request a lesson on engine timing Options

[type47]

I'd like to know on what parameters does the timing of an engine depend: induction? cam? I am resurrecting a 2L with a carb cam and installing a CIS basic system. We started the engine at the ECC in Oct and am progressing very slowly. I think the engine has an 009 dizzy (engine is still at ECC site so can't check now); at least it has a non-vacuum advance dizzy. I have a 2L D-Jet dizzy ready to install and that will probably be one of the next steps. When we started the engine, it did not sound smooth running but it started and that was the intent at the time,

http://www.youtube.com/watch?v=gRLyDnp7G_0#t=15

but there could be other things that caused that. My question is really to what specs do I time the engine; 27 degrees @ 3500 rpm like a D-Jet?

[TheCabinetmaker]

Since I built my 2056 with raby 9550 cam and 9:1 cr, it does not like the stock timing. It seems to run best with cooler oil temps when slightly retarded. 24 btdc seems to be the sweet spot. I don't know if the cam made the dif or not.

[gothspeed]

recheck the valve adjustment to make sure they are not too tight (.006" Intake and .008" exhaust, I would err on the loose side, until other things are worked out.). Then vacuum leaks. Your timing at 27° BTDC is close enough that it should not cause as much roughness as in the video. Does the CIS have the 'warm up' enrichment functional?

BTW that CIS installation looks freakin great! (IMG:style_emoticons/default/smile.gif)

[euro911]

Where did you get that CIS system?

(IMG:style_emoticons/default/popcorn[1].gif)

[gothspeed]

I will take a guess that CIS came from an early GTI? (IMG:style_emoticons/default/smile.gif)

[type47]

The CIS fuel distributor in the video is from an early (83-84) GTI. At the time of the video, which was taken at the ECC in Oct, I just wanted to see if the system would run the engine so no AAR or cold start components were operational. The 83-84 GTI fuel distributor has an electrically controlled frequency valve (lambda control) and electronic controls (ECU in particular) are something I was trying to avoid so the current installation uses a fuel distributor from a circa 79 Rabbit which does not have the freq valve. Having said I am trying to avoid electronic controls, I will have the cold start items (cold start valve and AAR) that will be installed in the final configuration. I'll have to learn about the electrical controls for those but in warmer weather, the cold start probably wouldn't trigger and the AAR can also operate off engine temp. I'll check valve adjustment and for vacuum leaks before engine installation. I did use new intake runner to phlenum hoses and the PVC piping was glued so there "shouldn't" be any vacuum leaks in the video. I'm just concerned with the dizzy, which I think is an 009 and if D-Jet timing specs should be used. Thanks ...

[dlee6204]

Jim, I had almost the same question when I was tuning my engine with CIS. For the most part I found that since your setup is "custom" your timing will be custom as well, you just have to find where it runs best. With that being said, stock timing should be a very good starting point.

I think other that a cam difference we almost have the same setup. I found that engine ran just fine at the stock timing but ended up having to retard it a few degrees because of high head temps. I also played around between L-Jet and D-Jet distributors and neither seemed to make a huge difference, both worked well. I can't remember if I tried a 009.

[type47]

... you just have to find where it runs best. With that being said, stock timing should be a very good starting point.

What factors did you use to find that point where it runs best? I read somewhere that a vacuum gauge can help and I have a vacuum gauge in the system. I can install a head temp gauge too if that is one of the factors... Curt also mentioned that he had to retard the timing on his engine.

[gothspeed]

Here is another type IV with CIS project. There might be useful info on there (IMG:style_emoticons/default/smile.gif)

http://www.aircooledtech.com/CIS_injection/

[r_towle]

Let's see.
The 009 advance curve is just plain wrong for a type 4 motor, so you will end up making a compromise of the transition advance at some point in the curve.

Overall timing, and total advance is very closely related to the camshaft (valve timing) so if you have a different profile on the camshaft from stock, your ignition timing will be different.
You may want to ask the camshaft grinder what they suggest.

Overall total advance can also be affected by compression ratio.
Higher CR creates a higher possibility of detonation.
That can be offset by a different camshaft, higher lift, more overlap etc etc...

So, ignition timing is best done (custom) on a dyno or with lots of data acquisition on the open road.

Rich

[euro911]

Back in the early '70's, I installed a cheap generic lawnmower throttle lever under the dash and a long throttle cable to the dizzy on my old '67 bus. Found a good incline and adjusted spark timing for no ping and maximum power (IMG:style_emoticons/default/aktion035.gif)

Who needs expensive dyno time (IMG:style_emoticons/default/happy11.gif)

[injunmort]

euro, that is how indian and dusenberg did it. advance, under load until it pings and retard a 1/4 turn. very much like a mag set up. after changing dist in my chevy truck, timing marks were irrelevant, advance the dist til it ran smooth then drive it under load und backed off timing until it stopped pinging under load.

[gothspeed]

euro, that is how indian and dusenberg did it. advance, under load until it pings and retard a 1/4 turn. very much like a mag set up. after changing dist in my chevy truck, timing marks were irrelevant, advance the dist til it ran smooth then drive it under load und backed off timing until it stopped pinging under load.

That method served me well in my early days, before knock sensors and non adjustable EFI timing came along. Also as a teenager, when I did not have enough money to own a timing light. (IMG:style_emoticons/default/unsure.gif)

This worked well as a fine tuning method also, as the resultant setting will be optimized for whatever elevation one finds oneself in. Although I only retarded a little bit below the 'ping' zone. (IMG:style_emoticons/default/smile.gif)

[euro911]

euro, that is how indian and dusenberg did it. ...

A friend's dad's old Harley '45' is where I got the idea from. I still remember the first time I tried kicking it over - and being thrown over the handlebars (IMG:style_emoticons/default/w00t.gif)