Computronix Ignition

[majicwrench]

You abuse me, and don't understand. HEI works well, in the system it was designed to work in. It is dependable, you can find parts, and you can find repair info easily. I would not recommend anyone remove their HEI.

I am not in love with points, I am in love with things that work dependably, that you can find parts for, that you can find repair info on, that are simple to fix.

There is post on the site right now, a question about aftermarket ignition. No one has replied. Does no one know the answer?? I am tempted to, but then I might be accused of "knowing nothing about" ignition systems.

Keith

[70spider]

HEI, why not take it out and go back to your beloved points?

This comment intrigues me. As I have mention in other posts the PO a long time ago put on this in the car
There are a ton of wires associated with it including running a wire directly from the #9 fuse to the balast. So with funding being low I was thinking the best thing would be to return it to points but I have no idea how. I might be able to afford the Petronix from AutoRicambi but with all the wires it looks like a daunting task.

[BCbrad]

Just got mine installed today for my 78. Seams to run very smooth, I have some tweaking to do though. There was a couple things that I had not planned for: 1. bending the alternator bracket 2. cutting the plug that is swapped from the aux port the the OEM distributor location. Also, the existing clamp for the new distributor did not fit well, so I needed to file the inside radius of the open end and drill out the hole a little to offer more room.

I was very hesitant to make the changes. Not because it is overly difficult, but once it is done there is no going back. If a new bracket and hole plug where available I would have purchased them to save myself the trouble and the anxiety. Otherwise, I can't wait to put some miles on!

[phaetn]

generally not a problem to push it to 15btdc at idle.

Had the car looked at by a very knowledgeable Fiat mechanic earlier in the week and worked magic on my steering; he also advanced the timing to adjust by ear and said I could probably take it a bit further, too, as long as it wasn't pinging and getting pre-ignition.

So I advanced it a bit and clearly went too far since it became hard to start at times (not as though it wouldn't catch, but as if the battery was dead or dying and could hear a pop out the pipe) -- I attribute this to the starter fighting to push the crank one way, while the spark was so advanced the combustion was trying to force the piston the other way. Backing it off made for easier starts again. I never did hear any knocking or pinging.

Just for fun (and piece of mind?) I also used a timing light, but just don't know the right angle to look at it. Is there an "official" perspective documented somewhere in a manual? This is the best approximation of the view I used that I could get with a camera to see where I was looking so I could clearly see the mark on the pulley as well as the 0, 5, and 10 degree marks on the timing belt cover. Is this about right? I know it's not quite visible with this shot, but it was around where I was at. It was quite clear to see all the marks with the strobe flashing double-time.

Looking at it from a different perspective (e.g. driver side of car) meant I couldn't even see the pulley mark as the rad was in the way or I was so to the side of the pulley that there was no front aspect to see the mark at all -- I suppose I could paint it on the side of the forward lip of the pulley; alternatively, if I was more overhead from the passenger side it really affected how the angles and marks lined up and it was hard to match or see much distinction between 5 and 10 degrees, let's say.



Thanks for any help and cheers,
phaetn

[majicwrench]

A "very knowledgable" mechanic would not set timing by ear. Engine then cranked hard because you had way too much timing. Could have easily blown head gasket or worse.
Keith

[phaetn]

A "very knowledgable" mechanic would not set timing by ear. Engine then cranked hard because you had way too much timing. Could have easily blown head gasket or worse.
Keith

To be fair, it was I who continued to advance it to the point with some hard starting, not he.

Any comment on best / most appropriate viewing point?

Thanks and cheers,
phaetn

[RRoller123]

I run the Computronics at 12 deg per timing light and the point marks. Still not sure how accurate the marks are, but the car runs well, definitely smoother and more power with the Compu ignition. One interesting thing is that my HF Xenon light failed after just a few days of fiddling, maybe 5 minutes max total bulb "on" time. I wonder if the much higher voltage in the spark plug lines made any difference? Senses by induction. I will take it back and get another one and see what happens to that one.

[4uall]

hey phaetn start on page 65, this might help

http://www.artigue.com/fiatcontent/Arti ... 124_MM.pdf

[4uall]

here is a great video for older fiats as well

https://www.youtube.com/watch?v=NoNAsPHiulY

[phaetn]

hey phaetn start on page 65, this might help

http://www.artigue.com/fiatcontent/Arti ... 124_MM.pdf

Thanks, I'd read that before but I've been seeing so much information over the past few months it's sometimes hard to remember what's what.

