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Discussion Starter #1
Now that I have more time to play with EFI Live I need help in understanding the specifics of timing.

Now I understand that if it (timing) is too early the truck can smoke and become quite ‘diesel noisy'.
Imagine the spray of fuel as a fist about to hit the piston. If it is hit too far before top dead center it would not only hurt your fist and the piston but it would make a louder than normal bang as the two things hit head on.
And I understand that if it is to late the truck will not use all the fuel in combustion and the result will be less power.
If the piston had gone past top dead center and was hit, the force of the hit would be going down with the piston so you would have too little
impact on it.
So my question is how do you know when your timing is 'perfect'.

From looking at other tunes it appears to me that most tuners basically just throw in a whole bunch of extra timing to make sure they get all the fuel injected before TDC. I guess at that point if they hear clatter they back off until it is quiet enough. The end result seems to be probably a lot more timing then is necessary.

In a perfect world what gets you the best results? I assume the absolute ideal situation is that the timing is set to start injection just soon enough to get every last drop of fuel in right at or before TDC?

It also seems to me that the best way to figure this out would be to figure out the math? You are injecting fuel for X amount of microseconds. You know that the piston moves Y amount in Z time. Therefor you must start injecting fuel A seconds before TDC. Is my theory correct?

Please feel free to share how you tune your timing and offer any insight you can to my theories and questions.

Don't hesitate to reply even if you aren't sure if you are right. We are here to learn and feed off each other.
 

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Yeah, us gasser guys are spoilt with knock sensors ;)

I imagine on a dyno like a Dyno Dynamics where you can hold specific loads you would probably see torque pick up and drop off as you find the ideal timing point?. The other thing is the pilot injection has a lot to do with helping rattle, but as far as deciding, too much timing, too much main pulse, too much pilot, not enough pilot........:confuzeld

Cheers,
Ross
 

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Discussion Starter #3
Interesting. Thanks. I'll need to talk to my dyno operator ;)
 

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Discussion Starter #4
I have a feeling the ones that know aren't going to be willing to share.
 

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It's a lot like my comments to Turbo lcc about boost tuning. I find that it is very important to have a highly accurate dynamometer to truly map out the best timing for the fuel and bost commanded. A degree here and there can make a nice difference or reduce power.
 

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I have a feeling the ones that know aren't going to be willing to share.
When it rattles you have too much........:cool:

It's a lot like my comments to Turbo lcc about boost tuning. I find that it is very important to have a highly accurate dynamometer to truly map out the best timing for the fuel and bost commanded. A degree here and there can make a nice difference or reduce power.
I don't have a dyno in my shop, but my SOTP-Meter on the street seems to be pretty good lately.........:D

T;) NY
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Discussion Starter #8
That is where being able to change on the fly would be a huge advantage. I'll see what my dyno operator can do since it's a heck of a long way to drive down there and park on your dyno.
 

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Discussion Starter #9
When it rattles you have too much........:cool:



I don't have a dyno in my shop, but my SOTP-Meter on the street seems to be pretty good lately.........:D

T;) NY
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I agree when it rattles you have too much but just because it's not rattling doesn't mean that you don't still have too much.

I don't think that increasing timing until it rattles then backing it off until it stop is the best tuning method.

I think parking on a dyno with the abiltiy to change on the fly would be the best bet.
 

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Measuring and correlating hp/tq to effective cylinder pressure as boost,timing, and fuel table adjustments are made on a load cell dyno would seem to be the most scientific method.
 

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Log Files will tell you alot if you log the right PIDS........;)

Controlling parameters and load on the dyno is a good tuning tool, but we have seen how dyno tuning can translate into less than desirable streetability in the past.

I find that tuning on the street under all kinds of driving conditions and developing tunes that react in a positive way on the street is much better than worrying about the peak dyno numbers.

All of my tuning has produced big HP/TQ numbers with excellent drivability. Ask anyone that has tried one of my tunes, you will get the same results and answers from all you ask.

I'll stick to my methods, it works for me.

I hope everyone else that is using EFI-Live has their own methods that work for them and they get the results they want too.

Good Luck,

T;) NY
 

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Currently my tuning methods have been slow and cautious. The biggest hold up for me has been the weather. Man I can't wait till the track opens not to mention the next efi update. Naturally the track isn't the best place to build a smooth street tune but it is a far more controlled environment than the street. Regardless the "perfect" tune will most likely need street, dyno, and track tuning to get it right.
 

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Max :
That is a hard question to answer, in my eyes each cylinder shoud have pressure sensers to optimize performance per cylinder not treating all as one .
If you are going to far advanced on your timing you are losing power and if it is retarded to far you are losing power , which you already know.
My answer to your question is , look, listen, and feel , I think you have the stuff .

:ro)
 

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It's about impossible to feel the subtle differences with your "butt dyno."

The image added here is playing with minor adjustments to the timing:
 

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It's about impossible to feel the subtle differences with your "butt dyno."

The image added here is playing with minor adjustments to the timing:
I assume the label TBIQ means table B0727 and if you were playing with timing maybe the chart should have been labeled B0910 or Maybe just Timing "C".

I don't think timing has that much of a linear effect on the HP/TQ curves in my experience but increasing the TBIQ tables by a linear % might..........:cool:
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Pay no attention to the names of the runs, that's insignificant. I did not do a good job of updating the names of the tunes on the dyno software.

These were all timing changes at different points.
 

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Finding optimal. Answer: Dyno test.

Too early:

Power loss due to compressing burnt gasses. Remember, the power comes from the work difference between compressing cold air, and expanding hot gasses.
NOx due to increased time/temperature.
Knock due to higher rate-of-change of cylinder pressure.
Increased heat loss to coolant. (increased time/temperature exposure)
Higher max cylinder pressure (mechanical stress)

Too late:
Loss of power due to lower BMEP.
White smoke due to unburnt fuel (only at real late timings).
Increased HC emissions (see above)

There's a best timing for every fuel rate, fuel pressure, RPM and air rate.

And BTW, for gassers, timing at incipient knock (when the sensor goes off), is usually too advanced by a few degrees, for best power. A knock sensor measures knock, not optimal timing. It's there to protect the engine in the event of bad fuel, and/or the closed loop timing value being too aggressive.

Search the net for papers on diesel timing. There are a few good ones out there. From the ones I've found, best power timing seems to be about 10 BTDC for HPDI diesels. Emissions-limited timing is closer to 0.
 

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For something interesting, plot compression ratio to crank angle. Now ask what ratio is needed to light off the charge? Does the charge even start burning before 20 degrees?

Next exercise is to plot the pulse duration in crank degrees at different RPM. In other words, how far has the crank moved while the pulse happens. Modest tunes will take 30 crank degrees or more to complete an injection pulse at 2800 RPM. More fuel, longer crank duration.
 
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