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Practical Standalone Tuning: Step 7: Steady State Fuel Tuning

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Step 7: Steady State Fuel Tuning

33.42

00:00 - OK so now we're going to have a look at our steady state fuel tuning and we're going to start with the fuel and we're just going to leave the ignition side of things completely alone and deal with it separately after we've got the fuel side of things sorted out.
00:14 Now as I've said, we've set the whole base ignition map at 15 degrees and while we're only going to tune the fuel side of things, we do want to listen while we're doing this for detonation and make sure that the engine isn't running into any knock while we're setting up the fuel.
00:35 Now because I've tuned this engine, I do know that down at low RPM around 1000 to 1500 RPM, and high load, 15 degrees ignition timing actually does result in some very light detonation.
00:49 So while we're doing this, I'm just going to take five degrees out of there and that's going to stay away from that detonation.
00:58 Now if you are dealing with this, as we explained in the course, where you're just tuning the fuel, you would notice that because you're going to hear that detonation start to come in over your headset.
01:09 So that would be the cue to stop and remove some timing as I've just done from the ignition table before moving on.
01:17 We're hoping that in general, that 15 degrees across the board, is going to be a nice safe place to start.
01:23 but with some particular engines, particularly high compression engines, or those running low octane fuel, we may find that occasionally we still need to retard the timing beyond that.
01:34 So let's go back to our fuel map and we're going to start with 1500 RPM which is about the lowest we can go in the RPM.
01:43 And we're going to start with as little load as we can get on the engine.
01:49 So we're just using fourth gear here, and I'll just get the engine running on the dyno.
01:55 OK so now once we've got the engine running at the right RPM on the dyno, particularly when you're using throttle position as a load, it's very easy to be very accurate on whereabouts in the map you're going because all you need to do is move your throttle to the correct position and that's where the engine will go.
02:17 As usual though, we do have the problem where at very very light throttle openings, the RPM, there isn't enough inertia to keep the dyno running and the engine will just slow down.
02:31 So now we're running at 5% throttle, 1500 RPM, and you can see we're running at about 1.04, oh let's just get it running stable there.
02:44 Running at about 1.07, 1.08 lambda.
02:48 So we're around about 8% lean.
02:52 At this point I'd be wanting to running at lambda one.
02:55 So we can multiply it by 1.08 which is adding 8% fuel.
03:00 And you can see we're corrected back, now it's sitting at lambda 1.01, 1.02 Oh we're actually right on now, when I'm in the middle of that zone, we're bang on where we wanna be.
03:16 So now the next step is to increase the throttle up to 10% but before we do that, we're just going to copy the number from that site up and now we can increase the throttle.
03:34 And we're about 14% lean there.
03:38 So we can times that by 1.14 And again it corrects it back to lambda one.
03:45 Now I'll just take my foot off the throttle there so the engine noise goes away.
03:50 Now what I'm going to be doing here is I'm going to be targeting lambda one up to around about this 40% throttle area, and then I'll be smoothly increasing the fuelling, decreasing the lambda target until I'm at about 0.90 out at 100% throttle.
04:10 So because there's no feedback in this ECU for a target air fuel ratio map, basically I'm doing this manually.
04:19 I just know what I want to target at a particular throttle opening and that's what I'll go for.
04:26 Now once we get up above 5000 RPM, in the cruise areas of the map, sort of our through about this area here, gonna be targeting slightly richer, around about 0.95 And in the top end, just to protect the engine a little bit, might start dropping the target lambda back to around about 0.87, 0.88 So we'll just go slightly richer in the top end where there's a lot more heat in the combustion.
04:56 OK so we'll just continue now, and we're going to move out to the 15% row.
05:02 Now obviously we don't want to run the engine lean for any long period of time.
05:08 And you can see there while I was setting that up, we were running at about 1.14 lambda.
05:13 Now when there's no load on the engine, we're not going to do any damage.
05:17 But it's also not ideal, I'm only doing this for the purposes of our demonstration.
