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What is "delta tps" in aem v2

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I'm trying to dial in my accel on my aem v2, and on the accel page there is a "dtps accel" table. What exactly does delta mean and what would this table be good for?

dtps accel describes the accel enrichment for the rate of change in throttle position. so the faster you slam the throttle pedal open, the bigger the rate of change in tps (Delta TPS) is.

So am I looking at this right, if the throttle is open 25% the enrichment is 35%?

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It's not a case of if the throttle is opne 25%, but rather if the rate of change of TPS is 25% (I'm not 100% sure on the units but I'd assume 25% per second) then you'll end up with the scheduled accel fuel being delivered. There are a range of modifiers however that will affect the final accel fuel depending on rpm, load and engine temp for example.

So its the Ramp rate of the fuel being applied to the actual throttle movement?

That channel 'dTPS' represents how quickly the throttle is increasing. Small values represent pressing the throttle slowly, and large values represent pressing the throttle quickly. The units are obscure, it's the amount of TPS change in some small fraction of a second. If you're not running the latest firmware on that ECU, the 02v02 firmware updates made some good improvements in the way the accel fuel calculations work. Tuning accel fuel on those older Series1 and Series2 AEM EMS units can be tricky; all the changes are multipliers based on your main Fuel map, so it's very important to have the fuel map tuned well for steady-state conditions before making adjustments to acceleration fuel.

Here is a copy/paste from an instructions PDF that gets installed to your machine when you have the latest version of interface software available for that ECU. In case the formatting doesn't translate well, the instructions PDF is named 'AEM Series 2 EMS setup notes -02v02 Firmware updates.pdf', and should be located in your \Program Files (x86)\AEM\AEMTuner\Instructions\ folder.

ACCEL FUEL

Tuners may have experienced difficulties in achieving desired acceleration fuel control in older

firmware versions. Firmware version 02v01 has a number of refinements to increase the overall

functionality of the acceleration fuel control as outlined below.

IMPORTANT ACCEL FUEL CHANNELS

TPS Filtered

Displays a filtered TPS (%) value. TPS Filtered is compared to channel Throttle to derive the Accel

dTPS channel value. The filter function is controlled by option Accel TPS Sensitivity. A higher Accel

TPS Sensitivity value will result in a slower TPS Filtered response and larger Accel dTPS values.

Accel dTPS

Displays the current delta throttle (%) value. Is the difference between Throttle and TPS Filtered. This

value is the basis for the delta-throttle accel fuel calculation and is the x-axis reference in the dTPS

Accel table.

Accel dTPS Latched

Displays the current dTPS Accel (%) value and is derived from the current dTPS Accel table value.

Channel only updates while the +dThrottle Trigger Count channel is incrementing.

+dThrottle Trigger Count

This channel increments anytime Accel dTPS is greater than option Accel dTPS Trigger. Accel fuel is

only calculated and delivered when this channel is actively incrementing.

Accel Mod

Displays the current Accel Modifier (%) value and is derived from the current Accel vs Throttle table

value.

Accel Warm-up

Displays the current Accel Warm Up Enrichment (%) value and is derived from the current Accel vs

Coolant Temp table.

Accel Fuel TPS Accel Factor

Displays the current TPS Accel Factor (%) value as derived from the Accel vs Engine RPM table. Is

also an accel fuel audit channel that reports the first step in the accel fuel calculation. Reports the

current accel fuel modifier value based on the Accel vs Engine RPM table.

Accel Fuel (Accel Mod)

Accel fuel audit channel that reports the second step in the accel fuel calculation. Reports the current

accel fuel modifier value based on the Accel vs Throttle table.

Accel Fuel (Latched)

Accel fuel audit channel that reports the third step in the accel fuel calculation. Reports the current

accel fuel modifier value based on the dTPS Accel table.

