Discussion and questions related to the course Practical Dyno Tuning
I have a question for you, I know you said that most engines will normally run with little change in performance over a relatively wide span of AFR's but I was just wondering if using your target numbers is what we as tuners should be aiming for all the time when tuning the AFR on an engine.
What I mean is, I did not see you referencing the AFR to say power or torque either while tuning steady state or wot.....you were basically just concerned with meeting your target numbers and that was it.
Is it fair then to say that when tuning in general the only time we really use the dyno to see changes in engine performance is when tuning the ignition?
Great question and I may not have really clarified this through the practical course. The practical dyno course is designed to show you how to achieve tuning changes, but not necessarily what numbers to use. Is far as the air fuel ratio goes, no you shouldn't be trying to apply a single AFR for every engine. The targets I use in the course are pretty typical and a good starting point. Of course you may want to try adjusting the AFR richer or leaner and see what your particular engine wants.
The AFR will effect the combustion temperature and in some instances with engines that are heavily knock limited, it can be beneficial to use a richer mixture to cool the combustion charge and allow additional ignition advance without knock.
If you want a thorough understanding of how the AFR affects the engine performance, and how to decide what particular AFR your engine wants, our Understanding AFR course is a great option.
After we done doing VE table and matching our target AFR, if we want to make fine tune on how much AFR our engine need, we just simply modify the AFR target table and the actual AFR will follow. Right?
How to do steady state tuning on cars with Automatic transmission which we cant hold specific gear number since kick down always an issue?
If you're tuning an ECU that uses a VE fuel model then yes, you can make changes to your AFR by changing the mixture aim table rather than adjusting the VE table - This is provided the injectors are modelled correctly and you've done a good job of tuning the VE table in the first instance.
Automatic transmissions do present some issues. Generally I will lock the transmission into a lower gear or place it in manual mode to prevent it kicking down. This will usually still result in the torque converter flaring which makes it hard or impossible to access some of the very low rpm high load sites. The point here is if we can't drive in these cells on the dyno then we won't be able to access them on the road either so it's not that critical. If I can't tune a particular site like this I will tend to follow the current trend or shape of the fuel table into the zones I can't reach.