Effect of overdriving the injectors?

[-SeabrookTrickBagger]

Has anyone tried to overdrive their injectors?  If so, did the bike perform better or worse?

TIA.

Seabrook

[Herko]

Seabrook.
Similar subject but question was maybe more of an "underdriving" question.

From old HTT. May help.
http://www.msnusers.com/harleytechtalk/afrzone.msnw?action=get_message&ID_Message=1285568&ShowDelete=0&CDir=-2

[uglyDougly]

  What do you mean by 'overdriving'?

  Doug

[waskier01]

I have an '01 113" 125hp softail that has been running for 4-5 years with a 4.5 pressure regulator (60psi) with the stock injectors.

[-SeabrookTrickBagger]

  What do you mean by 'overdriving'?

  Doug

Good question.  Tell the ECU the installed 6.1 gps injectors are 5.7 gps injectors.  That is the idea.

[-SeabrookTrickBagger]

I have an '01 113" 125hp softail that has been running for 4-5 years with a 4.5 pressure regulator (60psi) with the stock injectors.

Interesting.  Have not thought about that one.  Have you ever had stock injectors flowed at that fuel higher pressure to see if you get any, and if so how much, increase in flow?

[ViennaHog]

Wouldn't that simply increase the AFR across the board due to the 7 % increase in fuel addition? Some HD dealers around here do that and call that tuning and charge you big bucks for that.

[Herko]

" Tell the ECU the installed 6.1 gps injectors are 5.7 gps injectors.  That is the idea."

Fairly common when we run out of VE headroom (Vic's word) during the calibration phase of a tune.
Hard to imagine though that 6.1 flow rated injectors need a time boost unless your up around 170 HP or so.

"I have an '01 113" 125hp softail that has been running for 4-5 years with a 4.5 pressure regulator (60psi) with the stock injectors."

Higher pressure...another way to skin the "need more fuel" cat. Low 40's psi is stock for MM IIRC??

[uglyDougly]

  Overdriving isn't really the right term for changing the injector size at the ECM Constants.

  There may be some who disagree on this but I think the cells in the VE tables refer to another table (that we don't get to see) which calls out an air volume for each throttle angle or maybe even each cell of the table.
  The 0-to-127.5 (in .5 increments) is actually hexidecimal 0-to-FF or the hexidecimal 100%.
  The values in the VE tables are not injector pulse width like the M-M uses. (Those pulse widths of the M-M system are corrected for air pressure and temperature change but they are 0-FF of 24mS or 25mS.)
  The reason for the change is so the Delphi system can have higher resolution at the light load end of the map in order to be able to meet more stringent emissions regs.

  That difference in strategy is the reason, with the Delphi, you get VE tables that are maxed out at 20% or 40% throttle, not that the engine is actually using more air. If it trapped or processed more air at part throttle the torque would be higher at part throttle.

  What I mean is; if the idle fuel table of an M-M system uses a value of 20 out of 256, then the change of 1 increment is 5%.
  If the Delphi VE table refers to an air volume (per engine cycle) of 10 Cubic Inches (just throwing out some number here) and the idle air is 75/256 ths of that, then 1 increment is 1.333%.

 
  The Delphi strategy looks at the air volume for the cell of the VE table that you are in for this engine cycle, looks up the air volume, corrects it by inlet temp and parometric pressure, looks at the MAP and goes to the AFR table and looks up the required AFR for that MAP and RPM check the injector size and then calculates the pulse width and grounds that injector at the correct crank angle for the correct amount of time.

  The M-M IAW ECU can't do that kind of calculation whereas the Delphi can.

  I really haven't gotten off point.
  The reference tables that the MoCo uses don't have enough air volume values to satisfy a lot of the 'built' engines we tune. Then we reach the 127.5 in the VE table and it's still lean.

  We could find out what MAP that throttle angle and RPM will generate and insert a richer valu in the AFR table, but that would do the same to the other cylinder.
  The first version of the SERT didn't increase the injector time when you changed the engine size, but subsequent versions apparently do. Because I found that out on the first version I've been telling folks to change the injector size ever since.
  Since it uses the injector size in the pulse width calculation, decreasing the injector size will cause the calculated result to be; longer pulse width.

