Skeedatl

Nope. The motor will only take in air so fast as pointed out. It's the natural density of the air and the airflow as determined by the MAF sensor the determines the mixture.

What happens at automotive speeds, is the "tube" leading the intake will fill to the point of static pressure, then "overflow". Any additional air meeting the intake will not enter. To the airstream the intake is a solid. That is until you go fast enough for the compression to be qualitative...which I claimed was around Mach .5. At this point, you start pressurizing the intake charge. MAP sensors will see a constant pressure up until this point. Only after there is compression will the MAP sensor start to trigger additional fuel. Before this, the MAF is the main determining factor as to how much fuel is added, since MAP is fairly constant.

That being said, the "effort" spent by the engine drawing in air is negligable at best. The work is done by the static pressure force native in the air. You create a vacuum, it will natually be filled by the static pressure of the air.

A 1.8% increase in pressure is nothing compared to the 15PSI of vacuum present in a typical motor. Whether the pressure is gonna be -15PSI at the manifold of -14.95PSI...that translates to no difference in HP.

harddrivin1le

A side by side comparison, where all variables were fixed (including fuel octane) and where only compression ratio and head materials were the variables, is the only way of disproving what many call "the aluminum head myth."

Skeedatl

There is no such thing as the aluminum head myth. Everyone "normal" racer knows that iron heads hold more head than aluminum.

What's next, the radial tire myth...that slicks hook up better than radials?

It's one of those duh, what did you think statements.

harddrivin1le

But that 1.8% increase is LARGER than the difference in delta P between a K&N filter and a paper media filter....

And 1.8% of 15 (isn't actually 14.7?) is .27 psig, not .05 psig as you showed.

Yet, you claim K&N filters make more power while dismissing ram air as a "myth."

Skeedatl

Why don't you READ the posts?

Paper filters only maintain that effeciency when new. After a very short while the difference is MUCH larger.

Take a look at a paper filter with 10 or 15K miles on it compared to a cotton filter. The paper filter will be reduced to minimal airflow while the cotton filter flows just as it did clean.

Why is this concept so hard for you to follow? Cotton filters are about when they're new, it's about their service interval...they simply maintain high efficiency infinately longer than paper filters do.

If you want to change out your paper filter every 500 miles...be my guest...you'll then be able to barely keep up with the flow of a cotton filter.

Swat Dude

That is why the experiment he references is flawed. The guy only drove the car 500 miles. I would like to see what happened to the pressure losses at 15,000 miles.

harddrivin1le

Why is it so hard to follow that I don't run air filters for 15,000 miles?

And any K&N I've ever had is FILTHY after ~ 5K miles.

And you're wrong when you state that engines don't make "an effort" when drawing air into the cylinders.

That "effort" (actually a pumping loss) is LARGE at anything less than WOT.

Skeedatl

Even then they don't measure particulate size. They don't control the environment they were driving in. It was a complete joke. They must be getting their degrees from Cracker Jacks or something. None of my profs would have tolerated such a flawed experiment.

harddrivin1le

I don't keep ANY filter in a car for 15,000 miles.

I've used K&Ns on past vehicles and they are FILTHY @ 5,000 miles.

Skeedatl

Filthy doesn't mean restricted air flow in a cotton filter like it does in paper.

That's the point of a cotton filter.

harddrivin1le

Just like the "aluminum heads make more power because they allow more compression" argument that you make.

There are virtually ALWAYS other variables involved (port size and shape, to name one and weight reduction of the vehicle, to name another), yet you attribute any perceiveable gains solely to the increased compression permitted by aluminum.

Skeedatl

No, the mathematics modeling software built into programs like Engine Analyzer Pro control ALL the variables. On a 400HP motor, 1 point increase in compression ALONE is 20 horse.

harddrivin1le

That software shows that changing the material of the heads (from iron to aluminum), plus a corresponding bump in CR (while remaining within the boundaries of a given octane number fuel) will result in more power without changing anything else?

It doesn't show that.

