Smarty UDC Initial Impressions

AH64ID said:
So in talking about duration and timing I thought I would add this.

The duration table tells the ECM how long it takes to inject "x" fuel at "y" pressure, so it's more of a calibration table. It does not give the exact pulse width for a given load/rpm, that has to be calculated (extrapolated, blended) by the ECM for every injection.

What I have attached is an example of a calculated pulse width table based on stock duration and pressure. To calculate this the ECM (or a timing calculator) will take the desired fuel rate (load) and rpm to the rail pressure table. So lets use 100% load and 2000 rpms. On the stock table that commands 20,885 psi (which is 144 MPa; I use MPa because I only had to extrapolate 156 pressure columns, vs 145x that many). Now if you look at the modified labeling on the duration table you won't find a row that has 20,885psi as a whole number, so we have to extrapolate (just like the ECM will). That extrapolated value comes out to a desired pulse width of 2126us (so it takes 2126us of injector open time to flow 140mm3(100% load) at 144 MPa (20,885 psi)).

If you compare that to the UDC labeling you can see there is a big difference. According to the UDC labeling 2000 rpms and 100% load would be 386us, and that's not correct. This is why it's necessary to look at the modified labels I posted if your going to calculate pulse width and/or timing.

So, like I mentioned, the photo is what the desired pulse width will be with stock pressure and duration in relation to rpms and load. This table must be calculated, it's not available anywhere in the ECM that I am aware of, certainly not anything we can see with UDC. The ECM will then blend/calculate between the cells when the load and/or rpms are not exactly as indicated. (i.e. 2050 rpms).

There was also a question as to why duration increases with rpms. You can see from the attached photo that it doesn't. The reason it doesn't (generally) is because the higher the pressure the faster the fuel is injected (this is why pressure boxes make more power, they get more fuel in the cylinder per injection event and the additional fuel is what makes the power, not necessarily the pressure). As an example a 2000us pulse width gets you about 110mm3 of fuel at 14.5K psi, and 140mm4 at 23.2K psi.

So under WOT acceleration the pulse width will decrease as rpms increase, until you hit your peak pressure and then the pulse with stay the same regardless of rpms. With a constant rpm and increasing load (pulling a hill with a trailer) the pulse width will increase almost all the way to WOT, but the depends on how your pressure map is built. Looking at the stock pulse width table you can see that at some rpms it increases all the way to WOT, but at some it dips and then climbs back up.

So, lastly, when we modify the duration table we are not directly modifying the pulse width. Instead what we are doing is changing the "calibration" numbers and telling the ECM it take more (sometime less) time to get the same fuel. So the ECM still only thinks it's injecting 140mm3 (100% load) but really we could be injecting a lot more fuel and thus added power.

PulseWidth_zpsa57c6404.jpg


Clear as mud??
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Nice to see some one clear that up for the UDC folks. On each cycle the ecm has determined how much fuel to inject from torque demand and uses the "injector calibration table" to convert mm3 to injector energization time.

Tricking the energization table time is still a brutal way of calibration but i suppose for the $$ not to shabby.
 
AH64ID said:
It's more of a plateau until 31.4 then drops and starts climbing as fueling increases, but I don't want all that fuel BTDC at I get above 30% so I back it off a little. In the 31.4 load cell I only run 70% of my fuel BTDC, where at 18.9 I run 100% of it BTDC and it's all injected 2.7° BTDC.
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Clear as mud! Your controling fueling with tq management?!
 
Well towed a 15k trailer today did some hill climbs and blew some black smoke and pegged the pyro so back to square one! Man every time i think I've got it nope try again!
AH64 has my mind in the mud I'm not sure what to do now.... That dip in the middle has me wondering why and the tequela has me wanting to throw it out the window!
 
dangerous06 said:
Clear as mud! Your controling fueling with tq management?!
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I haven't touched torque management since my first or second Smarty Jr tune back in April.

dangerous06 said:
Well towed a 15k trailer today did some hill climbs and blew some black smoke and pegged the pyro so back to square one! Man every time i think I've got it nope try again!
AH64 has my mind in the mud I'm not sure what to do now.... That dip in the middle has me wondering why and the tequela has me wanting to throw it out the window!
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It sounds like your duration is too much for the air you have when you put the load of a turbo on it.

The dip...

