when i get this '66 88 running,i'de like to maximize the mileage i can get out of this big boat and was thinking of installing o2 sensors in the manifolds,left and right,and monitor for the best mileage,and do changes as needed.you might be saying WHY,i say why not..i'm almost sure no one has done this,i figure with a 3.23 rear,200r4,425 with a 600 holley or quadrajet should get over 22mpg...am i dreaming here...be kind!

 

I thought O2 sensors make changes automatically through a computor carb or fuel injection. They do this at different loads and RPM. I do not understand how you will read sensor output and adjust to get what you want.
That said, if you go to computor controlled fuel injection, then I can see it.

 

Just get a vacuum gauge and drive with a very light foot so it maintains the highest vacuum.


If you really want to get technical you can hook up a wide band AFR gauge. With a carb you physically have to change jets. Click on link below:


http://www.summitracing.com/parts/SUM-G2995/

 

I think you're dreaming if you think something like this can work, but who am I to say?

First, as m371961 notes, O2 sensors are integrated with the computer control on the engine. Very small adjustments are made continuously to react to what this and other sensors sense. What would you connect an O2 sensor TO so you can see what it's reading? What would you take as a "normal" value on a '66 Olds engine? What would you adjust if you were to decide that the O2 reading you were getting was somehow not normal? Etc. Etc. Etc.

The best way to maximize the mileage out of your '66 engine is to keep it tuned according to the manufacturer's specs. Don't try to be a hero and glom early 21st century engine technology onto a mid-20th century engine.

 

http://www.innovatemotorsports.com/

A wide band O2 sensor?
This may be the easiest way to set up what you want.
Comes with Air/Fuel ratio gauge.

 

It's called an air/fuel ratio meter (or, more accurately in the modern era, a wideband air/fuel ratio meter).

Lots of people have them.

In your case you're looking at installing two, at a cost of about $200 apiece.

- Eric

 

O2 sensors simply change voltage output in response to the oxygen in the exhaust. How this output is used varies. Computer controlled cars (both EFI and the CCC carb systems) use this voltage change as one input to the ECU. Along with other inputs (MAP, TPS, MAT, CTS, etc) the ECU looks up the correct fuel delivery based on a pre-determined fuel map. Aftermarket air/fuel gauges use the O2 sensor output to operate a gauge. You (the driver) act as the ECU by reading the gauge and changing the jetting in the carb to accommodate.

 

So you can install a aftermarket guage that reads air/fuel ratio under all conditions?
I gotta look into this.

 

Sure you can.

All the ricer guys have them.

They can really help you dial in your jetting.

- Eric

 

well i'm glad some guys understand my original goal in monitoring the air fuel ratio to i'ts optimum.too bad i need 2 sensors as it will be duals.also a vaccuum gauge is a must.maybe it's a crazy idea but with 27yrs with a turbo buick and learning how it runs,i just wanted to see what i could do with the olds.nothing wrong with trying to modernise an older car within reason.thanks..paul.

 

To be square, you can install an H pipe and do with only one sensor.


Facetiousness may exist in this post.

 

Correct. And just installing a wideband and gauge doesn't modernize your car, sorry. Only EFI etc would do that. All you're doing is using the wideband to see how your current setup is jetted, rich or lean. Then you can adjust from there (via jet, power valve and air bleed changes).

I'd shoot for about 12.5:1 at wot and somewhere around the low 14's for a cruise ratio. Much leaner than that and it'll probably surge.

 

Good luck with the tuning.
22 mpg may be a stretch. Upper teens possibly.

 

did some looking around,summit has a bunch of brands for air-fuel gauges and i like the AEM gauge..p/n 30-5130 or 30-4100.$220.00...auto meter,p/n 6178-7178-7378-4379...innovate p/n-3845...i'm thinking of putting one a/f gauge on 1 side and a pyro gauge on the other.as far as modernizing an old car,i'm just trying to make the old girl run a little better with what i got for now!.third brake light,pass side mirror,better lights,a real horn are all things that will make it safer than in '66.thanks..paul

 

There is no reason to install a pyro gauge. Running an A/f gauge on one side only is a waste of money, you need both sides to get an accurate assessment. IMHO you don't need one of those either. What you need to do is maximize your tune and maintain it. Buy a mountable vacuum gauge that you can see while driving and drive it with a light foot to keep the vacuum in it's upper levels. That will give your the best fuel economy. Use the extra money to make the car nicer.

