General Tuning Advise (Timing, Fueling vs CHT, Pre-Ign)

[you]

Hey all, after a long hiatus I'm kinda back at playing with my vans tuning and Im not that great at it...things are close but when hunting down optimal for my combo is when i run into issue...firstly do yall prefer to get the timing dead on first then move onto afr or vice versa...ive noticed that just at idle it loves alot of advance and head temps drop (oil temp raises, but in a good way..but..im skittish about running it at load/speed this way...no idea at this moment what it wants when i open it up...in the past i was running it at 12 initial 28 full load or a degree either way...

does pre-ignition or detonation show up in the afr or head temps..i can see how my afr fluctates with the timing adjustments and was curious whether i can avoid the dangerzone by tuning in that manner?

thanks yall...and if it makes any difference im running cis with a jetta ignition in a t4 vanagon

[ps2375]

I don't have any specifics about what an ACVW motor wants, bug I do know that if you change timing, you will need to retune the fuel for those areas. I did a lot of that for my water pumper when I was tuning it mpg's. If you have a CHT installed, I'd watch that closely will tuning.

But having just reread you post completely, seems you have much less control over things. What "jetta IGN" are you talking about?

[you]

thanks for the reply...im unable to "map" fuel or timing...i am able to adjust the fuel curve by picking and choosing which cis air meter i run, idle afr, and overall afr (load enrichment isnt exactly a function but it does seem to somehow compensate, likely from my foot)...as for timing i can adjust initial/full load/and the curve by picking and choosing the springs and vac can...i have a decent collection of parts to tweak with but by no means am able to fine tune like squirters can, lots of trial and error tedium....ign is basically a 1.9l wbx dizzy body with the electrical guts from a late 80s jetta stuffed in with a jetta coil and ign module...sorta a "modernized" version of the orginal hall units used in the cali busses and digijet vans

[Piledriver]

A CIS-E or -M meter can be electrically adjusted, as well as a manual mixture "zero" screw on the DPR, I ran that way for a few years, worked great. The Vanagon ignition module/coil etc are same as WC VW parts from same years, and put out a nice fat spark.

There is also user supplied MS2 custom firmware that can control -E/-M meters as well as ignition and use as a very good datalogger, its worth it just for that IMHO. Programmable ignition with temp based "cold timing" etc makes as much difference as full fuel control IMHO. I keep meaning to try this setup on my 86 Cabriolet, as I have all the spare bits, just no time to play, and the stock CIS+lambda setup works fine.

The only real difference between CIS-E and CIS-M DPRs I could ever find aside from the color is the zero is set differently at the factory---either is usable. You can even tweak the zero pot to set overall mix and run w/o any electronics. A SMC vacuum switch, and/or a WOT switch can be set up to provide load or boost enrichment.

[you]

A CIS-E or -M meter can be electrically adjusted, as well as a manual mixture "zero" screw on the DPR, I ran that way for a few years, worked great.

yup, doin both..warm up enrighment is a pot by the driver next to a cold start bump switch

The Vanagon ignition module/coil etc are same as WC VW parts from same years, and put out a nice fat spark.

its been years since i pulled it all and was running the wiring but iirc module differs both by number and visually...maybe i have the jettas year screwed up...coil might be the same...or im not even sure anymore...i had access to good u-pull its and was going overboard

as cool as ms is i dont have much interest/money/time to play with it....a kiddo is on the way too so for right now its easier for me to tinker with something im more familiar with and actually have....

A SMC vacuum switch, and/or a WOT switch can be set up to provide load or boost enrichment.

i actually have an smc switch but never installed it..when pulling long grades i would occasionally goose the mixture electronically but found it didnt ever affect head temps or performance.....i currently have the idea of using an ac or smog pulley to pressurize meth inj plumbed to a vac controlled egr rolling around the back of my head...but thats for another day.....right now i just want to keep slugs and head from melting