# iron block vs aluminum blocks



## interested_vw_buyer (May 7, 2006)

I was kind of disappointed when I found out the new 2.0T engine has an iron block instead of an aluminum block. Two different mechanics have told me in the past that engines with iron blocks and aluminum heads have a greater chance of needing a head gasket sooner because the two different materials expand and contract with head at slightly different rates, and that over time that loosens the head gasket seal. 
Has anyone heard this as well? Any thoughts? 
I am under the assumption VW went with the iron block to save money. Of course it weighs more I would imagine too, and that might contribute to the GTI's higher than you would think curb weight...


_Modified by interested_vw_buyer at 2:48 PM 5-7-2006_


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## silver bullet_337 (Mar 2, 2004)

*Re: iron block vs aluminum blocks (interested_vw_buyer)*

i always thought that an iron block is better for tuning.


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## gtiiiiiiii (Mar 6, 2004)

*Re: iron block vs aluminum blocks (silver bullet_337)*

iron block is stronger normally http://****************.com/smile/emthup.gif


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## whizbang18T (Nov 17, 2000)

what's wrong w/ an iron block ... it's good enuff for my sub 2L .. =P


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## iThread (Sep 27, 2005)

Imagine if VW went back to Magnesium


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## shaunyeap (Aug 19, 2005)

Perhaps they just went with the iron block because the 2.0TFSI has a rather high compression ratio, esp for a turbo motor.
Someone correct me if i'm wrong however, isn't that new 3.0 twin turbo engine by BMW magnesium?


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## Theresias (Feb 11, 2004)

*Re: (thread)*


_Quote, originally posted by *thread* »_Imagine if VW went back to Magnesium









I worked for a supplier of VW couple of years ago, were prototyping some magnesium oil pans there...


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## Cadenza_7o (Jan 23, 2001)

*Re: (shaunyeap)*


_Quote, originally posted by *shaunyeap* »_Perhaps they just went with the iron block because the 2.0TFSI has a rather high compression ratio, esp for a turbo motor.
Someone correct me if i'm wrong however, isn't that new 3.0 twin turbo engine by BMW magnesium?

Not sure about the 3.0 twin turbo but the NA 3.0 I-6 varieties have magnesium casing with iron cylinders. Cast Iron is simply cheaper to make and work on. I don't see VW going to magnesium anytime soon... Alu perhaps.


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## Tanner74 (Jul 28, 2003)

Yes, magnesium is used in the new BMW engine.
http://www.worldcarfans.com/ne...depth


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## Rob_vgti (Apr 24, 2006)

*Re: iron block vs aluminum blocks (gtiiiiiiii)*

Iron blocks are built to take a massive beeting. aluminum tend to have possible flaws hair lin cracks.. their not ment to be used in turbo motors u could have one but then your looking at a new motor down the road. PLUSSS iron blocks give the deep roar. an aluminum block will give a hi tone to it.. almost like a civic with a fart cannon on the back with no vtec....


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## gtiiiiiiii (Mar 6, 2004)

*Re: iron block vs aluminum blocks (Rob_vgti)*

my mkiv never sounded like a honda lol


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## h0tg60 (May 12, 2005)

*Re: iron block vs aluminum blocks (gtiiiiiiii)*

LS7 ALL ALUMINUM HEAD BLOCK TITANIUM RODS 500BHP on 91 OCTANE< READY FOR 7PSI OF BOOST >


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## interested_vw_buyer (May 7, 2006)

*Re: iron block vs aluminum blocks (Rob_vgti)*

There are an awful lot of all aluminum examples that don't seem to support the idea that iron is better for either turbocharged, or high compression engines. The Honda K24 has an extremely high compression ratio and it's all aluminum. Subaru turbocharged engines are all aluminum and they put out a lot more power than VW/Audi 2.0T engines. The 2.5-liter STI engine puts out 300 horsepower. Prior to their switch to 2.5-liter displacement, the 2.0-liter WRX made 227 hp with an aluminum block and head. The VW/Audi 2.0T makes 200. 
I do not know what the weight differences are. Clearly the aluminum is lighter but by how much I have no idea. I also don't know the cost differences and knowing both of those facts would help me understand the issue. 
I still also am curious if anyone knows conclusively if the head gasket seals are more likely to loosen with an aluminum head and iron block.


