ignition timing and nitrous oxide

Cheapstreetduster · Post by **Cheapstreetduster** » Sat Mar 12, 2005 12:37 am

last season i had some destructive problems with nitrous
and i think i have concluded that i may have had to little ignition lead
we popped a couple of head gaskets and neuked a piston and a cyl wall
..
after the long winter and deliberation ..
i have been coming to the same conclusion but its not the one i thought it was while i had made the tunning changes to the motor
i had some minor detination on 1/4 mile tracks that didnt show up on 1/8th mile tracks..
so while at the 1/4 mile track i retarded the ignition lead 2 deg from 30 to 28..
then i started seeing the detination at teh 1/8th mile tracks...
symtoms.. no top end or high gear power.. black specs on the porcelin cone.
loss of ring tension after tear down
a couple of blown head gaskets and one pass that eat through a piston and the cyl wall. requiring a sleeve..
the strange thing was that more often than not i was seeing rich conditions.. but alot of discoloration on the header wrap just out of the head at the primary pipe turn...
we had some lifted top ring groves and to piston tops with broken sections on the winter tear down..
now i am thinking it was to retarded ignition wise.. causing the piston to get to hot ..
the fat jet mixture i believe caused the piston tip ring land failures compounded with the late burn...
could this be the case..
if so i cant belive i figured this out now after all i went through last season and i am now going to a different class due to rule changes and wont be using no2 any more....
if i am correct ? its hard to swallow because i wont be able to confirm more power or improved ets because the class change...
i would still like to get some confirmation on what you think...
just to finally complete my thoughts ...
anyone have any input...
cheap

ozrace · Post by **ozrace** » Sat Mar 12, 2005 8:31 am

Late ignition timing should cause the piston to be exposed to less heat. Peak pressure will be less, and the amount of time the piston is exposed to heat is shorter, so more heat will go out the exhaust.
It is fairly common for engines with efficient chambers, and a big load of nitrous, to leave the start line without much timing at all - maybe 10 degrees. Doesn't seem to cause any problems.
I think heavily turbocharged deals use the same approach.

Cheapstreetduster · Post by **Cheapstreetduster** » Sun Mar 13, 2005 1:12 pm

huh,,
so do i have to start all over looking for my answer?
i was thinking late igntion might cause snowballing of the cyl temps or exhaust vavle..
i would like to know/figure out what was happening just to come to a conclusion..
it wanst always a part falure with the passes but i stil dont know wich way i should have gone to get it right..
jim