Good to see the info about tuning by ear as it might help others, too. Given the fixed advance of 20 degrees on the CompuTronix, I now understand why 15 btdc for idle is the suggestion (as per SoCal Mark) so as to get 35 degrees maximum advance.

I still wonder about the precision in measuring given the angles involved... I might try and paint a mark on the front lip of the pully so I can see it from the driver's side of the car and line it up better...

I will say I now have a good balance between good starting and some extra oomph at 3500 or so as it hits maximum advance. It just pulls noticeably better.

Thanks again and cheers,
phaetn

BTW Jay, you've inspired me to get a new steering wheel. I'll post in the other thread to keep this one clean and on topic.

[majicwrench]

Trying to set timing by ear it like target shooting blindfolded. You might get lucky and hit the target....

[phaetn]

Okay, okay, I get the message. I've got orange spray paint and a kid's paint brush to dab it on, am literally printing a degree wheel in the background as I type now, and will paint both the mark on the pulley as well as 35 degrees for full advance when at the "0" mark on the belt cover...

Then I'll aim with the timing gun from both sides...

I'm trying to remember if blindfolded and target shooting is how I conceived both my children. I'll have to ask my wife when she gets home.

One more question: can I turn the electonic ignition unit to adjust timing while the engine is running, or do I have to bolt it down to test each time and start the engine anew? I was doing the latter to be on the safe side because I'm not sure what is spinning down at the base of the unit and didn't want to strip any gears.

Cheers,
phaetn

[phaetn]

And here's the proof positive. It was actually not that hard to get at the crank pulley from under the front of the car once I had it in the right position.

I painted marks for TDC and 35° BTDC (the CompuTronix unit has 20°full advance).


I had to guess a bit for timing at idle since there's no 15° mark on the timing belt cover, but it's pretty clear where it should be based on viewing the 0, 5, and 10 degree marks. I'm also not really sure how accurate the tach is at idle, but I nevertheless aimed for 850rpm.

The two marks are clearly visible, as is the red LED of the CompuTronix unit itself pulsing.

I also ran the car at full advance at 3500RPM (easy to do in my '74 as it has a throttle knob that can be locked in position) and confirmed that the painted mark for 35°lined up with the 0° indicator in the yellow cover. Surprisingly I could catch some of it on video (I wasn't sure if the strobe's frequency would affect capture because of a mismatching frame rate). While the marks on the cover can't be seen, they were very clear to the naked eye.

I think this is precise as I'll ever get it...

Posting this for posterity in case anyone else needs inspiration to check timing this way.

Cheers,
phaetn

[toplessexpat]

One more question: can I turn the electonic ignition unit to adjust timing while the engine is running, or do I have to bolt it down to test each time and start the engine anew? I was doing the latter to be on the safe side because I'm not sure what is spinning down at the base of the unit and didn't want to strip any gears.

You sure can. I loosen the clamp off, then gently tighten it until the unit turns stiffly. If you get the angles right you can have the timing light going as well and it's pretty simple to set things up.

FWIW - I've got the Computronix set at about 12 degrees..... it just seems to work

A

[phaetn]

One more question: can I turn the electonic ignition unit to adjust timing while the engine is running, or do I have to bolt it down to test each time and start the engine anew? I was doing the latter to be on the safe side because I'm not sure what is spinning down at the base of the unit and didn't want to strip any gears.

You sure can. I loosen the clamp off, then gently tighten it until the unit turns stiffly. If you get the angles right you can have the timing light going as well and it's pretty simple to set things up.

FWIW - I've got the Computronix set at about 12 degrees..... it just seems to work

A

Thanks for the reply, A.

You're quite right: It was dead simple to adjust when running with the strobe on. Just for accuracy's sake, I had also painted a third mark at 15° on the pulley. It takes the guesswork out so I can line it up to the zero indicator on the timing cover. Timing is bang on now, both at idle and full advance.

If anyone's interested (and as a testament to Mark's own video that started this thread), I posted a video of my own start up sequence with the CompuTronix ignition and a 32/36 DFEV carb after having been away camping for three days so the engine hadn't been started at all in that time. Today was a warmish August day (75°F at the time of the test). Not sure how this compares with others' start ups, but it seems just fine to me.

I should try again in the morning when it's cooler.

Cheers,
phaetn