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Practical Diesel Tuning: 5. Confirm The Tune On The Road

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5. Confirm The Tune On The Road

21.05

00:00 - So we've got the truck tuned on the dyno, we've made about 400 horsepower to the tyre, we've got things tuned in so it's good balance, timing fuel, boost and we're happy with the power number and the way we've delivered it on the dyno.
00:10 But really the road test is where we're going to find out how the truck drives and is it something that the customer's going to want to buy? So I have the truck pulled out in the parking lot, just going to go ahead and put it in gear and really for my first test I'm just going to cruise around the parking lot.
00:24 And I like to get a feel for how the low speed feel is of the throttle pedal.
00:31 A lot of guys who tune these trucks are going to use them for towing.
00:34 So they're going to want to know if the truck is behaving well at low throttle inputs.
00:41 Especially on these LLYs they have a fairly aggressive throttle table down low and that's where minimal throttle inputs will give you more torque than you're sometimes expecting.
00:51 And with the Allison's really low reverse gear ratio...
01:00 ...it's stuff you wouldn't normally test on a car but believe me, low speed manuevering, if the truck is too touchy on the throttle which is a tendency of a lot of tuners, they ramp in that throttle based injection quantity table and you add fuel too soon to the cal, and if you do that you really feel the truck lurch.
01:16 That's not fun, it's not easy to back a trailer up, it'll definitely spook the wife.
01:23 OK so I'm pretty satisfied with the way the truck behaves at low speed right there.
01:26 I like to start our with gentle right, we already ran the truck hard on the dyno, we don't need to go out on the street and blast it right away.
01:34 So we're running 20, 30% throttle input, maybe a little more than that.
01:37 And I'm feeling the shifts and I'm listening and I'm thinking is the truck shifting the way that it's supposed to, is it shifting the way I intend? I have my datalogger running but of course as I'm driving I'm not going to be glued to my datalogger, it's just there if I need to use it.
01:56 If I have an issue with the truck or I don't like something that it does, I can simply tap one of the number keys, and you'll see it puts a mark in the log right there.
02:04 So if it does something that I really don't like, has some kind of hiccup or extra noise or something like that, I'll put a mark in the log and I'll know to look at that spot later on and I can go ahead and diagnose that.
02:12 So on the Allison, one of the things that we like to really pay attention to on the Duramax Allison setup is the defuel.
02:18 So as the truck shifts, you'll notice that the fuel rate cuts very briefly and defuels the truck so that the transmission can make the shift.
02:26 Normally most drivers are not going to notice this but as you start to add power to the truck, some of the algorithms that work with the defuel are going to pull away more fuel than you thought it should.
02:39 So especially if you ramp power in really soon or you get the truck to come to life sooner than expected that Allison's not expecting that, it's not expecting that torque load so it might pull fuel on you a little sooner and you'll feel that in the shape of a defuel curve that's really excessive or exaggerated.
02:56 I haven't felt anything like that yet.
02:59 I like to get the truck up in high gear and lug it a little bit.
03:03 Just make sure it's coming to life and responding to the throttle pedal.
03:10 So as I push the throttle pedal in high gear here, well I'm up in sixth gear, this truck has a six speed conversion so it's in sixth gear.
03:17 Normally it'd be in fifth.
03:20 But as it's in sixth gear I'm just feeling, is the truck picking up as I'm feeding it throttle? Is there any point where I'm feeding it throttle and the truck isn't responding? Got a downshift there so I want smooth power trajectory, as I feed the truck throttle, I want a predictable increase in output.
03:41 If I push the truck so far and then I push it a little further and it doesn't go, it should have called for a downshift or possibly we have a mass airflow limited fuelling issue right there which would mean I want to go on my mass airflow limited fuelling table and check that out.
03:56 Come back on the throttle.
04:01 Nice firm but smooth shifts.
04:06 Got a lock up, everything feels good.
04:11 And I'm at about 50% or 60% of the throttle right there.
04:17 And I'm just continuing to feed the truck more and more pedal to see, is it behaving, does it appreciate that power? For those of you who understand early Duramax's and Allisons know that at a certain power level the trans is not happy, we don't want to push the truck so far that the trans is going to hiccup really bad and hurt itself, we want to be paying attention to how happy the transmission is here, remember we built this tune with the stock transmission in mind.
