Ford's Drive by Wire Throttle Body Operation

by Shelby10' 4/24/2011, 7:55 pm

Stolen from another forum, but great info

Drive by wire Throttle Body operation in laymen’s terms and how it relates to the GT500 and other Fords

Ford's Drive by Wire Throttle Body Operation Throttlebodyscematic-1

Ford's Drive by Wire Throttle Body Operation Throttlebodyscematic-1

Ford has designed their DBW TB to be Torque based and behave a certain way in all different driving conditions such as: idle, drive away, shifting through all gears, down shift, steady state drive, WOT, coast with foot-off-pedal (daspot), highway drive, slow speed drive, reverse, shift into neutral during steady drive, etc.

To best understand what “torque based” means think of the relationship between the engine torque and the wheel on the ground.
In a manual transmission vehicle Ford has established certain throttle body (TB) load parameters based throttle position (TP) as engine torque is commanded.

Ford has built in torque based system safety checks (IPC’s) (Independent Plausibility Checker) in the PCM that the computer uses to constantly check to make sure the TB is operating within the parameters Ford established to make sure the TB is responding properly to driver ( actually Engine) demand.
If the IPC logic detects that power is greater than demanded it can take the necessary action to throw a “check engine light, or limit engine operation which could ultimately trigger a “fail safe”.
It is vital to TB design that the TB operate within these parameters in order to maintain stock like drive-ability and prevent a “check engine light” or a “fail safe” to occur.

There are some TB’s on the market today that don’t meet these criteria including all of the “brass geared” TB’s and tuners have had to make many changes in the PCM to get around the IPC’s, some to the point of even turning off Daspots and certain IPC’s and Fail safe’s in order to allow the engine to run with that particular TB.

This is not the case with the Ford Racing, the BBK and the L&M TB’s in fact they have been designed to run within the Ford factory preset parameters with all Dashpots, IPC’s and all fail safe’s in place to ensure safe reliable performance.

Ford's Drive by Wire Throttle Body Operation 101_3667-1

Ford's Drive by Wire Throttle Body Operation 101_3667-1

Now a word about “Tip in” , and “Dashpots’.

Tip in is the torque request needed when transitioning from idle position to part throttle. If there is not enough “tip in” you can experience a “dead spot’ in the throttle feel. Ford has allowed for this in their ETC (electronic throttle control) strategy. Yes this can be adjusted by a tuner if he so desires but in most cases this adjustment is not necessary and would only be done for personal preferences.

Think of a Dashpot as the rate of deceleration in engine rpm’s when you lift off the throttle. Too little dashpot and the car would drop rpm’s rapidly resulting in a less than smooth transition and a worse case of possibly stalling the engine.
Too much Dashpot and the engine RPM’s will hang up a while before dropping down to normal based on TP (throttle position).
Ford has allowed for this as well , for example with a manual transmission vehicle as in the GT500 when coming to a stop with your foot off the gas pedal the engine will remain at about 1100rpm’s while the vehicle is still rolling. Once it is fully stopped the ETC will allow the rpm’s to drop down to the normal 750rpm idle speed.
Even at highway speed when you let off the pedal the vehicle rpm’s will not drop off rapidly but will do so in a gradual manner.
Certain tuners prefer a different feel than what the stock Ford tune will give so they will opt to change certain Dashpot settings to achieve the feel they are looking for .

CAUTION:
There is a danger in changing these settings improperly which could result in an undesirable and improper engine operation like a “hanging or stuck throttle” which could be dangerous. Be sure your tuner understands this.

Of course there is much more to the DBW ETC strategy’s but I tried to touch on the basics to help give some understanding of how it works.

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