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Thread: Harmful to downshift causing 4k rpm?

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    Senior Member fc321's Avatar
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    Harmful to downshift causing 4k rpm?

    I was driving at 40mph (in 4th gear) and downshifted to 2nd gear when I saw red light ahead.

    Rpms climbed to a little over 4000 rpm as a result of this. Maybe it was 4500 actually

    Is this harmful behavior? Is that pushing things too far?

    I should also add that car was only driving for 6 minutes so not fully warmed up yet


    2015 Mirage DE 5 speed Manual (no bluetooth) nickname: "Agile Grey Rat"

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    Still Plays With Cars Loren's Avatar
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    Quote Originally Posted by fc321 View Post
    Is this harmful behavior? Is that pushing things too far?
    Not even close. Redline is 6500. Maybe it's not a bad idea to keep it under about 5000 when it's cold. But, these cars warm up fast. After 6 minutes of driving in Miami... it's pretty much warmed up.

    If you revved out 2nd gear all the way to the rev limiter, you'd be going 54 mph. So, if you're going less than 50 and you downshift to 2nd, you're not going to hurt the engine at all, totally within its normal operating range. Might be a little hard on your clutch if you don't rev-match it. But, the engine will be fine.

    Don't try going into FIRST gear at that speed, though! That's exactly what killed my engine. Top speed in first gear is around 30. If you grab first at 50+ mph... you're definitely over-revving the engine.
    Simplify and add lightness.

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    I would suggest rev matching on downshifts like that if you aren't already to save wear and tear on the clutch, but otherwise, as Loren said you aren't going to hurt anything.

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    Or just drop it into neutral when coasting towards a stop light.

    And in a quick stop you dont need to downshift. Just push the clutch and brake in at the same time. Let the brakes do their job.

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    Senior Member fc321's Avatar
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    Thanks guys,

    The first year I owned this car (and I had not driven a stickshift in over 10 years) I used Neutral ALOT, I mean ALL THE TIME when going to a red light or even a stop-sign but this year I have been downshifting more often. In this case would downshifting into 3rd have been appropriate? Or just to go into Neutral? it took me about 5 seconds to get to the red light (that had just changed to red).

    But maybe I should quit downshifting for the purposes of slowing the car down? I certainly dont want to wear out the clutch earlier than necessary.

    I've never learned to rev-match. I thought that was for racers.
    2015 Mirage DE 5 speed Manual (no bluetooth) nickname: "Agile Grey Rat"

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 44.9 mpg (US) ... 19.1 km/L ... 5.2 L/100 km ... 53.9 mpg (Imp)


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    Still Plays With Cars Loren's Avatar
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    If you're into hypermiling, downshifting and leaving the car in gear as you coast up to a stop uses less fuel. (look up "DFCO") But, I've found that it's hardly worth downshifting to 2nd for that purpose. Just grab 3rd and coast down until you hit about 1100 rpm, then clutch in for the stop.

    It's not a bad idea to "be in a gear" when your'e driving in traffic. Always ready to dig out of a sticky situation when it comes up. You just never know when something stupid is going to happen and you might need to ACCELERATE to get out of the way. Can't do that if you're in neutral.

    As for rev-matching, it can REALLY smooth out your driving. It doesn't take much. Just blip the throttle when you clutch in for a downshift. Just enough to get the revs up close to where they will need to be after the downshift. Doing so makes for a seamless downshift that is easy on your clutch, your synchros and your gears, doesn't "upset" the car, and is just plain smooth. Try it!

    I didn't used to do it until I got into track driving. Then I learned to do it. And, as mentioned, downshifting is good for hypermiling, so I downshift a lot. And I rev-match every downshift. It becomes a reflex after a while.

    Without rev-matching, the car lurches forward when you downshift. With proper rev-matching, you should feel nothing.
    Simplify and add lightness.

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    You can pretty much coast down in whatever gear you're in and drop to neutral not far from a stop, but even if you downshift you can get really good at just knowing the speed to do it without rev matching. Just do it a bit later than sooner if unsure. The only time I use rev matching is if I'm coming down a bit quicker for a turn.

    I use neutral a lot. And the mirage is so light it slows quickly anyway. I'd rather use a tad bit of brake then clutch to slow down
    Brakes are easy and cheap, clutches aren't.
    And even if you're coasting down in neutral its ultra fast to snap it in gear and go if needed.

    For extra credit and to try an advanced technique, try upsgifting without the clutch. I used to do it sometimes in my Mustang GT. If you hold the shifter with a bit of pressure against the next gear as you're accelerating it will slide right in when the gears match.

    I have not tried with the mirage
    Last edited by Pryme; 01-25-2019 at 04:00 AM.

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    Still Plays With Cars Loren's Avatar
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    If you're really good, you can upshift AND downshift without the clutch. Handy skill to have for when you lose clutch hydraulics (or a clutch cable in the case of the Mirage) and need to get home.

    The Mirage has a well-synchronized transmission and does that sort of thing just fine. Just takes a little practice and an understanding of how things work.
    Simplify and add lightness.

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    As for the original concern, yes 4000 RPM engine speed should not cause a problem.

    It is my experience that the Mirage saves more fuel by coasting in neutral than in gear. My advice is for saving fuel, coast in neutral unless you want extra drag to slow down for a stop. Either way, the difference between the two methods is slim. One method preserves momentum, the other doesn't.

    Also, better to wear down and replace brakes than clutches. Save your clutch and don't use the practice of downshifting for deceleration. The brakes serve that purpose just fine.

    Matching the speed of the transmission input shaft to the desired gear and vehicle speed saves synchronizers. It is easier when you memorize the engine speed v. vehicle speed for the various transmission gears. Make a fun game of it to see how close you can get.
    Last edited by Eggman; 01-25-2019 at 09:12 AM.

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    Downshifting to 4000rpm wont be any issues. I would down shift MORE if the car actually had engine braking...the **** box tune mitsu puts on the car it has next to no engine braking ability.


    2018 mirage ES manual

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        click to view fuel log View my fuel log 2018 Mirage Es 1.2 manual: 41.6 mpg (US) ... 17.7 km/L ... 5.7 L/100 km ... 50.0 mpg (Imp)


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