04:41 As I get on the country roads, I like to get the truck in high gear and locked up and I like to look in the rear view mirror and see as I flash the throttle, so as I flinch at the throttle like this, call for a downshift, do I see any smoke? And I got a puff of smoke there.
05:04 And when I'm logging the truck I can look at the cylinder air, the dynamic cylinder air and I can look at RPM and I can say OK at that point I'm getting a little bit too much smoke.
05:17 Little bit of a bark there, bit of a harsh shift.
05:21 That's not unnatural so when you first tune the truck you're going to have some of those harsh shifts, you're going to have to push through them.
05:28 I like to bring it up slow so I can feel those and I don't have to push the truck super hard through those but expect those.
05:33 You have to go through about four or five of those, that same shift before it'll learn itself out.
05:37 It's nothing to be scared of.
05:39 So I have the truck up in high gear again here and I have my finger on the note key, what I'm going to do is flinch the throttle again for that downshift and that'll give me a note in the log, look at that RPM and that cylinder air and maybe take a little bit of mm³ out of the tune there, in the mass airflow limited fuelling table.
05:56 And that'll clean that part of the tune up just a little bit.
06:01 Some guys are OK with a little smoke right there, some aren't.
06:04 I prefer to get the truck as smoke free as possible.
06:07 So I'll continue to dial that mass airflow limited fuelling table back as I can.
06:12 So we're at a spot where there's no cars behind us here.
06:15 I'm going to slow down and I'm going to let the truck go through a 3/4 throttle shift pattern and see if I can get it to learn out some of those harsher shifts.
06:24 Getting the truck to learn out those harsher shifts is a really good thing to do before you give it back to the customer.
06:39 If the customer feels those shifts, they're not going to appreciate it as much as you are.
06:41 You'll feel them clean up as we go through.
06:49 So there's one.
06:55 I'll come to a stop again.
07:00 And this time I also have a CTS2 over here which is showing me my exhaust gas temperatures.
07:09 You can feel it, my exhaust gas temperature is 1178, 1192, 1202.
07:17 1230 at 80 miles an hour.
07:19 So I'm getting a sense of how hard the truck is working.
07:21 Again 1200 degrees exhaust gas temperatures is not hard at all.
07:24 So we're really not pushing the truck into its danger zone as far as the engine or the turbocharging system's concerned.
07:30 But I like to know that, I like to have the EGT sensor hooked up on the truck and look at that.
07:40 The shifts are starting to feel better, I like that.
07:43 We'll do one more up through the gears here.
08:04 A little bit firm.
08:09 So the Allison's going to want to see as it goes through its learning regimen, key on and key off cycles.
08:13 So if the truck is continuing to shift a little hard for you, pull over and shut the truck off, turn it back, wait three or five minutes, turn the truck back on and it'll come back to life and it'll go through that relearn cycle again.
08:27 Usually after four key cycles it should be good.
08:30 If the truck is continuing the shift firm or shift extra hard or tie up, bark the tyres, do stuff that you don't like, look for something in your tune as far as shift quality goes.
08:39 Those situations are normally in the base torque or torque limited injection quantity tables.
08:46 We haven't modified those very much, this is a very basic tune.
08:49 So if any relearning, I would expect the truck to relearn, and shift issues I would expect the truck to relearn out.
08:56 So I'm back up on the highway, I'm in high gear.
08:58 I'm going to continue to feed the truck some throttle, just 'til it gets to downshift.
09:03 And just see is there any opportunity for a little bit more fuel? On the MAF limited injection table.
09:09 I have pretty good response and the truck is clean, I'm looking at the tail pipe and I'm seeing the truck is pretty clean right there so as I tease the throttle I'm going to make notes.
09:19 So I'm going to note two...
09:25 and two, OK and as I press that number two key I'm going to see those notes in the log and that's a trigger to me to add more fuelling on the mass airflow limited injection quantity tables.
09:36 Now if you watched me make the timing table in this truck, you know that we didn't get very aggressive with it.
09:40 We didn't really change the timing at anything other than full load.
09:42 However if you took advantage of editing the timing table, somewhere in the mid range or where you're operating the truck during normal cruise, odds are you're going to hear that extra timing.