Okay, so the peak on the low load side of the dip is for mileage. The reason it's so high is to get the most out of the fuel. This creates a lot of cylinder pressure (power) for the fuel. If we were to maintain this level of relative pressure (think psi per mm3) we would blow the head off at higher fuel rates, and it would be NOISY and not make much power. We can get away with it at low load because the cylinder temp, rail pressure, and boost are lower, this means the ignition delay is longer. Combine a longer delay with slower piston speeds and we get good mileage from high cylinder pressure (post combustion) at the proper time.

The valley starts where the cruise region ends. This is where fueling starts to ramp up and we have to make the power a little different. As fueling increases so does temperature from combustion, so we need airflow to both aid in combustion and keep it cooler. The very advanced timing of cruise doesn't make for as much exhaust flow, and thus lower airflow/boost. So we have to back the timing off. As fueling increases we need to increase timing to get all the fuel in the cylinder before it's too late, as we don't want to chase the piston down the powerstroke with the flame (like stock does).

I mentioned a % BTDC and % ATDC. In the cruise region we want all the fuel injected BTDC, so when the fuel ignites it is near TDC and peak pressure is 12-18° ATDC. In a spool region we want a little more exhaust to get the turbo lit (this is where each truck is different, as turbo's, cam's, injectors, altitude, intake, etc all have an effect). Then at full tilt we want to get as much fuel in as possible, but don't want too much ignition BTDC or we create negative torque which results in excessive cylinder pressure and lost power.

At WOT a good starting point is 50:50, so 50% BTDC and 50% ATDC. To find what 50:50 is we have to know rpms, rail pressure, and duration. From the rail pressure and duration table we can determine the desired pulse width (injector open time), and from that number we can determine how many degrees the injector will be open and thus create a 50:50, or any ratio we want.

In the spool region lets assume around 40% BTDC, and then blend into around 50% BTDC at about 70-100%. That makes the bottom 5 cells in the rpm column have the same 50:50 split, but the timing is gaining the whole time. That's because the pulse width increases the whole time, and we have to advance timing to get the 50:50 split.

So this photo is what the timing would look like with stock duration and pressure with a 50:50 split across the board. As you can see there is no valley, just a gradual climb all the way up.

50_50.jpg


This is what the timing would look like if we stopped it at TDC. As you can see it's not enough timing in the cruise region, but above 31.4% it's starts to be too much. This is where the dynamic timing of a CR really shows how well it works, we can change the timing to be optimal at any rpm/load.

100.jpg


So now lets create a valley. The spool region will be a 40:60 split, upper rpms a 50:50, and the cruise region will be about 150% before TDC (i.e. if it's a 100us pulse then it will start 150us before TDC and end 50us BDTC). This is only 1600+ because below that is not really important to the discussion, and would take more time that I want to play with.

But you can see that a blanket 150% in the cruise region doesn't work. It's still not enough timing at 6.4%, but too much at 31.4%.

MIX.jpg


mixcalc.jpg


So does that help explain the valley? Here in a few days I hope to push the timing calculator public, but as it's been said before it's a tool and not a rule. It helps you visualize where your injecting fuel, which makes for faster initial tuning and safer tuning as well.

Just one quick addition on dynamic vs static timing. This is what the split would look like if we were staticly timed at 16.5°

There are very few regions on that map where it's optimal. At low rpms it's injected so early it's just sitting in the bowl waiting for enough pressure/temp to ignite. That's too early, and one reason why 12V's are so noisy, 24V's with their single event have similar noise reasons.

STATIC.jpg
 
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AH64ID

Look forward to the calculator to try and understand this better. It always takes me a few times reading your posts to try and decipher what is being explained.

Have my truck partially disassembled. Adding drive pressure guage, headstuds and arson kit. Trying to decide if i want to port out the stock wastegate now or wait so I can do some testing pre/post modifying the wastegate to better understand how it effects operation.

Thanks for you Posts.. They have helped me.
 
JP-4.5 said:
It always takes me a few times reading your posts to try and decipher what is being explained.
Click to expand...

Hopefully it comes across clear. I always find little ways I could edit the post to make it easier to understand, but we can't edit after a few minutes here on CompD.

I think the calc is good to go, what I need to work on are instructions. It's easy for me to use since I built it how I wanted it, but I need to think about it if it were the first time I was looking at it.
 
