Autometer = Ecometer? Yep, It Really is This Bad

[cjforumadmin]

http://www.bangshift.com/blog/Autometer-Ecometer-Yep-It-Really-is-This-Bad.html

[Scott Liggett]

Re: Autometer = Ecometer? Yep, It Really is This Bad

MY 65 Impala has a 60's version straight from the factory. That vacuum gauge to show you how much you are pushing the big peddle against the floorboard.

[TheSilverBuick]

Re: Autometer = Ecometer? Yep, It Really is This Bad

The big question is how does it calculate it? Map sensor and speed? or using actual fuel amounts that pass through the injector?

I'm with Rebeldryver on the vacuum gauge thing, I run them in my cars for at least a while. Though my Skylark's mileage versus vacuum pulled currently has me a bit confused.

[SpiderGearsMan]

Re: Autometer = Ecometer? Yep, It Really is This Bad

gas @ 2.17 a gallon this morning
cut the gas tax and let the people live ! you DC frauds ! none of it fixes the roads anyway
you hear about the congressional gas pump in the capitol parking garage ? NO CHARGE

[squirrel]

Re: Autometer = Ecometer? Yep, It Really is This Bad

Though my Skylark's mileage versus vacuum pulled currently has me a bit confused.

As well it should

Do you get less vacuum, but better mileage, in overdrive?

[Scott Liggett]

Re: Autometer = Ecometer? Yep, It Really is This Bad

gas @ 2.17 a gallon this morning
cut the gas tax and let the people live ! you DC frauds ! none of it fixes the roads anyway
you hear about the congressional gas pump in the capitol parking garage ? NO CHARGE

No different than the one in Cali State Capital garage. Hell, the state assembly and senators each get two free cars we tax payers take care of. Easy to spot too. Assembly has an 'A' then two numbers, Senators have an 'S' then two numbers.

[TheSilverBuick]

Re: Autometer = Ecometer? Yep, It Really is This Bad

Though my Skylark's mileage versus vacuum pulled currently has me a bit confused.

As well it should

Do you get less vacuum, but better mileage, in overdrive?

No, that's what has me confused. This cam pulls a TON of vacuum. With the Centurion engine I was pulling 10-12 inHg in OD and got 23mpg consistently, this engine with more compression and pulling 12-15inHg consistently got 17mpg. It pulls a ton of vacuum at idle too despite a slight chop to the idle. There are three things I'm considering plausible causes. First is I did swap rear gears from 3.23's to 3.70's. But I tried even driving at slower speeds to cruise at similar rpm (which would equate to less wind resistance too....) and still netted 17mpg. The other thing I'm considering is the extra vacuum is just simply sucking more fuel though the not even tuned to this engine Q-jet, same Q-jet netted me 23mpg with the other engine. Then lastly the exhaust duration on this cam. It might just have a really good intake lobe sucking a bunch of fuel in and pissing it all out the exhaust while still showing good intake vacuum, but the plugs always look good (even before the MSD box) and I don't ever see smoke out the tail pipes. I really really need to get my MS set right so I can get some good readings on the O2 sensor to see if this is the case. I'll be chronicling the various testing on the Project thread when I get around to working on the Skylark again. For now I've been just enjoying driving it 8)

[38P]

Re: Autometer = Ecometer? Yep, It Really is This Bad

Hopefully it's not as annoying as the Ford/Lincoln/Mercury factory system.

The problems with the FoMoCo system are: (1) instantaneous fuel economy varies wildly (from 1 m.p.g. at full throttle to 50+m.p.g. when coasting), (2) average fuel economy is over a whole tankful instead of a trip or a rolling average (e.g. the last 10 minutes of driving), (3) sometimes the vehicle still runs when the computer says range to empty is zero.

On the other hand, when that meter says you're getting 5 m.p.g. (even if you know that you'll get 50+ coasting down the other side of the hill) you do have a tendency to lift off.

A better design for a meter would display instantaneous m.p.g., trip average m.p.g. (resets at key off) , and tank average m.p.g. at the same time (with lifetime average available upon demand).

BTW, a vacuum gauge is good only for relative m.p.g. comparisons on the same vehicle. A big vehicle using tall gears, a small engine and low vacuum readings can sometimes score higher m.p.g. than a similar vehicle with a larger engine, lower gears, and high vacuum readings.

Why? Reduced pumping losses and a higher effective compression ratio.

[Scott Liggett]

Re: Autometer = Ecometer? Yep, It Really is This Bad

Since our fleet cars, Lincoln Towncars, spend hours idling. It's hard to say exactly what mpg those cars are getting. The models we buy also have an idle meter which explains whose letting the cars sit and run for days on end. Though, if the car is getting less than 15 mpg overall, it's pretty obvious.