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## Borti (Jan 19, 2005)

*Re: iron block vs aluminum blocks (interested_vw_buyer)*


_Quote, originally posted by *interested_vw_buyer* »_There are an awful lot of all aluminum examples that don't seem to support the idea that iron is better for either turbocharged, or high compression engines. The Honda K24 has an extremely high compression ratio and it's all aluminum. Subaru turbocharged engines are all aluminum and they put out a lot more power than VW/Audi 2.0T engines. The 2.5-liter STI engine puts out 300 horsepower. Prior to their switch to 2.5-liter displacement, the 2.0-liter WRX made 227 hp with an aluminum block and head. The VW/Audi 2.0T makes 200. 
I do not know what the weight differences are. Clearly the aluminum is lighter but by how much I have no idea. I also don't know the cost differences and knowing both of those facts would help me understand the issue. 
I still also am curious if anyone knows conclusively if the head gasket seals are more likely to loosen with an aluminum head and iron block. 

Power numbers from the factory do not have much to do with that engines capabilities persay... I will agree though the EJ in the STi is a very stout alum. block. http://****************.com/smile/emthup.gif 


_Modified by Borti at 12:11 AM 5-11-2006_


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## Electron Man (Sep 21, 1999)

*Re: iron block vs aluminum blocks (interested_vw_buyer)*

Unless I'm mistaken, the FSI head is an Al/Si alloy that has roughly the same expansion coeff. of the cast iron block. http://****************.com/smile/emthup.gif


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## interested_vw_buyer (May 7, 2006)

*Re: iron block vs aluminum blocks (Electron Man)*

Interesting. I googled Al-Si engine blocks and didn't find much. 
I guess I am hesitant because of how many automakers have switched to all aluminum engines, and because more expensive cars almost always use all aluminum engines. Also some notoriously reliable, yet affordable models, like the Honda Civic have all aluminum engines. Thus I am suspicious that VW's iron block is simply to save money and move cars off lots now at the expense of long term repair costs, something few buyers will even know about or factor into their decision.


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## allcool (Oct 24, 2002)

*Re: iron block vs aluminum blocks (interested_vw_buyer)*

Electoman is correct, expansion rate for al-si is much better than aluminum.
al-si has been major break thru for piston and engine design.
Some of the new A R T forged pistons have expansion rates similar to cast pistons.
Aluminum-Silicon Alloys better thermal expansion rate allows much closer piston to cylinder wall clearance then older forged pistons from the past. We can now enjoy the strength of forged and the tight wall clearance usually associated with cast pistons. 
http://www.key-to-metals.com/Article80.htm


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## h0tg60 (May 12, 2005)

*Re: iron block vs aluminum blocks (allcool)*

FOR LAYMEN MEANS NO SLAP WITH FORGIES WHEN COLD PERFORMANCE IS SAME


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## im_a_local (Jun 4, 2004)

*Re: iron block vs aluminum blocks (interested_vw_buyer)*

The Iron block/aluminum head combination has been used countless times, so this is prob the least of your worries. If the engine overheats then, yes, the head may warp upon the heating/cooling. The 4.6 mustang blocks are an iron 4 bolt mains, and the N/A cobra block was aluminum 6 bolt. When SVT decided to build a supercharged version, they went back to the 4 bolt iron.


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## Mad Dragon (Aug 20, 2001)

*Re: (Cadenza_7o)*


_Quote, originally posted by *Cadenza_7o* »_Not sure about the 3.0 twin turbo but the NA 3.0 I-6 varieties have magnesium casing with iron cylinders. Cast Iron is simply cheaper to make and work on. I don't see VW going to magnesium anytime soon... Alu perhaps. 
The N52 cylinder sleeves are AluSil.


