Hellcat IAT Corrections

[GenF-GTS]

I'm looking for IAT correction tables on a 2015 Dodge Hellcat, all I can seem to find is a hot table which is factory defined as 100c (212f) at which point it removes timing and a cold table which is factory defined as -10c (14f) this table is zero'd out.

On a GM platform normally you have IAT versus grams/cyl along with the RPM multiplier to give the table a 3rd dimension I'm not seeing that at all on the hellcat tune files.

This in my eyes is the equivalent to zeroing out a GM IAT table from 0-100c (32-212f) and only pulling timing after it reaches a 100c (212f) intake temp and nothing in between.

Am I looking in the correct spot here?
Have I missed something?
Will this platform ever have IAT corrections like a GM tune?

[GenF-GTS]

This is where I?m looking

[B00STJUNKY]

I suspect that it performs a linear interpolation between the cold and hot table. So, say your hot table removes 8* at 100c, and the cold table is set to 0 at the same breakpoint, then if your temps were 50c (halfway between 0 and 100), it would remove 4*.

[10_SS]

I suspect that it performs a linear interpolation between the cold and hot table. So, say your hot table removes 8* at 100c, and the cold table is set to 0 at the same breakpoint, then if your temps were 50c (halfway between 0 and 100), it would remove 4*.

I believe it works as described by B00STJUNKY. It has the same crappy tables as a 2010 HEMI Ram. Not a fan. The RAM file has cold set to -22F with positive spark values and hot at 194F with negative values.

[Mr.T]

Look at the "Hot Deadband" table. Based on my Jeep, I believe the axis of the Hot Deadband table is MAP and the values in the cells are the degrees of temperature change above the "Hot Spark REF IAT". It appears to work like this; when the temperature goes above the "Hot Spark Ref IAT" + the Hot Deadband for the current MAP, then it starts interpolating between the Hot Spark table and the Part throttle Base table based on the difference between "Hot Spark REF IAT" and "Part Throttle REF IAT". After some time period with temperature below the "Hot Spark Ref IAT" it appears gradually exit the Hot Spark mode and the timing matches the Part Throttle Base table.

Since the "Hot Spark REF IAT" is around 75C, this seems like this is for after/during heat-soak where the intake temps have risen pretty high.

Also, on mine there is a choice of whether the IAT source is actual IAT or MAT (calculated intake manifold air temperature), which is the OEM selection on mine and makes more sense. At lower air flows MAT is heavily influenced by ECT since the air has more time to absorb heat from the intake ports. Suspect yours is also MAT, but the selection isn't available. MAT should always be higher than IAT, but 100C sounds pretty high -- Just looked and my Jeep has 74C for the Hot Spark Ref IAT temperature (which is actually MAT).

,

Here's an example of how it appears to work after playing with values in the tables and logging data: Lets say the Hot Spark Deadband temperature is 3 degrees C at 90 KPA MAP, the "Hot Spark Ref IAT" (which is actually calculated MAT) is 73C, the "Part Throttle REF IAT" is 33C, and the Hot Spark table has -2.5 spark retard in the cell for 1408 RPM and 93 KPA. So if the MAP is 90 KPA and the temperature is above 76C (73+3), it enters Hot Spark mode and 2.5 deg is subtracted from the spark timing at that MAP. If the MAT drops to 53C, which is halfway between the 33C "Part Throttle IRT" and the "73C Hot Spark REF IAT", the timing is reduced by half the amount in the Hot Spark table.

It's tough reverse engineering how this stuff is done, take it with a gram of salt...

[Lidio Iacobelli]

Hey Guys,, wondering if you guys (Hemi tuners) may be able to help with re-scaling or reworking The IAT Spark on a Hellcat?

What I'm trying to do is the same Nitrous timing retard trick many guys out there (including myself) do where we short the IAT sensors to a resistor (with a switch when needed), and cause the IAT temps to go very high in an effort to achieve an adjustable spark retard while only "spraying" the motor and leave the timing alone when the inlet temps are normal and the NOS is off.

This IAT trick has worked for me even on a few Fords with Coyote motors and Shelby's too. What I usually do is find the correct resistor that will make the IATs go to about 215* or higher, and configure the tune so that you get all the normal IAT operation and spark retard (or adder) while under 200* temps, and then with the flip of a switch they are forced to pull what ever values I set in the tables on anything over about 215* IATs. This give us the best of both worlds for spark with and with-out NOS usage.

