Need opinions (I know you've got one! ).

[Anonymous]

My goal is 20 MPG at 6000 feet altitude. This mini-forum should be restricted to engine-only ideas, please, as I've already rebuilt the trans, differential, driveline, etc., etc. and am using the special low-friction additives, and so on....besides, y'all have Mustangs and I have a lowly Fairmont waggin' for my puppy dogs...

If I can't reach 20 MPG with conventional carbing, I'll have to knuckle under (down under?) to Execute's plan and go EFI, so try hard, guys... that will be a lot of work! (to xe).

OK, here's what I've done so far -
1. Full rebuild, .040" bore, 7cc piston dish.
2. FoMoCo original, but new, cam/rocker shaft/lifters/rockers.
3. New FoMoCo Holley 1946 carb (stock unit).
4. Autolite sparkplugs - the SplitFire and Bosch ones are already out of the contest as they failed muster.
5. I ported the intakes on cylinders 1,2,5 and 6 to help even out the flow at the ends of the intake log.
6. Added the Cliffy port divider.
7. Milled the head .010" and installed the FoMoCo steel head gasket. This made the CR 8.65:1 on the lowest and 8.80:1 on the highest cylinder, due to the imperfections in the cylinder head. I smoothed out the head around the sparkplug bosses and the valves to help the flow along, but the CC results still were surprisingly widespread.
8. Static spark advance has been varied thru 10-11-12 degrees so far. Mechanical advance in the distributor is 26 (crank) degrees, at 1800 RPM.
9. Distributor advance is on port vacuum (like you Mustang guys have already).
10. EGR disconnected for this test.

I'm using the exact same driving plan every day, to & from work. It's very consistent. So far, the improvements have taken it from 12 MPG (average low) up to 16.5 MPG (average low). I'm staying with the 'average low' number to satisfy my pessimistic engineering bent.

What would you try next?

 

[DaveLS]

MarkP,

Ideas that would not reduce performance - and rational,

1. Headers - general improvement in effency
2. High Energy Ignition - general improvement in effency and possibly lower idle RPM
3. Adjust deck height to achieve 0.040 deck clearance (your steel head gasket may already be doing this. - improved combustion chamber turbulence - fuel air mixing - better burn
4. Distributor with mechanical as well as vacum advance, Possibly a Duraspark II. - insures full advance and reduces dependance on vacume
5. Check jetting and choke - goes to best fuel air ratio
6. 190 thermostat - increased temp increases effency
7. K & N air filter - ? if this would really help
8. Check timing mark to insure that it corresponds to TDC of cyl 1. Some harmonic ballances have been reported to have shifted. You could also set timing based on highest idle vacume, instead of timing marks.
9. Roller rockers - may not help but is cool
10. T5 trans -You didn't specify your trans but I am assuming it is an automatic because of your mileage figures. Also, I know you said engine only but this would probably make the biggest difference.

I wonder how much your 6000 foot elevation is effecting your mpg, especially in the summer. The stock factory jetting is (?) set on the rich side for sea level. Assuming this is true, the stock jetting should be significantly too rich at your altitude. If the car is staying this high then changing the jets might be something to look into. If you take the car to lower elevations this leaner jetting could result in possible problems.

These are just ideas. We have not tested any of them. Currently we are just trying to get things to work. Soon we will start the tuning process. For reference, we get about 20 mpg around town running 87 octane, an OZ head, headers, 4v Holley, stock cam, standard ignition, 12 deg advance, vacume and mechanical advance, t5, 3:20 rear, small tires, and stripped interior.

I would start with the air filter, headers and ignition and then proceed to the carburation tuning. In this order you get improved performance in the name of economy and do not have to tune again when the headers are added.

I would like to know how this works.

Regards, Dave[/i]

 

[Anonymous]

Gear Vendors unit if you have a C4, the OD will help a lot.

 

[addo]

Did you dial the cam and note its actual specs?

