[aargee]

Turning the key ON on any modern day motorcycle such as CBR 250R, Ninja 250/300, R15, R3 up to R1, Ninja H2 & S1000RR (or any fuel injected motorcycle for that matter), you can observe the tachometer making a full sweep from 0 up to the full RPM & back to 0 and hear the fuel pump priming. I also believe there's also a diagnostic checks being carried out during this sweep.

However take a car such as Honda City, S-Cross, Creta, Corolla, Innova, Scorp or i20 Active, I'm sure we can hear the fuel pump priming & to an extent understand diagnostics being run, but the tachos or speedos don't move a millimeter.

I believe very few cars DO have the speedo/tacho sweeping just like a tacho on motorcycles when the key is turned ON, but not all cars.

Any specific reasons as why the full sweep on all FI motorcycles please?

[suzuki san]

Hi aargee,

Believe it or not but the Nano has this feature.
I always wait for the full sweep and then a "click" sound before starting.

SS

[SmartCat]

I think its more of a gimmick and less of a feature. You know, like how tacho needle glows red as you approach 5000 RPM in certain cars.

[dark.knight]

The more relevant question would be why would the cluster sweep? The explanations are anything from doing the "sweep check" to ensure that the needles are working, or in warning the driver to wait until the sweep is done as the fuel pressure builds up in the line.

The reality of the matter is that the check is done more as a synchronisation guide within the cluster gauge, now I can post a confusing technical link here but let me first summarise that the cluster gauge is an instrument panel which is co-ordinated in a number of ways electronically. The speedometer is connected to the RPM gauge and vice versa, the fuel gauge has to react according to the weight of the fuel present and overall also has to interact with the speedometer to calculate estimated range, etc. This kind of information system is electro-mechanical and was largely used in older vehicles, and by default the sweep was programmed in as a system "check", not to see if the needles are working, but if the needles are co-ordinated. By this I mean that the RPM gauge needle and the Speedo gauge needle need to start at the same time and finish the sweep at the same time.. any nonsynchronism between the 2 would indicate that the cluster gauge is in some sort of fault and that the calibration is off. Yes I'm aware that the RPM gauge and speedo aren't supposed to be in-sync at all, as it depends on the gear but this is more of a reference check to gauge the accuracy during start-up that was programmed in electronically.

I'm more aware of the mechanical side of things and I really doubt that cluster gauge issues will reflect any serious driving flaw.. just more of an error in %age whenever you glance at the gauges, the RPM or speed might be slightly off from reality. In day-to-day driving I hardly even look at the cluster and sometimes reset the trip-meter after 6-8 months. I think this reason along with the fact that much of the instrumentation has gone digital (speed, average speed, mileage, fuel efficiency etc), brought an end to the sweep-check formality. Good question anyway.

Source: U.S Patent 07/935762 filed by Robert D.Dannenberg. Can be easily understood if reading complex legal terminology is a routine for someone.

http://www.freepatentsonline.com/5822335.html

[aargee]

Originally Posted by suzuki san

Believe it or not but the Nano has this feature.

Wow! Thanks for the info

Originally Posted by smartcat

I think its more of a gimmick and less of a feature.

But you see there's a pattern; all FI motorcycles have this "gimmick" but not all cars do. Even the cars that sell less in number than Nano don't have gimmick.

Originally Posted by dark.knight

The more relevant question would be why would the cluster sweep?

Thanks for the URL & expanding the word diagnostics technically. I'm trying to understand as why there's inconsistency with cars while unanimous in motorcycles on the sweep.

[tomraven99]

Agree that its a gimmick. At least on the new Thar cluster. The needles even sweep with only the power pins connected to the cluster. So I doubt its a diagnostic check up.

[SmartCat]

Thanks dark.knight was that insight!

Originally Posted by dark.knight

just more of an error in %age whenever you glance at the gauges, the RPM or speed might be slightly off from reality.

Originally Posted by aargee

I'm trying to understand as why there's inconsistency with cars while unanimous in motorcycles on the sweep.

I guess the key difference between car & bike engines is that bikes are revved aggressively more often (example, 2000 to 9000 RPM) than an average commuter car (1000 to 3000 RPM). Plus bike engines have higher rev limit (12000 RPM vs 6000 RPM) than an avg petrol car - so the tacho needle has to "traverse more".

So perhaps that's why calibration needs to be checked every time in bikes? To be reasonably accurate most of the time, across rev range?

[Viv3k]

On the motorcycles, it is not only the FI variants but motorcycles with carburettor also do the same. For example, the NS200 and I believe the entire Pulsar range do this.

