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feed back carburetors

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Discussion Starter · #1 · (Edited)
I have come up with a way to have a feed back carburetor as long as it is a 4 stroke engine and has a sealible carburetor

I am just looking for some feed back (sorry had to use the pun) if there is a market for a device like this.
 

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Discussion Starter · #2 · (Edited)
feed back carburetor

I have come up with a way to have a feed back carburetor as long as it is a 4 stroke engine and has a sealible carburetor

I am sorry I don't know how to fix the grammer error on the poll choice's, so please vote under this thread

I am just looking for some feedback if there is a demand for a device like this
 

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Would need more info, how it works, costs, etc.
 

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Discussion Starter · #7 ·
no bs 100 mpg carb

Im just a mechanical engineering student that is going to do an independent study on this, I have designed a controller that would keep the engine running at a set lambda (AFR) at part throttle. As stated before It would work on any 4 stroke spark ignition engine providing it has a carburetor.

Im making one now, I should be able the make one for myself for about $20 but that is with using scavenged parts. I am guessing that new on the market price would be about $130-$170

I am just trying to get a feel if there is a market for a device like this, and if so I might consider applying for a patent
 

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hahaahahhh some guy already made one!!! he got a patent on it and the company put that carb on the shelf and he never saw a dime!!!!!!!!!!!!!! too many politics!!
 

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Perhaps we should not completely rain on this young man's parade?
Perhaps offer some constructive suggestions and point particular areas he will need to consider?

We were all young with big ideas and without the cynicism of age once ;)

While many things have been tried I will bet that there is a lot of learning that can be had by trying again. Maybe he will be the one to crack the nut.

Lessee... at cruise you have to deal with both idle circuit and main circuit. You may be able to provide the required fuel trimming via just the idle circuit. This would also allow trimming of the idle mixture. So have at it!
 

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GS,
Same system that is on my Wife's 84 Riviera ?? And about a bazillion mid 80's GM vehicles ? You can probably get the ecms for next to nothing at the bone yard, same with the E4MC Q-jets.
 

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Discussion Starter · #12 ·
I have used the concept to operate my Lincoln Mark III on E85 and gas (any mixture of the two) through the same carb and retain stoichiometry(sp) I am just automating it now. Like I said before it is easliy adaptable to almost any carb and shouldn't have the querks the 80's feed back carbs did
 

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I have used the concept to operate my Lincoln Mark III on E85 and gas (any mixture of the two) through the same carb and retain stoichiometry(sp) I am just automating it now. Like I said before it is easliy adaptable to almost any carb and shouldn't have the querks the 80's feed back carbs did
Actually Greasefire, having lived through the feedback carb craze I can tell you that the GM feedback carb setup worked very well and was not quirky at all. The only problem they ever really had was the two o-rings on the bottom of the feedback solenoid would leak at about 100k miles, but they were extremely easy to replace.
Not to rain on your parade, but as one of the other posters said, the feedback carb has been done to death by quite a few car companies and they worked well. The sticking point is that no matter how well you control the mixture, the engine has to use a certain amount of fuel. And no matter how well a feedback carb meters the fuel, fuel injection will do it much much more precisely. Anybody that wants to control the fuel map that precisely will just use fuel injection.
Good luck,
Mike
 

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Discussion Starter · #14 ·
you bring up some good points LS-5, but retro fitting fuel injection on an older vehicle is an expensive venture unless your using junk yard parts. While the carb modification would be relatively inexpensive and offer most of the benefits.

In hindsite this is probably the wrong area to ask this question being that this board is very performance orriented and the topic at hand does not increase power.
 

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Back in the late 50s- early 60s there was a carb that was desighed that would give you a 66 miles per gallon and a gas company & Gm bought it and have patents on it. I believe it was Standard Oil. It was designed to fit all engs with an adapter. I was in automotive school at time was wondering why would Gm & Standard would buy it out unless they would put it on a standard car. Duhhhhhhhhhhhhhhhh. .hummm was I naive.
 

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Greasefire: I also don't want to rain on your parade, but an AUTOMOTIVE engine will not work with straight 14.5:1 mix. As you know, it always burns at 14.5:1. But because of varying vacuum and pressure from the venturi to the end of the burn cycle, the MECHANICAL ratio must vary to attain 14.5:1 under all operating conditions. Don't forget that TIME also enters into your equalization conundrum. (Look up B.S.F.C.: Brake Specific Fuel Consumption. Find out how that applies to different fuel ratios and burn efficiencies.)

