Before i jump to conclusions can someone explain how load is figured in the eec. i have an a9l eec. And do other eec figure it differently?


Ray

In short, Load is a percentage of airflow going into the engine relative to the engine's theoretical max airflow displacement. So if an engine has a displacement of 302 cubic inches, then IF the engine were flowing 302 cubic inches of air for every 2 revolutions of the crank, the Load should calculate out to 100%. Note Cubic Inch or Liters are measures of volume, not mass.

However the actual calculation is not that simple since what the computer needs is a mass value. The device the computer uses to detect airflow is either a Manifold Absolute Pressure (MAP) sensor, Vane Airflow Sensor (VAF), or a Mass Air Flow (MAF) sensor. Neither of these measure air in terms of volume, which is what CID is.

The MAP sensor is used in Speed-Density setups. This is where the manifold's pressure, along with RPM, Air Temp, knowledge of the engine's CID, and a look-up table are used to calculate how much air the engine is aspirating. With a known amount of air, in mass terms, flowing into the engine, the computer can calculate how much fuel needs to be sprayed by the injectors based on knowledge of the Air-Fuel-Ratio of the fuel assumed to be burned and commanded fuel trims.

MAF sensors measure the mass of airflow into the engine directly. Once an airmass flow is known, the computer can use the same technique described above to calculate fuel delivery.

VAF sensors were the predecessors to MAF sensors. They were basically a spring-loaded door that opened wider as airflow increased. They were horrible for performance AND were very dependent on air temp. But they were the first step away from Speed-Density towards directly measuring airflow.

In either case, Load is the ratio between how much air is calculated to be entering the engine relative to the theoretical max described in percent. Most naturally aspirated engines (stock and lightly modified) are not capable of flowing 100% of their theoretical max. Although more aggressively built N/A engines with aftermarket parts can. Most any boosted engine can exceed 100% without too much trouble. Lightly boosted engines can reach 125-130% Load. Extremely boosted engines (20+PSI boost) can easily exceed 200%. A common technique used by manufacturers today is to build cars with tiny fuel-sipping engines, but boost them with a turbo charger to get "big engine" performance from a small engine. With variable valve timing, direct fuel injection, and advanced ignition systems, engines can be built for fuel economy, moderate performance, and longevity.

But getting back on topic, which scenario are you wanting to know more specifics about? MAP, VAF, or MAF?

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89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

Maf is what I have. The confusion I have is the tps. Where does this come into play with the maf. And when does open loop need to come in off of tps? Does open loop bypass only the o2s and use the commanded afr from a table with the maf?


i hope I asked the right questions here.

TPS is used for accel enrichment as well as forcing Open Loop.

Yep. During CL, the EEC uses MAF, ECT, ACT, etc to calculate fuel. Then it uses the HEGOs to trim out "error." While in CL, the EEC efforts to keep the HEGOs switching rich-to-lean-to-rich. As long as the HEGOs are switching, the EEC is maintaining very close to stoic. It's also during this time that it learns long term fuel trims (aka KAMRFs) if learning is enabled.

During OL, the EEC is generally trying to command AFRs other than stoic. But HEGOs are useless for that. So the EEC has no choice but to "fly blind" and command without feedback. Depending on the tune, the EEC may or may not be referencing learned information. Regardless as the DIY tuner, it's your job to monitor actual AFRs via Wideband and modify the tune to deliver the fuel being commanded.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

In a nutshell
Load = maf / sarchg

Maf is actual airmass the ecu is calculating
Sarchg is the standard air charge "CID" scalar

on your car you should be enriching no later than half throttle or approx 3psi of boost

The fuel link my Sig has some good info

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