seeking aero advice

[Philip1]

I have a 2003 Saturn LW200 2.2 4-speed auto. I am trying to squeeze every mpg I can out of this car.

Here's what I have done so far:
warm air intake (I may convert it to a hot air soon)
2.25in exhaust from engine back
lowered suspension
((I used to race this car so these were done for power not economy))
upper grille blocked (I'm planning a lower grille block soon)
small lip spoiler (trip strip) on tailgate
tire pressures at 44 psi (max rating on sidewall)

I guess my questions are where to go next and have I done any aero damage with additions (such as the lip spoiler).


I am looking at a belly pan. The window screen thing has my complete attention. I am also looking at fitting a hard tray between the bumper and radiator support so the air sent to the radiator goes there and not anywhere else.
I am hoping to see 40+ mpg

[SL8Brick]

Re: the rear lip spoiler...

I have one of these on my Volvo wagon...http://www.jcwhitney.com/autoparts/P...001926/c-10101

I have the 1" high version. They're very flexible and can be easily bent to contour to a rounded rear roof line. They can also be profesionally painted to match. Personally, I like the practical benefits and anti-lift characteristics of the rear lip when applied to a two-box...but I'm sure there are others here who will disagree with that.

[Philip1]

yep thats the one

[SL8Brick]

Originally Posted by philip1

yep thats the one

Any close-up photos of yours?

[Philip1]

I'll have to get some when it's light out

this is the best I have so far

[kamesama980]

2.25" is way bigger exhaust than you want. 2.25" is perfect for my toyota 3l revving engine. Your domestic 2.4 will probably do better with a 2" (quality exhaust!!) or so unless you get the revs up. reason is you'll lose exhaust velocity and low-down torque meaning you'll have to use more gas. basically, exhaust size determines peak torque point and powerband distribution. 2.5 collector to axle to a 2.25 axle-back on my 3l puts the power peak OVER 6k rpm. 2" with cat and both mufflers put it about 4.5-5k. You want the peak efficiency to be where you spend most of your revving time: in an economy mindset, at or around acceleration and highway rpms.

Course then again maybe the ecotechs are wierd sobs and do best with a big big exhaust.

I suppose I should also qualify that it depends on how good the exhaust system is. if you use a free flowing cat and muffler with mandrel bent pipe, you'll want 2" or less. if you get regular press-bent with wrinkles, crimps, and normal mufflers, 2.25 might be necessary to make up for the inefficiency of the system itself.

[Philip1]

I used to race this car incase the photo was not a total give away. this exhaust size was determined by several factors.
1. VE at 5800rpm needed flow conducive to 2.25in pipe
2. 16 valve head flows more than 8 valve
3 10:1 compression
4. Dyno results indicated a 5-7hp gain across the board

this means nothing to FE unfortunately just a loud drone

BTW: I can't remove the roof rack due to the factory installed curtain airbags.

[Dynamically Aero]

Here's another source for the spoilers.

[kamesama980]

Like I said, I don't have experience with the ecotechs.

well if you're looking for 5800 rpm power, go for it. I've seen people do too big exhaust on cars and lose (usable) power and mileage because they shifted the exhaust velocity peak above redline. Drive an Infiniti G20 with open downpipe vs full ehxuast...revs great and huge power on the highway and crazy high rpms but you can't drive with it under 3k rpm. put the exhaust back on and you can chirp the tires at 2k rpm.

[Philip1]

if I could I would go back to a stock cat back at least