timing on a gt42? s372, s400sx. (all around the same size)
 

hey guys i was just curious to see how much timing you guys are retarding on the Tmap. on a turbo with the size of a gt42. static timing at 0 degrees, as well as physically. im doing one degree per pound for boost for now until i have more knowledge of this. thinx

go through the posted timing maps in this section and get an idea for yourself

1 :1 is conservative but good enough for a base
usually the first couple of psi can come at stock ( 24 BTDC ) timing and so skews the magic sum just a little

if the motor is ported you may wish to use 10BTDC ( there abouts ) as the static timing which will steady the idle for most worked engines

generally,, most will have 22-26 BTDC at load ,, no vac,, no boost
( 22 -24 at peak TQ revs and then slipping up to 26 degrees at higher revs beyond peak )

leading/ trailing split is usually around 15 degrees and will taper closer at boost and revs slightly
- about 8-10 degrees at peak TQ revs

from all that you should be able to draw a fair mud map

PS ,,numbers i have given above are true to TDC

if you just whack them into a micro that is timing calibrated their way
these will all be low by 5 degrees due to micos's usually being setup at the -5 leading timing mark

keep that in mind,, when reading micro maps,, and comparing others
-- some are setup on -5,, and are skewed , some are setup for true TDC numbers

if you remark the pulley for a 10 BTDC mark and time to it,, you have true numbers
( easy as for an FC ,,, as they already have a 15 degree split marked for -5 to -20 , use this gap with calipers and project it clockwise form -5 )


on FD,, easier,, timing mark is -20,, but the pickup tooth before that is +30
-- so mark the pulley where this tooth points to,, == 10 BTDC

bumpstart. my experince with heavily ported mild port engines is different. to get a smooth idle they need to run 5atdc otherwise its lumpy. putting in your timing figures will make it idle strong and pull more vaccum but its lumpy.

i know this changes with different styles of mild port. i guess most of them dont open very early and thats why the above works but any mildport that opens(practically almost as early as a bridgeport) will not idle smooth with the above timing figures in my experience. the rest of what you have said i agree with.

thnx for the help guys. i kno im posting this a bit late. but i have my static at zero on the hand controller. i also just wanted to make something clear , the tmap takes away or adds timing to the rpmT right? so if on boost my rpmT is at 25deg, and my Tmap is on -10deg. my total timing is 15deg correct?

If im correct, then what total timing are you guys running on a similar turbo?idc at what boost. just to get a clear idea.

I am just running 1:1 for now until i have further knowledge. also does the amount of timing retarded depend also on the size of the turbo? thnx alot guys

hey guys since the topic of this thread relates to something also that ive been thinking about, what type of total timing are people running with the introduction of meth injection? , i read howards thread an i see he ran 16 deg with an 11 deg split at 20psi but what about the timing before hitting full boost? and in his thread i noticed he finished the story kinda short without ever reaching 25psi =\ what timing would you guys run?

forgot to mention this would be introducing the meth at 5psi, similar to howards setup.

introduce the meth at higher point, u might be able to add some timing when the meth kicks in
you been lost you gotta take me for a ride !!