Road Tuning: Step 3 - Base Table Configuration
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Step 3 - Base Table Configuration
09.53
| 00:00 | The next step is actually configuring the fuel and ignition table, so we've got some numbers in there that are going to be a good starting point. |
| 00:07 | Now, the tables we've got at the moment have basically finished off where we've left up after tuning the engine yesterday. |
| 00:14 | I'm just gonna talk through that a little bit first and we'll set them back to some sensible starting point. |
| 00:20 | So you can see we've got the load axis here set to manifold pressure and obviously we've got rpm here as well. |
| 00:27 | If we press X we can access the axis set up menu for the Link G4 Plus and one of the things I find frequently novice tuners do is try and add too many zones. |
| 00:40 | So because the ECU interpolates we really don't need super accurate resolution in this table. |
| 00:48 | The ECU will work to interpolate between the surrounding cells, so what I suggest for the load axis is we use manifold air pressure for most engines. |
| 00:58 | That's going to be suitable unless you've got something with multi-throttle bodies or an engine that has very low vacuum due to large, aggressive cams. |
| 01:07 | In that case you may want to use alpha-N or throttle position. |
| 01:10 | So for the majority of engines using a single plenum and throttle body, manifold air pressure is going to be want we want to use. |
| 01:18 | So what we want to do is set the load axis sites every 20kpa. |
| 01:23 | And as I've said in the course, I'll generally add another zone around about 30 and 50kpa to help address the tuning around the idle and cruise area because that's the area the engine is going to spend most of it's time and that will allow us to add some more accuracy there where it's most important. |
| 01:43 | If once you start tuning you find that there is a particularly large step in either in volumetric efficiency in either load or rpm, it's easy to come back to this table and add extra sites later, so don't think that just because you've chosen these sites that's what you're stuck with. |
| 01:59 | In the rpm zones I will generally run the engine out with rpm sites to about 500rpm past my expected rev limit and again you can see here I've added an extra site at 750rpm which is around about my expected idle speed and sometimes it can also be helpful to add another site just above idle which is the transition from idle to driving and that can be handy to help smooth out that area. |
| 02:28 | So once we've done that, we've got our actual fuel table here and as I've said, we've already got some numbers in there. |
| 02:35 | Now the numbers in this table are going to depend on how much fuel the engine needs and we're not really going to know that straight away. |
| 02:42 | What I would do to start with though is set the entire table to something that I'm expecting the engine to idle at. |
| 02:50 | Somewhere around about 30%. |
| 02:52 | Okay, so that's just flattened the whole table. |
| 02:55 | Now if we were on the dyno, that's probably good enough to actually go and start doing some tuning, get the engine running and work from there. |
| 03:03 | Because we're road tuning, we do actually need to be able to drive the car straight away in order to get the engine running and make changes, so we probably need something a little bit closer than that. |
| 03:14 | Now, we're obviously not going to know exactly what those numbers are going to be. |
| 03:20 | That's the job of tuning, but we can deduce a kind of idea on what the fuel map should look like. |
| 03:26 | And generally as we increase the load we are also going to increase the fueling, so what I'm going to do is just go through and add 2% to each of the rows as we go up in load. |
| 03:40 | So that's just my guess at how much additional fuel we're going to want to add as we increase the load in the engine. |
| 03:49 | Okay, so that takes care of increased load. |
| 03:52 | Volumetric efficiency is also going to increase though as we increase our rpm. |
| 03:56 | So the torque curve of the engine has a pretty good indication of what the fuel curve should look like. |
| 04:02 | Obviously, because we're not on the dyno we don't know that so again, we've got to make some guesses and what I'm going to do is increase the fueling by again, two numbers as we increase the rpm. |
| 04:16 | And I'm going to do that all the way through to about 4,500rpm which is where I might expect to see peak torque. |
| 04:27 | Beyond 4,500rpm, I'm just going to copy those numbers directly across. |
| 04:32 | Now, at high rpm we may actually see the fueling decrease again because volumetric efficiency will drop off. |
| 04:41 | So if I want to get fussy we can actually add some more shape to the curve and we can have it drop off as well at high rpm. |
| 04:49 | So this is only a guess. |
