kormrider
ALFISTA BALILLA.
- 18 Gennaio 2012
- 31,538
- 20,636
- 181
- Regione
- No Italy
- Alfa
- 75
- Motore
- 2.0 Twin Spark
- Altre Auto
- Alfa 75 1.6 IE (1992-Battesimo con Alfa)Panda Nuova 1.2 - Ford Ranger LIMITED 3.2 TDCi
Origine motori a benzina Giulia
- Autore discussione paolo_
- Data d'inizio
che tristezza...un po' come il vecchio JTS? che cosa c'è di caratteristico dell'alfa romeo? non certo il motore
M
marcob156
Utente Cancellato
telaio e comportamento sportivo per fortuna.
però a me quel suono non piace per niente. la prima volta che ho sentito lo stelvio benzina pensavo fosse il 2,2 diesel
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BIOHAZARD
Super Alfista
confermo ho montato marmita remus racing... ora è una furia si sente da 3 km di distanza ahahah
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M
marcob156
Utente Cancellato
le prime due fonti che ho trovato che spiegano cos'è un motore open deck.Forse a molti è sfuggito questo piccolo, ma significativo, particolare!
comunque il motore della giulia condivide il 70% della componentistica con quello del gruppo Chrisler.
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Closed Deck vs Semi Closed Deck vs Open Deck Blocks
The deck is the surface where the head is bolted too.
The open deck design is for ease of manufacturing and not good for high cylinder pressures. This cylinder wall design is supported in 2 places. Many people will say that these engines cannot be turboed effectively but that is not the case. There are a couple here in the club that have run low to medium boost without issue. The problem is where the top of the cylinder where it meets the head will distort from high cylinder pressure and damage the head gaskets ability to seal in the combustion gases.
A semi closed deck design is a little harder to manufacture, but supports the cylinder at the top, bottom and sides. (four places). This is stronger then the open deck design and therefore can take higher cylinder pressures.
The fully closed deck design uses a different casting process that takes longer to manufacture and weighs more. These blocks have the most support to the cylinders, which will enable you to run the highest cylinder pressure of the available choices.
Subaru introduced the closed deck block for homologation reasons to be able to run it in their rally cars. This engine was made famous when a very similar version to it was installed in the limited edition 22B. With the casting methods and alloys available at the time Subaru chose this route to ensure a strong motor. With todays “modern” casting methods and alloys even the semi closed deck designed motors are very strong.
As a guide I would say the following;
Open deck blocks will work for all NA or low to medium boost applications.
Semi closed deck blocks are better suited for boost applications that are not extremely high or prolonged.
Closed deck block are best suited for applications where there will be very high boost for extended periods of time.
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Open Deck
An open deck Ford EcoBoost 3.5L V6. Notice the lack of any type of structural support around the top of the cylinders (although some open deck designs utilize a support point at the end of each outside cylinder).
An open deck is one of the most common designs found in lower horsepower aluminum blocks. It is the easiest to manufacture and provides the overall best cooling efficiency, due to the coolants ability to make full contact with the surface area of the upper portion of the cylinder. Some will argue that this block has the benefit of weighing less than its two siblings because less material is used, but this weight difference is marginal for most blocks.
The downside to an open deck is that it provides the least amount of structural support at the top of the cylinder walls, where they need it most. This reason alone makes an open deck block the least reliable choice for almost any type of forced induction or nitrous application, and should be left to low compression, naturally aspirated engines and low boost platforms.
Semi-Closed Deck
A semi-closed deck flat-four EJ25, found in the Subaru WRX STI. Notice the bridges used to help prevent any distortion around the top of the cylinders.
A semi-closed deck is the most common design found in modern factory turbocharged aluminum blocks, and is stronger than an open deck by adding structural support to the top of the cylinders at four points. Using modern casting techniques, this design can handle respectable boost levels into the mid 30 PSI range and a much higher peak cylinder pressure than an open deck (depending on the application).
Because of the added material around the cylinder walls, this style is more difficult to manufacture and requires more machine work before the cylinders can be installed. Some will argue that the added support joints of a semi-closed deck reduces cooling efficiency and is more prone to cylinder hot spots by limiting the surface area for the coolant to contact. At higher horsepower levels, a semi-closed deck is still prone to failure at the points in between the supporting joints, especially in endurance racing or road racing applications where sustained high temperatures are common.
The most common solution for semi-closed and open deck blocks is installing aftermarket sleeves that can support higher cylinder temps and pressure. This process is pretty expensive, but it is highly recommended that you find a reputable machine shop that has experience with your platform. Sleeving requires a lot of precise machine work to not damage the block, so only the best in your area should be trusted.
Closed Deck
A modified closed deck flat-four EJ25, found in the Subaru WRX STI. Notice the lack of any open space around the water jackets (only coolant ports), providing full support around the top of the cylinder walls.
A closed deck design is generally left to iron blocks and aluminum racing engines. It is the perfect design for fully built, high compression, high revving race engines that require the highest level of structural support available. Common on high level drag race motors, this design is also able to withstand prolonged periods of high heat and cylinder pressure commonly seen in endurance racing and road racing.
A closed deck block is much more expensive and requires an entirely different casting procedure if done from the manufacturer, but can also be modified using pieces that are press fit into position around the water jackets. The latter process requires a custom head gasket, along with precise calculations and machine work to verify that the pieces fit properly and that the water ports are drilled properly to provide adequate flow to efficiently cool the heads.
Many will also note that a closed deck block provides the least amount of cooling capability out of the three. Although this is true to an extent, many of todays closed deck blocks have been put through extensive testing and are designed to guarantee efficient cooling.
Conclusion
Depending on the goals for your build, you may need to sleeve your block or upgrade to a closed deck design. Most modern semi-closed deck blocks can handle very respectable power levels before needing to be sleeved or upgraded, and open deck blocks can handle just about anything you throw at it in naturally aspirated form. But, if you are building a race engine and want the ultimate reliability out of your block, your best option is a closed deck design or aftermarket sleeves (depending on the application and your budget)
Il 70% mi pare un po' esagerato. Se la testata è completamente diversa, con tanto di Multiair che non condivide nulla con una classica distribuzione, il basamento pure, cosa rimane in comune? L'imbiellaggio ed i pistoni...forse.
Per la precisione quello che viene presentato come open deck nella prima foto comparativa è in realtà un semi open deck, perchè ha comunque due ponticelli di collegamento. Un vero open deck è questo:
Ultima modifica:
GPoint
Super Alfista
- 30 Luglio 2009
- 474
- 316
- 126
- 44
- Regione
- Piemonte
- Alfa
- Giulia 2016
- Motore
- 2.0 Turbo Benzina 200CV
Nella prima fonti citata, scrivono questo:
"...... The engine is part of the GME (Global Medium Engine) family; Alfa Romeo’s version is already out, and produces 276 horsepower using MultiAir and two turbochargers....."
Mi sembra di capire che parlino di 2 turbo, ma sono quasi sicuro che la Giulia benzina ne abbia solo 1. Forse mi sbaglio ma mi pare un'inesattezza pesante. Correggetemi se sbaglio.
"...... The engine is part of the GME (Global Medium Engine) family; Alfa Romeo’s version is already out, and produces 276 horsepower using MultiAir and two turbochargers....."
Mi sembra di capire che parlino di 2 turbo, ma sono quasi sicuro che la Giulia benzina ne abbia solo 1. Forse mi sbaglio ma mi pare un'inesattezza pesante. Correggetemi se sbaglio.
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