furiousgeorge

would it be possible, or sane, to take the head into a machine shop, and have a few thousanths shaved off. This would decrease the volume above the piston, increasing compression, right? If someone was to do this, would there be anything else you would need to upgrade so the engine doesnt come apart at the seams? I got thinking after reading this post: "Why does the MG engine have a 10.0:1 Compression but the other three have 8.5:1. How are they getting all that extra compression??? Any ideas?"

Dwight V.

They get the compression from pistons. Less dish in the N series engine pistons. Shaving some off your head will make more, maybe get you up to 9.0 or 9.5. Worth doing if you're taking it apart for something else, but not a worthwhile endeavor by itself.
You'll still be short the bigger valves of the 2.3.

RSTPerformance.com

<center><img src="http://pictureposter.audiworld.com/42058/s_nhis_01.jpg"></center><p>
B (Recess depth) is only 4.4 mm instead of 8.1 mm like the others! This gives it much less volume therefor increasing the compression.

As far as shaving the head. you can shave off 38 thous. before the pistons start hitting the valves. if you get to 40 thous. valves will get bent!! It does help compresion /horspower/torque quite a bit. I have no actual data but I would bet at least a 10% increase!!! To be safe go to 30 thous. then if you ever overheat you can still fix the head without buying a new one!!

furiousgeorge

sounds good to me... now all I need is a good excuse to take the head off the car. Im taking a machine shop class at college starting in 4 days.

MikTip

Then you will need an adjustable cam sprocket to get correct timing.

You wont even gain 1 point in a 9.5:1 compression Audi engine, by shaving the head to its max! BTDT! ;O)

To really gain, you need to change pistons, or weld up the combustion chambers in the heads. Here to, ya need to know "exactly" what your doing, or your engine will not survive! ;o)

"Best" method is larger bore pistons of higher compression.

My 1986 Coupe had 79.5mm @ 8.5:1 pistons stock KX motor.

I installed 83mm Mahles @ 10.5:1!

Then a "Big valve" head! Now your talking!

Ya gotta pay to play! ;O)

Evilclown

Weld up the chambers? 'splain please.

MikTip

Re: Weld up the chambers= adding material to reduce the combustion chambers! ;o)

furiousgeorge

AH HA!! Little did you know... but im a welder... And aluminum is my specialty! I still need a reason for taking the head off my car...