05:22 I'm gonna show you now how I'd really do that when we tune the 15% throttle area of the map.
05:29 So what I'll do first of all is copy that number that we had at 10%, copy that down into the 15% throttle.
05:35 Now there's a pretty good chance that we're going to be lean when we go to 15% throttle, just like we saw when we moved from 5% to 10% and I'm gonna show you how I deal with that.
05:46 So we'll get the engine running again, and we'll smoothly increase the throttle up to 15%.
05:57 OK so what I did was I ran the engine at 15% throttle and while it was there I had a look at the lambda and we're sitting at around about 1.09 so we're about 9% lean.
06:09 So rather than sit there and make the change, what I did was let the engine come back to idle.
06:14 Now I can safely make a change of 9% and we should now be pretty much on target when we go back to that particular zone, so let's have a look.
06:35 OK and that's exactly what happened.
06:37 At that point we were sitting at 1.01 So we're still just very slightly leaner than what I'd want.
06:43 I'd probably just end up making a manual change there to that particular site and have another look at it.
06:50 So what we can do now is do the same process, we'll move that down to the 20% throttle area of the map and we'll go and have a look at that.
07:09 OK so we're around about 10% lean there.
07:13 So we can correct that.
07:19 And we can copy that number down into the 30%.
07:25 Now the other thing you can do is you can see a bit of a pattern emerge.
07:29 Basically each step of the map here, we're needing to add around about 10% more fuel.
07:37 So I could sort of start seeing a pattern emerge and start dealing with that myself.
07:42 So before we move into this 30% area I'm going to add 10% to the map.
07:51 And it should have me close.
07:58 OK so we're now a little bit rich, we're sitting at about 0.95 so we're about 5% richer than we want.
08:06 So I'll multiply the number by 0.95 And that brings me back, we're still a little bit too rich.
08:19 Yeah there we go we've got it where we want it to be.
08:21 So actually we didn't need that 10% there.
08:25 But you can start to see these patterns emerge and you can start adding a little bit of fuel as you move from zone to zone.
08:32 So now we're at 40% target and as I said, I'm going to start wanting to move a little bit richer than our lambda one.
08:40 So I'm basically going to interpolate just manually between lambda one and lambda 0.90 between this 40% and 100%.
08:49 So at this point I'd probably be liking to target somewhere around about 0.97 lambda, so let's have a look at that.
09:02 OK so we're a little bit lean there.
09:05 I could just add a few numbers into that particular zone and now we're sitting at 0.97 So we can copy that down, again we're going to be wanting to target a little bit richer.
09:18 Now I'd probably be looking at about 0.94, 0.95 so let's see where we are when we go to that zone.
09:34 OK so now we're at 0.95 I've just added a few numbers in there.
09:39 So you can see basically as I'm tuning this, I'm using multiple techniques.
09:43 I'm using the calculation of multiplying by the percentage we're out or sometimes I will just manually add numbers to the table and that's quite easy to do, it's easy to just use in this case the shift plus Q and A keys, Q adds fuel, A removes fuel.
10:02 And you can do that without needing to watch the laptop keyboard and I can just watch the lambda on the dyno screen and make changes on the keyboard and just keep making those changes until I get the lambda where I want it to be.
10:16 So now we're going to move through to 80%.
10:18 So again we'll copy that number up.
10:20 Now I'll probably be wanting to target around about 0.92 lambda at this point, so let's see where we are.
10:34 OK so again we're a little bit lean initially.
10:38 And you can see I can quickly get that through to that target 0.92 So this leaves us with one zone to do which is our 100% full throttle.
10:48 So we're going to do that now.
10:52 And we want 0.90 OK so that's as easy as it is to tune that particular row of the fuel table.
11:15 And then it's the same process we're going to use for each row that we need to tune.
11:19 Now one thing I want to point out here, I mentioned when I got the engine running and idling that the numbers we had in the idle area suggested to me that we were probably going to run out of resolution in the fuel table.
