Idle Speed

[Parnelli Bone]

This may seem trivial to some of you here, but only recently did I realize the cars in GT4 have different idle speeds.

I was letting my new Buick Regal GNX sit there rumbling before a practice run and (being a mechanic/shop worker) I could tell the engine was running at a bit of a higher pace than usual. Sure enough, the tach said 2000 rpms! I put in another car (a Civic I think). The idle on this car was much lower...about 550. 💡

It's a bit of realism I don't think anyone has noticed but being a car freak I think it's cool. All the cars in GT2 (for instance) idle at about 750 rpms no matter what make or model. 👎

 

[TuneRVisioN]

Try racing cars like the Skyline GT-8, Mitsu CZ3 street car, Lancer VII GT-A and others that shift while literaly gain speed shifting even on a uphill. They go 10MPH if you dont press anything, even on a flat surface (EXAMPLE: Take your Lancer VII GTA in arcade mode out for a spin on the test course. Stop completely when on a level surface. Let go of every single button, now watch the car go up to 10MPH on a flat surface. The gas bar on the left will indicate that you are lightly pressing X and you arent even pressing anything. Must be a glitch. It will also move forwards by itself on slight uphills.)

 

[Dark Elite]

I'm pretty certain this is related to automatic gearboxes. If you depress no pedals while in gear in most automatics cars, they will 'crawl' forwards until their actual speed equals engine idling speed in first gear, so that the engine can be fully engaged - hence the car adding throttle on its own when you stop and let off the brakes.

DE

 

[Greycap]

Far from a glitch as Dark Elite points out, all those cars (and some more too) are automatics or CVT's in the game, hence the seamless shifting (torque converter or CVT doing its work) and the unusual engine sound when the gears are changed. As a sidenote, these cars lose their automatic gearboxes when upgrading to tuning transmissions.

- R -

 

[G.T]

I'm pretty certain this is related to automatic gearboxes. If you depress no pedals while in gear in most automatics cars, they will 'crawl' forwards until their actual speed equals engine idling speed in first gear, so that the engine can be fully engaged - hence the car adding throttle on its own when you stop and let off the brakes.

DE

Then why do manufactures sometimes decide not to do this with some of their automatic transmissions?

My father has driven several automatic cars which do this, but when he drove a Chrysler 300C, it just sat there not moving at all.

 

[DLRgian]

Each engine and cpu has its own idle speed.

 

[TuneRVisioN]

Ohh ok I don't know too much about cars so I thought it was a glitch. Thanks for the responses.

 

[Philly]

Now I'm wondering why it is just those cars that do this. My idea is just that those are auto-only cars so they were designed like that. After all, wouldn't it make sense for all automatic cars in the game to do that? I'm sure real life cars that are offered with a manual creep too.

 

[Sharky.]

these cars lose their automatic gearboxes when upgrading to tuning transmissions.

The Skyline GT-8 doesn't lose it's automatic-ness when you fit a racing tranny - AFAIK it's the only car (CVT or auto) where a racing tranny doesn't make it manual.

(but the racing tranny bungs up 7th and 8th - 8th becomes shorter than 7th )

Side note: Giving a Prius a racing tranny gives it normal dials, rather than the standard energy monitor thing.


On topic: I've noticed the varying idle speeds. Of course, higher-revving cars should have higher idle speeds.

 

[Dark Elite]

(but the racing tranny bungs up 7th and 8th - 8th becomes shorter than 7th )

This makes me think that it not becoming a sequential manual is a glitch... Maybe it was meant to be a sequential seven-speed with the Racing Transmission, and got messed up - hence the useless top gear. You can't even tune gears to be like that in other cars, as far as I know. I haven't driven the car myself (I'm trying to avoid it ) but I might have to check that one out.

Perhaps the Prius' electric motor is disconnected when you fit a Racing Transmission?

I'm not sure about all real-life automatics doing what I described in my previous post, but all those I've tried have. All manual cars will move at engine idle in first gear too, you just need to be very careful with the clutch pedal. Seeing as GT4 doesn't tell us what the clutch is doing, however, it's safe to assume that with no brake or throttle pressure, GT4 automatically disengages the engine.

DE

 

[Parnelli Bone]

Yeah, all the GT games disengage the engine from the clutch automatically. In GT3, I got in the habit of hitting the e-brake (using L2 for e-brake) sometimes to make the clutch and engine truly disengage! This don't work in GT4 though...instead the rear tires immediately lock up when you do this even momentarily.

