An "aero" idea

[AndrzejM]

I just have this thought of adjusting the aero shape of the car by changing front and rear suspension height. If i could for example make the difference of 4cm (~1,6") or maybe even a bit more from the stock height of the car I could have much better angle of the roof. Of course it should be combined with an air dam to cut the air that would want to squize between the car and the ground.

Don't know if that would make a big difference but for example by changing the height of the front suspension by 4.2cm or lowering rear by that. Or changing that proportionally +2.1 front and -2.1 rear with a wheelbase of 240cm I could change roof angle by 1 degree. That's maybe not too much but as i said that's just an idea...

What do you think about that guys?

[Sven7]

I'll repeat what I read earlier here. I think it was in reference to the Hot Rod Magazine LSR 2nd gen Camaro. Lower, lower, lower. The lower you go, the better off you'll be. There's some debate on what is "too low" (about five inches, the ground clearance on Ren), but from what I gather, you're unlikely to see any gains by increasing ride height. Even SUV's like the Touareg with air suspension lower it bodily on the freeway. I think the Ram does this too now.



PS- food for thought. Companies in Europe probably make air kits for your Polo, and also probably for the E36 in your profile photo (although that 318 may be a mix-n-max with an E30 kit). You could conceivably convert to air suspension for fuel economy, and though the gains could be significant (10% maybe?), you may not make back the money spent.

[2000mc]

I always thought you were supposed to go the other way if anything, lower in the front than rear. most cars roof and trunk I think would benefit more from lowering the front only than yours. I would agree that lowering the rear on yours seems like it would produce a positive affect on the roof, however I think the penalty on the underside would outweigh the gains on the top side. If I was going to lower it, I would drop both ends evenly. After I added a modest air dam (paver edging, think it's like 1.5") I hear it rub a little often, enough I quit thinking about lowering

[AndrzejM]

With roads like are here in poland i can;t think of lowering the car... It would be better actually to make it a bit higher... Especially in winter.
I need to measure the Polo's roof angle and draw it then i'll see how the changes to the suspension would change the roof angle.

The idea came to me when I was riding Polo with very heavy load and three bicycles hanging on the tow bar. The rear was so low that i was scraping the asphalt with rear mud guards (Yes I know I'll delete these ). Anyway I got amazing FE then of 4.3l/100km And I was wondering why... Then i saw on the picture that the roof angle was much closer to the aero template than usual...

[spacemanspif]

I was looking at my new wagon just yesterday and thought how silly it looks riding higher in the rear. My plan is to level it and maybe drop the whole car an inch, nothing crazy, but most importantly just get the rear down level with the rest of the car. I agree that a car riding lower in the rear wouldn't make sense but I'd like to throw "level" into the mix as it seems most of today's cars ride higher in the rear.

[freebeard]

I vote noisy data.

When the car rocks front to back on the wheels the roofline moves in an arc, but the entire underside is going from negative to positive angle of attack [and back]. I suspect that is much more significant.

[redneck]

Originally Posted by spacemanspif

I was looking at my new wagon just yesterday and thought how silly it looks riding higher in the rear. My plan is to level it and maybe drop the whole car an inch, nothing crazy, but most importantly just get the rear down level with the rest of the car. I agree that a car riding lower in the rear wouldn't make sense but I'd like to throw "level" into the mix as it seems most of today's cars ride higher in the rear.

I"m sure it sits higher to allow for carrying a load.

However, I also wonder when the vehicle is at highway speeds if the rear of the car is pushed down by the airflow over the top and the front up from the air that is jammed into the engine compartment lifting the front. In effect leveling the vehicle. You could have someone else drive your car while you drove along side in another vehicle and observe what happens before you go changing anything.


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[Grant-53]

Most passenger cars generate lift rather than down force. The lowest point should probably be just behind the engine and the pan rises at an angle up to 8-10 degrees. For purely low drag, the front air dam may match the lowest point. If you need down force, go lower. Ground clearance depends on wheelbase and road conditions. All highway driving and no snow allows a 4-5 inch height, otherwise 9 inches is common.

[aerohead]

It's likely that the car was already optimized with respect to body inclination.Something very easy and inexpensive during product development.
And past messengers have reported that small changes in a bodies 'rake' can significantly affect drag.
If SAE papers were available for the Ford Probe-IV and V,they would be valuable,as both cars had active suspension.
The IV lowered its nose,deployed an active airdam,while raising its tail to achieve the lowest Cd.
You'd need careful measurements to 'know' what you'd done.
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The Spirit of Ecomodder.com is a skosh low in the nose (from undersized tires) and a skosh high in the tail (from oversized tires).
I have no idea what the impact to the drag resulted from the changes.It was beyond the scope off my project.