Real Fiero Tech

Well, I fixed my cruise control. I hadn't really put much effort into thinking about it since it's not a huge deal that it works right, but, it is annoying when I hold 'SET' to set my speed, then have to hit 'RES' a couple of times before the pedal drops under my foot. It would always drop 2-4mph otherwise.

While taking a moment to look around my engine compartment, I jiggled the cable from the cruise solenoid and found it to have a bit of slack. I figured 'what the hell' and moved the cable up a few notches in the thing to take the slack out, and low and behold the cruise works almost perfectly now. I might up it one more notch to make it taught.

BTW, I find that I get (at least) 21.5mpg on the highway with the stock 2.8 (that I replaced.)

21.5 mpg on the highway is not something you should be proud of..

My AWD 6000 with 3 speed auto and wide sticky tires does 22.5ish turning 3500 RPM at 75 mph.

my 86 gt 4spd gets 40+mpg on the highway

cactus bastard wrote:21.5 mpg on the highway is not something you should be proud of..

I didn't figure it's something I should be proud of, but it's better than the old engine. I don't know what really else to do to get the best out of what I have. Everything is stock.

lucky80 wrote:my 86 gt 4spd gets 40+mpg on the highway

With a stock engine :scratch:

not quite...

MSD GM dual connector coil
Mallory #812 ignition module
MSD cap rotor and superconductor wires
delco rapidfire plugs
K&N stock replacement air filter
160deg thermostat
hypertech street tuner chip
5w30 Castrol Syntec in the crankcase
Redline MT90 in the Isuzu

Lots of spark, plenty of air, stock fuel delivery, and I replaced my factory EGR with a GP Sorenson replacement. The aftermarket EGR came with a bag of airflow restrictors designed to size to meet the OE requirements of aproximately 200 different OE #'s using 15 - 20 different restrictors.
I threw that bag away, bolted it on the way it came out of the box, and removed the flow restrictor from the EGR tube to Plenum gasket cause it just clogs anyway. I run on 89 octane with 3 - 4 oz of Lucas fuel injector cleaner to every other tank of gas to combat the evil ethanol.

Last month I drove from Seekonk MA to Troy NH about 200 miles round trip on less than half a tank doin 70 to 75 the whole way.
:thumbleft:

How short are your miles and how big are your gallons?

I got 38 mpg at best with the duke (70 mph on the interstate without stopping at all) and 30 mpg at best with the 3.4 DOHC (75 mph on the interstate without stopping), both of which are much more efficient than the ol' 2.8 (especially with a four-speed).


EDIT: Wait, you said in your other post 4-speed and now you wrote Isuzu. What do you have?

isuzu designed the 4spd too.

my 2.8s a fairly fresh rebuild (40k or so)
most of my major sensors are new, many pigtails as well.
I'd be willing to bet that i'm running a little leaner than i probably should be due to a timing issue but no detonations so it can't be that bad.

Don't have to be a rocket surgeon to do the math
stock tank = approx 10 gallons
200 miles, less than 5 gallons = 40mpg+
doin 70 to 75 no cruise control

When I pay attention to the shift light i can go 2 weeks on a full tank back and forth to work 15mins each way 5 days a week.
When I'm actually driving it like a sportscar my mileage goes way down.

lucky80 wrote:isuzu designed the 4spd too.
.

Got a source for that?

And your mileage calculation doesn't sound like a very scientific method. Once you use a Fiero gas guage as a scientific instrument, the reliability of the data becomes suspect.

stimpy wrote:

lucky80 wrote:isuzu designed the 4spd too.
.

Got a source for that?

And your mileage calculation doesn't sound like a very scientific method. Once you use a Fiero gas guage as a scientific instrument, the reliability of the data becomes suspect.

LOL, I use the fuel pump as a scientific instrument. When it starts crying, I know I have not much gas left.

Trip meter = 215 miles from a full tank, just move the decimal over to the left to give mileage.

lucky80 wrote:isuzu designed the 4spd too.

What?

my 2.8s a fairly fresh rebuild (40k or so)
most of my major sensors are new, many pigtails as well.
I'd be willing to bet that i'm running a little leaner than i probably should be due to a timing issue but no detonations so it can't be that bad.

