[raceman]

l`m here at 7000 feet, the highest capital city in the country. Denver is almost 2000 feet lower. So we tune for altitude and run boost as much as possible. Octane requirements go down which is nice but power goes down also due to the thin air. New vehicles require no adjustments at all but older ones need the timing bumped up,sometimes set at 28` max advance on a NA motor. They`re all different of course. l reset the timing on a Kawi triple a few years back and the guy wheelied into a tree leaving the shop,it was that dramatic a power difference. Anyhow does anyone know about timing the carbed Ducati`s? l suspect the fuelies have things sorted and l`m sure they`re set from the factory but what`s the procedure to revealing the ignition system to proceded with this? ln the past l`ve had to machine parts on some engines to allow adjustment and others you can just buy an advancer...ls an advancer available? any help appreciated and l`ll post my findings

 

[620mblack]

um... you should be able to rejet to get the right a/f ratio

advancing the timing? not to sure about that

 

[Mark1305]

Invest in a Haynes Manual to see how the timing pickups are adjusted. You might see some gains, but it may not be worth the risks unless you do some extensive testing to preclude detonation under loads - big twins don't react like higher revving motors.

Another consideration that leads to me to believe it's not worth fooling with is that Ducati carbed bikes don't have very sophisticated ignition controls. The ignition modules basically go from no advance below about 3500 rpm to full advance above that rpm. Since you aren't dealing with an advance curve, you must deal with the advance vs rpm at the range you are most likely to cause detonation by adding advance.

The only direction I've seen tuners go with timing adjustments so far is take out about 2 degrees on really built motors.

 

[Speeddog]

You may regain some of the power by advancing it a bit, but IMO that's just a band-aid.


If you're *only* going to run at high altitude, getting a higher compression ratio is the best approach to getting the cylinder pressure (and that power) back to where it should be.

 

[greenmonster]

ls an advancer available?

DP has tuning ignition modules, 3 different w set curves.

 

[raceman]

You may regain some of the power by advancing it a bit, but IMO that's just a band-aid.


If you're *only* going to run at high altitude, getting a higher compression ratio is the best approach to getting the cylinder pressure (and that power) back to where it should be.

No offense here Speedog but you don`t seem to have spent much time tuning/racing at altitude. First off advancing the timing for better performance is just plain tuning,at sea level or 10K feet,it`s not a band aid at all. At altitude overly high compression has the same detrimental effects as at sea level-pinging,detonation,high temps and super high octane requirements. lt`s not the answer. Tweaking the timing can help a lot and in fact is nessasary for some older vehicles because they will lose sooo much power they`re dangerous to drive. l`ll post my findings but if possible l intend to add more initial timing to start with and proceed from there,perhaps raising the max adavance or lowering the tip in point. With some bikes all this takes is modding the points/pickup plate to allow rotation. Stay _tuned

 

[moperfserv]

The DP modules are pretty much the same as the Pederzini modules, maybe the same thing.
They are for increased compression, therrefore they all have less advance. That won't solve the altitude problem. In fact, a couple of those modules have TDC idle timing which makes an engine run really crappy at idle.
You can advance the timing by moving the piece that the pick-ups mount on. Maybe the Haynes manual covers the gap you need, but a little more than 0.5mm should do.
I retarded a lot of HC engines, but the idle timing is only 6 degrees stock, so the idle deteriorates with a little retard. Advancing the pickups should make it happy everywhere.


Doug

 

[altersys]

At altitude overly high compression has the same detrimental effects as at sea level-pinging,detonation,high temps and super high octane requirements.

huh? didn't you *just say*:

Octane requirements go down which is nice but power goes down also due to the thin air.

octane requirements going down is equivalent to higher stability and resistance to detonation at the same octane rating, under higher compression.

 

[Speeddog]

No offense here Speedog but you don`t seem to have spent much time tuning/racing at altitude. First off advancing the timing for better performance is just plain tuning,at sea level or 10K feet,it`s not a band aid at all. At altitude overly high compression has the same detrimental effects as at sea level-pinging,detonation,high temps and super high octane requirements. lt`s not the answer. Tweaking the timing can help a lot and in fact is nessasary for some older vehicles because they will lose sooo much power they`re dangerous to drive. l`ll post my findings but if possible l intend to add more initial timing to start with and proceed from there,perhaps raising the max adavance or lowering the tip in point. With some bikes all this takes is modding the points/pickup plate to allow rotation. Stay _tuned

Hmmm...well, here's my logic in recommending higher compression.

As far as the engine is concerned, the only effect from higher altitude is lower air pressure (or lower air density, whichever way you want to look at it).
Which is why you need to rejet a carbie motor when it is run at high altitude.

Because the air pressure at BDC is lower, it will be lower at TDC.

My recommendation is to increase the compression ratio, such that you get the pressure at TDC back up to what it is when the bike is at sea level.
Then, you shouldn't have to mess with the timing, as the conditions in the combustion chamber are what they were at sea level.

By increasing the compression ratio, you're fixing the *problem* caused by the high altitude.

I wasn't advocating "overly high compression", merely recommending that you regain what you've lost.

 

[test-reg]

Hmmm...well, here's my logic in recommending higher compression.

As far as the engine is concerned, the only effect from higher altitude is lower air pressure (or lower air density, whichever way you want to look at it).
Which is why you need to rejet a carbie motor when it is run at high altitude.

Because the air pressure at BDC is lower, it will be lower at TDC.

My recommendation is to increase the compression ratio, such that you get the pressure at TDC back up to what it is when the bike is at sea level.
Then, you shouldn't have to mess with the timing, as the conditions in the combustion chamber are what they were at sea level.

By increasing the compression ratio, you're fixing the *problem* caused by the high altitude.

I wasn't advocating "overly high compression", merely recommending that you regain what you've lost.

Definately the best way to go, but there are two downsides:
cost
not easily reversible when the bike leaves high altitude

 

[altersys]

what, you can't poke a leaky hole in the cyl head? [laugh]