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Cruising RPM's

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    Cruising RPM's

    ok so basically i would like a slight drop in rpm @ 70 since thats usually my flow in highway

    could i slightly oversize the diameter of wheels n tires to help compensate that ?

    less revolutions the better right ?

    or will engine be strained the same ?

    #2
    Which engine and transmission do you have?

    Larger diameter tires will reduce the driveline (including engine) rotational speed at a given vehicle speed, but 70 mph on the speedometer will no longer be 70 mph on the road.
    90 LX 4dr 5 spd 396,014 (sold 1/1/2022) - MRT: http://www.cb7tuner.com/vbb/showthread.php?t=201450
    08 Element LX FWD AT 229,000 - MRT: fleetw00d : 2008 Honda Element LX - CB7Tuner Forums

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      #3
      The technical and short answer is, no. There’s some wiggle room, but not enough for a firm yes.

      It depends on how much of a drop in RPM you want. This is, most of the time, controlled by the gearing of the transmission/final drive/differential. There's variable timing which also is used in vehicles with a drivetrain, but the older generation Hondas really didn't have it (they had VTEC, but it wasn't as advanced as let’s say a VANOS when it first hit the scene). Change your final drive/last gear out. It's an idea I came up with a few years back, and @Losiracer experimented with it in his M2B4 yielding great results.
      Last edited by Straight Success; 09-05-2020, 02:16 PM.
      The Lord watches over me!

      "Stop punching down on my people!!!"

      - D. Chappelle

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        #4
        There are a number of engine rpm calculators online, most of which include tire size. You’d need to know the exact specs of everything else in the driveline. I don’t know that we have that information on here, but it should be available somewhere.






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          #5
          In addition, what do you consider a slight drop in RPMs (25, 50, 100, 500, 1000, etc...)?
          The Lord watches over me!

          "Stop punching down on my people!!!"

          - D. Chappelle

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            #6
            car is a 92 ex accord ..

            mostly highway approx 70 mph

            i know about the speedometer mismatch when changing sizes as well ..

            i was just sitting back after dabbing some Larry Bird and that crossed my thoughts

            i was looking at a tire comparison site and trying to match some 17's to stock 15's when i thought what if i went up either sidewall or to 18's ( granted weight be close ) would that in any way shape or form drop my rpm's significantly ???

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              #7
              The engine speed will vary directly with the rolling radius of the (front) tires (not the wheels). A 195/60-R15 tire has a rolling radius of about 12 inches. A tire with a rolling radius of 13 inches would reduce the rpm at a given speed by a factor or 12/13 (about .923). For example, at whatever speed your car runs with an engine speed of 3000 rpm, a 13 inch tire would reduce the rpm at that same (actual) speed, the rpm would be 2769.
              90 LX 4dr 5 spd 396,014 (sold 1/1/2022) - MRT: http://www.cb7tuner.com/vbb/showthread.php?t=201450
              08 Element LX FWD AT 229,000 - MRT: fleetw00d : 2008 Honda Element LX - CB7Tuner Forums

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                #8
                Originally posted by fleetw00d View Post
                The engine speed will vary directly with the rolling radius of the (front) tires (not the wheels). A 195/60-R15 tire has a rolling radius of about 12 inches. A tire with a rolling radius of 13 inches would reduce the rpm at a given speed by a factor or 12/13 (about .923). For example, at whatever speed your car runs with an engine speed of 3000 rpm, a 13 inch tire would reduce the rpm at that same (actual) speed, the rpm would be 2769.
                thanks for the info

                Comment


                  #9
                  We do understand engine speed is the result of the amount of air and fuel being detonated at any specified time across each combustion cycle moving the crankshaft measured over a period of time (every minute), right? External forces are resultant at either the flywheel or flexplate (depending on your transmission type) act as additional loading which reduces engine speed.

                  Something along the lines of what an old chief engineer would say in this situation.

                  Have you considered all possible external forces? Weight perhaps?

                  What about the sensors and what each one measures?

                  Hmmm.

                  Wheel speed is dependent on engine RPM and the drivetrain gearing.





                  As fleetw00d said, overall tire diameter (an external factor) plays a role in acceleration. If you go up in diameter, you reduce acceleration. If you go down, you increase it.

                  Consider this. For roughly every 1.0" in diametrical change in tire size, there'll be ~+/- 150 rpm change to engine speed. Something you will probably never notice on your tach. So, go back and look at my original response and questions.
                  The Lord watches over me!

                  "Stop punching down on my people!!!"

                  - D. Chappelle

                  Comment


                    #10
                    Originally posted by 5acramento View Post
                    car is a 92 ex accord ..

                    mostly highway approx 70 mph

                    i know about the speedometer mismatch when changing sizes as well ..

                    i was just sitting back after dabbing some Larry Bird and that crossed my thoughts

                    i was looking at a tire comparison site and trying to match some 17's to stock 15's when i thought what if i went up either sidewall or to 18's ( granted weight be close ) would that in any way shape or form drop my rpm's significantly ???
                    Honda tends to gear their cars fairly low, since they tend to have relatively low torque and tend to make it at relatively high RPM's. Even their "low revving" NA engines, tended to keep the RPM's very close to 3K or slightly higher at 70MPH. It does make a tiny bit more noise, but doesn't really hurt the engine in anyway, so it probably is not really "strained." Some of Honda's higher revving engines could be close to 4K at those speeds, still with no ill effects.

                    Unfortunately, outside of swapping gear sets or going ridiculously bigger on the tire size, you aren't likely to move the RPM's more than a few hundred at that speed. Of course, if you start increasing your tire diameter, there are also penalties associated with that, as well as the penalties associated with lowering your RPM, putting you in a less responsive part of the rev band.
                    The OFFICIAL how to add me to your ignore list thread!

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                      #11
                      Originally posted by Straight Success View Post
                      We do understand engine speed is the result of the amount of air and fuel being detonated at any specified time across each combustion cycle moving the crankshaft measured over a period of time (every minute), right? External forces are resultant at either the flywheel or flexplate (depending on your transmission type) act as additional loading which reduces engine speed.

                      Something along the lines of what an old chief engineer would say in this situation.

                      Have you considered all possible external forces? Weight perhaps?

                      What about the sensors and what each one measures?

                      Hmmm.

                      Wheel speed is dependent on engine RPM and the drivetrain gearing.





                      As fleetw00d said, overall tire diameter (an external factor) plays a role in acceleration. If you go up in diameter, you reduce acceleration. If you go down, you increase it.

                      Consider this. For roughly every 1.0" in diametrical change in tire size, there'll be ~+/- 150 rpm change to engine speed. Something you will probably never notice on your tach. So, go back and look at my original response and questions.

                      Yeah that 150 isn't to far from fleetwood's 230 calculator

                      So I'mma chalk it up to no ..


                      Thanks for the info Ill look into other factors

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