11:33 And that's proving to be the case, you can see here at 1500 RPM and wide open throttle, we've already got a number of 93.2 in the fuel table.
11:45 Now chances are we would certainly hope that as we start increasing our RPM, the engine's volumetric efficiency will increase so that's gonna demand more fuel.
11:56 And when we're already at 93.2 there's a pretty good chance that we're going to max out that table at 100% which is the largest number we can enter before we can tune the entire table.
12:10 So that's OK, we can address that reasonably easily by going back and adjusting our fuel injector master pulse width number which is in that fuel main table and we're going to look at that.
12:21 Before we do that I just wanna explain what I'd be looking for.
12:25 Basically we want good resolution in the fuel table, and by good resolution I mean we want a good span of numbers.
12:33 So we don't want to see the maximum number at wide open throttle and peak power or peak torque to be somewhere around about 20 or 30.
12:42 And the reason we don't want that is when we make a change of 0.1 or 0.5 to that number, it represents a large percentage change to the number so we get quite a coarse adjustment and we can't be as precise in our tuning.
12:59 On the other hand if the maximum number in our table ends up somewhere in the region of maybe 60% to 80% that means we can make quite fine precise adjustments to our fuelling.
13:10 A change of 0.1 to a number of 60 represents a much finer change than a change of 0.1 to a number of 20.
13:20 So generally when I'm setting that master pulse width number, what I want to do is scale my fuel table so that the peak number, the largest numbers we see on that fuel table fall in the sort of 60% to 80% range.
13:36 If we start getting much over 80% or 90% we start running into potential problems with running out of numbers in the fuel table.
13:45 So yeah 60 to 80, generally sort of 70% would be a nice area to be in.
13:51 And if we're seeing this sort of scaling here, that's going to cause a problem, so let's go and fix that now.
14:00 So if we go back into our fuel main table.
14:05 We can see we've got our master pulse width number there.
14:10 If we make a change to the master fuel, we can multiply this by 1.5 So that would take us from a number of 14 milliseconds up to 21 milliseconds.
14:25 Now what we wanna do is make that same, or the opposite change to the numbers on our main fuel table.
14:31 And that will keep our fuelling exactly the same.
14:34 So if we enter 21 in here, you'll see that the lambda on the screen goes excessively rich.
14:42 We're now idling at about 0.72, 0.73 lambda.
14:46 So if we jump back to our main fuel table and we highlight the entire fuel map, we can make the opposite change to the fuel map to get our numbers back in the correct area.
14:58 So if we divide one by 1.5 we're going to get a multiplier of 0.67 And that's the multiplier we want to add in here.
15:11 So multiply the entire fuel table by 0.67 so that reduces all of those numbers in our fuel map and you can see now our lambda on the dyno screen is back to 0.95 Now that should in essence basically produce exactly the same result when we run the car at 1500 RPM as what we had.
15:32 So let's just go back and have a look at that.
15:36 Yep and you can see that down in those low throttle areas we're still running the engine at around about lambda one.
15:45 And at wide open throttle we're at 0.90 lambda.
15:52 OK but what you can see is now those numbers that we had here at 93%, we've reduced that down to 62%.
15:59 So that's how we can correct the master pulse width.
16:02 OK so now before we carry on, what we're going to do is just copy that 1500 RPM row across to the 2000 RPM column and we're going to multiply the whole row by 5% just to add a little bit of extra fuel to cope with what we'd expect to be an increase in our volumetric efficiency.
16:27 We'll just take the dyno up to 2000 RPM now and what I'll do is I'll just go through and tune that particular row.
16:35 And we'll see how we get on.
16:39 Now again before I make any changes to an individual cell I'm going to adjust the entire row, so I've still got the entire column highlighted.
16:50 And we're just a little bit rich, we're at 0.97, so I'm just going to reduce the fuelling there until we're at lambda one.
16:59 OK now we can look at the individual cells.
17:03 And as we expect, I've just dropped down to 5% throttle and you can see we're very close to where we wanna be.
