North American Turbocoupe Organization

The *official* gas mileage / engine combo thread!
Ryan H Offline
Posting Freak
I thought it'd be a good idea for everyone to post their combos and what mileage they get, if of course you use an accurate method to calculate your mileage.

Please let me know if there are any other values I should add here!

Car: 88 TC
Options: 5 speed, all others (except sunroof and leather)
Mileage: 114,350
FP at idle: 40
TPS: .91 (new IAC, base idle is "near stalling" speed)
Base timing: 12*
Spark gap: 0.032"
Tune up parts: All Ford with Belden spark plug wires.
Spark plugs: Autolite 103
Boost: My wastegate reference line is disconnected. It seems to peg at 22 PSI on my Autometer gauge.
Octane: 93
Exhaust: Stock downpipe with a gutted cat, dumped right after the cat.
Tire/wheel size: Stock wheels / 225 60 16
Vacuum at hot idle: 17" (I have worn cam & follower lobes.. Could this be it?)
Cooling system: Bone stock, new ECT from NAPA. This includes the thermostat temperature range.
Turbo: Stock IHI, braided feed line, stock intercooler & hoses.
Air filter: K&N cone on VAM.
VAM voltage readings: (N/A, will get these ASAP!)

Maintenance history:

At 89,000 miles:

- Head gasket done as preventative maintenance. It was not needed. While this was done, I cleaned the entire top end with a pressure washer and a TON of brake cleaner, this was with the head disassembled.
- All engine ground wires have been cleaned. New battery & starter cables were installed. I added a few grounds from the negative battery post to various places on the frame and engine.
- Differential was flushed out and fluid was replaced with Mobil 1 synthetic 75W 90
- SPEC Stage III and new flywheel from NAPA was installed. Rear main was replaced, friction modifier was added to the transmission. I also ran some Sea Foam through the engine oil before I changed it.

Recent changes:

- Sea Foam'd the fuel system and intake.
- Did the clutch, replaced with a stock unit and had the flywheel surfaced. Did not add friction modifier to gearbox this time around.
- Flushed the entire brake hydraulic system
- Flushed the entire clutch hydraulic system
- Changed gear oil to Rotella 85W 90
- Water pump was changed
- A/C belt disconnected (pulley broke)
- All new brake pads, rotors, one new caliper. New front wheel bearings to go with the new front rotors. I used Mobil grease.
- New front swaybar bushings, and end links. Energy Suspension.

And finally, the good stuff:

55 MPH cruise, I average 36 miles per gallon. The way I calculate this is by topping my tank off completely, and driving until I'm damn near out of gas (or out of gas). I have a 5 gallon can I keep filled when I do this.

70 MPH cruise, I average 32 miles per gallon if I don't use the cruise control. If I use the cruise control, I usually only average 30 miles per gallon at these speeds.

75 MPH cruise, I average around 28 MPG and my tach is sitting almost on top of 3,000 RPM at this point. At 80 MPH, I only get about 26.5 or 27 MPG. These are using cruise control, on nicely paved highways with not many hills. (Mostly I-10, I-75, and I-4 here in Florida).

In the city, well, I drive like an A-hole and I get about 15-17 MPG usually. LOL

I hope this thread gets something started!
'88 TC Smile Walbro 255HP, Stinger FMIC, PIT BOV, Pro 5.0, Kirban, RR cam, FRPP strut tower brace, T3

Matt S Offline
Posting Freak
Oh yeah this is good. Here's mine:

42lbs base FP
sc50 60/63
Head rebuilt with new valve seats at 80k
15k on all new motorcraft sensors
Magencor wires, 764 plugs
3" cone intake
3" dp - 3" catco cat - 3" ultraflow - 2.5" tp

Tripminder is dead on when not above 3k cruising

29.5mpg at 75mph/3k rpm's across the great plains, i.e. "flat" cruising with cruise control
28.2mpg between WA and CA across mountain passes 800 mile average total, mixed cruise control

27 or less above 3k (confirmed with same station fillups)

18-21 city driving no matter how I beat it.

Highest seen: 31.5 at 70mph or less

Totall 5700 mile round trip WA to PA and back 28.2 (was 29.5 until Montana mountain passis)
Sold it Sad*

Walsted Offline
Posting Freak
Mine: 86 TC with 270K+ miles, LA3 conversion, .94 TPS, 34 gap, 3.55, 23560R15, BCS bypass w/ 16psi or so limit, .390 cam (stock SVO/87-88 TC), so many tools in the trunk the rear rides low and there is no room for luggage, usually 1/2 tank or better: 25 mpg or better in the California desert, with 55mph and 70mph highways, 23mpg in D/FW traffic with a disproportionate number of idiots on the road who put me in situations where I have to floor it or get in a bad situation.
Mike Walsted - Sold my 1986 5-speed TurboCoupe

MeAndMyT Offline
Senior Member
about 19 miles to gallon street... 22 or so on highway.. i dont know why.. Tps is bad maybe thats the prob?
88 TC 5 spd 22x,xxx miles Ran 15.3 in 1/4.. K&N Cone. Gillis boost controller @ 15. Faze Boost Gauge. A/C belt off. 2 1/2 inch exhaust dumped at axles.