I'm running 15.4:1 AFR in highway mode with a much better flowing engine with just over 10k miles on it on a full rebuild and balance and I still don't get over 30 mpg

Don't have to be a rocket surgeon to do the math
stock tank = approx 10 gallons
200 miles, less than 5 gallons = 40mpg+
doin 70 to 75 no cruise control

Have you ever run out of gas? I'll bet you will with the gauge not far from the halfway mark. If you could make 40mpg with a 135 hp V6 and a 4-speed with a not-so-ideal highway gear I'm sure modern car makers would love to know how!

lucky80 wrote:Don't have to be a rocket surgeon to do the math
stock tank = approx 10 gallons
200 miles, less than 5 gallons = 40mpg+
doin 70 to 75 no cruise control

Try again. Real fuel mileage calculations involve odometer readings and gas receipts, with the appropriate work done to record odometer accuracy.

wow, didn't mean to spark such controversy and i totally didn't mean to hijack this thread, but let me address a few things:

The Dark Side of Will wrote:
Try again. Real fuel mileage calculations involve odometer readings and gas receipts, with the appropriate work done to record odometer accuracy.

I didn't claim it was an actual bonafide 40.whatever mpg.
based on the fact that my guage seems fairly accurate and it has never taken more than 9.5 gallons to fill my tank from empty, and the fact that the three trips from seekonk to troy that i've taken in the last two months (two in my fiero, one in my fathers f150) were all approximately the 211 miles that mapquest said it would be, I did a rough calculation. The first trip in the GT I had my buddy steve with me, he weighs 360 lbs., my mileage was closer to 35 (approximately) on that trip, but by myself with an empty trunk it was approximately 40.

series8217 wrote:
Have you ever run out of gas? I'll bet you will with the gauge not far from the halfway mark. If you could make 40mpg with a 135 hp V6 and a 4-speed with a not-so-ideal highway gear I'm sure modern car makers would love to know how!

I have in fact run out of gas, the second week I had this car (mid Sept last year) it was about 4 miles after the needle hit E. I already posted what i'm running that's not stock, I noticed a huge difference with the MT90 in the tranny. And this engine loves Syntech, I also use a synthetic block flush every other oil change to help prevent deposits.


lucky80 wrote:
isuzu designed the 4spd too.
Stimpy wrote:
Got a source for that?

Chilton's repair manual part #7571 1989 edition all us and canadian models pontiac fiero, Chapter 7 page 182
"The Pontiac Fiero that is eqiupped with a manual transaxle uses one of three types. The early Fieros were equipped with either a 4-speed 76mm Isuzu or 5-speed 76mm Isuzu transaxles. ...."
Haynes manual description from 1989 era is virtually the same.

Once again Starlite sorry about hijacking the thread,
I'll start a new one so people can doubt me there.

i was able to get 36mpg with my 84 4cyl 4speed econo gearing and skinny 175 tires.

I have a feeling that lucky has the incorrect VSS gear for his final drive/tire size.

I have a feeling that the chiltons is full of shit. The 4 spd is a muncie, and possibly designed by getrag, but Not Izusu.

The Factory service manuals are available online at www.fieronews.net for free download, so you can throw out the chiltons.

Haynes & Chilton's have been wrong about a number of things before.

Do a REAL mileage check over several tanks of gas and compare your odometer to interstate mileposts over significant distances (like over 20 miles).

I'm not saying haynes or chilton's are infallible, but have you ever had a 4 speed and an isuzu 5 speed side by side? they even look identical.
while the getrag is completely different.
And we all know they were all produced by Muncie.

I calculate my mileage by filling up the tank and zeroing the odometer. When I refill the tank, I divide the miles travelled by the number of gallons it took to refill the tank. I average around 28 MPGs travelling around 75 to 80 MPH with 2.8-3.4 conversion and 5 speed Getrag. I also checked my odometer and speedometer against my GPS and they are fairly accurate.

lucky80 wrote:I'm not saying haynes or chilton's are infallible, but have you ever had a 4 speed and an isuzu 5 speed side by side?

Yes.

they even look identical.

No