Porsche has never went to the extremes of making a twin turbo 944. It's policies in the 1980s follows:
-No 944, 924 or 928 shall exceed performance of the baseline 911.
-The marque of the 911 was to never be challenged by such extremes of diverse model production.
HOWEVER, there is a 944 twin turbo. But its a custom job. The use of a 951 block and head isn't relevant to this project seeing that the motor cannot handle a second turbo.
I have seen a 1984 944 at the PCASD autocrosses that is twin turbo. After talking to the owner of the car, he had used a standard NA motor to obtain the twin turbo technology. By heavily modifying the head, intake and crankcase, he was able to bolt on 2 K-27 turbochargers to it. the Compression was 8.5:1 and the HP was about 422 HP at 5300 RPM. Yes it is possible to do a twin turbo conversion on a 944. a 951...NO.
Be advised that this project would cost an excruciating amount of money. about 7-10 thousand to be exact.
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Porsche. Es gibt keinen Ersatz.