CA1148233A - System for monitoring and improving motor vehicle operating efficiency - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention is directed to a system which reduces the loading of the vehicle engine when the manifold vacuum pressure is less than a predetermined threshold level without requiring action by the operator to effect this shedding of the load. In addition, the invention incorporates monitoring apparatus in the system, to provide indications of the operator's inability to maintain a relatively high engine operating efficiency as indicated by the number of times the vacuum pressure decreases below the threshold level. Also the invention provides an indication of the time that the vehicle is operated in this less efficient condition. The information is available to the vehicle owner at the end of the period of operation and thus enables him to determine the habitually inefficient employee-operator of his vehicles.

Description

~ 3;233 -. ...
1 SYSTEM FOR ~NITORING AND IMPROVING MOTOR VE1~ICLE OPE~A~ING
EFFICIENCY

4 Back~ d of ~he Invention 8 This invention relates to a system for monitoring 9 the operating efficiency of an internal combustion engine and reducing the load on the engine during periods of reduced 11 operating eff~ciency.

13 The combination of highex fuel costs ~or the opera-14 tion of motor vehic1e engines and the modifications in engine .
design for environmental control which result in increased 16 fuel consumption have generated interest in improving motor 17 vehicle operating efficiency and thus reducing operating C08t.
18 In the case of fleet owners of vehicles, the increased fuel 19 costs and reduction in mileage per fuel gallon has produaed-a marked increase in operating cost and a concomitant decrease 222 in profitability. As a result, a definite need for system3 which can monitor the operation of the vehicle and improve 23 the efficiency of operation has been generated.

A system for indicating a reduction in engine mani-26 fold vacuum pressure by means of a light on the vehicle dash-27 board has been incorporated in some original equipment vehicle3 28 f~om manufacturer~. This passive system requires that the 29 operator note the indication of system inefficiency and take 32~ pcaltive tion to improve it. 1~ tAe case cf Eleet o~ners i;,' f.

` ~ 3233 1 ¦ having large numbers of vehicles and hired drivers, signals .... ... . . ~ _

2 from this type of passive system are often not observed. In

3 addition, it is difficult for the owner-employer to readlly

4 identify those operator~ taking positive action to'improve the vehicle operating efficiency.

Accordingly, the present lnvention is directed to a system which reduces the loading of the vehicle engine when 9 the manifold vacuum pressure is less than a predetermined ' threshold level without requiring action by the operator to 11 effect this shedding of the load. In addition, the invention 12 incorporates monitoring apparatus in the system, to provide 131 indications of tha operator' B inability to maintain a rela-14¦ tively high engin3 operating efficiency as indicated by the 151 number of times the vacuum pressure decreases below the 16 1 threshold level. Also the invention provides an indication 17 ¦ of the time th,~t the vehicle is operated in this less efficient 18 1 condition. The information i~ available to the vehicle owner 19 ¦ at the end of the period of operation and thus enable,s him to determine the habitually inefficient employee-operator of 21 his vehicles. ' 23 ¦ Summary of the Invention 24 ¦ The present invention for improving motor vehicle operating efficiency and monitoring the occurrence of inter-26 vals of relatively inefficient operation includes an electrical 27 system connected to the electrical circuit of the motor vehi-28 cle and which i~ responsive to one or more of the operating 2~ conditions of the motor vehicle, such as the pressure level within the manifold of the engine. , 32 ,, li, ,. , ~8'~33 1 The system includes a flrst relay means havlng a 2 flrst control element and a flrst switch element having first 3 and second states. The first switch element i8 res?on8ive 4 to the first control element ar.d changes state accordir.gly.
S Also included is a switch responsive to a vehicle operatlng 6 condition and having first and second states. This switch 7 changes state in response to variations in the operatlon 3 condition being monitored; for example, changes in the manl-9 fold pressure about a threshold level, and is coupled between the vehicle electrical circuit and the first control element.
11 The lowering of the engine operating condition below the 12 threshold level causes the first control element to be acti-13 vated and changes the state of the first switch element from 14 a normally closed state to an open circuit state.

