what speed/revs should my autobox change gear

[Darkstar]

ive been having concerns lately, as the box did not seem to go into top gear and would be reving at 3000rpm at 60mph until about a few miles up the road i did a forum search and thought i read this was normal in the cold weather, went for a drive tonight ambiant temp was 14' and it changed up as soon as i got up to about 40-50mph.

i hope that things were ok??

[scanner]

Very generally speaking low revs in high gear doesn't necessarily mean maximum economy. If the engine is designed to cruise at higher revs it will not be working efficiently, a bigger throttle opening will be needed and more of the fuel will go through the engine unburned. This seems to bear out in the results I got from my manual car and motor bike when I switched to 3rd gear in 30mph zones instead of top when I had points on my license and didn't want any more. I wasn't really going much slower. just that it is easier to stick to 30 by ear that way. My fuel consumption was no worse, possibly better.

This thread is very useful by the way and explains a lot. My Bongo does not seem happy if I feather the throttle, and I have to use hold if I am doing a steady 40 or 50 or if I am behind slow traffic or it hunts and "unlocks" I think. If I can just put my boot down and do my own speed it is much better. I do have some transient problems with the gearbox because the hold light flashes sometimes usually preceded by delayed changes jerky changes and hunting. It is going into ADS to be checked,

With the bike that is probably because you were then cruising along much closer to peak torque revs which are usually quite high on bikes.

An engine is most economical when turning over at or about peak torque engine speed.

[Alacrity]

ive been having concerns lately, as the box did not seem to go into top gear and would be reving at 3000rpm at 60mph until about a few miles up the road i did a forum search and thought i read this was normal in the cold weather, went for a drive tonight ambiant temp was 14' and it changed up as soon as i got up to about 40-50mph.

i hope that things were ok??

Sounds fairly normal to me. In the cold weather you have to travel some distance before 4th will come in then a bit further before lockup. Is the engine running at the right temp? We sometime have cars in here with no 4th or lockup where the problem turns out to be a faulty thermostat in the engine (stuck open) not allowing the engine to get hot enough to allow 4th to be commanded.

[Diplomat]

Sounds fairly normal to me. In the cold weather you have to travel some distance before 4th will come in then a bit further before lockup. Is the engine running at the right temp? We sometime have cars in here with no 4th or lockup where the problem turns out to be a faulty thermostat in the engine (stuck open) not allowing the engine to get hot enough to allow 4th to be commanded.

I've been wondering for some while how this 'commanding' is carried out.

Would it be possible to:

Fool it into locking up at a lower road speed?

Deter it from coming out of lock up so easily?

Manually control the lock up range?


There sure would be a big demand for an aftermarket accessory that could provide these functions.


I drive mine most of the time with well below average gross weight and cannot see that I would be straining such a torquey engine in a high gear even down to about 30-35 MPH.


Frank

[Darkstar]

yes engine gets up to temp fairly quickly,

its just im straight on to a 60 mph road after 500 yrds, a bit concerned i was thrashing the engine

[Alacrity]

Mmmm, its all possible but it would mean getting a custom built ECU made & I can't imagine that would be cheap. Manually controlling it - in its simplest form would be easy, just cut the switch wire (usually a ground) to the lockup solenoid & switch it manually. You would have to wire a resistor into the ECU wiring to fool it into thinking the solenoid is still connected otherwise you will be stuck in 3rd gear only (default) with the hold light flashing. Then you could have lockup in all 4 gears if you wanted. I am not sure this would work with the 2000 > trans as I believe the lockup is regulated as opposed to straight forward on/off, although I am not 100% on this as I haven't seen one in the flesh so to speak.

The next one to do then would be to switch the overdrive (4th) in & out manually then you could have a 6 speed Bongo - think of the acceleration!

I am sure someone with electronics knowledge could build an ECU to do what you wanted - the Bongo's transmission really is very simple, but I am afraid that is all beyond this simple soul.

[Diplomat]

Thanks, Alacrity.

With fuel prices the way they are there is definitely an opportunity for an add on.

Probably better if it only locked up in 4th and possibly 3rd (for long but not very steep hills).


Frank

[Velocette]

Very generally speaking low revs in high gear doesn't necessarily mean maximum economy. If the engine is designed to cruise at higher revs it will not be working efficiently, a bigger throttle opening will be needed and more of the fuel will go through the engine unburned. This seems to bear out in the results I got from my manual car and motor bike when I switched to 3rd gear in 30mph zones instead of top when I had points on my license and didn't want any more. I wasn't really going much slower. just that it is easier to stick to 30 by ear that way. My fuel consumption was no worse, possibly better.

This thread is very useful by the way and explains a lot. My Bongo does not seem happy if I feather the throttle, and I have to use hold if I am doing a steady 40 or 50 or if I am behind slow traffic or it hunts and "unlocks" I think. If I can just put my boot down and do my own speed it is much better. I do have some transient problems with the gearbox because the hold light flashes sometimes usually preceded by delayed changes jerky changes and hunting. It is going into ADS to be checked,

Update ADS have replaced the throttle potentiometer and it has transformed the car, it changes up almost inperceptibly at low speeds without any revving or delay, haven't tried it out of town yet but will tomorrow.

