Practical Diesel Tuning: 4. Optimise Tune
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4. Optimise Tune
30.21
| 00:00 | - We have our base tune built and we're ready to do our dyno work. |
| 00:03 | So the first thing I'm going to do since I have the stock file in the truck still is going ahead and run the truck on the dyno and get a baseline on the dyno so I can make sure the truck's in good mechanical shape. |
| 00:12 | So what I'm going to do is pull up my log file here, I'm going to use the EFI Live scan tool to log the truck. |
| 00:19 | I just want to go through a few of the PIDs that I'm going to look at as I run the truck on the base file and we'll use these same PIDs as we run the truck on the modified file. |
| 00:25 | I just want to talk about the PIDs I'm going to look at and briefly why. |
| 00:30 | RPM, engine speed, important. |
| 00:34 | Throttle position, this will tell us when we're under full load. |
| 00:37 | Boost pressure, give me an idea how hard the turbocharger's working. |
| 00:40 | Fuel rate calculated, that's going to tell me where I'm at on my maps. |
| 00:44 | So if I want to make an adjustment to a certain fuel rate mm³, this PID will tell me where I should be there. |
| 00:50 | Main injection timing, one of the ingredients of making power, make sure we're getting good timing, make sure nothing's pulling out. |
| 00:56 | Cylinder air, remember we had our aneroid fuel control, our MAF limited fuelling, that's dictated by cylinder air. |
| 01:03 | If I want to look and see if I'm being limited, I need to know my axis on cylinder air. |
| 01:08 | Main pulse width, one of the major ingredients in making power. |
| 01:13 | MAF flow, that's going to give us cylinder air. |
| 01:16 | Vehicle speed. |
| 01:17 | Turbocharger vane position, this is good on the LLY because it's going to let us know how hard the turbocharger's working. |
| 01:24 | If we see the turbo vane squeezing down really tight, that might be an indicator that we have a boost leak or we have some turbocharging issue where the turbocharger has to work harder than expected. |
| 01:33 | So we'll watch the turbocharger vane position stock and then also see what it's doing on a mod file. |
| 01:38 | MAP pressure ties into boost, DSP we're not going to be using yet. |
| 01:42 | FRPACOM, that is our regulator on the CP3 pump so the lower that number is the harder that regulator's working. |
| 01:51 | If we have any fuel pressure issues or fuel pressure discrepancies, we're going to look at that FRPACOM PID and see how low it is. |
| 01:58 | I would expect that to be somewhere in the 800 to 900 range, maybe 1000 at full load on one of these stock trucks. |
| 02:04 | If it starts to go towards zero then we know that we're out of fuel. |
| 02:07 | And fuel rail pressure and desired fuel rail pressure. |
| 02:10 | Any discrepancy between desired fuel rail and actual fuel rail is going to indicate that there's maybe a maintenance issue or some mechanical issue with the truck and we're going to stop there before we proceed with the tune. |
| 02:20 | Alright let's get it fired up and running on the dyno. |
| 02:23 | So we're scanning, our log file looks good. |
| 02:25 | I'm running a Mustang dyno, I have a test build for this year truck and for this power level roughly, it's an eight second test, it starts at 2000 RPM and runs to 3200 RPM. |
| 02:36 | What I'm going to do is bring the truck against the brake at 2000 RPM, flat foot it, let it make full power and then release the brake and let it run for eight seconds to 3200 RPM where the test will end. |
| 02:46 | This is all done in fourth gear and I do that by running over drive off and tow haul engaged. |
| 02:52 | I'll start the test. |
| 02:59 | Floor the truck, begin my test. |
| 03:11 | We'll let the truck come back down to zero miles an hour, go ahead and stop the log file. |
| 03:17 | When you save the log, be sure to be clear on what the file was and what the test procedure was. |
| 03:24 | So I'll do LLY baseline stock 2000 - 3200. |
| 03:36 | I like to add the horsepower and torque in there as well. |
| 03:39 | So for that I'll pull up the graph. |
| 03:41 | So I have my dyno graph pulled up, looks like we made 295 rear wheel horsepower and 576 foot pounds of torque. |