 

ASSUMING the carb is jetted correctly. Any changes to intake, air cleaner, exhaust, ignition timing, etc. will affect the necessary jetting for optimum A/F ratio. For that matter, E10 fuel affects the required jetting. The vacuum gauge won't tell you whether the jetting is correct or not. As for one vs. two O2 sensors, the reality is that even with dual exhausts, one is probably good enough. Unless you're going to monitor all eight exhaust ports, you're always getting an average reading and hoping that the mixture is correct in all eight. Frankly, since a dual plane manifold runs cylinders 1, 4, 6, and 7 from one side of the carb and cylinders 2, 3, 5, and 8 from the other side of the carb, a single O2 sensor in one manifold will "see" the jetting on both sides of the carb. If you're running a single plane intake or a large open plenum spacer on a dual plane, the problem gets even easier.

 

I have an AEM wide band A/F gauge on my '65 with only one O2 sensor in the drivers side pipe right after the header collector. I can assure you it isn't a waste of money. It's one of the best tuning tools you could possibly have. I've been using it for two or three years now and wouldn't have a carbureted hot rod without one. BTW if you really want to see what's going on on the other side without purchasing another gage you can just install a bung in both sides and move the O2 sensor to the side you wish to monitor at that particular time. I think you will find it isn't much different from the other side.

 

The only thing that MAY change that a little is the difference in plenum size, one side vs the other. Otherwise a single works just fine.

Check out the AEM stuff. They even have one that's wireless thru your smart phone.

 

Ya, what Chadman said. IMO second only to a timing light as far as tuning tools go.

Relevent (IMO) - what do people run for A/F @ cruise? Lemme know If I should just start a new thread.

FWIW I set my stuff @ 14.7 idle, 12.5-12.8 WOT, 15.5-15.7, will occasionally hit 16 but never get ping or surge. Too lean? OK?

When doing other folks stuff I go 15:1 @ cruise.

 

Fwiw

 

Most people I know have bungs in both exhausts to move the sensor from side to side and get an accurate reading. The gauge is not a permanent fixture in their cars, it's tuning aid. I've seen people compensate with a faulty carb where one primary jet is dripping by leaning out the other side to compensate and getting a good average A/F reading.


Again, as his car is not a performance built custom engine, a simple vacuum gauge and proper tune will suffice to attaining the best fuel economy. He can spend the extra money on other things.

 

I plan on getting an A/F gauge also. I'll put it on the drivers side exhaust pipe. My jetting is way off on my carb. Keep us informed on how this works out for you.

 

Third brake lights are overrated unless someone is up your exhaust pipe already. Passenger side mirrors were dealer options and a good idea. Stock GM dual note horn pairs are loud in good shape and sound good. Rock some Halogens and light up the night.

 

I would agree, but...

The fuel most of us use is different from the fuel that these cars were designed and jetted for.

Modern fuels with ethanol (ethyl alcohol) and/or MTBE (methyl tertiary butyl ether) have significantly more oxygen within the fuel than there would be if it were made exclusively of hydrocarbons. The effect of this is like adding extra air to the gasoline. In a carburetor, this means that less combustible gasoline is flowing through each jet under a given set of pressure circumstances, and means that, figuratively, some air is entering through the jets. This causes the mixture to be leaner for any given jetting than it was intended to be by the factory.

Using an AFR meter can tell you how much leaner, and help you to set it back up to the way it was supposed to be.


I agree with all of this, and I don't see how anyone can say that original GM horns aren't loud.

