air fuel ratio.

[balldrick]

I have a wide band air fuel ratio meter on my car and wanted to ask someone what is ideal?It runs pretty rich 11 to 12 when you put your foot down which I think is good on a supercharged engine but when just touching the throttle cruizing it goes quite lean 14-15 and really lean when coasting down hills etc is this OK? and what is ideal for idle. Thanks.

 

[MPGmustang]

that sounds about right, boosted or not for just crusing you want 14-15 A/F ratio, I don't know at WOT for 11-12 but being boosted I would think it's safert o be a tad rich, for N/A engines @ WOT 12.3-12.7 is the ideal ratio. when you coast in gear it's okay to go lean as you are not trying to make any power this is what helps slow you down.

I would guess idle you want to be somewhere around 14-16... others will know better.

 

[Gene Fiore]

At idle you want somewhere between 13.5 to 14...cruising should be around 14.5. At WOT for a naturally aspirated situation ideal would be between 12.5 and 13.1...not sure for a supercharged motor but I would think it would be the same. Others may chime in on the supercharger situation.

 

[THE FRENCHTOWN FLYER]

Your figures sound close to perfect to me. Often times the A/F ratio at WOT needs to be closer to 11:1 to cover the leanest burning cylinders. Remember that fuel distribution is rarely even among all cylinders (not to mention air distribution (another reason to love EFI)) so extra fuel is needed to insure safe operation.

 

[turbo2256b]

I have been tuning with a wide band for 5 or 6 years now from bikes to cars injected / carbed. 40 years experance. WOT shoot for 12.7 to 13.2 in most cases. Carbed idle street usally 13 to 14 race might go up to 12.7 (better off line some setups). Lite loads / cruse 14.7 to 16 can be tollerated one has to figure a ballance of timing verses fuel metering and vehicles usage. Frenchy you have seen one of my cars in front of POEE.

 

[THE FRENCHTOWN FLYER]

WOT shoot for 12.7 to 13.2 in most cases. Carbed idle street usally 13 to 14 race might go up to 12.7 (better off line some setups). Lite loads / cruse 14.7 to 16 can be tollerated one has to figure a ballance of timing verses fuel metering and vehicles usage. .

Yup. That's about optimum. But I have done individual cylinder air/fuel measurement during air/fuel distribution testing on dyno that showed some manifolds needed 11:1 at WOT to cover a bad actor cylinder that was running lean. And I know some BBC manifolds require staggered jetting to also compensate for a wide range of A/F ratios.

POEE car shows? That was some time ago. With 40 yr experience you must be my contempoary. What were you showing at POEE?

 

[turbo2256b]

Not shure which car at the show thinking it was my blue 87 Grand Marquis 2 door.

Built a few BBCs mostly for boats. Found the issue was realy the cooling system. If one didnt tap the rear of the intake to bring 3/8 water lines to the front crossover the rear cylinders would run way to hot. Boats just run lines out the transom. Some changes to the water transfer hole between the head and gasket were needed too. One in the front left bank one in the rear right bank. Found the same issue in the SBFs but line dosent need to be but about 1/4 max. Lean condition was realy cooling issue. SBF also have issues with impeller cavity only half filling and need a bleeder installed. Many other engines have these same issues. After the rear to front water systems jetting squared up. In the case of the BBCs didnt toast as often.

300/240 Six had issues withthe front cyl being way to cool. Would braze in a piece of angle iron or rod behind the pump to split the flow.

Always check plug readings. Some fixes tried also were running different heat range plugs depending on distribution but cooling issues solved most of them.

 

[kevinl1058]

That's what I have. 13.9-14.1 at Idle.. Cruise 13.8-14.5 WOT 11.2-11.9 with my tri power setup..

 

[THE FRENCHTOWN FLYER]

Not shure which car at the show thinking it was my blue 87 Grand Marquis 2 door.

Built a few BBCs mostly for boats. Found the issue was realy the cooling system.

That's a good point. Another test we used to run was a magnesium borate heat distribution test, where a magnesium borate solution was used to "plate out" on the cooling system as a white coating. This was a destructive test as the block needed to be sawed apart to examine the hot spots. I seem to remember one bank of the SBF being hotter than the other. I've never done a MB test on a 300 but in most sixes that use a block mounted water pump the #1 cylinder is the coldest.

 

[turbo2256b]

I had about a 3" thick folder at my desk about cooling systems. Including the ones using MB. At one point realized old school cooling systems basicly from the begining were better than later days do to poor octane in fuel. As fuel improved cooling systems went down hill in general. Think MB was money waistful. Had about 8000.00 of temp sensores installed in a head. Because an engineer didnt know the differance between area and doubling the size of a drill .. melted down 2 heads on the dyno before the operator could set up base for the runs

 

[Anonymous]

I'd like to see that 3" folder! Has anybody put this information out where the poor dumb backyard engine builder can find it and modify/improve the coolant flow in an engine he is rebuilding? The only such info I've heard is that some engines, particularly the Chrysler Slant Six, give the builder a hard time getting all of the air out of the cooling system after rebuilding. Should we be modifying the water entry area when we rebuild our big and/or small Ford sixes when we have 'em apart, or augmenting coolant flow out of some areas? Sometimes we'll be informed about improving the oiling of certain engines, but nothing much is said about coolant, other than to use distilled water with roughly 50% anti-freeze/lube/anti-rust, and something like Water Wetter.

