Strage AFR spike at higher IAT

[doorider]

I'm seeing a strange AFR spike on my 300 when RPM goes over 8500 and IAT above 113F (45C). This is repeatable every single time, as soon as IAT touches 113F and RPM is above 8500 the AFR spikes by about half a point, even with no change in RPM or boost.

Has anyone come across something like this? The IAT compensation table isn't very helpful, it only has a few IAT cells but no reference to RPM so ya you can add fuel when IAT is above 113 but with that as soon as you go below 8500 RPM it goes rich until IAT goes below 113F. By default there is no specific change at 113F in the IAT table, there's one at 103 and then 140 so this drastic change in AFR doesn't seem to be related to this compensation table.

spike1.png

spike2.png

[Tbranella]

I'm seeing a strange AFR spike on my 300 when RPM goes over 8500 and IAT above 113F (45C). This is repeatable every single time, as soon as IAT touches 113F and RPM is above 8500 the AFR spikes by about half a point, even with no change in RPM or boost.

Has anyone come across something like this? The IAT compensation table isn't very helpful, it only has a few IAT cells but no reference to RPM so ya you can add fuel when IAT is above 113 but with that as soon as you go below 8500 RPM it goes rich until IAT goes below 113F. By default there is no specific change at 113F in the IAT table, there's one at 103 and then 140 so this drastic change in AFR doesn't seem to be related to this compensation table.

spike1.png

spike2.png

have you tried changing the IAT temp on the table?
are you doing anything for hull ventilation to get the hot air out of the hull or get cooler air to the intake?

personally I think it's much easier to see exactly what's going on with charts instead of graphs.

[doorider]

Yes, I've played with the IAT table. I can force more fuel when it reaches 113F but that causes too rich condition when RPM drops below 8500 while temps remain above 113. You can see in the first graph, RPM is slowly dropping but due to heat soak the IAT is not, just yet, but AFR returns to normal around 8500.

By default the IAT table has cell at 103F and 140F with 3% drop between them. It doesn't feel like this is what causes my AFR spike, it's just too sudden and exactly at 113F.

Yes I have extra vents.

This is very strange, there is nothing that I can see that could be telling the ECU to remove fuel when it reaches that IAT and RPM, unless there is some other trim table related to IAT/RPM which I don't see.

[Matty_OneUp]

What other channel are you data logging?
Are you 100% sure that its the IAT causing the spike and not something else?
Do you have a log file that you could share?
You can narrow the IAT table but if your saying it has no effect then it may be something else causing the spike and the higher IAT is just a coincidence?

[doorider]

I'm logging all available channels.

I don't see anything else that it could be. The first pic in this post shows RPM steady, pressure steady when AFR spikes, the only data that changes is IAT. Towards the end you can see RPM/pressure slowly coming down while AFR remains in the spiked zone until RPM drops below 8500.

The IAT table tweak is not great because it's a 1 dimensional trim so it doesn't care what RPM you're at. If I add fuel at 113F it will cause rich condition when RPM drops below 8500 but IAT remains above 113F until it drops below which is not quick.

Very strange.

[RUTHLESS]

i'm logging all available channels.

I don't see anything else that it could be. The first pic in this post shows rpm steady, pressure steady when afr spikes, the only data that changes is iat. Towards the end you can see rpm/pressure slowly coming down while afr remains in the spiked zone until rpm drops below 8500.

The iat table tweak is not great because it's a 1 dimensional trim so it doesn't care what rpm you're at. If i add fuel at 113f it will cause rich condition when rpm drops below 8500 but iat remains above 113f until it drops below which is not quick.

Very strange.

normal