I feel concerned about a couple of other things. Bore shape (was it torque plate honed), and final CR (IMO, a shade on the low side). Headers might add ½MPG, so they would take a while to pay for themselves. Engines seem to run quieter with them; maybe less phase cancellation and hence less "rough"?

Adam.

 

[CobraSix]

HEre is what I would do (it's what I did).

1) High energy coil (40,000 Volts) like the flamethrower. With that you can open your spark plug gap by about .005 over stock gap of .035 (I think that's stock). That will give you about a 1-2 MPG difference.

2) Are you running pertronix or DS2? I didn't see it listed. Try one of them. YOu'll be able to open your gap up a little more (.005 or so). It will also smooth out your engine running. Plrobably another 1MPG increase.

3) Look at getting an MSD CD ignition. Any of the 6 series ignitions will work great. Which one you go with is a matter of how much money you have to spend. I went with the Digital 6+ for a few reasons, but the MSD 6A and 6AL are great additions. With that, you should be able to open plug gap an addition .010". That will give you about a 2-3MPG increase.

Those are the number I experienced as I added those components. THe entire system I describe should give you about a 4-5MPG increase in mileage that you are looking for.

Slade

 

[Anonymous]

I agree with addo that your compression ratio is too low. At 6000' on a standard day, your effective CR is only about 80% of sea level. So if your average static CR is 8.7, at 6000' it is equivilent to about 7.25 at sea level. You can play around with the numbers here.

I suggest raising your CR to about 10:1 static.[/url]

 

[CZLN6]

Howdy MarkP and All:

What a great criterion reference to determine progress. I'm thinking you have several factors limiting improved MPG. Some can be tuned away and/or compensated for while others will require a physical change. 1st is CR. Several have identified this as being too low for optium efficiency at the stated elevation. For maximum mileage, 8.8:1 is too low for this engine, even for a sea level situation. 2nd is the retarded cam timing used to detune, lower torque range and improve emissions on Fairmont era 3.3 sixes. Straight up cam timing gear set would improve MPG effiency. 3rd is the #1946 Holley carb. I'm of the opinion that it is too incumbered with emission goals and restrictions to be a good mixer. 4th would be the stock exhaust system.

What to do, short of a major rebuild to maximize quench, add CR and solve the cam timing problem?

Thermal efficiency- The goal here is to keep heat (aka energy) in the engine, but provide cold air for intake. Add a 190 degree thermostat for quick engine warm up and running. Avoid cold starts and idling. For cold morning starts, plug in your engine heater, start up and drive away. It will warm up quicker under driving load than idling. Your Fairmont has a fairly good air cleaner fresh air intake system. Use some duct wrap to insulate it from heat sources. This compensates for high elevation and low CR.

Ignition- Use as much initial advance as you can. At your elevation and CR, I'm guessing that you should be able to use 14 to 16 degrees of initial without knock. Advance it til it knocks, then back off slightly. I'm sure you've already maximized your plug gap and such. A hotter coil and/or MSD module would help some, but on the DSII it is hard to show much improvement. This compensates for late cam timing, elevation and CR.

Carburetion- Reduce choke function to the absolute minimum. Lower float level slightly below recommended settings. Lower idle speed to barely running. Lean out the low speed air screw. If you've ever thought of converting to a Holley/Weber two stage two barrel, this may be the time.

I know you're limited as to what you can do by the Colorado air sniffers, but a larger diameter, more effieient, single exhaust system would help, I'm sure.

All that being said, in MPG trials, the driver is still the biggest variable.

Well MarkP, what do you think? What's your next move? Let us know.

Adios, David

 

[xzerokidx]

My $.02, start lightening the load. that would be the first step towards better fuel efficiancy and for the most part its free (unless you want to start swapping to fiberglass).

 

[Anonymous]

Boy, it's great having a private brain trust!