| 03:48 | So I'm going to go ahead and label my test, LLY stock baseline one, 295 horsepower, 576 torque. |
| 03:57 | Now that I know those numbers, I'm going to put them on my log file as well. |
| 04:02 | 295, 576, save. |
| 04:07 | Those are about the numbers I would expect on this truck, I was expecting between 290 and 300 so 295 works out really nice. |
| 04:14 | Now let's go through and find the dyno run. |
| 04:21 | It's easy to find the dyno run because you can look for the area in the log that has throttle position at 100%. |
| 04:27 | So there's the start of our run at 2071 RPM and you can see we stayed on the brake from here to here where our RPM was constant and then our test starts here. |
| 04:37 | And runs out to about 3300 RPM we stopped. |
| 04:45 | So as I'm looking through the log file, the things I'm going to be looking for are, I'm going to start with fuel rate. |
| 04:50 | So I'm going to look at the fuel rate calculated and that's this blue line here, and I want to see what my maximum fuel rate calculated was because if you remember I built my tune file on a tune that was expected to make about 95 mm³. |
| 05:04 | 95 mm³ was the maximum command in the stock tune, remember we added a little bit to that so that we could get the rest of the stock fuel out of it before we modified the pulse width table. |
| 05:14 | So I'm going to say OK, is that a legitimate starting point? So look through here, say OK 94, 95, wow right on, OK. |
| 05:23 | So at peak power, 3000 RPM we're at 94.4, close enough to 95 for me. |
| 05:31 | I like that. |
| 05:35 | OK MAP psi 34.4 so I'm looking, is there airflow, what do we have for air? Looks like about 20 pounds of boost, just short of 20 pounds of boost, 19.5 pounds of boost. |
| 05:48 | Next line I want to draw you attention to is the green line and that's the vane position. |
| 05:53 | As you're tuning these LLY, LBZ, LMM, anything with a variable geometry turbocharger you're going to want to get a handle for what the turbocharger's doing. |
| 06:00 | How hard is it working? The only way to now this really is to do it by experience but luckily you have me here, I can tell you, running at full tilt, it's nice to see this thing between 40 and zero I really like to see it. |
| 06:14 | If I see the vanes go past 50 at full load, it means the turbocharger's working really hard and I expect high drive pressures. |
| 06:20 | This truck's not equipped with a drive pressure gauge but if it were we'd see drive pressures really start to climb as full load, the vanes close past 50%. |
| 06:30 | So vanes start up higher here around 44, you can see when we're loading against the brake, we're in the 60s. |
| 06:36 | 2000 RPM you do need that tighter vane position. |
| 06:40 | But as I release the brake and the truck runs out, you can see the vanes start to open and I'm going to use 3000 RPM as kind of my peak power RPM number so as I'm making comparisons we'll look at 3000 RPM. |
| 06:52 | And you can see vane position's at 38, 35, so we're right in there. |
| 06:58 | Nice spot to be. |
| 07:01 | Timing for those keeping track, 10 degrees of timing at full tilt to 3000 RPM. |
| 07:06 | Pulse width, so remember pulse width is how long the injector's on for, 1479. |
| 07:11 | As we add pulse width to add torque to add horsepower, we're going to want to check against our desired pulse width and make sure that we're getting the pulse width we command. |
| 07:21 | So we'll just keep track of that 1498, 1479. |
| 07:25 | And then I'm going to draw your attention to these purple and green lines. |
| 07:29 | And the way that they're overlaid on each other is beautiful, that's exactly what we want to see, we want to see desired rail pressure, right in line with actual rail pressure. |
| 07:36 | 22241, 22481, it's OK that they dance a little bit like that but if we see major deviations, you know if you saw down here in the 17, 18, 14,000 psi range, that would be an indication that we have a CP3 issue or a fuel leak or something that we need to address before we continue to tune the truck. |
| 07:55 | So all indications are that the factory truck is in good shape, it made the power number we expected, turbocharger's working about as hard as we expected, the fuel system's keeping up and we're seeing all the PIDs, show us exactly what we want to see. |
