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timing calculator

Practical Diesel Tuning

Discussion and questions related to the course Practical Diesel Tuning

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hi Nick,

i have made a timing calculator its mostly done haven't checked the margin of error or the rounding mistakes yet but for the most it seems to be accurate based on the curve of the 3d map,

i wanted to ask on the stock timing the percentage is 376.5% at 500rpm 0mm3 is there a reason for that is it the cranking timing? does the engine need more timing in specific situation? like idle deceleration and high load low rpm?

is there a do's and dont's of using timing calculator, or can i make the whole table 50% or higher, how would you recommend approaching it less percentage at cruising more at wot and not below certain rpm(1500rpm or 2000rpm) or single percentage across the whole table is works fine,

in general if the engine still making most power around 80% or 100% btdc would you say its safe to run that or is there a maximum like 60% or 50% for reliability, since we cant estimate cylinder pressure from detonation is there a rule of thumb or is every engine different and to tune 5-10hp below mbt timing


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There are always do's and don'ts when using a timing calculator. Do not use or think of it as a "perfect timing" tool. I personally do not like using one and i know a few other professional tuners who also dislike using them as well. They are more for seeing how a fuel pressure change will alter your injector split or "timing". But a timing calculator tells you nothing about your intake air temp, manifold pressure, or engine temp, so to base all your timing off of injector on time only is silly IMO. The reason you see timing ramp up in the corner like that is for two reasons. One, this helps with start up and getting the fuel in sooner when the engine is both cold and spinning slowly, giving the fuel plenty of time to warm up and aid in good combustion. Two if the RPM starts to drop during normal idle conditions it'll help prevent the engine from stalling. OE's set idle timing based mainly on noise and emissions, so increasing it will get closer to MBT. As far as detonation goes a diesel is always "detonating" so our goal is to place that detonation on MBT, this timing number will change constantly if you change your fuel amount or fuel pressure. That's where a timing calc comes into play. Most OE tunes will have negative timing for two reasons, to aid in turbo spool up time and emissions. I personally would have two different tunes for a truck that drives in the city only vs one that's on the highway mostly or only. Having a well tuned negative timing valley just off idle can really aid in turbo spool time, but too little timing can also hurt mileage if you happen to cruse in that same region. That's why i said i'd have two different tunes for a city only or highway only truck/car. Most tuners will just pick one or split the difference. One last thing, if you look at any newer diesel's ECU they have injection configurations based on engine temp, charge air temp, and fuel pressure. They range from cold, warm, hot, to low, medium, and high pressure. This is because these conditions really change how the fuel combusts thus changing when the fuel should be sprayed. Timing calculators don't take anything but pressure into consideration, so be aware of that when making changes.

thanks, this is what i was thinking coming from petrol engine background it didnt make much sense to me that you can just estimate the timing,

i had another issue i tried increasing the timing in the max soi main timing, it does increase but not as much as i command and there are other tables that im not sure what it does,

main soi timing which starts at 16degree at 500 rpm and drops to 0.6degree at 4800 its in positive value here so im thinking it might be atdc because max soi is negative btdc

there are type 2, type 3, type 4 which i think is maf

No Main injection event timing will be 16 degrees anywhere near idle, that map you are looking at is your pilot injection timing map, your pilot injection will happen X amount before your main event based on that map. Your main injection map will be more like -1* to 4* at idle. Diesels don't require 12-15* degrees of fuel injection advance like a petrol engine at idle because they don't operate in a vacuum. Flame fronts are slower to release heat in a vacuum, thus timing is a lot lower in the diesel world. Diesel's don't use throttle bodies for air control either, if they do it's only to help the EGR flow into the intake and to aid in a smooth engine shutdown. Remember diesel's Engine speed control is done by fuel amount and fuel timing only. Here is a stock timing map on a ford 6.7L diesel.

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just to clarify im tuning toyota landcruiser they use negative value for timing,i usually tune max soi main timing table but i noticed the only 1st gear advance the timing but from 2nd to 4th its closer to stock

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Can you post the tune file in here so i can view it? I want to make sure i'm not missing something but you should be able to go way above 45mm3 with positive timing. Do you also have a data log you can post in here of WOT? I'm really curious to know how much mm3 they are commanding and what it's actually producing.

this is the tune the fuel rate is 100mm3 and drops to 95mm3 at wot, the timing doesnt track properly with tune especially on higher gear

im commanding 110mm3 which is maximum pulsewidth on stock injector but 100mm3 is perfect afr

on the datalog the timing is positive but on the tune its negative

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After reviewing your log files it looks to me like the template for your timing tables within the HPT editor is swapped left to right. It appears that the top to bottom fit is appropriate. As RPM increases your timing lookup decreases in the table (this is opposite of the way it should work). In the log file the timing appears to track in the tradition way, increasing with load and RPM.

I'm tempted to say that your Max SOI tables are oriented correctly, but the units look to be in deg ATDC instead of the more tradtional BTDC.

Hope this makes sense,


it does, but its probably some weird toyota logic, even in their gas engines they have some weird timing algorithm, my guess its torque mapping related

what is confusing me that the timing doesnt track 100% with max soi, do you think it has some safety features to reduce timing over time or gears. or is it unheard of in the oem level

im gonna experiment with the other timing tables in combination with max soi and see what works, main timing alone didnt do any difference at wot

I think Nick is 100% right about the timing being ATDC. I've never seen that but i also haven't been doing this for many years yet. I also haven't messed with many Toyotas lol. It appears to be using multiple timing tables at the same time, Typically newer ECU's will interpolated based on a percentage of the specific table being used. So say you have one table with a value of 10 and another with a value of 2, if it was using both tables in a 50% capacity you'd see a timing value of 6. The problem is we don't know what that percentage is without having a PID to log. So you have two choices, one get in contact with HPT and tell them you're looking for the ability to monitor your timing tables by percent of utilization. Or the more likely choice you will have to make changes in one table, flash, and retest to see how much each one is being utilized. But it looks like it's using table 42733 during your longer WOT pull. So i'd start there and see how well that works for you. You are also making some boost! That vane position is pretty aggressive during WOT, does this vehicle have a back pressure sensor by chance?

no the car doesnt have back pressure sensor or egt but the engine is still making more power at 24 psi but alot more iat heat too,i tried going down to 18 or 20 psi and the vane position is the same around 60% i dont think its direct boost related 1:1 which is weird maybe the pid is not accurate? or maybe ecu control bov or something, i have done some research and most of people say the turbo max psi is 23 and it seems to be around it i tried 25 and 26 it didnt make more power

its a friends car and he wants a max effort tune, the car when from 10.5 to 6.4 at 0-100km with tune and valvebody only and he wants more