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Thread: shifting early - driving at low RPM bad for the engine? valve ticking?

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    Registered User nsxexotic's Avatar
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    shifting early - driving at low RPM bad for the engine? valve ticking?

    Over the past years I have noticed lugging the car, shifting way to early and forcing the motor to pull away at low RPMs/high gear at low speeds contributes to valve tick. Is this true?
    Is there any kind of damage that can arise from shifting to early and causing the car to pull at low RPMs?


    I have changed my driving habit on the NSX shifting 2500-3500 RPMs during NORMAL driving.

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    Modern engines should have no problem with shifting early - you can drive your X with 1,000 revs in any gear if you like.

    With low revs however you have less noise from the exhaust and may hear the valves ticking louder - but I doubt that they are really louder.
    www.fastvoice.de - english (okay, some kind of)/german with NSX content

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    Registered User jgtcnsx's Avatar
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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    nah i dont think thats true
    symbolic motors (mechanic)
    www.symbolicmotors.com

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    If you drive around constantly in low RPM, you will foul your plugs.

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    If you do not keep the rpm's up under load (over 2000 rpm) the oil pressure will decrease cause premature wear

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    Quote Originally Posted by W and hk4site
    If you drive around constantly in low RPM, you will foul your plugs / If you do not keep the rpm's up under load (over 2000 rpm) the oil pressure will decrease cause premature wear
    Any proof or reasons for this statements? I have the lowest oil pressure near maximum rpm on long straights, during low rpms the gauge says I have high oil pressure.

    And: Shouldn't modern engines and plugs (especialy our wonderful platinum plugs) be able to deal with lower rpms?
    www.fastvoice.de - english (okay, some kind of)/german with NSX content

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    Registered User hlweyl's Avatar
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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    Quote Originally Posted by NSX-Racer
    I have the lowest oil pressure near maximum rpm on long straights, during low rpms the gauge says I have high oil pressure.
    That doesn't seem right to me NSX-Racer. The oil pressure should increase with engine rpm. Are you sure that wasn't stated backwards? I am by no means an expert, but I would have that looked at, maybe something wrong with the sending unit, sump or even the gauge.

    I absolutely agree with your statement regarding modern engines dealing with low rpm. The ECU controls ignition timing so I wouldn't worry too much about fouling plugs OR premature wear. This is assuming that we are talking about useable RPM range. That is, you are not "bogging" the engine.

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    Quote Originally Posted by hlweyl
    That doesn't seem right to me NSX-Racer. The oil pressure should increase with engine rpm. Are you sure that wasn't stated backwards?
    Yes, I am. As you can see here:
    http://www.nsxprime.com/forums/showt...ht=oilpressure
    and in other threads I'm not the only one with that experience.
    www.fastvoice.de - english (okay, some kind of)/german with NSX content

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    I just read that thread and has me wondering what the final verdict was. It seems that it was an issue with the stock sending unit/gauge/gauge location. When a mechanical oil gauge was hooked up in a more ideal location, the mechanical gauge was going up as the stock gauge was dropping.

    Woops, straying off topic now....

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

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    If you do not keep the rpm's up under load (over 2000 rpm) the oil pressure will decrease cause premature wear
    This is believable. Here is a story - my father owned a 89 Legend with a little over 100k on the clock. It was purchased use and did not have noticable valve noise at that time. Gradually the car got louder and louder in terms of valve tick. It got so bad he had to sell the car for cheap.

    His driving habits were shifting extreamly early. Causing the rpms to dip under 1000rpms. Sometimes he would be in 5th gear doing 30mph.

    anybody have some insight on why some NSX with same mileage and year have different degrees of valve noise?

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    Quote Originally Posted by NSX-Racer
    Any proof or reasons for this statements? I have the lowest oil pressure near maximum rpm on long straights, during low rpms the gauge says I have high oil pressure.

    And: Shouldn't modern engines and plugs (especialy our wonderful platinum plugs) be able to deal with lower rpms?
    Yes, with my car. I was known to drive and shift like a granny and when it came time for my 90,000 mile service (done at 85,000 miles) my plugs were the most fouled that the NSX mechanic had ever seen. They were by far the most fouled plugs that I have ever seen. I used to shift at 2500-3000rpms since I lived in a very quite neighborhood and had a loud exhaust but was told not too shift so early or risk fouling my plugs. I was also told to ring the car out every now and then to help clean out the fuel injectors.

