tune coming down to idle hard

[Cjsobas]

I built a fairly hot tune and my problem is I'm having a hard time getting out to Come back down to idle after i rev it. Takes like 20 seconds to come back down. Anybody ever run into this problem

[mpdtune]

Post up your tune file.

[asmithIII]

Too much duration at low fuel settings. Many people only add duration at higher fuel settings. Injector on time is sometimes increased by mistake at low fuel settings without reducing the rate of fuel delivery.

[Cjsobas]

Thanks a bunch. That was the problem set it back to stock.at low rpms an mm the tune runs alot better.

[asmithIII]

How many percent over stock did you increase duration at high rpm and load?

Here is what I've found.

A stock engine with a clean fuel filter/strainer is sometimes straining to achieve stock duration and pressure under full load and rpm. If you increase duration very much, then monitor both the desired and actual fuel rail pressure. If desired pressure is less than actual pressure, then a lift pump is your next investment. After a lift pump, prepare to retune engine or risk transmission damage.

Did you know that many tuners reduce the duration of injection in the mid-range to increase fuel mileage?

The theory is to get the fuel to burn hotter but shorter. Works well, up to a certain point. I know of a few different ways to burn fuel hotter but shorter. Most of my methods use the rate of fuel injection to achieve best efficiency.

Hope this will help you in the future.

[Cjsobas]

I been data logging the frp and its not dropping off but your right on the lift pump that's the next thing I'm buying. As for how much i increased, i don't know i data log, see what cells im using then bump them up, then smooth the map out. That free tune i didn't smooth i thought who ever downloads it can adjusg to the preff. I try not to go above 3000 PW I used josh h timingcalculator at 50% btdc, did the same for rail psi

[asmithIII]

3000 micro-sec pulse width at 3000 rpm means a duration of 54 degree. Saw duration similar to that on a stock lml engine pulling a hay trailer with 82 PSI boost.

One day I'm going to make an economy tune based on a program like yours by cutting the duration in half.

[Cjsobas]

damn 82 psi thats a bit much haha. i dont know im new to this just makeing stuff and seeing how it works. yeah i noticed on the tunes that the dic is lying a bit more about the millage than i thought once i hand calulated it out

[asmithIII]

rechecked data log

72.6 PSI was maximum at 2508 RPM

3030 us main duration(not active) but post injection #2 was active
3030 us pilot #1 duration(not active) but post injection #1 active
3030 us at 2500 RPM has a duration of more than 45 degrees of injection...if both post injections are active then total duration is over 90 degree of crank angle

30.3 mm main fuel delivery
30.3 mm pilot #1 fuel delivery
Calculated fuel rate 96.4 mm

EGT at this point was 750*F
EGT max was 824*F

Main Injection Timing was 2.3 degree at this point

Turbo vane position at this point was 50.2% giving 72.6 PSI boost

It is obvious to me that the lml engines are using lots of air and a slow rate of introducing fuel into the combustion chamber to meet emission standards. Peak combustion temperature is being reduced by excess air and by slowly injecting fuel into the combustion chamber. Just food for thought.