[Pete Schweaty]

A few weeks ago I put 4 gallons of E85 with my 93 octane. Car drove great and from the logs, the engine loved it. Today I filled up with 93, no E85. I put it on map 1, drove it a little to clear the auto tune, then put it to map 5. Take a look at the logs, they speak for themselves . . . ouch. Any ideas why it would pull so much timing? It is 48 degrees and I am at sea level. The first log is the one of E85+93. The next 2 are after the fill up on 93 alone.

Thanks

[Mike@N54Tuning.com]

With lower octane levels your advance needs to be much lower all else being equal. Looks pretty normal to me?

Mike

[Pete Schweaty]

Thanks. I will admit that I dont know much about reading logs. So the drop to around 4 or 5 degrees is normal?

[marv85]

You can;t expect to support the same timing with and without E85. You definitely expect your timing to be lower on average.

With that said, on map5 in theory, and after it autotunes you shouldn't be seeing timing drops (more than 3 in amplitude). What is the autotune boost?

[Pete Schweaty]

It looks like it was targeting around 14.5. With the E85 it was low 16's.

[marv85]

Originally Posted by Pete Schweaty

It looks like it was targeting around 14.5. With the E85 it was low 16's.

well if it targets 14.5 , it is basically like running map2. Try map 1, and see if your timing looks better. or just rely on the DME to retard your timing continuously

[Pete Schweaty]

Ok. Now granted, those were the first 2 runs after fill up. I will give it a day or 2 and log again. Does the DME always start out in the same spot, say 10 degrees, and then pull based upon feed back? The reason I ask, is I noticed that after it dropped to 5 degrees, it began to gradually climb back up to over 10.

[marv85]

Originally Posted by Pete Schweaty

Ok. Now granted, those were the first 2 runs after fill up. I will give it a day or 2 and log again. Does the DME always start out in the same spot, say 10 degrees, and then pull based upon feed back? The reason I ask, is I noticed that after it dropped to 5 degrees, it began to gradually climb back up to over 10.

the dme has a main timing table. it will to target a certain degree of timing per load and per rpm. if it thinks it is too aggressive it will pull out timing accordingly.
after the timing pull happens it will ramp timing back up gradually in an attempt to hit its targets

[Pete Schweaty]

Originally Posted by marv85

the dme has a main timing table. it will to target a certain degree of timing per load and per rpm. if it thinks it is too aggressive it will pull out timing accordingly.
after the timing pull happens it will ramp timing back up gradually in an attempt to hit its targets

Thanks.

[JC888]

If thats the first run after fill up, I'm not surprised that it looks like that. Its gonna take 3 pulls on map 5 to fully get the DME to adjust to the new octane, that's why you see significant timing drops. If you compare your logs from your 1st/2nd/3rd pull, you should see it gradually settles in on timing and target boost as it figures the octane level.

Also rather than looking at the graph, pull the csv file as its gonna give you a better picture of what's going on. I find that the graph just doesn't give you the resolution you need to figure out if its a 3degree drop of 5 degree drop.

Do a few more logs after it has time to re-learn the new parameters, the timing should smooth out quite a bit. Your target boost sounds about right as when I was on 92 oct, I would target around 14.5psi and when I was on e30 it would be around 17psi.

[Pete Schweaty]

Originally Posted by jcy335xi

If thats the first run after fill up, I'm not surprised that it looks like that. Its gonna take 3 pulls on map 5 to fully get the DME to adjust to the new octane, that's why you see significant timing drops. If you compare your logs from your 1st/2nd/3rd pull, you should see it gradually settles in on timing and target boost as it figures the octane level.

Also rather than looking at the graph, pull the csv file as its gonna give you a better picture of what's going on. I find that the graph just doesn't give you the resolution you need to figure out if its a 3degree drop of 5 degree drop.

Do a few more logs after it has time to re-learn the new parameters, the timing should smooth out quite a bit. Your target boost sounds about right as when I was on 92 oct, I would target around 14.5psi and when I was on e30 it would be around 17psi.

Yeah. It looks like it dropped a little less on the second run. Ill try it again in a few days.

[Mike@N54Tuning.com]

Originally Posted by Pete Schweaty

Thanks. I will admit that I dont know much about reading logs. So the drop to around 4 or 5 degrees is normal?

Sure. If the fuel is bad enough you can even get as low as 0 degrees advance. What happens with map 5 though is over time it will lower the boost targets until advance reaches a relatively stable point. I expect after a few more runs you'll see your boost drop maybe 1psi more to 14psi on the straight 93 and advance hang around that 5 degrees sloping up to 11 degrees level.

Mike

[JC888]

Not meaning to hijack the OP's thread but I need clarifying on reading fuel trims (which may also help OP understand more about reading logs). From a graphical standpoint, its the lower the line the better? smoothness? I can't tell what is good from bad. Again, I'm strictly talking about the "trims" variable.

I notice that the OP's graph where e85 shows the fuel trims to be near the top of the graph when the 1st/2nd are lower and it spikes differently.

Thanks.

[marv85]

Originally Posted by jcy335xi

Not meaning to hijack the OP's thread but I need clarifying on reading fuel trims (which may also help OP understand more about reading logs). From a graphical standpoint, its the lower the line the better? smoothness? I can't tell what is good from bad. Again, I'm strictly talking about the "trims" variable.

I notice that the OP's graph where e85 shows the fuel trims to be near the top of the graph when the 1st/2nd are lower and it spikes differently.

Thanks.

only thing you need to care about is the actual value which should be less than 30 (34 I think).

trims are the ability of the DME to compensate by adding or removing fuel to hit it's AFR targets. when you max out your fuel trims that means you will start missing your targets. If you max out in teh positive direction, that means you are at risk of going lean (depending on how much more fuel you needed). etc..

when you add E85 your trims will naturally go higher, and hence you have to monitor and make sure you don't max out. Else you need a flash tune.

you care about trims throughout a WOT pull...