You know it and so do I.

harddrivin1le

ASSUMING THE SAME HEADS (AND SAME MATERIAL)!!!!!!!!!!!!!

That scenario no longer exists once you CHANGE MATERIALS (which have vastly different thermal conductivity values)!

And you've yet to show me that merely switching MATERIALS (iron to aluminum) permits a full 1.0:1 gain in compression ratio with THE SAME OCTANE fuel.

Such a gain is not evident in new cars and I've already given you examples.

My Accord V6 runs a whole 0.6:1 higher Cr than GM's 3.8 liter V6 on the same 87 octane fuel, despite the fact that the Accord uses 4 valves/cylinder and ALUMINUM heads.

harddrivin1le

All other things being equal (except head material and CRs) and assuming a given octane fuel operating right at "the safe limit" (e.g. 92 octane):

The engine equipped with the aluminum heads can tolerate a SOMEWHAT higher mechanical compression ratio.

That's due SOLELY to the fact that aluminum can dissipate ALL of the additional heat MUCH more efficiently (factor of ~ 3.5).

But the resulting PEAK DYNAMIC CYLINDER PRESSURE (and hence, POWER) will be THE SAME. EVERYTHING that was "gained" by the additional mechanical compression ratio goes out the window in the form of heat energy!!!

harddrivin1le

All other things being equal (except head material and CRs) and assuming a given octane fuel operating right at "the safe limit" (e.g. 92 octane):

The engine equipped with the aluminum heads can tolerate a SOMEWHAT higher mechanical compression ratio.

That's due SOLELY to the fact that aluminum can dissipate ALL of the additional heat MUCH more efficiently (factor of ~ 3.5).

But the resulting PEAK DYNAMIC CYLINDER PRESSURE (and hence, POWER) will be THE SAME. EVERYTHING that was "gained" by the additional mechanical compression ratio goes out the window in the form of heat energy!!!

Here's a good link on compression ratios, complete with a formula that you'll love:

http://www.popularhotroddingweb.com/...power_squeeze/

Skeedatl

Bzzzzz, wrong again.

I'm finished wasting time with you. I've already explained why you're wrong about a zillion times and provided the data to back it up. If you don't get it by now, you never will. Pffft, and I thought that you were actually interested in knowing the truth.

Swat Dude was right the whole time. Too bad I wasted so much time on you. But that's my flaw...trying to get people into the sport and understand the WHY for yourself rather than just vomiting up other people's B.S. like you do so much.

Save the cut n pastes for your scrap book.

harddrivin1le

No, I'm not wrong.

Aluminum heads permit a higher MECHANICAL compression ratio (than the otherwise identical iron head, with the same octane fuel, operating right near the limit of detonation).

That doesn't translate into higher dynamic cylinder pressure and therefore doesn't result in ANY more torque (or power).

When switching to aluminum heads (where everything else is equal), one has to RAISE the CR in order to prevent a POWER LOSS!

http://www.hughesengines.com/general..._head_tech.asp

Aluminum heads dissipate (get rid of) heat much faster than iron heads. The rapid heat loss from the combustion chamber results in reduced combustion chamber pressures (heat equals pressure); similar to the effect that lowering the compression ratio lowers cylinder pressure. When switching to aluminum heads you MUST raise the compression ratio to prevent a power loss. This is a good opportunity for our customers to take advantage of our computer calculated compression ratio service. This software assures them of getting the maximum power out of their purchase; it's a no-charge service for our customers.

Aluminum heads will not automatically create more power than iron heads unless they flow more air and are installed on a higher compression ratio engine. In cases where you have a decent port job on a set of iron heads it is possible to bolt on a set of out-of-the box aluminum heads and lose power. Aluminum is automatically lighter but not faster. Yeah, yeah I've read all of those magazine articles that told you how they installed brand X widget and picked up 500 HP and 4 seconds in the 1/4 mile (we have even been the victim of these articles). What you must keep in mind is that those magazines and the writers (???) are paid by the advertisers, not by that $19.99 you send in once a year. So you can expect that advertised products always look good even when they screw the test up and the "results" are not what they should be, (been there done that!). They are under a deadline and the rent has to be paid so the facts sometimes take a back seat. In some cases the engine would have produced more power with a set of well ported, iron heads, and at a lower price.