| 08:07 | So our next step here is to flash the modified file in and get our baseline dyno number on that and then we can optimise from there. |
| 08:13 | To flash the mod file in I'm going to turn the key to the run position, I'm going to select calibration flash. |
| 08:27 | So as we go ahead and run the modified file I'm going to start this log again and I'm going to start the dyno. |
| 08:32 | Remember as you're running any modified tune files, anything with higher horsepower, if you feel the truck stumble or do anything you don't like, get out of the throttle, let off, pop the truck in neutral. |
| 08:41 | Better to be safe than sorry, you don't want to push the thing hard if it doesn't feel right. |
| 08:45 | Last thing you want to do is fail a customer's vehicle, injure a transmission or a head gasket or have a major fuel system failure, anything like that, if you don't have to. |
| 08:56 | If something doesn't feel right, just back out of it slowly. |
| 09:17 | I'm going to go ahead and save my dyno graph based on the power level we've made and the tune number. |
| 09:23 | So this is mod version 1.0 and it made 373 horsepower, 766 foot pounds. |
| 09:35 | So we started with 295 rear wheel horsepower, 576 foot pounds, remember we wanted just about 100 extra rear wheel horsepower 'cause we want to keep the truck just on the cusp of transmission safe so we're looking for that 100 rear wheel horsepower. |
| 09:47 | So 295, we're looking for 395. |
| 09:50 | With this base tune file we're at 377 rear wheel horsepower. |
| 09:54 | So let's take a look through the log file and see how hard the truck's working, see if it seems to like where we're at and let's talk about adding some extra fuel, maybe making a little more power. |
| 10:02 | So I have the log file open, first thing I'm going to look at is main injection fuel flow. |
| 10:07 | Remember I'm looking for 100 mm³ or more, that's going to put us at the bottom of our pulse width table, so I'm looking at this blue line here and the blue line dips briefly to 98, that's not something I'm majorly concerned about. |
| 10:19 | And then at 3000 RPM, fuel rate calculated is 108 so we're easily at the maximum commanded fuel flow rate. |
| 10:27 | So next thing I'm going to look at is pulse width, what did we get? I see 1852 down here and that's at 3000 RPM, remember for discussion's sake we're at 3000 RPM. |
| 10:37 | If you look at the dyno graph, peak power is just past 3000 RPM, 3050, right around there. |
| 10:43 | So 1869 microseconds, 1869 microseconds, timing's at 13 degrees, let's look at the fuel pressure. |
| 10:56 | So remember we expect those lines to overlay right on top of each other, desired should be actual. |
| 11:00 | And we're desiring 2361 and our actual is Any time you're within 1000 psi commanded in a situation like this, I would call that you're doing pretty well especially with a stock pump truck. |
| 11:14 | As you start adding a lot of power to these things, they don't necessarily track as well so the more power we add the more I would say it's OK to see a little bit of discrepancy. |
| 11:24 | But this truck looks solid, 23,000, 23,000. |
| 11:27 | So we're right there. |
| 11:30 | Let's look at our turbocharger now. |
| 11:35 | Oh that's interesting. |
| 11:37 | OK so our turbocharger is making 42 pounds MAP, 37 psi, so if we take that 42 pounds and subtract our 14, that gives us about 28 pounds of boost. |
| 11:54 | And the thing that I'm noticing that I'm hoping you're noticing is this green line is higher than I said I think it should be. |
| 11:59 | So as we started the test we left at about 50 vane position, that's OK. |
| 12:04 | As we've run up through the test I would expect the vane position to come down some. |
| 12:07 | Really what vane position does is continue to climb. |
| 12:11 | So we're at 50, 60, 54, 55, it's OK to see those oscillations, it's on a PID loop, it's going to try and maintain desired boost, the vanes are always going to come up and down a little bit. |
| 12:22 | So that movement's normal but in general the vane position is higher than I'd like to see. |
| 12:28 | I think we could easily make this power by taking some boost out of the truck. |
