Fox Xtremely high fuel consumption

[Mindseye007]

Knock,knock,knocking on heavens door.
Maybe his balancer has moved and his timing is off.

You would think so @16 degrees how does running 87 octane and the motor does not knock? I Could not run @12 degrees with 87 it just pings and knocks until I run 91 or 94 then she purrs like a kitten. Most I had it was @14 then I got the sct chip and had her tuned on the dyno. I have always had the stock E7 heads never changed them yet .

 

[PonyGTrider]

You would think so @16 degrees how does running 87 octane and the motor does not knock? I Could not run @12 degrees with 87 it just pings and knocks until I run 91 or 94 then she purrs like a kitten. Most I had it was @14 then I got the sct chip and had her tuned on the dyno. I have always had the stock E7 heads never changed them yet .

Well friend I don’t know what to tell you and sorry to hear about that. Maybe the fact that the iron E7 heads can’t displace the heat as good as my aluminum twisted wedge heads, other than that don’t know what else could be. But I’m 100% positive I had my timing set at 16+ degrees. Now as I try to find the source of my excessive high fuel consumption I’m trying different timing settings but I’m finding that my problem is not related to timing.
Back when I had my engine in stock condition with the E7’s yes I ran at around 12 degrees.
Other than this don’t know what else to tell you, maybe others can elaborate more on this particular subject

 

[Mindseye007]

Well friend I don’t know what to tell you and sorry to hear about that. Maybe the fact that the iron E7 heads can’t displace the heat as good as my aluminum twisted wedge heads, other than that don’t know what else could be. But I’m 100% positive I had my timing set at 16+ degrees. Now as I try to find the source of my excessive high fuel consumption I’m trying different timing settings but I’m finding that my problem is not related to timing.
Back when I had my engine in stock condition with the E7’s yes I ran at around 12 degrees.
Other than this don’t know what else to tell you, maybe others can elaborate more on this particular subject

Have you had it on a dyno?

 

[PonyGTrider]

Have you had it on a dyno?

No I haven’t. There is only one “Dyno” around here and I went there but when we were just talking I knew they didn’t know what they were talking about so I left

 

[Mindseye007]

What rear gears you have? Also what is your tps set at?

 

[Bullitt347]

Anyone here have a car that can tell them what their "Instant Economy" is?
Take that car for a spin and drive it in a manner that results in 9ish mpg, and then try and keep it there.
It ain't easy to maintain that pace.
My 89' Mustang had a 331 cid S/C engine.
Bigger heads, cam. injectors and exhaust than the OP's ride.
I had to be driving with the engine making boost to get only 9ish mpg.
I will just leave it at that.

 

[PonyGTrider]

Anyone here have a car that can tell them what their "Instant Economy" is?
Take that car for a spin and drive it in a manner that results in 9ish mpg, and then try and keep it there.
It ain't easy to maintain that pace.
My 89' Mustang had a 331 cid S/C engine.
Bigger heads, cam. injectors and exhaust than the OP's ride.
I had to be driving with the engine making boost to get only 9ish mpg.
I will just leave it at that.

Yeah please Bullitt347: You “Just leave it like that”
You’re implying I’m making this up and that is BS.
What benefits would I gain by writing all of this? So if you’re satisfied with your “Eloquent” conclusion so be it. My problem is real but if you think I’m making this up then you better leave my posting with all due respect.
Right now I’m in the middle of a debate if I should take my engine apart to correct three cylinders questionable low compression and could be the final solution to my unusual high fuel consumption.

So yeah no offense but if you can’t help with proactive ideas, then just leave my posting.

Thanks Bud

 

[gkomo]

I was reading back through your thread and saw you compared your speedo to satellite devices. However, is your trip meter rolling correctly? Maybe you’ve actually driven further than what your trip meter is showing and that’s throwing off your calculations?

You should drive a known mileage trip and see if it matches what your trip meter is saying. Just a thought.

 

[PonyGTrider]

I was reading back through your thread and saw you compared your speedo to satellite devices. However, is your trip meter rolling correctly? Maybe you’ve actually driven further than what your trip meter is showing and that’s throwing off your calculations?

You should drive a known mileage trip and see if it matches what your trip meter is saying. Just a thought.

My speedometer and odometer have been verified and are accurate.
I calculate my miles/gallons based on the odometer not the trip meter by taking before and after readings

 

[PonyGTrider]

What rear gears you have? Also what is your tps set at?

Gears are 3.55 and TPS is set to 0.95 Volts

 

[DadLife0724]

You would happen to filling up your car at the same place repeatedly would you? Just throwing this out there, sub par gas is complete garbage and doesn't burn efficiently. That's all I got man. I've been following this thread closely and everything else I would have thought to say has already been said.

 

[Mindseye007]

Gears are 3.55 and TPS is set to 0.95 Volts

Have tried a new Motorcraft fuel filter ? What is the highest octane you can get a gas station where you live ? in canada we have 94 octane at petro canada gas stations, maybe try a tank of you highest octane see what kind of Milage you get from it .

 

[PonyGTrider]

Have tried a new Motorcraft fuel filter ? What is the highest octane you can get a gas station where you live ? in canada we have 94 octane at petro canada gas stations, maybe try a tank of you highest octane see what kind of Milage you get from it .

