Type 4 rebuild questions Options

[mepstein]

What can I do to rebuild my 1.7 for more HP and torque but keep the original d-jet.

piston and cylinders
crank
camshaft
heads
?

I know I can't change the cam too much but is there one that will do better and still work with d-jet.

I know there is modern FI but I'm not interested. No carbs. I'm not looking for all out HP or dropping 10K on an engine kit. I just want a nice bump in power, if possible, while keeping a stock looking engine.

[JamesM]

I think you are starting in the wrong place. the goals you have are somewhat incompatible with each other. No matter what you do to the motor the 1.7 intake and tiny throttle body are going to choke any significant improvements. The d-jet system itself can be adapted (though you are limited on cam choices) but the intake is still going to choke the motor. I experienced this first hand when I hacked a Megasquirt system together using spare 1.7 d-jet parts I had on to my buddies stock 2.0 motor. While it turned out noticeably better than the progressive single carb he had, the results were still obviously sub optimal. Throttle response was awful and power was choked.

If you are set on keeping the 1.7 intake you can pretty much forget about anything else. If you are tearing into the motor anyways than maybe do the cam, if not than just headers and a good tune are probably your best bet. Personally I wouldn't waste the time and money for such little gain, stock 1.7 d-jet motors are great for what they are.

The 1.8 intake is a whole different story, its what I am running with a 50mm 2.1 waterboxer throttle body on my 2056. I think the fact that the factory went significantly larger on the 1.8 intake components despite the motor being only ~100cc larger is a good indicator as well that the 1.7 parts didn't have any room to grow left in them. You could probably adapt the 1.8 plumbing to work with your 1.7 d-jet system but after that customization plus the motor upgrades you would probably just be better off starting with a stock 2.0, less hassle but probably comparable cost and power.

If you are stuck on keeping the d-jet ECU you have to play within the d-jet boundaries. If your primary goals are stock-ish appearance and more power you should seriously consider a modern ECU. If your goals are keeping 1.7 d-jet + more power you may want to reconsider your goals.

Ditch the d-jet and you could do something like this:
Looks like a stock small displacement motor on the outside, but pulls hard to 7k RPM with HP calculated from acceleration datalogs showing in the 130+ range.