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Ethanol & Flex Fuel Tuning: Effect of Fuel Flow on Ethanol Content Reading

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Effect of Fuel Flow on Ethanol Content Reading


00:00 - As we've discussed in the body of the course, if you've fitted your fuel composition sensor to the return line from a fuel pressure regulator, and the flow of fuel through that return line becomes marginal at high RPM and high load where the engine is using a lot of fuel, then the output from the fuel composition sensor can become erratic and hence affect the accuracy of a flex fuel system.
00:23 We're just going to demonstrate what the output from an ethanol content sensor should look like if the flow is adequate.
00:30 Because we're still going to expect to see minor variations in the reported ethanol content.
00:36 For this demonstration we're going to be using our turbo charged Toyota 86, using the Motec M150 ECU.
00:42 Let's just have a quick look in the software, and you can see that we do have an ethanol hold function but for this demonstration I've set both of the parameters for that ethanol hold function to zero.
00:54 What we're going to do now is get our engine up and running on our Mainline dyno, and we're going to perform a wide open throttle ramp run, and we're going to have a look at the results in our logging once we've completed that run.
01:06 So let's get the engine running.
01:07 With our engine now running in fourth gear we can see our ethanol content is fluctuating slightly but by no more than about 0.5% to 1%, and this is relatively normal.
01:19 We can see in our time graph we're also logging the ethanol content as the engine's operating.
01:26 So let's get the run underway and we'll have a look at the results.
01:48 So there's a run complete on our Mainline dyno.
01:50 You can see on the dyno that we ended up with 224 kilowatts or 300 horsepower at the wheels.
01:56 The red line above is our boost, and we were targeting approximately 165 kPa absolute boost pressure.
02:05 Let's have a look now at the data in our Motec ECU software.
02:10 If we look at the data from the run we can see at the top we have our engine RPM here.
02:15 We started our run at just under 2000 RPM and we completed it at just under 7500 RPM.
02:23 Now if we move down we can see that we have our ethanol content being displayed.
02:27 Now the important point to look for here is that the amount of variation we're seeing with our ethanol content remains relatively consistent right through that run.
02:36 Down at low RPM where we're just settling before the run begins there's very little actual fuel flow, we're only at 2000 RPM and minimal boost pressure.
02:45 We can see that we're sitting around about 83% ethanol.
02:49 We can see that the ethanol content is varying much like we saw at idle, by around about 1% maximum.
02:56 And we can see that the fluctuation through that run remains relatively consistent as well.
03:02 What we'd be expecting to see if the flow through that return line was an issue is that the ethanol content would start becoming erratic as we get to higher RPM and higher load where the engine is physically using more fuel.
03:17 To show how erratic and inaccurate the ethanol content reading can become when the fuel flow through the composition sensor becomes limited, we're now going to drain the fuel system on our Toyota 86, and when the fuel system is just about empty we're going to see that flow through the composition sensor drop away and what we're going to do is watch the ethanol content reading on our Motec ECU software, and we're going to see what that does.
03:44 Remember we're still on our same ethanol content, somewhere around about 83% to 85%.
03:50 So I'm going to start the fuel pump now and we'll watch the ethanol content change.
04:00 So straight away we can see our ethanol content is fluctuating quite dramatically.
04:04 We're seeing it jumping up and down.
04:06 It's also dropping away quite sharply now.
04:09 We're seeing it drop down to 67%, 65%.
04:13 So this is the last thing we obviously want when the car is running at high load and high RPM.