Thoughts on IAT/ECT tables
08-13-2011, 04:25 PM
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Thoughts on IAT/ECT tables So I've bought a very popular, widely respected mail-order tune for my 08' GXP. Part of his tuning process is essentially deleting the spark adjustment tables for the IAT and ECT. I've thrown this by a few people and they basically have told me that is crazy to do and dangerous. I've been driving on this tune now for quite some time and I haven't noticed any knocking due to high IAT/ECT, I confirmed this by scanning for about 2 hours (5 mb of data), there was some random steady state knock I found but it was at cruise so I'm assuming it's over sensitive knock sensors. Otherwise WOT was OK and even as the IATs approached 190 deg still didn't get any additional knock. I mean this was a 90+ degree day, no humidity and me doing WOT runs down a random road. If there was a day to see the impact on removing IAT/ECT tables this was it.
The car has been dynoed after the mail-tune, IAT/ECT was disabled during the tuning process so I'm a little worried about total timing. On the dyno it would make sense to me because you wouldn't want to add base timing against an IAT/ECT table pulling it across different cell ranges. If you take the tables up in timing until knock and back off a few degrees for safety then reimplement the IAT/ECT it should be safe. Putting the IAT/ECT back in would ensure the OE safety net for temp increases.
Example: stock timing reduction for a random point say .88 g/cyl @194 deg F is -12 degrees, that same point on the new tune is zero. So basically on that 190 deg IAT day I was running +12 degrees of timing.
In my mind, using an engineering train of thought, I'm adding 12 degrees of timing in conditions that aren't suitable for that much heat/pressure. How could the OEM be that far off to justify removing these tables entirely? I can see them being very conservative maybe but removing them sounds risky.
I wonder how my total timing is impacted if it was dynoed with no IAT/ECT?
I think what is keeping me a little on the safe side is that the stock plugs have been swapped for half a range cooler plug TR60 vs 55s and I'm also at a relatively high altitude (4500ft).
I have stock vs current files if anyone is interested.
The car has been dynoed after the mail-tune, IAT/ECT was disabled during the tuning process so I'm a little worried about total timing. On the dyno it would make sense to me because you wouldn't want to add base timing against an IAT/ECT table pulling it across different cell ranges. If you take the tables up in timing until knock and back off a few degrees for safety then reimplement the IAT/ECT it should be safe. Putting the IAT/ECT back in would ensure the OE safety net for temp increases.
Example: stock timing reduction for a random point say .88 g/cyl @194 deg F is -12 degrees, that same point on the new tune is zero. So basically on that 190 deg IAT day I was running +12 degrees of timing.
In my mind, using an engineering train of thought, I'm adding 12 degrees of timing in conditions that aren't suitable for that much heat/pressure. How could the OEM be that far off to justify removing these tables entirely? I can see them being very conservative maybe but removing them sounds risky.
I wonder how my total timing is impacted if it was dynoed with no IAT/ECT?
I think what is keeping me a little on the safe side is that the stock plugs have been swapped for half a range cooler plug TR60 vs 55s and I'm also at a relatively high altitude (4500ft).
I have stock vs current files if anyone is interested.
08-13-2011, 05:02 PM
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If you don't have the car full time it's impractical to set up the spark
adders. But I've used them to deal with ping with A/C on, where the
ECT would run up. Eventually I improved the cooling but it got me by
with stock radiator.
If you're boosted, IAT is going to be all over the place and it's going
to lag reality by a fair bit - too late to help, but hangs around afterward
and drinks your beer. Not sure what people do for that.
Modding fundamentally alters what the motor can take for timing, and
the stock setup is no gem to begin with. The only thing I can see is
cut-and-try, which at shop rates you wants none.
adders. But I've used them to deal with ping with A/C on, where the
ECT would run up. Eventually I improved the cooling but it got me by
with stock radiator.
If you're boosted, IAT is going to be all over the place and it's going
to lag reality by a fair bit - too late to help, but hangs around afterward
and drinks your beer. Not sure what people do for that.
Modding fundamentally alters what the motor can take for timing, and
the stock setup is no gem to begin with. The only thing I can see is
cut-and-try, which at shop rates you wants none.
08-13-2011, 07:03 PM
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Not sure what you mean by have the car all the time, its a dd so its driven often. Car is n/a, for now.
My post is kind of run on and hard to follow, just want to know what ppls thoughts are on removing iat/ect spark maps...
My post is kind of run on and hard to follow, just want to know what ppls thoughts are on removing iat/ect spark maps...
Last edited by redlightrampage; 08-13-2011 at 11:03 PM.
08-14-2011, 07:58 AM
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It's just the standard K&N CAI Intake for the LS4, 63-3059 P/N, it's up behind the front left headlight. There is a heat shield which does OK for a while but it still seems to succumb to the heat. I'm probably going to end up boxing it off completely.
I just realized those were mainly idle temps, it did take about 15 minutes of driving though to bring them back down to 100 which was ambient plus about 10 which isn't bad. As long as I was moving they stayed fairly cool. I guess making sense of this now I probably would rarely see the temps where the engine begins to start pulling a ton of timing so I could just zero out the cells that impact like the other guy said
I just realized those were mainly idle temps, it did take about 15 minutes of driving though to bring them back down to 100 which was ambient plus about 10 which isn't bad. As long as I was moving they stayed fairly cool. I guess making sense of this now I probably would rarely see the temps where the engine begins to start pulling a ton of timing so I could just zero out the cells that impact like the other guy said
