Bob, I have great great respect for the observations of the great tuners around the country. Some of then have been doing this stuff with carbs,points and smelling the plugs. Others do it with EGTs and MAF meters and microprocessors. They all have observations that have patterns. It's the patterns the the programmers are looking for. They can build in feed back systems in to the code to deal with the "bumps" Think about what Ion sensing and it's ability to detect the pressure in the combustion chamber every degree of the 720 degrees of crank rotation. O2 sensors smelling for the existance of 02 in 1300 degree F exhaust.

If you really want to have fun some day mount a pair of narrow bands 6" from the exhaust gasket. Now mounta narrow bandat the collector. Last mount a wideband 12" up the exhaust pipe. Put the motor on the dyno and watch all the gauges with the motor in closed loop where all the o2 sensors should be dead on and getting the same answer. Watch the PW of the two injectors. What you will most likely find out is all these things that you thought were gospel are all giving different answeres. The PW will be swinging just a little. This all gets very interesting. Lots of these dips can often be traced back to the tools. There is lots of delay in a wide band with changing exhaust temp that lots of tuners have no idea that is happening.

Megasquirt has tought me that a motor is a very predictable thing, given that you have the time to find the patterns. Four stroke motors (assuming you are not talking Mazda) are all very similar. Shure you get the big v8s with big huge open intakes and the 8000 RPM Honda street motor and the 14000 RPM GSXR motors bit thay all have their similarities.

Harleys havetwo rather unique properties. The wobble fire crank with a shared Y intake and therear cylinder gets less cooling air. It's still an air pump with a controled explosion in the middle of the pump. We have total control of the PW (fuel going in), MAP (air going in), Ion sensing to detect the correct timing (pressure in the middle), at least narrow band (air going out) anddata Logging (a way to record all this every 1/10 th of a sec or so. Not bad for "Tuning Neanderthals" You guys have come a long way. Your tool have come a long way from the old days of points, jetsand smelling plugs.

Nowwe just need the tools to read the data.

AW

 

Just curious, why would you shut down the fuel during extended deceleration?

With only two cylinders, having a combustable mixture available in the chamber, at any momment and without hesitation, seems more prudent. For that reason, and the reasons of cooling and additional lubricity to the combustion chamber components, shutting down the fuel supply seems rather... I can't think of any word that wouldn't come off assounding harsh. How about, illogical.

 

Illogical is perfect. The logic is not apparent Google Chrysler's Multi-Displacement System They do it for gas milage and may also do a total shut down of fuel in over-run. Honda on thair street cars (at least on the manual transmission) does it all the time. You can feel it if you know what you are looking for.

The logic is

1) If the throttle is fully closed

And

2) If the MAP (average) is lower than what it is atidle

And

3) The motor is up to operating temp

And

4)All ofthese conditions are all met for some period of time of say 1.5 seconds

Then totally remove ALL fuel until you...

a) get below say 1250 RPM (near but still slightly above idle)

Or

b) you open the throttle even a little

The air that the motor will continue to pump will be way cooler than any air fuel mixture if it is ignited, no matter when in the crank rotation this happens. Burning fuel at any time makes heat. I can get into the acceleration enrichment requirementsif you want, but for now...

Hope this helps

AW

 

No, none of that helps as while cars and bikes share one thing, they both have an ICC engine providing locomotion, the comparrison stops there.

Cars typically have from four to ten cylinders (older Saabs had three and so does the Wankel), are liquidcooled, and have the EPA and a 'green, tree hugging' customer base to address and pacify - never saw an EPAcity/highway mileage/cost estimateto operate sticker on any of my new Harleys.

As I read many of these posts/threads, I'm trying to not let any other logic or theory of operation knowledge cross contaminate discussions based on H-D V-twin technology.

But thanks for the info.

 

The Delphi ECM does shut off the injectors at low manifold pressure and zero throttle position.

 

That is a sad statement.... I can not think of an apporpiate response.

AW

 

Sad? Perhaps, but I'm OK with it.

Thank you for answering my inquiry about cutting fuel. I found it interesting.

As this is a technical forum and you started the thread with what would appear to be some in-accurate or flat-out wrongobservations and comments, the others here would rather not read the musings of another Dr. Phil wannabee on my state of mind.

Now, how about jumping back on thread addressing your 180 degree flip-flops and numerous other errors in thought and understandingthe processes employed in the design and operationof these particularly distinct and amazing motors.

 

In these two SERT maps there is a huge differance in the upper left section of the map. I am just asking what could possibly justify such a differance? Is this to make more noise as a bling thing? A way to keep the o2s up to temp by having flame in the exhaust? If so why on one tune and not the other?

In that bottom right corner of the map the timing goes all the way to 0 degrees. How is it possible that 0 degrees is the correct answer? Fuel takes time to burn. I could understand 10 or so but 0? Are they trying to soften the wobble fire motor pulsations by killing the torque?



Just asking questions

AW

 

In my opinion, it has to be torque management for warranty and longevitypurposes. The tuner does not want someone in a higher gear at around 1000 RPM cracking the throttle opento very low kpas bogging the engine,which is very hard on the bottom ends.

 

OK That is a reasonable explanation for the bottom right corner but what about the top left corner. A fairly small percentage of the "standard" Harley SERT maps do this, but why? Most motors run in the 30-40 degree range and not 10 degrees. In the big picture of NA IC engines these things are not that unique from one version Harley to the next (excluding the V-Rod) as 45 degree wobble fire, shared Y intake with inadiquate cooling (evenworse onthe rear cylinder) and with cranks and valves that limit the RPM to about 6500 or so.

This map with the low timing in over-run is I bet the most commonly downloaded map (as a stage 1 map) in most of the Sportsters.

Still asking questions....

AW