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Old 03-11-2014, 08:03 PM   #1 (permalink)
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Trans Am build thread

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.

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Fully sequential port fuel injection
406 sbc 350hp @4800 425lb-ft @3600
4L60e trans .70 OD, 3.23:1 rear, 26" dia. tire, 1,600rpm @55, 2,050rpm @70
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Old 03-12-2014, 08:25 AM   #2 (permalink)
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How did you seal the gaps up front? Foam?

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Old 03-12-2014, 01:38 PM   #3 (permalink)
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Cavalier of D00M - '05 Pontiac GTO LS2 T56
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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
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2005 GTO 6.0 V8 (600hp)

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Last edited by KrautBurner; 03-12-2014 at 01:46 PM..
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Old 03-12-2014, 01:47 PM   #4 (permalink)
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btw,

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

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2005 GTO 6.0 V8 (600hp)

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1994 F-350 7.3 TurboDiesel (Rollin' Coal)
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Old 03-12-2014, 07:22 PM   #5 (permalink)
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Quote:
Originally Posted by Joggernot View Post
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.

Quote:
Originally Posted by KrautBurner View Post
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.

Quote:
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.
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Fully sequential port fuel injection
406 sbc 350hp @4800 425lb-ft @3600
4L60e trans .70 OD, 3.23:1 rear, 26" dia. tire, 1,600rpm @55, 2,050rpm @70
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Old 03-13-2014, 04:09 AM   #6 (permalink)
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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.
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1984 chevy suburban, custom made 6.5L diesel turbocharged with a Garrett T76 and Holset HE351VE, 22:1 compression 13psi of intercooled boost.
1989 firebird mostly stock. Aside from the 6-speed manual trans, corvette gen 5 front brakes, 1LE drive shaft, 4th Gen disc brake fbody rear end.
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Old 03-13-2014, 01:55 PM   #7 (permalink)
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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.
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Fully sequential port fuel injection
406 sbc 350hp @4800 425lb-ft @3600
4L60e trans .70 OD, 3.23:1 rear, 26" dia. tire, 1,600rpm @55, 2,050rpm @70
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Old 03-13-2014, 06:57 PM   #8 (permalink)
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Do you think front 17 inch vette wheels will fit all 4 corners of a 3rd gen?
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1984 chevy suburban, custom made 6.5L diesel turbocharged with a Garrett T76 and Holset HE351VE, 22:1 compression 13psi of intercooled boost.
1989 firebird mostly stock. Aside from the 6-speed manual trans, corvette gen 5 front brakes, 1LE drive shaft, 4th Gen disc brake fbody rear end.
2011 leaf SL, white, portable 240v CHAdeMO, trailer hitch, new batt as of 2014.
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Old 03-14-2014, 12:28 AM   #9 (permalink)
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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
__________________

Fully sequential port fuel injection
406 sbc 350hp @4800 425lb-ft @3600
4L60e trans .70 OD, 3.23:1 rear, 26" dia. tire, 1,600rpm @55, 2,050rpm @70
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Old 03-14-2014, 04:19 AM   #10 (permalink)
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Riot - '03 Kia Rio POS
Team Hyundai
90 day: 30.21 mpg (US)

Bug - '01 VW Beetle GLSturbo
90 day: 26.43 mpg (US)

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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.

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1984 chevy suburban, custom made 6.5L diesel turbocharged with a Garrett T76 and Holset HE351VE, 22:1 compression 13psi of intercooled boost.
1989 firebird mostly stock. Aside from the 6-speed manual trans, corvette gen 5 front brakes, 1LE drive shaft, 4th Gen disc brake fbody rear end.
2011 leaf SL, white, portable 240v CHAdeMO, trailer hitch, new batt as of 2014.
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