However, barring the bigger motorcycles, I believe it is mostly a gimmick.

[Jeroen]

Originally Posted by dark.knight

The reality of the matter is that the check is done more as a synchronisation guide within the cluster gauge, now I can post a confusing technical link here but let me first summarise that the cluster gauge is an instrument panel which is co-ordinated in a number of ways electronically. The speedometer is connected to the RPM gauge and vice versa, the fuel gauge has to react according to the weight of the fuel present and overall also has to interact with the speedometer to calculate estimated range, etc. This kind of information system is electro-mechanical and was largely used in older vehicles, and by default the sweep was programmed in as a system "check", not to see if the needles are working, but if the needles are co-ordinated. By this I mean that the RPM gauge needle and the Speedo gauge needle need to start at the same time and finish the sweep at the same time.. any nonsynchronism between the 2 would indicate that the cluster gauge is in some sort of fault and that the calibration is off. Yes I'm aware that the RPM gauge and speedo aren't supposed to be in-sync at all, as it depends on the gear but this is more of a reference check to gauge the accuracy during start-up that was programmed in electronically.

]

I read through that patent. Still, I honestly think it is just a gimmick. But I have been wrong before. Has anybody seen an owner’s manual where this “check Procedure of the sweeping needles” is mentioned/explained?


Jeroen

[asingh1977]

I guess it seems to be a mechanical check by the cluster node. To show/check they are operational. Wonder: if the car will refuse to start if the full cluster sweep fails, on any one of the dials. Honestly, though: it looks quite cool on the Thar.

[suzuki san]

Not sure about what "diagnostics" are carried out during the "sweep" in the Nano but if I try to start the car before the sweep is completed and before I hear the distinct "click" sound, the car usually does not start. The service guys have also advised to wait for the "click" sound. Maybe it's the fuel pump. Anyway, it's now become a habit to wait for the "sweep/click" and then start the car.
This was never an issue in my previous Nano which dd not have the sweep facility.

SS

[GTO]

In most cars, it's just become a gimmick.

The XUV500 was the first mass market car to have the sweep. Loved it then, love it now, but only in cars with big engines. IIRC, the KUV100 does a sweep too, and it looked out of place in an economy car.



Am sure some dudes use a pic of the sweep to impress their dudettes - look how fast my car goes, baby!

Originally Posted by smartcat

You know, like how tacho needle glows red as you approach 5000 RPM in certain cars.

Not a gimmick in all cars. Some don't have a redline marking, so it helps.

[Jeroen]

My Jaguar runs through a diagnostic check. Shows up on the dash as diagnostick check in yellow letters when you turn the ignition on. Starting is disabled till the message disappears, takes maybe two seconds if that.

I make it a habit in all cars to turn the ignition on and wait one or two seconds before starting. I just like to give the fuel pumps to kick in and pressurize the fuel systems. That enables smooth starting I think. Especially on older cars, where pressure might not be retained that well after switching off. Some cars/engines are more susceptible to this than others. My Jeep Cherokee had this issue big time due to poor design of its check valve in the fuel system.

If your car never starts first time, but does start 2-3 attempt, try this approach.

Its not a big thing and I cant say how much good it does, but Im a techie at heart, so not rushing into these things is typically good, or at least not bad!



Jeroen

[SmartCat]

Originally Posted by Jeroen

I make it a habit in all cars to turn the ignition on and wait one or two seconds before starting. I just like to give the fuel pumps to kick in and pressurize the fuel systems. That enables smooth starting I think.
Its not a big thing and I cant say how much good it does, but Im a techie at heart, so not rushing into these things is typically good, or at least not bad!

This habit of yours will die a natural death when your next car comes with a push-button keyless start!

[arunphilip]

Originally Posted by Jeroen

I make it a habit in all cars to turn the ignition on and wait one or two seconds before starting. I just like to give the fuel pumps to kick in and pressurize the fuel systems.

Ditto. I also wait for the warning lights to turn off (i.e. the ones that turn off after a few seconds, not the ones that turn off only after starting).

Originally Posted by smartcat

This habit of yours will die a natural death when your next car comes with a push-button keyless start!

Umm, not quite. In my EcoSport, I first hit the push-button without clutch, which has the same purpose as turning the key upto just before cranking the engine (i.e. through two notches). I then wait for the lights to turn off, wait for little whines to stop, and then I push the clutch in and tap the button again to fire it up.

Although it is called the "accessory mode", it is equivalent to turning the key through two notches, not just one. See the extract from the manual that compares the key vs. keyless system for the EcoSport.