diesel auto box changes vs consumption

[rossocorsa]

In many ways love the car comfy with great handling for a big car and of course always a great place here to go for advice!! What annoys me a little bit is the gearbox hanging on to a relatively low gear when I just know I'd be in a higher gear in a manual it really hits economy, today on a run driving on a mix of A roads and dual carriageway I managed my best ever consumption but only by being very careful to coax the gearbox to stay in the highest gear possible and gentle acceleration usual open road speeds 55 to 70mph

http://i724.photobucket.com/albums/ww247/rossocorsa/mgtf/ztfuelconsumption.jpg?t=1287093088

in general running on my daily run to work of about 15 miles each way I'm lucky to keep above 35 mpg . I do need to do a box oil change and have the oil in the garage ready for a dry weekend to get it done but beyond that I'm wondering just what makes the box decide what gear to be in? Will an out of spec MAF effect changes via the information from the ecu? (mine could be a bit tired) If a ron box was fitted does it fool the ecu into holding gears longer as the ecu doesn't see all the fuel injected? (although as my ins co want about £80 extra if i fit one.....) Any thoughts guys?

[Godders 75]

I find I have to play about to get that, final gearchange sometimes,when iam doing about 52 i just ease off the gas and the rev counter drops from just over 2k to 1.6k, but i havent managed to get as good as a result as you.
Godders 75

[Robson Rover Repair]

Ive ready about a gearbox ecu update before, im unsure about when specifically it started being standard, but it might be worth exploring that from a T4 dealership.

[rossocorsa]

Ive ready about a gearbox ecu update before, im unsure about when specifically it started being standard, but it might be worth exploring that from a T4 dealership.

yep I saw something about that before but i've never seen anything definitive and also the official consumtion figures never changed so I reckon it could be a red herring. It does amaze me a bit how the box hangs onto lower gears though it really must have affected the official mpg/CO2 figures. I also read somewhere (I think) that in cold weather the box holds onto gears longer to improve warm up???

[Godders 75]

yep I saw something about that before but i've never seen anything definitive and also the official consumtion figures never changed so I reckon it could be a red herring. It does amaze me a bit how the box hangs onto lower gears though it really must have affected the official mpg/CO2 figures. I also read somewhere (I think) that in cold weather the box holds onto gears longer to improve warm up???
I was told that by a Vauxhall engineer when i had an auto Cavalier,and it was the same on my old 75 1.8t and my diesel i ive got now, it must crucify the mpg during the warm up

[rossocorsa]

intersting if it's possible to fool the box into thinking it's warmer outside without affecting the engine management as well......thing is I've got a FBH for those cold moments I don't need it hanging onto low gears as well!!

[James.uk]

Big car + auto box is no way to go if you want economy... :o

IMO you are getting very good mpg out of your car.. :)

If you need seriously better mpg then I think you will have to get a smaller car.. :shrug:
...

[keir1163]

I will swap your consumption for mine any day!!

mind you now the box is fixed maybe it will go over 20mpg!

[rossocorsa]

Big car + auto box is no way to go if you want economy... :o

IMO you are getting very good mpg out of your car.. :)

If you need seriously better mpg then I think you will have to get a smaller car.. :shrug:
...
well actually I usually struggle to exceed 35mpg the fact that by coaxing the car to hold higher gears I managed to squeeze 43mpg from it set me thinking a bit it is definitely over keen to hold lower gears particularly in town (where it will be well under 30 mpg). Another oddity is that it is very erratic results in similar driving can vary quite a lot but I don't know why

[wutang]

I don't know if the diesel settings are the same as the petrol, but the things that affect the gear change on my 2.5 are :-

Engine temp,
Going up or downhill ( the box will try not to change gear if going uphill, and if braking downhill will change down.)
Position of the throtle

In the petrol in E mode I think that it changes up quite early, S makes a big difference,

Is there a difference between the 75 and ZT auto box set up? is the ZT suposed to be more sporty so holds onto the gears a bit longer?

Richard

[Dave***t]

Does the auto box in a diesel automatically adapt for the changes in torque if you fit a ron box?

If so, getting one might be a very good idea - a pleasing amount of extra power, with the side effect of allowing the box to change up earlier and therefore also save fuel.

Also if so, and assuming good examples are still available by the time I move on from my current car, I'd definitely be looking closely at a ronned auto diesel ZT next time around.

[rossocorsa]

Does the auto box in a diesel automatically adapt for the changes in torque if you fit a ron box?

If so, getting one might be a very good idea - a pleasing amount of extra power, with the side effect of allowing the box to change up earlier and therefore also save fuel.

Also if so, and assuming good examples are still available by the time I move on from my current car, I'd definitely be looking closely at a ronned auto diesel ZT next time around.

well that is one thing I'd like to know for certain! I am guessing that as the ron box introduces extra fuel that the ecu effectively doesn't know about that it may well allow the box to hold a higher gear for a given speed/accelerator position. My concern is could it save the extra £80 in insurance I have to pay if I fit one. Unless you are on a serious economy drive forget buying a burner though it just isn't the same as running on gas

[HarryM1BYT]

Mine is a manual, however....

The Synergy allows you to drive on much less press of the throttle, so I would imagine the effect on an auto would be for it to change up earlier - it has that effect on me as I work my way up through the box.

[Dragrad]

Thread moved to correct forum. Re-direct left in old.

