XR700 or Pteronix

[paedrig]

1977 (early) 280Z

cold air, XR 700 optical ignition, urethane bushing kit, tokico illuminas and springs (all4), some other stuff i'm forgetting

Haven't been on the forums in a while and saw posts about the Petronix. (still researching but getting there) There was a post in the HelpMe section where a user said he switched from the XR700 to the Petronix. I have the XR700 and it works. My issue is it's nearly impossible to tell if my timing is actually accurate due to how the whole thing gets installed. Is the Petronix any better? Should i do the 79ZX Dizzy instead. Megasquirt with fire is not in the budget for another year or two, so it's not an option.

Opinions? I'ver heard lots of debate about Petronix vs. points (the other site, current posting) but none really about XR700 vs Petronix.

Thanks in advance

[LeonV]

You have a 280Z, and hence, electronic ignition. There is no need for the Pertronix unit. Not sure what you mean with the "timing accuracy" statement. That can be checked with a timing gun.

The only real upgrade you can make is going to a programmable, crank-triggered system, such as EDIS. That can be controlled by something like Megasquirt or Megajolt.

My EDIS system cost me around $400, best money I've ever spent on the ignition system. If you don't want to commit to that, just make sure your current system is in good order.

[paedrig]

The timing issue I was referring to is this;

Due to how the photo eye mounts on the distributer housing to replace the magnetic pickup allows for a lot of variance. Yes, there are instructions to "set it to 0 BTDC" but it is not an exact science. Setting the #1 piston at TDC then setting the photo eye to trigger at about the same time by adjusting where it's mounted in reference to the rotor. I would say it has a 5-10 degree innacuracy, therefore when using a timing gun your getting only a best guess as to what your timing really is, so basically are timing it by feel or sound. Not an exact science. The reason for the upgrade is because on the 77's the electronic ignition requires the use of that gigantic elctronic ignition box under the dash of the passenger side. Using the XR700 or the Petronix eliminates that from the system and thus, you can use high output coils etc. Installing a 79 dizzy accomplishes the same thing. (those stock ignition modules under the dash are very expensive to replace)

I originally planned on something like megasquirt with the MSD 6A ignition, but it still requires the use of a distributor. I will research the EDIS system and see if it blows my skirt up.

Thanks for the reply

Paedrigz

[Zed Head]

You're not measuring the correlation of spark and distributor, you're measuring the correlation of spark and piston position.

If the mark is at zero when the piston is at TDC, then the flash of the timing light will be accurate. That's why a timing light is used, instead of setting things at the distributor.

[paedrig]

Aha! Thanks for the clarification Zed Head. I guess i can relax knowing my timing is in fact accurate. That being said, over the last (decade i think) since having the XR700 it works fine. I burned one out once (got wet) replaced with a new unit (now waterproof) They work well and that's good enough for me reliability wise.

Thanks all.