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Practical Standalone Tuning: Optimising Your Tune on the Dyno

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Optimising Your Tune on the Dyno

06.48

00:00 - Since we've already spent a lot of time doing the steady state tuning, we'll already have a lot of our full throttle map pretty well tuned.
00:07 If you've followed the 10 step process so far, we should have an engine that is tuned in steady state up to about 5000 RPM.
00:15 This means we only really need to complete the full power tuning above this point.
00:20 As with steady state tuning, we want to start with a rich mixture and retarded timing, and slowly creep up on the tune to ensure a safety margin while we get started.
00:30 This might sound like a difficult task when we have no real idea what the engine may want, but there are a few tricks we can use to make an educated guess about the map.
00:39 Since we've already tuned the full throttle section of the map up to 5000 RPM, we'll already have a good idea of the shape of the fuel map so far.
00:47 I would follow this general shape and extend it outwards to the higher RPM ranges.
00:53 When you do this, make sure that you aren't just copying the 100 kPa full load row as often a restrictive intake will drop manifold pressure slightly at higher RPM which can have the ECU interpolating between two rows.
01:06 I'll also add 2% to 3% more fuel into the top two rows of the fuel map for my initial full power pulls, just to make sure I'm going to be safely rich.
01:17 Now we can look at the ignition map.
01:19 As with the fuel map, this should now be pretty well optimised out to about 5000 RPM.
01:25 We've also copied the timing from the 5000 RPM column across to fill in the remainder of the table.
01:32 Before we start doing a full power run though I'll highlight the entire two rows of the ignition table at the top and remove two degrees timing for safety.
01:41 We're now ready to do our first ramp run.
01:44 For our first run we're only going to cover the section of the map that we've already tuned.
01:50 I'm going to set a start RPM of 2000 RPM, a finish RPM of 5000 RPM, and a run length of six seconds.
01:59 If we've done our job properly there should be no danger at all and we should just be a little bit rich.
02:05 It's important at each step of this process, to listen carefully for any signs of detonation although at this early stage, we know we should be safe here.
02:14 Once we have our first run completed and everything's looking good, we can start to increase the run RPM.
02:21 I like to increase the runs by 500 RPM at a time which lets you start to creep up on the areas of the map that aren't tuned yet without too much risk.
02:30 So our next run is gonna go to 5500 RPM and take 6.5 seconds.
02:36 At this point, provided there's no sign of any detonation, I'm only going to concentrate on adjusting the fuel map.
02:43 We'll deal with the ignition timing once we have the fuel map dialled in perfectly.
02:48 Basically we want to perform a run, check the air fuel ratio, and perform any necessary correction to the fuel map using the have over want equation.
02:59 When making these changes we want to adjust the top two rows of the fuel map to account for any interpolation as well as extrapolating these changes out into the next RPM zone so the tune's going to be close when we increase the RPM.
03:14 Once we've made any necessary changes, we can do another run to confirm the air fuel ratio now matches our desired target.
03:23 Once our AFR is on target, we can again increase the RPM by 500, and move further into the untuned area of the map.
03:31 We just repeat this process until we've reached the engine red line.
03:36 When you're performing these ramp runs, we want to be watching the air fuel ratio display on the dyno very carefully.
03:43 If the mixture starts to move lean, abort the run by hitting the clutch and backing off the throttle so you can fix the problem and try again.
03:51 Never under any circumstances touch the brake pedal on the dyno.
03:56 A well tuned fuel map should be reasonably smooth and show the same general shape as the engine's torque curve.
04:03 If your fuel map looks something like this, then you're probably on the right track.
04:08 Just a note here about map resolution, while the 500 RPM increments we used when we initially configured the fuel table are generally fine, if your engine has large changes in VE across a narrow RPM range, you may find it difficult to get good control of the AFR.
04:26 In this instance it can be worth adding an extra RPM range to help provide better resolution at this point.
04:34 Once we have the fuel map perfectly tuned, it's time to adjust the ignition map.
04:38 This needs to be approached carefully as detonation can quickly damage your engine.
04:44 If at any time you hear detonation, abort the run immediately and remove two to three degrees of timing before trying again.
04:52 To optimise the ignition table we want to use the MBT tuning method, and increase timing until we see no increase in torque just like we did in the steady state section.
05:03 We do this by doing a base run that we can use as a baseline comparison.
05:07 We then add two degrees timing to the top two rows of the ignition map, and perform another run.
05:14 If we see the torque increase throughout the run, we would add another two degrees and try again.
05:21 Usually what you'll see is that through some sections of the rev range, the torque won't increase.
05:27 If this happens we know we've reached MBT timing and we can remove the extra timing from these areas.
05:34 If there are areas of the rev range that the torque does increase though, we would want to add a further two degrees to these areas and try another run.
05:43 Following this process we can quite quickly build up and optimise our ignition timing map.
05:48 When you're close to having the map optimised, you can make smaller changes of one degree until you don't see any further improvement in torque.
05:56 With a well tuned ignition map you should see smooth changes in the ignition timing numbers.
06:03 Large or erratic jumps in ignition timing will result in poor drivability, flat spots, and hunting.
06:09 As a rule, I don't expect changes of more than five to six degrees between adjacent cells in an ignition map.
06:15 Your finished ignition map should look something like this.
06:20 Once we have our full power tune completed, you may also like to make some more runs with the slightly richer and slightly leaner air fuel ratio, to check how the engine responds to changes in fuelling.
06:31 This can help you decide what air fuel ratio to choose.