09:52 Now part of the engineer's strategy for tuning timing and fuel pressure is noise vibration, harshness, dampening.
09:58 So keeping the truck quiet, that's part of the reason of having a common rail injection system so you can run lower pressures and dynamic timing.
10:06 Need to be listening for that, so if you're adding three, four, five degrees of timing at cruise because you're working with a bigger injector truck, or trying to clean something up.
10:16 A lot of times a bigger injector truck likes a little bit of extra timing and you can kind of tease them up a little bit.
10:21 But you're going to hear that so you want to listen, are you pushing it too far, is this something the customer's going to be annoyed by? I'm taking the truck on a 12 minute drive right now, but a lot of these guys are going to drive their trucks for three, four, five hours.
10:34 And if you have a truck that's excessively clattery or noisy or sounds a lot different than it does when the truck was given to you, expect to hear about it from the customer.
10:45 The power deliver on this truck is really smooth and you'll feel that with stock turbo trucks, very smooth power delivery.
10:51 What we're looking for is a predictable power output at a given throttle.
10:56 So you want to keep the throttle at a certain spot, you should never really feel the truck accelerate harder or softer as you keep the throttle at that one certain spot.
11:05 If the truck gets to a certain point and all of a sudden takes off, you've got some work to do on your transient there or your throttle based injection quantity table isn't mapped out quite right.
11:14 OK so I've made a few notes in my log file of areas that I want to give attention to as far as getting a little more fuel in one area and cutting a little bit of fuel out on that downshift.
11:23 I also want to back that low speed throttle down a little bit, it's responsive and it's controllable but it can be a little bit softer down low just for the ability to back the vehicle up.
11:35 So if I click up at the top here, the top of the screen to magnifying glass all, that'll condense the log file into the whole log in one screen.
11:42 And then I can really see where my notes are. that's these dotted lines.
11:48 And I can zoom to these dotted lines and check things out.
11:52 So here's that downshift, and it's really nice, you can see me go from 1400 RPM to 2100 RPM.
11:59 And that dynamic cylinder air goes from 1.0 to 1.75 and that's where the truck really starts to fuel hard.
12:06 And you can see that in the yellow line down at the bottom here.
12:10 That's MBPW pulse width, so we go from 1027 up to 1975 pulse width.
12:17 So we need a little bit of dampening right there and you can see that happen because the boost comes up relatively quickly.
12:24 So we'll open the tune file up.
12:29 And so the area of the tune file that controls that is called the MAF limited injection quantity table.
12:34 And you can see the issue with this table here is that the factory table has a really steep gradient from 1.2 to 1.8.
12:41 And that's really where we're transitioning from 1.0 to 1.9 So what I can do is I can ease that transition a little bit.
12:58 And I can do that by taking these cells down here and I'll just turn the table a little bit, turn that table and you can see a little better.
13:09 If I interpolate between those cells you can see it smooths those out a little bit and what that's going to do is smooth the way that the fuel comes in as you roll into the throttle right there.
13:22 Now really we're not going to see 120mm³ so I might as well do 110, that'll make sure we get full fuelling...
13:35 ...all the way out.
13:40 And you know I really don't need it at 2800 plus, it's really in the lower RPM.
13:44 So what I'm going to do is, to make sure I don't lose full fuel up top, I'm going to do that.
14:01 Just kind of ramp that in a little bit.
14:04 It might take a few iterations to get this table right but that should solve it a little bit.
14:10 OK and then the other situation where we put a note was at sixth gear when I kind of hit the throttle and I didn't see any smoke whatsoever and the truck didn't really come to life as quickly as I was hoping.
14:21 So that was my number two note and that was all the way towards the end of the log file, remember there was three of those.
14:27 So I go over here and I'm looking at 1568 RPM at about 1.0 grams of dynamic cylinder air, again 1600 RPM, 1.0 grams 99 cylinder air.
14:41 97 cylinder air.
14:43 So we're kind of seeing that trend there that we're right about 1.0 on the dynamic cylinder air and somewhere in this range here.
14:57 So what I could do is add a little bit of fuel right there and what that's going to allow is a little bit of extra fuel at that airflow.
15:11 I'll type five, plus.
