Smarty UDC Initial Impressions

Just tested it, and it does command the set rail pressure above 71%. So it's just guessing at the load % after that...
 
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Walker said:
Yes. I had the rp set to 18,000 up to 75% load then had a jump to 24,000. It should the jump on my rp gauge.
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I just wanted to make sure I understood you message correctly. I though I remembered a message about that from Marco.

Does your scanner show the throttle position correctly? If so, then you can use that and be pretty close.

Paul
 
Aside from towing I don't see 65-99% load often, its usually 0-50% and 100%.
 
Quick question on the torque management: How Does this translate to engine load? Some of the samples have it max out early.
 
Think of torque management as low rpm fueling. The stock tune limits low rpm fuel to 54% tq, by increasing the upper load percentages you tell the ECM it can fuel harder at lower rpms.

If you increase the low load torque your throttle becomes very touchy, but the upper load can be made smooth. I run lower torque at low load, and higher torque at high load and it's very easy to drive on dirt roads and towing, thou not as much fun on the street.

It's possible that torque management will effect total engine load at low rpms, but by the time I get to an rpm where I don't mind being WOT the load always reads 100%. I can see 100% load as low as 1400 rpms. Anyone else?
 
What should I be adjusting to clean up smoke when taking off at wot? Back off on duration or add timing down low?
 
Trying to go for max milage when cruising at 2000 rpm Would +3 at 31% load be in the ball park or is a higher + number or a lower - number be better? Just trying to figure the timing numbers out.

I think cj42 question is duration needs to be lowered but remember on first take off things need to spool up and a mashed pedal can never be cleaned up.
 
dangerous06 said:
Trying to go for max milage when cruising at 2000 rpm Would +3 at 31% load be in the ball park or is a higher + number or a lower - number be better? Just trying to figure the timing numbers out.

I think cj42 question is duration needs to be lowered but remember on first take off things need to spool up and a mashed pedal can never be cleaned up.
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Cruise for me is about 0-25% load, and taper to "spool" by 31%.

Play with the timing, increase it until mileage stops increase or you get rattle. I wouldn't go above 8°.

cj42 said:
What should I be adjusting to clean up smoke when taking off at wot? Back off on duration or add timing down low?
Click to expand...


That will be duration and torque management. You may also play with rail pressure... and of course rail pressure/duration effect timing.

Due to the injectors you may need to keep tq management around stock, or lower (in the upper end, you can bump the bottom end for pedal feel) to effect WOT smoke from a stop.
 
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Okay, so this is going to be a quick lesson on checking your peak timing. The purpose in this is to make sure you don't have too much timing for your fuel. It's possible to have a low timing number, say 16° but not have enough fuel for that to be optimal. A 50:50 split (BTDC/ATDC) seems to work good for heavier fueling. A little more if you are really trying to squeeze every hp out, maybe 51-52 BTDC or a little less if you don't want quite as much piston heat, 45-48. Those are rough numbers I have played with, but motor mods will have effects as well.

With the way the stock maps are laid out it's pretty easy to check 100% load timing, a lot more difficult to check lower loads. But with some common sense you can do a lot just knowing what peak timing should be.

So lets look at a stock 04.5-07 tune. For this lesson we will leave duration and pressure stock, just messing with timing.

This is a stock duration map with additional labels. What's important to note is that rpms is really load and load is pressure. 100% load is the only one that isn't appox, it's really 100% load. The rest are for reference to an OBDII reader and not necessarily to match the load on the side of the timing/pressure table (which is why anything but 100% is harder to calculate).

When the ECM goes to calculate the desired pulse width (injector open time) it looks at 2 tables. Pressure and duration, with pressure being first. Lets calculate the desired peak timing at 4 rpms, 2000, 2400, 3000, 3200.

So we first reference the pressure table. At 2000 rpms and 100% load the pressure is 20,885 psi. We then go to the duration table (one below with labels). You will notice that 20,885 is not listed on the left column, so now we have to do some math. There is a 23,206 row and a 20,305 row, with 2,901 psi between them. 20,885 is 550 psi above 20,305 and 550/2901 is 19%.

The next thing we look at is duration at 100% load. At 20,305 the duration is 2156us and at 23,206 it's 2005us, with a 151us difference. You will notice that as pressure increases the duration decreases for a given load, this is because the pressure forces the desired fuel out faster.

So we now take our 19% difference from the pressure and multiply it by 151 for 29us difference. We subtract that 29us from 2156us. This gives us a pulse width of 2127us.

So know we know how long the injector is going to be open for we can figure out when to start the injection event. A crankshaft has 360° of rotation, and by using rpm's we can calculate how long it takes to go 1° at any given rpm. Lets start with 2000 rpms. 2000 rpms is 33.33 rotations per second, multiplied by 360° gives us 12,000 deg/sec. A microseconds (us) is 1,000,000th of a second, so 1,000,000 divided by 12,000 gives us 83us per 1° of rotation.

Next you take the total injector open time, 2127us, and divide it by 83. That gives us 25.6° of total injector open time.

Let's say we want a 50:50 split of BTDC/ATDC. Multiply 25.6 by 0.5 and you get 12.8°. Thus we would set our timing at 100% load, 2000 rpms at 12.8°.

"Now lets look at 2400 rpms on the stock tables. Commanded pressure is 22,336. Since 22,336 falls between row's on the duration chart we have to do the math again. 22,336-20,305= 2031. 2031/2901=70% . At 20,305 the duration is 2156us and at 23,206 it's 2005us, with a 151us difference. .70*151= 105us. 2156-105=2051us.

At 2,400 rpms it takes 69us per 1° of rotation. 2051/69=29.7° of injector open time. Same thing 29.7*0.5=14.9° of timing. "



Now lets look at 3,000 rpms. Commanded pressure is 23,207 (same as 23,206), which happens to be one of the columns on the chart so no math is needed. 23,206 and 100% load is 2005us. At 3,000 rpms it takes 56us for 1° of rotation. 2005/56=35.8°. 35.8°*.5= 17.9°.

Now lets look at 3,200 rpms. Commanded pressure is 23,207, which happens to be one of the columns on the chart so no math is needed. 23,206 and 100% load is 2005us. At 3,200 rpms it takes 52us for 1° of rotation. 2005/52=38.5°. 38.5°*.5= 19.3°.

Pay close attention to the 3,000 and 3,200.. the pulse width is the same, but the injector open time is just under 3° longer at 3,200 due to the increased speed of the crankshaft.

So now you are able to calculate what your peak timing should be based on pressure/duration tables and a given rpm. When the load is less than 100% you need to have less timing than 100% load, or you will be injecting all the fuel much sooner and that can lead to increased piston heat and cylinder pressure.

Duration-1.jpg
 
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OH my brain hurts! OK so 2000rpm = 12.8 at 100%. SO +12.8 is max timing at 100% load right? And as load decreases so does the timing heading backwards in numbers towards 0 timing. Where's the tylenol!
 
That 12.8° is a 50:50 split, where you go from there is up to you.

I forgot to add, that a calculator is simply a starting point, not an ending point. You may or may not have to adjust your timing values from what calc gives you. It's a reference and a guide, not a rule.
 
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