Injection Timing Calculator

[mecanicman]

If you are reading/using this, do not PM me about it. I am no longer supporting this. Feel free to use at your own risk, but all pms regarding diesel tuning will be deleted.

I have never been able to make the injection timing calculator made for hpt work(For anyone who found the other post about injection timing calculator, all it does is invert the hpt tables so you can use the efi live calculator, I did not realize this back then so I created this one). So, I took version 2 that Josh made and reworked it for hpt myself. If you already have a working calculator, this one is probably no different. I just reworked the tables to correct the axis, and corrected a formula mistake made by Josh in the LMM table. I did considerable error checking against Joshs table and am pretty confident it is correct, but use at your own risk. If you come accross any problems, I would appreciated the feed back to correct it. Enjoy.

Website has been updated, spread sheet is now attached.

Edit:fixed formatting in lmm table

[mecanicman]

bump

[Johns98TA]

Hey man I downloaded this spreadsheet and put my tune into it to test it out. Even at 50% it really added a bunch of timing, so I didnt even try flashing it into the PCM. At 2750 rpm, the spreadsheet was adding 10.5 degrees to the stock timing table. Do I dare even try that?

Truck is a 2006 LBZ Duramax. The tune Im running: I have added +10% fuel to the Base Fuel Qty, and +10% to the desired boost tables. I also added +2% pulsewidth to the injector PW table. I left the timing stock, and disabled post injection. I also upped all the torque tables so the pedal will command 900ft-lbs of max torque. Fixed all the tables so it will rev out to 4000. This thing runs smooth and quiet and HAULS. Almost no smoke. It runs so good Im afraid to try adding any timing? Thoughts?

[mecanicman]

At 10% extra fuel, you may run into a problem above 3250 rpm. You will have to manually limit the table at whatever timing value you are comfortable with(the common rule of thumb is dont excede 30*). I have done tunes with more fuel then your describing and reving to 4000 rpm and dont recall having an issue, post yours before and after and I will have a look.

[nmcqueen469]

Glad I found this thread, I'm going to try this with a friend's LLY.

[MikeOD]

I'll be the dumb guy...I can't find the fuel rail pressure table to copy into the spreadsheet..what am I missing?

[mecanicman]

Under Fuel system after trans diag across the top.

[MikeOD]

I found it and was about to post that...you can call me slow, it's ok, I won't be too offended. Thank you for the help. Do I paste the results into all 5 of the timing tables?

[ajamesbond007]

mecanicman - used your timing calculator. works great as far as I know

Can you shed some light on why 50/50 timing is the ideal timing (or at least the best to start out with?) I have read many forums saying this is the case but just am curious as to why. Didn't know if you knew any info on this or not.

Thanks!

[MikeOD]

Now that I know how this works, I think I'm going to spend some time monitoring where the truck drives in the maps that we're calculating, and then play a little more to balance efficiency down low and EGT up top...I was able to pull his EGT back a little bit last night and the truck certainly feels punchier down low after using this calculator. Diesel tuning is certainly a whole different ball game.

[mecanicman]

MikeOD-Yes, paste into all 5 tables.

ajamesbond007- I will do my best to explain as I understand it, hopefully dont get beat up to bad if Im wrong! 50/50 is a compromise between best fuel economy and power. Something closer to 40/60 delivers better power while closer 55/45 will get you your best economy. These are generic values, every engine will be a little different and affected by camshaft(most diesel cams are pretty tame so stock they are all pretty close). On a gas engine, all the fuel must be in before your ignition. Once ignition has happened you have one large controlled burn and the expansion of gases forces your piston down. On a diesel engine, you put fuel in before you reach point of ignition, but you can continue to add fuel after the initial ignition that will continue to burn and add cylinder preasure(why a diesel makes such incredible torque). By adding more fuel in initially(55/45) your fuel burn is all complete long before exhast valve is open and you have maximized your use of fuel. By adding more fuel as the piston travels down (40/60) you continue maximize your cylinder preasure/torque/power but may open an exhaust valve before fuel burn is complete costing fuel economy.
Hope this helps.

[ajamesbond007]

Makes senses to me. I know there are many variables, but what would you say is the maximum advance you would command for best fuel economy in the cruising range?

[ajamesbond007]

AAnd thanks for explaining the compromise part =]

[mecanicman]

I dont have a maximum value. I have played with up to 65/35 in the driveability areas for fuel economy. I have not seen any benifits past 60/40, and the 60/40 only on a couple of trucks. 55/45 seems to be the best for most of the trucks I have done. The only maximum value I try to follow is not to exceed 30 degrees timing. You always have to keep in mind how much actual fuel is going in as the engine is building compression as you dont want to hydraulic a cylinder. I have seen 3 rod/crank failures that I was able to examine the tunes on. In these cases it appeared to me that to much fuel was going in before tdc.
The timing calculator is generic, it works well for good fuel economy but applies the theory best for one area to the entire table. On my more recent tunes, I go for a drive with the owner with scanner and have them drive normally. In these driveability areas I set it up for 55/45 to try for best economy. I then have them drive a little more aggresivly suchs as passing and set those areas up as 50/50. Anything abouve that I set in the 40/60 range for max power. I have gone higher on engines revving higher.

[ajamesbond007]

Cool thanks for the reply. I am going to try that on my buddies truck and see if I can get another mile or so.

I have looked at lb7 stock tune and noticed that according to your timing calculator, the majority of the lb7 timing table had 0% of the main injection BTDC. What really boggles me is why would GM put such retarded timing into their timing tables, especially in the cruising range?

[mecanicman]

I think its because we are not accounting for pilot injection. It gets complex and I have not figured out how to account for it all.

[MikeOD]

By adding more fuel as the piston travels down (40/60) you continue maximize your cylinder preasure/torque/power but may open an exhaust valve before fuel burn is complete costing fuel economy.
Hope this helps.

I'm guessing thats where the huge amounts of soot come from on some tunes.

Thank you for the explanations/help. I've got a lot more experimenting to do on the LBZ I've been working on, but since asking you for help I've had a LOT more success.

[ajamesbond007]

Mecanicman - got a question about the timing tables... during start up and cold operation, what do we need to do with the adders, such as ECT and IAT? just reduce them in the areas that we put the 50/50 timing in or delete them or leave them alone? I would guess it would be a good time to reduce them at least in the 50/50 area, but am unsure....

[mecanicman]

I have played with it, but dont find it to make a lot differance either way. I dont usually play with the timing, i just play with the mulitplyers, drop them down about 3 boxs so they are doing nothing at a lower temperature. In my expieriance it has only made a differance at low temperatures, runs better with those tables enabled(I had them totally disabled).

[ajamesbond007]

I figured getting rid of them completely would cause problems since GM did put those tables in there for a reason. Thanks for clarification