how do u tell e12/e28?

 Late '87 aerodecks got 14" wheels, cruise, but no air con. '88 models got horrible upholstery and most were autos. I had a manual, and it was very good; rust was the enemy in the end. In the USA they got a 'fastback' model too, with the same front (pop-up headlights etc) as the Aerodeck.

 Under the bonnet; the small thing with the yellow dot on it to the left of the airbox is the cold idle auxiliary air valve. Over time this wears and needs adjusting, but even the Honda manual tells you not to do this (rarely incorrect, but on this occasion...). This little blighter is often the kiss of death for an auto box; if it goes out of adjustment, then on cold starts the engine hunts between 2000rpm and 500rpm or just idles too high (1500rpm). On the manual box it is just irritating, but with the auto it works the box in a bad way- sometimes damaged just by selecting 'drive'.  

Sorry about the Aerodeckness, wrong place and all that...I think I've got it out of my system now....

cheers

Perhaps we ought to rename this section the Aerodeck forum.....

Still, when do we get to see the photos of your Mazda with its bra on, Ben?

I was gutted when I wrecked my first aerodeck on diesel; it was a manual EXi in silver. The second one I had was never as good as the first... and eventually began to rot. A chum ran it for another 70000 miles and eventually someone ran into him and that was the end of it. Very few left now; hardly any in good shape with manual gearboxes. Preferred the earlier trim (stripy); just a few with this trim and cruise...

cheers

Well - my car is defo in need of a tune up, something which I havn't had the time to get round to due to work pressures. I get about 25 mpg tops - even though the econometer suggests 30 or so, the pumps tell me its about 25.

I have never driven another BMW with cruise, and so could not compare it to mine - in any case I hardly ever use my CC due to the fact that the roads in this country are too busy most of the time. I tend to use it when my foot gets tired!

As far as the down change goes, this happens when the CC stalk is pushed forward. It accels for about 5 secs in top, and then seems to change down in to 3rd and keep on. However the 10 or so times I have used the accel function have been at about 60 mph - so that could explain this  - at 80 i suspect it wouldnt change down.

I used to own a Honda Accord with a vacuum operated CC system, with buttons on the sterring wheel - although mechanically different, in practice it did the same thing as the 6 does, and was also never as economical when running on cruise. Incedently the Accord did not have an econometer at all, so I went by the fuel gauge on a common journey I used to do!

This was an '87 Saloon 2.0 EXi with a 12 valve engine - and it never did more than 30 mpg on the motorway either. Although on the combined cycle I did fare much better than the 6, which does about 12-15mpg in urban conditions as far as my experience goes. 

Actually, now that I remember the Honda, the vacuum system moved the accelerator pedal, which you could feel and see, whereas the BMW system does not have that feature.

I just wonder how the manual 6's fare on motorway economy compared to the autos.

-eh? your (and my) model 6er have the tallest gearing going, for economy. Mine does 30mpg on a run which is pretty good for this size engine. On the motorway it accellerates in top gear quite adequately without kicking down into third; once above an indicated 70mph it takes more than 3/4 throttle to get it to kick down. I don't have cruise on mine, but on other vehicles I have owned it was very rare for the cruise control to apply more than half throttle under accelleration. I can't help but think there might be something amiss if yours tends to kick down when you don't want it to when driving at speed.

cheers

phb10186 wrote: come to think of it, that makes perfect sense so as far as the consumption dial behaviour is concerned; i.e touch the gas and the econometer goes east. Another point in this department - if BMW designed what was a pretty clever piece of electronics for the early 80's, they also designed a fairly poor cruise control system, since the economy loss is huge when on cruise, as it seems to be pretty heavy on the gas to maintain speed. It is a shame that the cruise does not have a setting to not have to change to 3rd to speed up, rather instead gently use 4th to gather speed, and thus save some fuel that way.

in 'E' you should be able to use about 1/3rd throttle above 62mph without provoking a downshift from 4th. If your does anything different I suspect the most likely cause is a worn throttle potentiometer- this is used as one of the signals for the gearbox computer and is a commonly faulty part on older cars.

cheers

come to think of it, that makes perfect sense so as far as the consumption dial behaviour is concerned; i.e touch the gas and the econometer goes east.

Another point in this department - if BMW designed what was a pretty clever piece of electronics for the early 80's, they also designed a fairly poor cruise control system, since the economy loss is huge when on cruise, as it seems to be pretty heavy on the gas to maintain speed. It is a shame that the cruise does not have a setting to not have to change to 3rd to speed up, rather instead gently use 4th to gather speed, and thus save some fuel that way.

Thanks Ivan, v interesting.

Also interesting re. motronic lumps with 'banana' manifolds, never seen one myself, live and learn etc....

motronic cars are meant to be more economic because of the improved over-run fuel cut-off and a lower idling speed. E28 base E24s are lighter in weight and many are taller geared too. Both these help fuel economy considerably. However the biggest change comes with the 4-speed auto vs the earlier 3 speed (although not strictly an E28 thing). E12 base cars with the auto box struggle to do better than 20mpg round town and 25mpg everywhere else...

cheers