engine revs when lifting off gas - Page 2
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This is a discussion on engine revs when lifting off gas within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; Check if the cruise control lines are too tight. Someone had a problem where his car was revving by itself. ...

  1. #16
    Registered User driverj's Avatar
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    Check if the cruise control lines are too tight. Someone had a problem where his car was revving by itself. That's what he found to be an issue.

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  3. #17
    Registered User lukeskywrx's Avatar
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    You also got to thinks of all the load that the drivetrain causes on the engine, it had to spin all the gears, and diffs to move this 3000 pound object that you are sitting in. if you are holding in the gas to maintain a constant speed and suddenly press the clutch in and now all the engine has to do is spin itself it is going to pick up a few revs. to counteract this most people let off the gas just before clutching but if it is not timed right your revs are going to spike slightly.

    here is the little scenero i thought of. Imagine you are pulling a heavy load attatched to a rope. you are pulling at a constant speed untill someone cuts the rope without you knowing. you are going to pick up some speed as you stumble forword. unless you have some advances warning(aka someone letting off the gas)



    luke
    I just don't get this drifting thing, why would I spend money to put a car in the wall for a bunch of stupid 16 year olds with dreams of fast and Furious?

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    Blobeye Syndicate #17

  4. #18
    Registered User Retro's Avatar
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    This has nothing to do with you taking your foot off the gas too late. I had my car acting up a lot one day and I practiced specifically taking my foot all the way off the gas, and then clutching in. I believe it's just a little bit of throttle lag, and if you can perfectly time the gas out, clutch in, then it may happen.
    clutch, shift, gas, clutch, shift, gas, shift, clutch, gas, clutch gas, shift... oops!

  5. #19
    Registered User Rich10's Avatar
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    It happens when my car has boost. My take on it is as follows. When you remove your foot from the throttle and simultaneously press the clutch, the intake system still has pressurized air. In order to avoid a lean situation, the ecu will provide gas. At this point, the engine has no load on it. With the pressurized air in the intake system, the additional gas and no load, the engine revs higher.
    2002 WRX WRB

  6. #20
    Banned hippy78's Avatar
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    lol. The ecu is always providing gas for the air going into the engine. This way the engine can keep going. The question is whether the engine's getting enough gas/air to raise the rpms or not. It's obviously a problem with your foot action. If your foot came off the throttle earlier, less air would go into the engine causing the ecu to put out less gas and the rpms would drop. If your foot's on the gas too much (so that there's enough air gas to make the rpms go up) when you put the clutch in, the rpms will go up. That's just the way engines work.

  7. #21
    Registered User driverj's Avatar
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    I am just curious. Is this your first manual?

  8. #22
    Registered User dome's Avatar
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    I had the same problem for the first 2-3k miles, but now it seems to have gone away. I didn't consciously change my driving style, but it has pretty much disappeared.

  9. #23
    Registered User wrxwex's Avatar
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    this is my first manual car , and this is only my third day having it(350 miles later), but i knew how to drive manual pretty well before getting it, and im getting better everyday, so it could be my error, but sometimes i don't think it is...

    BTW BREAKIN IS WORSE THAN CHINESE WATER TORTURE!!!!
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  10. #24
    Registered User analog_909's Avatar
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    It is definately due to the heavy a$$ flywheel. When you let off quickly and put the clutch in, the motor/flywheel still has lots of inertia and when the load on it (drivetrain + road) goes away all that inertia still wants to keep going as much as possible. That's one reason why lightweight flywheels are so neat... RPM's are much more controllable.

  11. #25
    Registered User Retro's Avatar
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    Originally posted by analog_909
    It is definately due to the heavy a$$ flywheel. When you let off quickly and put the clutch in, the motor/flywheel still has lots of inertia and when the load on it (drivetrain + road) goes away all that inertia still wants to keep going as much as possible. That's one reason why lightweight flywheels are so neat... RPM's are much more controllable.
    It's not inertia from a heavy flywheel. The heavier the flywheel the harder it is to change your RPMS, that means it's harder to slow it down, and harder to speed it up. The more inertia the more resistance to change. The same thing would happen on a lighter flywheel, but it would be more responsive and possibly less noticeable.
    clutch, shift, gas, clutch, shift, gas, shift, clutch, gas, clutch gas, shift... oops!

  12. #26
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    here i was thinking that it was my huge doc martens hitting the gas a little bit
    Sunset Orange Metallic 2003 WRX

    aim- skrypaksWRX

  13. #27
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    yea some people don't understand the idea of inertia

    " a property of matter by which it remains at rest or in uniform motion in the same straight lineor spinning int his caseunless acted upon by some external force "

    only reason the revs would jump that much is from bad shifting technique.
    -----------------------
    2003 Black WRX

  14. #28
    Registered User PKer's Avatar
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    It's just a case of left foot getting ahead of the right.

  15. #29
    Registered User OffRoadWagon's Avatar
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    Umm, yeah guys, it's driving technique. Ever heard of a term called rationalizing? That's what you're doing right now if you think it isn't your driving. But who am I to judge? I'm sure you know exactly what you're doing with your driving, seeing as it's so many WRX owners first manual car (bad idea, btw), the clutch engagement is quite different from most other manual cars, you probably drive with your head right next to the B-pillar, and can't see your own hood. But yeah, most people these days are in control of their cars, not the other way around...sure...


    I mean come one people, hundreds of really smart people come together to produce one single product: a car. Some of these people have been doing it for years and years, probably more years than you or I've been alive. And suddenly you come on the scene, and it's something not designed right with the car??

  16. #30
    Registered User Fixxxer's Avatar
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    I've driven nothing but manual transmissions my whole life. I learned to drive stick on my parents' Porsche 911 Carrera. I had a 1980 MGB (4-speed manual). Then I got a 1994 V6 Mustang (5-speed manual) that I put a Vortech supercharger on (). Next was a 1999 Trans-Am WS6 (6-speed manual). And finally, I got the 2003 WRX.

    Considering the fact that I've never had this problem with any other manual tranny leads me to believe that it's something about this car that's doing it. Granted, the WRX is turbocharged and none of my other cars have been, but that shouldn't make a difference in the way you shift through the gears, should it (other than launching, of course)? I'm not trying to be a d!ck or anything... I'm really curious as to why this car would do it and none of my others would.

    -Lee

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