In a month or so I will be swapping in my built z6 bottom end and getting ready for some boost. Block has 75.5mm 8.8:1 Wiseco pistons and eagle rods. I will be using Hondata to tune. I played with tuning the stock motor to get an understanding for how everything worked.

So my question is is there anything specific differences between tuning low compression and high compression engines? And for break in I planned to run the motor without the turbo on it yet. Should I run a 255 fuel pump and 750cc injectors during the break in or just wait to install them with the turbo

 

With low comp pistons u can run leaner afr. And more ignition (all motor). Install turbo and fuel system and break in with little boost.

 

It's old, but this is good info from Evans Tuning.

evans tuning forums :: View topic - High Compression vs. Low Compression

Install all your turbo components with the new engine and tune it all at the same time.

 

awesome. Thanks guys. I figured it would be best to do it all together. I assume that if I did it engine first then turbo the entire map would need retuned.

 

I hate low compression dished pistons. I have actually found it better to run less timing with low comp dished pistons. This is due to the fact the top surface of the piston sits nearly 40 degrees below tdc when it's at tdc. Every engine is different and so if every tuner. I'm gonna tell you all this has worked well for me. Especially when you incorporate the spark plug into the tuning process. To each there own. I personally would never run a dished piston regardless of the setup.

 

I mean the pistons are 8.8:1 and stock is 9.14:1 so it's not like they're super low. I figured with tuning it myself on the street I would feel safer with a little more margin for error as opposed to a high compression engine.

 

i think you will find the motor doesnt need/want that much leaner of an afr, maybe a few tenths of a point. i think the bigger difference will be the timing. when i had my vitara setup on the dyno i was quite surprised how much it liked timing, probably turned out to be at least a few degrees over a stock compression sohc but you really need the dyno to find out for sure.