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Misunderstandings about intercoolers and carbureted superchargers
by moore1 | Dec 5, 2018 | News | 1 comment
Misunderstandings about intercoolers and carbureted superchargers
By Chris Beardsley:

Unlike port fuel injection systems, carburetors have a unique advantage while operating on boosted engines without an intercooler.

Chris Beardsley
In carbureted applications, the air charge from the supercharger is significantly warmer than ambient air. When warmer air is forced through a carburetor, the atomization process is enhanced as the cool fuel mixes with it. Ever try starting your carbureted engine in the dead of winter? Now compare that to a hot August afternoon. The warmer air of the supercharger blowing through the carburetor amplifies the atomization process. The result of superior atomization is a cooler, denser air charge under pressure.
The warmer air mixing through the carburetor does something else just before it cools. The heat acting on the fuel causes the fuel particles to disperse—a chemical explosive process that sends fuel in every direction with violent force. When this occurs at the entrance to the plenum, each intake runner is filled with a more evenly balanced mixture of fuel and air that enters the cylinders. Naturally, cylinder-to-cylinder distribution affects horsepower. For these reasons, the ample performance of carburetors incorporated in boosted projects without an intercooler is evident. Even common pump fuels generate impressive power, and increasing ignition timing can further the power potential using these principles.
“But intercooling is better,” I hear you say. “What if I add one of those?”
While intercoolers have their place in boosted performance, for most carbureted applications adding an intercooler works against you. It looks fantastic and its associated plumbing enriches any engine compartment.
But, by directing the air charge through an intercooler to feed the carburetor, we lose its natural heat and associated benefits during the atomization process. The intake air charge lacks the density, the distribution or the balanced fuel mixture of a simple direct flow system.
“Yet, with the intercooler the air is colder, right?” Yes, technically the air charge might be a few degrees colder. Air reaching the carburetor without intercooling typically reflects intake temperatures of 60-70 degrees below the throttle blades compared to intercooled temperatures that may be 10 degrees cooler. But they enter the carburetor around 100 degrees cooler. Relinquishing this amount of heat weakens the atomization process and the distribution. The slightly cooler air temperature does not recover the loss of these other consequential factors.
In the case of operating a supercharger with a carburetor, run the air straight in and enjoy its inherent hidden benefits, including the cost saving and complexity of the intercooler.
Source:
TorqStorm Superchargers
TorqStorm.com
Telephone (616) 706-5580 or visit www.TorqStorm.com or e-mail the knowledgeable Beardsley at: sales@torqstorm.com

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Sounds kind of on the order of Smokey Yunick's hot vapor engine.

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Official Cookie and Mater Tormentor.

So I guess the cold air intake that I fabbed up for my TorqStorm kit is counter productive as well. But, as Chris said, the plumbing looks cool anyways. I'm thinking that the ram air tube is worthless too. That's what you get from a homer, haha.

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Cheers, Bill.
Smoke em if you got em.

I don't think so. The cold air intake will bring a cooler, denser charge to the supercharger that will then heat the air/fuel charge. Sounds good to me.

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“Buy the ticket, take the ride.”
― Hunter S. Thompson

I'm not buying the quoted no inter cooler solution in every case. In some cases that suffer from low ambient air temps, poor manifold fuel distribution, etc issues, maybe. I don't think the author made a strong case for his argument.
In any case, an air to air inter cooler never gets the charge air down to ambient air temp anyway, which is what a normal NA carb has to deal with 100% of the time in the first place. If this was a solution, people would be adding inlet heating solutions, rather then .cold air

The McInnes book says the same thing. It also states there in no advantage to intercooling until you are over 10lbs of boost. Corky Bells books suggests that intercoolers were always advantages. But Corky was in the business of selling turbo kits, that included intercoolers.

I thought the article referenced was in regard to superchargers which would not impart the same degree of heat to the charge that an exhaust driven turbocharger would. I think it makes sense and the Smokey Yunick homogenizer, hot vapor engine that 'zilla referenced was of the same thinking.
Lou, are you intercooling or not intercooling your supercharged engine?

_________________
“Buy the ticket, take the ride.”
― Hunter S. Thompson

I have never run a conventional intercooler. I have been up to 14-15 psi boost. I use methanol/water injection (-20F windshield fluid from parts store). I have a conservative tuneup I am sure, but then I drive 100s or 1000s of miles and race and drive home. Intercooler piping and cores are a paid to fab and can impart large restrictions, which I learned from Cameron Tilley on one visit. Also, not much air will pass over an air-air intercooler in a drag application until the top half of the track and then it's all over a few seconds later. For road racing, high boost, land speed, or other sustained applications, I can certainly see the benefit. Water-air intercooler would be more immediate for drags and is likely much better for lower speed apps like autoX. Bigslant6fan has/had a water-air setup on his Barracuda.

I have a stack of used air-air intercoolers I have bought cheap over the years that are collecting dust... Anyone want one?

I plan to run the same AEM meth/H2O injection on my Torqstorm setup with port EFI and no intercooler. Boost will be 12 psi max.

Lou

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Home of Slant6-powered fun machines since 1988

I always thought one of the issues with positive displacement superchargers is they are always beating the air, ie heating it up, whether its moving air or not, a turbo has a much less problem with that. Seems like meth/water injection is a work around, not a solution. If this heated air was such a plus, wonder why more positive superchargers aren't set-up with blow thru carbs. I Believe drag guys have intercooler misters for temporary low air flow conditions. Intercooler tubing restrictions means one might have too long of flow and/or an undersized intercooler, but then every solution has a downsize, and lag might be one drawback?

I do agree intercooler effectiveness/usefulness is very related to the boost run.

Compressing air heats it up. It doesn't matter what is doing the compressing. Cooling the air requires a radiator or injecting a cooling agent. An intercooler is just a radiator. A draw thru system uses the atomized gasoline passed thru a venturi to cool the air. The same principle, different methods to achieve the desired results.

To be clear I never said it did. My point was, different devices have different efficiencies in compressing air, and those less efficient, add more thermal energy mechanically to the air being compressed more so then those more efficient, increasing the air temp more so then just the process of compressing the air, hence my earlier comment.

Your examples above of cooling air are well known and accepted, the topic in this thread centers on why both together cannot show a better result then just one alone, I believe.

Ok, a carburated draw thru system is so efficent in cooling the intake charge that it will ice up the plenum. Do you need to add additional cooling? GM added waterheated plenums to counter this problem.

Is a carburated blow thru system just as effective, or do you need to add additional gadgets such as intercoolers or water injection?

When I did my draw thru turbo, back in the late '70's, I had a problem with the carb adapter iceing at idle. Had to add heater water to the bottom of the adapter.

_________________
Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225