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Ethanol & Flex Fuel Tuning: 5. Tune for Secondary Fuel

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5. Tune for Secondary Fuel


00:00 - With our ECU configuration now complete in our G4 Plus to suit E85 we can go ahead and perform our E85 tune.
00:09 Remember at this point all we've done is copy the fuel table one and ignition table one data across to our second set of tables, so at this point our tune is essentially completely unaltered from what we were running on pump fuel.
00:23 So at this point the required additional fuel volume is being dealt with by the Link G4 Plus software purely based on the fuel characteristics that we entered along with the multi fuel blend table that we've also adjusted.
00:38 Now this is a good place to have a little bit of a sanity check before we get too deep into our tuning.
00:44 At this point we should expect when we get the engine up and running that our lambda data or out air fuel ratio data should be broadly similar to what we saw on pump fuel.
00:54 Certainly we can expect some discrepancy but I'd like to expect or see the air fuel ratio within about 10% of where we were on pump fuel.
01:04 If you're outside of that range it may indicate that you've got some problems with your configuration and it may be worth going back and just confirming everything is correct.
01:14 Now when you go to start the engine on E85 for the very first time, particularly if the engine is cold, you may need to make some adjustments to your cranking enrichment table and warm up enrichment tables.
01:26 Remember we only took some broad guesses at that data that we needed at the E85 content value when we were going through the configuration.
01:34 So if the engine does struggle to start, that's the first place you should be focusing your energy.
01:41 Alright what I'm going to do now is we'll turn the fuel pumps on, we'll get the engine started and we'll have a look and see how our lambda compares to what we had before.
01:59 So the first thing we can notice there is that our VW Corrado still starts really well on E85 even with those base guess settings that we've put into our cranking enrichment table.
02:10 Now if we look at our lambda LTC1 value coming from our dyno you can see that currently sitting at idle the lambda is around about 0.97 to 0.98 Obviously it's moving around a little bit.
02:23 If we compare that to the lambda target, this is the same target we were using on pump fuel, you can see that that's approximately the same where I've got a target of 0.97 So this is meaning that at idle our air fuel ratio has essentially remained unchanged.
02:40 Now we can go a little bit further with that, we can check some of our part throttle air fuel ratios as well, make sure that those are all matching.
02:48 I'm going to jump ahead and we're going to now perform a ramp run on that same boost setting we were using on pump fuel and we're going to see how much our air fuel ratio has varied during a wide open throttle ramp run in an area that we know we've already tuned on pump fuel.
03:05 Again we can expect some discrepancy here, so of course we want to be monitoring that air fuel ratio.
03:10 If we see it move outside of the range that we're comfortable with, we can simply abort the run, and make the necessary changes to our second fuel table.
03:19 Let's go ahead and do that run now.
03:40 OK so we've got our first run complete there on E85.
03:43 Remembering again we've still made no changes to our second fuel table.
03:47 The important thing to note here is we've overlaid this with our pump gas tune and we can see that there definitely is some discrepancy in our lambda.
03:55 Generally through that whole run we were around about 2% or 3% lean.
04:01 We can also see that we're actually a little bit leaner in the mid range than right at the top end of the run, where we've almost come back to exactly the same lambda target that we were running on pump fuel.
04:12 We can see our boost is again broadly the same.
04:14 And of course at this point we haven't made any adjustments to our ignition timing so our power is also broadly the same as what we were seeing on pump fuel.
04:23 So at this point I'm comfortable that everything is checking out.
04:27 The flex fuel system is doing exactly what it needs to do, it's making those adjustments, we do have that small error as we would expect.
04:35 We can now go ahead and make our tuning changes.
04:38 Now it's also important when we're making these tuning changes to understand where we are making the changes.
04:44 It's really important to make sure that we are making changes to the correct table.
04:49 We can see at the top of our fuel table here it says fuel table two.
04:54 Likewise if we jump across to ignition table, we want to make sure we're making changes to ignition table two.
05:00 These are the two tables we're referencing at the upper end of our flex fuel system where we're at 85% ethanol.
05:09 It's really easy if you're in the habit of tuning the G4 Plus system simply to press the F key to jump to the fuel table and we can see that pressing that once will take us to fuel table one.
05:21 And it's very easy to make the mistake of making adjustments to the incorrect table, wondering why you're not getting the effect of change that you're expecting.
05:31 This can also be a big waste of your time.
05:34 Now the other thing to point out is the sort of magnitude or changes that we're likely to see.
05:39 Now at this point we've been running at exactly the same boost level that we were running on pump fuel.
