Last weekend, i came across a situation that has rarely happened to me over the last 5 years of karting, which, upon further reflection, prompted me to speak about it in the hopes of helping others on here which could run into it at some point or another, and i figured sharing some wisdom could help in avoiding potentially catastrophic failure on your engine.
I ran into a bad batch of fuel.
Preface: This happened in Lonato, Italy, over the course of Sunday the 14th of Jan.
As most of you know, the vast majority of “amateur” karting (ergo, outside of International Events) in the EU is done on pump fuel. More often than not, an organizer will designate a fuel station nearby the track within its competition regulations, take a sample of 98 octane fuel on the Friday of the race and use it as a baseline for fuel testing procedures. It is as such common practice for us to run 98 pump fuel during practice days as well, which is of course more economical but exposes you to the possibility of running into a product that is contaminated in one way or another, as the quality of the fuel depends on the amount of usage that the pumps receive (if there is a lot of traffic, the tanks will be filled more often and will as such provide fresh fuel more often than not), along with the reputability of the distributor itself.
Most of the time, when fuel is “contaminated”, it is by a too high amount of water / ethanol, outside of the range specified by the supplier (for reference, most 98 octane pumps provide fuel at 5% ethanol, at least in France / Italy).
The problems / symptoms of an over - ethanolized fuel are:
- The lack of capacity for the fuel to complete proper combustion and maintain a flame front which is fast enough to combust the mixture at/close TDC.
- Due to the above, unusually high EGT readings, especially the low EGT readings.
- EGT readings which do not react to carburation shifts : The logical approach is to richen the mixture when encountering abnormally high temps. With bad fuel, the richening of the mixture will more often than not have no impact on EGT values.
All of this leading to detonation, as the low combustion speed leads to sporadic combustion after TDC (which can be more or less severe). In my case, my piston looked like swiss cheese after two sessions.
This is very serious and can happen very fast. as the next step, if not remedied, is the piston beginning to disintegrate and throw aluminum pieces in your bottom end, potentially grenading your beloved engine.
The main takeaway of all of this to avoid issues is:
- Always keep an eye on your EGT temps, after every session.
- Check your piston surface after every two sessions. Not only does it help you with carburation, but it will also warn you of such a scenario.
-If you notice EGT values not moving even after big shifts in carburation, do not use the fuel in your jug anymore.
-If you notice heavy detonation, stop running immediately, and proceed with a piston change.
Hope this helps