Hurff Offline
Senior Member
From the newly installed tripminder....

Which is dead on for me. Distance traveled matches the ODO & known distances.

29-32 highway (avg)

24-26 city (DC driving stop & go)

with an avg speed of 32 mph (over a 35 mile trip) I get 25.4 mpg.

The irony is that the fuel gauge (I believed) was fairly accurate. After the tripminder I experienced (or just finally noticed) the two-state stability (instability ?) of the IVR. Now the gas gauge never goes to full, but it is real easy to track fuel used. I am getting to the point where I consider the gauges on the right side of the dash are 'just there for looks) and the ones on the left are 'its important info, but take these readings with a grain of salt...'
1987 TC - RIP

slacken00 Offline
Senior Member
well i think i have the worst for sure and i dont know why, buy i have a stock rear, fuel pres. is set at 43, 255lph. fuel pump, ported big valve head, a237 cam, vac. at idle is only 13ish, sc50 set at 17lbs. of boost, stinger 3" exhaust no muffler or cat, i dont really drive it that often just to work a couple times a month but when i do it gets around 12-13 mpg. and when i drag race it gets somewhere around 8-9 mpg. i run 94 oct. and about 5 gals. of turbo blue 114 oct.
88 tc black, sc50, stinger 3 inch ex, 255 lph fp, kirban afpr, bov, ported big valve head w/a237 cam, gutted upper intake, (knife edged lower, 75 pph inj. not on yet), spec 3 clutch, street tires best run 13.9, best mph. 109.5(no tuning)

2008 ford edge sel awd
2000 ford mustang gt,exhaust intake chipped

trashline Offline
Posting Freak
I average about 18-20 mpg. this is all stop and go traffic. And Im only out of boost when I shift the car Smile . 200,000 miles mods in profile.

06 Cobalt SS
66 mustang 289 C4 handfully modded

Stingers IC install and tbird photos

turbokev Offline
Senior Member
It's amazing how much wind resistance plays into fuel mileage..

My tripminder says I'm getting 32 mpg when I'm cruising on a flat surface at 50 mph.. if I kick it up to 75 mph the mpg's drop to 25 and at 85 they drop to 20.

Yes, I know the rpms are different, but even if I kick up the rpms at 50 mph by driving in 4th instead fo 5th gear, I still get 28 mpg.

I think the Tbirds are not as aerodynamic as they look?

At any rate, my car is tuned with Motorcraft parts, has a catless 3" single exhaust and my boost controller is set to 16 psi. Tank over tank I average 22 mpg.. but I do a fair amount of stop and go driving and I'm fequently on the boost going through the gears.
Kev Schofield
1989 Corvette

85, 2x86, 87 & 88
(former TC's)

KentCT88TC Offline
Senior Member
I just got this car in October, and it was running poorly and idling all over the place. Had it tuned up with new wires, Autolite plugs, new IAC, O2 sensor, and Motorcraft Throttle Position sensor. Using stock IHI, Gillis set @ about 16 lbs. The last mechanic who got the idle right sez these cars do better with 20-50 oil (I use synthetic), because otherwise the oil leaks around the turbocharger, so I switched to that. He said the turbo was in good shape. Lots of idling with daily traffic jams coming and going from work.... Not much highway driving yet, but when I do, it's usually 70 MPH and I'm using the turbocharger. Use 93 octane gas. Today when I checked the MPG it was only 15.8! Last week, it was 20.5.... I am taking it on a trip, and hope it does better at highway speeds (that is if I dont have to sit on the NJ Turnpike again). I am not sure I have a problem yet, but am disappointed at the mileage on a 56,000 mile car. -Kent
-'88 Turbo Coupe, K&N, Gillis valve @18 lbs., 2.5 " exhaust.
-2000 Mustang GT 373 gears, Diablo computer chip, cold air intake, Typhoon intake manifold.
-2001 Jeep SE 2.5, AEM cold air intake, Gates headers & exhaust, throttle body spacer, Jet Stage 2 chip

Import Killer Offline
Senior Member
Crap Recon crate engine
A237 roller cam, intake, 3' exhaust, oil smoking turbo: 17 city 24 highway Sad

My daily driver is now a project

Dont ever buy a recon motor
1987 Turbocoupe
Painted sonic blue pearl
Ground effects w/S351 wing
17x9 Chrome Cobra Rs
255/45/ZR17 Kumho 712s
KYB suspension
MOMO shift knob and boot
K&N cone air filter, Gillis boost valve, T-3 turbo, ported intake and E6, A237 roller cam, MSD coil, Kirban FPR
Full 3" exhuast w/Ultra Flo muffler
Brute force clutch
White faced indiglo gauges
2 12" Rockford Fosgate subs and amp

Users browsing this thread:
1 Guest(s)

Theme © iAndrew 2018 - Software MyBB