Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > DYNOS and Engine fuelling

[DEMON]

you'll like this one shazam !

Dynos are very useful tools in the automotive industry..so lets have a little lesson on em eh ?

1. what do dynos do ? i can tell you they dont measure the power of a bike /car ? So I hear you say eh ?

2. When a graph of torque and power are plotted on the same graph, they will cross at exactly the same point no matter which bike you stick on the dyno...why ?
If you and a mate have had dyno runs on the same dyno, or different ones, take a look at your graphs and see !

3. How do power commander work ?

4. Why do engines that run extremely lean burn out their components ? why doesnt this happen with a mixture which gets really rich....surely more fuel = more heat ?

Ducati performance chips tend to make the dukes run extremely lean...but on which cylinder ?

5. Why fuel the two cylinders differently then ?

6. Which 4 stroke cycle does your bike use ?

7. stoichiometric air...what is it ?

[rockhopper]

2. 5250 revs isn't it? Can't remember why this is though!
4. The incoming fuel/air mixture actually cools the engine, not enough fuel, not enough cooling, engine gets hotter.
5. I think the Ducati FI systems (the earlier ones anyhow) map both cylinders the same even though the system is capable of mapping them differently.
6. Otto cycle
7. Something to do with the perfect ratio of fuel to air to make the fuel burn. 14.7 : 1 rings a bell.

[twpd]

Dynos are very useful tools in the automotive industry..so lets have a little lesson on em eh ?

1. what do dynos do ? i can tell you they dont measure the power of a bike /car ? So I hear you say eh ?

Torque. Or turning force.

2. When a graph of torque and power are plotted on the same graph, they will cross at exactly the same point no matter which bike you stick on the dyno...why ?
If you and a mate have had dyno runs on the same dyno, or different ones, take a look at your graphs and see !

5252 rpm. It's a physical constant from which power is derived as a function of engine speed and torque. I can't remember the equation for it right now though.

3. How do power commander work ?

They apply an offset to the existing component that drives the injectors. The offset is derived from the throttle position which, is calibrated during set up and other factors such as engine speed and the "map" used by the PC.

4. Why do engines that run extremely lean burn out their components ? why doesnt this happen with a mixture which gets really rich....surely more fuel = more heat ?

More fuel makes an engine run cooler.

Ducati performance chips tend to make the dukes run extremely lean...but on which cylinder ?

Not sure with that one - I don't play with DP chips.

5. Why fuel the two cylinders differently then ?

Rear ones tend to run hotter as they get less air flow. You might want to run it richer to help cool it?

6. Which 4 stroke cycle does your bike use ?

Errr.... is that a trick question? No quite sure what you mean.

7. stoichiometric air...what is it ?

About 14.5:1 IIRC. That is 14.5lbs of air to 1lb of fuel.

[twpd]

Otto. Of course! Doh!

[Felix]

There are dynos and there are dynos. The good old inertial dyno indeed only measures torque and calculates power by multiplying torque and RPM. Inertial dynos cannot operate at steady state, i.e. hold a constant RPM, they can only do run-ups. Other dynos that have a "brake", e.g. an eddy current dyno can actually measure power directly. These more advanced dynos allow to tune an engine for constant throttle to WOT transitions. I think the latest Dynojet dynos are now of this type as well. Most operators though still use the old run-up method only.

Yes, Power Commanders "intercept" the injector pulse and slightly lengthen or shorten it depending on how you program it. If you run your PC with a "zero" map, it leaves the original injector timing unchanged.

Are you sure that DP chips make engines run lean? I was under the impression it's more the opposite. Most DP chips produce sooty exhaust pipes. Ducati are very lean from standard to pass the emissions regs.