never asked before?

[Apache]

In the pursuit of greater economy, and pandering to the engineer in me...

I note that I have to be doing about 56 mph before I get into lock-up. I then drop out of it way to early in my opinion when following old farts or HGVs up the A49. Has anyone done any mods on the gearbox control electronics to change the lock out drop out point to lower speeds? I reckon the 3L could easily cruise along at 45mph in top gear...

Any thoughts?

[joe112]

In the pursuit of greater economy, and pandering to the engineer in me...

I note that I have to be doing about 56 mph before I get into lock-up. I then drop out of it way to early in my opinion when following old farts or HGVs up the A49. Has anyone done any mods on the gearbox control electronics to change the lock out drop out point to lower speeds? I reckon the 3L could easily cruise along at 45mph in top gear...

Any thoughts?

IMHO it wouldn't really be worth while... a lot of non exact research/guesswork has determined thqat to get the best mpg from a surf is to do between 50 and 60 every where...

Basically monday to friday the only place i go is work and back... exactly the same route and distance each day.. not really watching my speed or revs (although not thrashing it either (70-75 on motorway and 40ish in built up) would use £35 per week (5 days)

doing no less than 50 (where practical) and no more than 60 on motorway i can do the same distance on £20. this is keeping the revs at about 2500rpm


It is quite common knowledge that diesels perform best at 2500rpm - optimal torque etc

by altering the gearbox and hitting o/d early will put more workload on the engine and use more fuel

this is just my non scientific test and opinion which i have no way of backing up at all what so ever!!! i will probably be corrected no end but hey!! I do follow it though and reckon i get about 28-30Mpg on the average tank (unless i'm towing or in a rush of course!!)

Joe

[da SLUG man]

It is quite common knowledge that diesels perform best at 2500rpm - optimal torque etc

all diesels???

trucks don't even rev that high...

green band is between 1000 - 1500 rpm

very little pull above or below that.

[joe112]

all diesels???

trucks don't even rev that high...

green band is between 1000 - 1500 rpm

very little pull above or below that.

??????

Thats only just above tickover on a surf! isnt it??

[da SLUG man]

??????

Thats only just above tickover on a surf! isnt it??

yeah.

so not all diesels rev the same.

[Apache]

Might be an interesting experiment though. I'm sure given current technology it's possible to optimise change points better as the standard 'gearchange map' will be a compromise.

Is the gearbox under main ECU control or is it separate? I'm assuming that the sensors involved will include at least road speed and engine load, and I reckon that by doing a bit of manipulation to this data, one could change the point that the gearbox drops out of lock up.

Just a theory, I'll need circuit diagrams and a lot of coffee...

[Uplander]

Might be an interesting experiment though. I'm sure given current technology it's possible to optimise change points better as the standard 'gearchange map' will be a compromise.

Is the gearbox under main ECU control or is it separate? I'm assuming that the sensors involved will include at least road speed and engine load, and I reckon that by doing a bit of manipulation to this data, one could change the point that the gearbox drops out of lock up.

Just a theory, I'll need circuit diagrams and a lot of coffee...

Hi,
Very interesting points, luvly thanks am enjoying this "craic"....Dont, let anyone stop you or even slightly deter you in your mission to experiment, but jeez, let us ken what you discover eh pal ? BTW I think its more electronically controlled than mechanical, unless i am very much mistook !! well mine seems very computerised in it's habits !

Peter

[Apache]

So, can anyone point me in the direction of the relevant diagrams? A overview 'block diagram of what happens, and the circuit diagrams so I can instrument it to find out what goes on. Diagrams of the ECT area might be a good start because this changes the gear change points.

I envisage some sort of switchable gearchange maps. One I would like is something that allows the car to remain in lock up down to about 40 - 45mph so minimising gearshifts on A roads where I usually suffer some plank driving at *just* below the lock up speed in front of me. I'm sure I'll be able to develop some kind of optimal map to reduce the amount of gear changes and thus decrease fuel consumption.

[Steve Letts]

I think, from memory, (well actually from experience,) the lockup part of your torque converter is controlled via a solenoid driven by the a/t comp.
This gives you a couple of options,

1) You supply power direct to the solenoid, this overrides the a/t comp and the torque converter locks up. nice and simple, until you forget that you have left the lockup in and the a/t comp. tries to downshift....... Never tried this, but i imagine the result would be a very harsh shift, and in time damage to the clutch packs etc in the trans.