16 A second relay means having a second control element 17 and a second switch element having first and second states ia 18 provided. The second switch element is responsi~e to the 19 second control element and changes state accordingly. The 20¦ second control element is coupled between the vehicle electri-21 ¦ cal circuit and the first switch element. In operation the 22 ¦ second control element is deactivated by the opening of the 23 ¦ first switch in response to a change in vehicle operating 24 condition below the threshold level.
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26¦ The second switch is coupled into the sontrol circuit 27 ¦ of at least one vehicle acce sory, generally the air condi-28 ! tioning compressor control circuit. This second switch i.s 29 ¦ in a normally open circuit state. The energization of the 32 seoo~d con rol element caosss ~he s-cond switch elsment to ~ . ~ ' . .

~ _3_ , ll ` ' , l ~ 3233 1 ¦ enter the closed,circult state. Since the firqt switch~e~a-¦ ment of the first-relay-means:iq-normally closed, th~ sedon~C
3 ¦ control element is typical,ly,,ene~qi~ed during effician~_:~
¦ vehicle operation and the second switch is closed thereby -S ¦ not altering the vehicle accessory operation. When the - -~
6 ¦ second switch i9 in its open circuit state, the controlled 7 ¦ accessory load is not coupled to the vehicle engine~

9¦ The second relay means preferably include time delay 'I means which delay the opening of the second switch element-11¦ for a first inter~al after the opening of the first switch 12¦ element. Thus, the controlled accessory is not shed from the ~31 vehicle engine load unless the vehicle operating condltion- ~
~41 stays below the threshold level for the duration of the first ~51 interval. The time delay means also n~aintains the second 161 switch element in the open circuit state for a second pre~ ~
17 ¦ determined interval after the closing of the first switch --18¦ element. The controlled accessory is then cutoff for-at~
~9l least as long as the second interval. The time delay means essentially eliminates the transient effectq associated with:--2.1 urban driving patterns. - - ' , ~-~

23 The monitoring of vehicle operation is provided by 24 a third switch element having first and second states and 25 I responsive to the activation of the first control element of 26 ¦ the first relay means. Timing and counting means are coupled 27 between the third switch element and the ignition circuit so 28 that their operation is initiated by a drop in the vehicle 29 operating condition below the threshold level.

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ll The present invention provides increased operating ! :
2 efficiency by the load shedding of selected vehicle accessorles 3 in response to changes in operating conditions and provides 4 the vehicle owner with the number of occurrences and the total operating time under the low operating conditions.

7 Further features and advantages of the inventlon 8 will become more readily apparent from the following detalled 9 description of a specific embodiment of the in-~ention taken in conjunction with the accompanying drawings.
11 l 12 irief Desc~tion of the Drawings 13 Fig. 1 is a block schematic diagram of one embodi-14 ment of the invention.
, î6 Fig. 2 is a series of timing diagrams illustrative 17 of the operation of the embodiment shown in Fig. l.

19 Description of the Preferred Embodiments 2~ Referring now to ~ig. l, the invention is shown 21 in a block sche~atic form. The conventional automotive key-22 activated ignition switch ll is shown electrically connected 23 to the positive terminal of the motor vehicle battery 12. The 24 negative terminal is coupled to a reference potential, normally the vehicle chassis.

27 The ignition switch is electrically connected to a 28 pressure-respons~ve electrical switch 14. Switch 14 has open 29 and closed states and remains in the normally open condition as long as the vacuum pressure in the region ~eing monitored 31 is above a threshold level. In the present invention, the 32 ,.

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1L~1 ~8Z33 1 pressure being ~onitored is that of any vacuum system directly 2 responsive to the engine intake manifold preqsure. While the 3 pressure-responsive switch may be inserted directly into the 4 intake manifold, it has been found advantageous to monltor the vacuum pressure in a spark advance vacuum system that i~
6 directly responsive to the intake manifold pressure. The 7 term vacuum pressure as utilized herein is taken to mean 8 negative pressure.
In tested embodiments, the pressure responsive switch 11 is selected to change state at a threshold vacuum pressure of 12 approximately six to eight inches of mercury. Since vehicle 13 operating elevations differ significantly, the threshold 14 level of the vacuum pressure switch can be selected to be 85 to 90 percent of the manifold vacuum pressure of a vehicle 16 ¦ operating at 60 miles per hour with substantially zero 17 ¦ acceleration.

19 ¦ In certain vehicles, the spark advance vacuum syste~
20 ¦ is not directly responsive to manifold pressure due to the 21 1 incorporation of a delay function in the design of the vehicleO
22 In vehicles of that type, the pressure responsive switch is 231 located so as to directly monitor manifold pressure, prefer-24 ably intake manifold pressure due to the lower operating temperatures therein when contrasted with the exhaust manifold 26 system which not only has a higher operating temperature but 27 is more likely to contain pressure leaks.

