Tweet
This will be an ongoing topic, contributed to as I get the time to add stuff and migrate things over from the old forum.
HARDWARE
// coming soon //
SOFTWARE
// coming soon //
IN THE TRUCK
Always....ALWAYS get your feet wet with tuning by working on idle. Idle conditions are the most sensitive, so if you go too lean, it'll just die w/o hurting anything. Do that at WOT and you might regret it. Also, there's less distraction when tuning idle as you don't have to concentrate on driving, so start simple and get a grasp of tuning before hitting the road. Not the most fun, but worth the time spent.
There will be a couple of main tables to control idle rpm:
- F18 - Idle vs Coolant Temp (in gear)
- F19 - Idle vs Coolant Temp (in P/N)
- F13 - Idle vs Battery Voltage
So, essentially, the ECM is going to look at your condition and work through a kind of idle flowchart from there. Are you in gear?....use F18+F13. Are you in P/N?....use F19+F13. From there it's going to see what temp the engine is at and what the voltage output is. Truck is in P/N, was just fired (68 degrees) and the voltage is at 14.4v....it'll use the 20C cell from F19 and the 14.4V cell from F13.
Simple, right? So far it is, but things get a bit more complicated from here. What if the temp is between 20C (68F) and 44C (111F)? Such as 90 degreesF....well, the average of the two is taken. So, if 20C is set for 800 rpm and 44C is set for 750 rpm, it'll command 775 rpm until the temp rises to closer to 44C. But what about the battery voltage table (F13)? What affect does it have? Well, it's always blended. So, if you're at the above condition (in P/N, 20C & 14.4v) and the F19 table is commanding 800 rpm and the F13 table is commanding 775, then the desired idle will be 788 (800+775/2 rounded up). And if you suddenly turn on a heavy load (rad fans, IC fan, and IC pump all at once) and the voltage dips to 12.8v? Well, the F19 table stays the same and the F13 table references the 12.8V cell (which could be 900 rpm) and suddenly it's blending 800 & 900 to give a desired idle of 850 to counteract this electrical load. Once the voltage returns to normal, the idle does as well. Make sense?
You'll want to get the idle happy (no stumbles, pushing through brakes, etc....700-800 rpm and 13.5:1 or so will do for now) with it in gear and in P/N. Next you want to make sure that there is as little as possible difference when shifting from P/N to drive/reverse. You can't just go in and match the values in the top two tables, because there is a load difference in between those two conditions. Every truck is different, but I usually start with a 100 rpm difference and tune from there. (I tuned the '92 Sy idle so heavily that the only way to know it went from N to D was to look at the shifter.) * Remember to put the idle through it's paces (come to stop from speed, test with headlights on and turn steering wheel at idle, etc....)
If you have electric fans, you'll be glad the idle vs batt voltage table is there as it has cured any stumble from high amp fans on any truck I've worked on. I usually set the idle for the lower voltages (10v-13v) higher than desired idle in an incrementing form (50 rpm to 150 rpm), but keep the 14v+ value near desired idle.
After getting a consistent idle that you like (easy to hold still, doesn't try to die at stoplights, etc....), you can start trying to lean out the mixture to get your AFR up near stoichiometric. Don't get obsessed with it, but try to get near 14.0-14.5:1 so your not burning people's eyes when you crank the truck up. If you spend a fair amount of time in town (sitting at lights) then you can gain some considerable economy by get idle AFR right.
HARDWARE
// coming soon //
SOFTWARE
// coming soon //
IN THE TRUCK
Always....ALWAYS get your feet wet with tuning by working on idle. Idle conditions are the most sensitive, so if you go too lean, it'll just die w/o hurting anything. Do that at WOT and you might regret it. Also, there's less distraction when tuning idle as you don't have to concentrate on driving, so start simple and get a grasp of tuning before hitting the road. Not the most fun, but worth the time spent.
There will be a couple of main tables to control idle rpm:
- F18 - Idle vs Coolant Temp (in gear)
Main idle control table for idle while in gear. This table runs from -28 degC (-18 degF) to +92 degC (198 degF). Anything colder than the -28C cell will observe it's value, and anything hotter than the 92C cell will observe it's value. The value you set in here will be the one shown as commanded in your datalogging software. However, it may be blended with another table (F13). More on that below.
- F19 - Idle vs Coolant Temp (in P/N)
Main idle control table for P/N. Same as above but for park/neutral situations instead of in gear.
- F13 - Idle vs Battery Voltage
Main idle control table based on battery voltage. Values in here are based on direct voltage from the alternator and will allow you to add idle rpm in the case of a voltage drop (heavy load, dying component, etc...).
So, essentially, the ECM is going to look at your condition and work through a kind of idle flowchart from there. Are you in gear?....use F18+F13. Are you in P/N?....use F19+F13. From there it's going to see what temp the engine is at and what the voltage output is. Truck is in P/N, was just fired (68 degrees) and the voltage is at 14.4v....it'll use the 20C cell from F19 and the 14.4V cell from F13.
Simple, right? So far it is, but things get a bit more complicated from here. What if the temp is between 20C (68F) and 44C (111F)? Such as 90 degreesF....well, the average of the two is taken. So, if 20C is set for 800 rpm and 44C is set for 750 rpm, it'll command 775 rpm until the temp rises to closer to 44C. But what about the battery voltage table (F13)? What affect does it have? Well, it's always blended. So, if you're at the above condition (in P/N, 20C & 14.4v) and the F19 table is commanding 800 rpm and the F13 table is commanding 775, then the desired idle will be 788 (800+775/2 rounded up). And if you suddenly turn on a heavy load (rad fans, IC fan, and IC pump all at once) and the voltage dips to 12.8v? Well, the F19 table stays the same and the F13 table references the 12.8V cell (which could be 900 rpm) and suddenly it's blending 800 & 900 to give a desired idle of 850 to counteract this electrical load. Once the voltage returns to normal, the idle does as well. Make sense?
You'll want to get the idle happy (no stumbles, pushing through brakes, etc....700-800 rpm and 13.5:1 or so will do for now) with it in gear and in P/N. Next you want to make sure that there is as little as possible difference when shifting from P/N to drive/reverse. You can't just go in and match the values in the top two tables, because there is a load difference in between those two conditions. Every truck is different, but I usually start with a 100 rpm difference and tune from there. (I tuned the '92 Sy idle so heavily that the only way to know it went from N to D was to look at the shifter.) * Remember to put the idle through it's paces (come to stop from speed, test with headlights on and turn steering wheel at idle, etc....)
If you have electric fans, you'll be glad the idle vs batt voltage table is there as it has cured any stumble from high amp fans on any truck I've worked on. I usually set the idle for the lower voltages (10v-13v) higher than desired idle in an incrementing form (50 rpm to 150 rpm), but keep the 14v+ value near desired idle.
After getting a consistent idle that you like (easy to hold still, doesn't try to die at stoplights, etc....), you can start trying to lean out the mixture to get your AFR up near stoichiometric. Don't get obsessed with it, but try to get near 14.0-14.5:1 so your not burning people's eyes when you crank the truck up. If you spend a fair amount of time in town (sitting at lights) then you can gain some considerable economy by get idle AFR right.