ESE's works engine tuner

[RomeuPT]

Hello Everyone.

I kind a ask my self sometimes, why some bikes use a steel exhaust flange and then use springs to hold the pipe, I understand that in some models the flange might need to be centered or something, that a aluminium flange may help cool the end gases and give some increase in performance, that it might even get's easier to change the exhaust just taking off springs, to do oval to round transitions, alow pipes to be simplier and rotate a bit to fit better or something etc etc.

But for example Aprilia RS have a steel flange, a round exit exhaust duct, no step between the exit and flange entrance, no need to center the flange, has much has I know rear fitting is the same and is ajustable, some complain about leaks in the flange connection with pipe, the standard exhaust springs are not very acessible and hard to take off, same to bolt on the flange, and my guess is it would be possible to bolt a pipe without much more effort than the flange alone with common tools. Why is this not done?

[husaberg]

Hello Everyone.

I kind a ask my self sometimes, why some bikes use a steel exhaust flange and then use springs to hold the pipe, I understand that in some models the flange might need to be centered or something, that a aluminium flange may help cool the end gases and give some increase in performance, that it might even get's easier to change the exhaust just taking off springs, to do oval to round transitions, alow pipes to be simplier and rotate a bit to fit better or something etc etc.

But for example Aprilia RS have a steel flange, a round exit exhaust duct, no step between the exit and flange entrance, no need to center the flange, has much has I know rear fitting is the same and is ajustable, some complain about leaks in the flange connection with pipe, the standard exhaust springs are not very acessible and hard to take off, same to bolt on the flange, and my guess is it would be possible to bolt a pipe without much more effort than the flange alone with common tools. Why is this not done?

Flexibility and vibration plus ease of removal

[Frits Overmars]

I can still do that, and I don't get the amount of help from gravity that she does.

[Dutch Fisher]

Thats reminds me,, i must go out and milk the cows

[seattle smitty]

Holy cow, H-berg, I watched for quite a while hoping she'd have a wardrobe malfunction . . . well, that's inspiration for another day of labor.

[ken seeber]

Holy cow, H-berg, I watched for quite a while hoping she'd have a wardrobe malfunction . . . well, that's inspiration for another day of labor.

Smitty, dunno how virile you are, but would that be "hard" labour?

[husaberg]

I can still do that, and I don't get the amount of help from gravity that she does.

Thats reminds me,, i must go out and milk the cows

Holy cow, H-berg, I watched for quite a while hoping she'd have a wardrobe malfunction . . . well, that's inspiration for another day of labor.

Well it was the best way I felt I could convey the need for both vibration control and the importance of flexible of mounting.
The best slip joint flanges I have seen include O rings. I are surmising one of the correspondents will have pics of the Aprilia or Super Kart set ups.
http://www.kiwibiker.co.nz/forums/at...5&d=1413013578
http://www.kiwibiker.co.nz/forums/at...6&d=1413013580
http://www.kiwibiker.co.nz/forums/at...8&d=1413013584
http://www.kiwibiker.co.nz/forums/at...7&d=1413013582
http://www.kiwibiker.co.nz/forums/at...3&d=1302726963
Combination of both MR WOB
http://www.kiwibiker.co.nz/forums/at...2&d=1412478918
http://www.kiwibiker.co.nz/forums/sh...post1129955411

[Frits Overmars]

The best slip joint flanges I have seen...

Let's not go there, Husa. We must think about our young readers. And spare the hearts of the old-timers.

[chrisc]

Let's not go there, Husa. We must think about our young readers. And spare the hearts of the old-timers.

"Practice safe 2 stroking, always use a slip joint"

[seattle smitty]

What was it the dirt riders' wives used to say . . . "An enduro rider is just dirty boots at one end, and a dirty mind at the other."

Thanks for the pipe photos, H-berg; somebody is doing some gorgeous work.

[seattle smitty]

There must be some general principles on the gapping of spark plugs that I'm missing. One of my interests is in improving the fuel efficiency of my daily driver, work truck, camper-van, road bike, etc.. According to years of reading articles for laymen, improvements to Kettering battery-and-points ignitions got the desirable gap for factory automobiles up (bigger) to about .035" (let's see, about 0.9mm). The advent of inductive and CD electronic ignitions allowed gaps as big as .060" (1.5mm) to light off relatively lean mixtures.

So I got to thinking that it is desirable to have the biggest gap, short of misfire, that your ignition could handle. But these days I hear that the newest alcohol-burning outboards, with the best ignitions they can find, want very small gaps, down to .011 or .012" (0.3mm). So what is the deal here, for racing engines? Do you want the biggest plug gap that the engine/ignition combination will take without increasing misfire (or overheating the ignition), or are there other considerations?

[wobbly]

The amount of energy available to be used in the spark process sets the gap that can be used.
Other elements that come into play are the plug efficiency ( an arbitrary term to denote the use of rare earth metals for the centre and earth electrodes )
and the mixture to be ignited ( rich and lean are harder to fire ).
When the ignition system initiates the gap ionisation this uses a set % of the energy available, and the wider the gap the greater the energy required to
establish a spark.
The remaining energy is used to create the "burn" phase that establishes a growing flame kernel.
So having a wide gap may use up too much of the available Joules, and the burn phase ends up not creating a sufficiently large kernel to have this spread thru
the chamber and consume all the combustible mixture ie a misfire.
Firing rich Alcohol mixtures is one scenario that needs alot of available energy, and if this isnt the case then close gaps can as a band-aid ameliorate the lack of power
to both ionise the gap and then create the kernel.
To do this well you have to resort to using a CDI system like the Ignitech, and fire both channels into a single coil that has a large inductive reactance.
The combination of plenty of energy storage in the twin capacitors and plenty of inductance to increase the burn period allow super rich highly compressed mixtures to be
burned with no combustion events dropping out.

[peewee]

i was told by a few people on other forums to decrease the spark gap for my alcohol engine. i tried .018" and .024" (which is what they are out of the box), i never could tell any difference with seat of the pants. maybe a dyno would of picked up the minor differences but i couldnt tell so i just used the standard gap from the box. maybe on another engine with less powerful ign it would of been more noticable

[seattle smitty]

Once the arc is established, doesn't the resistance to current flow drop dramatically? Of course, if you have to establish the arc with a CD system's short duration discharge, I guess the arc wouldn't stay established for long in any case . . . .

[speedpro]

I built a battery powered, points triggered, CDI for my old AC50. I went from about a .3mm gap, even with a big coil as that was all the gap it would spark over, to 1mm. In the lab the CDI would fire over a 10mm gap with a vicious bright blue spark. Using a pulse generator to trigger it we ran it up to equivalent of a V8 doing 10,000rpm without losing any output. The charging pulses looked like a picket fence on the scope and the inverter was drawing about 10A from the supply. We doubled up the capacitors from the original design and upped the inverter/rectifier output to 400V. It was definitely something you kept fingers off if it was powered up.

Never had a problem with misfiring. Back in the good old days.