>it sucks you just went thorugh a piston or two. yes,
>detonation is bad. No, detonation is not that hard to avoid
>in most situations. if you don't lean your car out a lot
>with an afc, or an afr, or any other kind of piggy back
>device to run boost, then once you hit 0 atmospheric
>pressure, your ignition timing should hit 18 to 15 degrees
>advance on the spot. MAYBE 21......no higher. if it
>doesn't, you are probably using an afc or some other device
>to make the ecu not see "full" voltage from the map sensor.
>it is perfectly safe to run over 8 psi of boost with 21
>degrees of spark advance. The stock thermostat is
>relatively high for bosted applications, but it has been
>proven to work. a 160, 170, or 18 degree thermostat would
>work better, but the 195 does do the job. several cars
>boost on it and have boosted on it for quite some time. you
>ABSOLUTELY ABSOLUTELY ABSOULTELY CAN'T trust the oxygen
>sensor voltage alone. you will ABSOULTELY blow your shit up
>if you do. I remember helping 96venger tune his car. he
>had the corbin meter in his car, and it was reeding .999 to
>.998 volts when we first got his car runnign with the 440 cc
>injectors. at .999 volts, the car shouldnt' even be
>"running".........let alone have a huge hill in the middle
>of the air/fuel ratio curve. so we put the 2.72' disk in
>his car, and richened up the middle enough to flatten it out
>on the scale to around 11.5 :1 across the board from the
>time the pedal went full throttle to the time we let
>off.........the voltmeter said .99 to .98 all the way
>across..........guess what the afc said........... .96 to
>.95 all the way across. if you want to push your car past
>12 psi, you REALLY need to hav eyrou car tuned with multiple
>instruments (i.e. egt gauge, wideband o2 sensor, and if
>possible aftermarket knock sensor). the factory oxygen
>sensor is NOWHERE NEAR accurate enough to keep your car
>runnin if you push it. if you run mroe than 12 to 18 psi,
>you really need to be in the 11.5 to 11.3 range in air/fuel
>ratio. if you run more than 18 psi, you really need to be
>in the 11.3 to 11.0 range. if you run less than 12 psi, you
>can probably get away with running at 12.0 air fuel ratio,
>but not for long if your car isn't consistant (due to a poor
>fuel pressure regulator). if you run leaner than this, you
>"will" be buying new pistons, and if you run mroe than abotu
>21 degrees of timing at ANy of the above suggestions, your
>pistons and head and cylinder walls WILL look like someone
>went crazy with a tiny chizel around every corner and edge
>fo yoru combustion chamber and pistons. just keep timign
>around 18 to 20 degrees max under boost, and boost pressure
>under 12 psi on stock pistons and under 20 psi on
>aftermarket forged pistons on 93 octane gas, and you will be
>fine. if you don't.......you will be building another
>engine.......trust me, I know.

Relying on a rich fuel mixture alone is not good for max HP when boosting. Remember, anything richer than 10.1:1 will cause detonation also, just as easily as too lean of mixture. Then only reason is you can run soo much boost pressure without timing retard is becasuse of running on the edge of very rich conditions, thats not good for power. IMO, you will make more HP, with a slightly leaner air/fuel mixture, and retarded timing at higher HP. My EGT's never went above 1575 degrees when i was boosting 10 psi. I still cracked a piston. We HAVE to pull timing at one point or another. Its just plain physics.
Your theory of tuning is by running so rich, that it cools the intake charge enough to avoid serious detonation. The stock o2 is by far not perfectly accurate, but its pretty close overall IMO. If it wasnt, the the readings it gets would be totally inaccurate when just normal driving around, and your engine would run like crap, and get horrible gas milage. The o2 alone is what sets the Short term fuel trim, and Long term fuel trims on our cars. It HAS to be somewhat accurate at oxygen measurement. Not perfect, but close. I just wish my theories could be tested out using a dyno. Try mega rich fuel mixtures for high boost. THEN try retarding timing and leaning out fuel mixtures to where they really should be. I'd be willing to bet money that higher HP will result with leaner fuel and retarded timing. It makes sense anyway..

>oh, and also, how can the J and S safegaurd retard each
>cylinder's ignition firing when on our cars 2 cylinders fire
>at a time (waste spark). that doesn't add up to me.
>

The J&S can pull timing from each cylinder. We have 2 coils, one for cylinders 1 and 4, the other for cylinders 2 and 3. BOTH of these sets of cylinders fire at the same time, BUT only one cylinder is on the compression stroke, and the other is on the exaust stroke. So lets say cylinder 1 fires and gets detonation. The J&S reads the knock, and knows that cylinder 1 just fired, and it will remember to start to retard cylinder 1 NEXT time IT fires. So it "knows" to SKIP the next following spark trigger signal for the same coil, because now the next following signal is going to spark cylinder 4. The next spark signal after cylinder 4 is back to cylinder 1, so only then does it retard spark. Make sense? The unit listens for knock over 100 times a second.

Let me ask this also. How many of us boosted 420A guys run at 15+ psi of boost, and have actually dyno tuned our cars, using timing retard and A/F ratio adjustments? I dont know, I really cant think of many..Most 15+ psi guys just inadvertantly pull timing or run mega rich and just run it. I think we are all missing out on some good, serious HP here...Fuel tuning alone just isnt going to net max HP, we have to ignition tune also. I think we need to retard timing, and run closer to a consistant 12.1:1 to 12.5:1 A/F ratio under boosted conditions, or slightly richer, but thats it. Of course, this is all my theories anyway

13.5 @108 MPH-2.2 60ft(stupid FWD!)
S16G @ 18 PSI/FMIC/Running on MegaSquirt II (Now with sequential
fuel injection)
My webpage: http://eclipsed4evr.home.comcast.net
-1998 Mitsubishi Eclipse RS-T- "Toy"
-1992 Plymouth Laser Turbo AWD(SOLD)
-2000 Honda CR-V(daily)