Increasing efficiency, within reason? (long post)

Topic: Increasing efficiency, within reason? (long post) (Read 3961 times) previous topic - next topic

Re: Increasing efficiency, within reason? (long post)

Reply #15 – September 19, 2005, 03:37:44 PM

well the difference between 76 and 70 on the hwy for my cobalt has been about 4 mpg on average. so it does make a pretty big difference, at least in that 4 banger.

Re: Increasing efficiency, within reason? (long post)

Reply #16 – September 19, 2005, 03:49:23 PM

Quote from: Bird351

OK, so maybe I SHOULD ask about the 351 thing. Do you think that converting one to EFI but leaving it otherwise stock would get the Mark moving from a dead stop a little more efficiently vs. the 5.0 HO in it now? (my 351 is 210 horses as-is, carbed)

Short version: Moving up to a 351 is going to hurt your in-town gas mileage unless you regularly go WOT.

I can give you the long version if you want.

Re: Increasing efficiency, within reason? (long post)

Reply #17 – September 19, 2005, 05:26:38 PM

Speed makes a big difference in my T-Bird too - I got 33 MPG driving like a granny on a 60-mile trip, and I got 28 driving like I normally do on a 200 mile trip. The 33MPG trip was all back roads, so speeds rarely got over 70. The 28MPG trip was on open highway with speeds constantly in the 75-80 range.

Re: Increasing efficiency, within reason? (long post)

Reply #18 – September 19, 2005, 05:36:27 PM

Unfortunately it's not an option for highway driving here. Even at 74-75 mph I'm regularly passed like I'm standing still, and get passed (by people going more normal speeds) more than I pass others. Even the cops here will tell you flow of traffic is 5-10 over the limit, and that limit is 70 on rural Interstates down here. I will not go so slow that I increase my risk of having some idiot in an Excursion turn my LSC into a subcompact from behind.

At any rate, even at 75 with the cruise on, I'm still getting what the EPA rating suggests for the car. I can't complain about that mileage much.

Re: Increasing efficiency, within reason? (long post)

Reply #19 – September 19, 2005, 11:48:37 PM

The LSC's have the 3.27 gear for a reason... Better performance AND fuel economy. Whaattt? you say... Yep The HO engines peak efficiency is 300-400 rpms higher than the SO(this is due mainly to the camshaft). You go stickin' 2.73s in it, and my bet is you'll actually loose milage. But you say the Mustangs had HOs and 2.73 gears. Yea and they are 800-900lbs lighter as well, so the engine isn't working as hard to cruse the same speed. The 351 probably won't do any better on the highway, and will only suck more gas in town, so don't even think about it(My 5.8 Lightning is a real gas hog).

If you really want more MPG, swap in a SO 5.0(or 2v mod motor[shudder]) and then go with the 2.73s. Otherwise use synthetics, keep it in tune, the tires pumped up and don't worry about it.

One thing thhat will help is to install a vacspooge gage and drive by it... The higher you keep the vac, the better the fuel economy.

Me, I just ordered some new race tires......

Re: Increasing efficiency, within reason? (long post)

Reply #20 – September 19, 2005, 11:49:58 PM

Someone made a comment that a bump in the timing would require a higher octane fuel...such is not the case on these HO engines. We drove my T-bird around at 25 degrees BASE on 87 octane just for the hell of it...but that was before it was my t-bird and it still had to SO...After I put the HO in, I ran the base timing at 14 degrees. The timing pointer decided to disappear on my way to the track and I proceeded to advance the timing even more so, probably in the area of 5 degrees. I have no problems at any engine speed or load. Very rarely will I put anything higher than 87 in my car.

Re: Increasing efficiency, within reason? (long post)

Reply #21 – September 20, 2005, 01:32:27 AM

The idea wasn't just to swap 2.73s in, but to put in a 4R70W (an AOD-E w/ a wide-ratio gear set, for anyone else following along who doesn't keep up on slushboxes much) along with it.

http://www.becontrols.com/tech/ch3aodeupgrade.htm

Quote from: Baumann

To determine the "effective" first-gear-ratio improvement derived from using the wide ratio gear-set in a given application, simply multiply your rear axle ratio by 1.183 to obtain the equivalent standard gear-set axle ratio. In other words, a 3.27-1 axle ratio with a wide ratio gear-set will provide the equivalent of a 3.87-1 axle ratio with a standard ratio gear-set in first gear while providing identical ratios (and resultant cruise RPM’s) in third and only slightly different overdrive ratios. Essentially, the wide ratio kit makes your vehicle act as if it has a lower (higher numerically) axle ratio for maximum acceleration without sacrificing fuel mileage and increasing engine wear as a rear end gear swap would do. For most mild street vehicles, the wide ratio gear-set works best with a 3.27 or 3.55-1 rear axle ratio.

