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Old 03-04-2014, 08:36 AM   #142
bfrank1972
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Quote:
Originally Posted by steve99 View Post
for a tune designed for 93 octane obviously 93 would be fine

94 would be best as it has more knock resistance hence ECU will run full timing advance and produce best power, won't produce any more power as tune will produce this on 93 (assuming no knock encounter on 93, IAM should be =1 on 93 or 94.

91 will work but ECU will likely detect knock, reduce timing advance (IAM less than 1) thus reducing power. Won't damage anything but you will not get the maximum benefit from the tune.


even the factory tune is designed for 93 for max power, will run on 91 but at reduced power due knock retard IAM less than 1 in most cases.

IAM = Ignition advance multiplier can be monitored on OFT or other logging device if its less than 1 indicates knock encounted and ignition timing has been retarded by ECU (ie advance reduced) to compensate for lower octane fuel.
I was under the impression the OTS stage 1 tune was actually optimized for 91, not 93. Might actually be able to squeeze a little more out of 94 fuel.

Also regarding the OTS E85 tune, is there room for more timing advance for true E85? @shiv@vishnu says anything greater than E60 is fine, just wondering if he built in a large safety margin or if its that you just can't benefit from any further timing advance.

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