Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Kevin Wood]

... when using cruise-mine will go down two gears in quick succession, then change back up after a few seconds rather than building back to the desired speed more gently. (NOT in Sport mode)

It probably isn't going down 2 gears, actually. The box has a feature called "torque converter lockup" which activates when cruising to bypass the torque converter and improve economy. When the lockup comes in the RPM will drop by an amount dependant on the load - probably about 500 RPM when cruising.

When the box changes gear it has to come out of TC lockup so it will change gear and then lockup the TC again a second or two later. This is why the RPM rises when it changes down, and then drops a little in a second step as the TC locks up.

Cruise control is another system where the ECU doesn't have all the information the driver does. If the speed is dropping below that set on the cruise control the ECU will apply a proportional amount of throttle. That may result in the transmission changing down where a "real" driver would have avoided the change. All the cruise control knows is that it has to keep a constant speed.

Holding an auto box on the line at the stall speed is not really any different to pulling away with a caravan on the back on a steep hill. Bear in mind that 100% of the engine's output is being dissipated as heat in the fluid in the torque converter so don't do it for more than a few seconds and leave the car idling for a few minutes after the run to circulate ATF through the fluid cooler.

Kevin

[MickAP]

Reading this thread with interest, I pick up my auto Miggy next Monday.
It's will be the first ever auto I've owned in 33 years of driving. And yes on the test drive made the classic mistake of using my left foot to brake, I was bearly moving though. Lets see how many times I make that mistake when I get it.

Mick

[Andy H]

I have been wondering about the relationship between the air intake gubbins and the gearbox gear selection.

With my manual I learned where the power came in (4000rpm ish) and tended to either cruise below 3000rpm or 'make progress' by exploring 4000+ rpm.

The combination of auto box and cc don't seem to have any strategy to cope with the rapid increase in torque at around 4000rpm. If I was driving a manual I could change down & reduce the throttle opening to climb a hill smoothly where the auto+cc goes to full throttle & then changes down a gear.

I suppose I used to drive around the poor implementation of a variable length intake system but the auto doesn't.

[cruisetopoland]

Reading this thread with interest, I pick up my auto Miggy next Monday.
It's will be the first ever auto I've owned in 33 years of driving. And yes on the test drive made the classic mistake of using my left foot to brake, I was bearly moving though. Lets see how many times I make that mistake when I get it.

Mick

The first auto I drove was a Rover 216 auto loan car-given to me while my own identical, but manual 214 was in for another engine replacement. 
I got about half a mile, then tried to change down at the first island and used the brake pedal instead of the (missing) clutch.  This flat-spotted all the tyres and the guy behind aged about 10 years 

Tip if driving auto first time-take off your left shoe 

[omegadan67]

i take it hte miggy box wont take the abuse my volvo one did then ( i.e running it up the drag strip) at the lights on the strip engage 1st and sports mode T/C off left foot on brake hold at 3500rpm when green let the brake go

It handles it fine. Apparently   (only the stall speed is less, around 2.5k seems to be ideal. Apparently )

hmmmm not sure wether to try it now then or not lol, best not for time being till i get use to it, dont wanna be picking bits up of the autobox of the strip

This sort of abuse tends to burn out the torque converter on vauxhalls if used on a regular basis.

as for acceleration and performance an auto will be slow from a standing start and top speed however in general driving an auto could/should beat a manual due to its quicker responce when down shifting and selecting the right gear for load and engine speed that said its down to personal preference as to weather auto or manual is best  IMHO

[KillerWatt]

Reading this thread with interest, I pick up my auto Miggy next Monday.
It's will be the first ever auto I've owned in 33 years of driving. And yes on the test drive made the classic mistake of using my left foot to brake, I was bearly moving though. Lets see how many times I make that mistake when I get it.

Mick

As Kevin said, once you've had it for a few days you will subconciously "learn" what the box is going to do, and when it's going to do it...so you can compensate accordingly if you want something different from it.

For me, a manual box wins every time over auto.
But as I said earlier, a big motor (such as the V6 Mig) with an auto box is very nice to drive (that's modern day auto box BTW, not the crap we had 20 odd years ago).

[I_want_an_Omega]

Thats interesting as I'm sure that the AR25/35 is well over 20 years old having been pretty much the same as on my E reg Carlton ............

[Kate]

Thanks, I've really enjoyed reading this! I feel very well informed now!