    I'm not sure what you are proposing with our 'modern' engines and platinum plugs. My car has a motor designed in the late 80's.

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    Quote Originally Posted by W
    I'm not sure what you are proposing with our 'modern' engines and platinum plugs. My car has a motor designed in the late 80's.
    Hey, isn't that modern? I heard of american cars where the engines were basicaly designed in the late 40s...
    www.fastvoice.de - english (okay, some kind of)/german with NSX content

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    ok, well, i just spent a half hour typing out a killer answer for you guys, but then it wasn't accepted and was lost in cyberspace. a second order problem has arisen in that, while polishing my margarita recipe for XPO, i found the perfect combination of tequila, blue curacao, and grand marnier, that has since kicked my butt into dumbass mode (which wasn't much of a punt, by the way).

    short answer: low rpm and high gear are a bad combination for multiple reasons. don't do it. cruise min 3k in any gear, unless straight & level. accel min 3k starting point. there's a reason your tach says 3k at 70 mph.

    secondary answer: while at the track yesterday, i also noted low oil pressure at high rpm. both the car and i survived just fine. i burned up my rear brakes, although after prolonged cause-and-effect analysis, i don't think the two are connected.
    dave
    94 black/tan
    Who winces at the thorn dare not seek the rose.

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    guess i'll start changing my shifting habits.

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    Quote Originally Posted by zomby woof
    ok, well, i just spent a half hour typing out a killer answer for you guys, but then it wasn't accepted and was lost in cyberspace. a second order problem has arisen in that, while polishing my margarita recipe for XPO, i found the perfect combination of tequila, blue curacao, and grand marnier, that has since kicked my butt into dumbass mode (which wasn't much of a punt, by the way).

    short answer: low rpm and high gear are a bad combination for multiple reasons. don't do it. cruise min 3k in any gear, unless straight & level. accel min 3k starting point. there's a reason your tach says 3k at 70 mph.

    secondary answer: while at the track yesterday, i also noted low oil pressure at high rpm. both the car and i survived just fine. i burned up my rear brakes, although after prolonged cause-and-effect analysis, i don't think the two are connected.
    Heck, I'm more interested in the drink recipe.

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    I used to drive my car (Volkswagen) 300'000 km within 10 years with very low rev (1500 - 2250) and 3/4 throttle and had no problem at all. The car is still running and will run much more but I sold it 2 years ago. AND: I saved a lot of fuel/money and bewared me of a lot of noise and tire wear
    With 3/4 throttle the car stays in his most economic fuel range at low revs and if there is some torque there's fun enough too and the spark plugs don't get dirty If you stay above 1500 rpms you won't have any problems at all.

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    Registered User hlweyl's Avatar
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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    Very interesting discussion. It seems to me the NSX is completely comfortable cruising at 2000 rpm. I don't feel any "bog" at all. Logic would tell me that I am getting less wear at 2000 rpm than 4000 rpm, plus better fuel mileage.

    I would completely agree if we were talking about trying to accelerate up a hill at 1000 rpm. I've ridden with people doing stuff like that and you can hear the engine detonating big time.

    I'd be interested to hear someone with knowledge in the matter to chime in and be specific as to what rpm, what speed, what gear, etc. And are we assuming that the engine in question NEVER gets ran in upper rpm range? I would assume the original posters intent was that this was his normal driving habits but I would assume that he would actually run the engine in the upper rpm ranges (how could one not ) occasionally.

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    Registered User nsxexotic's Avatar
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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    Hey thats me (original poster).

    My used to be (old) driving habit was to shift early consistently. For example shifting around 2000+ rpm range when crusing. I thought this would be ideal for long term reliability but after doing some research I find that your shift point should somewhat be in close relation on how automatic vehicle shifts.

    The data on low oil pressure at low RPMS could overtime cause valvetrain noise from insufficient lubrication??? opinions?

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    Registered User hlweyl's Avatar
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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    The way an automatic shifts is different. It takes into account throttle position and engine rpm whereas a manual WE choose.

    As far as valvetrain noise, I would say it depends: what rpm and speeds are you talking about? Do you notice the engine "bog"? That is, that low deep sound with possible detonation (knocking sound). A modern engine will try to prevent detonation by adjusting the timing but you can still do damage. So that would by my non-expert answer: it depends.