  A couple years ago there was a discussion on the HTT about just this subject and one of the respondents was offended by the suggestion that we lie to the system.

  If we had access to the air volume charts we wouldn't need to lie to the ECU.
  We would be able to create cals that better fit larger throttle bodies as well.

   Then again, I could be completely wrong.

   Doug

[-SeabrookTrickBagger]

Fibbing to the DTT TCFI in the parameters to tell it the injectors were a bit smaller than those actually installed seemed to have a beneficial effect on my engine.  I suspected the pulse duration would be increased, but WTFDIK.  The engine got quite a bit smoother from idle on up.  I was a bit surprised.  Just wondering what the gurus thought ..........

As far as increasing pressure behind an orifice which flows liquids, well, considered shade tree expert opinion from the local "house of knowledge" is that if the orifice is flowing at maximum output to begin with, the additional pressure will not increase volume output.  But, to borrow a phrase and add a word, "I could be wrong --- again."

[-SeabrookTrickBagger]

That said I can't imagine any HD engine used for the street needing huge injectors like 6.1.
HTH, Bob

That might depend on whether 6.1 gps was arrived at HD fuel pressure or 3 bar.  At 3 bar, 6.1 gps flowed at HD fuel pressure  would be about 5.7 grams per second.  Just wonderin......

[waskier01]

The 4.5bar pressure regulator increased fuel because I was worried about the duty cycle, also gave me the added benefit of increased atomization for better fuel mileage in cruise mode. My '01 softail is Delphi.

[waskier01]

Don't all of the PCIII and such systems lie to the ECM.

[uglyDougly]

  SeabrookTrickBagger wondered about an orifice flattening out at some critical pressure. The ports of our engines will max out at the speed of sound. (air is a fluid) but the MotoGP bikes use more than 10Bar fuel pressure, so I don't think going from 4 to 4.5 Bar s enough to get the response curve to flatten out.
  Ducati Superbikes used to use 5 Bar regularly but I would guess they use higher than that now.

  Bob's right on with all of his responses.

  I'd like to add one thing about Power Commanders and their present strategy.

  The PCIII counts RPM from the number of injector cycles (X 2) and TP from the TPS output. Then it alters the pulse width according to the values you put into the table.
  The only problem with that strategy is that every time the injector ground is made there is a 'dead time' while the field builds up around the actuator (solenoid) and when it moves.
  In my earlier explanation I forgot to mention that the ECU also goes to an injector 'dead time' table that allows a different dead time for a range of system voltages.
  The field builds up at a different rate for different voltages.

   The calculation includes the injector dead time, so adds that to the pulse width.

  The PCIII can only measure the amount of time that the ground is applied to the injector and add or subtract from that.
  At short pulse widths like cruising (at Sturgis) the injector dead time can be a significant percentage of the total injector pulse width.
  For any given system voltage, the altitude correction of the ECU changes only 75% of the pulse width (just throwing out a number for example) but the PCIII changes the entire grounding cycle by the same percentage that it did at sea level. That means it has changed that 25% by the same percentage as the 75% of the cycle that was actually corrected.
  The result is that bikes that were tuned in Minneapolis will go rich in Sturgis. And the lighter loads will be more rich than the high loads.

  I'm not bashing the PCIII, but now, 12 years after H-D started to use FI and now that everyone is a tuner in the last couple years, they might be able to grasp these concepts.

  Doug

[uglyDougly]

I actually don't know how rich they go. It's just that I've been setting the part throttle stuff at 13.5-13.8 for years and the customers would frequently report sooty plugs and poor performance at altitude. Looking at the values of injector time at light load I might guess 5% wouldn't be out of the question. That doesn't sound like enough to soot the plugs but there would be more error at idle.
  If the injector time at idle is 3mS and the dead time is 1mS the PCIII would be causing the adjustment to be 150% of what it should be.
  If the difference in  barometric pressure from Mpls to Sturgis was 29.9 in hg to 26 in hg that would be a correction of .87%.
  If the PCIII added 10%, the error would be 3.4%. That doesn't sound like enough for the customer to notice. Although I recall a lot of PCIII cals with more the 20% at idle.
  At that time, some of the OEM Ducati chips had insufficient altitude compensation that goes back to a baro sensor problem at the introduction of the FI system in 1986-7. Because I knew that and could see it in the chip file, I thought that H-D may not have had sufficient compensation in their cals. That was the only explanation I could come up with at the time.
  Here's a reference to an article.
http://www.yawpower.com/injectordeadtimesarticle.html

   I haven't looked  back very much since then and as soon as the MoCo came out with the SERT that was my tool of choice. Since then there has been little reason to second guess results.

