Road Tuning: Step 7 - Steady State Tuning
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Step 7 - Steady State Tuning
17.13
| 00:01 | Okay, so the time's now come to actually start tuning the engine while we're driving it. |
| 00:06 | For the most part, at this point, we're going to be concentrating on the fuel first. |
| 00:10 | We can basically forget about the ignition map. |
| 00:13 | What we do want to do, though is monitor for detonation while we're tuning that fuel map. |
| 00:19 | The numbers we entered, hopefully, if we've got our numbers in the right ballpark, we shouldn't be having any problems with detonation, but we just want to be audibly listening for detonation, just in case we've got an engine that's, perhaps, very high compression or very susceptible to knock. |
| 00:35 | So, as long as we're not having any problems with detonation, we can concentrate, at this point, solely on tuning the fuel side of the map and that's what we're going to do. |
| 00:43 | So, what we want to do is start by driving the car with as little rpm and as little throttle as we can. |
| 00:50 | I'll generally start in second gear and this, particularly when we're tuning an engine that we've got no map for at all, we want to really not have to worry about any cars or traffic, so that's why we've got an empty drag strip here. |
| 01:06 | So, I will generally start with around about 1500 rpm is a good place and we're just using our left foot braking technique to just control the engine load and rpm and we want to start with as little throttle on board as possible and then we just need to make adjustments to the fueling numbers to get our lambda on target. |
| 01:38 | We're just adding a little bit of fuel into that zone. |
| 01:41 | It's quite important to make sure that we're adjusting the throttle position and brake to stay as close to the center of the cell as we can. |
| 01:50 | Once we've tuned that particular cell, we can copy the numbers into the next cell and increase the throttle position and increase the load. |
| 02:03 | So, once we're into the next cell, we can tune that. |
| 02:11 | And again, we copy it down into the next load zone. |
| 02:17 | As we move into the increased load, the air fuel ratio starts to move a little bit lean, which is what we'd expect, so as we increase the load, the VE of the engine increases and hence, we also need to add a little bit more fuel. |
| 02:34 | So, this is the process we continue, basically, until we have got to wide open throttle. |
| 02:44 | We're just matching our target. |
| 02:47 | You can see at wide open throttle there, we're quite lean, we're about .97, whereas we want to be at .90. |
| 02:55 | So, we need to add a little bit more fuel. |
| 02:56 | Okay, so that's that row complete. |
| 02:59 | Now, what I hadn't shown you there is the lowest load we could get to was 40 KPA. |
| 03:07 | That's still pretty realistic as to the sort of load we're going to expect to see when the engine's running. |
| 03:13 | What I generally do, because if we're at very light throttle, perhaps just rolling down a hill, we may be able to pull the throttle back far enough to drop down into the 30 KPA section here that I'm just highlighting. |
| 03:27 | What I would've done, because I actually pulled some fuel out with the change that I made to that 40 KPA row, sorry I actually added some fuel. |
| 03:36 | What I would've done was I would've highlighted the row, the zones below it and I would've made the same change to those to just retain a smooth shaped fuel curve. |
| 03:47 | Now, once we've got the complete tune finished, we can address those areas again if we need to at very light throttle cruise. |
| 03:53 | At the moment we need to build up the map. |
| 03:55 | Once we've got that 1500 rpm slice of the fuel curve tuned, we need to copy that across to the 2000 rpm row. |
| 04:06 | Now, as we increase the rpm, we can also expect the volumetric efficiency of the engine to increase, so what we're going to do before we access that 2000 rpm column, we're just going to multiply the entire column by 1.05 to add five percent fueling to it. |
| 04:22 | Now, that's going to hopefully get us really close to our target before we start tuning. |
| 04:28 | Now we've done that, we can again just drive the car in the 2000 rpm row exactly the same way we did and see where we're at and how close we are to our target. |
| 04:40 | What I'll do before I make any individual changes there, you can see we're about two percent lean on that particular zone. |
| 04:48 | I'll just increase the fueling through that whole 2000 rpm row, before I make individual changes. |
| 04:58 | The reason being is I'm expecting the volumetric efficiency change of the engine to be relatively smooth. |
| 05:04 | So, if we're lean at 2000 rpm and 50 or 60 KPA, I'd expect we'd probably be similarly lean at 2000 rpm and 100 KPA or 30 KPA. |
| 05:16 | So, before I start individual site tuning, I would just make an across the board change to that 2000 rpm slice. |
| 05:23 | It should speed up my process. |
| 05:25 | Now that we've done that, we can go back to 2000 rpm and we can start narrowing in on individual sites. |
| 05:32 | So, we'll again go as low on the load as we can. |
| 05:36 | We're down at 30 KPA. |
| 05:39 | What you find is during the very light throttle, it's quite difficult because the engine will tend to slow down. |
| 05:46 | You can see we're really close to our target, so I'll increase the load and hold the rpm stable. |
| 05:53 | We're a little bit rich there, so I'll just pull a little bit of fuel out. |
| 05:57 | Again, we'll increase. |
