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

[mepstein]

Yes. A good running FI system is a wonderful thing. It's worth putting the time in if you are already 95% there.

[thelogo]

Call me crazy but when you park it for 35 years
You should just be happy it still runs .

I would reach into my wallet pull out 3k
And do aftermarket fuel injection.
If the eratic idle bothers you .


Or you can keep driving as is and hunt down exhaust and vacuum leaks
Smoker tester (glass bong)
is your friend

[roblav1]

Chase down vacuum leaks and get the injectors cleaned. Make sure the fuel tank is clean too.

[SirAndy]

Also consider looking at the engine wiring harness.

I ended up making one good as new wiring harness out of 3 old ones. Many of the wires had become brittle and had broken insulation under the protective sleeves.
This made a huge improvement in how smooth the engine ran (1.7L D-Jet).
(IMG:style_emoticons/default/idea.gif)

[914_teener]

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

You could be suffering misfires at the injectors due to a crack harness as Andy suggests.

After replacing and going through everything on my d-jet system including a new harness and finally the 123 distributor, it idled dead nuts to spec and steady an pulled strong up to the redline, and was right on the money after I check the AFM with a wideband.

I say this from experience FWIW. Unless you like programming and major fiddling yourself or can afford to pay for aftermarket injection for a stock motor, stick with the D-jet. The Bosch engineers knew what they were doing, and if they could have done it better they would have. Anybody who has done it will tell you that...anyone else who hasn't either likes fiddling or hasn't ever serviced FI or worked on it. My opinion and only mine.

If I could have found a good original dizzy I would have done that but I coudln't.

Good luck there are still a lot of good folks here....the ones who are still with us.

[thelogo]

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

You could be suffering misfires at the injectors due to a crack harness as Andy suggests.

After replacing and going through everything on my d-jet system including a new harness and finally the 123 distributor, it idled dead nuts to spec and steady an pulled strong up to the redline, and was right on the money after I check the AFM with a wideband.

I say this from experience FWIW. Unless you like programming and major fiddling yourself or can afford to pay for aftermarket injection for a stock motor, stick with the D-jet. The Bosch engineers knew what they were doing, and if they could have done it better they would have. Anybody who has done it will tell you that...anyone else who hasn't either likes fiddling or hasn't never serviced FI. My opinion and only mine.

If I could have found a good original dizzy I would have done that but I coudln't.

Good luck there are still a lot of good folks here....the ones who are still with us.

(IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif)


The bosch engineers did it way too good
When your design outlasts the parts required to build and maintain the system several decades over

You are pretty bad ass.

Niceest retro fit 914 f.i i ever saw was a bosch system off a rabbit .... Looked alomost factory .


But with virtually no parts /components available for djet
In theory you could 3d print a new mps ?

But in 1975 did they sell them (mps) or 5th injector
at flaps ?





And if modern fuel injection is so expensive.

Would carbs and a carb cam be cheaper
(Engine out anybody )

[ctc911ctc]

Laughed at this, and we were thrilled that it ran, very very thrilled!
But I want more!

Call me crazy but when you park it for 35 years
You should just be happy it still runs .

[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.

[914_teener]

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.

Or just make it a six. (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/first.gif)