user 8202

I just got my 97 back running after rebuilding the engine with all forged internals running 84mm 8.8:1 pistons.

for you guys that have done the same thing, did you habe to change any settings in megasquirt? Did you change the displacement from 1839 to 1900? Does lowering the compression change how much timing advance I can run or just the amount of boost? So far I haven't ran the new engine with any boost, just trying to get a few hundred miles on it first.

sonofthehill

iTrader: (1)

Yes it will need to be re-tuned. Pretty much anything you change will require some adjustments.

borka

iTrader: (1)

With a lower compression engine you can up the timing a bit for more power, or leave it as is for more safety.

Then run autotune to fine tune the fuel ratio as it will be a bit off since you changed the compression.

technicalninja

I'd leave it alone for now...
You changed the compression ratio 0.2 points from 9.0 to 8.8 (reduces dynamic compression) but you increased the displacement 15 cc per cylinder (increases dynamic compression).
Dynamic compression will not change much if at all.
I would not make timing changes right now.

You made it STRONGER but you didn't change the operating parameters very much at all...

Let auto tune do its thing.

user 8202

Ok cool, thanks everyone. I haven't really changed anything other than running autotune and it has changed the VE table some. Im going to slowly start adding some boost soon.