I haven’t try that filter,
The specification says that premium gasoline is between 91 and 93 intakes so let’s say it is 92

 

[LILCBRA]

I agree that something is off here and am curious to find out what the actual culprit is. The only thing I can offer/share is that my Cobra II is a very similar setup. The one and only time I recorded fuel mileage with it was when I road tripped it from Atlanta to Mustang Week in Myrtle Beach. It got roughly 19-21 mpg cruising at around 70 mph. And it ran pig rich. Here's a dyno video of it a couple years later to illustrate how rich it was running - I believe most here have seen it....


View: https://youtu.be/ehtnhnB9sEM


I'd suspect that if you're burning as much fuel as your calculations are giving, you'd definitely notice some sort of evidence. A dust trail like my car gave, some sort of residue or something in the tail pipes, fuel smell in the oil (as I did....), etc.

Here's my setup for comparison:
.030 over hypereutectic flat tops with valve reliefs
Twisted Wedge 170s
1.7 roller rockers
Melling 24203 cam
long tubes
2-1/2 dual exhaust with H pipe
I've ran with both an Offenhauser 360 intake and a ProComp knock off air gap dual plane intake
at that time, I ran a Holley 650 double pump that was obviously not set up right. (It now has a throttle body injection setup that I've not driven enough to give any mileage info, but I'd suspect that it's better than before.)
1995 Mustang GT T5,
3.55 gears
265/50-15 rear tires
Speedometer gears were installed to correct the readings given all of the changes to the drivetrain.

I guess a question that hasn't been asked - have you been under the car to inspect for any signs of leakage while on the road - like cleaned sections of the floor pans from a fuel spray? I mean I understand your concern, but it doesn't sound like the engine or drivetrain are the main culprits to me.

 

[PonyGTrider]

A quick UPDATE:
After searching for either a set of Autolite 3924 and NGK FR5 spark plugs which I found none I got a set of NGK FR5-1 which is longer than the NGK FR5 and before I threaded them in I measure the clearance against the piston and had about 0.200” gap. I then calibrated them to 0.054” then I took for a ride a few mile with some wide open throttle then return home and here is just a sample othe plugs out of cyl 1
I’ll wait for the engine to cooldown before I take the rest out.
So tell me now what do you think about the No 1 cyl coloration on these multi angle photos. Also there is a picture of the FR5 left and the FR5-1
Normal? Rich? Lean?

 

[PonyGTrider]

I agree that something is off here and am curious to find out what the actual culprit is. The only thing I can offer/share is that my Cobra II is a very similar setup. The one and only time I recorded fuel mileage with it was when I road tripped it from Atlanta to Mustang Week in Myrtle Beach. It got roughly 19-21 mpg cruising at around 70 mph. And it ran pig rich. Here's a dyno video of it a couple years later to illustrate how rich it was running - I believe most here have seen it....


View: https://youtu.be/ehtnhnB9sEM


I'd suspect that if you're burning as much fuel as your calculations are giving, you'd definitely notice some sort of evidence. A dust trail like my car gave, some sort of residue or something in the tail pipes, fuel smell in the oil (as I did....), etc.

Here's my setup for comparison:
.030 over hypereutectic flat tops with valve reliefs
Twisted Wedge 170s
1.7 roller rockers
Melling 24203 cam
long tubes
2-1/2 dual exhaust with H pipe
I've ran with both an Offenhauser 360 intake and a ProComp knock off air gap dual plane intake
at that time, I ran a Holley 650 double pump that was obviously not set up right. (It now has a throttle body injection setup that I've not driven enough to give any mileage info, but I'd suspect that it's better than before.)
1995 Mustang GT T5,
3.55 gears
265/50-15 rear tires
Speedometer gears were installed to correct the readings given all of the changes to the drivetrain.

I guess a question that hasn't been asked - have you been under the car to inspect for any signs of leakage while on the road - like cleaned sections of the floor pans from a fuel spray? I mean I understand your concern, but it doesn't sound like the engine or drivetrain are the main culprits to me.

Well I haven’t found that evidence yet.
About your last paragraph if I’m wasting over 50% of the fuel we are talking more than 7 gallons of fuel… I haven’t inspected both fuel lines from the engine to the tank it would be evident to see 7 gallons leak but in good fate I will lift the car to go underneath and will closely inspect all the fuel lines, I promise that

 

[gkomo]

Aftermarket heads like the TFS’s require different plugs. Were you running stock style plugs?? They will be too short and not get into the combustion chamber far enough.

 

[PonyGTrider]

Aftermarket heads like the TFS’s require different plugs. Were you running stock style plugs?? They will be too short and not get into the combustion chamber far enough.

I was using what everyone else the ones recommended by trick flow NGK FR5 but couldn’t find any so I’m using one a bit longer which is the NGK FR5-1 I posted a photo a few lines up

 

[AeroCoupe]

I would just wait until I could get a wide band on the car and see how things look. I would put two bungs on the exhaust (one passenger and one driver) so you can see what each bank is doing. Will require swapping the sensor from side to side but all the work you have done to date swapping them would be nothing.

 

[Noobz347]

Run those new set of plugs for a tank of gas and do your usual calculation to see where you're at.

You'll get a better read on the plugs too.


Wow... The length comparison in your image makes them look really long.