| 12:31 | If we wanted to confirm that, we could look at the air/fuel ratio gauge. |
| 12:34 | I don't have one hooked up on this truck, you might not have one hooked up so I'm going to leave that gauge out of this but I will tell you that with the vanes closed that much, I guarantee you the truck is clean and the air/fuel ratio's in check. |
| 12:47 | So the leverage that we have to make extra power here would be, we could mess with the timing a little bit, we could add rail pressure, we could add pulse width or subtract if you want to make less power. |
| 12:58 | But seeing as how we're looking for just about an extra 20 horsepower I'm going to do the math on that. |
| 13:03 | So I'm going to say we're looking for 395, we're at 373 right now. |
| 13:06 | So I do the division on that. |
| 13:17 | Looks like we're about 5.8% off. |
| 13:19 | So I'm going to try and avoid making multiple changes at once, I'm going to try and get us to that power level first and then make some slight tweaks. |
| 13:26 | So first we'll try and get to that power level by adjusting the fuel rate. |
| 13:31 | The way we're going to do that is to go into the fuel injection table, main injection pulse table. |
| 13:39 | Remember we modified these to get that extra fuel flow. |
| 13:43 | I'm going to grab those same rows and I'm going to adjust those by 5.8%. |
| 13:53 | And really that small of a change you probably don't need to blend. |
| 13:59 | Control C to copy, I'm going to find my pilot off. |
| 14:04 | Control V to paste. |
| 14:07 | So there I have some extra pulse width, extra fuel. |
| 14:13 | What I'm going to do is look at my 160 mPa, I'm going to say 1900 microseconds. |
| 14:19 | So on this run at 373 horsepower we were at 1860 microseconds, I'm going to bump this up to 1950 microseconds, I can see what that gets us. |
| 14:33 | We'll increment our revision one. |
| 14:39 | Resave it, a little trick if you want to be clever, is you can add your horsepower and torque numbers to the previous tune so you can see what you changed along the way. |
| 14:56 | While I'm flashing the truck I want to talk about the boost a little bit. |
| 14:59 | So we saw that our vane position was higher than expected. |
| 15:01 | Between 50 and 60 vane position when we're expecting somewhere in the 35 to 45 range. |
| 15:09 | Might be wondering why I didn't do anything to change the boost while I had the option. |
| 15:13 | The reason is because we added fuel, so as I add fuel via adding microseconds, adding fuel rate, the exhaust system's going to have more energy in it. |
| 15:23 | Remember the exhaust system's on a PID loop so it's going to change vane position to achieve the desired boost. |
| 15:30 | As it sees that extra energy in the exhaust system, there's a possibility that it's going to change the vane position, probably lower to achieve the desired boost that we're looking for. |
| 15:41 | So really what I want to is get us to that power level first and then if I don't like the vane position, then I can pull some of that desired boost out. |
| 15:50 | We've got our revised tune loaded in, now we're going to make one more pass on the dyno and see if that netted us the extra power. |
| 16:12 | We've completed that run, so I'm going to go ahead and save the log file, my numbers on that pass were 390 and 823 foot pounds. |
| 16:23 | Save and I have titled the dyno graph as well. |
| 16:29 | I haven't gone over the dyno graph that much, really the dyno graph looks very similar to the stock dyno graph, just with the amplitude higher and that's what we're expecting. |
| 16:40 | So our peak power on these trucks is typically in the 2950 to 3150 range. |
| 16:51 | Can see we're right around 3100 RPM. |
| 16:53 | I can add a little bit to the ceiling here, 405 just so we can get a clear picture. |
| 17:05 | So pretty good flat power right there. |
| 17:07 | OK so first thing's first right, fuel rate, do we make fuel rate. |
| 17:11 | Yes our blue line looks good, we're over 100 OK I like that. |
| 17:14 | Pulse width, remember we're shooting for 1950, let's see what we've got. |
| 17:20 | 1999, at 3000 we're right at 2012 on the pulse width, interesting. |
| 17:29 | Fuel rail pressure is down slightly, 22700 compared to 23061. |