Quick Facts: Aluminum vs Iron


Weight: Aluminum heads weigh about 45 to 50 lbs., a pair, less than iron heads
Durability: "Ported iron heads can crack if the engine is badly over-heated". Yes this is true, but if the engine got that hot the aluminum head would have melted or been badly warped. The seat rings would have also fallen out, but the head might not crack. Anyone who lets his engine get that hot deserves to buy new heads or have an expensive repair bill
Reparability: This is a trick question. Yes, aluminum heads are easier to repair if the damage is very bad and that is a good thing because they are much more fragile and more prone to damage than a hard, iron head
Cost: Aluminum heads cost more, and then there may be the hidden cost of raising the compression ratio
Airflow: You get very similar airflow results from ported, stock heads and "stock replacement" type heads. With raised port cylinder heads, the sky is the limit
Power: Power depends on what you have to start with, or what else you plan to do to the engine. If you have low compression (9.5:1 or less) and are not going to change pistons or mill the heads to restore the cylinder pressure, save some money and go with the ported iron heads. If you are starting on a fresh engine with higher compression ratio pistons, want to lose some weight and the budget can handle it ---go ported aluminum. There is another power consideration; most of the aluminum heads have a closed combustion chamber which is far superior to the OEM heads with their open chamber design. However, if the piston is not at 0.000" deck, the chamber design has very little effect.

If all this sounds like we don't like aluminum heads, the truth is quite the contrary. Aluminum heads are cleaner, easier to port and they look trick next to an iron head. If you make a mistake on an aluminum head, it is easy to fix. If you drop it on your toe it doesn't hurt as bad. Porting aluminum also keeps the shop cleaner, what's not to like? We just want you, our customer, to get the right cylinder heads, iron or aluminum.

harddrivin1le

You are WRONG about aluminum heads making more power.

I've posted ~ half a dozen links explaining why you are wrong and most of them are from people who SELL ALUMINUM HEADS.

All other things being equal (except for compression ratio and materials), aluminum heads will make NO MORE POWER than their iron counterparts when both are running the same octane fuel.

Skeedatl

Oh boy...you don't even understand what you're reading.

The increase in compression MORE THAN MAKES UP FOR THE HEAT LOSS. If you can't grasp this elementary concept, you are a lost cause. You don't understand the mechanics of heat, nor fluids so me showing you the mathematics isn't going to help just as it didn't help you get off your WS6 ram air B.S.

When you actually take physics and fluids and actually UNDERSTAND how internal combusion engines function you will realize how big a fool you are.

This time I really am through with you. Enjoy your ignornace.

harddrivin1le

If you bothered to read my posts you'd see that I've said that ~ 2 dozen times.

"makes up for" is not synonomous with "makes more power."

But it doesn't "MORE than make up for." You just THINK it does. You've yet to produce a single valid source which backs that claim.

In the context of this conversation (where all variable are fixed unless otherwise noted), aluminum heads are "self cancelling" in that the increased compression they allow goes right back out the window in the form of ADDITIONAL HEAT ENERGY conduction through the heads.

The net gain in power is ZERO.

Again, where everything else is the same and for a GIVEN octane fuel operatring "near the limit" (of detonation) in both cases.

Skeedatl

:lol1: LOL, you go right on believing that drivel. Mathematical models have already shown you incorrect. Bathe in your ignornace while the rest of us laugh at you.

harddrivin1le

PROVE what you've stated.

You can't.

Even the people who make money SELLING aluminum heads don't make the claims you make.

The modestly higher CRs permitted by aluminum heads do NOT "more than offset" the additional heat transfer that occurs across the heads. Rather, the two are EQUAL, meaning that the net gain in dynamic cylinder pressure (and torque/power) is ZERO.

harddrivin1le

Who else is laughing?

