[Joel Koontz]

I am wondering how much faster an Aluminum Intake will warm up than Iron Intake. Aluminum transfers heat much better so I feel certain it would warm up faster, but I wonder how much faster.

With an exhaust crossover, I think the Aluminum Intake would warm up much faster because if would immediately be exposed to exhaust heat, but I am running Eheads with no exhaust crossover. I am currently running a stock Iron Tri-Power intake. In cool weather it takes quite a while to warm up. I am wondering if an Aluminum Tri-Power Intake would warm up significantly faster.

[mchell]

IMO.....the aluminum heads are dissipating heat more rapidly and this is probably where you are "losing" your heat......the aluminum intake may exacerbate this ....it dissipates heat more rapidly and even tho it may heat up quicker, it may never achieve and hold the temps the iron would

[steve25]

Once the engine temps reach equalibriem (10 minutes of driving), its a moot point.
Both Intakes will be at the same temp.
The bad thing about aluminum is at hot engine shut down when since they are such a good conductor of heat that they will pull heat from the heads and stay quite hot for a loonger lenght of time.

[Cliff R]

I thought after getting my butt handed to me on the other thread that we were supposed to pack ice on the intakes and stop every 10 minutes to put more ice on them so they stay cold?

Seriously, without an exhaust crossover to heat it up quickly, the intake stays cold too long and the engine will not reach optimum efficiency with a "normal" tune in it. I've used a factory iron intake, HO aluminum, RPM, and currently testing a P4B-QJ intake.

From what I can tell, it's more about the actual outside temps and air quality than the material they are made of. All of those intakes take too long to warm up in really cold weather. All of them are fine in hot/humid summer months.

So I'm a +2 for "it's a mute point", any intake will be at about the same temp after 10 minutes or so of driving.

Can't comment on aluminum being a better conductor vs iron. I do know they all get hot enough you can't put your hand on one without any additional help from a working crossover.....Cliff

[pfilean]

For what it's worth in this discussion. Aluminum conducts heat at about 4 times the rate of cast iron. And aluminum absorbs about twice the amount of heat iron does to raise the temperature of a unit weight one degree. But as aluminum weighs about 1/3 what iron does per unit volume it won't take as much heat to raise a given volume of aluminum that one degree. But I'm with the thought that it is all a moot point once the engine is at operating temp.

[Joel Koontz]

Thanks for the replies.

I don't want the intake to get HOT, just to warm up quickly. Once the engine has warmed up, I want the intake it to be as cool as possible.

I suspect that without an Exhaust Crossover an Aluminum Intake will be cooler than an Iron Intake when the engine is running and completely warmed up. Opinions regarding that are welcomed also, but my initial question is regarding which will warm up more quickly.

I think the best scenario for cool weather drivability would be to have an aluminum intake with an exhaust crossover that would be TOTALLY shut off once the engine/intake has warmed up, but since I seldom drive the car in cold temps, I don't plan to install/create such a system.

[Kenth]

You DO want the intake to get hot and stay hot if you want economy, performance and driveability from your engine.

It´s what the engine wants/needs that matters.

Drive your car at highway speeds, stop, put your hand on side of the carb or even on the front and rear intake runners.
Now you see why the crossover is needed.

[Cliff R]

+2

A hot intake is needed to keep the fuel in suspension as it makes it's way from the carburetor to the intake runners.

I doubt if the hot intake really warms the incoming charge all that much considering the velocity that it travels thru the runners. Many of the well educated folks who have been dissecting this topic typically think on a single plane/static environment. I see this all time with this hobby. The events involved with combustion will occur 20, 30, 40 times a second (or more) at speed. Imagine for a moment how fast the incoming air moves thru the entire intake tract when the cylinders are being charged that quickly.

I actually did a test yesterday with my own engine. Without a working crossover it took 30 minutes to heat soak the intake to achieve the highest idle speed, and smooth idle in and out of gear. Outside temps at the time of the test was 27 degrees.

Even after 30 minutes of running time to heat soak the parts, there was still a LOT of vapor in the intake system when we removed the carburetor. The entire inside of the plenum areas were wet. This happens as a significant amount of the fuel in the intake charge condenses on the cool metal parts and comes out of suspension. The same test done with the outside temps above apprx 50 degrees will show a bone dry intake when the carb is removed, telling us that all of the fuel in suspension is making it's way to the combustion space.

We are back to that thermal efficiency deal that I got slammed for on the other thread. In a wet flow system, we are trying to burn a mixture that is WAY below the LEL (lean). Any lean mixture is going to need to be heated up, and the fuel molecules well atomized for complete combustion.