17:11 Come up to 15%.
17:19 20%, we're a little bit rich at 20%.
17:27 30% we're still a little bit rich.
17:31 Now 40% we're gonna start going a little bit richer now, we're going to target 0.97 At 60% we're going to target 0.95 so we're a little bit rich there.
17:47 Now 0.93 at 80%.
17:54 And 0.90 at wide open throttle.
17:58 So you can see we can really quickly adjust that whole row and again we're just gonna do the same process and copy it through to 2500.
18:06 Our multiplier, we didn't really need that full 5% so let's try 4% for this next row.
18:13 Now one little trick I'm gonna show you here as well.
18:15 If you are tuning a completely fresh table like this, you can see now we've got at 15% throttle and 2500 RPM, a number of 50.6 in here.
18:26 We've got a number of 20.1 in the cell to the right as the RPM increases.
18:32 That's a huge difference.
18:33 Now what I'm getting at here is if our RPM's moving around a little bit and it starts increasing and interpolating from this 3000 RPM row, it can make a huge difference to our mixture, and we can end up trying to account for that by tuning the 2500 RPM row.
18:50 So if your RPM is moving around on the dyno a lot, it can be handy to just copy that across to the next row as well.
18:59 So we're tuning the 2500 RPM row, but we've just copied those numbers into the 3000 RPM row as well just so that if it does interpolate, we're going to be closer.
19:10 So I'll just go through now and do the 2500 RPM row.
19:59 OK so that tunes the 2500 RPM row.
20:02 What we'd do now is just copy that across to 3000 RPM and again we'd just copy it through to 3500.
20:10 So I'm just gonna go through now, and I'm going to tune the rest of that fuel table up to 5000 RPM in steady state, and you can just watch what I do there.
21:39 So there's one thing I need to point out here is you can see our engine coolant temperature, some engines will control the engine temperature much better than others.
21:49 You can see here that at 3500 RPM here, we've just ended getting up to 100 degrees.
21:55 Now that's something you do need to keep an eye on while you're tuning.
21:59 It can be really easy, particularly when you're learning to tune to be so fixed on just the air fuel ratio, that you don't take notice of other aspects.
22:08 So I always want to just keep an eye on the engine coolant temperature and make sure that's not getting out of control.
22:14 If it does, like we just got to 100 degrees, I like to keep the engine coolant temperature at a maximum of 100 degrees while I'm tuning, I'd just allow the engine to idle for a little while, and the fan should bring the temperature down, and I'm just gonna do that before I continue with the tune.
23:56 You can see as we start using more load and more RPM, controlling that engine temperature becomes a little bit more challenging.
24:06 And that's why you wouldn't really want to be tuning the car for extended periods of time at 6000, 6500, and 7000 RPM.
24:13 The amount of heat that the engine is going to be producing would make it very very difficult to control that engine temperature properly.
25:57 OK so that's got the engine tuned now in steady state out to 5000 RPM.
26:02 But you can see that it's quite difficult to get down into these lower load areas of the map.
26:09 And particularly for a street car, those are the areas we're going to be using a lot.
26:13 So another trick that I would do there, is to, after I've done the fourth gear tuning as far as I can, I would also try using first gear, and that just gives us a little bit more torque multiplication and generally allows us to get down a little bit further in the load and tune a lot of those low RPM, low load sites that we're going to be using on the street and we're going to be able to do a better job of getting the tune right, before we actually go any further and have to look at it on the road.
26:48 So I'm just going to do that now.
26:53 And we'll start with again as low as we can go in the RPM which we should be able to get down to that 1500 RPM.
27:02 And you can see now that we can get all the way down to 2% throttle and the engine's still running quite happily.
27:11 So we couldn't get down there before.
27:13 And you can see that we're at 0.92, 0.93 lambda so we are quite rich there as well.
27:20 So we'll just take 8% out of that particular site.
27:25 And you can see that's corrected us back pretty closely to our target lambda one.