29 The embodiment shown in Fig. l utilizes the moni-toring of vacuum pressure to determine the engine operating ' I~
~ 33 l conditions and to e~tablish the threshold level for operat~on 2 of the invention. Due to the availability o~ vacuum swltches 3 to the system installer and the reliability of vacu~m pressure 4 monitoring devices, thi~ embodiment enables presently operating ~ vehicles to be retrofitted with the invention for a relatively 6 low cost. However, other engine operating monitoring dev~ce~
7 can be employed if desired. For example, the rotation of 8 the drive shaft or an axel could be monitored by either direct 9 drive linkage or by optical monitoring. These types of monitoring could be utilized to activate subsequent sy~tem 11 components based on rates of acceleration or merely high speeds, 12 if desired. In addition, the fuel supply system can be moni-13 tored by a flowmeter and a threshold established indicative 14 of a particular operating condition. Embodiments of these types utilizing different engine operating condition monitors 16 are difficult and relatively expensive to install in pxesently 17 operating vehicles and better suited to be incorporated by 18 the manufacturex in new vehicles.

The pressure switch 14 is electricallv connected 21 to the control element 16 of first relay 15. When the igni-22 tion switch is turned on and the vacuum pressure in the intake 23 manifold is below the threshold level, the pressure switch is 24 actuated and a voltage is applied across the control element 2S 16. First relay 15 includes ~witches 17 and 18 each having 2G first and second states and each of which is responsive to the 2~ application of the voltage across control element 16. As 28 shown in Fig. 1, first switch 17 is in the normally closed 2~ ~tate and opens when the vacuum pressure in the manifold drops belo~ the threshold l~vel. Switch 18 is shown in its 31 normally open state and closes when control element 16 ig 32 energized. ,, 1~ Switch 17 i~ coupled via control element 21 of t~me ¦ delay relay 20 to the lgnition circuit. Thus, when switsh-3 ¦ 17 is closed, ~ voltage is applied across control element 21.
4 Also included in relay 20 is switch element 22 having ~
normally open state. Switch 22 is utilized to electrically 6 couple the therl~ostatlc control 23 for the vehicle air condi-7 tioning compressor 29 to the ignition switch. Switch 22 19 8 shown in the normAlly open state. When closed, the combina-9 tion of the thermostatic control 23 and the compressor 29 ~ol operate in their normal operating mode. This operatio~ is interrupted by the opening of switch 17 which result~ in the 12¦ removal of the voltage across control element 21 and cause~
13¦ switch 22 to return to the open circuit state. Consequently, 14 ¦ the air conditioning circuit i9 disabled at this point in 15 ¦ time and the comp_essor load is no longer present for the 16 ¦ motor vehicle engine~.
17 l 18 I Switch 18 of first relay 15 is coupled to the igni-19 ¦ tion switch via the series combination of time delay 26 and indicating device 25. When switch 18 is closed in response 21 to a low vacuum pressure state sensed by switch 14, the indi-22 cating device 25 shown as a buzzer in Fig. 1 is activated to 23 identify the low operating efficiency condition to the opera-24 tor. In addition, the buzzer points out to the operator that maintenance of the low operating efficiency condition will 26 result in one or more controlled accessories being removed 27 a~ vehicle engine loads. Time delay 26 is characterized by 28 a normally closed state in the absence of a voltage applied 29 thereacross. When switch 18 i5 closed, the voltage i~ applied 30 ¦ across the combination of indlcatlng device 25 and tlme , ~ 233 1 delay 26. The.time de~ay 26 re,mains in the clo=sed state for_ 2 an interval.of,time and then opens the circuit to disablç ~he 3 buzzer to prevent the continuous,signalling to the opera=tor.
4 If-desired, a.manual switch may be connected in electrical series with buzzer 25 to permit the operator to di~able the 6 buzzer~ , . - . ,..: . : . . . . .. ..
8 Also, switch 18 is coupled to the ignition switch 9 via the parallel combination of timer 27 and counter 28 so that the closing of switch 18 activates these two component~.
11 Timer 27 is activated by the closure of switch 18 and is an 12 elapsed time indicator which at the end of a long period of 13 vehicle operation shows the amount of time during which .~he .
14 vehicle was operated in the low efficiency condition. Counter 28 is activated at the-same time and records the'number.of 16 occurrences of the low operati.ng efficiency condition. ..