I've already figured out on a Hellcat that this IAT trick does work for sure by adding resistors to both of the Post intercooler IAT sensors that are in the MAP's. I've already tested it with no Nitrous flowing yet, and it works flawlessly so far with out causing any other changes in the Tuning while making pulls at WOT. And it'll pull the max spark negative values that are set in the HOT spark tables when it sees about 215* temps after shorting the sensor. I was really worried that faking the IATs to go so high would cause other tuning issues, but it didn't at all. The WOT A/F and all did exactly as it normally would even as the IAT's went over 210*. So this was a relief.

The problem I'm having is the IAT hot/cold-spark tables on this Dodge stuff are no where near as easy to use as the GM and Ford stuff.
What I'm chasing is; I want the IAT hot-spark tables to only pull about a total of 3 to 4* timing as the inlet temps legitimately work there way up to about and 160* air temps.

But I would like to have the option of pulling as much as 8-10* timing when I "spray only". And if I key in about -8* in the bottom rows of the hot spark table,, it pulls all of that as it approaches about 160* temps at the end of a 1/4 mile run,, and this is to much retard for me (with boost only) since this car is on e85.

What I'm wondering is if the IAT "reference" values can be played with (re-scaled) in order to try to set this up to pull no more then about 4*-5* timing as the IAT would normally get just over 150* temps or so,, and then allow it to retard as much as 10* or so if needed only when the IAT gets up to or past 215* (per the resistor trick).

Thanks

[zhc]

Hey Guys,, wondering if you guys (Hemi tuners) may be able to help with re-scaling or reworking The IAT Spark on a Hellcat?

What I'm trying to do is the same Nitrous timing retard trick many guys out there (including myself) do where we short the IAT sensors to a resistor (with a switch when needed), and cause the IAT temps to go very high in an effort to achieve an adjustable spark retard while only "spraying" the motor and leave the timing alone when the inlet temps are normal and the NOS is off.

This IAT trick has worked for me even on a few Fords with Coyote motors and Shelby's too. What I usually do is find the correct resistor that will make the IATs go to about 215* or higher, and configure the tune so that you get all the normal IAT operation and spark retard (or adder) while under 200* temps, and then with the flip of a switch they are forced to pull what ever values I set in the tables on anything over about 215* IATs. This give us the best of both worlds for spark with and with-out NOS usage.

I've already figured out on a Hellcat that this IAT trick does work for sure by adding resistors to both of the Post intercooler IAT sensors that are in the MAP's. I've already tested it with no Nitrous flowing yet, and it works flawlessly so far with out causing any other changes in the Tuning while making pulls at WOT. And it'll pull the max spark negative values that are set in the HOT spark tables when it sees about 215* temps after shorting the sensor. I was really worried that faking the IATs to go so high would cause other tuning issues, but it didn't at all. The WOT A/F and all did exactly as it normally would even as the IAT's went over 210*. So this was a relief.

The problem I'm having is the IAT hot/cold-spark tables on this Dodge stuff are no where near as easy to use as the GM and Ford stuff.
What I'm chasing is; I want the IAT hot-spark tables to only pull about a total of 3 to 4* timing as the inlet temps legitimately work there way up to about and 160* air temps.

But I would like to have the option of pulling as much as 8-10* timing when I "spray only". And if I key in about -8* in the bottom rows of the hot spark table,, it pulls all of that as it approaches about 160* temps at the end of a 1/4 mile run,, and this is to much retard for me (with boost only) since this car is on e85.

What I'm wondering is if the IAT "reference" values can be played with (re-scaled) in order to try to set this up to pull no more then about 4*-5* timing as the IAT would normally get just over 150* temps or so,, and then allow it to retard as much as 10* or so if needed only when the IAT gets up to or past 215* (per the resistor trick).

Thanks

Yes, you can re-scale it to do what you're asking for. Note that by default, it's going to use "Manifold Air Temp" though, not IAT. Manifold Air Temp is basically IAT adjusted by ECT so usually MAT will be higher than actual IATs. Although, in your case when you engage the resisters, MAT might actually read lower than the faked IAT readings you're getting if IAT is higher than ECT. I think you can switch it between using IAT or MAT in the latest Beta but I haven't tried it myself.

As for rescaling, the three values you want to change are "Part Throttle Ref IAT", "Hot Spark Ref IAT", and "Cold Spark Ref IAT". Also note the dead band value which is 32F by default. What this means is that there's a middle area, the dead band, where it won't pull any timing. After the dead band (should be 16F after the mid point between Hot and Cold Ref IAT), it will start pulling timing and ramps up linearly to the max timing you have set in the hot spark table where max timing pulled will occur at whatever the "Hot Spark Ref IAT" is set at. I'm 90% sure this is how it works and have had success re-scaling it on Hellcats based on this understanding.

