Replace F15 gearbox with F13 on X16xe

[cosmin_cosmin_1]

i want to change my f15cr gearbox with a f13wr 4.18 because in my opinion i should have a better fuel consumption on 4th and 5th gear.

the problem is that the main axle is not the same, i'll attach 2 photos

F15 (currently attached to the engine)
http://s1.postimage.org/17nc97a10/f15.jpg (http://postimage.org/image/17nc97a10/)

F13 (picture from the internet, but is the same as my spare f13)

http://s1.postimage.org/17nalnxj8/f13.jpg (http://postimage.org/image/17nalnxj8/)

as you can see, the end of the axle is not the same on both
Is it possible to replace the f15 with f13? will the clutch fit right? Anyone tried this?
I am also planning the change the heavy flywheel that x16xe comes with, with another one (flat type) from c16nz, also change the pressure plate but keep the original clutch disk

[phazer]

I'm running an F13 on my X16XE. I'm using the original SRi flywheel and clutch, I believe its the larger flat type.

[cosmin_cosmin_1]

sorry for asking this,but which engine code is "sri"?
do you know if your f13 gearbox have the main axle as in the second picture?

[tom reid]

I would leave the f15 in place, it'll give better fuel consumption than the f13.

[phazer]

The ratios aren't much different, that'd be my reason for keeping the F15.

OP: Engine code is C14SE or C16SE for the GSi. It'd need to be a late SRi though IIRC the early ones had the smaller flywheels from the single point injection 1.4

[cosmin_cosmin_1]

this is my f15cr at 3000rpm
http://s3.postimage.org/rovbozus/8a8071fcc37e21dad2ae2888e124d0c6.jpg (http://postimage.org/image/rovbozus/)

this should be the f13wr
http://s3.postimage.org/rp0ab1c4/f13wr.jpg (http://postimage.org/image/rp0ab1c4/)

little differences in acceleration on 1st,2nd,3rd gear, bigger difference in 4th and 5th which i hope it will lower the rpm when normal driving.

what do you think?

[phazer]

Ahh didn't spot the WR bit, mine is a CR, which has very similar ratios to the F15. Won't the WR make the car feel a bit flat? Especially as the X16 likes to rev.

[Stuart]

for the effort involved you will save next to shag all fuel imho.

[cosmin_cosmin_1]

at the same rpm, in 5th (if the values are right) i will travel around 10% faster with f13wr. in ideal environment (flat road, constant speed) , i guess this will give me a maximum of 10% fuel economy. its not much but i think its the best i can do regarding the gearbox.

any other advices pls? will help me reach a conclusion if its worth it or not
x16xe likes to rev, i agree,but it also likes to drain the pockets, mine does more than 10 liters/100km in the city

[Stuart]

at the same rpm, in 5th (if the values are right) i will travel around 10% faster with f13wr. in ideal environment (flat road, constant speed) , i guess this will give me a maximum of 10% fuel economy. its not much but i think its the best i can do regarding the gearbox.

any other advices pls? will help me reach a conclusion if its worth it or not
x16xe likes to rev, i agree,but it also likes to drain the pockets, mine does more than 10 liters/100km in the city

ignoring the fact that the 10% extra speed will require more power to overcome drag so you will use more fuel by default.
Also to do the correct city speeds you might be lower down the rev range which might be in an inefficient area of the engines behavior.

Try it by all means, but I dont think that you will get anywhere near a 10% saving

[cosmin_cosmin_1]

i've done some more calculations and: in 1st, 2nd and 3rd, the wheel speed is actually lower with f13wr than with f15cr, by:
6% in 1st
3% in 2nd
3% in 3rd

In theory i think it means it will accelerate faster and burn more fuel.

i've created an excel sheet, simulating the speed from 1000rpm to 5000rpm
http://www.clubtigra.ro/forum/viteze.xls

the f13wr is from a petrol engine (1.4 or 1.6 L), not diesel.