18 Also included.in the preferred embodiment is hour-, 19 meter 24 connected directly to the ignition circuit. Conse-quently, this meter records the total elapsed time during._ 21 which the vehicle is operated. The relays 15 and 20 provide_ 22 the load shedding feature of the invention which enhances 23 operating efficiency~while the timer and counter provide the_ 24 fléet owner with the information necessary to determine the nature of the operator's driving habits. If desired, hour 26 meter 24 provides the total elapsed time of operation. The 27 feedback of information to the operator is provided by relay , 28 15 and the combination of buzzer 25 and time delay 26.
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---: Since the vehicle is expected to operate under a 31 -~ariety of traffic conditions, it has been found advantageous 32 . ,, ,,~!A, ~ 33 1 to incorporate time delays in second relay 20. The lnltlal 2 delay makes the switch 22 achieve its open condltion a f lr~t-3 predetermined interval after the voltage is removod from 4 across control element 21 due to the opening of switch 17.
S Also, a second delay is provided to maintain the switch ~2 6 in the open position for a second interval after switch 17 7 is closed to again apply the voltage across element 21. The 8 use of the delay intervals presents the repeated on-off 9 cycling of the controlled acces~ories which would occur due to the stop-start followed by rapid acceleration cyclQs 11 characteristic of many urban traffic patterns. In addition, 12 the combination of the normally open state of switch 22, the 13 normally closed state of switch 17 and the time delay of 14 relay 21 result in the air conditioning and/or controlled loads not beinq coupled to the engine when it is initially 16 started. The controlled loads remain decoupled from the 17 engine after closure of the ignition switch for the duration 18 of the second interval. The second interval i~ longer than 19 the typical time utilized to engage and disengage the ~tarter motor, for example five seconds, and ls therefore not deter-21 mincd by the engine operating efficiency. While the engine 22 may achieve an efficien~ operating condition shortly a~ter 23 ¦ disengagement of the starter motor, the lengthened second 24 ¦ delay interval has be~n found to reduce the potential for 25 ¦ stalling when engine operation is initiated.
26 l 27 ¦ The foregoing detai1ed description o~ the ~mbo~i-28 ¦ ment of Fig. l refers to the use of relays and time del~y 29 ¦ relays which are discsete or individual electrical component9.
30 ¦ The term relay as u~ed herein is intended to mean an electr~-31 ¦ cally controlled device having at least two states which corre~-32 ¦ pond to the open circuitin~ and the conducting states of a ,.
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B~33 1 conduction path in an electric circuit. Thus, it iq intended 2 to include solid state devices, whether a discrete component 3 or an integrated part of a multi-element semiconductor device.
In the case of a time delay relay, the actuatable switch element and the time delay element may be either integrated 6 into one component or may be two discrete elements coupled 7 together to operate in the intended manner as described 8 below in connection with the waveforms.
The operation of the system is shown in the wave-11 forms of Fig~ 2 wherein the manifold vacuum pressure i8 12 plotted as a function of time. At time tl, the ignition 13 switch is turned on and the engine is started. The vacuum 14 pressure increases to P (i.e. absolute pressure drops) in the intake manifold. After starting at time tl, the engine 16 is idling and the vacuum pressure remains above the threshold 17 pressure P0 until time t3 when the driver elects to accelerat~
18 the vehicle rapidly.

Although the ignition switch ll was closed at time 21 tl and the manifold vacuum pressure increased to a level above 22 the threshold, the time delay relay provides an open circuit 23 condition in the controlled accessory circuit until time t20 24 This delay insures that the accessories are not coupled to the engine during the initial start period when inefficient opera-26 is likely to be encountered. As shown by the solid line of 27 the vacuum pressure, the driver begins to accelerate at time 28 t3 and maintains this acceleration rate until time t6. This 29 situation is typical of a passing situation or high speed on an inclineO At time ts, the acceleration rate is decreased 1j~and the manifold vacuum pressure is again above the threshold 2l¦level PO signifying that the vehicle is again operating in a 3!lrelatively fuel-efficient manner.

