New DD and future BT/BAT...also a question about compression

**safab** · 06-13-2008 10:51 PM

So while browsing craigslist I came across a 97 a4 1.8tQM w/ ~235,000 miles that supposedly had a bad turbo, bad cat, possibly o2 sensor(s) and lastly a blown head gasket also. Owner says the car drove fine until 40K miles ago until the turbo blew...even then it drove fine until a few K miles ago when the CEL came on and the mechanic diagnosed it as mentioned above. I couldn't resist and was able to snag it really cheap thinking I could go BAT on it later in the year and for now just spend a few bucks and repair and use it as a beater w/ the blown turbo and all for the summer.

Anyways, picked it up and drove it around all day w/ A/C on and no overheating or any issues that I could tell whatsoever, besides no power and a CEL. I got her and home and did not find any oil in the coolant and no coolant in the oil. Hooked up a boost gauge and the vaccume reading is good. Also did a compression test and got (cyl 1-4) 185, 190, 180, 190. I searched and from what I read that is pretty good??? for a 1.8t. So, what i'm thinking is that I got lucky....that the turbo blew (a oil seal) and oil has been leaking into the exhaust fouling either an o2 or the CAT thus the CEL. What do you fellas think? Am I on the right page here?

I've got a 3071r/550's/FMIC and 034Ic sitting around so might as well pick up a manifold and throw that in (go BT for onw) and run it for a while till it pops........if the engine is good.

**biketsai** · 06-14-2008 12:24 AM

How much did you get the car for if you dont mind me asking.

**spxxx** · 06-14-2008 12:31 AM

that compression test looks good, mine was 158, 160, 165, 165....
its not the pressure that matters but the difference between them, take the highest pressure and multiply by.75 to get the lowest possible allowable.

**safab** · 06-14-2008 09:28 AM

1500

Cool...I guess instead of spending the money on repairs right now I need to find a manifold.

**onemoremile** · 06-14-2008 09:31 AM

Sweet deal.

**mike-2ptzero** · 06-14-2008 09:32 AM

Originally Posted by spxxx

that compression test looks good, mine was 158, 160, 165, 165....
its not the pressure that matters but the difference between them, take the highest pressure and multiply by.75 to get the lowest possible allowable.

Well the pressure still matters since that is what compression the motor has and usually means there is a good amount of wear, plus the motor is not running at 100% anymore unless more timing is being added to make up for the lower compression.

**njm23** · 06-14-2008 11:07 AM

ur gunna have to build that motor to run a 3071r... i dont see why you would wanna blow it up and have to find a whole new engine when you put a rod through the block.. and nice deal on that! got lucky, must feel nice. ha

**spxxx** · 06-14-2008 11:50 AM

Originally Posted by mike-2ptzero

Well the pressure still matters since that is what compression the motor has and usually means there is a good amount of wear, plus the motor is not running at 100% anymore unless more timing is being added to make up for the lower compression.

so what is the "optimum" compression pressure for our engines?

**safab** · 06-14-2008 12:03 PM

Originally Posted by njm23

ur gunna have to build that motor to run a 3071r... i dont see why you would wanna blow it up and have to find a whole new engine when you put a rod through the block.. and nice deal on that! got lucky, must feel nice. ha

I've already got a spare motor and all parts for a 2.0L build...just need to clearance the block and assemble the motor. So I'm not worried if the motor pops. Besides, I don't have to push the 3071r to the max...I should be ok around 300whp hopefully on the stock block.