Accel Fuel (Warm-up)

Accel fuel audit channel that reports the final step in the accel fuel calculation. Reports the final accel

fuel modifier value based on the Accel vs Coolant Temp table.

Accel Fuel +Max

Displays the maximum accel fuel pulse width that can be delivered based on option Accel Limit and

the current fuel pulse value.

ACCEL FUEL TABLES REVIEW

dTPS Accel

The dTPS Accel table quantifies the size of a delta throttle event. This table is usually setup such that

smaller throttle deltas produce a smaller accel fuel amount and larger throttle deltas produce a larger

accel fuel amount. Should hold a fairly linear relationship between Accel dTPS and dTPS Accel. This

table has a 0-100% modifier range meaning that the largest accel fuel amount that can come from this

one table is up to the current fuel pulse value. It can only reduce the accel fuel amount.

Accel vs Throttle

The Accel vs Throttle table scales the accel fuel amount based on throttle position. More air flow is

generally introduced when the throttle is opened quickly at lower throttle positions versus a similarly

sized delta throttle event at a higher throttle position. Because of this, the Accel Vs Throttle table has

a generally downward trending curve and typically goes to or very near zero where increasing throttle

position no longer introduces a significant increase in air flow. This table has a 0-250% modifier range

meaning that the largest accel fuel amount that can come from this one table is up to 2.5 times the

current fuel pulse value. It can both increase and decrease the accel fuel amount.

Accel vs Engine RPM

The Accel vs Engine RPM table scales the accel fuel amount based on engine speed. More air flow is

generally introduced when the throttle is opened quickly at lower engine speeds versus a similarly

sized delta throttle event at a higher engine speed. Because of this, the Accel vs Engine RPM table

has a generally downward trending curve and typically goes to or very near zero where air flow is

sufficiently large enough at higher engine speeds that having a delta throttle event no longer

significantly changes air flow. This table has a 0-100% modifier range meaning that the largest accel

fuel amount that can come from this one table is up to the current fuel pulse value. It can only reduce

the accel fuel amount.

Accel vs Coolant Temp

The Accel vs Coolant Temp table scales the accel fuel amount based on coolant temp. Generally, an

engine needs more fuel at lower coolant temps to help maintain acceptable drivability and decrease

engine warm up time. Because of this, the Accel vs Coolant Temp table has a generally downward

trending curve and typically goes to zero when the engine reaches normal operating temperature. The

Accel vs Coolant Temp is only applied to the final accel fuel amount. This table has a 100-200%

modifier range meaning that it can increase the accel fuel amount by up to two times.

ACCEL FUEL TUNING TIPS

The processing of Accel dTPS has been updated in this version of firmware to give a larger dynamic

range of delta throttle values. The Accel dTPS function in previous firmware versions was limited to

only 35-45% but this has now been increased to give a full 0-100% range. The lower dynamic range

from the older firmware versions meant having to sometimes “ramp up” the dTPS Accel table more

aggressively to get appreciable dTPS Accel values. Now that Accel dTPS has a larger dynamic

range, a more linear dTPS Accel table can be used giving you a more usable range of dTPS Accel

values.

The lower dynamic range from the older firmware versions also meant using abnormally low Accel

dTPS Trigger values (1-3%) in order to get accel fuel to trigger at smaller deltas. The larger, updated

Accel dTPS range now allows more conservative Accel dTPS Trigger values (7-12%) which also helps

to prevent false triggering of accel fuel that may have resulted from using low trigger values.

The addition of the new accel fuel audit channels (Accel Fuel TPS Accel Factor, Accel Fuel (Accel

Mod), Accel Fuel (Warm-up), and Accel Fuel (Latched)) gives the ability to monitor the accel fuel

calculation as its being actively calculated. Reviewing these values in a data log will show how each

individual accel fuel table is influencing the accel fuel amount at any one moment. Close examination

of these values will allow you to better adjust the accel fuel table values to help create your final

desired accel fuel behavior.

Hope that helps,

SB