Optimizing Engine Operation, How good can it get? Options

[ctc911ctc]

Overview

'74 2.0L, 20K miles, stored since '84, first run Oct 2018. 100% stock D-Jet engine with new hoses, fuel system, etc. Spec compression on all 4. Dwell set, timing set.

Engine runs good, strong - chasing idle problems (see my post 'idle weirdness').

My question is; how good can I get this engine to idle? Can this engine run smooth at 800-900 RPM with very little engine vibration? Can the engine run rock steady at 800 rpm without minor surges? Currently this engine is shaking at idle, not violently but you can feel it in the cab.

Does anyone have a high quality audio example of this engine running when new? Or to absolute factory spec? (yea, I know many of you believe that this is not a good method of reference, but hearing what one SHOULD sound like is helpful).

I look forward to coming into this group of like minded 914-crazy (me being the most crazy) group of awesome people each day.

Many thanks in advance

CTC911CTC

[Superhawk996]

idle will never compare to modern vehicle standard. You will always feel idle to some degree on a 914; even with a smoother running six cylinder engine.

There is very little isolation from engine and/or transmission mounts by modern standards.

Modern vehicle idle is a careful tuning of engine firing order vs. engine mount damping characteristics. Many modern vehicles use active engine mounts that are tuned to one frequency at idle and another frequency at road speed. 914 has no such thing just two tiny engine mounts that are a couple of inches in diameter.

Cannot compare vintage cars to modern.

Enjoy what you have.

[BeatNavy]

idle will never compare to modern vehicle standard. You will always feel idle to some degree on a 914; even with a smoother running six cylinder engine.

(IMG:style_emoticons/default/agree.gif) BUT...you can get it pretty close. Modern cars use a closed-loop FI system, and the computer and idle air control valve can compensate for the different variables. D-Jet has no feedback mechanism other than you making the necessary tuning changes based on what you see/hear/experience.

[Bleyseng]

idle will never compare to modern vehicle standard. You will always feel idle to some degree on a 914; even with a smoother running six cylinder engine.

(IMG:style_emoticons/default/agree.gif) BUT...you can get it pretty close. Modern cars use a closed-loop FI system, and the computer and idle air control valve can compensate for the different variables. D-Jet has no feedback mechanism other than you making the necessary tuning changes based on what you see/hear/experience.

You can get it fairly close but with 45 year old engine it takes time to go thru all the FI parts to get it correct. Rebuild the dizzy, install a Pertronix, new or clean the trigger points then on to setting the valves, and get the AAR valve to work right and open smoothly. Once all these little things are done it will idle at 850-900 rpms just fine. Mine idles at 1050-1100 due to Raby cam just fine.

[mepstein]

idle will never compare to modern vehicle standard. You will always feel idle to some degree on a 914; even with a smoother running six cylinder engine.

(IMG:style_emoticons/default/agree.gif) BUT...you can get it pretty close. Modern cars use a closed-loop FI system, and the computer and idle air control valve can compensate for the different variables. D-Jet has no feedback mechanism other than you making the necessary tuning changes based on what you see/hear/experience.

You can get it fairly close but with 45 year old engine it takes time to go thru all the FI parts to get it correct. Rebuild the dizzy, install a Pertronix, new or clean the trigger points then on to setting the valves, and get the AAR valve to work right and open smoothly. Once all these little things are done it will idle at 850-900 rpms just fine. Mine idles at 1050-1100 due to Raby cam just fine.

The good thing is by the time you get there, you really understand the system vs throwing parts at a problem. Modern FI is great but it's a steep learning curve and $$$ to get it on a type 4 for not much better running on a stock system. For a BIG 4, by all means, go aftermarket FI.