| 06:01 | Again, just a touch on the rich side there. |
| 06:07 | Driving the car and controlling the load and rpm like this is quite an art and it does take quite a long time to perfect. |
| 06:17 | Basically, our mixture is very close. |
| 06:19 | If anything, we're just a little bit rich everywhere. |
| 06:23 | Just increasing the load further. |
| 06:28 | Then we can go to full throttle. |
| 06:30 | You can see we're actually quite rich at full throttle. |
| 06:34 | Okay. |
| 06:35 | That's the 2000 rpm row complete. |
| 06:39 | So, because this is quite hard on the brakes, I will tend to do a row like this and then I will give the car a chance to cool down a little bit, so that means driving without using the brakes and just letting some airflow get over the brakes and get everything back down to a normal operating temperature. |
| 07:00 | Okay, so now that we've done the 2000 rpm row, we're starting to build up a better picture of our map. |
| 07:05 | We've copied that through the 2500 rpm row and we're just going to repeat the process. |
| 07:11 | So, we start by driving at 2500 rpm and making any changes we need to to that particular row. |
| 07:20 | So, we were just a little bit rich there. |
| 07:23 | I just made a change, so now we can concentrate on the individual sites. |
| 07:27 | So, I'll just see if we can get down to 30 KPA. |
| 07:30 | We can't really, so we'll go up to 50. |
| 07:46 | Okay, and we'll go up to 60 KPA now. |
| 07:49 | See, we're a little bit lean there. |
| 07:59 | Then wide open throttle. |
| 08:05 | Okay, and that's what we need to do to actually tune the fuel table. |
| 08:10 | So, the rest of the process is just a case of rinse and repeat of that particular process. |
| 08:17 | Generally, what I like to do with that is I will complete the mid range part of the map, like we're doing now, up to about two-thirds of engine rev limit. |
| 08:26 | So, in this case I'm going to do that up to about 5000 rpm. |
| 08:29 | The reason I'm concentrating on up to 5000 rpm is there's a very narrow range that the engine is going to be driven in regularly. |
| 08:38 | Normally, it's going to spend most of its time either at idle, which we've already addressed, or cruise, and the cruise area consists of about 1500 rpm through to about 3500 rpm. |
| 08:52 | Beyond that, generally the engine's only going to be driven at wide open throttle or in a transient condition. |
| 08:57 | So, we don't need to be as fussy about the rest of the map. |
| 09:02 | So, I'll just complete that now up to 5000 rpm and you can watch what we do. |
| 13:34 | All right, now I'll come back. |
| 13:43 | So, once we've tuned the engine in a steady state like that up to 5000 rpm, we've really filled in a good majority of the map and on a fairly low power car like this, it's actually quite easy to do. |
| 13:54 | As I said, you do have to pay particular attention, though to the brakes, they will get a hard time. |
| 14:00 | So, you need to give them adequate opportunity to cool down. |
| 14:04 | Above 5000 rpm, though, most people aren't going to be driving the car up at part throttle, so we don't need to be quite so accurate with our mapping. |
| 14:13 | What I'll generally do is I'll start by copying the numbers that I've just completed for the 5000 rpm row and I'll copy them the whole way through the rest of the map to give the map some shape or some numbers that I'm hoping are going to be pretty close. |
| 14:29 | Now, what I'll do beyond that is I will highlight the next row of the map that I haven't yet accessed. |
| 14:36 | So, in this case we're going to go to 5500 rpm. |
| 14:39 | What I want to do is just drive the car briefly. |
| 14:42 | I'm not going to look at the whole map, I'm not going to look at all of the load zones in that row. |
| 14:46 | I'm just going to highlight that whole row, I'll drive at part throttle with a moderate amount of load and I'll just see where the mixture is and I'll then make an adjustment to that entire row, either up or down, to get the mixture where I want it to be. |
| 15:07 | So, because we've been targeting slightly richer at part throttle there at 5000 rpm, we want to stay right about .95 lambda. |
| 15:17 | Okay, so I just added some fuel there, which is probably what I'd expect. |
| 15:20 | Again, our VE is still increasing. |
| 15:22 | So, we'll just copy that 5500 rpm row up to 6000 and do exactly the same process again. |
| 15:45 | Okay, so again, the engine wanted to see a little bit more fuel at 6000 rpm. |
| 15:50 | We'll copy that across to 6500 rpm and test that zone. |
| 16:08 | Now, we don't really need to be doing this at 7000 rpm and above. |
| 16:13 | No one's going to be driving the car there, so it's safe to just copy the numbers that we've just seen across and we're going to touch up those high rpm rows once we do the wide open throttle fuel tuning. |
| 16:30 | So, once we've done the fuel map like this we should have a car that, for the most part, is driving quite smoothly everywhere. |
| 16:37 | Now that we've tuned the fuel table, I'll just talk about the ignition and we can't tune that in steady state the same way we've done the fueling, because we've got no feedback on engine torque. |
| 16:49 | Instead, all we want to do at this stage is make sure that we've got no detonation occurring while we're doing that fuel tuning. |
| 16:56 | So, we're not going to actually make changes to the part throttle numbers in the ignition map. |
| 17:01 | We're going to look at that once we've done the wide open throttle tuning and then we'll come back and look at this part throttle ignition mapping again. |