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## Zeratul61985 (Mar 25, 2006)

*Re: (Mad Dragon)*

Aluminum dissipates heat better hence the highest point of the motor would be the hottest therefore aluminum will release it quicker...as far as headgasket issues.....VW and Audi use MLS (Multi layered steel) headgaskets on most of their engines and ALL turbo engines, the diesel the diesel pumpe Dusse the 2.0T and the 1.8T all had very durable MLS gaskets.......I know of only ONE headgasket we replaced at my dealership on a passat 1.8T otherwise I saw my fair share of cam adjuster seals leak on passat 1.8Ts but never headgasket issues MLS is widely known in the racing community to hold up to a lot of abuse and is better than copper because it has no heat cycle...its aperfect transition between iron and Aluminum


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## gtiiiiiiii (Mar 6, 2004)

*Re: (Zeratul61985)*

good info http://****************.com/smile/emthup.gif


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## Cadenza_7o (Jan 23, 2001)

*Re: (Mad Dragon)*


_Quote, originally posted by *Mad Dragon* »_The N52 cylinder sleeves are AluSil.

Ah... they're into AluSil now. Thanks for the info...
I wonder if Porsche is still using NikaSil sleeves.


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## allcool (Oct 24, 2002)

*Re: (Cadenza_7o)*


_Quote, originally posted by *Cadenza_7o* »_Ah... they're into AluSil now. Thanks for the info...
I wonder if Porsche is still using NikaSil sleeves. 

Yes!
Nikasil is a hard chrome type COATING process developed by the German firm Mahle, originally for use in the Mercedes Wankel rotary. Nikasil coated cylinders are nickel and silicon carbide matrix coating about 0.07mm .0025-.003" thick.
Nikasil or other similar alloy coated cyl bores are used in many very high performance engines.
Porsche also uses AL-SL for CASTING some of their blocks.
"KS Aluminium-Technologie AG (ATAG) has succeeded in mechanically exposing particles of silicon (a hardening agent) on the contact surfaces for the cylinders in monolithic (ALUSIL) and quasi-monolithic (LOKASIL) aluminum engine blocks. Since 2001, the automotive supplier in Neckarsulm, Germany has been working with a special honing process called SIPLAMEC, which was granted a European patent in March 2004 by the patent office in Munich after an extended application phase. The manufacturing process is used in the V8 engine block of the Porsche Cayenne and elsewhere." 
ATAG also makes blocks for VW , BMW and Volvo. 
So just to make my point clear, AL-Si blocks do not need any coatings or cylinder liners. 
Although some cylinder liners are made completely of AL-SI.
Correct me if i am wrong, iirr some of the replacement cyl liners for the ill famed M52/M60 BMW Nikasil fiasco were al-si
I still don't understand why BMW had problems with Nikasil, when most all other Nikasil motors(Porsche and others) work great. Its funny that some of the Nikasil M52 motors are fine high mileage units even using high sulfur fuel.
Alusil block is less expensive to make than a Nikasil bore coated block. This is because of the new al-si honing procedures from ATAG. Is a Alusil block better than a Nikasil coated block, imo no, unless you are a bean counter.
jmho allcool


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## allcool (Oct 24, 2002)

*Re: (allcool)*

Just so there is no misunderstanding, I am not saying al-si blocks are inferior, nope. 
Look at it like this,
Porsche Cayenne Turbo uses ALuSil block, 
Porsche GT uses Nikasil coated cyl bores http://****************.com/smile/emthup.gif 
Seems as if Porsche thinks alusil is ok for trucks







but prefer to have Nikasil in their highest performance sports car








jmo allcool


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## gtiiiiiiii (Mar 6, 2004)

*Re: (allcool)*

how do you know all this stuff








either way we need more posts like that where I actually learn something for a change


