Back tracking so you know my situation.

I installed LT headers, ran them without pipe or anything for about 2 months.

Now I just finished piping it in, but I do not have my o2 sensors in, because they simply won't fit, I will have to bend them or try to find compact ones or some sort, but I'll worry about that later.

My question is, where does the tach get it's MPG readings from? My tach is saying I'm getting 11mpg, while my Gryphon programmer is saying I'm getting 16.4!!!

So which is correct? I know, I know, I need to fill up, and run it out, and fill up again to find out, which I plan on doing. But I still have half a tank left, and I need to empty it since I am going other maintaince to the truck and need to pour fuel injector cleaner, and whatever else.

So, all in all, is the tach getting readings from o2 sensor? or where? Also, where would the programmer be getting readings from? Thanks for the help guys!

 

I guess I got everyone stumped on that one? lol

 

A tach displays RPM not fuel mileage ?? yeah you got me stumped...

 

Oops, sorry. Meant the instrument cluster

 

Don't trust the Gryphon or instrument cluster. Do it the old fashion way for MPG. The ecm guesstimates from its data what the mileage might be. Don't forget to adjust the tuner for tire size if they are not the stock size.

You will need a custom tune to get the reported 30hp/35 tq gains. It wont be an issue if you run without a custom tune for emissions. I think they are like $50 for the custom tune, not 100% sure. You don't have to return the ecm program to stock, the dmv only checks for trouble codes (at least in Wi). You have an 05 so Im pretty sure you only have 2 cats. Magnaflow 94106 are the high flow cats Measure the header exhaust end for size to choose the right one (prob. 3") O2 bung already in them. Have them welded to the header? Or did the LT's come in a kit with the cats already there? The cats (94106) will go exactly where your OEMs were. You may need an O2 extension like you said. No clue about "smaller" ones.

 

(2004 Lariat) I have a custom tune with the Gryphon. The OBX headers came with the o2 bungs on it, and the driver side is hitting some lever, I am guessing the e-brake line maybe? The passenger will be fine, I just need to splice the wires to make an extension. Also, yes I do have the magnaflo hi-flow cats, and it is welded to the headers, mechanic said they could not bolt on =(

Thanks for the info 08, was hoping that one or the other would be pretty close, within 1mpg, of what my actual is. I filled up yesterday, when I get to 100 miles I think I will fill up again and see what the actual mileage is, because there sure is a big difference between them.

 

My wifes mpg rating on the cluster is close but no cigar. Mostly higher mileage displayed on the cluster than actual. Sorry, it is so much easier the other way.
She doesn't care for MY numbers. I did graduate and passed all of my math courses.

 

Well, just filled back up. Gryphon read 16.3mpg. Dashboard read 10.7
Actual was 10.0

Guess I need to get those o2 sensors on quick. Saw today that they make a 90 degree angle fitting for them.

 

It gives you the rating from calculating metered fuel consumption from the injectors and vehicle speed sensor

 

I'd be a little concerned about only getting 10 mpg's. If not having the o2 sensors is causing that, I'd get them in immediately. Otherwise you're just throwing money away with your mileage. Good luck. Let us know if the o2 sensors do the trick.