putting a small suspension lift on back of volvo s40 - Fuel Economy, Hypermiling, EcoModding News and Forum

chefdave · 03-03-2015, 01:19 PM

Hi
after reading an article on here on corvette aerodyamics and having the rear of my volvo lower than the front. Would it help aerodyamics to raise the rear about an inch. S40's are also known for soft rear springs if i put any weight in boot the front end starts to feel floaty and vague. Think its to do with factory fitted engine under tray as the air hitting it is lifting the front end. No weight in back and s40 feels glued to the road. Other option is to fit a small air dam as s40 is very close to the ground 12" or less not sure about airdam effectiveness. A 3rd option could be replace rear shocks and springs from a v40 estate of same age and see if this helps. Shocks and springs will come off as a unit provide nuts are not rust welded on should not be a difficult or long job. Views or opinions are most welcome.
thanks
dave

aerohead · 03-03-2015, 07:31 PM

carmakers have known for many decades that changes in inclination can effect drag.
There is a risk that Volvo has already optimized the inclination angle on your car during its development.
A few studies were published and no two cars behaved the same.I don't have all that with me,sorry.
The Ford Probe-IV would drop its nose about 3-inches,then raise its tail a smidgeon,increasing the attack for the top of the car,without increasing its overall height (frontal area).
From a safety standpoint,it might be better to lower the nose than to raise the rear.Some cars were given active suspension so that the car would maintain a constant rake regardless of load.It was a safety issue.Progressive-rate springs were developed in part to mitigate these effects.
Renault's VESTA Plus concept car enjoyed a 0.004 drag reduction from a 0.75-degree nose drop.
Without a wind tunnel its a tough thing to figure out.

Joris · 03-04-2015, 08:24 AM

You could search for 'Mad' springs. They do trailer springs for Volvo s40/v40 which stiffen the rear and lift about an inch. Not sure if they are available overseas.

Edit: you are in the uk, so no problem
http://www.mad-tooling.com/en/suspen...-coil_springs/

chefdave · 03-04-2015, 11:55 AM

Hi thanks for feed back. Volvo wheel arch to wheel is actually smaller/closer than front by 3/4". So will be looking into towing springs Josha.

Sven7 · 03-04-2015, 05:16 PM

Hot Rod Magazine (I think) did some wind tunnel testing on a second gen Camaro land speed racer and found that lowering the car in any way-front, back or all around- was beneficial (this may have been from Hucho, but both are useful sources). Your sloping roofline probably acts like a very mild kammback right now, recovering pressure built up by the front of the car, and as long as you have an air dam to deal with air aimed at the underbody, you should be fine.

chefdave · 03-14-2015, 03:23 PM

Hi
got some rubber spring insterts used as a towing aid for coil springs. Car rides so much better steering has more feel and bite. According to trip computer on my 56 mile daily commute i have picked up 0.2 mpg average. Now saving up for proper springs as investment seems worth while.

aerohead · 03-14-2015, 05:37 PM

Quote:

Originally Posted by Sven7

Hot Rod Magazine (I think) did some wind tunnel testing on a second gen Camaro land speed racer and found that lowering the car in any way-front, back or all around- was beneficial (this may have been from Hucho, but both are useful sources). Your sloping roofline probably acts like a very mild kammback right now, recovering pressure built up by the front of the car, and as long as you have an air dam to deal with air aimed at the underbody, you should be fine.

I ran across a note from an article a neighbor who owned a Porsche 914 shared.
The 914 was tested at different ground clearances:
*zero G.C. = Cd 0.30
*140 mm G.C. = Cd 0.34
*165 mm G.C. = Cd 0.357
*180 mm G.C. = Cd 0.367