Mileage on 84 5.0

[fgross2006]

And what size are your tires? If they're taller than stock, the speedometer will read slower and the odometer will record fewer miles.

I did pull the stock TRX rims and tires and replaced with 15 inch rims from an 87 Mustang.

I have 225/15 in the rear and 198/15 in the front

Inflation is good although I will re-check them this weekend.

[grabbergreen84]

If my calculations are correct, and if your tires are 225 60 15s, then they end up being 20 mm taller than the original 220 55 390s, which the TRXs had. That will make your speedometer run slow, and the odometer will register fewer miles. Do you have a GPS? You can get accurate MPG calculations from those. You can also measure a distance with another car, and compare to the Mustang.

[fgross2006]

If my calculations are correct, and if your tires are 225 60 15s, then they end up being 20 mm taller than the original 220 55 390s, which the TRXs had. That will make your speedometer run slow, and the odometer will register fewer miles. Do you have a GPS? You can get accurate MPG calculations from those. You can also measure a distance with another car, and compare to the Mustang.

I will bring my GPS to work Monday. ill zero the odometer and see if the mileage on the odometer jibes with the GPS.

It still won't change the fact that I consistently get 120 miles out of 10 gallons.

[fgross2006]

I finally had an opportunity to get under the 84 and get pics of the gas tank,

Definitely from a junkyard, has yellow pencil markings on it.

But, is this a 15.5 gallon tank or not?Attachment 78932Attachment 78933Attachment 78934Attachment 78935

[RamblerSteve]

Old school as such, stock CA smog, no computer but plenty of mechanical smog stuff including cats. 302 punched out to a 306, RV cam, C4 Street Fighter auto trans. With 600 cfm 4V it gets 11-14. With 2150 2V it gets 15-18 mpg. Stock 12.5 gal tank shows empty at 10 gallons. Nice to know I still have 2 gallons left when the light comes on. 3.55 8.8 trac-loc ear end, 5 lug conversion with 15 inch Drag Lites, 225/50's on 7 inch rims up front, 245/50's on 8 inch rims out back. Don't know if that's good mileage in that setup or not. Changed speedo gear so its accurate within 2 mph just like my stock Ford Escape. Seems like the EFI cars get better mileage, but it's a fast little car with either carb on it.

[fgross2006]

So after changing all my sensors and putting Motorcraft sensors in my car, putting in a hi performance K&M air filter, clearing all the failure codes and getting the car to run with no codes (other than occasional code 18 in CM) I'm still getting poor mileage.

The car runs great, idles nice, has nice horsepower. But im stumped as to why im only getting 10.5 MPG.

[stevecap04]

That seems really low, my 88,89 got about 20-22, havn't driven 84 really to find out what im getting yet.

[fgross2006]

That seems really low, my 88,89 got about 20-22, havn't driven 84 really to find out what im getting yet.

Theres nothing left to tune or tweak. All I can do now is to pull the engine and have it rebuilt.

[Boss 429]

1980 Cobra, 255, 2:26 rear end, C4 Driving Dayton to Tampa twice, would return 29-30 MPG at 65-70mph. I thought this was great for a car of that era.

[grabbergreen84]

1980 Cobra, 255, 2:26 rear end, C4 Driving Dayton to Tampa twice, would return 29-30 MPG at 65-70mph. I thought this was great for a car of that era.

Holy cow! I wonder what it would do with an AOD. That's especially amazing with a direct-drive C4. My '88 has gotten 26 on the highway before.

[fgross2006]

I'm at a total loss why I'm only getting 10.5 mile per gallon. And I drive 90% highway when I commute to work.

The car runs nice, idles smooth, except for the occasional idle hunting in park. It also has a slight cluck in the power train when I accelerate or decelerate. I'm trying to figure out if there's play in the rear or the tail shaft of the tranny.

I pull no codes when I scan, There's nothing left to tune. I have all new ignition parts.

I just did up the entire front end, suspension, motor mounts, tranny mount, U joints and alignment this weekend. I'm curious if that will improve mileage at all.

[xctasy]

I'm at a total loss why I'm only getting 10.5 mile per gallon. And I drive 90% highway when I commute to work.

The car runs nice, idles smooth, except for the occasional idle hunting in park. It also has a slight cluck in the power train when I accelerate or decelerate. I'm trying to figure out if there's play in the rear or the tail shaft of the tranny.

I pull no codes when I scan, There's nothing left to tune. I have all new ignition parts.

I just did up the entire front end, suspension, motor mounts, tranny mount, U joints and alignment this weekend. I'm curious if that will improve mileage at all.

