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Old 12-31-2010, 03:07 PM   #11
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Re: Modifying cruise control to flow lph instead of maintaining speed

Originally Posted by SentraSE-R View Post
Most cruise controls adjust speed based on a voltage signal from the vehicle speed sensor. All you have to do is figure out the voltage limits from the VSS, and input another similarly limited voltage input in place of the VSS.
VSS is an AC frequency not a DC voltage.

Even in cars with a LPH pid, it's calculated, not measured so there isn't a sensor you can tap into.

As to substituting stuff, depends on the system. 2000 ford probably put it all together in one computer: CC is likely integrated in the PCM which is why you would need all the computer work to change it. On an older car (like my toyotas) with a separate computer for the cruise with analog inputs and outputs, you'd have a hope of getting it to happen. still quite problematic, but less so than newer cars.

I'm not trying to be difficult but it's not gonna pay off. I know it's less interesting but existing proven methods are more worthwhile.

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Old 01-01-2011, 01:01 AM   #12
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Re: Modifying cruise control to flow lph instead of maintaining speed

Originally Posted by Everett View Post
Well I was thinking about consistent fuel mileage and there aren't many hills here in saskatchewan. I was just wondering if it could be done and how. When I get my car dyno tuned I will see if it's possible to reprogram it to work like that. Unless you guys can feed me a how to. I would rather build it myself. The cool factor of the homemade part. Keep the ideas coming
Everett - do you understand that it is important to always have fuel and air in a consistent ratio? Or, are you talking about a diesel?

-Bob C.

Think you are saving gas? Prove it by starting a Gas Log, then conduct a proper experiment.
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Old 01-04-2011, 07:40 AM   #13
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Re: Modifying cruise control to flow lph instead of maintaining speed

I think the thought process is, place a limit on the amount of fuel to be consumed. ie, 30L per hour. That equates to 2000rpm at light load for example. If the load or rpm changes, the fuel consumption remains steady.
2000rpm/light load
1800rpm/heavier load
2200rpm/lighter load
There are many problems with this idea though. The engine requires a proper air/fuel ratio. To arbitrarily limit fuel flow would require the engine to modify the throttle settings according to the oxy sensors. Sensor reads lean (actually more air) then it would reduce throttle setting to achieve proper ratio. Sensor reads rich (lack of oxygen) then would open the throttle to achieve proper ratio.

That is REALLY an back-asswards way of doing something. Besides the properly working computerized systems (proven) out there right now compared to this untested theory, you also have the problem of adjusting something unrelated to achieve a goal.
Kind of like leaving the throttle set wide open and pulling spark plug wires off and on to vary hp to match the requirement.

The best way to limit fuel consumed is to monitor it yourself. Cruise works on flat ground, use minimal throttle on hills.

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