It's interesting that the GNX rumbles at 2000 rpms, though. I know for instance that drag-racing cars have to idle fast otherwise they'll literally stall. PD must have somehow found info on idle speeds for various cars.

 

[jessekatianda]

My favorite car in the game, the SL55 AMG also does this crawling.

It's just the nature of the automatic based transmission of the car, which I absolutely love.

 

[DLRgian]

Could be the torque maybe? My Dodge Durango on idle in gear crawls.

 

[Sharky.]

the SL55 AMG also does this crawling.

\/

automatic based transmission of the car

That's why.

 

[Parnelli Bone]

No, some cars haven't had their ATF fluid topped off, that's why they don't crawl

..just kidding...

 

[Metar]

So is it safe to assume, learning from what I read, that autos, or manuals in some instances (if they have enough torque low down), crawl even when nothing is pushed. If torque is enough, they crawl forward, and if not, it stalls?

 

[Dark Elite]

As I mentioned earlier, Gingiba, in real life pretty much any manual car (that is in good condition) will 'crawl' forwards with no throttle above standard engine idle speed, from the Ford Fiesta to the Lotus Exige. I've yet to drive a car incapable of doing it on a level. On a hill, however, a stall is more likely.

In the game, I haven't ever seen a manual do this - which is because, or so it seems, GT4 does not engage the clutch until you add throttle above engine idle speed. With the Mercedes SL 55 AMG, you will probably find that the car will stop doing this 'crawling' when you fit a Fully Customisable Gearbox, as this (if I recall correctly) removes the automatic gearbox in favour of a manual.

DE

 

[Metar]

As I mentioned earlier, Gingiba, in real life pretty much any manual car (that is in good condition) will 'crawl' forwards with no throttle above standard engine idle speed, from the Ford Fiesta to the Lotus Exige. I've yet to drive a car incapable of doing it on a level. On a hill, however, a stall is more likely.

Then you haven't seen our car yet. An ancient 1.4l trying to pull 1.4 tonnes stalls quite often.

Cheers for the explanation, though! *tick*

In the game, I haven't ever seen a manual do this - which is because, or so it seems, GT4 does not engage the clutch until you add throttle above engine idle speed. With the Mercedes SL 55 AMG, you will probably find that the car will stop doing this 'crawling' when you fit a Fully Customisable Gearbox, as this (if I recall correctly) removes the automatic gearbox in favour of a manual.

DE

So basically, in GT4, cars with automatics won't disengage the "clutch" (or whatever those 'boxes use), therefore producing the same 'crawl' that any real-world car will exhibit, yet the manuals will actually disengage the clutch when at a stop?

If so, then this works together with that odd whizzing sound you hear on (I think) all cars when you're moving at about 10-20KM/h. I haven't tested it much, but I've noticed it mostly on racecars, where it's much louder, or the Caterham 7. It's a high-pitched sound which seems to be "turned on" as soon as you start accellerating, yet dies out when you're idling. Could that be the sound of the drivetrain then? When going downhill with the clutch disengaged, there's no sound - yet with throttle, there is. Perhaps it's got something to do with this?

Sorry if it's a little cluttered and unclear

 

[TuneRVisioN]

Now I know why cars crawl by themselves... They didn't teach me in this so called "Automotive School..."

This forum tought me alot more about cars than the Automotive School I went to. 👍

 

[Parnelli Bone]

Then you haven't seen our car yet. An ancient 1.4l trying to pull 1.4 tonnes stalls quite often.

Cheers for the explanation, though! *tick*



So basically, in GT4, cars with automatics won't disengage the "clutch" (or whatever those 'boxes use), therefore producing the same 'crawl' that any real-world car will exhibit, yet the manuals will actually disengage the clutch when at a stop?

If so, then this works together with that odd whizzing sound you hear on (I think) all cars when you're moving at about 10-20KM/h. I haven't tested it much, but I've noticed it mostly on racecars, where it's much louder, or the Caterham 7. It's a high-pitched sound which seems to be "turned on" as soon as you start accellerating, yet dies out when you're idling. Could that be the sound of the drivetrain then? When going downhill with the clutch disengaged, there's no sound - yet with throttle, there is. Perhaps it's got something to do with this?

