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Power reserve gauge?


Chapap

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This is more of a theoretical/curiosity question. I’m guessing the most practicable answer is to use a vacuum gauge.

Is there a way to measure how hard the engine is working? I’m guessing that to make an actual “power reserve” gauge, you’d have to put the vehicle on a dyno and measure all throttle positions for all rpms, then use that in a program of sorts. How close would a vacuum gauge or throttle position gauge be? Maybe air or fuel flow? Guessing exhaust pressure/flow would mirror the intake? It’d all be rpm dependent so I guess it’d just be a gut interpretation unless you hook sensors up to some kind of comp.
 


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I idea how it works but most apps that talk with your truck have something similar. Dash command, torque etc.
 

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This is more of a theoretical/curiosity question. I’m guessing the most practicable answer is to use a vacuum gauge.

Is there a way to measure how hard the engine is working?
Yeah, it's known as a Dyno
 

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obd2 systems will tell you the percent load, some of the later obd1 ford EECs will also show it. Products such as scangauge will show it but only work for obd2 applications. With a 2.3 I'd imagine that the load percentage is close to 100 percent while driving though, haha.
 

Chapap

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obd2 systems will tell you the percent load
didn’t know that. I had Torque app with a cheapo boluetooth reader in an ‘03 Grand Marquis. Never found that option… or it didn’t show anything.
 

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Would load really be the best way to guage how hard the motor is working? On one hand I say yes.. but on the other hand I feel like referencing RPM against a dyno sheet would be better... it's likely a mix of the two.

You could probably achieve 100% load in first gear at low rpm with a big enough trailer.

But is that really as hard on the motor itself as spinning peak HP with very little load on it?
 

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Yes, a vacuum gauge can tell you engine load, high vacuum = low load, low vacuum = high load

Computer also does that calculation based on engine RPM(air flow), throttle position and MAF sensor data, its the Load calculation and most OBD2 apps can access that

But neither would give you a "power reserve" amount
 

Chapap

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Yes, a vacuum gauge can tell you engine load, high vacuum = low load, low vacuum = high load

Computer also does that calculation based on engine RPM(air flow), throttle position and MAF sensor data, its the Load calculation and most OBD2 apps can access that

But neither would give you a "power reserve" amount
“Power reserve” may be the wrong term… or right. I know power is actually technical term and that may… or may not… be what I’m looking for. It’s just that if I’m on a hilly interstate, I slow way down going up hill and don’t mind bobbling between 60-70. After an hour or two I get accustomed to the gutless engine and all the rattles and bangs, and I have to be careful not to do a steady 80. Just curious as to how much effort the engine is putting forth in various conditions.
 

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I would get a vacuum gauge and run a hose into the cab

Any vacuum gauge will work, but there are gauges like these: https://m.media-amazon.com/images/I/71-VT5ZcGFL._AC_SL1500_.jpg

These have a green area when vacuum is in the range where engine is most efficient when under load

Vehicles used to come with similar YEARS ago
I remember my Grandfather had a Cadillac with a red and green light on the dash, green for best economy/MPG
 

1990RangerinSK

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“Power reserve” may be the wrong term… or right. I know power is actually technical term and that may… or may not… be what I’m looking for. It’s just that if I’m on a hilly interstate, I slow way down going up hill and don’t mind bobbling between 60-70. After an hour or two I get accustomed to the gutless engine and all the rattles and bangs, and I have to be careful not to do a steady 80. Just curious as to how much effort the engine is putting forth in various conditions.
You need to downshift.
 

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The "load" calculation that the obd2 computer does is a very simple calculation. It is the amount of air actually going into the engine (as measured by the mafs and intake air temp sensor) divided by the amount of air that the engine will pump at 100% volumetric efficiency at that rpm. On normally aspirated engines, the load varies from somewhere in the 15% range at idle up to around 80% at wide open throttle. Many of the scanner devices have the ability to show you this value on a real time (or nearly real time) basis. And the load is actually pretty useful at showing you how much "reserve power" you have available at that point, since the power output of the engine is directly related to the amount of air it is ingesting. The pcm uses the load value in several important ways, such as deciding how much spark advance to provide at a given load and rpm - there is a lookup table that has "load" on one axis and "rpm" on the other axis and the table is filled with the spark advance numbers for each combination of load and rpm. (Of course, those numbers are modified by things like coolant temp, intake air temp, etc. but the load is a very important value to the pcm.
 

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Ive always had good luck getting a general idea of how hard im pulling the guts out of something by computeing throttle position, RPM, and how the motor sounds.
 


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