Engine RPM question

5736 Views 5 Replies 0 Participants Last post by Guest, Apr 5, 2002

Discussion Starter · Mar 27, 2002

Quick questions for anybody that has installed a tach to monitor gas engine RPM.

1) With the Prius stopped and the shifter in "N" what is the gas engine RPM? Does rpm vary at all with accelerator pedal position?

2) With the Prius in "P" what is the gas engine RPM with the accelerator pedal pressed to the floor? If the Prius is "warmed up" what is the slowest RPM you can maintain before the engine shuts off?

Thanks,

Ed

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Discussion Starter · #2 · Mar 27, 2002

I have just ordered an LCD lighted digital tach from JCWhitney with an inductive pickup. This will simply detect the pulses flowing in the spark plug wires and compute the RPM. The power will come from a tap in my fuse panel (I already tapped it for a voice activated phone).

as for your questions (I don't have the tach yet, but will guess on my observations ).

1) With the shift in park or neutral, when you press the gas peddle the RPM will go up some, but only a fairly small amount. I would guess something like 2000 rpm may be seen. Any if the battery is well charged and the engine warmed fully, the gas peddle sometimes will do nothing at all - sometimes the ICE will simply stop during the pressing of the peddle.

2) I think the first response somewhat answers the 2nd question too. The computer will determine if the ICE will come up in RPM at all. I have seen about 2000 - very approximately - peddle to the metal (so called). Of course put it in drive and the engine is supposedly limited to 4500RPM - If I recall correctly.

I will know more specifics when I install the new toy - (tach). I want that simply to watch the engine shut down or be idling while I drive at 60 MPH...

Steve Dickerson
'02 super white - 10,500 miles
NYS

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Discussion Starter · #3 · Mar 28, 2002

Steve,
Just a thought, isn't the Prius missing the high voltage spark plug wires? The Japanese Prius spec write up that was posted the other day <http://www.electrifyingtimes.com/priustechspecs.html> showed a sparkplug top unit with the following text:
- Ultra-compact cylindrical ignition coils have been adopted. Shaped to enable each of the coils to be independently connected directly to the spark plugs for the cylinders, the coils are placed in the plug holes in the cylinder head. Consequently, the use of high-tension cords is made unnecessary, thus minimizing high-voltage loss and electromagnetic interference. -
I know others have hooked up tachs, but recall that they found digital signals to use. Anyone out there have first hand knowlege?

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Discussion Starter · #4 · Mar 28, 2002

You are correct - I reordered (canceled the inductive tach) a DIS tach from JCWhitneys. I am not too sure how it will hook up, but most new cars seem to have this type ignition so they must work.. Anyone want to expand on installation of a DIS tach?

thanks..

Steve Dickerson NYS '02 super white - 10,500 miles.

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Discussion Starter · #5 · Apr 3, 2002

The engine does not "rev" at all when the gear selector is in neutral. The warm engine idle speed on my 2002 Prius is on average 950 RPM (same for park without pressing on the accelerator). If you "floor" the accelerator pedal in Park, the engine runs at 1,600 to 1,700 RPM.

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Discussion Starter · #6 · Apr 5, 2002

Thank you Richard.

1700 RPM makes sense for top engine RPM with Prius in park and accelertor pedal to the floor. In this scenario MG1 would be spinning at about 6200 RPM. Since the "red line" of MG1 has been suggested to be around 6500 RPM the numbers make sense.

I can also use this info when I take my Prius in for annual emissions testing. They like to take 2 measurements here. One at 1000 RPM (Put Prius in "N" for this measurement). And one at 2000 RPM (Put Prius in "P" and floor it to get 1700 RPM ... that should be close enough to make them happy).

Ed

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