The mighty LSA supercharged V8.

[Robert91RS]

Originally Posted by radz282003

Hypereutectics are better now, I believe. They still aren't as good as forged slugs in the LS9, but they're better than the past.

Originally Posted by Camaro509

Someone with more knowledge about this please set me straight, but I thought
Hypereutectic pistons were inferior to forged pistons where higher power out-put
was concerned? That they couldn't handle some of the power add-ons as well as forged pistons could...

This Wiki quote is very informative.

“Hypereutectic” refers to a metallic alloy which has a composition beyond the eutectic point. In materials science, the word eutectic refers to a specific ratio of chemical composition at which the constituent elements will form a single, homogeneous phase when cooled. Above or below this ratio, separate chemical phases will form during cooling due to insolubility of one constituent in the other. Most metals are not eutectic, and have different phases present in their cooled form. Hypereutectic pistons are made of an alloy of aluminum which has much more silicon present than is soluble in aluminum at the operating temperature. Hypereutectic aluminum has a lower coefficient of thermal expansion, which allows engine designers to specify much tighter tolerances.

The most common material used for automotive pistons is aluminium due to its light weight, low cost, and acceptable strength. Although other elements may be present in smaller amounts, the alloying element of concern in aluminum for pistons is silicon. The point at which silicon is fully and exactly soluble in aluminum at operating temperatures is around 12%. Either more or less silicon than this will result in two separate phases in the solidified crystal structure of the metal. This is very common. When significantly more silicon is added to the aluminum than 12%, the properties of the aluminum change in a way that is useful for the purposes of pistons for combustion engines. However, At a blend of 25% silicon there is a significant reduction of strength in the metal, so hypereutectic pistons commonly use a level of silicon between 16% and 19%. Special moulds, casting, and cooling techniques are required to obtain uniformly dispersed silicon particles throughout the piston material.

Advantages
Most automotive engines use aluminium pistons that move in an iron cylinder. The average temperature of a piston crown in a gasoline engine during normal operation is typically about 300C (600 degrees Fahrenheit) and the coolant that runs through the engine block is usually regulated at approximately 90C (190 degrees F). Aluminium expands more than iron at this temperature range so for the piston to fit the cylinder properly when at a normal operating temperature, the piston must have a loose fit when cold.

In the 1970s increasing concern over exhaust pollution caused the U.S. government to form the Environmental Protection Agency (EPA) which began passing legislation that forced automobile manufacturers to introduce changes that made their engines to run cleaner. By the late 1980s automobile exhaust pollution had been noticeably improved but more stringent regulations forced car manufacturers to adopt the use of electronically controlled fuel injection and hypereutectic pistons. Regarding pistons, it was discovered that when an engine was cold during start-up, a small amount of fuel became trapped between the piston rings. As the engine warmed up, the piston expanded and expelled this small amount of fuel which added to the amount of unburnt hydrocarbons in the exhaust.

By adding silicon to the piston's alloy, the piston expansion was dramatically reduced. This allowed engineers to specify a much tighter cold-fit between the piston and the cylinder liner. Silicon itself expands less than aluminium but it also acts as an insulator to prevent the aluminium from absorbing as much of the operational heat as it otherwise would. Another benefit of adding silicon is that the piston becomes harder and is less susceptible to scuffing which can occur when a soft aluminium piston is cold-revved in a relatively dry cylinder on start-up or during abnormally high operating temperatures.

The biggest drawback of adding silicon to pistons is that the piston becomes more brittle as the ratio of silicon is added. This makes the piston more susceptible to cracking if the engine experiences pre-ignition or detonation.

Performance replacement alloys
When auto enthusiasts want to increase the power of the engine they may add some type of forced induction. By compressing more air and fuel into each intake cycle, the power of the engine can be dramatically increased. This also increases the heat and pressure in the cylinder.

The normal temperature of gasoline engine exhaust is approximately 650C (1200F). This is also approximately the melting point of most aluminium alloys and it is only the constant influx of ambient air that prevents the piston from deforming and failing. Forced induction increases the operating temperatures while “under boost” and if the excess heat is added faster than engine can shed it, the elevated cylinder temperatures will cause the air and fuel mix to auto-ignite on the compression stroke before the spark event. This is one type of engine knocking that causes a sudden shockwave and pressure spike, which can result in an immediate and catastrophic failure of the piston and connecting rod.

