Looking to buy a 09 Manual, how's the throttle response?
I'm looking to buy a 09/10 manual. The dealer I went to days ago didn't have any, so I test drove the xB just for the hack of it. The car's fine, but the throttle seems to lag almost a second behind my foot. When I lift off the throttle, I'd expect the RPM to stop climbing instantly, but instead, I see RPM goes up another 700rpm or so. This is especailly annoying when accelerating onto the highway, I can even feel the buzz at the clutch, because the engine won't cut power quick enough, and I bet it's putting more wear onto the clutch. Down shift blip is just hopeless... The mazda 3 I tested later that day had much better response, and that had drive by wire as well.
So how's the throttle response on the yaris? With no tachometer it'd be harder to tell for me just from a short test drive.
If you still had the "COOL" light lit on the dash, that's normal behavior. Fast idle, intake cam timing fully retarded, spark retarded... If you have an automatic, it holds it in lower gears and makes it rev up till it warms up.
I'd expect it to cut the throttle slowly while it's cool and the catalysts aren't fully lit off, because there's a big pulse of hydrocarbon emissions when you close it quickly. That's why we've had dashpots on carburetors to slow the return to idle power ever since the early '70s. The deceleration fuel cutoff is also there for emissions suppression.
There is NO throttle lag in mine. Haven't experienced what some people are complaining about. Perhaps a misadjusted throttle pedal? Mine has an automatic transmission.
Throttle lag time just doesn't sound right at all. Whether the engine is cold or not there shouldn't be any lag time between the pedal and performance. The ECM should take care of all of that. I'd test drive another one from somewhere else and compare the two. I'm betting something is amiss on that car.
What he's describing isn't throttle lag. It's revving up when he pushes the clutch in, and sounds to me like it's just going up to the fast idle. Hard to be sure you're understanding when you're not there hearing it, though.
I have exactly the same problem with my 09 Corolla. The throttle response lags behind the thottle pedal by about 1.5 seconds. So when you upshift and take load off the engine by pushing in the clutch, the engine speeds up even though you don't have your foot on the throttle! This happens at ALL engine speeds, whether the engine is warm or cold.
It's kind of like typing on a real slow computer where there is a delay between when you push a key and the character shows up on the screen.
My wife took the car in last time and was told this was "normal". I'm taking the car in in a few weeks and will try to get to the bottom of it then.
This lag really makes the manual transmission difficult to drive smoothly. I find it odd that toyota would have a problem like this when you consider most of the Corollas sold around the world have manual transissions.
It really is frustrating enough that I would consider trading the car in soon for a non-Toyota.
If you have an automatic transmission, it'd be almost impossible for you to have the same symptom I'm describing.... they should be entirely different ECU programming, considering transmissions are all electronically controlled nowadays. And no it's not fast idle, this happens at any engine speed even after it's warmed up. I test drove the golf, mazda 3, none of them did this. Test drove a Saturn Astra, which did SOME, but not as much as the xB, the GTI I test drove almost felt like my 4AG in terms of response, and that's with a turbo strapped to it!
And yes, it's like a second or more behind my foot. And I'm amazed at how TOYOTA being what it is, can't seem to get this thing right..... first they took away all cars that are remotely fun, down graded rear suspensions to pre 80s technology. And now they don't even seem to test drive their cars anymore before releasing them to the market.... what the hell is wrong with toyota?!
The "over-run" is, in most cars, used to clean up vehicle emissions by providing a consistant burning of fuel that is in the engine. Otherwise, like "in the old days" you'd get a big old backfire and flames out the exhaust as the unburned fuel explodes and makes its way out.
I'd expect it to cut the throttle slowly while it's cool and the catalysts aren't fully lit off, because there's a big pulse of hydrocarbon emissions when you close it quickly. That's why we've had dashpots on carburetors to slow the return to idle power ever since the early '70s. The deceleration fuel cutoff is also there for emissions suppression.