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    My shift points are hardly ever below 4K, and usually closer to 4.5 or 5. I realize it's totally unscientific, but the feedback I get from the engine makes this feel right. All I know is that the NSX V6 loves to spin, and I am happy to oblige!

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    Ok, I’ll try again. After further review of Bosch’s Automotive Handbook, and no margarita’s this time…

    By up-shifting at low rpm, you’re asking your motor to deliver power at its point of lowest “mechanical advantage”, which means you’re forcing the pistons, wrist pins, con-rods, crank, and journal bearings to accept the force of a large explosion pushing against a relatively unmovable object. Sketch out the kinematics and you’ll see what I mean. Yeah, I know the titanium con-rods have better fracture toughness characteristics than your standard NASCAR-issue steel con-rods, but the wrist pins and crank bearings are still susceptible to shear and just plain getting the crap skwarshed out of em. And the aluminum pistons are getting a hot fire on their face with no way to get away from it.

    Continually running the motor at low rpm forces it to operate at less than desirable volumetric efficiency, which means that there’s not enough breeze flowing through the motor to blow out all that heat and combustion by-product adequately. Resultant to that is that the motor doesn’t achieve a good internal operating temperature, which allows the aforementioned gases to cool, and condense into gunk which will then apply itself to your plugs, pistons, et c.

    Due to valve overlap, along with the stated low volumetric efficiency, some of those gunk-producing gases can emigrate out of the combustion chamber and blow back and settle onto the valve seats, or maybe even all the way around the valve, to collect on the stems and in the seals. That may not contribute directly to a loud valve tick, but it will likely eventually contribute to worn seals/seats. Then again, gunk buildup in the valve seat area would preclude full valve closure, effectively increasing the gap between cam & valve, making a louder tick.

    Further downstream, your catalytic converter has to purify this flow, and, because the cat-con isn't hot enough, the same gunk-laden gases cool and condense in there, further reducing efficiency of the breezes flowing through your motor.

    Herr Bosch points out, however, that a 4-stroke engine has “very good volumetric efficiency over the entire engine-speed range, low sensitivity to pressure losses in exhaust system, as well as relatively good control of the charging-efficiency curve through selection of appropriate valve timing and intake system designs.” What that means for us is that we probably don’t have to worry about gunked-up motors as much as in the old days, because Honda-san gave us some good electronics (and VTEC at the upper end of the rpm spectrum), to account for most of the undesirable low-efficiency effects. However, there’s still that nagging kinematics problem that can be cured only by changing lifestyle habits.

    Give your motor a break. Shift at 4k, 5k…any additional induced wear is less of a concern than shearing wrist pins, burning pistons, fouling plugs, or squashing the guts out of your crank bearings. And you don’t have to spend a half-hour at high rev’s while you’re shifting. Make a moderately spirited acceleration, shift, have a little fun, listen to the motor sing, and then get into cruise mode. It’s a Honda!
    dave
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    Who winces at the thorn dare not seek the rose.

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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    You forgot something....*cough*recipe*caugh*

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    Registered User nsxexotic's Avatar
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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    Thanks for the write-up zomby woof.

    "A good friend of mine also mentioned that subaru 2.2 and 2.5L engines very commonly develop a valve tick. subaru has a TSB about it, and it mentions telling customers with manual transmissions to not 'lug' the engine when driving up hills because it could contribute to valve tick...also - the 1.8L turbo subaru motor... lugging it can cause head gasket falure"
    (copy and paste so pls excuse the grammer)

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    Registered User zomby woof's Avatar
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    Re: shifting early - driving at low RPM bad for the engine? valve ticking?

    this is my world-famous (at least in texas and geelong, victoria, australia) get-you-laid-but-don't-even-THINK-about-driving-home margarita recipe. a couple of these babies and you're clothes will absolutely rip themselves from your bod' (dude, you're in my light)

    1/3 cup cuervo gold
    1/4 cup blue curacao, triple sec, or grand marnier
    a salty rim on a 12-ounce tumbler
    5-6 ice cubes
    margarita mix to fill the glass

    metric users will have to make the conversions. sorry.
    dave
    94 black/tan
    Who winces at the thorn dare not seek the rose.

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