the two firing angles is 270 degrees, no?

I don't understand that either.

I thought the Boxer twins would benefit even more from a 2 into 1 because of the symmetry.

Secondly, sharing muffler volume if firing is unsymmetrical seems to me to create inequalities in backpressure and/or scavenging between the cylinders, so keeping the exhaust systems isolated avoids that interaction, no?

That is what I believe.

Yes, you have to weigh the benefits of shared muffler for scavenging versus the benefits of clean even back-pressure.

Keep in mind the stock ECU is mapped for the stock mufflers and crossover.

Throw a Stucchi on and some more open mufflers and all that hard work plotting the map cells by the factory engineers has gone out the window.

I have yet to see someone post a really extensive mapping that truly got the most out of the modifications.

Also, keep in mind that without a crossover, you will lose power somewhere...

With Guzzi stock muffers and no crossover, expect big gains in the middle and bigger losses at higher RPM.

I suspect if you put on the free-est flowing mufflers you can find, the high RPMs benefit while the low-end will drop miserably.

But find the right compromise and re-tune the ECU and you have one of the smoothest running Guzzis around.

Just don't expect to win races against the bikes with Stucchi Crossovers and Mistral Mufflers, that have already been proven to make power.

[Ryland3210]

I don't understand that either.

I thought the Boxer twins would benefit even more from a 2 into 1 because of the symmetry.

 

That is what I believe.

Yes, you have to weigh the benefits of shared muffler for scavenging versus the benefits of clean even back-pressure.

Keep in mind the stock ECU is mapped for the stock mufflers and crossover.

Throw a Stucchi on and some more open mufflers and all that hard work plotting the map cells by the factory engineers has gone out the window.

I have yet to see someone post a really extensive mapping that truly got the most out of the modifications.

Also, keep in mind that without a crossover, you will lose power somewhere...

With Guzzi stock muffers and no crossover, expect big gains in the middle and bigger losses at higher RPM.

I suspect if you put on the free-est flowing mufflers you can find, the high RPMs benefit while the low-end will drop miserably.

But find the right compromise and re-tune the ECU and you have one of the smoothest running Guzzis around.

Just don't expect to win races against the bikes with Stucchi Crossovers and Mistral Mufflers, that have already been proven to make power.

 

Does the ECU provide independent fuel maps for each cylinder? If not, clean even back pressure would be more important.

 

Personally, I'm probably the exception, but I like the big gains in the middle at the price of losses at higher RPM's within reason, if that's the price to be paid for even back pressure, on the theory that the simpler no-crossover system will improve economy and sound great. Also, given where I live, midrange acceleration is desireable, to be able to pass slower vehicles on single lane twisty roads as quickly as possible. That normally means dropping down to the approprate gear to catapult me around the slower vehicle without shifting.

 

As far as losing the benefit of factory tuning, I'm sure it's close to perfection, but am troubled by the anomalies I see in the fuel and timing maps. The F/A graphs showing extreme lean conditions and wide variations in ratio, and the timing chart dip at part throttle make me doubtful. I look at the challenge of spending the money and investing the time into working with a dyno to optimize both as a fun project, and I'd be glad to report the results. I only wish there was a way to adapt a lambda sensor to use while riding. That way, I could quickly go through the trial and error procedure without having to resort to the dyno.

[dlaing]

Does the ECU provide independent fuel maps for each cylinder? If not, clean even back pressure would be more important.

 

Personally, I'm probably the exception, but I like the big gains in the middle at the price of losses at higher RPM's within reason, if that's the price to be paid for even back pressure, on the theory that the simpler no-crossover system will improve economy and sound great. Also, given where I live, midrange acceleration is desireable, to be able to pass slower vehicles on single lane twisty roads as quickly as possible. That normally means dropping down to the approprate gear to catapult me around the slower vehicle without shifting.

 

As far as losing the benefit of factory tuning, I'm sure it's close to perfection, but am troubled by the anomalies I see in the fuel and timing maps. The F/A graphs showing extreme lean conditions and wide variations in ratio, and the timing chart dip at part throttle make me doubtful. I look at the challenge of spending the money and investing the time into working with a dyno to optimize both as a fun project, and I'd be glad to report the results. I only wish there was a way to adapt a lambda sensor to use while riding. That way, I could quickly go through the trial and error procedure without having to resort to the dyno.

For $205US

http://www.guzzitech.com/store/TR-DirectLink.html DirectLink can modify fuel maps for each cylinder.

I think Tuneboy can, but the map labels have me a little confused.

PCIII USB can do individual cylinder tuning, but not timing.

For a few more hundred dollars you can get a wide band Oxygen sensor, preferably with data logging so that you can use while riding.

An exhaust gas temperature meter can also be useful.

I think the further you go from stock with modifications, the more you will benefit from these tools. Motoguzzinix's posts show that there is room for improvement for just about any V11. Going with separate exhausts will really change the mapping needs.

You might also consider pod filters to keep the cylinders even safer from cross-interference.

[Pierre]

The stock map from my ECU as interpreted by my Tune Boy software

I graphed the 84.56% throttle data across all the RPMs.

I spaced the spread sheet entries so that curve would show.