| 04:50 | It's probably going to be a long way from what we need, but it should be enough to get us up and running quickly with a car that we can at least drive on the road while we start dialing in the fueling. |
| 05:01 | Now if we swap to the ignition map, basically this is the one area of road tuning we really do have some downsides compared to dyno tuning. |
| 05:09 | We don't have feedback on torque, so this is the area you really need to be prepared to make some compromises. |
| 05:16 | There's a pretty good chance that your ignition map is not going to be optimal, but there's nothing we can really do about that if we're not prepared to spend some time on the dyno. |
| 05:28 | So I would start with a map that looks something like this. |
| 05:32 | Again, first of all, looking at our load and RPM axes we don't need to be quite as fussy here, so we've got load sites every 20kpa and we've got rpm sites every 500rpm. |
| 05:44 | So that just basically matches what we saw in the fuel table. |
| 05:48 | We want to make sure that our load axis is the same as the fuel axis table. |
| 05:53 | Secondly, I basically will start by entering some numbers that I know are going to be pretty close. |
| 06:00 | So most engines will idle with ignition timing of around about 15 degrees quite happily, so that's what I'm going to put down in this zero to thousand rpm and zero to 20kpa area. |
| 06:12 | And you can see the ignition timing gradually advances up to around 32 degrees at 3000rpm and low load and again, this is the area where the engine will probably be cruising. |
| 06:24 | And these numbers I have come up with here are based on my experience of tuning virtually thousands of engines on the dyno of what I see works quite well. |
| 06:35 | At high rpm we can increase the ignition advance slightly. |
| 06:38 | You can see we go up to about 35 degrees. |
| 06:42 | These areas of the cruise and light load, we're not expecting to have problems with detonation, but at high load, full throttle that could be an issue. |
| 06:51 | And you can see we've retarded the timing and at high rpm we're seeing 25 degrees. |
| 06:58 | Down at low rpm, 2000 perhaps, we're down at sort of 19-20 degrees and that's as good a starting point as we can really come up with if we're not going on the dyno and you can see if we look at the graphical display, we've just smoothly translated between or interpolated between those load numbers. |
| 07:17 | So this is going to be our starting point and we're going to tune from this table later on. |
| 07:22 | If you've got a turbocharged or supercharged engine, this table is also going to extend out into boost pressure and generally I like to remove around about 2 degrees of ignition timing per 20kpa just to account for the added air flow, added volumetric efficiency, and added load from positive boost pressure. |
| 07:43 | One other thing we want to check carefully before we go as far as tuning is make sure that our compensation tables aren't doing anything silly in the background that could affect our tune and have us chasing our tails. |
| 07:55 | So, the two common ones I see there are warm-up enrichment and also our intake air temperature correction. |
| 08:02 | We'll just have a really quick look at both those tables now. |
| 08:05 | So the warm-up enrichment, what we want to do is make sure that our normal operating temperature of, sort of 80-90 degrees, that we've got zeros in this table, so that just makes sure that the ECU isn't turning any additional fuel in the background. |
| 08:22 | At the same time we'll check our intake air temperature fuel trim table and you can see we've already got this pre-configured at our standard operating intake air temperature of 20 degrees, we've got zeros in the table as air temperature increases, air density decreases and you can see we're trimming fuel out. |
| 08:42 | Conversely, as air temperature decreases, our density actually increases so we want to add fuel to cope for that. |
| 08:51 | Now I've set this table up as a 3D table. |
| 08:53 | You can see at the moment our air temperature is sitting at 55 degrees. |
| 08:57 | We've driven the car for a while and it's been sitting stationary with the bonnet down, so it's unsurprising it's heat soaked. |
| 09:04 | You can see further up in the table we're trimming out as sort of 8.5-9% fuel which is what we would want to remove if this was an actual intake air temperature and we were driving on the road. |
| 09:17 | This isn't real though, it's heat soaked, so it doesn't actually represent the real intake air temperature if we were to start the engine up right now and if we did that and we had these compensations running all the way through to closed throttle what would happen is after a hot restart the engine would run lean and be erratic and hunt for a few minutes after start-up, so you can see I've trimmed some of that compensation out down at closed throttle. |
| 09:44 | It doesn't have as much control and that helps eliminate some of that and get a more consistent tune. |
