I was wondering if there were any significant differences in the 2 blocks. I remember somewhere that h22a1 was a closed deck and the a4 is an open deck. And closed deck is better for boost. What are your opinions? I just recently bought an a4 and might build it for boost with Mahle 9:1 pistons. So what should I do build the A1 or A4?

 

How crazy are you planning to go with the engine?

Closed deck adds some rigidity to the sleeves, which is a definite plus.

Open deck people use those block guards but I really don't like that idea, it restricts coolant flow when jammed down into the water jacket, and the top of the cylinder is where you need cooling the most.

 

so would you recommend the a1 over the a4? I am planning to make less than 400. I think around 350whp once the build is done. Just some mahle gold series pistons. Im not planning on going all out on it.

 

Honestly, I think it will be just fine, and since you already bought it, it makes the most sense to keep it.

I'd take a look around the forced induction forum though, they most likely have some good concrete evidence for ya and more turbo-knowledgeable people to talk to. I don't do a whole lot with turbos and all that jazz.

 

Also the 98 and up a4's have 55 mm main journals on the crank as opposed to 50 mm on earlier engines.

 

Are those pistons the ones that don't require sleeving the block? If you go with forged piston's you have to sleeve the block.

 

^ya the are.also they don't need pistons rings.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by v13tx1301 &raquo;</TD></TR><TR><TD CLASS="quote">so would you recommend the a1 over the a4? I am planning to make less than 400. I think around 350whp once the build is done. Just some mahle 9:1 gold series pistons. Im not planning on going all out on it.</TD></TR></TABLE>

Is there a certain reson why did you chose that comp ratio? Also can you tell me how they work out for you? I want to try them in my set up.

 

i wanted to be safe by choosing a lower compression ratio. I was thinking of going with the 10:1 but I would rather have the motor last and sacrifice the lower end power than not having a motor at all. Sure I'll let you know how they work out once I get them running. Wont't be for a lil while since I just dropped like a grand on black friday. haha.