This puts me in mind of a small but oft-wondered-about point: Automotive thermostats used to have a little bleed hole in them, fifty years ago. Forty years ago, this hole gained a tiny check-ball. Thirty years ago the hole, with or without check-ball, seemed to disappear. Will you tell me about this?

 

[turbo2256b]

I forgot to grab up 2 boxes of folders when I retired. It was in one of them. I doubt the cooling system engineers had all the info from Ford and multipal other sources compiled in one place. Also had fixes to some issues, design improvements, most of which were ignored or bandaided.
Most engines need to be vacuum filled with coolant (some big truck repair centers have the ability) they are at the factory. Some just need some bleeders installed in the proper areas.
Theromostats still have bleed holes in them but are little V notches stamped in the edge. Look closely and you will see them. There is a wrong and right way as to were to oriented the bleed hole in some applications such as a SBF not as necessary as a 460.
My last Boss 302 I actually manifolded water down the side of the block into each of the threaded freeze plug holes. Something done on some exotic engines.

 

[THE FRENCHTOWN FLYER]

Most engines need to be vacuum filled with coolant (some big truck repair centers have the ability) they are at the factory. Some just need some bleeders installed in the proper areas.

I install Schraeder valves at the high point in my drag cars' heads. You can get them at most hardware and big box home improvement stores in the plumbing section. Usually they have 1/8 or 1/4 NPT threads. They are especially useful since my electric water pumps do not provide enough velocity / volume in the water jackets to purge the air from the cavities. Also, some of my installations are "nose down" so the high point is the rear of the head.

 

[Anonymous]

The maker of Evans Coolant has stated that if you could find all the hot spots over the combustion chambers and alter coolant flow in such a way to keep the steam bubbles scrubbed away, you would greatly retard the onset of detonation (and his coolant tends to deal with hot spots). For a gross difference like an entire cylinder (the back one in an I-6??) running hot, possibly you could detect it with one of those infrared temp guns, or see "cement boil" or other spark plug distress if it were really bad. But lesser temperature variations around the engine would seem pretty hard for the home mechanic to find . . . unless you have some trick. If you could advance the timing of individual cylinders to the point of pinging . . . aren't there some computerized systems that allow this??

 

[turbo2256b]

We had a meeting with Evans once. Ford wouldnt bite on the price per gal. Also quanity was limited. Didnt do anything great for emission reduction.
Did build a one of engine nothing that ever went into production to realy get into the nitty gritty of optimizing flow, velosity, pressure were it was most desireable. It was akin to setting up a circuit board to direct certian amounts of voltage to different parts systems in electronic equipment. Cant remember what the project was called precision cooling.

I know what I would like to do but would take a basicly new engine heads block intake

 

[Anonymous]

Well then, you mght get in touch with the person on this site who is designing a new aluminum crossflow head for the Big Six and is already casting heads for the Small Six. Maybe he would appreciate your input. I expect that aluminum is somewhat more forgiving than cast iron of coolant flow problems, but if you're creating a new head, you'd want it perfect.

Of course, that's just the head and you were envisioning a "clean-sheet" engine, but supposing we had a new head done to your specs, maybe we could take a factory block and drill out or restrict existing holes, drill and tap new holes for external lines (lots of race-motors get auxilliary side-oiling; why not coolant?), modify the pump (Ford's or one of the aftermarket pumps) with deflectors, a modified backing-plate, or whatever, alter the thermostat housing, change radiators, change engine-compartment airflow, just a lot of things can be modified by anybody who enjoys fooling with this stuff, . . . which pretty much covers anybody on this sub-forum.

And personally, I really don't think of this sort of optimization effort as mere personal ammusement for gear-heads, not nowdays. Between running a service truck and my ordinary driving, I am spending an absurdly huge amount of money on fuel every month. An optimized engine with the cylinders cooling evenly (and fueling evenly) lets us crank up the effective compression more than we could without this effort, on the way to getting an engine that works hard and gets the best fuel efficiency possible without detonation. Fifty dollar bills come in after considerable effort, and go out like "Monopoly money," and I'm tired of it. So I'm very interested in any of the useful info that appears here.

 

[Anonymous]

Dang, sure did throw a wet blanket over this thread (sigh!).

 

[turbo2256b]

Been busy here. Aluminum is less forgiving actually. A spot were nucleate boiling can ocure could mean instant burn through.

 

[Anonymous]

I'm just a dumb welder, but isn't film-boiling the situation to avoid (a layer of vapor that has low thermal conductivity, clinging to the metal surface and not being scrubbed away by flowing coolant)? Of course you can have eddys and no-flow (not much coolant movement) areas in either iron or aluminum heads, and I hope you'll advise us about modifications to avoid this. But are you saying that a (relatively) hot-spot over a combustion chamber in an aluminum head which has coolant flowing through it could actually burn through?? The aluminum head seems like such a big heat-sink, made of a thermally-conductive material. Is this melt-through something you have seen? I can imagine severe detonation knocking a hole in a thin and hot/weak ("hot-short") spot, but just melting through surprises me.

 

[MPGmustang]

I thought for a forced air, depending on PSI you want '.1' richer for each PSI boost, up to 1.0 total points... IDK where I heard it from

but IMO 11:1 is rich I would aim for 12:1 and stay on the rich side to avoid detonation, it's more fun to use more gas than parts...