200 MPG Carburetor Talk

[Frank Lee]

Originally Posted by mja1

Not true. for 99.9999999% of cases yes.

Oh gosh, in that case, I change my position completely.

[mja1]

Originally Posted by Frank Lee

Oh gosh, in that case, I change my position completely.

Kinda like a cheetah is faster than a crow, but 99.99999% of the time the bird is flying around faster than the cheetah. It's not to say I want to change peoples minds from a great form of technology, EFI is amazing. I was just commenting on this thread about gas mileage carbs with information on the subject.

[Frank Lee]

I like carbs, they are simple cheap easy to fix. Where is this carb that is better than efi?

[user removed]

Yep let me stick this heah myricle crab on yo motoah and yall weel get 200 miles per galin.

You know I find it humorous that the claim has now inflated from 100 MPG to 200 MPG. I guess it follows the philosophy that if you lie enough and lie big enough then someone will believe you.

If you want to read some interesting stuff look at what has transpired as far as engineering an engine for 60% thermal efficiency which is what you would be required to exceed if you were going to get 200 MPG out of any car, with just the replacement of the carburetor with your "miracle" carb.

While Homogenous Charge Compression Ignition designs claim improvements in mileage as high as 25%, I don't think they have quite got to that level and that is under very narrow and very specific loads at constant speeds on a dyno, nothing like real world scenarios.

If you understand the numerous reasons why vehicles do not get over 100 MPG, then you might realize that it ain't going to happen by sticking a carburetor on a vehicle and doubling, tripling or quadrupling the mileage. Believing this to be possible just clearly shows that the believer simply does not comprehend the issues involved in maximising vehicular efficiency.

regards
Mech

[user removed]

Originally Posted by Frank Lee

I like carbs, they are simple cheap easy to fix. Where is this carb that is better than efi?

I have one in my garage Frank, right next to the Brooklyn Bridge.

Mech

[mcrews]

Originally Posted by SOUL-DRIFTER

I remember some cars like the first year or two Honda that advertised getting 60mpg, they were not fuel injected back then. Yet the EFI of today does not get close to that.
So what is the explanation there?

Sorry to say this, but how can you claim to be a mechanic and ask this?

Those first 'civic' probably didnt weight half what the next gen civics weight.

And the engines had no power.

There there was all the smog requiremnets that followed.

(or maybe they pulled off those '60mpg carbs')

[IamIan]

Originally Posted by mja1

The lower pressure fuel of the carb has the 'potential' to take advantage of high AFR's. This is the point where a carb outperforms EFI in efficiency, where the ICE is limited only by the melting point of the engine materials used, not by the ignition & fuel timing as in traditional EFI.

What OEM Carb based ICE achieves higher AFRs than the 25.8 : 1 that some OEM EFI ICEs have been tested to be able to achieve?

What I've read EFI systems have superior higher LB AFR benefits potential to Carb based systems... thus ... from what I've read ... it is the opposite of what you are claiming... and it is Carb systems that suffer with lower AFRs.

[slowmover]

I always did want to test & tune one of the FISH carbs on a mid-70's Slant-6 PLYMOUTH "Feather" Duster. There were some aluminum block versions of this motor from 1961 that would have been good to change over to (170-cid I think); plus (modified Wiki quote):

The Feather Duster featured lightweight aluminum parts including the intake manifold, bumper brackets, hood and trunk bracing, and manual transmission housing, for a weight savings of about 187 lb (84.8 kg)—5% lighter than a standard Duster similarly equipped. It came with a I6-225/1V Slant Six with fuel & ignition delivery calibrated for economy, a low-restriction exhaust system, an extra-high 2.81:1 rear axle ratio, and was offered with . . [an] A833 overdrive 4-speed manual transmission. It was the most fuel-efficient car in its size class, EPA rated up to 36 mpg highway and 24 in the city. (along with Dodge's version, the Dart Lite).

Fish Carb Stories

The Fish Carburetor Manufactured by the Brown Carburetor Company

Would be (would've been) a thrill to hit 40-mpg highway in a car big enough to carry normal sized people comfortably. Who'da believed it in 1976? (this funny carb or not).

.

.

[mja1]

Originally Posted by IamIan

What OEM Carb based ICE achieves higher AFRs than the 25.8 : 1 that some OEM EFI ICEs have been tested to be able to achieve?

