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Re: General SBK Discussion Thread
I by no means am an expert on this, but here are my 2 cents:
Theoretically the answer to your questions is Yes.
In simple terms let me define 3 states an engine can be in in terms AFR (Air/Fuel) tuning.
1) Lean. More Power, Runs Hotter
2) Optimal (Stoichometric ratio or 14:1 ratio air to fuel)
3) Rich. Less Power. Runs Cooler.
As you can see there is Pro and Con to being Rich or Lean tuned. The idea is during combustion, some un-burnt fuel touches the mechanical bits of the cylinder, exhaust port etc and being a liquid adds a cooling effect. Hence Richer mixture run cooler than Lean.
Now, one would think that by default all bikes from the factory will be at the optimal ratio from the factory at all revs. This is not the case. Manufacturers tune their bikes to behave differently at different revs. Just as an example, on a street bike a manufacturer can tune a bike to be leaner at low revs for better response, but make it richer at higher revs to run it cooler. Such a bike will have comparatively lower peak power figure by an X% then the absolute best it can be. Now similarly a manufacturer going for peak numbers can tune a bike richer at lower revs to run cooler considering many bikes in city spend time in lower revs and go lean on higher revs for higher peak power knowing bikes dont spend much time at higher revs.
It depends on the bike and the manufacturer and the application of the bike that decided how a bike is tuned through its rev range. While tuning ourselves, we can choose to modify the tune according to our application as well. For example for my track bike which will spend considerable amount of time at high revs, I might make it a bit richer at higher revs, at the cost of peak horse power.
I hope this helps.
Rachit
Originally posted by Andy_kristine
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Theoretically the answer to your questions is Yes.
In simple terms let me define 3 states an engine can be in in terms AFR (Air/Fuel) tuning.
1) Lean. More Power, Runs Hotter
2) Optimal (Stoichometric ratio or 14:1 ratio air to fuel)
3) Rich. Less Power. Runs Cooler.
As you can see there is Pro and Con to being Rich or Lean tuned. The idea is during combustion, some un-burnt fuel touches the mechanical bits of the cylinder, exhaust port etc and being a liquid adds a cooling effect. Hence Richer mixture run cooler than Lean.
Now, one would think that by default all bikes from the factory will be at the optimal ratio from the factory at all revs. This is not the case. Manufacturers tune their bikes to behave differently at different revs. Just as an example, on a street bike a manufacturer can tune a bike to be leaner at low revs for better response, but make it richer at higher revs to run it cooler. Such a bike will have comparatively lower peak power figure by an X% then the absolute best it can be. Now similarly a manufacturer going for peak numbers can tune a bike richer at lower revs to run cooler considering many bikes in city spend time in lower revs and go lean on higher revs for higher peak power knowing bikes dont spend much time at higher revs.
It depends on the bike and the manufacturer and the application of the bike that decided how a bike is tuned through its rev range. While tuning ourselves, we can choose to modify the tune according to our application as well. For example for my track bike which will spend considerable amount of time at high revs, I might make it a bit richer at higher revs, at the cost of peak horse power.
I hope this helps.
Rachit
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