The “4032” performance piston alloy has a silicon content of approximately 11%. This means that it expands less than a piston with no silicon, but since the silicon is fully alloyed on a molecular level (eutectic), the alloy is less brittle and more flexible than a stock hypereutectic “smog” piston. These pistons can survive mild detonation with less damage than stock pistons.

The “2618” performance piston alloy has less than 2% silicon and could be described as hypo (under) eutectic. This alloy is capable of experiencing the most detonation and abuse while suffering the least amount of damage. Pistons made of this alloy are also typically made thicker and heavier because of their most common applications in commercial diesel engines. Both because of the higher than normal temperatures that these pistons experience in their usual application and the low-silicon content causing the extra heat-expansion, these pistons have their cylinders bored to a very loose cold-fit. This leads to a condition known as “piston slap” which is when the piston rocks in the cylinder and it causes an audible tapping noise that continues until the engine has warmed to operational temperatures. These engines should not be revved when cold, or excessive scuffing can occur.

Forged versus Cast
When a piston is cast the alloy is heated until liquid, then poured into a mould to create the basic shape. After the alloy cools and solidifies it is removed from the mould and the rough casting is machined to its final shape. For applications which require stronger pistons, a forging process is used.

In the forging process the rough casting is placed in a die set while it is still hot and semi-solid. A hydraulic press is used to place the rough slug under tremendous pressure. This removes any possible porosity and also pushes the alloy grains together tighter than can be achieved by simple casting alone. The end result is a much stronger material.

Hypereutectic pistons can be forged but typically are only cast because the extra expense of forging is not justified when cast pistons are considered strong enough for stock applications.

Aftermarket performance pistons made from the most common 4032 and 2618 alloys are typically forged.

[radz28]

Good find. This might help some people, with extreme worries about the OEM LSA pistons.

Thanks

[Vega]

Originally Posted by Mr. Brownstone

Vega, I agree with you 100% about the mystique of the 427 and the Camaro. I also think GM did it backwards w/ making the Z28 the so called "heavy hitter" w/ the larger engine unlike the Z28's of yore with their high revving little 302's. The nimble little, high revving, Trans-Am racer was the Z28 and the heavy hitting Brutes were the SS396's and the COPO 427's not limited to but including Don Yenko's Bad boys and Fred Gibb's ZL-1's.

I guess Now days its all about marketing and name recognition. Most people ( even the non-motorheads ) know what a Z28 is and they think "Z28...thats gotta be fast!!! but you tell them ZL-1 and they stand there scratching their heads......they haven't got a clue.

So I guess GM is smart to badge their GT500 Killer as the Z28 against some of our wishes.

haha yeah sometimes i get a little carried away and type a lot, but still thanks much, and yeah thats very true, im just not sure if todays market would work with the 60s set-up, i mean everything now is so linear and everyone's looking for the "next best" instead of just a car with different pros and cons so idk i could go for either fashion but the only thing that bugs me with today's idea is that you're gonna be giving your golden right nut for the good stuff, LOL

here's an idea, what if most, if not all, Z/28s were built on an "on-order" basis, where the customer ordering the car got to choose a crate engine and minor mods to each engine (such as cam) for the car to be built with? Are my ideas getting too far fetched yet? What if you could order specific air bags that when they inflate they take the shape of T-pain's head! XD
Yeepp, im gettin there...

[Jinx]

I hope an engine is made using a mixture of the LSA and LS9 in their thoughts.

Basically the LSA's 1.9L supercharger, cam specs, and same build dimensions,
but have in mind the LS9's bottom end strength. Doesnt have to be titanium, but just general forged pieces like a 03-04 Cobra and GT500 would use.

I think that would keep the cost reasonable and mass producable

aka LS8?

[clark17357]

Dragon,

Thanks for the write up. Because you put so much time into it, perhaps you have some information on the intercooler and heat exchanger beyond what is written.

While the intercooler design is touted as something that "raises the bar in both packaging and efficiency," I do not see that design as being able to improve on the more traditional design which has the heat exchanger located away from the motor and the heat produced by the motor.

Maybe I am missing something (and I hope I am as the overall "look" of the unit is very appealing) but this design would not do anything to diminish heat soak and would seem to work in the opposite direction, given its location.