Randal, your issue may be that the rpm your cruising at in the Skylark isn't where the engine combo is most efficient. I get better mpg at 80 plus than cruising at 70 mph in the Impala. You've obvoiusly found the best cruising speed for efficiency in the Centurian, as 23 mpg is fantastic for that car.

[squirrel]

Re: Autometer = Ecometer? Yep, It Really is This Bad

With the Centurion engine I was pulling 10-12 inHg in OD and got 23mpg consistently, this engine with more compression and pulling 12-15inHg consistently got 17mpg. It pulls a ton of vacuum at idle too despite a slight chop to the idle. There are three things I'm considering plausible causes. First is I did swap rear gears from 3.23's to 3.70's.

Let's see here....

Old engine, 10-12 in, 23 mpg, 3.23 gears
New engine, 12-15 in, 17 mpg, 3.70 gears

So, if I understand correctly, you are now getting worse mileage, more vacuum, and you have a steeper final gear ratio.

Like I said....

[TheSilverBuick]

Re: Autometer = Ecometer? Yep, It Really is This Bad

With the Centurion engine I was pulling 10-12 inHg in OD and got 23mpg consistently, this engine with more compression and pulling 12-15inHg consistently got 17mpg. It pulls a ton of vacuum at idle too despite a slight chop to the idle. There are three things I'm considering plausible causes. First is I did swap rear gears from 3.23's to 3.70's.

Let's see here....

Old engine, 10-12 in, 23 mpg, 3.23 gears
New engine, 12-15 in, 17 mpg, 3.70 gears

So, if I understand correctly, you are now getting worse mileage, more vacuum, and you have a steeper final gear ratio.

Like I said...

I think it's easy to point fingers at the gear ratio, it was my first gut reaction too, but I honestly think there is more to the story than that, 500 rpm difference in cruising, which then I slowed down 500rpm over 500 miles still netted me the same mileage made me think less of it being an rpm issue. It got 17mpg +/- .5mpg rather I cruised at 65mph or at 85mph. I know the extra rpm would make it pull extra vacuum, but it pulls extra vacuum at the same rpm (2000 vs. 2500) than the Centurion's engine did.

Scott, the Centurion gets 15mpg highway. When the Centurion's engine was in the Skylark it got 23mpg and loaded the engine up in 5th under 70mph. My old Firebird with 700r4 and 2.73 gears got better mileage at 80mph than 65mph as it was a sweet spot for the engine. The Skylark's current engine doesn't seem to nose over anywhere above 1200rpm. I might go back to 3.23 gears... or such, but I'm not going to start experimenting with gears until I get the EFI tuned up and I know the engine is running lean while cruising.

[squirrel]

Re: Autometer = Ecometer? Yep, It Really is This Bad

heh....it's fun to try to explain this....

Randal, think about it in terms of throttle opening. The further open the throttle is, the more efficient the engine is.

[TheSilverBuick]

Re: Autometer = Ecometer? Yep, It Really is This Bad

heh....it's fun to try to explain this....

Randal, think about it in terms of throttle opening. The further open the throttle is, the more efficient the engine is.

I've actually considered this as a way to minimize pumping losses. I was actually "Hoping" that the cam I chose would have less vacuum due to the long duration. The same time I would think the higher speed/engine rpm would require more throttle openning. Neither has panned out for me so far, but I have more testing to do.

[squirrel]

Re: Autometer = Ecometer? Yep, It Really is This Bad

If you're looking for efficiency, then you want to pick a cam that has the right timing for maximum cylinder pressure at the rpm you want it to be efficient at...instead of running rough because it has too much overlap...right?

For a given car speed, gearing the engine to run slower will require more throttle opening, so the engine will run more efficiently (mostly). It increases the load on the engine. You're going the wrong way, decreasing the load and increasing rpm, so that the engine is using a higher percentage of the power it makes just to overcome it's internal friction (pumping loss)

[TheSilverBuick]

Re: Autometer = Ecometer? Yep, It Really is This Bad

I picked a cam with almost no overlap. It was a risky venture I'm not willing to say was wrong until I know I have the fuel and timing right. If I conclude the cam is wrong I'm going to get the small one from DF's and Chad's Carcraft article ;D

The gears were cheap and came with the carrier, so those were a matter of convience and not the ideal set I was going for. I was/am aiming for 3.42's to go with the .64 OD.

I'm targeting 2,000rpm for cruising to guarentee I have sufficient oil pressure when the engine is loaded up climbing hills in OD. 3.42 gears would get me that and load the engine up a bit more. The 3.23's loaded the engine up too much I think (at least the Centurion's engine) as anything under 70mph the rpm's were too low for my liking (and with this engine I'd probably have to worry about pinging).