Either w/ or w/o the 3.27s, I still wouldn't mind going to a 4R70W.. it's supposedly much more durable than its AOD ancestor.. and can be had in the right bellhousing pattern. (and yes, I am aware it would not be inexpensive to do)

The pic I'm including is of the gear ratio calculator spreadsheet we whipped up some time ago, for when I had a strong desire to mess around with a gear splitter and alternate gearing. (hence the "Please ignore column B" statement.. that was the splitter's column) Whipped up those numbers using Baumann as a source, plus the FordMuscle RPM calculator and some random tire size calculator.

(I think it ran somewhere around 2200-2250 RPM on the gauge, at 75 MPH.. so it doesn't completely mesh with what the calculators tell me)

Re: Increasing efficiency, within reason? (long post)

Reply #22 – September 20, 2005, 02:25:16 AM

Quote from: Sick88Tbird

Someone made a comment that a bump in the timing would require a higher octane fuel...such is not the case on these HO engines. We drove my T-bird around at 25 degrees BASE on 87 octane just for the hell of it...but that was before it was my t-bird and it still had to SO...After I put the HO in, I ran the base timing at 14 degrees. The timing pointer decided to disappear on my way to the track and I proceeded to advance the timing even more so, probably in the area of 5 degrees. I have no problems at any engine speed or load. Very rarely will I put anything higher than 87 in my car.

Hmmm, that was me. In my experience, with my '85, too much timing advance gives great power results, but it pings real easily. I guess results vary based on mileage and engine condition.

Re: Increasing efficiency, within reason? (long post)

Reply #23 – September 20, 2005, 07:37:42 AM

Quote from: Thunder Chicken

Keep the A/C. It may burn some fuel, but most fuel economy experts will tell you that it takes less energy than it does to drive at 65+ MPH with the windows open. Aerodynamic drag is a big fuel burner. Around town, turn off the A/C and open the windows (likely not much of an option down there in Florida).

Not necessarily true. Although aerodynamics plays a pretty big role in efficiency, the a/c compressor will drag down the motor more than having your windows open will. I won't say I believe everything I see on TV, but on mythbusters, they tested the a/c versus open windows theory and the open windows lasted a lot longer than a/c. Given these were suvs, the results should be about the same for most cars unless they're super aerodynamic to begin with and rely completely on that factor to attain higher efficiencies. Since the test wasn't performed with fox cars, I cannot say with a great degree of accuracy that open windows will net you better mileage, but I don't see why it wouldn't.

Re: Increasing efficiency, within reason? (long post)

Reply #24 – September 20, 2005, 07:44:02 AM

My 88 XR7 with its almighty 3.08 and 235/60R15 will run down the interstate at 80 only running 2000rpm.

I wouldn't go with a 2.73 just because it would take so much more to get the car rolling from a stop.

Re: Increasing efficiency, within reason? (long post)

Reply #25 – September 20, 2005, 09:28:27 AM

The A/C is a keeper here. Especially since I can't roll down either window, now.

Re: Increasing efficiency, within reason? (long post)

Reply #26 – September 20, 2005, 09:30:52 AM

Quote from: Bird351

Especially since I can't roll down either window, now.

That must suck, whats wrong with them?

Re: Increasing efficiency, within reason? (long post)

Reply #27 – September 20, 2005, 10:20:16 AM

Quote from: Bird351

The idea wasn't just to swap 2.73s in, but to put in a 4R70W (an AOD-E w/ a wide-ratio gear set, for anyone else following along who doesn't keep up on slushboxes much) along with it.

A AOD can be built using the 4R70W gear set... As for swapping in a Electronic tranny, I'd use a 94-95 Mustang automatic EEC that can shift the tranny and operate a electric fan. The fan is something not mentioned that does help fuel economy.

Re: Increasing efficiency, within reason? (long post)

Reply #28 – September 20, 2005, 10:22:33 AM

Its not hard to get the car moving with 2:73's. I have two 5.0 cougars with then and a crown vic. Its not hard to make the car move. My 87 3.8 has higher gears, I forget what now. Its really not that much diffrent between 2,73's and a 3.08

Re: Increasing efficiency, within reason? (long post)

Reply #29 – September 20, 2005, 10:28:46 AM

Quote from: slamedcat

That must suck, whats wrong with them?

Passenger one hasn't worked since I got the car. Driver's side one went bad recently.. started sticking in the seals. I've tried pulling down on them while someone leans on the switch, tried spraying some silicone spray lube up into the seals, but it's a no-go. I have one more thing I'll try, but I'm not optimistic about it.

Since I may be working again starting later this week, I'll just replace the motors when I can afford to. We know the switches aren't the problem.. we've tested that before.