Sorry if it's a little cluttered and unclear

That whizzing sound is the gearbox, correct. You only hear it on some cars in the game when they are upgraded with a with a full-custom or close-ratio (sports or semi-racing) gearbox. Full racing cars like the Toyota TSO20 will usually have a full-custom box already installed and will always have gear noise.

When many cars(in the game) are equipped with their stock gearing, they'll usually have no gear sound since cars sold to us by the dealer are supposed to be "quiet" (in real life) Make sense? Imagine some yuppster test-driving a Lexus only to have tons of gear-noise flooding the interior!

Real-life cars generally do everything possible to avoid gear-noise by using syncronized gears that mesh a certain way. Reverse usually doesn't have this mesh, which is why when we back up we hear that wrrrrrrrrrrr noise.

 

[djblackmon]

Yeah, all the GT games disengage the engine from the clutch automatically. In GT3, i got in the habit of hitting the e-brake (using L2 for e-brake) sometimes to make the clutch and engine truely disengage! This don't work in gT4 though...instead the rear tires immediately lock up when you do this even momentarily.

Try it on AWD cars, I can do it in GT4. I do it all the time in STi's and Evo's. Just tap the e-brake really quick when driving and the car goes to idle. You can also rev it if your in a lower gear that if the clutch catches it will redline(ex. hit redline in 3rd, tap e-brake, put it and first, and it will revv.)

 

[Speed Drifter]

Real-life cars generally do everything possible to avoid gear-noise by using syncronized gears that mesh a certain way. Reverse usually doesn't have this mesh, which is why when we back up we hear that wrrrrrrrrrrr noise.

Well that's almost correct, but the noisiness depends more on what type of gear wheels are used in the box.
straight cut gears usually whine a lot so manufacturers tend to use cogs which are cut in a slight angle like in the pic below

 

[Metar]

Alright - perfectly clear! Cheers and +reps to both of you! Now I understand all that stuff...

 

[Parnelli Bone]

Well that's almost correct, but the noisiness depends more on what type of gear wheels are used in the box.
straight cut gears usually whine a lot so manufacturers tend to use cogs which are cut in a slight angle like in the pic below

Exactly. That's what I was trying to say about the way the gears mesh. 👍 Reverse is often a straight-cut which is why it whines in a real-life car.

 

[Dark Elite]

An ancient 1.4l trying to pull 1.4 tonnes stalls quite often.

(that is in good condition)

Anyway, if you are extremely (and I mean extremely) careful when letting out the clutch, surely it will crawl on a smooth, level surface? Have you tried it like that? If the engine in engaged slowly enough, just about any engine can do it. Most cars you hardly have to think about it, it's that easy to just ignore your right foot altogether

Back to the current discussion...

I thought that reverse gear often whining was something to do with the wheels/axles turning in the opposite direction to what they were designed for?

Any thoughts on this? I don't know enough about the way drivetrains work to rule out this possibility, or to accept it.

DE

 

[lightfox]

The automatic crawling behavior may not be desirable in real life. This happens to me.

Drove a rental car to NY. Stopped at red light. Looked down to read a map to figure out where the heck I was. I guess I didn't press the brake strong enough so it was not in affect. And since I was looking down, it is hard to notice the car is slowly crawling forward. Then horns everywhere, I looked up and I was in the dead center of the intersection looking at cars headlights left and right!

--

 

[Dark Elite]

Paying attention negates this undesirable side-effect.

DE

 

[Mad Matt]

Automatics work in a variety of ways. A torque converter creeps (as I understand it) because the fluid that the two "blades" sits in, is always slightly viscous so the engine idling pulls you forward.

A DSG gearbox works differently in that it's in fact two gearboxes and a wet clutch, but ours creeps too. I think that's because, in drive, the clutch is slightly engaged even when stationary.

I know a CVT is to do with the "elastic band" and the difference in distance between the drive train and the engine, but I assume they have some kind of clutch for when you’re stopped at lights.

What's strange in the game is that you can choose to drive a car that was only available as an automatic in manual mode. I also noticed that the automatics drive more like a DSG in sports mode. You don't really get kick down, for example.

 

[Tulok]

i havent ever gotten an fr cars to crawl... but i have gotten my self to roll down a hill while revving for a short time(the rx7-1996). The sir-II(eg) will really kick if i rmember correctly.
Low in 4th---"no look downshift"-*Pop*3eeeeeeeeeeerddd/lurching forward then smoothing as you increase rpm

 

[GT_KING]

another car that crawls on idle is the jaguar XK-R.