It would be nice if we could do ALL of this within the cylinders (direct injection). This way we could run cold intake systems, ice cold incoming air, and increase cylinder filling to make optimum power. As good as that theory is, doesn't work so well in practical application, as we don't see too many gasoline engines out there that use direct injection systems. I think the 4 cylinder engine that powers the Chevy Equinox is one of them, there may be others, but my knowledge with modern vehicles is limited.

With older carbureted vehicles the intake needs to be hot, or you will loose efficiency, and a richer incoming mixture will be required for complete combustion. A cold intake will also hurt idle quality more than it will induce running issues. Idle rpm, and quality will continue to improve as the intake gets hotter. Once it reaches a temperature where fuel no longer condenses on it, a much leaner mixture will be needed to achieve smooth idle quality, and the lowest rpm change in and out of gear.

I did that test yesterday as well, and backed out the mixture screws 3 additional turns on a dead cold engine. When the choke came off the fast idle at 3 minutes, the engine idled pretty good (intake was still ice cold to the touch). At the 30 minute mark it was pumping out tons of unburned fuel (rich), and the mixture screws had to be put back at there original settings (50 rpm lean tip-in, then backed out 1/4 turn).

Some additional food for thought as it relates to this topic.......Cliff

[David Jones]

Cliff, for what it's worth, my experience exactly mirrors what you have been posting.

I run a Q-jet with no choke. Have for years. Edelbrock P4B-QJ. 6X heads with the crossovers filled. Probably about as "worst case" as one could get in the warm it up wars.

If it's under 50 degrees out I need to plan on 15-20 minutes of driving time before my car drives "normal". The colder it is the longer it takes. For the 1st few minutes the idle is very erratic. Beyond that it takes 15 minutes before the engine feels like it is really interested at lower rpm. As it warms, the closer it gets to operating temp (not just water temp), the happier it feels.

Get it out at 65-70 degrees or above and it's a whole different animal. By the time you have water temp it runs like a champ.

.....and I wouldn't change a thing.

[72LuxuryLeMansLa.]

Originally Posted by David Jones

Cliff, for what it's worth, my experience exactly mirrors what you have been posting.

I run a Q-jet with no choke. Have for years. Edelbrock P4B-QJ. 6X heads with the crossovers filled. Probably about as "worst case" as one could get in the warm it up wars.

If it's under 50 degrees out I need to plan on 15-20 minutes of driving time before my car drives "normal". The colder it is the longer it takes. For the 1st few minutes the idle is very erratic. Beyond that it takes 15 minutes before the engine feels like it is really interested at lower rpm. As it warms, the closer it gets to operating temp (not just water temp), the happier it feels.

Get it out at 65-70 degrees or above and it's a whole different animal. By the time you have water temp it runs like a champ.

.....and I wouldn't change a thing.

My P.O.S. 350 operates the same way except I have a working choke and crossover. Since my choke works I don't have to play with it once it starts running on fast idle but at around 50°F and below it has to warm up for 10 minutes at least before it will slow idle and it takes a few miles of driving before the throttle response is normal. When I finally build and install my new engine with the blocked crossovers in the 6X-4 heads I'll post back with my thoughts on the difference.

[Cliff R]

Thanks David, good info.

I also ran my q-jet for many years without a working choke, and no heat thru the crossover in the intake. I also had the carb set up to run straight off the jets, and no primary metering rods. I only recently added the choke, and put the metering rods back in the carburetor. I like the instant cold starts and fast idle feature. Maybe I'm just a tad more impatient these days than in my younger years, or just like things to work better all the way around......Cliff

[Kenth]

It takes some time to understand the principles of the combustion engine, once the understanding is there, everything about it is so much easier.

What is not so hard to understand is why a 40-50 year old engine, never opened, is full of carbon, soot and burnt oil.
This is mostly not the case with a newly rebuilt, well maintained, enthusiast engine.
Keyword here is maintainance.

And, as knowledgeable as D W is i´m sure he´ll agree to use the crossover on a street engine for street usage.
Running an engine on the dyno does NOT mirror running an engine on the street.