You also need to read something about the inability of a carburated system to deliver equal mixture distribution to each cylinder. The only way your carb plan can work is to have one carb for each cylinder and a O2 sensor for each cylinder. Monitoring the tailpipe gas will only give an average of all cylinders, not the mixture of each cylinder. (That is the way it works with injectors, also.)

Don't give up thinking!!!! That's the best part of life. Good Luck in your endeavors. And stay on the Chevelle Forum. Your next idea might be one we can all use.
 

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Greasefire: I also don't want to rain on your parade, but an AUTOMOTIVE engine will not work with straight 14.5:1 mix. As you know, it always burns at 14.5:1. But because of varying vacuum and pressure from the venturi to the end of the burn cycle, the MECHANICAL ratio must vary to attain 14.5:1 under all operating conditions. Don't forget that TIME also enters into your equalization conundrum. (Look up B.S.F.C.: Brake Specific Fuel Consumption. Find out how that applies to different fuel ratios and burn efficiencies.)

You also need to read something about the inability of a carburated system to deliver equal mixture distribution to each cylinder. The only way your carb plan can work is to have one carb for each cylinder and a O2 sensor for each cylinder. Monitoring the tailpipe gas will only give an average of all cylinders, not the mixture of each cylinder. (That is the way it works with injectors, also.)

Don't give up thinking!!!! That's the best part of life. Good Luck in your endeavors. And stay on the Chevelle Forum. Your next idea might be one we can all use.
Kirk, just for some interesting information. Some of the more advanced injection systems are actually using individual cylinder mixture adjustments based on single oxygen sensor readings. In a nutshell this is accomplished by knowing the individual cylinder exhaust pulse timing through the exhaust port and manifold for a given engine operating condition. Thus knowing when a particular cylinders' exhaust charge is being read by the O2 sensor. This is how precise some engines are controlled and also why performance or driveability is killed sometimes when some jughead modifies a new car thinking he knows more than the engineers that designed them.

Greasefire, good luck with your carb thingy but just be aware that if you're looking for the magic 66 mpg carb, you won't find it, it's a myth (unless it's on a moped). One needs only look at the physics and math regarding the power needed to move a particular weight vehicle and the air/fuel requirements to make that power for a given engine size/efficiency. The best your gizmo could possibly do is make the carburetor 100% efficient. Even if you miraculously did that your mileage would still be mediocre at best. If you think it's gonna get 66mpg, you better be putting it on a carb on a very very small car with a very very small motor.
But, as you know, the only cars using carbs anymore are hotrods and I think your poll has shown that people aren't too concerned with mileage on a 540ci motor. Great thinking though.
:beers:
Mike
 

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The 100 MPG carb myth has been around as long as I can remember. If you just look at how many HP are required to drive a vehicle, and then look at the number of BTU in a gallon of gas, and then take into consideration the 60% to 80% inefficency of the IC engine; you will see it ain't going to happen.

Even mopeds don't get 100 MPG. I wish people that think 100 MPG is possible would just do the math. Unlike the Kennedy assasination, the Tri-Lateral Commission, and the Masons trying to kill Art Bell; there is no anti-100MPG conspiracy.
 

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Discussion Starter · #19 ·
I know the "100 MPG" carb is not thermodynamicly possible I have actually calculated the numbers on it (in kJ/kg rather that BTU/gal, I hate english conversions like 778 lbf*ft=1 BTU)

Lowest brake specific fuel consumption is generally around 15.3:1 for a gasoline engine. They are run at 14.7 for emissions purposes.

Ken, when you say that they run an average, this is true but it is because of the way narrow band oxygen sensors opporate ( and average cylinder mixture). In my opinion is shouldnt be called a sensor but rather a > or < switch.

I take my chevelle on long cruises (500 miles one way) and I like to tinker with carburetors so I like to optimize all fields (that I am concerned with) of performance. Someone who only drives around town or only races would not benefit from this device.

This idea was never to replace fuel injection nor promote false economy claims ( and if you look through my posts I never claimed this) but to be able to allow the average carb guy to tune for WOT at the track and then let my device trim the fuel mixture everywhere except WOT and aggresive throttle movements.
 

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One thing you need to consider is that many of those interested in this level of optimization have already made the jump to EFI because it does it much better than a carb ever could. And it does more: real time spark adjustment is just as important as fuel mixture adjustment.

It is true though that many, perhaps most, retrofit EFI setups are sub-optimal in the area equal cylinder charge. What might be more marketable would be good retrofit long runner EFI manifolds optimized to provide equal cylinder charge and higher flow rates. And fit under the hood :thumbsup:
 
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