FreedomPenguin

Lol
This isn't a race car, stop trying to blame the car. It's meant to be driven not raced, I don't have a hang on mine how I drive, I'm not trying to race my 180hp engine, weaker than a Subaru.

It's a comfortable drive and feels nice. The clutch will only wear to that of the drivers style.

TomCat_tC

Hey John - I was the one who made the original post on this issue. 18 months after buying my car, I too, have never gotten used to the rev hang. Along with the throttle lag - I am surprised that a car like a Scion can be so challenging to drive without spinning the clutch or stalling on occasion. I have owned at least a dozen manual shift cars. While it has not cured the rev hang, the Sprint Booster I installed has made the car a lot more tolerable to drive. As I see it, the only real cure for the rev hang would be to replace the lead flywheel, which I am nor prepared to do until the engine comes out for some other purpose.

novanasty

Just thought I'd throw another 2g drivers experience in real quick. I have driven many manual vehicles in my day, and the throttle lag on dbw systems can be annoying a first, buuut you get used to it. I've had my RS8 for over a year now and I don't really pay any mind to the throttle lag anymore as I've gotten used to it.

The rev hanging, however does get annoying. But only does it on a cold engine in the mornings. RPM's never hang when I shift on a warm engine. I always watched my driving really close and always make sure I'm not leaving my foot on the accelerator for that split second after I push the clutch in, leaving the RPM's hanging where they left, or even rising slightly.

My explanation to this rev hanging problem, for me at least, as stated before does not hang on a warm engine, is that when you first start your engine, and its cold (meaning not operating temp, not cold outside) the ECM has the engine in open loop, otherwise called "cold start enrichment". Meaning the ECM is trying to get the engine to operating temperature as fast as possible because the engine does not make acceptable emissions, or is truly efficient until it reaches operating temp. One of the many ways the computer does this along with injector pulse width being longer, is keeping RPM's up. I'm sure everyone has noticed when you first start your engine, it stays anywhere from 1-2k rpms until it starts getting warm. And when you jump in your car and start driving as soon as you crank it, you're still in open loop for the first few miles until your engine gets hot. And an annoying combination of a dbw throttle system and open loop results in an annoying rev hang until the engine warms.

Like I said before, mine only does it on a cold engine. I've never experienced it on a warm engine. Hope this helps someone understand why it does what it does. Theres not really much you can do about it, unfortunately.

TomCat_tC

Having read Novanasty's message, I can say that my car's rev hang experience is consistent, cold and warm. The only performance change I notice with my car is that the synchro for second gear (manual transmission) is a little sticky when the car is cold, but goes way when it warms up. The explanation provided by Novanasty makes perfect sense. However, my rev hang is persistant at all times. I have come to live with it, but I will never like it. I still think it has more to do with the weight of the flywheel than the ECU. However, this is just a guess, and I could of course be wrong. If anyone can convince me it is the ECU, then theoretically a new chip could fix it, right?

Hey, what do you want for $19,500? It's good value for what it sells for.

novanasty

I definitely think it's an ECM issue. When you think about it, the computer doesn't know when you're going to shift, when you're going to push in the clutch. So when you do, you could say you're catching the computer off guard, and as fast as computers work, for that split second when you take the load of driving the vehicle off the engine, the computer is going to maintain injector pulse width, air flow into the engine, ect. Thus is why we have rev hang. So the computer could be making changes to compensate from substantial engine load, to no engine load as quick as it can, but the engine is spinning with a lot of force and momentum and it's hard to change it in a split second. Just one of the few cons of driving a dbw car, and I don't think there's much that can be done about it unfortunately.

johnmk

Hi novanasty,

You have good background knowledge but you're wrong on our car. There's no rev hang when engine cold. Shifts as any manual should shift, with regard to rev hang , when engine cold. Once it's closed loop, that's when the really annoying rev hang begins. That means once the car is warmed up, it shifts like Queen Mary. Those first few minutes driving on a cold day, oh how I savor them. :-)

stevenj

I am a new member (car engineer by profession) who was interested in discovering the cause of rev hang in cars fitted with drive-by-wire throttle. I looked into this issue in depth when I recently bought a new 5MT Toyota. I did some tests and published my findings with graphs and videos here: http://www.revhang.altervista.org

My conclusions are clear: for emission compliance reasons modern cars are deliberately designed to keep injecting fuel in the engine for some time AFTER throttle pedal (not necessarily the throttle valve) was closed to idle. Rather than decelerating instantly, cars keep moving forward with throttle closed when gears are engaged, or engine revs are not dropping or even rising slightly when declutching quickly. From safety perspective I consider such a function questionable. IMO, drivability of such cars is adversely affected, unless one learns to live with the rev hang or even like it :-).

Drivers not keen on spirited driving can avoid the rev hang by waiting for 1 to 3 seconds (depending on the car model) after closing throttle before disengaging the clutch in order to change gears smoothly. Other drivers, who bought manual transmission cars for enjoyment, are simply out of luck. No change of heavy flywheel for a lighter one or installation of after-market throttle controllers can alter the effects of OEM programming of fuel injection ECU. A "tune" could possibly do that, if it was available.

In the end I succeeded in completely deleting the rev hang in my car by my CUREVS device (stopping the flow of fuel to the engine at the right moment) and believe it would work equally well in other cars, with appropriate software settings.