[tpssonic]

DI is alive and well and living in the two-stroke world.

http://www.youtube.com/watch?v=eu3NEPSBfUs

Back to reality with our multi-decade old carbs- which really aren't so bad and do a pretty good job of atomizing (breaking down the "globs" of fuel); emulsifiing it (mixing with air) and then vaporizing it (changing into a "rarefied" or less dense form) the air/fuel charge. Maximizing surface area is the key here. As mentioned before, the Q-jet carb typically gets better fuel mileage because the smaller primary bores have higher velocities, which in turn providethe shearing/ breaking up (atomization) of the fuel. What's more, in the intake there is a great deal of vacuum that causes the air/fuel emulsion to change state (liquid emulsion to gas, due to the lower air pressure- see Ideal Gas Law). During this phase transition (basically refrigeration by evaporation) there is a huge refrigeration effect on the intake system (witness the frost accumulation on methanol-fueled engines even running in the summer). HEAT IS NEEDED to counteract this cooling effect on the intake, even though the mixture is traveling at high velocities, heat exchange is occuring. On the mechanical side of fuel atomization, I have run across two stroke carbs that do a masterful job of atomizing fuel. They allow the production of HUGE cold-shot horsepower on the dyno with the EXACT SAME air/fuel ratios AND carb/engine/ambient air temps that a lesser-able carb would only muster an engine stumble and even piston seizure. Bottom line, if the the carb can't break up the fuel, it needs heat to do it. If the aluminum dissipates the heat faster than it absorbs heat in comparison to iron, it will take longer to warm up. If it doesn't, it won't. Helpful, huh?

[Cliff R]

+2

You do NOT want a cold intake manifold when it comes to this topic.

I also have several two stroke applications that put a provision in the air cleaner assembly specifically for cold weather operation. They route a portion of the intake air into the carb from the P/C fins to heat the incoming air charge. This helps engine efficiency by keeping the fuel in suspension, probably offsets the refrigeration effects mentioned above. Not sure about all the tech stuff, I just know how these things work from the user level.......Cliff

[J.C.you]

I realize this is the street section, but a cold intake under running conditions makes a case for runners to have this type texture.

[Bruce Meyer]

Im glad I live in Phoenix. We don't need no steenkin choke!

[Cliff R]

-6 here this morning, as a test I fired up the 455 in the Ventura. Two pumps on the gas pedal and it roared to life, sputtered momentarily, and died out once. Fired right up on the second attempt and idled nicely at 1400rpms. As well as the engine is tuned, it absolutely REFUSED to idle even after running on the fast idle for nearly 20 minutes. The intake manifold was still cold to the touch, and the carb baseplate was ice cold/frosted up some.

We shut the engine down and let it heat soak about 10 minutes, and it fired right up and idled nicely at 750rpm's.

I was interested in the comments above about the refrigeration effect, and how an engine with an aluminum intake and no crossover would operated in weather this cold, which was very poorly until the intake heated up some........Cliff

[72LuxuryLeMansLa.]

Ok. We are dealing with a stock application here and I am a big proponent of everything working the way it was designed....to a point....I insist on dual exhaust
I understand that there needs to be heat on the intake to keep the fuel atomized. What temperature is needed? If you are beyond a stock application, like higher compression and so forth, Is there a point where the intake is too hot? I'm wondering if say 150°F-300°F is good but say over 500°F is a bad thing.........(I just made up the numbers for the sake of the question.)
I am not arguing a point here......I'm just trying to gain some knowledge.

Thanks!

[tpssonic]

"realize this is the street section, but a cold intake under running conditions makes a case for runners to have this type texture."- J.C.you

Exactly! This "texture" promotes turbulence and additional atomizing/emulsifying of the charge. In dyno tests (again, 2-stroke engine-speak spoken here, but it should apply to similar internal combustion engines), we saw decrease in power FROM STOCK with (smooth-finish) extrude-honed intake ports. Roughen them up and bingo- increase in power from stock. More importantly, it helps both street and race engines.

[tpssonic]

"-6 here this morning, as a test I fired up the 455 in the Ventura. Two pumps on the gas pedal and it roared to life, sputtered momentarily, and died out once. Fired right up on the second attempt and idled nicely at 1400rpms. As well as the engine is tuned, it absolutely REFUSED to idle even after running on the fast idle for nearly 20 minutes. The intake manifold was still cold to the touch, and the carb baseplate was ice cold/frosted up some."

Cliff, if you can get that engine to fire and run that quickly in -6F (it was -10F when I went to work today, so OH is not the suckiest place in the Good 'Ol USA today), then it will work wonders at normal human temperatures, but you don't need me to tell you that. That is why I am on the current Cliff Q-jet wait list.

Real-world testing does have it's place (actually, it's what I prefer). At the point it can be supported quantitatively, it become much more useful because it can then be used to predict behavior. When it can't, we simply didn't do our homework, and it's back to the drawing board... and back to more real-world testing.