One or all of these three reasons will be causing 10.5 mpg.


1. Air fuel ratio is scaled out
2. Drag factor with the roof down (or brakes or wheel bearings binding)
3. Excessive exhaust back-pressure

One. Drag factor with the roof down. Most convertibles are about a Cd of 0.70 with the top down, which is why top speed in your case drops 15 mph , from 120 to about 106 with the lid down, and fuel consumption skyrockets on a motorway cruise. If you are top down motoring, the drag factor drops from 0.42 with the hood up to something like 0.70, which is 2/3rds more, compounding to the cube root each mph faster you go.


A conservative 40% increase in drag from the stock roof up Mustang gives a 20% increase in mpg at 55 mph. 24 mpg would become 20 mpg.
I personally think you'll be loosing 70% on your roof up drag.

By my road load calculations, At 55, mph, a 70% gain in drag will take about 50% off your fuel economy, or 8 miles per gallon off your normal 84 CFI years 24 mpg highway EPA figure. Making 16 mpg. If you drive at 65 instead of the EPA's old 55 mph mpg speed, then you'd go down more.


Before you do anything, you need to do a Low Speed 60 to 10 MPH coast-down test on dead level, flat cement or good asphalt or tar-seal macadam.


Here is how two people can do it

http://www.instructables.com/id/Meas...t-of-your-car/

Download Drag_Coefficient.xls

Here's the SpeedWhiz input sheet http://www.speed-wiz.com/calculation...alculation.htm


I'll run the calcs for you.

For safety, you can use kph, at 70, which would require readings at 0, 10, 20, 30, 40, 50, 60 and 70 seconds from 44 mph.



Here's how it works on big trucks. http://fleetowner.com/video/aerodyna...t-down-testing

with the roof up to see if the brakes are binding.

You throttle off after a 44 mph constant speed, and measure the time from go to woah. Ford says never Put your AOD or C5 in N, but you'll have to try it safely.



Second, Air fuel ratio is out. Some people used to trick the a/f readings to get more performance.

Buy or borrow a wide band O2 sensor and multimeter, and weld a bung in the exhaust at the first cat.


You need to verify two things. Firstly, you actual lambda voltage with a known good O2 sensor. Its should be close to stoichometry or 15.2:1 in close loop on today's oxygenated fuel. Under open looe, should be 12.5:1 or so. That will verify air fuel totally. The CFI EEC unit will always take care of that very well. No codes, no problems generally.

Thirdly, excessive exhaust back-pressure, I assume your exhaust back-pressure is very high. The same bung can be tapped with a fuel pressure gauge to measure back-pressure. It should be way less than 4 psi. If its not, then that's your problem.

Is the primary light off converters flapper valve working properly? If not, back pressure will be high.


The previous owner did this with my Mustang...

Put in a tell tale 02 light that glows when off stoichometery, and an O2 sensor to drive it.
http://vb.foureyedpride.com/showthre...-spec-Bcode-I6

I know, I just like the look and sound of a dual exhaust. I will probably wind up going for custom pipe work and letting the muffler shop deal with it

After doing 1, 2, and 3 above, you can then look at other exhaust options.

No car should do 10.5 on the highway. If my 92 hp 3.3 B code 81 Fox had a convertible roof down at 65 mph, then its 17 mpg would be about 10.5 though.


NB// I've been involved with Coastdown tests since 1997, when a certain New Zealander (Doug McMillan) took out the 1300-1600 cc LandSpeed Record with a Honda CRX. He posted the drag factor and coast down info, and has been doing Bonneville speed runs with his wife at 242 mph in a VTEC Civic. Doug was the founder of Hondata down here in Dunedin and with the help of a man named Derek from Auckland they went to the US.

[JACook]

Great suggestion about doing coast-down runs, as even small things creating drag can really have a large effect
on highway fuel economy. And while I can see why you would never want to pop an automatic in neutral and
coast with the engine stopped, I can't think of a single reason why it would harm the transmission if the engine
is kept running.

Interesting comment too about making sure the flapper is working properly. While the CFI engines do not have
the passenger-side light-off catalyst like the 4V engines do, they do still route exhaust through to the passenger
side, to heat the intake when the engine is cold.

One other comment WRT O2 sensor monitoring - The O2 sensors will only have an accurate view of the oxygen
content in the exhaust, when the secondary air system is in downstream mode. So whenever you're monitoring
the O2 sensors, you have to also monitor the diverter valve mode. (And as I've said in the past, you really need
to be absolutely certain there is no false upstream air getting into the exhaust during closed-loop operation.)