[mikeonb4c]

I drive mine most of the time with well below average gross weight and cannot see that I would be straining such a torquey engine in a high gear even down to about 30-35 MPH.

Frank

A belated post in reply to this, but one big issue with the Bongo I think is that the turbo doesn't seem to do a lot below 40mph and I wonder if you would in fact be forever changing down due to lack of engine torque in top. On the other hand, my Bongo does seem to stay in the lower gears up to higher revs than I think it really needs to.

Velocette - is the throttle potentiometer different from the throttle position sensor, or are they the same thing? What was cost of replacing it, if it isn't rude to ask? I keep thinking that as Bongos get older, there must be an increasing number of components whose performance may deteriorate but without completely failing. Where replacement is cheap (thermostats and water pumps are two much discussed examples), ther is perahps a case for replacing them even if the Bongo 'appears' to be running normally (but how can you know what is normal unless you drive other similar Bongos, or else fit a replacmenet part like you did, whereupon the difference before and after was striking)

[rustyp]

I've been wondering for some while how this 'commanding' is carried out.

Would it be possible to:

Fool it into locking up at a lower road speed?

Deter it from coming out of lock up so easily?

Manually control the lock up range?


There sure would be a big demand for an aftermarket accessory that could provide these functions.


I drive mine most of the time with well below average gross weight and cannot see that I would be straining such a torquey engine in a high gear even down to about 30-35 MPH.


Frank

There is some adjust-ability, the throttle pot on top of the fuel pump can be moved around a little bit (I forget which way) but it simply fools the gearbox into thinking that less throttle is being applied than actually is. This means you can apply a little more throttle before it drops out of the lock-up, ideal for inclines.

It only needs a little adjustment by slackening the 2 screws and turning it. If I get the chance I will have a look to work out which way to turn it.

Russ

[rustyp]

The throttle pot/potentiometer/TPS/Throttle Position Sensor are all the same thing!

[Velocette]

I drive mine most of the time with well below average gross weight and cannot see that I would be straining such a torquey engine in a high gear even down to about 30-35 MPH.

Frank

A belated post in reply to this, but one big issue with the Bongo I think is that the turbo doesn't seem to do a lot below 40mph and I wonder if you would in fact be forever changing down due to lack of engine torque in top. On the other hand, my Bongo does seem to stay in the lower gears up to higher revs than I think it really needs to.

Velocette - is the throttle potentiometer different from the throttle position sensor, or are they the same thing? What was cost of replacing it, if it isn't rude to ask? I keep thinking that as Bongos get older, there must be an increasing number of components whose performance may deteriorate but without completely failing. Where replacement is cheap (thermostats and water pumps are two much discussed examples), ther is perahps a case for replacing them even if the Bongo 'appears' to be running normally (but how can you know what is normal unless you drive other similar Bongos, or else fit a replacmenet part like you did, whereupon the difference before and after was striking)

I think potentiometer denotes the type of sensor so yes it is a TPS but possibly all (non Bongo) TPS's are not pots. The fact is a pot suggests that it has an anologue function rather than open closed half etc' .

ADS charged £175.00 incl labour using a second hand part. New ones were £175 +VAT on Flea Bay.

Yes, when you think about it, it would be from 0 to 1/4 throttle where the pot track would get the most wear and that was the portion where mine would be skittish and hunt up and down the gears.

[mikeonb4c]

I drive mine most of the time with well below average gross weight and cannot see that I would be straining such a torquey engine in a high gear even down to about 30-35 MPH.

Frank

A belated post in reply to this, but one big issue with the Bongo I think is that the turbo doesn't seem to do a lot below 40mph and I wonder if you would in fact be forever changing down due to lack of engine torque in top. On the other hand, my Bongo does seem to stay in the lower gears up to higher revs than I think it really needs to.

Velocette - is the throttle potentiometer different from the throttle position sensor, or are they the same thing? What was cost of replacing it, if it isn't rude to ask? I keep thinking that as Bongos get older, there must be an increasing number of components whose performance may deteriorate but without completely failing. Where replacement is cheap (thermostats and water pumps are two much discussed examples), ther is perahps a case for replacing them even if the Bongo 'appears' to be running normally (but how can you know what is normal unless you drive other similar Bongos, or else fit a replacmenet part like you did, whereupon the difference before and after was striking)

I think potentiometer denotes the type of sensor so yes it is a TPS but possibly all (non Bongo) TPS's are not pots. The fact is a pot suggests that it has an anologue function rather than open closed half etc' .

ADS charged £175.00 incl labour using a second hand part. New ones were £175 +VAT on Flea Bay.

Thanks for that - price seems about right for TPS from a distant memory of dandywarhol discussing his on here a long time ago. Expensive little buggers that's for sure!

[bigdaddycain]

The amount of throttle application affects when and where the box changes up or down as a generalisation. For example, i managed a trip from Wigan to Cornwall without exceeding 2500 RPM through deft throttle use.

[Velocette]

The amount of throttle application affects when and where the box changes up or down as a generalisation. For example, i managed a trip from Wigan to Cornwall without exceeding 2500 RPM through deft throttle use.

I could do that now. I wouldn't have got to the end of our road before!