Summary

Any thoughts on E85 versus petrol in regards to ignition timing? Yeah actually we've got a really neat little demonstration of ignition timing on E85 versus gasoline. If you jump on our YouTube channel and search for that, you'll find that but in short there's a lot of misconception around what we need to do with the ignition timing and a lot of this comes from the fact that when we're running on pump gas particularly under high load, particularly if we've got a boosted engine under high boost, generally we are going to be what I refer to as knock limited.

00:00 - Any thoughts on E85 versus petrol in regards to ignition timing? Yeah actually we've got a really neat little demonstration of ignition timing on E85 versus gasoline.
00:11 If you jump on our YouTube channel and search for that, you'll find that but in short there's a lot of misconception around what we need to do with the ignition timing and a lot of this comes from the fact that when we're running on pump gas particularly under high load, particularly if we've got a boosted engine under high boost, generally we are going to be what I refer to as knock limited.
00:32 What that means is we can't get to MBT timing because as we advance the timing we start to get to the onset of detonation.
00:39 So we end up with a very retarded map to protect the engine and make sure that it's not suffering from detonation or knock.
00:47 So when we go to E85 which has a higher octane rating, plus it also has much better cooling properties due to its latent heat of evaporation, we can then add more timing in when we're in the boosted areas of the map or the high load areas of the map.
01:02 Now that allows us to tune normally to MBT and that's where we see massive gains in performance when we go from pump gas to E85.
01:11 So we get this general conception out there in the market, in the industry that when we go from pump gas to E85, we need to add timing.
01:18 Now that does work like I've just explained where we are knock limited on pump gas however in the light load areas, what is easy to miss is that the burn speed, the combustion speed between E85 and pump gas is actually quite different.
01:33 E85 actually burns a little bit quicker so again just if you keep your mind back to our demonstration where we were talking about what we're trying to do with our ignition timing, we're trying to set the ignition timing so that peak cylinder pressure occurs at that optimal point, 16-18° after TDC.
01:51 Keeping that in mind, if the combustion speed is faster on E85, we actually need less ignition timing so in the light load areas where we can tune to MBT, generally we'll actually want to remove a little bit of timing when we go from pump gas to E85 so that's just something that a lot of tuners, even professionals out there in the industry don't understand and when they go from pump gas to E85, they just chuck an across the board 5° of additional timing at it, that's not what we want to do.
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