Well, here's what I'll start with:
1. Find a high-energy coil that works with the DII ignition. Anybody had long-term (like over 40,000 miles) experience with any of the high-voltage ones?
2. Changing that DII to the Yellow Grommet edition.
3. Try to find some Holley jets for the 1946 (until I can get past the 25-year emission limits next year and go into the H/W 2-stage, which is where my heart is, anyway).
4. Play with the plug gaps after 1 & 2 above.
5. Replace the catalytic with a "high-flow" cat, if I can find one. (I'm stuck with that baby, around here. The gendarmes of emission are getting testy because Denver's back on the 'bad air' list and losing federal funds again).
6. Find a 190 t'stat for it: this will necessitate installing the hood louvers, though, because the cat-equipped 3.3 engines generate enormous heat soak at 180 degrees, worse yet at 190+.
7. - Play with the 36 degree dizzy setting. When I advance the static much past the current 12 degrees, it becomes very hard to start, especially hot. The 36 degree setting would allow lower initials, with the full 36 still available, along with the "higher average" I'll get from the Yellow Grommet unit. I'll probably have to find lighter springs, though.

Things I've already done (as suggested by some of youse guys);
- Checked the TDC mark (when I rebuilt it all).
- Narrowed the quench with the steel head gasket: I'd like less, but can't re-rebuild just to get it. It's at a little over .040" now.
- Checked the cam on installation: it is 1 degree late with stock gears.
- Improved the air filter. I'm studying ways to generate a ram-air: I'd like to put a NACA duct into the eyebrow over the passenger-side headlight when I get ready for the re-paint job this Spring. It has a good cold-air system now.

I have the idle at 550 with A/C on, which seems to be as low as I can reliably go without surprise stalling in the summer.

Headers are out of the equation, since the catalytic makes them useless. They'd never fit, anyway, with the EGR and AIR piping already filling up that whole area. I've been busted twice for having that stuff missing (when I bought the car that way!), so I don't want to go through that expensive game again.

Keep any new ideas coming: I'll keep posting the results as I go.

Addo: it was torque plate bored, but I wasn't there for the honing, so I'm not sure about that step. I couldn't measure any out-of-round when I got it back, so I felt pretty good about having round holes, at least. I started out for a .030" bore, but the front cylinder was leaning toward the water pump so much that we had to go .040" over just to get straight holes!

 

[BKNLINE]

Hi Mark,

Yes, if you are running with the original catyletic converter trash it! Replace it with an aftermarket performance cat readily available at any muffler or speed shop. I think Jegs and Summit Racing sells them too. I have a '78 Farimont wagon (and also a Friggin' Futura) - both V8s and I replace the original, cruddy-very-restrictive-inefficient factory cat with an aftermarket unit. My wagon before I did any emissions work to it failed California's Smog check II and was labled a Gross Polluter. Fortunately, that was a pretest. I re-installed all the stuff the previous owner had removed and had a new cat installed and the wagon passed so well it met 2001 standards for HC and CO ( about 50 ppm too high to pass 2001 NOx spec).

Both V8s are averaging around 15 mpg and are near stock configuration.

I also recommend an MSD or you might try Jacob's Electronics Mileage Master ignition computer. On my '65 I6 Mustang long ago it gained 2 mpg and 8 mph at the top end.
That was with their coil and opening the plug gap to 0.050.

I think on your Fairmont with the DS II your plug gap is either 0.045 or 0.062 if it's Calif. spec (or maybe that's V8 only) but with an MSD or Jacobs you might be able to open you gap up a bit more

I almost thought about lowering the car also but I seem to recall that has some negative effects on the Fox chassis if not done right.

Hope that helps,

Dean T

 

[CobraSix]

I've put 20,000 miles on my Flamethrower coil from pertronix in the last 2 years. Still working great.

Slade

 

[Asa]

- Improved the air filter. I'm studying ways to generate a ram-air: I'd like to put a NACA duct into the eyebrow over the passenger-side headlight when I get ready for the re-paint job this Spring. It has a good cold-air system now.

i'd suggest visiting Mustang Geezer's site

look at his CAI setup, very purdy, very functional

 

[80broncoman]

I know a man around here who wanted a little more MPG and a little less speed out of his pizza delivery chevettes. I told him simple way is to put 1 1/2 inch block of wood on the underside of the gas pedal. same top speed just takes longer to get there.
Jim

 

[Anonymous]

Thanks for all the ideas!