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## syntrix (Aug 20, 2000)

*Re: iron block vs aluminum blocks (interested_vw_buyer)*


_Quote, originally posted by *interested_vw_buyer* »_There are an awful lot of all aluminum examples that don't seem to support the idea that iron is better for either turbocharged, or high compression engines. T

Bingo, aluminum is the block, iron alloy the sleeve. Most the the "iron is better" are comparisons of thing sleeves on honda engines that were improperly boosted.
A lot of modern sleeved and factory turbo'd blocks can take a huge amount of abuse. It's usually the conn rods and wrist pins that go before the sleeve. When that happens, the rod usually scores the sleeve, making it useless. Here's one of my examples:








Wheeeee! Iron is not always better than aluminum blocks. A lot more needs to be discussed before making blanket statements.


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## allcool (Oct 24, 2002)

*Re: iron block vs aluminum blocks (syntrix)*

syntrix,
Looks like a couple of rats been sleeping in that cyl!
Have you determined what caused this to happen.


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## syntrix (Aug 20, 2000)

*Re: iron block vs aluminum blocks (allcool)*


_Quote, originally posted by *allcool* »_syntrix,
Looks like a couple of rats been sleeping in that cyl!
Have you determined what caused this to happen.

Stock wrx block. Plenty of lack of timing advance, plenty of fuel, no knock.
Piston either snapped in 1/2 or the rod twisted and cause the piston to then snap in 1/2. That's the weak link in the stock suby engines... rod/pistons.
But the point is, sleeve was not the problem here. Wouldn't have mattered if it was an iron block or aluminum block.
Head:
http://www.swankmonkey.com/images/IMGP3849.JPG

and a gift from subaru.. who says there's no such thing as a warranty, lol:
http://www.swankmonkey.com/images/IMGP3848.JPG
But that car is long gone now! Someone got lucky and got a used suby with a new engine in it http://****************.com/smile/emthup.gif 

edit:
someone needs to find the fsi spec sheet that shows the extra internal pressure a 2.0T fsi is supposed be capable of holding. I **think** it's 15% more than a 1.8T, but someone needs to chime in.
I think that is more the purpose of this post, internals strength based against another well known platform.


_Modified by syntrix at 9:28 PM 5-16-2006_


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## liquidhg (Feb 7, 2006)

*Re: iron block vs aluminum blocks (syntrix)*


_Quote, originally posted by *syntrix* »_
someone needs to find the fsi spec sheet that shows the extra internal pressure a 2.0T fsi is supposed be capable of holding. I **think** it's 15% more than a 1.8T, but someone needs to chime in.
I think that is more the purpose of this post, internals strength based against another well known platform.



Trying to stay in the context of Fe vs Al blocks - what was the main weak point/link in the stock iron 1.8t engine and can anyone hazard a guess what would be the weak point in the 2.0t?
As syntrix pointed out, would the block necessarily be the weak point? And what sort of HP numbers would we be talking about before it would become an issue, even after some of the internals had been upgraded? I was always under the impression that the rods were typically the weak point of the 1.8t. How much can the stock rods handle? How much can the stock pistons handle? And as it relates to this thread, how much can the stock iron block handle?


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## syntrix (Aug 20, 2000)

*Re: iron block vs aluminum blocks (liquidhg)*

I have it, but I don't know if I can post it.
1.8T has a peak cyl pressure of 85 bar
2.0T has a peak cyl pressure of 110 bar
The 1st piston ring is different between the two, too!


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## liquidhg (Feb 7, 2006)

*Re: iron block vs aluminum blocks (syntrix)*


_Quote, originally posted by *syntrix* »_I have it, but I don't know if I can post it.
1.8T has a peak cyl pressure of 85 bar
2.0T has a peak cyl pressure of 110 bar
The 1st piston ring is different between the two, too!


any idea what those cyl pressures would translate to in relation to HP?


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