tomshark

i often complained how bad the mpg on this 85 euro auto is. around 13-16 mpg.
after fixing the cruise and finally sitting and watching the rpm against cruising speeds 3,000 rpm at 75-80 seems rather steep. may i assume the 4 speed auto is not a overdrive ?
is this normal ?
is there a better option manual maybe or is the gearing just as high in 5th gear?
this car is a poster child for a gear vendors overdrive unit but it just can not work .

safulop

4-speed auto is 1:1, no overdrive. Final drive increase slightly for S4 model I think, so my RPM at 80 mph is around 2700. This gets me 20 mpg nonetheless, so less than 18 mpg highway is indicative of rich running.

-Sean

the flyin' scotsman

the 84-86 euro has an optional final drive ratio of 2.54

Sean.....your 88 has a 2.20 diff...... lower revs for better mpg.

James Bailey

plus it has a looser torque convertor which allows the engine to rev more quickly as you start to pull away from a stop. The Euro 16 valve likes RPM.....at the expense of MPG

the flyin' scotsman

more info:

tomshark

thanks the info confirms what what i am seeing. i was under the impression it was a 4 speed overdrive .
the car is running very very well and a blast to drive .
i just have not seen those kind of rpms at hwy speed since muscle cars with 3.55 and up rear ratios
i really love driving and working on it but i hate righting a check to exxon /mobile everytime i take it out.

James Bailey

If she is going to run 150 mph it NEEDS to be spinning 3,000 at 75 MPH

RKD in OKC

Almost every Porsche I've owned sees almost right at 3000 rpm at 80mph.

tilac999

It's because the ROW/Euros have a 2.75 rear gear insted of the 2.20 USA. If you had a 5-spd auto or I had a 6-spd manual we'd have OD instead of 1:1 in top gear. Highway MPG would shoot way up.

DANdeMAN

Well, I'm doing 100kph(60mph) @ +/-1800rpm in my 84 AT in D... But I think my speedo is off by 5kph.
According to my calculations, it would give me 80mph @ +/-2400rpm. I will have to confirm that in real life...
As a side note, I did 210kph(130mph) @ 5000rpm in 3rd a few times - This I will not confirm - maybe.

the flyin' scotsman

what diff ratio do you have Dan?

From the info I posted above it appears the 85 Euro could have 2.20 or 2.36 or 2.54

tomshark

at 60 mph i am sitting at about 2400-2500. again it seems very high
and by the engine whine i would say the tach is pretty close.

the flyin' scotsman

the tranny/diff info is stamped on the lower rear diff casing. if you get under the car from the rear the stamping is easy to find then we can determine what ratios you have from there.

do you shift the gbox manually? does it select all gears? whats the maintenance on the tranny?

DANdeMAN

I was about to ask that question....
I guess I have the 2.20 and I am not to inclined in craling under there at the moment. Can it be seen with a mirror on a stik.

Jim Devine

The speedo & tach may or may not be accurate, but
you can do the math using the tire diameter,
gearing etc. & compare it.

http://www.jekylhyderacing.com/HeightofTires.htm