What I've read EFI systems have superior higher LB AFR benefits potential to Carb based systems... thus ... from what I've read ... it is the opposite of what you are claiming... and it is Carb systems that suffer with lower AFRs.

The main reason we have EFI is to tune exactly to spark. The point where carbs become more efficient is above 26-27:1 AFR. Around 28-30:1, so combustion temps are just below the melting point of steel (think upward to 2500 deg F combustion temps), which is what adiabatic ceramic engine's are all about. And you're knowledgeable enough to know that this can't happen on a traditional ICE. When we're talking about an ignition based ICE yes, but not when there is no ignition.

Preheat the fuel to 450+ degrees before entering the intake manifold, (autoignition temp of gas is 475 deg F+), the pressure of the cylinders works the combustion. It's walking a fine line against extreme backfires outside the combustion chamber but it's been done, and it's not at all an OEM setup. I guess I wasn't clear that the idea couldn't be achieved on any old stock carb. Or any old engine for that matter. It'd be a very tricky process, and it can't be done with EFI. Most FI systems run at least 30psi (most stock ones 45-65), where carb can run less than 5psi. Much easier to 'preheat' a lower pressure fuel.
...an ignition is needed to get the whole system up to operating temps, but after that its not needed

[IamIan]

Originally Posted by mja1

The main reason we have EFI is to tune exactly to spark. The point where carbs become more efficient is above 26-27:1 AFR.

Not just for the spark... EFI at it's core is about precise control of the Fuel ... it is commonly used in spark ignition engines ... but that is for other reasons... not for any need of a spark for a EFI system.

I can give you sources of a OEM EFI engine being tested to run at up to a peak of 25.8 : 1 ... do you have any examples to share of an carb based OEM ICE test showing the 26+ you claim here? ... or any non-OEM modded system?

AFRs more than a certain point are not even readily combustible ... it is the combination of a swirling effect with the tuning of the spark just right that can allow for the effective combustion of a very lean AFR... the swirling EFI can create intentionally uneven AFR points inside the combustion chamber , in controlled ways and controlled timing ... and for effective LB high AFRs this is beneficial... in a general AFR that is not otherwise effectively combustible the controlled swirling effect and timing of a EFI system can achieve combustion where it could not be achieved otherwise...

In theory a modern EFI system like this can be used to run even non-spark / compression ignition engines at higher AFRs than they would be able to achieve otherwise ... I don't see a Carb based system being able to do this.

Even modern diesel engines without an hypothetical EFI system take advantage of a noneven AFR mix in the combustion chamber in order to achieve combustion of AFRs leaner than would be possible at a even AFR mix.

Carb based systems have inherently less control of the fuel in the combustion chamber than a EFI based system does... the carb based system concept is dependent on the concept of a preAFR mix ... this concept does not allow for the same level of precision fuel control in the combustion chamber that a EFI allows.... a premix or an even mix is not always the best mix in the combustion chamber itself.

Although at high enough AFRs it is reducing , not improving ICE net operating efficiency ... and without higher net operating efficiencies you aren't increasing MPG or FE any more.

Originally Posted by mja1

I guess I wasn't clear that the idea couldn't be achieved on any old stock carb. Or any old engine for that matter. It'd be a very tricky process

Which would exclude the entire market for the '200' MPG carburetor.

Are you thinking of an experimental ICE design from the ground up?

Originally Posted by mja1

Most FI systems run at least 30psi (most stock ones 45-65), where carb can run less than 5psi. Much easier to 'preheat' a lower pressure fuel.

I don't see any reason why the pressure of the fuel has any significant effect on how 'easy' it is to preheat ... the amount of energy needed to raise a given amount of fuel any arbitrary temperature is purely a function of the specific heat of the fuel and the total mass of fuel being heated.

I also don't see a low fuel pressure being a significant advantage ... if anything I see it has been well proven as a significant disadvantage in many ways.

I also don't see a net efficiency benefit of spending fuel energy to preheat the fuel above the amount of preheating one can get from the ICE's operating waste heat... and 450+ is significantly above that point.

Also , Preheating the fuel is a very different topic from the 200 mpg carburetor ... it works for and on different principles.