| 17:34 | And I'll bring your attention to the tune file here just to show you something. |
| 17:39 | So as fuel rail pressure actual drops, the pulse width or injector on time is going to come up. |
| 17:48 | And that's just a function of the truck trying to get its target fuel mass or fuel volume. |
| 17:53 | So as the truck goes from 160 mPa at 1952 towards that 22,000, 20,000, 21,000, it's going to gain microseconds. |
| 18:08 | Or it's going to stay open longer in order to try and get that same fuel quantity. |
| 18:13 | So when we see that slight adjustment in pulse width, that's tracked because of actual fuel rail pressure fluctuating slightly. |
| 18:22 | Normal. |
| 18:23 | Fuel rail pressure, 22,800, I mean you can see them dancing a little bit more than we saw on the stock file but all in all tracking very well. |
| 18:31 | I'll draw your attention while we're here to the FRPACOM and that is how hard the pump is working. |
| 18:37 | So remember as that goes towards zero it tells us the pump's working very hard. |
| 18:40 | That's at 987 and the bottom that we see i What that tells us is that the CP3's keeping up very well on fuel, the truck could easily make more power if we wanted it to. |
| 18:50 | What I will tell you is this truck's transmission probably isn't going to be happy if we push it any further. |
| 18:55 | An interesting thing on this truck is that we ended up with more pulse width than we had anticipated in the timing curve. |
| 19:01 | So what I'd like to do is go in and add a little bit extra timing just to balance that pulse width back a little bit. |
| 19:06 | So I want to start to straddle top dead centre with my injection pulse width and because we continue to add to pulse width, on the power stroke I need to advance the timing a little bit to get that back towards normal. |
| 19:17 | The next thing I want to do is adjust boost a little bit. |
| 19:20 | So for the power level we're at, our vane position's pretty aggressive still. |
| 19:24 | You can see down low here we're at 50 vane position, comes in to 55, 58. |
| 19:31 | So I'm going to make a couple of modifications to the desired boost. |
| 19:35 | I'm just going to pull a couple of psi out of our desired boost and I'm going to add a couple of degrees of timing to the tune, I'll show you how I do that and then we'll run it one more time before taking it out on the street. |
| 19:45 | OK so I'm in my timing table and I'm going to grab just the full load higher RPM section of the timing table and modify it. |
| 19:53 | Highlight it, type in three degrees here, add, and that's going to take us from about 13 degrees at 3000 RPM up in that 16.5, call it 16 degrees at full. |
| 20:09 | We still have some room on the table here. |
| 20:11 | If you want to use a timing calculator to help you, that's fine, if you want to just increment two degrees at a time until the truck doesn't pick up any more power, that's your prerogative as well. |
| 20:21 | As long as you're nice and slow and creep up on the thing, you're doing OK. |
| 20:25 | What I want to caution you to is adding five, six, seven degrees of advance at a time without testing it on the dyno or driving it. |
| 20:32 | Some things that I look for if I don't have a dyno so if I'm driving the truck on the street and I want to find out, do I have enough timing in it. |
| 20:40 | I want to look at my exhaust gas temperatures, so very high exhaust gas temperatures are going to indicate that my truck doesn't have enough, possibly does not have enough timing. |
| 20:49 | It could have a lot of fuel in it, it could have not enough air but if everything else is where I think it should be and the truck is running hot, usually adding more timing to it is going to cool off the exhaust gas temperatures. |
| 21:00 | Typically on the dyno, you can creep up in the truck and you'll find a rate where it makes the same power if you add timing to it. |
| 21:07 | From there, back it down two degrees, always err on the safe side with timing. |
| 21:11 | We'll put three degrees of advance in and with 2000 microseconds at full I will tell you that 20 degrees will be perfectly acceptable. |
| 21:19 | We'll err 2.5 degrees lower than that just to see what it does. |
| 21:24 | And then on the boost side, we're going to come in here at full boost, or at full load. |