[fgross2006]

Great suggestion about doing coast-down runs, as even small things creating drag can really have a large effect
on highway fuel economy. And while I can see why you would never want to pop an automatic in neutral and
coast with the engine stopped, I can't think of a single reason why it would harm the transmission if the engine
is kept running.

Interesting comment too about making sure the flapper is working properly. While the CFI engines do not have
the passenger-side light-off catalyst like the 4V engines do, they do still route exhaust through to the passenger
side, to heat the intake when the engine is cold.

One other comment WRT O2 sensor monitoring - The O2 sensors will only have an accurate view of the oxygen
content in the exhaust, when the secondary air system is in downstream mode. So whenever you're monitoring
the O2 sensors, you have to also monitor the diverter valve mode. (And as I've said in the past, you really need
to be absolutely certain there is no false upstream air getting into the exhaust during closed-loop operation.)

Whats a flapper?

Much of the advise in the previous post is out of my league. I didn't understand much of it

[xctasy]

JACook is right. The CFi doesn't have 4-bbl M code carb exhaust flapper valve...Sometimes, there is a restriction with the 4-bbl. I was wrong about that for your CFi, but there could still be a backpressure issue.

Spend some time reading this

http://vb.foureyedpride.com/showthre...ng-5-0-exhaust



1984 Mustangs and all 5.0 M code Foxes vary so much. One is 4-bbl carb fed, the other Central Fuel injection, totally different, but 2-bbl Carb like with the same M Vin code as the 4bbl.

Ford really should have given them specific codes, so we don't get confused. Ford has done this before, like with the 2.3 CarbTurbo having the same engine code as the non turbo.

"M" - 5.0 liter 4V (5-speed manual - 175 hp) or
"M" - 5.0 liter CFI (automatic - 165 hp) V8 302 CID .What the...

The exhaust varies, with the 4V having a very restrictive but effective passenger side light off converter.
The 5.0 CFi never needed one any of its years, its a very clean running engine, but Iin the Fox Mustang and Capri and LTD/Marquis, runs the same odd passenger side priority heat stove to the CFi intake air heat.





Flapper valve Post #17 on 6-26-2014, 08:37 AM by boboli

Since you asked about the heat riser, I found one of the 85 ones I have. I think I tossed the other long ago. There are 2 on ebay right now( 1 used and 1 new) that look exactly the same.
from the rear


from the engine side


the label on the vacuum canister has long since been destroyed, so I can't read any #'s. The label almost looks to have a bluish color, but I can't say if that is original or just from time. The original on ebay has a red sticker. Maybe they are color coded to size? The only cast # on the valve body is a #4 right at the corner, near the vacuum canister.

Sorry about the gobbledegook. I've kind given you a menu list. Its kind of hard to diguest in one post, but any more amplification won't help. Chip away at understanding those three things if you've got time, but don't wear yourself out with it. If you can understand a coastdown test, and take some safe time out to do it, it will help. If its to insanley hard to get your mind around it, don't go any further with it.



The CFi is a really good combo, if you go through the checks I've suggested, you'll sort out the economy problems.

I couldnt simplify the three items below:-
1. Air fuel ratio is scaled out
2. Drag factor with the roof down (or brakes or wheel bearings binding)
3. Excessive exhaust back-pressure..


One two or or all three will be the reason for the economy drop.

[fgross2006]

JACook is right. The CFi doesn't have 4-bbl M code carb exhaust flapper valve...Sometimes, there is a restriction with the 4-bbl. I was wrong about that for your CFi, but there could still be a backpressure issue.

Spend some time reading this

http://vb.foureyedpride.com/showthre...ng-5-0-exhaust



1984 Mustangs and all 5.0 M code Foxes vary so much. One is 4-bbl carb fed, the other Central Fuel injection, totally different, but 2-bbl Carb like with the same M Vin code as the 4bbl.

Ford really should have given them specific codes, so we don't get confused. Ford has done this before, like with the 2.3 CarbTurbo having the same engine code as the non turbo.

"M" - 5.0 liter 4V (5-speed manual - 175 hp) or
"M" - 5.0 liter CFI (automatic - 165 hp) V8 302 CID .What the...

The exhaust varies, with the 4V having a very restrictive but effective passenger side light off converter.
The 5.0 CFi never needed one any of its years, its a very clean running engine, but Iin the Fox Mustang and Capri and LTD/Marquis, runs the same odd passenger side priority heat stove to the CFi intake air heat.





