Making an old Volvo fuel efficient

[Joris]

Made a start on the undertray by bolting some aluminium sheet to the rear. Will try to close off the sides, and above the leafsprings with some rubber sheets.



Should I put on some vertical fins, or would those only be there for looks?

[renault_megane_dci]

The way I see it, there is a big step between footwell at the level of your diff and the aluminium sheet you added.

IIRC the smoother the transition, the least the drag.

But to steep an angle will add lift at the expense of drag.

[UltArc]

Vertical fins will help. Man, that looks good.

[Joris]

I got 36 MPG this week. I know it can be better because not even half of it was highway driving. Next week the turbo camshaft arrives, so interesting to see what that will do.

[Joris]

Got some things done. Installed the turbo camshaft, what a joy to drive! Vacuum at idle is much lower, pulls better down low and idles better. I think (hope) the cam will save me some fuel.

Mocked up a cardboard partial kammback, will need your help on this in another topic.


Started thinking about smooth wheelcovers.


And finished my front undertray today.

[renault_megane_dci]

Wheel cover wise, I wonder if it won't be easier to start from steel wheels as they're designed for it, having the little lip on the side (and being magnetic ...)

Also, a good opportunity to go for narrower / taller tires if you can find second hand tires ...

[Joris]

Yes, I am looking for another set of wheels. But at the same time, I will try to make some covers for these wheels. Better then nothing

Calculations showed a 300 rpm drop with taller (195-65-15) tires at 60 mph. Sure that doens't go unnoticed

[renault_megane_dci]

What's the wheel pattern ?

I seem to recall eco tires go up to 16 inches these days.
An other 300 rpm wouldn't scare that big 2,3 liters engine of yours ...

[Joris]

Originally Posted by renault_megane_dci

What's the wheel pattern ?

I seem to recall eco tires go up to 16 inches these days.
An other 300 rpm wouldn't scare that big 2,3 liters engine of yours ...

Wheel pattern is 4x100, the same as most small cars have. Easy to find.

When driving, I can feel that I am 'overreving' the engine, and want to shift to 6'th gear, but it is not there.

[renault_megane_dci]

Volkswagen and Renault come to mind but still not the one and only size.
(Peugeot and Toyota are different for sure)

300 rpm drop seems like a lot, it's actually the ball-park between my 5th and 6th !

Is there a diesel variant for your gearbox / diff combination ?

I did a gearbox swap in my Mk1 Golf GTi back in the day using a diesel gearbox.
It didn't last long so I ended swapping just the diesel crownwheel and pinion in the GTI diff setup that has some inbuilt springs.
It made a big overdrive in 5th like 180 kph @ 4500 rpm.