Engine timing

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tiagosantos
Posts: 389
Joined: June 20th, 2010, 12:10 am

Engine timing

Post by tiagosantos »

Ok, another round of noob questions :)

Got my car all tidied up and ready to go today and checked timing as part of the process, as usual. I switched to the pertronix electronic points a few weeks back and this was my first time checking the timing after the switch. I also had to remove the distributor a while ago (don't ask..) so I wasn't sure what the timing would be at all. My old engine had a fancy degree wheel but the new one only had TDC - and I bolted everything in before I remembered to mark the pulley (which reminds me, I need a damn whiteboard).

I tried measuring it up today without pulling the fuel cell and couldn't do it, so splurged on a timing light with an advance dial.

Now for the actual question - when you're adjusting timing, how much does the mark flutter/sputter around? I got it sort of around the mark, but it really isn't stable at all, probably jumps around 1, maybe 2 degrees either side of the mark. Also, timing should be checked at 3000rpm, but how much should it change beyond that, if at all?

I think I've got it right, but could use some reassurance.. Or better yet a warning that it's all about to blow!! :)

Thanks for all your help so far guys, really appreciate it.
SR Racing
Posts: 1205
Joined: June 24th, 2006, 1:58 pm

Re: Engine timing

Post by SR Racing »

Tiago.

You want the timing set at 36-37 degrees when you are above 2500+ RPM. After that point it should not advance (or retard any more.) If it advances another couple degrees, then go ahead and set it for 36-37 max. If it retards, your distributor is messed up. (1 degree or so won't hurt.)

+/- one or even 2 degrees of flutter is not terrible, it just indicates some distributor wear or gear lash, etc.
billinstuart
Posts: 201
Joined: July 17th, 2006, 8:53 pm

Re: Engine timing

Post by billinstuart »

some electronic pickups retard timing at high rpms..1-2 degrees per thousand. what's wrong with points..you've got plenty of dwell time with a 4 cylinder engine?
tiagosantos
Posts: 389
Joined: June 20th, 2010, 12:10 am

Re: Engine timing

Post by tiagosantos »

Thanks guys.. I wrote a message thanking you this morning but forgot to hit submit, apparently..

Nothing wrong with points as far as I know, I'm just two generations too wrong to be messing with them :P Nah, I bought a data logger and thought I'd get a cleaner rpm signal with the electronic ignition.

Thanks again!
SR Racing
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Joined: June 24th, 2006, 1:58 pm

Re: Engine timing

Post by SR Racing »

billinstuart wrote:some electronic pickups retard timing at high rpms..1-2 degrees per thousand. what's wrong with points..you've got plenty of dwell time with a 4 cylinder engine?
?? :?: . All of the legal electronic ignitions don't and can't do this. They also don't suffer point bounce and the dwell is constant. Yes, dwell is not an issue except that the cam follower wears on a set of points, thus increasing dwell and reatrding ignition timing.
SR Racing
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Joined: June 24th, 2006, 1:58 pm

Re: Engine timing

Post by SR Racing »

tiagosantos wrote:and thought I'd get a cleaner rpm signal with the electronic ignition.
You typically do. Another advantage of the electronic ignition,
tiagosantos
Posts: 389
Joined: June 20th, 2010, 12:10 am

Re: Engine timing

Post by tiagosantos »

Yup, I never got around to using the data logger with the points still in the car, but the rpm signal seems pretty decent with the pertronix. I'm very glad to not have to adjust the points gap again too!
brian
Posts: 1348
Joined: June 26th, 2006, 12:31 pm

Re: Engine timing

Post by brian »

A common cause for bouncing timing light pulses is a worn dist. shaft. Generally speaking, and Jim knows this stuff better than I, the old coil system, combined with metal core spark plug wires, makes our tach signals way too "dirty" for most DA systems. Contemporary DA systems are designed around more modern ignitions. Many DA systems have gone to magnets on the pulleys with halo switches to provide a clean square wave signal for modern DA systems. It took me almost a complete season to clean up my tach. I have part numbers for anyone who would like to do this.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
billinstuart
Posts: 201
Joined: July 17th, 2006, 8:53 pm

Re: Engine timing

Post by billinstuart »

Timing retard is an unintended consequence of any electronic device..the processing time, even though minute, translates to unintended timing retard. Seems like the term is "skew rate". Some systems/devices are worse than others with regards to the timing retard issue.
Matt King
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Joined: December 23rd, 2008, 1:44 pm

Re: Engine timing

Post by Matt King »

I've got a Pertronix in my car now and the RPM signal to my AIM system is garbage--no better than when I had points. Like Brian said, it's still an inductive ignition system and the coil provides a very dirty signal. I haven't tried an RPM filter yet, which might help, but many drivers use a magnetic pickup on the front pulley for this very reason.
tiagosantos
Posts: 389
Joined: June 20th, 2010, 12:10 am

Re: Engine timing

Post by tiagosantos »

I bought an MSD tach adapter magic box thing before Brian told me about the hall effect/magnet setup.. In hindsight, that would have been much cheaper, but the MSD box seems to be working fine!