Looking forward to the calc!
Quick Question: Say rpm is a constant at 2000. Cruise will be at 8 BTDC from 6.4 to 31.3
What does towing a load of 15k do to the timing. I mean to say is 8 BTDC To much because of the weight being pulled? Then if you encounter a incline and load goes to 50 the timing at that range is 2.5 BTDC would that be not enough and cause the high temps and heavy black smoke? How would you do the calc for that?
 
You set the timing for the fuel load, and the drag on the motor determines the load, and thus the timing/pressure.

So pulling a 15K trailer won't let you run in the 0-25% load range except on a downhill. In the flats your in the "spool" range, and on the hills it may go up to 100% load.

2.5° at 2000 rpms doesn't seem like quite enough at any point in the timing, but your silver bullet is a slow spooling and higher rpm turbo, so you might need less timing to get it to spool. Black smoke is too much fuel, or not enough air.. generally, but can indicate improper timing too.

Have you played with duration below the 3100 rpm column?

Tuning for towing is no different than tuning for everyday driving, other than fueling that may make ok EGT's when DDing might get too hot when sustained with a trailer, so it's a balance of daily power and towing power.

My turbo is probably good for 100+ hp over what I make, but I can run WOT up thru 7K feet at 2K rpms with a trailer, so I leave it alone. If I didn't tow I would turn the fuel up.
 
I think it does. I noticed a stronger/smoother bottom end. My cam is a Stage 1, so nothing fancy and probably how it would have been from the factory if it weren't for the EPA.

The 3rd gen 5.9 grind has the largest intake profile and smallest exhaust profile of any ISB cam in a Dodge. That means low airflow, and lots of exhaust left in the cylinder.
 
We have been playing with an 06 to clean up some smoke. He is running 90 HP injectors with twins. According to my UG at an engine load area around 35%-45 % in the RPM range 1200-1600 still getting smoke. My question to John is if I mess with area's will help or because the labels are labelled wrong it really want effect that area?
 
Are you trying to decrease duration?

Have you messed with duration between 0-3000 rpms?
 
We were cleaning up the smoke. Tq management cleaned up pretty much the whole issue except for that one area. So now we will be decreasing duration in the area I described... He will be trying this tomorrow so I find out.
 
I would put duration at that area stock, or mess with all the cells. The reason is if the combo of duration/pressure/timing creates smoke on acceleration then it will create smoke while cruising (or a good chance it will). And while you can fool the ECM with less fuel for acceleration it still takes so much hp to cruise.

I would back the timing off a few degrees and try, that should decrease smoke and increase boost.
 
I tryed lowering the duration to reduce smoke but it ran crappy even more smoke up top never cleared up. Is there something that needs to be adjusted if duration is dropped?
When you say you increase the last three rows in duration that means the last three load cells or the top 3 rpm cells? I'm going to have to except that 20mpg is my max no matter what I do and should work on the smoke on excel and cruise it's just a haze but can be seen like an old truck going up a hill!
 
Where did you reduce the duration at, and by how much? Yes duration changes need timing changes.

Chances are that you took out too much duration, and didn't get the turbo spooled.. and well that means less air up top.

I mean the last 3-4 columns, not rows. How far up the column (work bottom up) you go depends completely on your pressure map and desired fueling rates.
 
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Test drove this tune today. S06 smarty.


Pulls hard to 3800rpm then tranny shifts.

Flux 3's, 6.7 cp3, 62/71/14 and S480 87 turbine 1.10a/r, PCS controlled auto


Any comments on things that don't look right? Runs better than it ever has but this is all new to me so let me know if I'm on a path to destructive ends.

Any other 03/04 guys running a similar setup and care to share what works for you?


On edit: This is my current PCS tune with 4th shifts at 150mph or something like that to really wind out 3rd gear.
 

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OK you know that feeling you get when something runs so good your afraid it's going to die the next day?! Well my latest tune which I'll post later today has given me 25mpg hand calculated!? Only glitch is a small surge and retreat going down hill at 2000 rpm and 0 load. Like bucking a little?? That's with cruise control set at 67. Not sure what that means but maybe someone can look at this tune later tonight and tell me if something is way out of spec! Man I hope I'm wrong about the imminent death!
 
I used to get surging like that with the TNT tunes.. I will look back in my notes and see if I can find what setting was causing it..
 
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