MPG Run #6

[TominMO]

Today I did a run with timing advanced, but there're some catches.

Yesterday I cleaned off the distributor cap contact points, which were quite corroded. This cured a misfire I was getting from time to time. Then I advanced the timing, but I don't know exactly by how much. I was unable to find the pulley timing mark, so I just did it by "feel". There was actually very little room left to advance it, so I just cranked it clockwise (since the disty runs counterclockwise) as far as it would go. I estimate this was only about 4 degrees of extra advance, just based on experience with other cars. I would have preferred 6 or 8 degrees of advance. I am running premium gas to prevent detonation with advance, and intend to keep it advanced.

Today it seemed to run smoother, probably due to the combination of advance and cleaning the contacts. Air temp was like yesterday, high 50s; breeze almost nonexistent.

Mileage came to 52.1. Yesterday it was 50.5, for an improvement of 1.6 MPG. I am getting the impression that 55 MPH is a much better speed to run it at for economy than 60. At 55 MPH I have gotten 58.5 MPG. You wouldn't think 5 MPH would matter so much, but the data seems to suggest that.

My tests are not as rigorously scientific as I would like, but at least we have something stronger to go on than anecdotal evidence. Your mileage may vary.

This run was going to be with the car waxed, but I didn't get around to that, so I did the ignition advance test instead.

Next test will be with the car waxed; I will also do a test with heavier 14" tires/rims, and a city-street hypermiling MPG test, before I put on the 14" rims.

[JPT]

Did you notice that your engine doesn't like high revs with advanced timing as much as with stock timing? Mine seemed to rev better when the timing was stock.

I'm keeping mine advanced. I get about 2 MPG more and better low end and throttle response. I just shift a little earlier.

[TominMO]

Did you notice that your engine doesn't like high revs with advanced timing as much as with stock timing? Mine seemed to rev better when the timing was stock.

I'm keeping mine advanced. I get about 2 MPG more and better low end and throttle response. I just shift a little earlier.

I haven't driven it with high RPMs yet, since I advanced the timing, which was just last night; just did a mileage run this morning and am now in the middle of doing a city-street hypermiling run. I'll check out the high revs after this run.

[TominMO]

Follow-up: with the timing advanced, it feels like it runs quite strong all the way up the RPM range to redline, so I'm keeping it that way. I don't mind paying a little more for premium to get this performance boost.

[festyxfi]

I've been staying at 60mph on recent long trips up to the U.P. of michigan in my tired (230K) 89 carbed 5-spd and only able to pull 45mpg. I'm very impressed with your results. I once was able to get 50MPG by keeping it at 50MPH, but carbie is tired (and carbed) a fresh EFI will blow those #'s away.

Thanks for continuing to share your findings.

FX

[TominMO]

I've been staying at 60mph on recent long trips up to the U.P. of michigan in my tired (230K) 89 carbed 5-spd and only able to pull 45mpg. I'm very impressed with your results. I once was able to get 50MPG by keeping it at 50MPH, but carbie is tired (and carbed) a fresh EFI will blow those #'s away.

Thanks for continuing to share your findings.

FX

If you plan on keeping that car for awhile, stick a Weber DGEV 32/36 on it. More power and better mileage as well. Virtually turns it into an EFI car, but with a much cleaner engine bay.

[festyxfi]

Okay Tom.

[Banana Bonanza]

For a 230K mile engine, 45mpg is pretty darn good. I wouldnt complain too much if its running good. I will say if the feedback carb gives you actual drivability problems, I think the weber or carter-weber is way to go. Thats assuming you dont have yearly emission nazi visual test where you live. And it sure cleans up the engine compartment eliminating the bushel basket full of hoses and various little electronic gizmos. I can actually change oil filter from above now instead of putting car up on jack stands and crawling underneath. Course part of that new room to get easy oil filter access is the B6 carb manifold is offset bit more towards driver side than the B3 manifold.

[TominMO]

Some people have disguised their Weber for visual inspection purposes by temporarily sticking on a stock air filter housing, and some extra hoses as desired to create the stock effect.