| 21:36 | And subtract two pounds of boost. |
| 21:44 | And I'm also going to smooth that in. |
| 21:56 | I'll copy those, control C, and I will paste them into the EGR on table. |
| 22:04 | And those were at 1200 RPM and 70 mm³. |
| 22:09 | 1200 RPM and 70 mm³, control V. |
| 22:16 | Save as 1.2. |
| 22:18 | You may be curious why I'm pulling boost out, shouldn't the truck make more power if it has more boost? There's a point of diminishing return on that. |
| 22:25 | If we run the turbocharger faster than it needs to be, let's say our air/fuel ratio is 19.5, 20:1 which it probably is right now. |
| 22:32 | If I run more boost it's going to create choke in the exhaust and that choke is going to result in higher drive pressure and the higher the drive pressure ratio to boost, the less power we're going to make. |
| 22:42 | It's also to the long term detriment of the turbocharger that you can overspeed the turbocharger and cause premature failure. |
| 22:49 | So we want to use just as much air as we need in order to keep the turbocharger happy long term and keep the truck making the power we expect. |
| 22:55 | Now that I have this tune built I'm going to save it as version 1.2 which I just did and then flash it on and we'll dyno the truck once more. |
| 23:17 | Alright so on that tune file we got kind of a happy, a little easter egg there. |
| 23:22 | We got 410 and 872. |
| 23:25 | So remember we were shooting for 395. |
| 23:27 | That 410 I think was a result of the extra timing, so it really liked that three degrees of timing and my suspicion would be that it would like even more timing. |
| 23:36 | So what we can do is back off the pulse width a little bit and continue to back off the boost and I'll show you why in just a second here. |
| 23:42 | So as we look at the log file, again the basics right, so we look at fuel rate calculated, make sure we've got our 100 mm³. |
| 23:49 | Good we're there, OK our pulse width. |
| 23:52 | 2900, 3000 RPM, 1993, same as we were last time so everything's pretty much the same as we were last time, our fuel pressure's the same as we were last time. |
| 24:03 | That stuff tracks really nice, the only thing that really changed was our timing which is 16 degrees and our boost which came down those two pounds that I requested. |
| 24:13 | So pulled two pounds of boost out of it and now our vane position is back in line. |
| 24:18 | So our vane position's at 47.5. |
| 24:21 | Remember I said before 35 to 45 is where I'd like to see it. |
| 24:24 | 47.5 OK we can see we toggle kind of between 45, 45, start to fall off towards the end of the run there. |
| 24:34 | So we're really in the 45 to 50 range, I would say 45, we're on the high side of what I think is appropriate but that's OK. |
| 24:40 | The truck will be nice and clean. |
| 24:45 | Main injection timing, 17 degrees. |
| 24:47 | So remember before we were mid 13s, we had three degrees, we're at 17 degrees now. |
| 24:53 | The truck picked up almost 20 rear wheel horsepower. |
| 24:56 | So it went from 389. whatever, 390, up to 410 rear wheel horsepower. |
| 25:01 | That's a nice jump so I really like that timing. |
| 25:04 | So if we really want to target that 395, we can pull some pulse width back out of it and use less fuel, more efficiently with the extra timing and make that extra power. |
| 25:14 | So as I'm going to continue to refine this truck, what I'm going to do is continue to pull that fuel back creep up on timing, pull that fuel back, creep up on timing. |
| 25:22 | I might pull another pounds of boost out of it just to get the vanes down in that 40 range but by continuing those iterations, I'll make the truck run as efficiently as it can possibly run while making the horsepower target that I want to make. |
| 25:35 | While we're on the topic of building our base tune, I want to cover a few little pieces that you might run into along the way if you have customers come in with modified trucks. |
| 25:42 | One of them is differences in intake setups, so the factory intake is calibrated to the factory mass airflow sensor. |
| 25:49 | If they've modified the factory intake, there's a good chance that the mass airflow readings are going to be off. |
| 25:54 | This can affect you in a number of ways. |