It is not perfectly accurate in the spacing of the bars for some reason <_>

But the curve gives a pretty good indication.

Tuneboy has 3D graphing capability, maybe I will post.

I need a new usb memory stick so I can shuttle between garage PC and internet connected Mac.

The upper row of the upper map in this image is what was graphed

David, does your Tune Boy work with the newer twin plug Guzzi's? I've been trying to find the factory map for their twin plug version but those maps are apparently unobtanium, so now thinking that your Tune Boy plugged into a newer twin plug Guzzi would reveal the factory advance curve. What do you think?

[dlaing]

David, does your Tune Boy work with the newer twin plug Guzzi's? I've been trying to find the factory map for their twin plug version but those maps are apparently unobtanium, so now thinking that your Tune Boy plugged into a newer twin plug Guzzi would reveal the factory advance curve. What do you think?

Hi Pierre,

I am almost certain the TuneBoy won't communicate with the Breva, Griso, Norge, etc.

Those bikes use a Magneti Marelli IAW 5 AM2 or something like that...maybe it is a 5AM?

I would not be surprised if TechnoResearch soon comes out with a Direct Link software to use with the Newer bike's ECUs.

It appears as if their diagnostic software may work with it, but Guzzitech does not list it.

But it is listed here

http://technoresearch.online.fr/Motorcycle-List.htm

The diagnostic won't show the mapping, only the direct link.

Not sure about AxeOne, but I doubt it will show the mapping.

[Guzzi2Go]

....Going with separate exhausts will really change the mapping needs.

You might also consider pod filters to keep the cylinders even safer from cross-interference.

 

I read somewhere that a motor with split inlet and exhaust tracts is considered as two engines sharing the same crankshaft. Balancing the two seems to be an issue and extremely sensitive to external conditions. Apparently already a slight crosswind leads to difference in balance on the lee- and windward side.

[Ryland3210]

I read somewhere that a motor with split inlet and exhaust tracts is considered as two engines sharing the same crankshaft. Balancing the two seems to be an issue and extremely sensitive to external conditions. Apparently already a slight crosswind leads to difference in balance on the lee- and windward side.

 

I believe that balancing is very important for power and economy. For example, my Norton Commando's two AMAL carbs had throttle cables I could reach while riding. At cruise speeds (z.B. 100 kph) if I reached down and pulled one cable to open one carb throttle while holding the handlebar throttle still, it would make almost no difference in power and speed would only increase a little. That was not expected at all.

 

This is one reason why I am very interested if the ECU mapping for each cylinder is separate. Even if one balances the vacuums perfectly, there is still the question of fuel delivery, especially with the V11 engine's asymmetrical firing order.

[dlaing]

I read somewhere that a motor with split inlet and exhaust tracts is considered as two engines sharing the same crankshaft. Balancing the two seems to be an issue and extremely sensitive to external conditions. Apparently already a slight crosswind leads to difference in balance on the lee- and windward side.

That presents a good argument for sticking with the stock airbox and using a crossover.

I suppose you could have shields to deflect the wind and balance tubes to even the airpressure by the pods. But that would be a pain to implement so that it worked well.

[motoguzznix]

IIRC, the V7 used individual exhausts. Tonti & Todero added x-overs to their specials that they used to set speed records w/, & they've been on Guzzis ever since! As far as x-overs go, I have to say the one from the V7 Sport or V750S are probably the best looking models; no idea about performance, but they sure look the part!

Concerning the X-over of the V7Sport, I can make a comment as I own one:

There are two separate crossover pipes that protrude into the exhaust pipes and so reduce the freeflowing area of the pipes. This is a worst case situation for the exhaust föow and causes power losses all over the rpm range. When I removed the protruding parts of the crossover pipes, power made a substantial step upwards. Not backed by Dyno measuremants, only by feel. But the crossover then is more of a conventional Xover like on any LM 123.

 

With Guzzi stock muffers and no crossover, expect big gains in the middle and bigger losses at higher RPM.

I suspect if you put on the free-est flowing mufflers you can find, the high RPMs benefit while the low-end will drop miserably.

David

 

I would be careful with these predictions.You might be far from the truth and on the Dyno there might be a lot to learn in that area.

For any 4stroke engine, backpressure is bad for power. Of big influence is the tuning length of the exhaust pipe. This has to be taken into account for comparisons.

 

Does the ECU provide independent fuel maps for each cylinder? If not, clean even back pressure would be more important.

 

As far as losing the benefit of factory tuning, I'm sure it's close to perfection, but am troubled by the anomalies I see in the fuel and timing maps. The F/A graphs showing extreme lean conditions and wide variations in ratio, and the timing chart dip at part throttle make me doubtful. I look at the challenge of spending the money and investing the time into working with a dyno to optimize both as a fun project, and I'd be glad to report the results. I only wish there was a way to adapt a lambda sensor to use while riding. That way, I could quickly go through the trial and error procedure without having to resort to the dyno.

The fuel can be mapped independently for each cylinder, the ignition timing not. For the fuel, there is a base map for both cylinders and an offset map for the right one.

 

Wideband lambda controllers are available by several sources, I use the Dynojet wideband controller. Works well with good results, my posted lambda measurements are made by using it.