I At time t3 when the driver has elected to rapidly 61accelerate, switch 18 closes and the buzzer 25, timer 27 and 7!~ counter 28 operate. The buzzer is non-operative at time t5 8,~due to the time delay circuit 26 which typically is set for jla 0.5 second operating interval. The timer and counter re-0llmain activated until time t6 when the vacuum pressure rises labove the threshold level PO.

13l! The opening of switch 17 at time t3 results in the 14, opening of switch 22 after a delay interval of 1.0 to 1.5 151'lsecond at time tS. The switch 22 remains open after time t6 16¦1due to tha second delay of about four seconds and closes at 17 time t7. Thus, the air conditioning compressor 29 is removed 18 as an engine operating load for the t7 - tS interval thereby 19 improving operating erficiency. The t7 and t6 interval is 20 equal to the t2 - tl interval provided at the initial starting 21 of the vehicle engine.

23 The broken lines of Fig. 2 illustrate the operation 24 1 of the invention during periods of short rapid acceleration 251lsimilar to the operation resulting from the passing of another 26 ~ motor vehicle. At time t3 the vehicle vacuum pressure drops 27 1I below the threshold level PO and returns at time t4. The 231,buzzer, timer and counter are all activated and then de-activated 29~, at time t4. The time delay relay and switch 22 remain in 30 ~the closed position since the t4 and t3 interval is less than 31 ~the duration of the first delay interval provided by relay 20.

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~¦ In embodiments of the invention installed in vehicles 21 wherein extended periods of inefficient opPration are likely 3 Ito be encountered, it has been found desirable to utilize the 4 Iprior-discussed embodiments with an override relay 31 provided sllas shown in Fig. 1. One example of the type of driving condi-6 ,tion which gives rise to a need for the incorpora~ion of 7 Irelay 31 is the large change in elevation experienced during 8 driving through the Rocky Mountain region of the United States.
9¦lIn situations of this type, the operator does not wish to 10!lhave the controlled accessories inoperable for this extended 11¦lperiod and the override relay is included to set a maximum 12lltime for the energization of control element 16 and the 13~lresulting deenergization of control element 21. f 15¦ During operation, switch 32 of relay 31 is normally 16 closed and the embodiment of Fig. 1 operates as previously 17 described with current flowing to relay 15 upon the activa-18 tion of pressure switch 14. In addition, current flows 19 ~through control element 33 and after a predetermined interval, 20 ¦typically 20 to 40 seconds, the control element 33 heats to 21 !! a level wherein switch 32 opens, thus halting the flow of ¦~current to relay 15 and permiiting switch 17 to close. As 23jia result, control element 21 is energized and switch 22 closes 24¦,to permit the controlled accessories to resume operation.
~511 Switch 32 stays open until pressure switch 14 reopens and 26,lcurrent no longer flows through control element 33. In prac-27~'tice, a one second delay in the closing of switch 32 is pro-28l, vided. When the switch is again closed, the sequence previously 29lldescribed can be repeatëd when inefficient operation i8 next 30 encountered.

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~8'233 In embodiments of the invention as shown in Flg. l 2 wherein the buz2er notifies the vehicle operator of lnefficient operating conditions which embodiments have been te ted ~ r ~tr~C7e ~na~ over one thousand mil,e~ in a Volkswaqon Rabbit and a Pontiac ,,(~cle ~ ~onneville, the number of rapid accelerations was decrea~ed 6 by four to five times due to operator recognition of inefficient 7 operating conditions. The percantage of total operatlng t$me 8 spent under heavy acceleration with an intake manifold vacuum 9 pressure of less than eight inches of mercury was reduced from 8.7~ to 0.9~ in the case of the Volkswagon and from 9%
11 to 1.2~ for the Pontiac. The fuel consumption as measured by 12 mile per gallon calculations improved in the Volkswagon from 13 27.2 to 32.1 miles per gallon and in the Pontiac from 12.0 14 to 14.3. In embodiments of the invention wherein the indi-cating device 25 is not utilized to notify the driver, the 16 shedding of the controlled load in response to the activa-17 tion of the relays has been found to provide a four to six 18¦ percent increase in fuel economy during extended periods of 9 ¦ vehicle operation.