27:31 Now what I'd do there as well is you can see that we're never going to be able to get to 0% throttle at 1500 RPM.
27:38 What I'd do is just generally copy the trend back down into that site.
27:44 So you can see we've gone from 44 to 38 to 32, so there's a good chance we're going to probably want to be somewhere around about 28% before we go any further down into that load.
27:57 So now we can go up to 2000 RPM.
28:00 So we'll just increase the RPM on the dyno slightly.
28:25 And you can see we can't quite get down to that 2% there.
28:31 Yeah it's just a little bit too low in the load.
28:34 But I would use that technique to basically fill in as much of this area that we couldn't get to in fourth gear as I possibly can.
28:42 Once we've done that though, we've got the engine tuned completely up to 5000 RPM.
28:46 And we would then just copy that 5000 RPM column across to complete the rest of the map.
28:54 You can see here graphically we're starting to build up a little bit of a shape of what the engine wants to see.
29:00 And what we wanna do now before we do our full throttle tuning is we want to just briefly have a look at these 5500, 6000, 6500, and we wouldn't do the 7000 'cause that's actually on our rev limiter.
29:16 We just wanna have a look at those ares of the map and just broadly adjust them.
29:20 And as I said, now we're gonna actually target slightly richer so instead of lambda one in the cruise areas we're going to be targeting around about 0.95 Just slightly richer, this is an area we're only going to be seeing under wide open throttle.
29:35 So let's have a look and see what that area look like and we'll start with the 5500 RPM row.
30:00 OK so as we move from 5000 to 5500, the engine was slightly lean.
30:06 I just added a little bit to that entire column, and I just cycled through from the lowest load I could hold at 5500 RPM and I just slowly increased the throttle through to wide open and watched the lambda as I did that, and it all looked pretty close to my target.
30:23 So we'll copy that across to 6000 RPM and we'll increase the RPM on the dyno and do the same again.
30:45 So at 6000 RPM the numbers from the 5500 RPM column actually worked out perfectly, everything looked good.
30:52 We cycled from 0.95 through to 0.90 So we'll copy that across to 6500 RPM.
30:59 We'll have a look at that and we can pretty well call the fuel map done.
31:14 OK so what was happening there is we were just touching the soft limiter in the RPM limit.
31:20 So while I'm tuning this, what I'm going to do is just move that a little bit further out of the way.
31:26 You can see while it says it's set at 6800 RPM, the way that the Link G4 software works, is it actually soft limits 200 RPM earlier.
31:36 So we were just starting to touch that.
31:38 So I'll just set it to 7000 RPM, just so we can get the tune complete.
31:42 So let's go back to 6500.
31:59 OK so at 6500 RPM what we saw there is the mixture was actually a little bit rich.
32:06 And this is quite common.
32:07 Basically we've moved past the engine's peak volumetric efficiency, the engine's becoming less efficient, getting less air into it so it needs less fuel.
32:15 So we can follow that trend and we will actually reduce the 7000 RPM row.
32:21 So you can see here what I'm looking for is a nice smooth curve to my fuel map.
32:26 And basically if we see something that looks a little bit like this, we're probably on the money, we're probably pretty close.
32:33 Now you can see we've only tuned from 1500 RPM up, and we've got this funny area here in our fuel map which you can see has still got our base numbers in it, and is in essence untuned.
32:46 Now in some engines we can actually go and tune that 1000 RPM row.
32:52 Chances are we're not going to be able to apply full load to the engine on the dyno at 500 RPM.
32:58 So we've got a couple of options, either you can tune the 1000 RPM column in steady state like we've just done, or what you could do is copy the numbers that we've just got from the 1500 RPM column, and copy those back through.
33:11 And that's going to be a pretty close esitmate to an area that we're not going to really be able to run the engine in anyway.
33:20 I call it being fussy but it's nice to see a complete fuel table that looks smooth in every part.
33:26 If I see big holes or jumps in the map, I know that there's a pretty good chance something isn't right.