What "mathematical models" are you talking about? Do you have a mathematical model that allows you to adjust for cylinder head material and the additional CRs such materials might allow for a given octane fuel? No, you do NOT.

You're focused solely on MECHANICAL compression ratios and are IGNORING what actually matters (dynamic compression ratios).

Skeedatl

Again with the modestly higher CR. Nice fiction there. It's not modestly, it's substantially.

The vastly higher compression ratios permitted by aluminum heads build more than enough horsepower to offset HP lost to heat.

If you can't understand this extremely simple concept. You never will.

harddrivin1le

PROVE IT.

Skeedatl

Yes I do dumbass. Engine Analyzer Pro allows substitution of materials for THE EXACT SAME HEAD CONFIGURATION.

Who else is laughing...EVERYONE.

You are a joke on this forum. Everyone loves watching you trip over yourself time and time again.

harddrivin1le

PROVE IT.

The additional RISE in mechanical compression ratio is TOTALLY cancelled by the additional heat that is transferred out of the combustion chamber.

Despite the higher mechanical CR, the dynamic CR s THE SAME (assuming equal octane fuel and otherwise identical heads).

harddrivin1le

The exact same head configuration...

but changing to a DIFFERENT MATERIAL (iron to aluminum)...and with the same octane fuel....?

You're neglecting resulting dynamic compression ratios (and the higher octane that would be required to support those higher crs.).

harddrivin1le

I hear crickets...

What about the term, "THE SAME OCTANE FUEL" don't you understand?

See, the required octane # is dictated by the DYNAMIC compression ratio of the engine and NOT the mechanical compression ratio:

http://www.popularhotroddingweb.com/...power_squeeze/

harddrivin1le

DYNAMIC COMPRESSION RATIO (not mechanical compression ratio) is what determines the required fuel octane rating.

Just because an aluminum head allows a higher MECHANICAL CR does not mean that is yields a higher DYNAMIC CR:

Skeedatl

No I'm not. You don't even know what dynamic compression is. You just cut and paste nonsense and irrelevant graphs.

You don't even understand what you're reading.

harddrivin1le

Unlike you, who provides NO EVIDENCE WHATSOEVER.

You "model" doesn't mean SH!T in the context of this "discussion" (which you prefer to turn into a flame war) UNLESS the model allows you to compare DYNAMIC COMPRESSION RATIOS and takes into account required fuel octane.

Sure aluminum can yield a higher dynamic CR (and make more power) with 93 octane than iron can with 87 octane.

But that's not what I'm talking about.

I'm talking APPLES TO APPLES. SAME GAS, both heads operating "right near the detonation limit."

Skeedatl

What you're posting doesn't show anything. You don't know what the detonation limit is. If course your graphs ignore the most basic variables such as timing, but you wouldn't know that. You just make up these limitation as you go.

You're running under the false assumption that Chevy's 3.8 and Hondas 3.2 are running the highest CR's possible.

You're logic is flawed from start to finish.

harddrivin1le

Again.

What about THE SAME GAS (i.e. OCTANE RATING) don't you understand?

Anything that aluminum allows in terms of added MECHANICAL compression ratio it GIVES UP in the form of heat energy. The resulting DYNAMIC compression ratio is therefore THE SAME.

Again.

With the SAME GAS - operating "near the limits" of the rated octane number.

And if aluminum heads permitted "vastly higher" (mechanical) CRs then we'd SEE IT in the cars that are being sold today.

Anything that's running much more than 10:1 needs 91 octane or better to produce the rated peak power and torque values.

The new LS2 is running 10.9:1 and that requires 93 octane!!!

Meanwhile, GM's 3.8 runs 9.4:1 wih 2 valves/cylinder, an IRON block and 87 octane.

harddrivin1le

Again.

What about THE SAME GAS (i.e. OCTANE RATING) don't you understand?

