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Old 05-29-2013, 09:12 PM   #1 (permalink)
F8L
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Lowering Prius - raked or level?

I am going to lower my new Prius Plug In and I can choose between springs that keep the car level or ones that create a slight rake.

The TRD springs that come on special package Prius will lower the car approx. 1" all around.

H&R springs will create a more raked look and lower the car approx. 1.2" front and .75" in the rear.

My question is which drop is better aerodynamically speaking? The raked stance is good for downforce and may reduce the amount of air going under the car while accelerating aiding the evacuation of air out of the rear. The extra downforce scares me though. Wouldn't that increase rolling resistance?

The level stance is how Toyota set up the car and how the Performance Package comes but with the extra weight of the Plug In, I am worried that the rear may go lower which would create a very slight reverse rake or at least stay level.

The bottom of the Prius is pretty clean so I am not sure how much lowering will help or hurt.

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Old 05-29-2013, 10:50 PM   #2 (permalink)
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there is a science to it. Not sure though if it applies here.
Back in the 70-80s one of the mags eco-ed a muscle car....maybe the duster....found that dropping the front nose really helped. maybe 2mpg
But you have to remember, there was NO slant on the front of those cars like there are today. My bet is that the slight is already in the design.
with that said, I dropped the Q45 about 1 inch in the fron and saw a slight improvement in mpg. (your'll have to search my posts)

also, smashed the IMPUL body kit becuse of the 1" drop. (again search my thraeds)

Finally, If there is ANY deterioration in the ride quality, I wouldnt do it. I had put in An aftermarket spring kit....took them off after about 5k miles. And the Q45 has electronic suspesion! I just was not going to put up with a crappy ride for the looks.
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Old 05-29-2013, 10:54 PM   #3 (permalink)
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That is hard to say. If I had to guess, I'd say level is best.

And yes, more downforce = more drag.

And lowering the car doesn't necessarily mean lower drag. It might constrict the air flow under the car, and increase the drag.

Is that your Prius in your avatar? If so, you could lower drag a fair bit with smooth wheel covers.
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Old 05-30-2013, 12:40 PM   #4 (permalink)
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One inch on a Prius is like having 4 adults in the car so I wouldn't stress too much about it. I would go with the TRD springs as they tend to be the best spring rate balance daily driver/performance as Toyota can back their install with warranty and will most likely have the least impact on the life of the strut shock absorber after stock.
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Old 05-30-2013, 08:56 PM   #5 (permalink)
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Thanks!

The avatar picture is my old Prius. The new one has the OE Plug In wheels which are a little more aerodynamic looking.

The worry with the TRD springs is they are designed for the regular Prius which has a smaller battery and weighs about 100lbs less. This may create a little butt sag. Since I have never seen a Plug In with the TRDs in person I cannot say for certain but some of the pictures I've seen are worrisome. With the H&Rs I can get them for $200 installed through a friend.

This is more of a mental exercise than anything. The relatively clean body of the Prius makes the idea of lowering for better aero a little confusing because of what Neil stated. Lowering a car with a very clean underside may create drag.
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Old 05-31-2013, 10:37 PM   #6 (permalink)
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Quote:
Originally Posted by F8L View Post
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This is more of a mental exercise than anything. The relatively clean body of the Prius makes the idea of lowering for better aero a little confusing because of what Neil stated. Lowering a car with a very clean underside may create drag.
Still, SimuTech, which performed CFD analysis on the lowering springs and body kit (and 17" wheels!) with the PLUS package, claimed an improvement in drag. Looking at some of the streamlining images, as well as those of other cars, it appears to me that one overlooked benefit of lowering is decreased turbulence from the wheel wells.









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Old 05-31-2013, 11:37 PM   #7 (permalink)
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Wheel skirts would a much less drag from the wheel wells; not just a little.
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Old 06-01-2013, 02:35 PM   #8 (permalink)
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Quote:
Originally Posted by NeilBlanchard View Post
Wheel skirts would a much less drag from the wheel wells; not just a little.
Yeah, but wheel skirts are also more of a hassle to fab up yourself, engineer so they stay attached yet have easy access to the wheel, etc. Plus, putting the car closer to the ground improves the fineness ratio, as well as preventing some airflow under the car without the use of an airdam. I'm a little biased (I have my car lowered a couple of inches for these very reasons), but lowering does mitigate several issues in one fell swoop...and unlike a lot of what we do here, there's already wide public acceptance of the practice, to the point of manufacturer support (TRD, in this case). At least they're heading in the right direction, even if most people do it for reasons other than efficiency.

Besides, I'm not sure F8L will want to go put home-made wheel skirts on his new car
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Old 06-01-2013, 03:25 PM   #9 (permalink)
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Why not?????

Fourth: rear skirts and 30.4mpg on trip!
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Old 06-01-2013, 03:39 PM   #10 (permalink)
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http://www.carenthusiast.com/toyota/...0__005_530.jpg

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Third: Full underbelly pan
http://ecomodder.com/forum/showthrea...q45-11402.html

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http://ecomodder.com/forum/showthrea...tml#post247938
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