Joined: 04 Jun 2006
Location: Gaithersburg MD
temp sensor update
(Sun Jul 06, 2008 7:34 pm)
|I switched the ECT sensor to the head when I installed the Evan's waterless coolant. Of course this really zooed things up at first, but now that I am getting tuning back in line, the tuning is much more stable. It was wrong to have the sensor in the water jacket of the block. The temp of the coolant has little to do with what kind of mixture the combustion chamber wants.
The biggest problem came when trying to restart the car after a five or ten minute stop. The head would get heat soaked, and be around 205, while the coolant would be cooler, and maybe even still down in the 170 range if I hadn't driven very far; say to the bank down the street.
I started over with the tuning by bringing the warm up curve down to 1 at 198 degrees which is where the head runs while cruising, if not acted upon by unusually cool, or warm weather. Then I started it dead cold, and drove around as it warmed up, adjusting the warm up curve while watching the AF ratio gauge as it got warmer. When it was warm, I adjusted the entire fuel map, all cells at once to provide something close to 14.8:1 AF ratio. Then I adjusted the start up fuel to get it to start well when hot.
I then let it cool down, and started the entire process over once again, adjusting the warm up curve to accomodate the new base fuel map.
This is not fine tuning, but just getting it in the ball park. Since the gross adjustment of the map changed all the settings by a fixed amount, and not by a percentage, the lower VE numbers are richer by percentage now than the higher ones. But it is pretty close, and I will tune from here.
The Accel program has a trim map for the warm up curve that modifies the base warm up curve by RPM and engine load. It looks a little like a base fuel map, except it is only 16 cells. The idea is you can make the warm up curve multiply the idle range more, or less than, the cruise range or higher RPM range, to taylor each cell to wht the engine needs to keep the AF ratio good in that range. To tune this trim map I plan on setting the cruise cell at .750, (which just happens to be two over, and two down on the map) and never change that one as I tune during warm up. When the engine is operating in that cell, if the AF ratio is wrong (during warm up), I will change the warm up curve only. If, under these same conditions, the AF ratio is wrong in any of the other cells, I will alter the trim coefficient in those cells to correct the AF ratio. I had to figure this out on my own, as the manual is very, very deficient, as I have said many times.
Anyway, the bottom line is, now that the hardware is better, that is, the fuel tank is right, the temp sensor is in a better place, and all the ignition components are excellent, tuning is getting more stable, and hence, more rewarding. I am learning. I hope my exerience is a help to others.
I got new tires today, and I had the confidence to hand the keys to the tire shop manager, and not worry that it would not start, or act goofy in other unpredictable ways. The same was true when I had the front end aligned last week. It's begining to act like a normal car now. Thanks to all who insisted that things would go better with the ECT sensor in the head. You were right.
A REAL professional is someone who knows when to hit it with a bigger hammer.