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Torroni
08-11-06, 07:27 PM
How can I make my standard 1.6 GTE Nova more economical on motorway journeys?

Engine runs at about 4000rpm in 5th gear doing 70mph. Just feels like an extra gear or larger 5th gear is needed to bring the revs down for motorway cruising?

Any ideas? Thanks! :)
Stoo
08-11-06, 07:32 PM
Final drive???
craig0120
08-11-06, 07:49 PM
fit a 1.0?
change final drive tho
Torroni
08-11-06, 07:50 PM
Can explain final drive Stu? I'm not familiar with how the whole thing works.
Welsh Dan
08-11-06, 08:10 PM
Basically the gear ratios are worked out by how many teeth on the 'gear you're in' compared to the final drive. The bigger the final drive for a given gear the slower the wheels turn for a given engine speed, but with more torque. The smaller the final drive for a given gear+engine speed, the faster the wheels turn with less torque.
Stoo
08-11-06, 08:14 PM
Final drive errrm

if you wanna change it, Its a bit technical, not easy, so dont tackle it if your not competent.

basically theres a set of two cogs/gears in the gearbox (crownwheel on the diff, and the pinion/idler gear) this is the final drive, if you lower the final drive ratio you will accelerate quicker but lose top end speed, however if you higher it, you will lose on acceleration but gain speed!!

Im not sure which box you would have to get the final drive from tho to achieve ur goals!
Torroni
08-11-06, 08:14 PM
So what what ratio would i be looking for to obtain the desired effect in 5th gear? i.e. Lower revs at motorway speed. Where can I get hold of a new gear?
Welsh Dan
08-11-06, 08:18 PM
Which gearbox and FD do you have? If you have an F13CR you could pull the 5th gear from a normal one (WR), and keep your acceleration in the lower gears, but gain a bit more economy in 5th.
Torroni
08-11-06, 08:24 PM
Yes its the F13CR. How much difference will the (WR) make? I guess I need to look on ebay to get hold of the part?
Welsh Dan
08-11-06, 08:30 PM
http://www.xen0phobiak.f2s.com/novaload/gear_ratios.jpg

Image borrowed from stuart, its in german but you'll get the meaning. Look on ebay or F/S here or find any 5 speed F10.

I've got an F13CR I intend to fit at some point, its already got a 4.18 final drive, but I'll probably fit the 5th gear from my f10 for the same reason you're talking about.
mowgli
08-11-06, 10:12 PM
if the engine is in good condition, then at a steady 75mph, it should get close to 45 mpg, gm actually designed lean bits into the ecu so at 56 & 75 it runs really economically, they have been fiddling fuel mileage official figures for years
Torroni
09-11-06, 10:12 AM
if the engine is in good condition, then at a steady 75mph, it should get close to 45 mpg, gm actually designed lean bits into the ecu so at 56 & 75 it runs really economically, they have been fiddling fuel mileage official figures for years


I've never had anywhere near this sort of fuel economy. A full tank of petrol usually lasts around 200-225 miles maximum, which is a combination of motorway and 'around town' driving. It just feels like there is no need to run at 4000rpm if the engine can handle a slightly bigger 5th gear.

Will there be a problem with the way the ECU is set-up if i change the final drive?
Welsh Dan
09-11-06, 06:17 PM
Changing the gearbox wont affect the ECU.
Adam
09-11-06, 07:35 PM
If you change the final drive it will effect all gears tho, whereas fitting a WR 5th gear will allow low engine rpm on motorway, but still keep the other gears the same.

I'd change 5th.
Chris Astley
09-11-06, 08:20 PM
The last gte i had did between 240-270 to a tank full, maybe get your car setup on a rolling road and serviced if it hasnt been done recently!

Chris
ade
10-11-06, 12:03 AM
isnt 4000revs a bit high for 70mph? I know when I drove in my 1.4 Nova 70 mph was about 3200revs (i think). Its the same in my seat and the volvo s40 i drive (2ltr).
Chris Astley
10-11-06, 08:50 AM
What size tyres you using? with a f13cr box at 4000rpm using 195/50R15 for example you would be doing 78mph.

If you fitted the WR 5th gear you would be doing 97mph which i dont think the engine would pull it very well if you have standard horsepower.

Chris
Torroni
10-11-06, 12:45 PM
What size tyres you using? with a f13cr box at 4000rpm using 195/50R15 for example you would be doing 78mph.

If you fitted the WR 5th gear you would be doing 97mph which i dont think the engine would pull it very well if you have standard horsepower.

Chris


Hi Chris...

Tyres are 15" and speedo is accurate as I've checked this with my in-car GPS? How did you calculate the numbers above or does my engine need serious re-tuning?? :)
Stuart
11-11-06, 08:45 AM
erm as a quick one here ( i cba to read the whole thread) but if you want to drop the engine speed for a given road speed then either fit bigger wheels, OR fit a lower number FD like a 3.74 etc.

but im fairly sure the FD in the F13 in gte/gsi's was a 3.74 anyway