   Doug

[-SeabrookTrickBagger]

Seabrook,
"additional pressure will not increase volume output"
Increasing pressure increases the injector's output. The easiest example is the 51psi regulator vs stock 46psi for MM EFI. This was the only way to get enough fuel from the injectors when the Power Commander II was the only tuning tool available for that EFI system back in 96-98.

"That might depend on whether 6.1 gps was arrived at HD fuel pressure or 3 bar.  At 3 bar, 6.1 gps flowed at HD fuel pressure  would be about 5.7 grams per second."
HUH?

waskier01,
"The 4.5bar pressure regulator increased fuel because I was worried about the duty cycle, also gave me the added benefit of increased atomization for better fuel mileage in cruise mode. My '01 softail is Delphi."

What tuning device do you have? As far as duty cycle is concerned, what keyed you to worry about it?
Increasing the fuel output for the entire engine's EFI mapping by increasing fuel pressure may not be necessary or in the the best interest for performance

Addressing your comment/question about the PCIII lying to the ECM, it is the signal out of the ECM that is modified not the signal in. Lying to the ECM has not been used since the PCII, which went obsolete when the PCIIIr came out almost 10 years ago.

HTH, Bob

Bob,

the totality of the statement was:  "if the orifice is flowing at maximum output to begin with, the additional pressure will not increase volume output."

""That might depend on whether 6.1 gps was arrived at HD fuel pressure or 3 bar.  At 3 bar, 6.1 gps flowed at HD fuel pressure  would be about 5.7 grams per second."[/i]
HUH?"  I guess that remains a trade secret.

Seabrook

[-SeabrookTrickBagger]

I actually don't know how rich they go. It's just that I've been setting the part throttle stuff at 13.5-13.8 for years and the customers would frequently report sooty plugs and poor performance at altitude.
   Doug

Doug,

Could you expand on that statement in conjunction with this statement:  At higher altitudes than that in which you originally tuned the bike, you have less air but the injectors flow the same fuel which will make it run rich at altitude. Correct or incorrect?  Not challenging you, I just don't know.  Of course this assumes that you don't have automatic barometric pressure adjustments in the intake/fuel system.

TIA.

[-SeabrookTrickBagger]

Thanks. Bob.

The DTT TCFI allows you to disable the automatic baro update as a continuing service.  I am not sure if the baro update which occurs each time you start the motor is likewise disabled, but I think it is also disabled when the continuing baro update parameter is set to off.  The reason I asked is that my bike was tuned at an effective 3 feet below sea level and I rode it up to about 10,000 feet in New Mexico with continuing baro update off and I thought it ran nicely rich as opposed to lean.

[-SeabrookTrickBagger]

Tuned in Seabrook, Texas.  The air density level here computes to below sea level.

No black smoke.  I could tell it ran rich in New Mexico, but not that rich since it was tuned lean in Seabrook.  I was in and out of the mountains so much that at one moment I was in the desert and the next I was at 7k feet.

Sorry we lost connection last night but my battery died in the middle of a gem you were telling me.

[-SeabrookTrickBagger]

Thanks. Bob.

The DTT TCFI allows you to disable the automatic baro update as a continuing service.  I am not sure if the baro update which occurs each time you start the motor is likewise disabled, but I think it is also disabled when the continuing baro update parameter is set to off.  The reason I asked is that my bike was tuned at an effective 3 feet below sea level and I rode it up to about 10,000 feet in New Mexico with continuing baro update off and I thought it ran nicely rich as opposed to lean.

I went back to some old notes on the DTT IId and noticed that my notes indicate that each time the DTT IId is turned on, the unit takes a barometric reading whether continuous update of barometric pressure is turned on or not.  It appears the effect of continuous barometric update, when activated, is to adjust for barometric changes during operation and between startup/restarts/shut off.  So that is why mine ran rich but not that rich at altitude.  Had to correct my erroneous recollection ........