View Full Version : to build or not to build (looking for opinions and options)

12-17-2014, 12:49 PM
So I purchased a donor b5 late spring from a customer that brought in his 2001 A4 1.8t AWM that wouldn't start and had no compression. I pulled the engine and have very slowly taken everything else apart. Well, two weeks ago I finally pulled off the cylinder head and found this...

If I messed up posting the pictures, they show cylinder 4 and 3 pistons totally melted, cylinder 2 with the beginning stages of melting and cylinder 1 with no damage. Judging by the oil channels in the block and knowing the customer and the lack of maintenance done, I think this happened because of a lack of lubrication and/or running lean. When I get some free time next week, I'm going to run it down to the machine shop to see if it's salvageable.

Going under the assumptions that it is, what would you do if the biggest turbo you were going to put in was a K04 or GT28rs and didn't want to spend a ton of money. This would be a daily driver.
My thoughts are get AEB connecting rods and pistons just for strength components and call it a day. But I'm curious to know benefits of possibly honing it out a little bit and lowering compression to 9:1 or even 8.9:1 like the Audi TT (Using rods and pistons from that motor. I know they're difficult to find but just roll with it)
I've been sifting through threads and I know that when you lower compression you can push more psi, but the low end suffers. If someone could make a comparison for me between a 8.9:1, and 9:1 compression that'd be awesome. My wife had a 225hp Audi TT and it didn't seem to suffer that much, but was it just the turbo compensating?


12-18-2014, 10:04 AM
Bump for fixed links

12-19-2014, 06:59 AM
I put AEB pistons and rods on my AWM engine and it ran fine. I totally recommend honing and getting new piston rings. If you have extra money I'd also would get h-beam rods. Since you're thinking in upgrading the turbocharger. How's the cylinder head?

12-19-2014, 10:09 PM
Thanks for the input! That's what I'm trying to determine if I want to do, make this a long term project and put some money into it or not. The cylinder head is in decent shape, just a little warped from the cylinders getting too hot. I took it to a machine shape though and they said that it's a good candidate for a rebuild. If I put the AEB pistons in, would that raise my compression since the AEB engine advertises 9.5:1? (I'm still trying to understand all the ways to raise or lower compression)

12-22-2014, 07:17 AM
To be honest I don't know I heard of ppl putting AEB pistons on AWM engines. I had an extra set of AEB rods and pistons and I bought a 2001 A4 with a blown engine so I did the swap. It drove good, nice power. I think if you raise the compression you just have to use less boost, but with what your goals are I think you'll be ok.

12-24-2014, 10:04 PM
Thanks! Definitely something to consider. I'm trying to decide if I want to do the 9:1 compression ratio or 9.5:1. Do you know how your engine felt compared to a stock awm? Did you also have a tune to compensate for the higher compression? (How much less boost are we talking?) I like the idea of a little higher compression to have a little more bottom end response, but the appeal to higher boost levels at a slightly lower compression for a better top end sounds good also. Since I'm going to be running water/meth, I wonder how much of a difference that would make at either compression. If the system would keep temperatures low enough at higher compression to maybe allow for normal boost? Sorry, I feel like I may be asking similar questions to previous ones, but I've searched the forums and haven't really seen anything definitive because everyone's set up/goals are different.