Road Tuning: Transient Fuelling
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Transient Fuelling
04.01
| 00:00 | - Transient fuelling refers to acceleration enrichment which is essential if you want an engine that responds smoothly to sharp changes in the throttle position. |
| 00:09 | The parameters available to you will depend on the brand of ECU you are using, and we are going to look at the key parameters the Link G4+ uses to address this. |
| 00:20 | We can start by heading to the accel enrichment menu. |
| 00:24 | Most of the parameters won't actually need to be adjusted here and for simplicity we will deal with the important adjustments only. |
| 00:33 | The G4+ includes a parameter called Accel sensitivity which defines how sensitive the accel enrichment will be to changes in throttle position. |
| 00:43 | A larger number here results in more enrichment for a given rate of throttle change. |
| 00:49 | This works in conjunction with the Accel clamp table which allows the amount of acceleration to be adjusted with regard to engine rpm. |
| 00:58 | At low rpm, airspeed is slower and we generally need more accel enrichment than we do at high rpm. |
| 01:06 | This table allows the accel enrichment output to be optimised throughout the rev range. |
| 01:13 | Two further tables are also included in the Link G4+ to give even more control. |
| 01:19 | Accel cold correction allows the accel enrichment to be increased when the engine is cold, and Accel load correction allows the accel enrichment to be adjusted dependent on engine load. |
| 01:31 | Each parameter will need to be tuned to suit your particular engine, although I find that the default parameters are usually pretty close. |
| 01:39 | This means you aren't gonna be starting from scratch and it speeds up the process. |
| 01:45 | I tune the accel clamp table by driving the car in 2nd or 3rd gear at each rpm in the accel table and testing the response when the throttle is stabbed open. |
| 01:56 | You want to watch what the air fuel ratio does, as well as feel how the car responds. |
| 02:02 | While the air fuel ratio may show up problems with accel enrichment, often the response is not fast enough to truly show what's happening. |
| 02:11 | Basically I'll adjust the enrichment numbers based on what I'm seeing on the air fuel ratio meter and what I'm feeling. |
| 02:19 | If we don't have enough accel enrichment, you will feel a hesitation and see a lean spike on the air fuel ratio meter. |
| 02:26 | If you have too much accel enrichment, the engine may bog and you should see a rich reading. |
| 02:33 | Adjust each rpm zone until you have smooth and clean acceleration performance. |
| 02:39 | You may notice that above 5,000 rpm you have little or no acceleration enrichment. |
| 02:45 | This is pretty typical since air speed is so high at these rpms and additional enrichment isn't necessary. |
| 02:53 | Next we can look at the decay rate. |
| 02:56 | Often this doesn't need to be touched, but if you notice that the air fuel ratio is initially good as you open the throttle, but then moves either rich or lean, you can alter the decay time to fix this. |
| 03:08 | You are looking for a nice smooth transition in the air fuel ratio from your normal cruise mixture to the wide-open throttle target mixture. |
| 03:18 | Lastly we can change the sensitivity if necessary. |
| 03:23 | The aim here is to only bring in the accel enrichment when it's truly needed. |
| 03:28 | If the sensitivity is too high, you may end up with unwanted accel enrichment during small changes in throttle position. |
| 03:35 | If it's too low, you may find that moderate changes in throttle position result in a slight bog or doughy response from the engine. |
| 03:44 | My advice is to use data logging to check what level of accel enrichment is being delivered, and drive the car over a range of situations, varying your throttle position. |
| 03:54 | Look for areas where the engine doesn't respond smoothly. |