| 25:56 | You can have a truck that's unresponsive, and is unwilling to fuel because it does not read the air correctly that's coming into the engine. |
| 26:04 | Or you can have a truck that is over responsive. |
| 26:07 | Believe it or not, some of the aftermarket intakes are smaller than factory which artificially raised the mass airflow rate which artificially allow more fuel in the engine and run the truck smokier, more responsive, of course less peak power potential because the intake is smaller. |
| 26:24 | But nonetheless, they're out there. |
| 26:26 | If the intake is larger than stock, usually the best thing that you can do is modify the mass airflow scaling. |
| 26:32 | And I'll show you that here. |
| 26:37 | This is the mass airflow sensor voltage, zero to five volts. |
| 26:41 | And the values are in pounds per minute of airflow. |
| 26:46 | If the mass airflow, if the stock mass airflow sensor opening is four inches and your modified mass airflow sensor opening is five inches, you're going to want to do the math on that. |
| 26:59 | You're looking at the area of the cross section, remember that, not the diamer, not the radius, you're looking at the area. |
| 27:05 | So going from four inches to five inches is actually a 56% larger cross section. |
| 27:12 | So good place to start is take this whole scale and add 56%. |
| 27:20 | You'll notice down here at the bottom you're going to max out slightly but that'll put you in a good spot to start. |
| 27:26 | If you need to make small adjustments based on smoke control, that sort of thing, you'll make those in the max injected fuel quantity based on mass airflow. |
| 27:38 | So these tables work together with the mass airflow rate. |
| 27:41 | The more mass airflow that the truck reads, will show up here in dynamic cylinder air, based on RPM and that mass airflow reading will in turn limit or unlimit the amount of fuel the truck's able to make. |
| 27:55 | Based on how much air's coming into the engine and what RPM, that's the fuel limiter, so 65 mm³ in this case at 2800 RPM and 0.9 grams per cylinder. |
| 28:06 | I like to avoid modifying the mass airflow rate table to control smoke, I like to use this table to control smoke. |
| 28:13 | This MAF limited injection quantity. |
| 28:15 | I like to use the mass airflow rate table when it's warranted because the intake is different. |
| 28:20 | OK second thing is larger injectors. |
| 28:23 | We'll make this brief, larger injectors are going to artificially change the power output of the engine. |
| 28:30 | So the engine's no longer calibrated to the injector. |
| 28:32 | That is to inject 100 mm³, at 160 mPa, it no longer takes the pulse width described in the table here. |
| 28:45 | It's going to be different by a percentage. |
| 28:47 | And most reputable injector manufacturers will describe their injector change in units of percentage. |
| 28:54 | So 30% larger than stock, 60% larger than stock, 100% larger than stock and so on. |
| 28:58 | What this generally means is that at high loads, pay attention here, high loads, the injector will flow that much more fuel. |
| 29:06 | So let's take 100 mm³ for instance, if we put those injectors in a stock truck, with a correctly calibrated pulse width table, 100 mm³ and 160 mPa, that injector would, instead of flowing 100 mm³ at that pressure and that pulse width, it would flow 130 mm³ or 30% more. |
| 29:26 | 100% injector, likewise would flow 100% more fuel. |
| 29:30 | So what we're expecting here is 30% more horsepower, 30% more toruqe. |
| 29:35 | 100% more horsepower, 100% more torque. |
| 29:37 | So when you're targeting those power numbers for customers with modified injectors, keep in mind that you're not going to have to make modifications as large to the pulse width to get those dramatic changes. |
| 29:49 | The larger the injector, the smaller the changes you're going to have to make in pulse width to get those power numbers to move. |
| 29:56 | I would also caution you against modifying the idle rows, zero to 20, and even the part throttle I wouldn't mess with unless you feel that drivability is being detrimentally affected by the injector. |
| 30:10 | Try and focus on the higher power, higher output rows first and then move down as you see necessary. |
