Cylinder Deactivation

[johnunit]

You can easily get high 20's on the highway out of these cars, even in stock form.

yeah, my worst-case-scenario of an early front end, carbed 351w car still gets 23+mpg driven reasonably on the highway.

[gadget73]

heh, I've never hit 19 with my car. 18.5 is about as good as it gets. 17.5 is more typical. With the stock engine, it topped out at 14.5 mpg. Its not just my driving either. The Mark VII pulls down 21-22 on the highway with no problems. I've gotten over 20 driving Scott's car too. He can't do that with my car though.

[OilBurner]

I remember when i first got my car it got 14. then when i inflated the tires properly it jumped up to 17-18. I may have actually observed 20 more recently...but i dont really remember. I have synthetic gear lube in the rear end and i believe i have the 2.7x ratio.

[sxcpotatoes]

2.78 rear end, excellent highway mileage, not too pleasing on the butt-dyno. Yeah, 4.6s are fuel-sippers, '98-02 may be the best ever. Before the original intake started to go on my '99 (with 233k) Grand Marquis, I was routinely getting 32.5mpg on the digital dash running at 62mph cruise control (60 radar-sign-thingy-observed speed). Mileage went down on the '03+ cars due to them being heavier or whatever. My '03 ultimate only seems to do 28.5ish on summer gas. Same as my '90 Towncar with the 5.0, actually, but they ARE 3.55s in the Ultimate, forget at the moment what gears are in the TC.

[johnunit]

I remember when i first got my car it got 14. then when i inflated the tires properly it jumped up to 17-18. I may have actually observed 20 more recently...but i dont really remember. I have synthetic gear lube in the rear end and i believe i have the 2.7x ratio.

What pressures are you running? I've found minimal ride issues right up to 44psi (sidewall max on my tires).

[sly]

35 all around on mine (cept the Mark... 40 front/35 rear... apparently the front is that much heavier).

[OilBurner]

I filled mine up to slightly past max...forget if it was 34 or 44...but i probably did 35 or 45 only because its a more mentally-satisfying number...when i got the car they were very low...not low enough to be a problem but bulging out at the bottom low.

[gadget73]

I run 40 in mine usually. I put it up to 44 (max on the sidewall) if I'm doing a long highway run but the extra 4 psi on the beat up roads is not as pleasant. I run 35 locally in the Mark VII for the same reason. With the poly bushings, that thing just beats the hell out of you if its any higher. The Towncar is still smooth with the poly. Damn crappy Fox suspension.

[OilBurner]

Ok so the original idea behind this thread i have basically decided to scrap for now... However i did come up with a fail safe solution that will not interfere with the electronics...custom headers! basically separate all the cylinders into groups of 2, dependent on firing order, and move the oxygen sensors so that they are only monitoring the exhaust stream of the 4 (2 on each side) cylinders that would be running all the time (in both 4 and 8 cylinder mode)...this would make it so the exhaust gas ratio would not change at all when cylinders are switched off, and would still allow the ECU to do its monitor/adjust thing in real time as normal...additional sensors could also be added so that both sets of 4 cylinders could be switched on or off without having a "primary" set...the additional sensors would just be switched so that whatever cylinders are being used would be the ones that are being monitored...this could be manually controlled, or automated so that the 2 groups of 4 cylinders are switched on or off every so often and used an equal amount of time to avoid hot spots and whatnot...

This all requires more modification than i have time for right now, so until then, I just got the car back from having a dual exhaust installed. 2" from the cats back with knock-off flowmaster 40 series. Cost $280. Will be advancing the timing and also switching to synthetic oil in the next week or so..and doing the stereo and repacking the passenger side wheel bearing...and then i will be embarking on my cross country drive to California from PA. any other thoughts or opinions on things i should do to the car before i take it on this long trip are welcome.