What I have seen of late is a heat exchanger with twin puller fans. You can see it on the Revan Racing web site (revanracing.com). Ignore the fact that it is not engineered for GM products yet but you can see that their approach should apply to any applicaiton, assuming there is room for it.

These big motors throw off a lot of heat and the problem with the 5.4 Ford motors that are supercharged (the motor addressed by Revan Racing) is heat soak. The GT500, as powerful as it is, cannot make its advertised power for a long period; not without something like what the Revan Racing set up does. Is your sense that heat soak is the common enemy with any supercharged motor and, yet, you rarely see it discussed?

Thanks, again, for the write up. The Z/28 is a car that needs to be built. Those of us who ran muscle cars in the 60's remember when the original version hit the streets. Sure would like to see it back, particularly with a power set up like this.

Jim

[99-LS1-SS]

The system delivers 250 kPa (about 36 psi) at idle or low speeds. Yet the electronic throttle management system can almost instantaneously increase fuel pressure to 450 kPa (65 psi) for sustained high-speed operation or wide-open throttle.

How much power do you think the 65 psi injectors will support? I'm guessing around 700 rwhp maybe a little less since it's forced induction. What injectors does the LS9 use?

[Vega]

Originally Posted by Jinx

I hope an engine is made using a mixture of the LSA and LS9 in their thoughts.

Basically the LSA's 1.9L supercharger, cam specs, and same build dimensions,
but have in mind the LS9's bottom end strength. Doesnt have to be titanium, but just general forged pieces like a 03-04 Cobra and GT500 would use.

I think that would keep the cost reasonable and mass producable

aka LS8?

Thats a great idea, my biggest beef with the LSA is its lack of forged parts, although it should be noted that the LS9 is somewhere in the ball part of 530lbs dry, but that'd be assuming we'd use the LS9 as the base, id be more for using the LSA as a base and just adding forged parts and modifying the engine some to up the horses a few

[Mr. Wyndham]

Originally Posted by clark17357

Dragon,

Thanks for the write up. Because you put so much time into it, perhaps you have some information on the intercooler and heat exchanger beyond what is written.

While the intercooler design is touted as something that "raises the bar in both packaging and efficiency," I do not see that design as being able to improve on the more traditional design which has the heat exchanger located away from the motor and the heat produced by the motor.

Maybe I am missing something (and I hope I am as the overall "look" of the unit is very appealing) but this design would not do anything to diminish heat soak and would seem to work in the opposite direction, given its location.
Jim

The intercooler design is pretty exceptional, to tell you the truth.
Here are some pictures of the supercharger/intercooler to start you off:








Where traditional positive-displacement systems (like the GT500) have an intercooler mounted in between the supercharger and the engine block, the LSA's approach is very different, and offers a number of advantages. The supercharger is flipped upside-down, and pushes air UP, into the intercooler brick + intake housing. This design lets the supercharger belt be a little shorter, it allows the intercooler to be far more effeciently designed, and it allows the air to take a straighter path down into the cylinder, resulting in more torque.

It's a water-to-air system, so the heat-exhanger is mounted traditionally -- that is, down with the radiator and oil coolers, etc. As it was written in the article, this design drops the intake temperature over 150 degress...which is very important for durability and performance. I'm sure GM doesn't condone the use of ice, or ice-chilled water...but with an intercooler this efficient, if someone were to cool the liquid down. You would see tremendous power gains, I think.

[clark17357]

Originally Posted by Dragoneye

It's a water-to-air system, so the heat-exhanger is mounted traditionally -- that is, down with the radiator and oil coolers, etc. As it was written in the article, this design drops the intake temperature over 150 degress...which is very important for durability and performance.

Thanks for the clarification. I did not understand it correctly first time around. I thought that, somehow, the H/E was other than where it is and that is what had me concerned - did not see how you could cool the air charge very well.

Very interesting design. I am going to do some homework on it as I had not seen it before. More torque and a cooler air charge is a pretty unbeatable combination.

Jim

[truth411]

Hmm question? If the Z/28 uses the LSA, the LSA does not have forged pistons so how much of a ceiling would one have for mods? I highly doubt 700rwhp from a pulley swap would be wise like the GT-500 boys are doing. Any thoughts?

