Safe Speed Forums

My GF has just returned a hire car, a brand new Vauxhall Vectra, now OK the Vectra is not exactly renound as a drivers car and she was going to hate it because it's wrong wheel drive, but her major complaint was the half a second lag between doing something with the accelerator and the throttle actually responding.

Not only does this make smooth driving impossible, since it's much harder to time the clutch+accelerator correctly it's also a safety issue since if a pedestrian steps out, you will lift off and go for the brakes but in the time it takes to move between pedals the car will continue to be applying the throttle instead of providing engine braking, thus increasing the stopping distance and effectively increasing the reaction time.

My only explanation for this behaviour is that the accelerator is electronically controlled via CAN-bus, but I suppose Vauxhall could have innovated some other way to make a drive-by-wire system with a crappy response time.

Surely this trend is a safety hazard waiting to happen and could do with being stopped. At least the brakes are still mechanical... for now.

I’ve driven many modern Vauxhalls. I can confirm many are slow to respond, both going on and coming off the throttle. I have experimented with these: I give it some gas, then take my foot completely off, then depress the clutch - the engine still revs up, then eventually comes down. I thought it was just due to how they were mechanically set up?

However, it should not affect braking performance during emergency braking because you’ll depress the clutch too. Full on servo assisted modern brakes surely don’t need extra assistance from the engine!

I was thinking of the time between coming off the accelerator and onto the brakes, on a normal car this would cause a little bit of deceleration, rather than continuing to accelerate.

What about the opposite situation where you need to accelerate to get out of danger, then it's a bigger hazard I guess.

Also what is wrong with a good old fashioned throttle cable?

That would depend on how quick you are with the clutch. Even then your point is still valid: better to have a bit of engine braking than nothing. Unless you are revving in a low gear, I estimate typical engine braking would provide 0.1G. Coupled with the 0.25 second transition time from gas to brake pedal, this would translate to an additional 0.5mph scrubbed. At ~60mph, that would mean a difference of 1 meter - around a 2% difference.


I've never been a fan of this; thankfully I've never been in a position where I've had to rely on it.

Nothing wrong with CAN. All modern cars use drive by wire throttles.

The delay is due to poor calibration. Nothing you can do about it. It is a "fix" to meet emissions standards.

Modern powertain CAN networks operate much faster than you can detect.

You get what you pay for and Vauxhalls are cheap as chips. Drive a BMW if you want to know what a propper drive by wire throttle should act like.

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Hmm, I've recently gone from an Omega with cable-driven throttle to one with an electronic one, and I honestly haven't noticed any obvious difference in their throttle responses. The electronically driven pedal is considerably lighter underfoot, which was very obvious the first few times I drove the car, but now I've got used to that it seems to drive about the same as the old'un - the only performance difference now seems to be down to changing from a 3l to a 2.6l engine. Makes me wonder what VX have done wrong to mess up the current Vectra throttle response when they seem to have been capable of doing a decent job of it in one of their older designs...

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Chris

The slow response for throttle on is very poor. The slow response for throttle off is almost certainly driven by the need to meet emissions. On all manual cars since - well, ages, there has been a dashpot arrangement to prevent sudden closure of the throttle, thereby expelling all fuel burnt. Or so they tell me.

Another reason to have an auto

The Detroit engine Peterbilts I drove in 1997 had potentiometers on the accelerator pedal not cables and they drove lovely. Like Gizmo said it's the emmisions gubbins. Not sure the throttle cable on my 1998 Honda has anything on the end of it that ever see's petrol, I imagine it operates s widget that tells the injectors how much fuel to administer.

It's not just for emissions. Once you give the car control of the throttle, it can start doing smart-arsed things with it for traction and stability control. I notice it in my Peugeot 807 sometimes. If I really "horse" it into a bend, it kindly lifts off the throttle for me to help keep me nice and safe (ta!). If lifting off the throttle doesn't kill the understeer, it will start messing about with whichever rear brake is likely to make it tighten its line until I'm back going the way it thinks I want to go. Similarly, when I'm trying to charge up the icy hill not far from my house, it helpfully cuts the throttle to reduce wheelspin. It also lightly applies the brake to the wheel that's spinning if only one of them looses traction. I can turn it off but it comes back on again above 20MPH whether I like it or not!

From the emissions point of view, the lag might be largely down to the idle speed control valve. As has been said, some are better than others. Modern engines run so damned weak at idle that they'd practically stall if the cooling fan or the aircon pump cut in. The iddle speed control is supposed to combat this (and usually does) but it also seems to make the throttle response really poor. I love getting into my old car and blipping the throttle - it's absolutely instant, like a bike, almost!

So to summarise, it's an attempt to remove the need for any skill at all and wrap up the driving experience in as simplistic an interface as possible. What is ofter refered to in the IT industry as a "point and drool" interface.

It certainly explains a lot about Vectra drivers, so in that respect it was a worthwhile experience, I guess. I understand why they never indicate now

Have you tried using the Vauxhall 'Smart' Indicators, when I had several Astras whilst waiting for the C4 theywere all plauged with electrical faults, hold it on to get a proper indicator flash but only get one or two, the other common problem was a light touch kept turning the main beam on instead blinding oncoming cars.

A truly, truly god awful set of controls, how long have we had click on/off indicator stalks?? They work so why change them to something that doesn't.

Would never touch a Vauxhall again unless I had a gun to my head!!

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They take some getting used to huh? Even now I occasionally get confused with them.


Unfortunately I have no choice because they are our company's car of choice! I try to use the Signum whenever possible

I had a new shape vectra for 3 years (just replaced with a proper car). Bloody indicators

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was it a diesel? if it was, it is probably turbo lag

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go for it

No it was petrol.

And given that my GF drives a 200SX with an uprated turbo, FMIC, boost controller, custom ECU map and other upgrades, I think she would know if it were turbo lag.

ha ha, fair enough

S13 or S14? I really want an S13, but I don't have the money or time to maintain it

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go for it

S13.

And yeah, I know what you mean on the maintenance. Rust and big ends mainly