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Practical Standalone Tuning: Making Coarse Adjustments

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Making Coarse Adjustments


00:00 Since we've already coarsely adjusted both the fuel pressure and base ignition timing, we know these parameters are going to be close enough to let the engine start and idle.
00:09 As discussed previously, we'll need to revisit these settings once the engine is running, but for now we don't need to worry.
00:16 Since we've already set the ignition timing to 15 degrees, there's no chance we'll have any detonation in the idle areas we'll be tuning, so you can go ahead and forget about the ignition side of the mapping for now.
00:29 Keeping the engine running at this point may require you to use the throttle to prevent stalling.
00:34 Until the engine is a little more tuned and the idle parameters are configured, there's a pretty good chance that if you take your foot off the throttle, the engine will die.
00:42 This isn't a concern.
00:44 You want to use enough throttle to hold the engine RPM around the 1,000 to 1,500 RPM area while you're making your initial adjustments.
00:53 The fuel side of the mapping is probably going to need some attention.
00:56 This is the area we need to concentrate on during our initial start-up.
01:01 We want to make sure that our engine isn't running too rich or too lean, although at this early point the mixture window we want to aim for is pretty wide.
01:10 I like to see the engine run with a lambda value somewhere around .85 to .95.
01:17 To achieve this, we need an easy way to make quick coarse adjustments to our fuel map and how we can go about this will depend on the particular ECU.
01:26 Since our Motec M150 uses a VE-based fuel model, provided our IM lambda table and injector data are correct, we can change the actual air/fuel fuel ratio by adjusting the efficiency or VE map.
01:40 To affect an across-the-board change, I'll normally start by selecting a large block of the table that incorporates the area the engine is running in, then add or subtract from the block until the mixture matches my target.
01:53 We aren't trying to be exact here; that will come later.
01:57 For now, we just want to get the engine running cleanly so we can complete the configuration and set up.
02:03 If, on the other hand, your ECU uses a millisecond base fuel table, there are a couple of ways to coarsely adjust the fueling.
02:11 You can either adjust the base injector pulse width up or down, or if your ECU has an overall trim function, you can use this to get the mixture in the ballpark.
02:21 The overall trim feature is simpler and faster, but usually this will be limited to perhaps plus or minus 50%.
02:28 If this isn't enough to get the mixture correct, you'll need to change the base injector pulse width.
02:34 If you struggle to get the engine to initially fire up and run, you may also need to use these techniques to increase the fueling everywhere to get the engine started.
02:44 Remember while you're making these changes that the engine will be warming up.
02:49 The background compensations for startup and warmup enrichment will also be active in the background, so you can expect to see the mixture changing as the engine warms up.
02:58 Don't worry about this right now, but keep making adjustments if necessary to keep the mixture correct.

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