Why do you take timing out when IATs climb? So your engine doesn't detonate and blow up the nice shiny stuff inside your long block. This is obvious, right? Okay, but at what point should we start removing timing due to IATs, and how much timing do we remove? The downside to retarding timing is higher EGTs and less power. Go too far one way (advance) and you detonate, go too far the other (retard) and you melt stuff.
At least with VEMS, this table is very simply laid out:
- iat ign retard
- iatret.jpg (124.28 KiB) Viewed 9495 times
This is how I used to have my 30r setup. I was very weary of intake temps and have a feeling it contributed to my last engine's detonation problems. Since upgrading my intercooler and intake setup, I've reduced my IATs and have subsequently adjusted the amount of timing the ECU will pull from the base timing map.
New Treadstone vs old CXRacing intercooler:
- iattrvscx.jpg (99.79 KiB) Viewed 9494 times
I recently found a table from the Evo guys, this is how their stock ECU pulls timing:
- EVO ignRtd_vs_airTemp.gif (4.39 KiB) Viewed 9495 times
This is clearly where dyno tuning helps the calibrator in that he can see MBT (or as much timing as possible before MBT due to knock) and hear detonation/preignition. If det, pull timing. It may be that one just cannot run over a certain amount of boost - Marc tuning the billet k26 on the small #6 hotside, for example. If I recall, intake temps went off the "acceptable" limit at a certain boost regardless of timing. But what if you're unable or don't have the funds to get on the dyno right away? Suck it up, gotta pay to play? Or are there some very general guidelines out there?
So at what temperature do YOU start pulling timing, and how much? How high of temperatures is too much? What is simply too little timing? Is there a certain number or range that there is no point in pulling MORE timing than?
For example, based on that IAT timing retard table I posted above that I used to use on my 30R, my VEMS was pulling 6 degrees out of my timing table on a regular basis. My base timing table was only ~12-15 degrees in the upper RPM range. 6 degrees of timing is NOT a lot, one could say effectively *too little* timing to even be worth it. BUT, that was my old intercooler and I felt it was worth it to save the motor. Sure, "turn down the boost yadda yadda" but I wanted to be able to push the car and let it figure out when/how to pull timing.
This is my current IAT retard table. As you can see, it is much less conservative:
- new iat timing ret table.jpg (67.45 KiB) Viewed 9495 times