Thanks for all your replies. I'll give it another go next weekend and maybe try swapping my spare distributor in, see if it helps the bounce at all.

Cheers :)
brian
Posts: 1348
Joined: June 26th, 2006, 12:31 pm

Re: Engine timing

Post by brian »

Here's a follow up to my post. The halo or magnetic proximity switch you need is made by Cherry and is part number 513279. I got mine from Jameco electronics.1-800-831-4242 for $9. Sure beats what the DA companies want. It's has a aluminum threaded body for mounting and will live in the harsh environment of the engine. I made a bracket that shares the oil pump studs and captures the mag field from a magnet that I JB welded to the front pulley. Super cheap, super clean signal and no extra battery power required.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
hardingfv32-1
Posts: 1014
Joined: December 1st, 2006, 8:01 pm

Re: Engine timing

Post by hardingfv32-1 »

The AIM ignition filter works fine for their systems.

Brian
brian
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Joined: June 26th, 2006, 12:31 pm

Re: Engine timing

Post by brian »

I thought about their filter until I learned that everyone's system is different and there would be no guarantee that the Aim unit would work on my system. The MSD products I tried did not succeed. The clip on plug wire device would work but was a real pain during engine changes and was seriously fragile looking. Nice thing about the halo approach is there is no electrical connection between the ignition and the fragile CPU electronics.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
pillowmeto
Posts: 103
Joined: January 5th, 2008, 12:54 am

Re: Engine timing

Post by pillowmeto »

The clip on wire types can break after repeated install and removal, but being inductance, are very simple. I have a bunch of them at work and I just zip tie the pickup wire to the spark plug wire. The clip is simply to hold it in place and serves no other purpose.
SR Racing
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Joined: June 24th, 2006, 1:58 pm

Re: Engine timing

Post by SR Racing »

billinstuart wrote:Timing retard is an unintended consequence of any electronic device..the processing time, even though minute, translates to unintended timing retard.
Bill, with delay (either mechanical or electrical) there is no RETARD of the signal when the RPM goes up. The only affect at higher RPM would be the advance wouldn't increase as much, but not retard. In any case, you would not be able to see this lack of advance with your timing light. The only retard that you might experience is due to a worn distributor. Many of them will drop back a degree or two when the get past the full advance curve. This is a mechanical issue.
SR Racing
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Joined: June 24th, 2006, 1:58 pm

Re: Engine timing

Post by SR Racing »

In regards to the electronic points and noise issue. There are 2 issues, dirty signal and coil ringing. The points are very dirty electrically. A good condensor will clean this "dirt" up a bit. The coil on any inductive ignition will "ring". This ringing USUALLY doesn't bother a decent tach pick-up. In all the AIM (or other) data systems we have seen, good points, and condensor (along with good wiring practices) fixes the issue.
(Good wiring practices = proper routing of wires and GOOD grounds without ground loops.)

When using the Pertronics on all of our and customer cars we have never had a problem. (We have had a couple calls from customers that did have problems, but when advising them to change points condensor and a dwell check, we didn't hear back.)

Many other after market ignition systems do provide a perfect square wave to the D/A or tach. (MSD, etc). They have do this with a separate circuit since most multi-fire at low RPM.

Most D/A lines are a very high impedance input. They are susceptable to noise.

It is beyond the range of this discussion, but cleaning up the signal with a simple resistor and capacitor in the line going to the D/A is pretty easy.
SR Racing
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Joined: June 24th, 2006, 1:58 pm

Re: Engine timing

Post by SR Racing »

brian wrote:Here's a follow up to my post. The halo or magnetic proximity switch you need is made by Cherry and is part number 513279. I got mine from Jameco electronics.1-800-831-4242 for $9.
Doesn't look like Jameco carries that one any more. But they have several others that would work fine.
smsazzy
Posts: 703
Joined: June 24th, 2006, 5:56 pm

Re: Engine timing

Post by smsazzy »

I have an AIM Tach filter if anyone wants to buy it. It is brand new. I will sell it for 75% of whatever a new one goes for. Send me a PM or email if interested.
Stephen Saslow
FV 09 NWR
hardingfv32-1
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Joined: December 1st, 2006, 8:01 pm

Re: Engine timing

Post by hardingfv32-1 »

Jim

Please expand on "proper routing of wires and GOOD grounds without ground loops".