[wuzerk]

RON does state that his modules suit the autos as they will change up earlier and down later. I see from your picture that the average speed was 43.6 mph. If that was the true average then you must have been in fifth gear for most of it! My auto, with Synergy 1 on 'medium' settings easily betters 50mpg on a decent run but general around town running brings it down rapidly. The car does weigh 1.6 tons!

[rossocorsa]

I see from your picture that the average speed was 43.6 mph. If that was the true average then you must have been in fifth gear for most of it!
only by trying hard! The box constantly wants to be down a gear but my original point was that by keeping in 5th I'd achieved at least 6 mpg above my norm but the box is very reluctant to stay in 5th even in very steady driving and trying to keep it in a high gear is harder work than driving a manual!!

[rossocorsa]

well I bit the bullet coughed up the insurance dough and ordered a synergy I'll report on what happens with economy and gearchanges once i've had a little time to test it out:D

[James.uk]

My auto wont change into top gear under 50 mph.. And if slowing, it changes down again at around 48 mph.

My car also holds onto gears longer when the engine is cold or under hard acceleration..

Touch the brakes going downhill and the engine assists the slow-down somehow.. :shrug:

A Ronbox will effect the gear changes as the cars ECU "talks" to the gearbox ECU. So any changes the Ron box makes to the cars ECU will in turn effect the signals sent to the gearbox ecu..

Driving in "snow" mode should reduce the amount of torque sent to the wheels.. ipso facto, it will change gear at lower revs but have poor acceleration..

Engaging "sports" mode will have the opposite effect..
...

[rossocorsa]

i tried snow mode out of interest but all it seems to do is start the car in second it doesn't seem to affect gear changes at any speed

[oldyellow]

i tried snow mode out of interest but all it seems to do is start the car in second it doesn't seem to affect gear changes at any speed
AFAIK that's all snow mode does, it just tries to reduce initial wheel-spin in ice/snow by moving away in second :(

[rossocorsa]

well I bit the bullet coughed up the insurance dough and ordered a synergy I'll report on what happens with economy and gearchanges once i've had a little time to test it out:D

fitted it tonight and set it on full torque and power :D haven't tested it in anger but in the dark i can't see any smoke ...except from the tyres. seriously waiting until the drive to work to see what has changed. It took me a lot longer to fit than the 15mins some folks seem to claim but I like to do a tidy job and safely cable tied everything out of harms way etc. and as usual the airfilter cover was a pain to get back it never seems to just click into place first attempt. I did take it round the block and the engine seems slightly noisier (?) throttle response is better not sure about the power increase yet need to get on the open road

[rossocorsa]

well not sure what to think changes are definitely better pick up is improved but performance has only gone from barely adequate to adequate it's not the stuff of forum legend. Can't say about economy the readings on the trip computer are very high which explains some folks claims on here but of course the synergy causes false readings so I'll have to wait until I can do a brim to brim. I didn't think my maf was completely done for as it didn't drive all that badly before but now I'm beginning to wonder.......

[HarryM1BYT]

I suppose because I am gentle right footed most of the time, I found the fuel computer to be not that much different in accuracy.

[rossocorsa]

I suppose because I am gentle right footed most of the time, I found the fuel computer to be not that much different in accuracy.
well if it is right the mpg improvement is dramatic!! Although I have to say that my trip used to be pesimistic by about 1 to 2 mpg but 65mpg cruising at 60ish seems a bit far fetched to me (I zeroed the display on the way home from work)

[James.uk]

If you put it in neutral going downhill the trip will read 900 + mpg :D ;)
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[rossocorsa]

If you put it in neutral going downhill the trip will read 900 + mpg :D ;)
...
and the auto box would end up jiggered!!

Actually today the trip settled down to a more realistic figure but i'm still going to brim to brim it to check and maybe get a correction factor for the trip computer

[HarryM1BYT]

well if it is right the mpg improvement is dramatic!! Although I have to say that my trip used to be pesimistic by about 1 to 2 mpg but 65mpg cruising at 60ish seems a bit far fetched to me (I zeroed the display on the way home from work)

I was also saw steady readings like that.

Mine seemed at first to be a quite dramatic increase, but after a few miles it seemed to settle down to more believable figures. I don't mean just the silly figures you see when you first reset the mpg reading, the sensible numbers seemed to last through the reset. When I first fitted it was probably when my figures would be terrible, that was when I was deliberatly really hammering the throttle, just to see what it could do.

See if yours settles likewise.

I now seem to be getting steady figures of around the 50mpg mark. It doesn't get used for short shop runs, nor daily work runs, just the longer pleasure runs and I usually tend to be an economic driver.

[rossocorsa]

done nearly 650 miles with one partial and one full fill up computer says 42.8 actual is 38.8mpg mixed driving and neither really pushing it or going for economy now to adjust that computer correction factor when i can find the how to!!.

[James.uk]

Just do the brim to brim.. It's the only accurate way to do it..

http://javascript.internet.com/math-related/miles-per-gallon2.html
...

[rossocorsa]

Just do the brim to brim.. It's the only accurate way to do it..

http://javascript.internet.com/math-related/miles-per-gallon2.html
...
yes I know but it is annpoying to have a trip computer showing total garbage so I adjusted it yesterday will brim it again later in the week and see how accurate it is now, just done a fast trip down to the classic car show and it shows 43 mpg will be interesting to see if it is right!! Didn't manage to speak with anyone on the club stand as the one person there was busy with someone and had back to the public burried in a laptop....