> By retarding the time
>the plug fires the mixture, it helps cool down the
>combustion temperature be cause it makes the plug fire at a
>later time in the cumbustion process, later after max
>compression is made, therfore lower combustion temperature
>keeps it from detonating.


you will have a "less chance of detonation' if yo udo that, but you hav eto rememerb, I dont' run a vc-1,vc-2, mising link, or anything like that, and I had the stock ecu from murix's car in my car for quite a while. under boost, I was getting about 15 degrees of spark advance. if I wa sto retard timing 5+ degrees more than that, the car woudl make "no power" (tried it on the dyno.......it was pathetic. can you say 305 hp on MY car with all the flow work, all the cams, everything, etc. with 18 psi). plus my egt's with 12.3"1 air/fuel ratio were through the roof (I was getting 1650 out of the center 2 cylinders on the dyno!............which come to find out is too hot fo ran engine. got the piston to prove it.) retarding timing does not cool combustion temperature. it reduces the chance fo it being soaked into the motor. insted all that head goes out the exhaust valves and through the valve stem seals. watch yoru egt's close when you retard timing. they will go up with NO changes except reduced timing. that is why. it maybe safer for the motor as a whole, but it reaks havoc on the valves. I know a supra guy back in the day that retarded timing by a whim and tuened a few of his exhaust valves into butter (he was getting about 16 degrees base timing also)! if you tune fo ra higher air fuel ratio, you will have a much more radical ignition of the fuel, which will increase heat and force, but retardign the timing will push much of the heat and potential force through the exhaust and turbo, resulting in extreme spoolups, and holes in pistons. if you run richer, you can have a much mroe controllable burn, and use more of the energy from the combustion to produce torque, and still have enough exhaust heat left over for good turbocharger effiency (assuming a low amount of convetion through the exhaust manifold and turbine housing).


Does anyone think that you are
>getting the maximum HP out of a 11.0:1 fuel mixture? Seems
>to me that there can be more power from cumbustion if the
>mixture contains less fuel than that, its just my idea
>anyway. I have another queston for Armond, as he seems to be
>the leader here with high HP 420A motors.. Did you use ANY
>form of ignition timing retard when you dyno tuned yours or
>any other 420A's??? I would really like some more of your
>input.

when we tuned mark's car (96 venger) we used 0 timign retard due to the fact that his car was making a consistant 18 degrees of timing to begin with. his car also did not rattle on the dyno, and it produced a save ammount of hp consistantly. The manual boost controller that is on the car (turbo xs) is really flaky, so no more than 12 psi was ran on the dyno. the turbo woudl overshoot about 4 psi with this boost controller, and even at the 16 psi spike , the car held rock solid and made consistant hp, and did not rattle. we raised the car all the way to a consistent 15 psi (which resulted in a 19.5 psi spike and the car made a save, noise free 270 hp "after" the spike with an air/fuel ratio of 11.3:1 and considerably low exhaust gas temperatures. no one at the dyno felt that it was safe to push the car with a "consistant" 20 psi spike on 93 octane with an "average" of 18 degrees advance, even at 11.3:1 air/fuel ratio, so the boost wa sbrought back to 12 psi. as far as I know, the car still runs pretty rock solid, and still has perfect compression. it makes around 240 hp at 12 psi on average, but ignition timing "can be flaky" with these cars, and can increase or decrease on a whim. the car ahs made as much as 260 hp at the same boost level randomly (no doubt due to ignition timing. he runs the missing link. that is the "MAIN" reason to keep an eye on timing.....glitches. MuRix's car hasn't been dyno tested in years, but it ha sbeen "almost there" countless times. his car however has performed well with 0 retard at 18 psi with little aftermarket help. no visible damage to the spark plugs, and no abnormal changes in compression. ran like hell to say the least. I hav eanother friend that frequents here that ran 12 psi on stock pistons for about 2 years with an aftermarket head gasket with NO timing retard. no afc either. just a standard HRC stage 2 turbosystem, cams, and a thick head gasket. his car was strong as hell also. as soon as the afc went on and the car was leaned out 30% across the board..........dents in the pistons formed, putting the motor out of commission a few times. I had no part in tuning this car, but it is blatantly obvious now that those issues were caused by "abnormal timing". the car was even relatively rich (once again by his oxygen sensor), and the motor still failed.......a few times. you can't run rich and run "all the timing you want". that's not what I am saying. you have to run the "right" ammount of timing, and you have the combustion temperatures in a "safe range" at the same time. too much timing will enlarge existing problems. too little fuel will create more heat than a normal motor can stand at 220 psi of compression pressure. the higher the compression pressure, the more extreme the danger. if you run over 12:1 air fuel ratio when yoru turbo is in it's island effiency or higher, you will fill the cylinders with enough explosive to cause uncontrolable damage. at lower pressures, the density and speed fo the air is thick and slow enough to only use small ammounts of fuel, therefore resulting in lower ammounts of force overall. the mroe more air you blow in, the mroe fuel it takes, and the more potential there will be for force........until you cross that barrier where the ammount of air requires enough fuel to either work the motor, or "work the motor over" if you know what I mean, and if "that much fuel" isn't burned properly, you are bound for dammage. with the 20G, that point is about 15 psi. running leaner than 11.5:1 at lower boost levels is really just "getting away with it". with the same ammount of air flow on a smaller motor, that would result in more boost, and would hav ethe same result as running the increased airflow on the larger motor (in this case ours). of course this is all in laymans terms, but trust me. after going through 4 engines, you tend to learn a few things. not sayin I know everything, but I know what "lean" is now.

A.D.P.
"...If you do too much, people become dependant. If you do to little, people loose hope. If you do it right, people won't be sure you've done anything at all."
bring it on............

A.D.P.
"...If you do too much, people become dependant. If you do to little, people loose hope. If you do it right, people won't be sure you've done anything at all."
bring it on...........