Lowering Compression Ratio for Boost

[ian_norris]

Hi guys,
I have a 1995 Saturn SC2 DOHC and I am entertaining the idea of turbo-ing it. My primary concern is running 10+ pounds of boost in a 9.5/1 compression ratio engine. I have not been successful at finding pistons with dishes or lower compression height. Head spacers don't seem to be extreme enough. I'm trying to drop it to about 7.5/1, which- according to charts I've found online- should bring the active compression ratio to about 12/1, which should be ok on 98 octane gas (with the stock ignition timing?).

Does anyone know of a source for shorter/dished pistons for a '95 DOHC 1.9L? Alternatively, does anyone have other effective strategies for dropping compression ratio?

[cgg17]

Originally Posted by ian_norris

Hi guys,
I have a 1995 Saturn SC2 DOHC and I am entertaining the idea of turbo-ing it. My primary concern is running 10+ pounds of boost in a 9.5/1 compression ratio engine. I have not been successful at finding pistons with dishes or lower compression height. Head spacers don't seem to be extreme enough. I'm trying to drop it to about 7.5/1, which- according to charts I've found online- should bring the active compression ratio to about 12/1, which should be ok on 98 octane gas (with the stock ignition timing?).

Does anyone know of a source for shorter/dished pistons for a '95 DOHC 1.9L? Alternatively, does anyone have other effective strategies for dropping compression ratio?

I have ran 7 psi on stock 1995 ignition timing with megasquirt for fueling.
Currently I run between 12-14 psi with megasquirt now controlling fuel and timing.
The engine has not been opened and has 195k miles on it. Have not had an issue yet, and I am running 93 octane pump gas.
What are your plans for tuning?
I will say this: if you do not plan on installing an aftermarket ecu for fuel and timing control, do not bother with a turbo.

[ultravioletnk]

Originally Posted by ian_norris

Hi guys,
I have a 1995 Saturn SC2 DOHC and I am entertaining the idea of turbo-ing it. My primary concern is running 10+ pounds of boost in a 9.5/1 compression ratio engine. I have not been successful at finding pistons with dishes or lower compression height. Head spacers don't seem to be extreme enough. I'm trying to drop it to about 7.5/1, which- according to charts I've found online- should bring the active compression ratio to about 12/1, which should be ok on 98 octane gas (with the stock ignition timing?).

Does anyone know of a source for shorter/dished pistons for a '95 DOHC 1.9L? Alternatively, does anyone have other effective strategies for dropping compression ratio?

the stock pistons for the 1st gen (1991-1995) sohc motors are dished, they've long been a popular choice for budget boosted builds. that said, the stock compression ratio is plenty fine for boost if you have good engine management and fuel. many cars these days are running turbos on 10:1 and higher, and direct injection engines push it even further.