[GM4lyfe]

Originally Posted by truth411

Hmm question? If the Z/28 uses the LSA, the LSA does not have forged pistons so how much of a ceiling would one have for mods? I highly doubt 700rwhp from a pulley swap would be wise like the GT-500 boys are doing. Any thoughts?

Hard to tell what the max would be. Alot more has to be done to the motor than just a pulley swap, 700rwhp is like 800hp+ at the crank. Currently the LSA is at 556 at the crank at 9psi with 9.1 compression ratio. So it looks like a bump in compression, cam change, pulley swap, full exhaust mods will be needed to acheave those power levels. Also the current H/E and intercooler system will need to be upgraded to.

[Mr. Wyndham]

Originally Posted by truth411

Hmm question? If the Z/28 uses the LSA, the LSA does not have forged pistons so how much of a ceiling would one have for mods? I highly doubt 700rwhp from a pulley swap would be wise like the GT-500 boys are doing. Any thoughts?

No idea what the LSA's ceiling is. The Caddy guys are doing minor mods to get a little over 600 crank hp out of it.

Lingenfelter has a warrantied kit designed to boost power to LS9 levels...they don't replace any internals.

And Hennessy has a kit good for 700hp without replacing any internals...no word on a warranty...though I didn't check very far into it.

Let's put it this way...the engine won't blow up if you do a little modifying.

But I look at it the same as the LS3. But you wouldn't put 600hp through a stock LS3 without worrying, and so you probably shouldn't put 800hp through a stock LSA without worrying. Even the LS9 with all its titanium isn't indestructible........

I personally doubt that the GT500 guys are putting all that power so easily with unaffected reliability...but I can't get any specs on the engine from Ford...they're nowhere near as transparent about this stuff like GM...it would make this discussion so much easier.

[clark17357]

Originally Posted by Dragoneye

I personally doubt that the GT500 guys are putting all that power so easily with unaffected reliability...but I can't get any specs on the engine from Ford...they're nowhere near as transparent about this stuff like GM...it would make this discussion so much easier.

Hi Dragon,

Here is a thread that discusses the blown Ford 5.4 motor and its specs. Does this help?

http://www.teamshelby.com/forums/ind...6919&hl=forged

Jim

[Jinx]

Also, these part of the LSA information article stuck out:

"The LS9s pistons are made of forged aluminum. The key difference in material choice here, is the desire for refinement in the Cadillac application."

"The cam design also reduces operating noise compared to the naturally aspirated 6.2L Corvette LS-3 V-8 by one decibel. While the change might not seem significant by itself, it combines with similar incremental improvements through the LSA that reduce interior noise in the 2009 CTS-V substantially compared its predecessor"

"The camshaft operates the engine's valves, and its design is crucial to both power and smoothness. The torque enhancing benefits of the supercharger allowed GM engineers to develop a "softer," lower-lift camshaft for the LSA, compared to the typical high-rev, high-power super-sedan engine. The LSA cam delivers maximum lift of 12.2 mm for both the intake and exhaust valves. Moreover, the cam lobes are profiled to reduce the amount of time that both intake and exhaust valves are partially open at the same time. Valve overlap is reduced compared the previous, LS2-powered CTS-V, despite the substantial increase in output. The result is smoother operation at low speeds, and particularly at idle."

With these statement, (maybe Im nit-picking) the LSA seems more geared and refined for the Caddy application. With a car like the Z28, I would think the designers would want the things they tried to omit with their design detail with the LSA. Words like a SOFT, SMOOTHER, QUIETER.....isnt what we are thinking when we want to sit idle with a SS with GMPP exhaust next to us.

Im still thinking that an engine made between the LSA and LS9 is in order. GM knows these car will be ran harder on the average than a Caddy. Plus i would hate to think that they would let there own "GMPP" miss out on warrantied upgrades to contend with FRPP upgrades on a GT500. I have faith that GM is smart to do this. They have been so far with the details.

If they push out L99s JUST for automatic Camaros to avoid gas guzzler tax, I believe they would at least expect and prepare for the stress and expectations that the Camaro's breed of customer will put on a Z28.

Making a "LS8" or "mongoose" with forged material (not titanium) and having its power output between 556hp and 600hp would be a good benchmark and insurance against a crippling load of warranty claim. Do it right the first time. At least put it on par with the strength of the GT500's 5.4L and boost its power output a little above to add to the snake's insult.