15:15 And then I might smooth that in just a little bit.
15:23 I'm going to show you something on this table because we have an EGR on and an EGR off table.
15:27 So what I want to do is to make the same changes to the EGR on table as the EGR off table.
15:32 Except those tables are different base so what I want to do is apply the same difference.
15:36 So what I'm going to do is show you a little trick here.
15:39 I'm going to control Z all the way back to stock.
15:46 Copy the stock table and then shift control Z all the way back in.
15:52 Then I'm going to paste and subtract.
15:59 Then I'm going to copy.
16:06 Then I'm going to paste and add those changes into the EGR on table.
16:14 So that'll make similar changes to the EGR on table.
16:17 Now I talked about the low speed control and the low speed control is really in the throttle base injection quantity.
16:22 What I'm talking about here is low RPM, so maybe up to 1800 RPM and up to 30 or 40% on the throttle.
16:34 You can see in there how it kind of ramps in.
16:36 So if I want to soften up that hit, make the truck a little bit less responsive right off idle, I can soften these two rows.
16:45 And again your approach to this might vary a little bit but the goal is the same thing.
16:48 Soften the first two rows and then smooth things in.
16:53 So minus four, five, plus.
16:58 And then it'll smooth it in like that.
17:04 Very good OK so we've softened up our low speed throttle base injection quantity table, that should make the truck a little bit more manageable right off idle.
17:10 I'm going to save it.
17:13 And make this version 1.3.
17:18 And I'll go ahead and flash the tune file in and then drive it again.
17:30 So while we're flashing here I just want to give one more little spiel about shift quality.
17:33 Every time you reflash the TCM or reflash the ECM with a tune that has different torque loads, you're going to notice the truck will relearn the shift quality and shift parameters.
17:44 So expect the truck to shift a little goofy the first time after a new TCM or a new ECM file.
17:50 Again as we go through those key cycles and shift cycles, it's good to go three or four shifts of the same gear and the same high load every time you take it out for that first drive.
17:58 And then go through at least four key cycles before giving the truck back to the customer, especially if the transmission's not behaving.
18:05 Of course if it's shifting great, you're good to give it back right.
18:08 You want to make sure the truck is shifting good, make sure it's performing the way that you would expect to get it back before you hand it back to a customer.
18:18 OK so I've finished my reflash, my tune update and I'm just going to cruise around the parking lot nice and slow, get a feel for the throttle.
18:27 It's subtle but it's a little bit smoother.
18:43 You know in stop and go traffic there's nothing more annoying than a truck that lurches every time you tap the throttle.
18:49 This may seem like an insignificant piece of tuning but trust me, you'll appreciate it when you're stuck driving the thing.
18:56 So we'll get the truck up into road gear again and start flashing the throttle, pumping the throttle and seeing how the smoke output is and seeing how the response feels.
19:06 Remember we're looking for a little bit more response in sixth gear and then we're looking for a little bit less smoke as we transition from sixth down to fifth and fourth.
19:22 You could hear that shift but it wasn't as bad as the last time.
19:25 That's kind of how it is with these things, every time you shut if off, start it, run it again, go through a few more shifts, it gets better and better.
19:33 So we're up in high gear, I'm teasing the throttle a little bit, I can see just an ever so small wisp of smoke now.
19:43 So I added five mm³ to the MAF limited injection quantity table in that lug area right there.
19:49 And about one gram of cylinder air and 1500, 1600, 1700 RPM.
19:57 I don't know, that feels just about perfect, honestly the truck's got great response right there.
20:03 I really like that.
20:07 So as I continue to drive here I'm going to go ahead and touch the throttle just a little bit more to try and get it to downshift.
20:14 Take off, ooh and there was no smoke on that downshift.
20:20 You could feel it hesitated just a slight bit before it took off.
20:24 I may have taken a little bit too much out.
20:27 But it's. nice to be able to see which direction we're going.
20:30 And this is just a process of iteration.
20:33 Got to put miles on the truck, you've got to road test it.
20:35 If you're going to tune the customer's truck and you're going to take it out for 20 minutes and expect to get it perfect, it's probably not going to happen.
20:41 Best thing to do, either borrow the truck for a week or buy a truck and work on the cals so that you can get it just the way you want it.