- Eric

 

Why do you keep insisting this?
If it's running richer or leaner than optimum then all a vacuum gauge will do is tell him its the best for that air/fuel, even though it may be wrong.
Richen the idle screws on your car, then adjust the timing for the best idle vacuum. Then optimize the idle screws for the correct air/fuel and tell me the vacuum gauge doesn't read differently.
Let me guess, you've never used a wideband correct?

 

Mark your missing my point, his car is stock, 100% stock. How far off can it be if his carb is operating correctly and he has a good tune. The manufacturer had already determined what the proper settings should be and any deviation from that will be minor at best. Any time the temp, humidity, or the barometric pressure changes it throws the A/F off with a carb.


No I've never used one, I still do it the old fashioned way. I look at the plugs, and listen to the engine. Can I gain a bit of power and efficiency by spending a bunch of money by using one and booking a bunch of time on a dyno, maybe.


I'm not talking about him using a vacuum gauge to adjust his carb. I'm talking about him driving with one bolted to his dash at all times and limiting his fun pedal to operating the car at it's highest vacuum during cruise. It was called a fuel economizer back in the day.

 

I'm a big fan of using a wideband to tune carbed engines. I've had one for some time, and I'm currently using one to tune the Holley 3310 on my Procomp headed 455. Other than at idle, where you can certainly get away with a vacuum gauge and a tach along with a well tuned ear, there is little that would tell the difference between 13:1 and 16:1 at cruise.

It's also very tough to tell much about the WOT air/fuel without the wideband. Yeah, you could tune based on ETs and MPH at the track, but it's much easier to tell what's going on with the wideband. Coupled with a vacuum gauge you can tell how the individual carb circuits are working in the carb. If you put in a 6.5" power valve, for example, you can tell right when the extra fuel comes in. It is far and away the easiest way to optimize all the circuits in the carb.

Tuning is like voodoo without it. My car ran fine with a 13:1 cruise and 14.3:1 at WOT. Without the wideband I would have thought everything was great, obviously this was not optimal, and a 14+ AFR borders on dangerous at WOT. The car runs much better now, and it''s noticeably faster with a richer AFR. However, the "upside down" behavior of the power system would have been difficult to detect. This was an easy fix, and easy to quantify the results of making the PCVRs bigger.

It's hard for me to fathom, but people often are willing to spend thousands on an engine, but then will just slap a carb on it and expect it to run. It's worth a few hundred bucks to make it run right, either by buying a wideband and doing it yourself, or paying someone to tune the car properly.

 

Or you could just move to the U.S. and not worry about mpg. Gas is $3.26 for regular today. I felt like I was stealing it

 

i know what you mean,my cousin lives in mi.i fill up before i come back up.. well,oldscutlass,my car will not be stock as i will be putting on an edel.perf and i have 3 carbs to play with..holley 600-quadr.from '79 camaro-and original carter 750..that's why with an a/f gauge and a vac gauge,should be fun.i also like the aem-30-4100 gauge.

 

THANK YOU!!!!

Eric (oldcutlass) do you think fuel composition has changed any since the 60's? You bet, a bunch. That alone will have an effect on the air/fuel.
Plus were they worried about emissions and/or mileage in '66? Not hardly.

 

Look, we'll just agree to disagree. My point is not against the meter in purely performance applications, I suggested the link early in the thread. My point is for the op's application.

 

another thing to bear in mind: back in the days before emissions and mileage were thought about much, the factory set these carbs. up to run on the richer side of 14.7, across the board. this was done to account for manufacturing tolerances, varying quality of fuels, and varying operating temperatures. you can keep many issues "hidden" by throwing a little extra fuel at things. if the op really wants to mess with things that much, a wideband O2 setup would be very useful.


bill

 

I've never used a wideband air fuel meter to tune a car with a carburetor. I have used an OBD 2 scan tool to monitor O2 sensor output.

I read through the entire thread. I have to say that using an A/F meter to tune a carb would be the best way to do it. How else would you be able to tell the difference between different metering rods, jets and hangers in your Q-jet? That being said, I use a timing light, vacuum gauge, and tachometer to set the tune on my 71 98 and it runs fine.