Slade: It has the DSII system already, plug gaps at .050" stock. Does your Flamethrower run in the DSII system, or is it running on points? Reason I ask, there is a current limit (and ESD backlash limit) in the DS units, which will be higher with a higher-voltage coil. I don't want to overdo with the DS stuff.

BKNLINE: Thanks for the brand name tips on the cat. My present cat has 198,000 miles on it and there is too much back pressure, probably because the guy before me removed the AIR system that helps the cat burn itself clean. On this particular engine (1979), the AIR is the type that loses no HP because there's no air pump: it has a check valve, muffler and a series of hoses and pipes that enter the exhaust manifold at dead center above cylinders 3 & 4, where the pulsing vacuum pulls air into the manifold from the air cleaner (thru all the piping). It moves enough air to be better than the earlier (pre-1978) systems, but it's a LOT of EXPENSIVE pieces (over $200 to replace it all).

 

[CobraSix]

I'm running the flamethrower on DS2 with no problems so far (though only about 5000 miles on that set up).

198k on you cats? I bet that's the problem. They are probably stopped up.

Slade

 

[Anonymous]

Yep, it is (there's only one). The manifold pressure is high enough lately that it blew out the plug where I had stopped the leak from the old choke heater. That choke heater tube corroded away years ago from the MTBE gas additive the politicians made us use ("oxygenated fuel", they called it - now they use gasahol instead, so it ruins the fuel pump diaphragms and o-rings in the carbs).

As soon as I get a warm day, I'm going to tap that hole and put a plug into it so I can directly measure the pressure in the exhaust. In Colorado Front Range, muffler shops are not allowed (by law) to replace a catalytic converter until the exhaust pressure reaches "high pressure", which the shop I deal with says is over 4 PSI. That's a LOT of back pressure, in my experience.

 

[Asa]

what happens if "a rock" punctures the housing of the cat?
wouldn't they have to do the work then?

 

[StrangeRanger]

Federal law says a cat must be damaged, defective or have over 50K miles on it before it can be replaced. I personally have brought 2 cats into compliance with the law I recommend a sharp chisel and a BFH.

 

[Anonymous]

I have some scrap iron with sharp edges. Hmm...

 

[66200i6]

This is a huge subject so the following is just addressing the issue of ignition and I will apologize up front for the length.

Start with the basics. Without spark your system is dead. I think the best upgrades to start with are good plugs (your running the best IMO, good hard alloy). Good low resistance, wire wrapped, carbon conductor, silicon plug wires, and a magnetic core high recovery coil.

Next, increase the amount of time your coil has to recover so it can deliver good spark by upgrading from the stock points. The favorites here are the second generation Igniter or the Dizzy II. This increases the accuracy of the signal to the coil, which in turn gives it that fraction of a second extra time it needs to recover for the next spark.

Next, is fuel metering. Upgrade to a progressive two-barrel to increase the velocity through the Primary venturi. The Weber 32/36 DFV is the way to go IMO. The primary venturi is on the left side of the carb body which when installed is closer to the firewall and in turn easier to adapt the throttle linkage. This DFV model is also easy to find because it has been used for years as an upgrade to the VW Type II Bug engine.

As far as adjusting/tuning of a healthy system, work with your plug gap. A good-sized spark kernel can only help. I am running .075 (the most I can get easily from a Autolite) with the Jacobs Mileage Master. With a healthy system (tuned regular), you can increase the gap easily another .006. With a good low resistance wire set you can add another .006. If you add a good high-recovery coil you can add .007. That takes your gap up to .054 from the stock .035 gap. Personally I never gap lower than .050.

On the other hand if you don't tune often you can start subtracting .004 gap. If you are going use all you’re new found power in that six most the time, you can subtract .010 gap.

Of course every system is different so experiment and find the best setting for your rig.

Ric.