[Lidio Iacobelli]

zhc,

Thanks for your help. If I may kindly ask,, based on what I'm trying to do - As a starting point, where would you set or re-scale these IAT settings to achieve what I've described I'd like to try to have happen? With and with out the resistor trick.

Hate to sound stupid, but with out seeing this one on a illustration or table, I'm having a tuff time with it : (
I'd like to leave the setting/source on "MAT" and not switch that for now in case it opens a can of worms. I've attached a screen shot of a 1/4 mile run log of my car recently on e85 and no NOS yet, and you can see where I highlighted all the Post intercooler air temps. On a warm Michigan day this weekend they reached about 150* on this particular log,, but they've gone over 160*+ on others. Not to worried about these temps.

I'd like to try to set it up to not let it pull more then about 2-3* as it approaches 160* inlet temps or so,,, and then I've got the resistors set up to make the post IAT's go up to about 215* or so with the flip of a switch, so once its over or around 215* IATs (for NOS) I'd like to configure it to pull about 8* to 10 degrees or so.

Thanks again in advance for any help! Really appreciate it.

[06300CSRT8]

Sorry for metric to imperial conversion....

And for a caveat I have never tried this, but based on this thread, this is how I would attempt it.

Set the Hot Spark Ref IAT to 200F
Set the Cold Spark Ref IAT to 190F
Populate the Hot Spark table with what timing you want pulled for NOS (8 to 10 degrees)
Populate the Cold Spark table with what timing you want pulled for no nitrous

At 190 or cooler IAT, you should get timing pulled according to the cold spark table
Between 190 to 200, it should blend between the hot and cold spark tables
At 200 and above, should get timing pulled according to the hot spark table.

[Lidio Iacobelli]

Sorry for metric to imperial conversion....

And for a caveat I have never tried this, but based on this thread, this is how I would attempt it.

Set the Hot Spark Ref IAT to 200F
Set the Cold Spark Ref IAT to 190F
Populate the Hot Spark table with what timing you want pulled for NOS (8 to 10 degrees)
Populate the Cold Spark table with what timing you want pulled for no nitrous

At 190 or cooler IAT, you should get timing pulled according to the cold spark table
Between 190 to 200, it should blend between the hot and cold spark tables
At 200 and above, should get timing pulled according to the hot spark table.

This is very helpful and really appreciate all the help!
I will be trying all of this very soon.... should I populate the "Cold Spark" tables with negative or positive numbers? Don't want to go in the wrong direction and accidentally add unwanted spark under load. I assume negative values?

Thanks

[06300CSRT8]

Populate with negative so it pulls timing.

[Lidio Iacobelli]

Sorry for metric to imperial conversion....

And for a caveat I have never tried this, but based on this thread, this is how I would attempt it.

Set the Hot Spark Ref IAT to 200F
Set the Cold Spark Ref IAT to 190F
Populate the Hot Spark table with what timing you want pulled for NOS (8 to 10 degrees)
Populate the Cold Spark table with what timing you want pulled for no nitrous

At 190 or cooler IAT, you should get timing pulled according to the cold spark table
Between 190 to 200, it should blend between the hot and cold spark tables
At 200 and above, should get timing pulled according to the hot spark table.

Wanted to report back that so far the values you recommend I try for; Hot Spark / Cold Spark appear to be working !

Iv'e not been able to get the inlet temps much above 130* yet to see what it will do exactly with the timing as it goes from 115* to about 150*+ eventually on boost only, but it appears to be good so far.
And the new "hot-spark" / NOS retard table clearly works when "jumped-only" and the IATs artificially go past about 210*. As a test I set it up to pull -15* in the entire Hot Spark table and when I hold it at about 2000rpm and flip the switch,, it goes from about 120* inlet temps to about 215* and the timing drops from about 30 degrees to about 15 degree timing.. And it appears to not change the commanded Lambda or anything else in the tune while running.

So it looks like we may have a viable solution for spark retard under NOS conditions on the (2) Post IAT equipped Hellcat's.

Thanks again for all the help with this and I'll post a log soon of it in action.

[AlphaCat]

My multiplier is set to zero. Is that relevant. If zero does this table even pull timing? Where is the MAT sensor? Should I set it to IAT?