Of course, there is always value in buying tools and cool stuff just to have it! The other day I was looking at portable gas analyzers that were over $1500 (to monitor HC, O2, SOx, NOx, CO, CO2)

 

While I agree with the comments on the wideband, my thinking is that, while I like economy, I like perfect, safe performance more. So, if it runs a bit better a little rich, that's ok with me. In other words, I'll tune for best operation over most economical.

 

The great thing about tuning with a wideband (if you understand how to tune the different carb circuits) is that you can actually do both. You can tune for both economy at idle and cruise and max power at WOT.

 

And unless the OP can still buy 1960s gasoline, the stock jetting will be wrong for optimum power and economy.

Yes, you CAN tune a car properly without an A/F meter. To do that means that you have to know how to properly read plugs.

 

You dont need 2 sensors. As a matter of fact most aftermarket TB EFIs only have 1.
It will allow you to optimize your jetting. Do you know how to jet the circuits on a holley, qjet, carter?
After you're jetted correctly, you're pretty much done with it.
22mpg on a big car, maybe if you only drive downhill. Don't expect dramatic changes in mpg by rejetting a stock carb on a stock motor.
If your goal is better mileage, a vacuum gauge will be a better indicator. There are other things you can do, primarily to keep rpm down, that will help with mileage.

 

My 2 cents on tuning without the wideband is that it is certainly possible, and people did things that way for decades. A wideband allows you to optimize things, however. It's more than just the jetting, too. You can optimize every circuit in the carb, although this requires a pretty extensive knowledge of carburation.

In a Holley, at a minimum I would expect to change the jets, the power valve (for vacuum opening point), and the power valve channel restriction size (which controls the amount of fuel delivered by the power system). A Qjet or a Edelbrock/Carter can accomplish the same things with jets, metering rods, and power piston springs. In general, you can put a pretty good tune on your car with these. For most street cars, I would expect to shoot for about 12:1 at WOT on the power system and 16:1 at cruise. Of course, the engine will tell you what it likes to some extent.

Beyond those, on a Holley, there are the idle feed restrictions and air bleeds, as well as the main air bleeds. Emulsion tuning is real black art, and easy to make changes to if you have one of those fancy billet metering blocks with 10 little jets in it. There is also the easily adjustable accelerator pump, with the multicolored cams. All that stuff probably needs changes to be truly optimized. This is a far cry from what I generally see with the way cars run at the car shows.

For the OP, 22 mpg is probably pushing it, but a lockup overdrive should help a lot. As an example, my Dad had a '68 Camaro with a modern 427 LS7 producing about 600 hp at the crank thanks to a bigger cam, headers and a very free flowing 3" exhaust system. It had a 6 speed manual and 3.50 gears behind it that made for about a 1900 rpm cruise at 80 mph. Doing that speed it would get about 20 mpg, maybe a touch more on occasion. This was using a modern fuel injection system, as well.

I think a well setup carb could have been more efficient, simply because the GM computers will not really allow for an AFR that is greater than 14.7:1 due to emissions concerns. Bumping the cruise AFR to 16:1 should result in a nice gain in economy. As a counterpoint to that, I saw as high as 14.5 mpg with my last 455/TH400 3.08 rear setup in my 442. That was using a Edelbrock 650 AVS with a mild engine build tuned in the 16:1s at cruise.

I'm sure a big car is heavier and probably has even more bricklike aerodynamics than his Camaro had, so that would be working against you. You'll have a steeper final drive ratio, too, but you may only cruise a 65, for example, which, in my experience, makes for much better economy. I just don't have that sort of patience, and all our rural freeways are 75 mph limits out here.

 

hi,i think up here in canada where gas is 6.50@gal.i think it makes a little bit of sense to see what i could.every little bit helps.thanks for the answers and suggestions.there will be more i hope..this will be a spring project for me so got all winter to debate.i think i'll put the sensor in the pass.side man.AEM-30-4100 looks good.

 

What do those cost up there?