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[SPIDERMAN]

If I understand correctly, he is suggesting to get a dyno run on the other dyno now and comparing that with the previous dyno run also done on the other dyno.  In theory it is a good idea.  In practice the previous dyno run was done uncorrected (if I am not mistaken) and therefor can't be compared to anything since the run conditions are unknown.

Unless the runs are done on the same day, on the same dyno, in the same weather conditions, there really is no comparisons that will be accurate and even then arguments can be made for tire pressure, strap tightness and rotating mass.  IMO, the dyno is just a tool for tuning and not a tool for comparing bike to bike.  That should be done on a track side by side.

 Common sense, I thought it had gone out of fashion.

 That does it, I'm moving back to Maine ASAP


B B

[miker]

I always thought decel pop was a factor of reversion when you let off the gas

B B

Yup, scavenged exhaust goes sputter, gurgle, but when mine evolves into a distinct pop I know another exhaust leak is letting that cooler air in.  Its a bitch in a 3 million lb/hr steam boiler when a burner goes out and in, that "decel" pop shakes the chit out of everybody and stains the skivvies!

[Hoist!]

Not comparing the 2 dynos, but comparing the runs on both to see what the numbers are on the Dyno jet for this new tune. I purchased and setup my first dyno in 1993 and quickly learned that dynos are good for nothing more than determining incremental changes in engine performance for that specific engine on that specific dyno. You can never compare the results from diff engines on diff dynos, to many variables. Guys would claim thay got this HP and TQ and bring the engine to a diff dyno and get diff results. The proof is on the track not in the dyno room.

Now, back to my original statement.... it would be interesting to run cybil on the dyno jet that Hoist got his first tune on, that would give us an idea where its at for TQ & HP on a dynojet...since the two dynos use different approaches and many of us only have seen results from the dyno jet brand this would translate the new tune into dynojet results.

VG

That won't happen. And first off, the last tune was from the old engine. I've been running on my old tune with my new motor. Similar build, but not identical. So the map was never right for this engine anyway. But I think I have a run that Vern did before tearing my motor down, and I'm gonna throw it on the same Dyno again just for chits and giggles. So hang in there VG. You might get to see that yet.

Hoist!

[SPIDERMAN]

I've had it from being too lean, too rich, or reversion, over the years on various bikes. Number of reasons it can occur. My '95 Dyna needed smaller intermediate to get rid of it there. But when this bike was too rich, no decel pop on this one at all. So I'm assuming dumping fuel in her will eventually get rid of it. But that would defeat the better gas mileage result I got from the tune.

And then again, maybe not. They tried and couldn't get it out.

Hoist!

As explained to me, decel pop is caused by cooler air running back up the pipe when you let off the gas and the pressure in the pipe changes like air running over a chimney causes a draft. If you've ever had an open fireplace you understand the effect.

B B

[TNThumper]

ok Hoist now your talkin.. nothing more than a run to get numbers which would translate to dynojet result comparison of the current tune.

thank you very much

VG

[springer-]

I always thought decel pop was a factor of reversion when you let off the gas

B B

Decel pop can be caused by several conditions.  There is a lean decel pop and fat decel pop.  A fat decel pop is from excessive un-burned fuel being exhausted on to the hot exhaust valve causing it to ignite in the exhaust system.  This can also be a result of timing being to advanced not allowing the charge enough time to burn before exhausting.

Lean decel pop (more common) is usually a result from not enough fuel to sustain a controlled burn resulting in un-burned fuel being exhausted then ignited.  This can amplified by a free flowing exhaust because you tend to hear it more than a muffled exhaust.

[SPIDERMAN]

Decel pop can be caused by several conditions.  There is a lean decel pop and fat decel pop.  A fat decel pop is from excessive un-burned fuel being exhausted on to the hot exhaust valve causing it to ignite in the exhaust system.  This can also be a result of timing being to advanced not allowing the charge enough time to burn before exhausting.

Lean decel pop (more common) is usually a result from not enough fuel to sustain a controlled burn resulting in un-burned fuel being exhausted then ignited.  This can amplified by a free flowing exhaust because you tend to hear it more than a muffled exhaust.

Hmmmmmm  I'm getting a heck of an education today. The things you describe above I've always referred to as detonation and backfire

I'm headed home soon to visit my poor old Mom, I'm gonna look you Boyz up.

Do any of you fly a patch ?  If so PM me  (only good I assure you)


B B

[porthole]

detonation  -pre-ignition - two flame fronts colliding on the compression stroke.

Decel pop is only when the exhaust valve opens, no?

[Hoist!]

Here's two charts. First one is the dyno sweep at 20%, 40%, 60% and 100% throttle I believe. Actual measured torque, not calculated. Way different from what we're used to seeing on the dyno. But believe me, the bike runs better. Shows ya what all these different dynos/tuners do to real numbers.

Hoist!

[Hoist!]

This one is a WOT comparison of my bike vs. an '08 SEUC, Stage I, tuned the day before the same way as mine. Note how the stock drops off at 3600, and the HP dies. See the fairly sraight line TQ of mine and how the HP justs keeps climbing with the RPM's. That's why she pulls like a mutha!

[springer-]

Detonation or spark knock is erratic combustion. Detonation happens when excessive heat and/or pressure causes the charge to ignite. This can cause multiple flame fronts in the combustion process instead of a single flame kernel. When these flames fronts collide, the violent reaction produces a sharp increase in cylinder pressure.  This is often heard as pinging or knocking. The force is so violent it can damage head gaskets, pistons, rings, and even rod bearings.

This occurs in all engine but continued and prolonged detonation can cause serious damage.

Pre-Ignition is typically caused by a hot spot during the combustion process, before the spark plug fires the cylinder.  It can be caused by excessively hot Carbon deposits, overheated spark plugs (too hot of a heat range) or hot sharp edges on a spark plug, piston or in the combustion chamber.

Too lean AF condition can promote hot spots.

[Hoist!]

Here's a few pics of the other day.

This is ouside the dyno shop. That's the SEUC he tuned the day before with Cybil.

[Hoist!]

That's Bean's Buell back there.

[Hoist!]

Entrance to the Dyno.

[Hoist!]

The built-in Factory Pro Dyno!