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Anomalous vibration occurs at around 5000 revolutions per minute.


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Greetings,

I have been fine-tuning the performance of my supercharged 1.6 engine on the road. I am using a donor engine with a fully undisclosed past, save for the fact that it had oil when I purchased it.


The vehicle is maintaining a consistent and stable performance in terms of reaching my Air-Fuel Ratio (AFR) objectives. However, the autotune feature is persistently attempting to increase the amount of fuel at 5000rpm and 140kpa.

I am genuinely perplexed over the cause of this. Regardless of the desired air-fuel ratio (AFR) or ignition timing, I failed to see this anomaly on my previous engine. I have experimented with ignition timing ranging from 11.8 to 12.3, as well as anywhere between 13.5 and 17 degrees, in these specific ranges. Autotune continues to inject more fuel in order to achieve the desired air-fuel ratio (AFR). Occasionally, a run may result in a rich mixture, leading me to suspect the presence of an intermittent issue.


The car is equipped with a coil on plug system, utilising BK7RE spark plugs with a gap of 0.8mm and 0.6mm. No noticeable change was seen between the two gap sizes. The problem persists when utilising the conventional ignition system and BK6RE spark plugs with a 1mm gap.
The injectors are EV14 with a capacity of 550cc.
The intake temperatures range from 20 to 40 degrees Celsius, which is within a reasonable and safe range.


I am open to any and all advise to improve the smoothness of this VE table. I am willing to test any suggestions.

I have received suggestions that the issue may be a misfire, but I have conducted tests on several ignition systems, plugs, and gaps, and I believe I have eliminated that possibility. What is the procedure for monitoring fuel pressure while in motion? The user's text is incomplete.The automobile has excellent performance and operates smoothly without any problems at higher revolutions per minute (rpm).

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Auto tune is a tool designed to assist you in reaching the correct range, but it is still necessary to accurately configure the map. Adjustments in each section of the graph need a considerable amount of time, making it mostly suitable for cruising and locations where the throttle is used lightly. You must use extrapolation techniques to the higher numbers more extensively, relying on logarithmic analysis and rigorous testing.

Since there is just one cell, I would simply manually adjust the value to make it smoother and complete the task. The cells located to the left and above are likewise incorrect, since they seem to be affluent.

Upon assessment, a significant portion of your table seems to be somewhat coarse and need further effort and refinement. The pressure of 90 kilopascals at 2600 revolutions per minute, for instance, is much more than the pressure in the next cells. The air-fuel mixture at 160 kPa and 4900 RPM is very lean.

You want a well-crafted and uniformly seamless VE table. By reducing the air-fuel mixture at lower revolutions per minute (rpm) below 100 kilopascals (kPa), you may optimise the fuel efficiency of your vehicle when cruising. As an illustration, I will provide my own example. Do not replicate it. Our final drives and gearing will vary, which will affect your cruising range. Our use case and configurations are also different, and the ECUs we use have distinct fuelling algorithms. However, this example provides an understanding of the level of smoothness you should strive for.

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It is not advisable to depend on AFR target tables for tuning. It is advisable to ensure that the VE table is as accurate as possible. Then, adjust the AFR target tables to align with the VE table. Finally, set the wideband authority to a small percentage to allow for minor adjustments, if necessary. The objective, however, is to ensure that the map is accurate and does not need any adjustments from the WB in order to get your desired outcomes. When using autotune with autotune, it is important to have accurate targets to guide adjustments to the VE table. Additionally, the WB PID calibration must be carefully set up to ensure smooth adjustments. Furthermore, the VE table should be consistent and free of irregularities to allow the WB to signal smooth adjustments. If there are significant deviations or erratic variations in the VE values, the wideband (WB) system will transmit substantial fluctuations to the autotune feature in an attempt to rectify the situation. However, if the PID (Proportional-Integral-Derivative) configuration is not adequately established, these signals will exceed the desired range and cause oscillations, leading to inaccurate adjustments in neighbouring cells.

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The table is quite coarse, I concur. Despite the many spikes on the table, the driving experience is unexpectedly smooth. However, I fully concur that the VE table requires significant more effort to get a smoother performance.

Thank you for the thoroughness of your answer and the VE table you provided. I will not replicate your VE table since I acknowledge that each engine and configuration is unique, which might impact the engine's efficiency.