[cruisetopoland]

... when using cruise-mine will go down two gears in quick succession, then change back up after a few seconds rather than building back to the desired speed more gently. (NOT in Sport mode)

It probably isn't going down 2 gears, actually. The box has a feature called "torque converter lockup" which activates when cruising to bypass the torque converter and improve economy. When the lockup comes in the RPM will drop by an amount dependant on the load - probably about 500 RPM when cruising.

When the box changes gear it has to come out of TC lockup so it will change gear and then lockup the TC again a second or two later. This is why the RPM rises when it changes down, and then drops a little in a second step as the TC locks up.

Cruise control is another system where the ECU doesn't have all the information the driver does. If the speed is dropping below that set on the cruise control the ECU will apply a proportional amount of throttle. That may result in the transmission changing down where a "real" driver would have avoided the change. All the cruise control knows is that it has to keep a constant speed.

Kevin

Very useful and informative-cheers 

[Kevin Wood]

But as I said earlier, a big motor (such as the V6 Mig) with an auto box is very nice to drive (that's modern day auto box BTW, not the crap we had 20 odd years ago).

..big, not small, as I discovered on holiday this year when I was presented with a Seat Ibiza 1.4 Automatic hire car. 

Kevin

[cruisetopoland]

But as I said earlier, a big motor (such as the V6 Mig) with an auto box is very nice to drive (that's modern day auto box BTW, not the crap we had 20 odd years ago).

..big, not small, as I discovered on holiday this year when I was presented with a Seat Ibiza 1.4 Automatic hire car. 

Kevin

Three speed Perodua Kelisa EZi 989cc auto anyone?? POWER 

[HolyCount]

Reading this thread with interest, I pick up my auto Miggy next Monday.
It's will be the first ever auto I've owned in 33 years of driving. And yes on the test drive made the classic mistake of using my left foot to brake, I was bearly moving though. Lets see how many times I make that mistake when I get it.

Mick

The first auto I drove was a Rover 216 auto loan car-given to me while my own identical, but manual 214 was in for another engine replacement. 
I got about half a mile, then tried to change down at the first island and used the brake pedal instead of the (missing) clutch.  This flat-spotted all the tyres and the guy behind aged about 10 years 

Tip if driving auto first time-take off your left shoe 

What I did when first driving an auto (after 30 years in manuals) was tuck my left foot across behind my right leg, so it was out of the way and I was less likely to try to declutch with it.  Worked for me 

[Bill Cooper]

Kate

We have an Elite and have just got 35 mpg (at 68mph) on the main road sections from Penryn to Birmingham - so you can get good mileage, mind you round the lanes it drops a bit.  I supoose having just fitted a new Dispack helped with the mileage.  Enjoy the car, I have had autos for 20 years and have always been very pleased with them

Bill

[Auto Addict]

1. Is it ok to leave the car in drive all the time when you are out or should you put it in neutral at traffic lights etc.?
2. Are automatic gearboxes as reliable as manual ones?
3.Do you still have to get your clutch replaced when it wears out?
4.How is acceleration affected?
5. How is mpg affected?
6. Do you need to top up gearbox oil or anything like that?
7. If the gearbox fails is it economically viable to replace?
8. Is it expensive to replace?
9. Is it a massive job to replace?
10. Are automatics aimed at the older driver?

1) Yes, though if stood for more than 20s or so, i knock mine to N, and apply handbrake like a good little boy
2) No
3) No, it doesn't have one
4) Generally lower from standing start, but due to different gearing, may beat manual at certain other speeds
5) Generally much lower around town, often same ballpark on a motorway run
6) Ideally replace oil every 50-75k
7) With OOF, yes, viable! Otherwise, no
Breakers on OOF will sell then for £75-£120. Recon from specialist will be £500+
9) Difficult to do on your own
10) Not really.

Why?

A useful tip, if you want additional engine braking when going down slight hills, is to flick it into sports mode.

[Mr Skrunts]

An answer to your question one. If your sat in traffic for a long time & not really moving much, it's a good idea to select neutral or park (especially in hot weather). The gear oil will get too hot & this won't do it much good.
As for KW's control aspect, in slippery condition like snow for instance, auto's are better. (before some one pipes up & says blah blah. Remember JC in Iceland on the glacier with Icelander's )

Yeah with massive off road grippy truck tyres running at 4 psi.