Compression Ratio for 2.056 Engine Build with FI
 

I am having a 2.056 liter engine built and the engine builder is asking me about compression ratio. I am using a combination of 1.7 liter and 2.0 liter fuel injection parts. The description is as follows:

The factory fuel injection I will be using is based on a mixture of 1.7 liter and 2.0 liter parts.

The Manifold Pressure Sensor has been converted from a 1.7 liter unit to a 2.0 liter unit and is adjustable so that the air/fuel ratio can be adjusted for partial and full load conditions with a air/ sensor welded into the exhaust collector.

The air/fuel ratio at idle can be adjusted with a potentiometer on the Electronic Control Unit with input from the sensor in the exhaust system. The fuel injection intake runners have been increased in size from 34 mm for a 1.7 liter to 36 mm for a 2.0 liter by purchasing 2.0 liter runners.

The 2.0 runners will be attached to the heads with three bolts. Four Standard Motor Products FJ67 fuel injectors have been purchased to replace the 1.7 liter fuel injectors. The flow rate for the FJ67 injectors is greater than the flow rate for a factory 2.0 liter fuel injector. The flow rate for the FJ67 injector is 415 cc/min at 36 psi compared to 380 cc/min at 43psi.

I have received input from the builder of the modified Manifold Pressure Sensor that the above changes will allow me to use a larger engine but no greater than 2.056 liters. Also, the compression ratio must not be changed from the factory value and that a factory fuel injection camshaft must be used. The factory compression ratio for a 2.0 liter engine with a actual displacement of 1.971 liters is 7.6. The heads with be new 2.0 liter units. The compression ratio for a 1.7 liter engine is 8.2.

What is the compression ratio that should be used in the engine build?

Lauran

Get a Raby 9590 cam and you can stay D-Jet FI and go as high as 8.5 CR. That's what I'm running (CR about 8.6). Runs nice and strong and also very cool. Only downside I can see is that it doesn't really want to hold a stable idle until it gets a little heat into it (~180 to 200 on the head temps). Based on others' feedback this is fairly normal with this combo.

Here's a link: https://lnengineering.com/type-4-store/camshaft-kits/deluxe-9590-cam-kit.html

I am going with 8.5 to 1.

Lauran