21 ¦ The invention does not directly control the engine 22 ¦ so that full power and acceleration are available to the oper-23 I ator at all times during operation if he requires them. Thus, 24 the present invention does not alter the safety characteristics of the vehicle upon which it is fitted. The embodiment shown 26 in Fig. l and the test data therefor refer only to the shedding 2. of the air conditioner compressor load during the period3 28 of inefficient operation. Other automobile accessories, for 29 ¦ example the alternator, may be so controlled by providing either additiona sw"~ches for the time delay relay ~nd 3'1 connecting this to the field armature winding or utilizing 2 ¦ swi'ch 22 for more than one accessory.
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82~3 1 I In the embodiment tested and operated as described 2 Iherein, the pressure switch 14 utilized was a vacuum switch 3'1 made by John W. Hobbs Co., Springfield, Illinois, with a 4 threshold within the range of 6.5 to 7 inches of mercury,

5, the first relay l5 was a Potter & Broomfield 12v DPDT relay, 611tl1e delay relay was a 12 volt normally open two second delay 7l~r.~lay made by Amperite and the override relay 31 was ~ 12 81lvolt normally closed 30 second delay relay made by Amperite.
9~¦The delay interval for the override relay is normally selected ~lito be shorter then the time interval required for the coils in the air conditioning unit to rise significantly in temper-12l ature. The fan in the vehicle continues to circulate air and 31~; it is found to improve the vehicle comfort level to have the I -14loverride switch take effect prior to any significant tempera-15l~ture change in the vehicle. The particular delay interval is 16 ~determined in part hy the operating climate and the construc-17¦ tion of the vehicle.
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While the above description has referred to a specific embodiment of the invention, it will be recognized 21 that many variations and modifications may be made therein 22 without departing from the scope o~ the invention.

24 What is claimed is:
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Claims (7)

1. Apparatus for improving motor vehicle fuel effi-ciency by reducing the accessory load on the engine during periods of reduced operating efficiency, said apparatus, comprising:
a) means for monitoring engine operating conditions and providing an output signal indicative of engine operating efficiency below a threshold level;
b) time delay means responsive to the output signal of said monitoring means, said time delay means having first and second states and first and second pre-determined delay intervals, said time delay means being activated to the second state by the application of said output signal to the time delay means for at least as long as said first delay interval, said second delay interval occurring upon the terminating of said output signal whereby the time delay means remains in the second state for at least as long as the second interval;
c) means for coupling the time delay means to the accessory being controlled, said accessory being disabled from operation when said time delay means is in the second state;
and d) override means coupled to the time delay means for limiting the duration of the disabling of the accessory to a third predetermined delay interval.

2. Apparatus in accordance with claim 1 wherein said time delay means includes a time delay relay having first and second states, said time delay relay being responsive to the output signal of said monitoring means.

3. Apparatus in accordance with claim 1 wherein said override means includes a time delay element which is responsive to the output signal of said monitoring means and has first and second states, said time delay element entering the second state after receipt of said output signal for the third interval and remaining in said second state at least until cessation of the output signal from said monitoring means.

4. Apparatus in accordance with claim 1 wherein said means for monitoring engine operating efficiency comprises pressure-responsive means for monitoring engine manifold pressure and providing an output signal indicative of engine operating efficiency below a threshold level.

5. Apparatus for improving motor vehicle operating efficiency by controlling the operation of vehicle accessories wherein said apparatus is connected to the vehicle electrical circuit and responsive to engine manifold pressure, said appar-atus comprising:
a) switch means having first and second states and responsive to changes in engine manifold pressure, said switch means being in the first state when the manifold vacuum pres-sure is less than a threshold level;
b) time delay relay means having a first control coupled to said switch means and the vehicle electrical circuit and a first switch element coupled to the accessory being con-trolled, said first switch element having a delayed response to the activation and deactivation of said first control ele-ment, said first control element being activated when the switch means enters the first state whereby the first switch element responds to disable the accessory;
c) override delay means responsive to a change in state by the switch means to the first state for overriding the disabling of the accessory by the first switch element after a predetermined interval whereby said accessory resumes operation independently of the state of said switch means.

6. Apparatus in accordance with claim 5 wherein said time delay relay means comprises first and second relays, each having a switch element and a control element, the first relay control element being coupled to the switch means, the second relay switch element being coupled to the accessory being controlled, the first relay switch element being coupled to the second relay control element, one of said first and second relays having a delay therein.

7. Apparatus in accordance with claim 6 wherein the first relay switch element and the second relay switch element are normally closed and normally open respectively.