Can DDEC a 5 head bolt onto a DDEC 6 block?

So, after 4 months of battling 4.5 mpg with my 2008 Cascadia, I'm getting desperate for more miles per gallon.

DDEC 6 has been inframed, overhead ran twice, new reman head, all new sensors and engine wiring harnesses. Although most of the random codes are now gone AND my engine runs pretty smooth, I can't get this engine to get better fuel economy.

The truck has been reliable but I'm at the end of my rope chasing fuel economy. 3.90 gearing and Eaton 13 speed. I'm running at 1450 rpm @ 64 mph.

I've posted and read on this forum that the DDEC 5 is vastly superior to the DDEC 6.

Apparently the DDEC 5 is even capable of 7.5 npg whereas my DDEC 6 might manage 6.5 at best. I'm currently getting 5 and that's with my APU finally working and summer fuel blend AND more repair bills than my truck is actually worth !!

The only things left to do are the injectors, injector wiring harness and the turbo. The turbo actuator has been checked twice. No issues.

SO. I'm seriously considering buying a reman DDEC 5 head and using N2 injectors instead of the problematic E3 injectors.

I'm pretty sure that the oil and water holes will line up but I know that the DDEC 5 fuel return line exits at the back of the head whereas the DDEC 6 fuel return line exits at the left rear of the head. The shop I want to use can deal with that.

Will the compression ratio change at all using a DDEC 5 head?

Will the N2 injectors hit the top of the pistons?

I know that the N2 injectors have 2 pin connectors but the E3 injectors have a 4 pin connector.

Does anyone know why the E3 injectors have 2 extra pins?

If all I need is a custom injector wiring harness, then I'll get one made.

Does anyone know why this won't work? Quality Truck maybe Benjamin 260_6?

 

Thanks for responding to me. Thanks for the head's up re the N3 injectors. A few people have told me that a good tune will help but I'm not sure that the DDEC 6 will ever get 7 mpg hence the idea of swapping heads.

 

@QUALITYTRUCK. I do thank you but I finally understand that I need a good tune.

In numerous posts, I read that the DDEC 5 is a better engine so that's the root cause of my fixation.

 

Wait. I am not wasting everyone's time.

My tuner, the injector guy and this forum all told me that the DDEC 5 was a better engine. Before I buy a new set of E3 injectors and get a proper tune done, I wanted to be 100% sure that I wasn't missing out on an opportunity to get even better fuel economy. That's why I posted.

Thank you all for your insightful replies.

 

BTW the truck has already been deleted by the previous owner and tuned. It puts out 517 hp to the wheels and makes 1847 ft lbs of torque.

Redoing what was already done makes me wonder where the smoking gun is....