Exhaust Gas Recirculation (EGR) and ignition timing

[type4org]

Hi guys,

According to this article...

http://www.asashop.org/autoinc/nov97/gas.htm

it seems that ignition timing on many engines that had a factory EGR system was different from non-EGR engines, it was advancing quicker because mixing in exhaust gases helped to cool the combustion chambers and thereby allowed more aggressive timing.

On my '74 12 wagon with (EGR-equipped) EC engine the system has been disabled a long time ago because the filters simply are not available anymore. Now I am wondering if I am doing the engine a big disservice (chance of pinging because of unsuitably aggressive advance curve) and should try to locate parts to re-enable the EGR system.

Anyone else have experience in engine changes (positive or negative) due to a disabled EGR system?

jens

[raygreenwood]

I would doubt it highly. The advance level is the same...meaning what degrees it advances to. The only difference may be...the speed at which it adds that advance in. Bear in mind, that the fuels available now are superior to what was available on average in the mid 70's....lead additive not really a factor after a while when all else was taken into account (ie low octane, new anti-foam additives , alcohol, high sulphur crude sources etc.) You should notice no differences. Generally, the higher rate of advance was also necessary because the overall compression on the California engines and the 1800's was low. I have found that as long as you make sure that your engine does not over-advance...you can generally interchange any vacuum can from any type 4 with minor adjustments. Ray