My understanding is that I need to get some logs and manually adjust my VE (Volumetric Efficiency) in order to achieve my desired goal Air-Fuel Ratios (AFR). Striving to maintain a consistent table without fluctuations of 20 units, as it now has. Make sure that this table is positioned in close proximity to my objectives, and then activate the closed loop function, completely disregarding the VE auto adjustment capability.

I am somewhat perplexed by the use of target Air-Fuel Ratio (AFR) vs the Volumetric Efficiency (VE) chart. It seems that you are neglecting the target table while configuring the VE table. However, the target AFR table is used in determining the amount of fuel to inject, with VE also being taken into account.


A report on the underlying reason for the sudden increase in VE. I adjusted the fuel mixture of the vehicle to a higher richness level during my commute to work, specifically at a boost level of 11.5. This allowed me to optimise the performance by correcting the fuel mixture in the areas where it was too rich at 5000rpm. As a result, I was able to consistently achieve my desired performance goals, which was not the case while aiming a richness level of 12.


Tonight, I will focus on improving the overall smoothness of the table. Afterwards, I will implement closed loop control on the ECU, allowing for tiny real-time modifications. Would a range of 5-10% be suitable for this purpose?

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All the information provided is accurate.

The AFR target table does not play a significant role in the fuel calculation process. The purpose of using it is just to compute a correction factor that is applied to the current VE value when closed-loop fuelling is enabled. Open loop fuelling does not use it whatsoever. The fuel calculation mostly relies on your VE table, dwell/voltage offsets, and engine setup parameters, such as injector size and engine size.

It seems that you may have had a detonation or spark plug failure at those specific engine revolutions per minute (rpm). I would have anticipated its manifestation to occur throughout a broader variety of revolutions, however there is a possibility that my assumption is incorrect. 11.5 afr is far more secure. My vehicle is equipped with a turbocharger and designed for track use. However, it is specifically designed to achieve a wide open throttle (WOT) objective of 10.7 seconds at 10 pounds per square inch (psi) of boost pressure. This results in a power output of around 260 horsepower, thanks to the installation of a rather big turbocharger. In all honesty, I find this to be slightly excessive. I would prefer a range of 11-11.5 instead. However, I have confidence in my tuner. The only drawbacks are a slight increase in oil dilution, which can be mitigated by more frequent oil changes (which will be necessary anyway since it is a track car), and higher fuel consumption. On the positive side, I should experience lower cylinder temperatures and improved resistance to detonation.

A 5-10% level of authority seems accurate. The performance of my race car is around 5%, whereas that of my road vehicle is 10%. While some individuals, known as road tuners, may increase their speed by up to 25%, it is important to note that this approach is very ill-advised and lacks effort. It has the potential to be a significant and hazardous issue if a sensor were to malfunction, since it may lead to a substantial deviation from the real VE table. Consider the scenario when you are operating the engine at maximum power and suddenly the engine control unit (ECU) chooses to reduce the fuel supply by a significant 25%. This abrupt reduction in gasoline might potentially cause severe damage to the engine.

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Thank you for providing a clear explanation of the intended use of the target AFR table! Spending a significant amount of time on the video-sharing platform YouTube and an introduction to the concept of Electronic Fuel Injection (EFI). The HP academy course has not provided a good explanation of the topic.
I need to invest in a professional tuning session for my automobile on a dynamometer, but where is the enjoyment in that!

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The answer is contingent upon several factors, doesn't it? With enough study and effort investment, it is possible to achieve a level of proximity suitable for road use. If you want to optimise power, the only viable method is to use a dynamometer, since it allows for the visualisation of power curves.

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Now you see the reason why I hired someone to handle all the tasks for myself. Don't misunderstand me, I really like getting involved in hands-on labour and working on automobiles. However, it just appeared to be too demanding to do alongside my full-time job and my desire to fully enjoy the car.

I hope that you are able to successfully resolve the matter.

I have not personally experienced driving a SC mx5 without twin TB, however I have been informed that it produces a considerable amount of noise.

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There has been some progress made.

The reason for the poor drivability at low speeds is likely the presence of quite big gaps in the VE values, namely at 27, 35, and then back to 30 along the 27kpa axis. Those increases range from around 15% to 25% in proportion.

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