Anything that aluminum allows in terms of added MECHANICAL compression ratio it GIVES UP in the form of heat energy. The resulting DYNAMIC compression ratio is therefore THE SAME.

Again.

With the SAME GAS - operating "near the limits" of detonation for the rated octane number.

And if aluminum heads permitted "vastly higher" (mechanical) CRs then we'd SEE IT in the cars that are being sold today.

Anything that's running much more than 10:1 needs 91 octane or better to produce the rated peak power and torque values.

The new LS2 is running 10.9:1 and that requires 93 octane!!!

Meanwhile, GM's 3.8 runs 9.4:1 wih 2 valves/cylinder, an IRON block and 87 octane.

harddrivin1le

I am still trying to digest your claim that aluminum heads permit "vastly higher" compression ratios. Please define "vastly higher" and cite valid documentation to support it.

Even if they did, that wouldn't be relevent to this discussion, since the "gain" would be lost (again, assuming the SAME OCTANE FUEL) due to the superior heat transfer properties of the aluminum.

And what about your claim that engines don't make "an effort" when drawing air into the cylinders? What happened to that claim? The effort is LARGE @ anything less than WOT, due to restriction caused by THROTTLING. The last time I checked, most people driving on the street don't always drives @ WOT.

That's one main reason why Diesel engines yield better fuel economy than their gasoline counterparts - Diesels have NO THROTTLING restrictions!!!

Skeedatl

Engine Analyzer claims I can up the compression 3 full points, and it builds 12% more horsepower than the EXACT SAME MOTOR with iron heads. With iron heads the notes claim detonation, BUT a 17% increase in power should the detonation be tolerated.

Thusly, while iron heads would have made more power in this model, they can't be run in in the REAL WORLD because of detonation...HOWEVER, it's also showing that there is a NET horsepower increase of 12% with the higher compression and aluminum head swap, indicating 5% of additional energy is lost by the material as heat.

This is also shown by a 6% drop in HP by ONLY swapping to aluminum...this can only be explained as drop in HP due to head loss since fuel, EFI pulse, cam, everything else is the same.

So while it is true that iron can make more power than aluminum for a given motor and fuel, it is not true that the permitted increase in compression isn't enough to overcome the energy lost to heat.

Run it in your software yourself. Mathematical models are all we have to go by since there is no REAL WORLD iron and aluminum castings that are identical.

You and your articles claim .5-1.6 CR increase is possible by swapping to aluminum, but the mathematical models say differently. And since there is no real world example showing your case correct, while my friend is able to boost way higher than me with not the exact chamber design, but similar head flow indicating that the amount that pre-ignition is controlled by aluminium heads is far higher than you claim.

Now, if you can understand that, or don't want to, that's fine. You don't race or build motors so it doesn't matter. Me, it does matter as I'm spending money on it, and my crap has to work since I don't have a big budget to experiment. I see what works at the track, try and understand the mechanics behind it, do some math, run some models, and spend the money.

Thus far it has my in the 10's on pump gas and iron heads with a turbo V6...not an easy feat let me assure you. And I'm one of the fastest pump gas car guys I know turbo or non-turbo, V8, V6 or otherwise.

harddrivin1le

You keep ignoring dynamic compression ratios and the related OCTANE REQUIRMENTS. What OCTANE would you require to run that kind of compression?

Show me ANY gasoline engine that is running ~ 13:1 on 94 (or less) octane pump gas.

The new LS2 is running 10.9:1 on 93 octane...It will tolerate less, but that invokes spark retard.

Nothing I've posted (that I'm aware of) says that a 1.6:1 increase in compression is possible merely by switching to aluminum heads and a higher CR - UNLESS a higher octane fuel is used.

That's not "apples to apples."

harddrivin1le

GM's 3.8 liter V6 is running 9.4:1 with iron heads using 87 octane fuel.

Show me some engines equipped with aluminum heads that are running 12.4:1 (or better) on 87 octane.

I'll even spot you 4 valve head layouts.

Show me some.

ROTFL