Technical What Carbs Became What...

I have one of those! Don't remember where I got it here in the center of CT. Scrap yard I think.

 

I got mine at Don's, on the Berlin Turnpike!

 

I have a C3BX for one of those!

Gary

 

I saw that episode also, and likewise was very surprised at what they concluded. I remember one sentence I think flybooger said, "carbs make more power because they have a higher air flow that cools the fuel charge more at high revs, hence denser fuel charge"--or something to that effect. Right away I wondered if GM, Mopar, Ford, etc. were watching this and thinking what a mistake they made on their supercars!

 

The vast majority of oval track racer’s are still using Carburetors. Mostly Holleys.

 

My summertime old car activities take me from just below sea-level, to just about 10,000-feet in elevation (10,225.2-feet, actual change).

I got tired of stopping to do jet changes. Performance is identical, but now consistent over the entire range.

Mileage went up by 12%.

A laboratory dynamometer is not the real world is not. The real world is not a laboratory dynamometer.

 

Science is always right except when it isn't

 

I can assure you that they had no reason to even think about it.

No automobile manufacture is building any regulated road-going vehicle with maximum power as the only concern.

There are bigger concerns, those being tailpipe emissions standards, and CAFE standards.

Carburetors no longer exist on production vehicles because even the most brilliant design cannot maintain compliance with those last two standards.

If overall performance has to be reduced to make that happen, then that is what happens. That is the world we live in now.

Just be happy you can still elect to dump unburned fuel, and all the pollution you want into the environment.

 

The vast majority of single engined general aviation airplanes are still using gasoline burning piston engines too. But the world's air forces and airlines have moved on.

I think many racing sanctioning bodies stipulate carburetors for many classes for various reasons, not because they make more power.

 

It is due to Latent Heat of Evaporation.
The carb is father from the intake valve than the injector is.....the fuel introduced has more time to draw heat out of the intake charge as the fuel vaporizes thandoes fuel injected closer to the valve.

You've seen an alcohol mechanical injection or Alcohol carb all frosted up after a good run??
Same deal is happening there, on a bigger scale.

Electronic fuel injection is better on emissions, cold start, and ease of fuel curve adjustability.
It just loses by a tiny amount on the peak HP race.

 

Great thread. I had one of those Holley spread-bore carbs. I tried a bunch of stuff, but it always had a bog when you smashed the pedal. Opposite results with a Quadrajet. I love to hear that honking whine of the big ones kicking in. It has something to do with the design, acts like variable venturi? Not sure of the terminology.

I bought a Dodge 318 with a thermoquad. First thing I did was bolt on a Quadrajet; literally, the bolts line up, linkage, everything. That 318 HO 4V engine was out of a mid eighties cop car. Plenty of power for a work truck, but the point is: the Quadra added maybe 20%, just my experience.

 

I always heard the Holley Spread-Bores combined all of the bad features of a Holley with the unfavorable characteristics of a Quadra-Jet.

 

Maybe we can agree to disagree on this point. Vaporized fuel displaces a lot more volume than liquid fuel. That increased volume of fuel vapor means there is less space available in the runner to deliver oxygen laden air.

Have you looked at an engine designed specifically for methanol? The ports in the head and intake runners are HUGE to accommodate the necessary airflow.

Great strides have been made to design injectors that will deliver more finely dispersed fuel particles and placing the injectors near the intake valve leaves more space available in the intake runners to carry air. A properly timed injector will spray fuel on the backside of the intake valve such that the preponderance of the fine mist of fuel will be largely atomized by the time the intake valve closes, along with that big gulp of air.

 

I think you are missing the fact of the large cooling effect that fuel vaporization supplies leads to a denser air/fuel charge in the cylinder.
By putting the fuel in just before the valve you lose much of the cooling effect.

It's only responsible for the handful of peak power gain the carb shows over fuel injection.

 

I’m not sure about the injector location discussion but in my experience working on a top fuel team; a certain percentage of nitro goes in above the blower and the rest goes in near the ports. At one point, the linkage got screwed up, so the hat wasn’t feeding enough fuel. We started throwing belts because the rotors got hot and seized. I started looking for a frosty blower at the end of each run. Later, I got my own front engine dragster. I ran methanol through a Dominator on top. You could actually see the blower getting frosty in an eight second run.

As for a denser intake charge, I know that at a lower temperature, ALL the molecules are closer together. That allows more molecules of both air and fuel to fit into the same space. On my 57 Chevy, I used the old trick to put bags of ice on top of the intake manifold before a drag race. The 327 became a different power plant, lowered ET by at least two tenths.

 

Anyone remember the " cool cans" where you ran multiple loops of your copper fuel line in a 3# coffee can filled with ice ?

 

Yes sir.