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2009 (MY2010) S5 + APR Stage1
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63 Posts
Discussion Starter · #1 ·
I had the APR Stage 1 ECU and TCU remap about a year ago, and they recommended just having the 95 RON map as no one had warned me to run at least a couple of tanks of Shell 99 RON through, so the mix in the tank would affect the dyno run if they used the 99 map. They said I could return for the 99 map once I'd run a couple of tanks through.

So my questions are:
  • Is it worth going back for the install of the 99 RON map?
  • What if I fill up with non 99 RON? I'll always use Super Unleaded, but that may only be 97 or 98 depending on where I fill up, though I'll try to use Shell 99.
  • If I'll end up using a mixture of 99, 98 and 97 RON, would I be better with a different map? Say 97 (based on averages)?
  • If the worst came to the worst and I had to use 95, would that cause any problems, or just reduced performance until I filled with 99 again?
  • And finally, how much difference will any higher RON map make to BHP? The dyno run after Stage 1 install says I'm currently on 453.

Any thoughts or suggestions folks? Thanks.
 

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A higher RON allows the timing to advance and increase torque somewhat. If this increase is maintained at higher revs then peak power may increase too. So if a car has high octane fuel then a tuner can use a map to take advantage of it. Timing is critical because detonation must not occur too soon in the piston cycle which risks damage. So the engine has sensors which will detect any premature detonation and if they do the ECU will retard timing. But a map designed to be optimal with 95 RON will likely perform better than a map which has been optimised for 99 RON but is retarding on 95 RON.

So if you can mostly buy 99 RON then you’ll be best off with a map which has been optimised for it. You can then occasionally use 97 or even 95 RON and lose a bit of performance which will eventually get back to what it was after some time back on 99 RON. But with stage 1 you will not notice a huge difference in the new map. If you want more then it would be best to upgrade to stage 2, and only use 99 RON.
 

· Registered
2009 (MY2010) S5 + APR Stage1
Joined
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63 Posts
Discussion Starter · #3 ·
Th
A higher RON allows the timing to advance and increase torque somewhat. If this increase is maintained at higher revs then peak power may increase too. So if a car has high octane fuel then a tuner can use a map to take advantage of it. Timing is critical because detonation must not occur too soon in the piston cycle which risks damage. So the engine has sensors which will detect any premature detonation and if they do the ECU will retard timing. But a map designed to be optimal with 95 RON will likely perform better than a map which has been optimised for 99 RON but is retarding on 95 RON.

So if you can mostly buy 99 RON then you’ll be best off with a map which has been optimised for it. You can then occasionally use 97 or even 95 RON and lose a bit of performance which will eventually get back to what it was after some time back on 99 RON. But with stage 1 you will not notice a huge difference in the new map. If you want more then it would be best to upgrade to stage 2, and only use 99 RON.
Thanks for the detailed advice Dippy.
 
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