2) The a/t comp will activate the lockup solenoid under certain conditions, engine temp, speed and throttle postion. So the next method would be to fool the a/t comp into thinking these conditions are being met. The a/t comp will drop out of lockup if the throttle goes to the idle position, or if the speed falls below a predetermined value for the slected gear, or if you touch the brakes (to prevent stalling the engine if you should lock the rear wheels). As well, if the throttle goes above i think, 50%, it drops out of lockup as well to gain the 'torque multiplication effect' created by the small amount of slip in the converter. Therefore, if you can make the throttle appear stationary, the a/t comp will remain in lockup, regardless of what you do with the pedal.

3) remap the chip inside the a/t comp. I don't know if this ones possible.

There, thats my 10cents worth.
Most of the above I gained whilst trying to repair the failing trans on my old surf. It had dodgy speed sensors, shift soleniods, clutch packs, you name it, it had it. Most of the auto electricians, mechanics, trans specialists it went to had no idea, so I spent a fair bit of time trouble shooting it myself.

If you search for an A340 or A343 trans,(2nd gen had A340, 3rd gen A343, generally) made by aisin i think, thats a good starting point, you'll be surprised at what other vehicles they're in, beside the humble surf.
15 cents..

[Apache]

An interesting 15 cents too.

I tend to agree with your sentiments regarding simply applying power to the A/T comp to force it to stay in lock up. Sounds a bit inelegant. I am looking more to fool the appropriate sensor/s into thinking the conditions for lockup are present in limited circumstances. ie. When the vehicle speed is constant and load isn't increasing - which for me means, say, around 45mph constant speed in traffic. It seems ludicrous that a torquey diesel would not be able to pull the vehicle along satisfactorily in top gear at that speed, given now acceleration demands.

Cant mess with it at the moment as am away on business in New York, but this site gives me the familar feeling of home. Thank god for hotels with free broadband!

[Catfisher]

How goes the lockup

An interesting 15 cents too.

I tend to agree with your sentiments regarding simply applying power to the A/T comp to force it to stay in lock up. Sounds a bit inelegant. I am looking more to fool the appropriate sensor/s into thinking the conditions for lockup are present in limited circumstances. ie. When the vehicle speed is constant and load isn't increasing - which for me means, say, around 45mph constant speed in traffic. It seems ludicrous that a torquey diesel would not be able to pull the vehicle along satisfactorily in top gear at that speed, given now acceleration demands.

Cant mess with it at the moment as am away on business in New York, but this site gives me the familar feeling of home. Thank god for hotels with free broadband!

Fantastic someone trying to do what I have been thinking of. It is a pain to drive around single track roads reving just below lockup. I had a patrol before the surf and it would handle 25 mph and up in top gear. 4.2 nat asp diesel manual box. I averaged 27mpg in that with a best of 29.9. best I have had in the surf is 24.3 after a motorway journey. It is too dangerous to drive at over 50mph on some of the lanes I use on a regular basis but they are nice and flat and would be a doddle to tickle along in top.

Please keep us informed on the progress.

I found a control box on the web, do you think this could point the way?

http://www.powertraincontrolsolution...content-4.html


Also has a downloads section with some wiring diagrams.

http://www.powertraincontrolsolution...xe_harness.pdf

[Apache]

Thanks for the links. I will take a look. I haven't looked into it seriously yet - basically because it's too bl00dy cold and I'm a bit busy with a kithen extension, but when the warmer weather gets here I'll get it sussed and post a report on how it can be done.

[Chillitt]

you better sthtop kithing it, ith making your voith go funny

[Apache]

Thath'll be the Scothch

[kitesurf_phil]

I don't know if the 2.4 is designed to lock up earlier but mine does it a 50 MPH. It is OK most of the time, although it can make the truck suddenly go sluggish when building up to carriageway speed on slip roads. Flicking the overdrive off compensates pretty well.

I would be interested in something that would hold lock-up off until 60 MPH for when I have the caravan on the back, then I won't have Apache gnashing his teeth when he is following.