Trans Am build thread

[sjgrimsley]

I decided I should start a new thread for any further mods I do on my car instead of posting to my intro thread.
A little background, I typically get 18.5~19 mpg. 20.5-21 mpg if I really, really tried. After sealing up gaps at the front of the car, and extending the front air dam, it's up to 21.7 and 21.5 without too much effort. My next mod was side skirts.

Anyway, I have a couple of pictures to post of the rain gutter side skirts I finished last night.







They started out white, but a can and a half of black plasti-dip fixed that. I also made up an inner pair of skirts to go up to the inside edges of the tires, but I don't have any way to mount those yet.

All told, I have less than $25 in them. When I installed them last night I had about 220 miles on the current tank. After today's commute to work and back there are 265 miles on the tank. Probably will see no difference until I have a full tank with these on here.

[Joggernot]

How did you seal the gaps up front? Foam?

Joggernot

[KrautBurner]

have you thought about going with a T56 (Manual 6 speed)?
it's got a double overdrive

would probably make a difference
but with those 3.23 rear gears, you may need to go 75mph to get peak mpg



my 4,000+lb GTO with a 400HP 6.0L (when stock)
was getting 30-32mpg on the highway (if I could keep the speed up about 70-75mph)
and that's with 3.46 gears

now, she gets about 23-24mpg highway

[KrautBurner]

btw,

your front tires are on backwords?
are those Mich Pilot Sport A/S?

[sjgrimsley]

Originally Posted by Joggernot

How did you seal the gaps up front? Foam?

Joggernot

Yes I used a strip from front to back between the skirt and rocker panel.

Originally Posted by KrautBurner

have you thought about going with a T56 (Manual 6 speed)?
it's got a double overdrive

would probably make a difference
but with those 3.23 rear gears, you may need to go 75mph to get peak mpg



my 4,000+lb GTO with a 400HP 6.0L (when stock)
was getting 30-32mpg on the highway (if I could keep the speed up about 70-75mph)
and that's with 3.46 gears

now, she gets about 23-24mpg highway

I have considered a T56 but those cost their weight in gold around here, and I have been planning a 6L80 swap with 2.73 or numerically lower ratio rear for a while now anyway.

btw,

your front tires are on backwords?
are those Mich Pilot Sport A/S?

Yes and yes. I swapped them a while back to diagnose a problem pulling to the right and have yet to swap them back.

[oil pan 4]

If the l480 and l680 use the same first gear then using a 2.73 rear is going to be slugish.

What kind of wheels are those?
And are they lighter than the factory wheels?
The factory iroc alloy wheels weigh 22lb.

[sjgrimsley]

The 4L60 has a 3.06:1 1st gear and the 6L80 has a 4.03:1 1st gear. For a reference, the C6 08+ Corvettes with the 6L80 come with a standard 2.56:1 ratio or an optional 2.73:1 'performance' ratio.

With the torque this 406 already makes, I am tempted to try the 2.56:1 rear with the current 4L60 trans.

And these are C5 Z06 replicas 17"x8.5" front, 18"x9.5" rear. I have them to clear the future brake upgrade. The factory wheels won't clear the front rotors I'm looking at getting.

[oil pan 4]

Do you think front 17 inch vette wheels will fit all 4 corners of a 3rd gen?

[sjgrimsley]

They will for sure. But this a dual purpose car of sorts haha

Call me crazy but this is sort of my quest to build the poor man's Z06 which is a 427 (7.0L) rated 505 hp and returns 28 mpg at 75 mph. If it can do it, I feel I should be able to get close. It has 18" front and 19" rear and they are wider.
I'm sure it's considerably less frontal area than my car, and I know it sits lower, but I don't think it's THAT much of a difference. But I could be wrong. Lol

[oil pan 4]

The thing is the last body style of hyundai sonata the v6 has very simular weight, frontal square footage and Cd as a 3rd gen. The hyunda gets up to 8mpg better than the old V8 80s car.
So its possible for car of that mass and aero profile to get mpgs in the high 20s. The difference is all engine, engine management and gearing.