New Guy w/ an 84 Mustang GT - Fuel Economy, Hypermiling, EcoModding News and Forum

1trickpony · 10-30-2012, 02:23 PM

Hi all, Jeff here. From Northern Iowa with a 1984 Mustang GT. I am currently swapping out the tired carburated 5.0 with an '87 EFI 5.0. It has a T-5 and 3.08's
So far my best was 18mpg with the carbed motor. I am hoping for low 20's right out of the box with EFI. I have added a late 80's ranger front air dam in hopes to help with MPG.
Right now it has solid rims on it with 14" tires. It wont be running those forever but they work for now.
Thats all I can think of for now more to come..

UltArc · 10-30-2012, 03:14 PM

Welcome! It seems like the Mustang community is really growing here.

What is your commute like? Any other goals?

1trickpony · 10-30-2012, 04:24 PM

I don't daily drive this car but do go on long trips with it to bigger shows and what not. My goal is to drive to Denver this April for my sisters wedding and get 25+. I will be hauling a small motorcycle trailer to carry all the 1 year olds stuff. Long term goal. Do power tour and get 30 mpg average over the whole trip

1trickpony · 10-30-2012, 06:33 PM

Putting this in here so I can remember later on:
1984 EPA rating:City-13 Comb-15 HWY-20
Now the new motor is a 1987 5.0 H.O with a 1988 harness and computer
1988 EPA rating:City-14 Comb-17 HWY-23
My car has a 3.08 rear gear and the 1988 manual should come with either 2.73 or 3.08. I am just writing them both off as 3.08
My car currently has 225/70r14 and the stock tire on a 88 is 225/60-15
The 14" tire is 26.40" and the 1988 is 25.62"'
So if I stay with that size tire the operating RPM would naturally be lower. I can even go bigger if need be. (14" tires are hard to come by in this size)
Another thing I have going for me is the stock gear ratio of the t-5. I got this off of the interwebs so might not be 100% correct.
T-5s by year
84 1st 2.95 2nd 1.94 3rd 1.34 4th 1.00 5th .625

85-89 1st 3.35 2nd 1.93 3rd 1.29 4th 1.00 5th .675
5th gear has a lower ratio in the 84 versus the 88. Thus improving over a stock 88.
To recap the rear ends are the same, I am running close to 1" taller tire on the rear slowing rpms at speed, and my transmission is .050 lower than a stock 1988 Mustang GT. So given the EPA "rated" the 1988 at 23 HWY I believe with those 2 things I should be better than 23. Whether thats 25 MPG we will see.

1trickpony · 10-30-2012, 06:35 PM

If anyone smarter than me can figure out what I should be getting, that would be awesome.

deathcomesarippin · 10-30-2012, 06:58 PM

Welcome! I have a mustang as well (kinda runs in my family.) I have a Sn-95 model, so completely different aero wise from the fox bodys. I know 85 is the first year Ford put that fuel injection, I dont know how much better they upgraded that system in 87.. but if they didnt make any changes I know I would stay with a carburetor-ed engine. Much more options/ after market things you can do to a carbed 302, than you can with that year fuel injection, I dont think ford intended MPG at all with that fuel injection system. thats just my 2 cents.

the t-5 is great! If you have 3.08s do still have the 8.8 rear end? do plan on changing the rear gears? If you want to get serious ($$$) id swap out for a good 9 inch, probably could weigh less.

Aero wise, its really fun to mess with a stang, even though I have a newer-ish model im trying to go for that older trans am road racing look, and the aero mods I have done so far are making it happen haha!

1trickpony · 10-30-2012, 07:11 PM

In 1984-85 ford had cfi which really wasn't that good. I believe in 86 they went to a one year only efi. 87 was the first "good" year. 1988 was still speed density which is what I have.

The 3.08 are in the factory 7.5" rear. When I upgrade it will be to the 8.8" out of a sn-95 and 5 lug. Will probably run the stock 3.27 for a while.

As far as mods go, I really want them to look good over all. Subtle yet clean.

deathcomesarippin · 10-30-2012, 09:54 PM

Ok cool, didnt know that about the EFI! I feel you about the appearance, with a fox body id be more picky with what body mods I do. What wheels do plan on putting on? maybe some dish wheels? And I think a front air would help this car out alot. Maybe some rear window louvers?

UltArc · 10-31-2012, 08:46 AM

Myself, would def do rear window Louvres in a fox.

1trickpony · 10-31-2012, 02:07 PM

I personally love the louvers. My wife on the other hand does not. If I find one with the right price I might buy one. Another thing I have been thinking about are those lexan light covers. I don't like the way they look. But if they prove to be an improvement they are something I could remove at shows or when ever I want