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damn, finally got it last night, and so far I have almost 400 miles on it. :p

stupid question time, I searched and couldn’t find anything, and the dealer had no clue either..

here goes...

When I get on the gas, then let totally off the gas and depress the clutch, the rpms climb up about 400-500rpms before dropping. Is this supposed to happen? The only thing I can think of is that it is supposed to happen to help keep the power up... It doesn’t happen unless I put the clutch in.. And yes, Im 100% sure Im off the gas.
 

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It's caused by the "fly by wire" throttle control. The gas pedal is not mechanically connected to the throttle.

I noticed this as well. I did find that it decreased over time. Not sure if it's the ECU learning or the driver learning.
 

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:eek: WTF?!
So what is going on there, is it actually better for the engine to keep revving a little longer after the pedal is released or is this just a glitch in the "fly by wire" programming? The main attraction of the "fly by wire" throttle is quickened throttle response, which is obviously, when depressing the pedal but shouldn't it also quicken throttle response when releasing the pedal?
I'm completely baffled....
 

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How not to get a car out of the snow

The main attraction of the "fly by wire" throttle is quickened throttle response, which is obviously, when depressing the pedal but shouldn't it also quicken throttle response when releasing the pedal?
My feeling exactly. Recently had to remove the neg cable from the battery to do some work which also reset the ecu. I noticed that "rev jump" after letting off the gas again. I believe there is some ecu learning that decreases that.
 

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I know what you are talking about, it is a bithc when you shift at 7k cause it takes a while for the car to learn so when you have like 2k miles on her and you pull a 7k shift and you are not careful the revs will shoot deap into redline, as my friend showed me. But anyways, just learn the car and let it learn itself, and i have 4k miles on her, and i dont have that problem at all anymore.
 

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I don't think it's a problem with the fly-by-wire programming, just a function of remaining gasses in the engine and the inertia of the turbine in the turbo. When you get off the gas and push the clutch in, you're decoupling the engine and tranny. However, since there's still exhaust gasses flowing through the engine, and the turbo won't stop spinning immediately since it has a ton of inerita, it will continue to spool, creating boost in an unloaded engine. The recirculation valve redirects most of the air, but there's still some exhaust gasses left that need to be vented. So basically, it's like blibing your throttle at idle. If you guys are really on the throttle, it's really noticable (RPM jumps up on mine about 500 RPM) since there's a lot of boost. But if you're tooling around town with little to no boost, the RPM doesn't jump up when you shift...
 

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2534082

I think the reason the revs shoot between shifts is simply because of physics and inertia. Without sounding nerdy, your clutch is connected to your drivetrain.

When you depress the clutch, the drivetrain is disengaged from the engine flywheel. During this disengaging point, the flywheel is still rotating and still has a pretty high moment of inertia, but it doesn't have the drivetrain load. This then causes the engine to slightly overrev because you've removed the drivetrain load from the engine.
 

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If it was just due to what you are all saying it is than that would be ture of all turbo cars, and it isnt. I have driven many turbo cars and none of them have that problem.
 

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I too would agree with Thunder except for the fact that it changes over time. And when I reset the ECU, it went back to the way it was.

I really don't know though..............
 

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um...why does everyone shift at redline? at 7000rpm you'd be way past the horsepower peak and in the red by the time you complete your shift. there is a phenomenon called valve float that occurs at redline and is usually a determining factor as to where redline should occur. i have my rev light set at 6000rpm just to be on the safe side. there are occasions when you can't watch the tach.
 

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Out of the top of my head, the best shift point will be around 6500rpm, because when you shift into the next higher gear, your rpm's will drop below the peak HP (maybe 5800?) ... That way you will be gearing up your next shift towards the peak HP.
 

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Someone mentioned that this was intentional programming of the throttle by wire for emissions. Basically, when you let off the gas quickly, that's when the car will produce a lot of combustion byproducts (I'm not sure if it's unburned hydrocarbons, NOx, or some other nasty), so the throttle is programmed to stay on a little longer in order to clean things up a bit. I'm not sure if the idea is to protect the cats or if the extra emissions would make it through the cats.

Has anyone else noticed that when they're coming to a stop and you depress the clutch early (say at 40 mph when stopping completely to zero) the rpms will stay pretty high (around 1000 to 1200 rpm) until you come to a complete stop, then they drop?
 

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Fhqwhgads said:
Has anyone else noticed that when they're coming to a stop and you depress the clutch early (say at 40 mph when stopping completely to zero) the rpms will stay pretty high (around 1000 to 1200 rpm) until you come to a complete stop, then they drop?
This happens with my RSX as well but not consistently. It is weird.

BTW I just noticed the post that said if you shift at redline your RPMs fall to above 5k? I would have figured the STi would be geared to fall closer to 4k? If that isn't the case you must have to shift a LOT in the STi and probably explains the low trap speeds.
 

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What rpm you shift at is also determined by what mods you have on your car, casue stock you probably should be shifting closer to 6,500rpms than 7,000rpms. However once you are getting into modding the car you should shift as close to red line as possible, cause generally moded STIs pull there peak numbers right at red line or just before it.
But for where you want to shift your sti it is more complicated, if you really want to get down to it you need to deceid what rpm you want to shift each and every gear.
When you redline first and shift into second you are at about 4,600rpms, however if you shift your car at 6,500rpms you are going to be at about 4,100 rpms. And in a stock sti you make 225hp at 4100 and you make about 260hp at 4600 rpms. So it is benifical to run the car to redline in first because of the power that you will lose going into second cause at 6,500rpm you make 300hp and at 7,000 you make 280hp. However as you progress up the gears your gears are closer which keeps the rpms closer...like when you shift from first to second you drop to 4,600rpms, but when you shift from second to thrid you only drop to 5,200rpms, and when you shift from third to forth you drop to 5,500rpms (assuming that you are redlining).
But i ran through all of the math for optimal shifting on a STOCK sti and here is basically what you want to do
1st-7,000
2nd-7,000
3rd-6,700
4th-6,700
remember those are for stock stis, if you have anything more than a intake and exhaust, you will want to bring that all the way to redline(generally) it depends on how your dyno chart looks. These numbers are going off of the aps stock dyno curve. But every car is different and every mod makes a differance. Like my stock v6 camaro but down best times shifting at 5,200rpms when the red is at 5,800 and my b16crx makes best times shifting at 8,200 and red is 8,200.
 

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i was reading something in one of the bike magazines about best performance and acceleration not always coming from shifting at redline. however i am still not set at shifting at redline. seems to a shift does not occur instantaneously. you have to push in the clutch shift the gear and then let the clutch back out. that takes time, so if your Shift light is set at say 7000rpm, by the time you get the shift started i think you'd be past redline. optimum shift points can be figured out mathematically but it also has to do with driver skill. i have my REV light/buzzer set at 6500rpm just to be on the safe side.
 

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It might sound funny, but i have my shift light set at 7,000. I am used to shifting at the track without a shift light, so i have it there as a safety. I usally shift at about 6,800 and having it set at 7k is my way of know that i am not over reving the engine.
 
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