Thanks
Brian
SR Racing
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Joined: June 24th, 2006, 1:58 pm

Re: Engine timing

Post by SR Racing »

Keep the ignition wires (primary and secondary) away from any dash input wires. Make sure your grounds are GOOD grounds. Paint scraped away, etc.
Make sure your plug wires are secure and the ends are on well. Any arcing internally will still fire a Vee easilly but it is also a great RF transmitter.
Make sure your distributor clamp is tight. That is a ground for the points. Any loose connectors in the primary ignition wiring will also transmit lots of noise. Crimp all connectors well (DO NOT SOLDER alone). Heat shrink on the wire at the connector will help to keep vibrations lower. Put some clear silicone (RTV) on all of your primary wires, switch screws, etc. This also keep vibration down and keeps things from loosening.

Make sure your ignition supply wire is a MINIMUM of 14ga stranded automotive wire. Even 12ga is better. This circuit consists of the line from your kill switch, to your ignition switch, to your coil. It is going to be a total of 10-12 ft of wire. The ignition primary can draw as much as 5 Amps.
The more the current the more the voltage drop at the coil. The more the voltage drop across the wire the more RF (noise) that is generated. (and the less spark you get at the coil.)

BTW. A Vee with a standard coil points and condensor has more than enough energy to fire these low compression engines. DO NOT spend money on solid wire or any real exotic plug wires. Use STOCK or any good street ignition wire. Solid wires will only make noise and burn up rotor tips and distrubutor caps faster. The plugs will avalanche at about 15K volts or so with ANY wire.

The only advantage of the Pertronics and Compufires, etc, is you won't have to adjust dwell or timing anymore. (Which is a significant advantage) In our tests here, they all eliminated some splater and RF noise and gave you a couple thousand more volts of OPEN wire voltage. So you can get eg. 28K volts instead of 26K volts. Since the plug with standard gap fires long before that (see above), there is no performance advantage. We have tested many systems on the dyno. They do NOTHING for a Vee in performance.

How is that?
tiagosantos
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Joined: June 20th, 2010, 12:10 am

Re: Engine timing

Post by tiagosantos »

Hey Jim, maybe you should write a book, eh?

:lol:
billinstuart
Posts: 201
Joined: July 17th, 2006, 8:53 pm

Re: Engine timing

Post by billinstuart »

SR Racing wrote:
billinstuart wrote:Timing retard is an unintended consequence of any electronic device..the processing time, even though minute, translates to unintended timing retard.
Bill, with delay (either mechanical or electrical) there is no RETARD of the signal when the RPM goes up. The only affect at higher RPM would be the advance wouldn't increase as much, but not retard. In any case, you would not be able to see this lack of advance with your timing light. The only retard that you might experience is due to a worn distributor. Many of them will drop back a degree or two when the get past the full advance curve. This is a mechanical issue.
The unintended effective retard is indeed a function of processing time. When you view the event duration time of a running engine, any processing time does indeed relate to unintended retard of the ignition event. Once the mechanical advance is maxed out, the spark event is slightly delayed due to signal processing time. This event duration time is significantly short enough to render multiple spark devices ineffective above about 3000 rpms or so.

Let's say the processing time is a second...the spark won't occur for a whole bunch of revolutions of the engine.

I see it on my distributor machine on electronic distributors. Even regular old points distributors appear to retard slightly at high rpms..takes a measurable amount of time to flash the tube in the machine.

Now, does it affect power? Probably not...we've already set the timing for maximum safe power..all we're really discussing is exactly what this "optimum" timing number is.
SR Racing
Posts: 1205
Joined: June 24th, 2006, 1:58 pm

Re: Engine timing

Post by SR Racing »

billinstuart wrote:The unintended effective retard is indeed a function of processing time. When you view the event duration time of a running engine, any processing time does indeed relate to unintended retard of the ignition event. Once the mechanical advance is maxed out, the spark event is slightly delayed due to signal processing time. This event duration time is significantly short enough to render multiple spark devices ineffective above about 3000 rpms or so.
Yes, the msd type ignitions do stop multispark before about 3500, but this is an issure of dwell time not not electronic transit time. (As an example, a coil pack over system can mutispark forever (almost :lol: )

With a 4 cyl VW engine we have up to twice the potential dwell time as a V8. So it isn't much of an issue. I don't believe you can see 1 degree of retard in our igntision due to transit time until you get to maybe 10,000 RPM :lol:
There would be much greater delay time in your timing lamp and that is what you COULD see.

Yes the issue IS THERE, but of no practical interest in performance.
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