torr

ok here's the deal:

low boost 15lbs, car runs great through all the gears all the way up to redline.
problem: with 25lbs the car sputters and seems like something is cutting out at various rpms, and mostly in 3rd and 4th gear.

i run c16 at 25lbs, also the boost needle is not steady and flickering at this boost level. at 15 it stays steady. for ignition i have: msd sci-l, msd hvc coil, msd cap, ngk blue wires, ngk "8" plugs. how long do these plugs last? `all the ignition stuff is new except for the dizzy. however i did swap dizzies from another car and still same problem. fuel pump is walbro 255.

when i set the boost to a lower boost level say 18-19 the car runs good. anywhere around 22 and the car stutters. the car is tuned to 25 though.

anybody experience this problem and can maybe help.

R THIS

sounds to me like the spark is being blown out.. check your plug gap...

also do the plugs look lean or have any signs of detonation???

i find in my car that the plugs start to deteriorate in performance after around 1000 miles... im running NGK ZFR7F11's

torr

well i gapped them to 28, and i'll have to check the plugs in the morning. but i think i may have a ignition timing issue.
what causes the spark to blow out?

R THIS

if the gap is too large, the pressure of the air blowing into the cylinder can redirect the spark, making it not contact the electrode

like holding a lit lighter and blowing on the flame

with an msd you should reduce your chances of this happening, but you are running a fair bit of boost... once you rule out timing and tuning aissues you may want to try out a set of plugs with the surrounding electrode... it doesnt have a tab it has a circular cover, that will protect the sparking of the plug.. im not sure exactly what they are called, but they are race style plugs

torr

ok question about timing, since my car was tuned do i need to know what the tuner set the ignition timing to, or can i just do the timing boost calculation, 25lbs should be about 13 degrees retarded.

Antilag

jesus thats to way off for me. I have mine idiling around 26 and at high rpm's and 280 map and up im at 19 degrees. but then again I'm at 4600 feet elevation. Try this, gap your plugs at 18-19 with high boost. That usually helps alot. Tell us how it goes. I set mine at 18 and mine does just fine.

torr

ok, checked the plugs and they are fouled, flat black looking. i'll throw some new ones in and hopefully that fixes it.

99B16Si

if theyre fouled you probably have a problem with your air fuel ratio also. look into that before you foul out another set. with c16 and 25psi you chould have an af ratio of around 12:1 and u can be a little more aggressive than 13 degrees with youre timing(id try 15 or 16

torr

hey so when i set my timing all i have to do is jumper the service plug, let the motor run to operating temps, shine the timing light at the pulley tdc's and set it at 16 degrees retard by turning the dizzy towards the front of the car right? how do i know that it'll be at 16 (is it the red line on the pulley) without having a digital timing light.

torr

figured it out, timing and plugs were changed.