Flapper valve Post #17 on 6-26-2014, 08:37 AM by boboli




Sorry about the gobbledegook. I've kind given you a menu list. Its kind of hard to diguest in one post, but any more amplification won't help. Chip away at understanding those three things if you've got time, but don't wear yourself out with it. If you can understand a coastdown test, and take some safe time out to do it, it will help. If its to insanley hard to get your mind around it, don't go any further with it.



The CFi is a really good combo, if you go through the checks I've suggested, you'll sort out the economy problems.

I couldnt simplify the three items below:-
1. Air fuel ratio is scaled out
2. Drag factor with the roof down (or brakes or wheel bearings binding)
3. Excessive exhaust back-pressure..


One two or or all three will be the reason for the economy drop.

I belive I saw something that looked like a heat riser on the passenger side of my car. Do the CFI models have them?

[xctasy]

Sorry, I misread JA Cooks response...I knew that Ford used very specific components, and I've not been able to find pictures of the 84 CFI verses 84 4-bbl

84 and 85 cars were very different, so were CFI and 4-bbls. Anyone will move to the 86 system, due to problems with the many changes to the 84 and 85 CFI and 4-BBL systems


"While the CFI engines do not have the passenger-side light-off catalyst like the 4V engines do, they do still route exhaust through to the passenger side, to heat the intake when the engine is cold."


Therefore you are correct, what you see is the vacuum operated heat riser valve on your CFi too.





On 85's (which generally had tubing headers), its found in this post

http://vb.foureyedpride.com/showthre...Pipe-Questions

Is this it installed?

[fgross2006]

Sorry, I misread JA Cooks response...I knew that Ford used very specific components, and I've not been able to find pictures of the 84 CFI verses 84 4-bbl

84 and 85 cars were very different, so were CFI and 4-bbls. Anyone will move to the 86 system, due to problems with the many changes to the 84 and 85 CFI and 4-BBL systems


"While the CFI engines do not have the passenger-side light-off catalyst like the 4V engines do, they do still route exhaust through to the passenger side, to heat the intake when the engine is cold."


Therefore you are correct, what you see is the vacuum operated heat riser valve on your CFi too.





On 85's (which generally had tubing headers), its found in this post

http://vb.foureyedpride.com/showthre...Pipe-Questions

Ive seen heat risers on NOS websites but I want to be sure what I need. they're not that cheap and I don't want to waste money.

[xctasy]

http://www.scribd.com/doc/26804743/H...s-David-Vizard

*Source:How to Modify Ford SOHC Engines (Pinto/Cortina/Capri/Sierra 1.3- 2.0 litre 1970 to 1982) by David Vizard, published 1984 by Fountain Press.

Page 83-85, CHAPTER FIVE Exhaust Manifold & Exhaust System
ISBN 0 86343 9856, Dewy Decimal No 629.2504 Viz

Read up on diagnosis of excessive pack pressure, 3psi is common. The best Ford 5.0 was the Aussie 1997 EL GT with 4.5 kPA, or 0.65 psi.

If its more than that, buy parts.

But diagnose first with borrowed equipment. Get someone to weld or braise in a measurement port for a wide scaled fuel pressure gage.


For air fuel, chassis dyno time with an EGT gage, with JACooks important notes on air pump operation.


Remember. all we are looking at is Why the 10 Em Pee Gee? Going on a replacement mission is expensive, but focused diagnosis will answer your problems.


If its just a
binding wheel bearing,
the top down motoring you do effecting the mpg,
an air fuel problem not diagnosed
and some kind of restriction (clogged cats, or soaked mufflers full of rust),

then you'll instantly go up to 24 mpg at 55 mph when relieved of it.


I put a resister in my dads 1984 Toyota 1.8 CFi temperature input to the ECU, and scaled the air fuel ratios up to 16.7:1 at cruise, 12.5:1 at open loop, and avoided the Check Engine Light. It just required a timing bump to 14 degrees static from 9 dbtc stock, and 93 octane to do it. It performed great, with the little 112 cubic inch engine doing 37 US mpg, and driving the 4 speed auto overdrive like it had a 2 liter/121 cubic inch engine. When retuning to 9dbtc factory specs on 91 octane by a mechanic in Dads town after a noisy lifter was detected, the CEL came on, and off course the technician removed the resister. Sometimes, AIR Fuel is scaled out by modifications like this, without a fault code being registered. It was a common way of cheating the stock air fuel tables.

One last one. The operation of the IC's in the ECU. Sometimes they degrade or short out, and the computer has to do more work to solve valid closed loop air fuel ratio's. It might not even register a code in that instance.