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Hi all,

I'm unsure which MHD stage 2 map to use for my car. The map options are:

  • 91 Octane / 95 RON
  • 93 Octane / 98 RON
  • 95 Octane / 102 RON
Where I'm getting stuck is the RON vs Octane dilemma. It seems fuel providers in the UK kinda mix an match quoting RON & Octane on their products. For example V-Power is quoted as 99 RON, but on the pump is says 99 Octane... so which is it? And beyond that, 99 doesn't match any of the maps perfectly.

So, this leads me to part 2 of my question. How important is it to run the correct fuel for the map? Is it just going to be a performance issue or is there a risk of damage? If just a performance deficit, how much of an impact are we talking?

Thanks in advance for any help!
 

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93/98 for V Power and the like, 91/95 for standard. However, you do need to log and make sure your corrections are OK and you are not getting knock etc. even though you have selected the correct map. You may have to run the 91/95 map even on Super to be safe.
 

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The short answer is, always map for 95 and put 99 in the tank.

The longer answer is, if you're going to home map your car with MHD, you should at least spend the extra £80 and get the monitoring pack. Then you can fully log your engine's output parameters and performance. This way you'll know if the map you're running matches the fuel you're putting in. In general, if you use off-the-shelf maps specified for using 99 fuel, you'll get a lot of timing corrections - even if you're using 99 fuel - and the DME will pull so much timing, you'll get less real-power than choosing a 95 map and getting less corrections. That make sense?
It's basically because the OTS maps will be overly optimistic for the fuel quality we get here.
 

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as above, map for 95 and use 99, for reference on my m140i when using MHD the 98 ron map only made literally a few more bhp than the 95ron map, the 98 ron map however had a load of timing corrections.

So, use 95 map, use 99ron fuel and you have more margin of safety and not any real world performance differences
 

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Well I didn’t know this. I was using the 98 Ron setting thinking this was the closest to VPower rating and have been since 2018.
I’ve now switched over to 95 for hopefully long term health 😀
Odd however a higher setting RON map, presumably suited for the fuel you’re using would cause corrections.
 
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