I've driven a good many manual transmission cars since the '70s that revved when the throttle was quickly dropped and the clutch disengaged, because of the momentary throttle hold-open to decrease emissions.
In carburetors there's often a huge distance between the Jets and the cylinder, the throttle valve sits before all of that, and if you close it suddenly, yes, the next few cycles will be very very rich, since the fuel was already delivered for the air velocity that was there before the throttle valve was slammed shut.
We are talking about fuel injections here people! They are placed close to the intake valves, and they can be cut at any time the ECU says so. So really, it takes 1/1500 of a minute (0.04 second) to burn off the fuel if your engine is revving at 3000 RPM. Plus, any modern 3 way cat will clean up that tiny bit of unburned fuel without problem once it warms up ( remember fast idle when cold? ).
If you drove cars that revved after you've let off the throttle, back in the days.... I'm sorry.
You'd be correct if that were a complete analysis of the situation, but it's not. When the throttle's closed abruptly, there's a considerable volume of air in the intake manifold that will take several intake cycles to pull down to equilibrium manifold pressure. Instantly reducing the fuel injected would likely cause lean misfire and dump unburned fuel in the exhaust. More importantly, when the volume of fuel-air mixture admitted to the cylinder is not much greater than the residual gas left in the cylinder space, it may fail to ignite, or may burn slowly and incompletely. This is exacerbated when the engine's being spun faster than idle speed. Deceleration fuel cutoff is there to eliminate these problems while coasting, giving zero emissions at that time, but when the clutch is disengaged DFCO isn't an option. As for the catalyst, it can only more or less fully burn up fuel in a mixture that contains adequate oxygen, at the stoichiometric ratio or leaner, and gas rushing through it never reaches an equilibrium state. If the catalyst could be 100% efficient, there would be no need for any other emissions controls on the engine. The catalyst could take care of it all. We know that's not the case.
I'm not sorry I've driven cars that revved after the throttle was let off, back in the day. I'm glad I'm still here to share with you a tiny bit of the vast storehouse of knowledge, wisdom and insight I've acquired through my many long years of experience.
Truly a sad thing when a car maker find enough excuse to make driving fun a thing of the past.
quote: "When the throttle's closed abruptly, there's a considerable volume of air in the intake manifold that will take several intake cycles to pull down to equilibrium manifold pressure."
Equilibrium to what?
Several cycle to pull down, but without fuel or spark, it would just act like an air pump.
quote:"Instantly reducing the fuel injected would likely cause lean misfire and dump unburned fuel in the exhaust"
yes, but from your first sentence, you are implying that it should also dump EXCESSIVE oxygen along with it. The Catalyst needs oxygen to function correctly, if it's lean mixture, there should be enough oxygen for the catalyst to perform its duty, no emission control is perfect. and I don't see why there will be a "misfire" or lean mixture detonation if the ignition is cut.
This whole residual fuel thing in theory can be eliminated with direct injection, but that's not what we are talking about here.
"Deceleration fuel cut off", as you refer to, can't co-exist with coasting (If you meant constant speed coasting).. you still need to burn fuel to over come the pumping loss and the friction/resistance.
Quote: "when the volume of fuel-air mixture admitted to the cylinder is not much greater than the residual gas left in the cylinder space, it may fail to ignite, or may burn slowly and incompletely.This is exacerbated when the engine's being spun faster than idle speed"
You need to clarify this, EGR's job is to dump useless gas during very low throttle opening to reduce combustion temperature that can lead to excessive nitrogen oxidation, quite contrary to what you just said...(Or maybe you just didn't explain it thoroughly).. and why would this have to do with the issue anyways? Cylinder charging has a lot to do with the design of the engine; timing and duration of the valves, piping of the exhaust/intake system...etc.... simply comparing it to the idle speed is not at all relevant
If you go test drive other car makers such as VW, Audi, Mazda or BMW, none of them exhibit the same dissatisfaction. Plus, when the RPM shoots up and you engage another gear, it's more likely to experience a sharp and abrupt RPM drop, is that easier on the ECU when it comes to emission control?
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