05:44 So we're running around about the 100 to 110 kPa rows.
05:49 Now we know that broadly speaking here both our fuel and ignition tables, fuel table one, and ignition table one are correctly tuned for pump fuel.
05:58 We know that we were marginally knock limited here on pump fuel so it's fair to expect that we're going to be adding a little bit more ignition timing, we should be able to tune up to MBT, particularly at this low boost level.
06:11 And as we've already seen, our fuel table two is already pretty close, we're just going to need to make some small adjustments.
06:18 The important thing to note though is that as we increase the boost up to our new target that we're going to be running on E85, 260 kPa or approximately 24 psi, we're obviously moving well above the area in both our fuel and ignition tables that we have tuned on pump gas.
06:37 What this can mean is that the accuracy of our fuel table two and ignition table two values in those areas may be quite marginal.
06:47 This is because we simply haven't got any really good base data from fuel table one and ignition table two that we've copied across.
06:55 All we've done is extrapolated the values, or the trend that we've seen up to the point where we have tuned on pump fuel.
07:02 So that's a really important thing to note there, we may need to do quite a bit more work as we increase the boost and move further into the untuned areas that we haven't looked at on pump fuel.
07:12 Alright we're going to jump ahead now, we're going to complete our tune, and we'll come back and have a look at the results we end up with.
07:19 With our tune now complete on E85, the first thing we can see is the large improvement that we've got in power.
07:25 We're now making 315.5 kilowatts or 423.1 horsepower at the front wheels.
07:31 Now the graph that we've got here on our Mainline dyno is overlaid over the grey lines from our final pump gas tune just so you can see the exact magnitude of those changes.
07:42 Now obviously we have increased the boost as we can see here the red line is now sitting at 24 psi or 160 kPa for our E85 tune.
07:52 Now this obviously has accounted for some of the improvement in performance but remember we were heavily knock limited on pump fuel so we simply couldn't have safely run the engine at that sort of boost level.
08:04 At the top we can see our lambda trace which broadly is identical to what we were seeing on pump fuel.
08:11 Now particularly as I mentioned when we're out at that higher boost level where we haven't been able to tune on pump fuel, this is where we can expect to see some larger discrepancies in our second volumetric efficiency or second fuel table.
08:25 And that's exactly how things panned out here.
08:28 Essentially though the tuning process we've gone through is exactly the same process that we used for tuning pump fuel.
08:35 We've just simply gone through the HPA 10 step process, optimised both our fuel table two, and ignition table two values to suit the E85 fuel properties.
08:46 Let's have a quick look at the changes that we've made here.
08:50 So we've got our fuel table one values, and particularly if we look at the area which we could tune on pump fuel, if we look at the two rows between 100 and 120 kPa, if we take a broad value here for example at 120 kPa and 5000 RPM, we've got a value of 88.5% VE for fuel table one, for our pump gas tune and we've gone up to 96% for E85 for our flex fuel tune.
09:20 So we've got a change there of around about 8%.
09:25 So this is in line with what I was expecting to see from the changes we've made.
09:30 Let's have a quick look at the shape of the VE table for our second or E85 fuel table, and again we can see we've got a shape that broadly in line with what we'd be expecting from this engine.
09:43 Let's jump across and have a look at our ignition table, we'll start with ignition table one, our pump gas ignition table.
09:50 And remember we were running at full boost here around about the 200 to 220 kPa row.
09:57 Now if we have a look at some of the values in there, particularly where we first come on boost, where we're quite close to the engine's peak torque we can see that we've got values of 10, 12, 13 degrees in that area.
10:09 Now if we jump across to our ignition table two, and we can see that we've been able to advance the timing quite dramatically in that area.
10:17 We're now up to 15 to 18 degrees in that same area.
10:21 So this is our ability on E85 at even the same boost pressure to optimise the ignition timing right up to MBT.
10:29 What we're more interested in though is what we've been able to do at our higher boost target.
10:34 In this case remember we were targeting around the 260 kPa row.
10:39 And you can see that we've running anywhere from around about 10 degrees, when we first come up on boost, all the way through to 19 degrees at the rev limit.
10:50 And again on E85 at this sort of boost pressure, we've been able to optimise the ignition timing there to MBT with absolutely no indication of any knock present at all.
11:02 So at this point our tune is complete.
11:04 The last step of our tune here on E85 would obviously be to optimise our cranking enrichment and our cold start enrichment, when we've allowed the engine to cool back down.
11:16 So we'd need to do this the day following our tune.