More Horsepower. More Torque!!

[David A. Cooley]

>>From what I've seen, it depends.  Some custom chips are open-loop
>(offroad) only, while others (especially Calloway and Lingenfelter)
>actually attempt to make their calibrations 50 state legal (unless you
>request an offroad chip).  Others just shoot for 49 state.
>

Actually, the chips are still closed loop... (looks to the O2 sensor for
feedback) until WOT, then it's still not open loop, it's in Power Enrichment
mode... It ignores the O2 sensor and adds additional fuel.  The fuel may or
may not be trimmed by the long term learning of the PCM depending on the
cal...  The offroad only designator just means they didn't take the time and
money to have their chip emission certified.

>Speaking of the ZR-1, I'm looking for ideas on knowing how lean
>to go when tuning a car with cats.  The optimal method is
>supposedly to drill a temp probe into the cats and measure the temp
>of the cats to make sure they are running hot enough (hot enough to
>protect the cats from being damaged).  Does anyone have any other
>methods short of that?
>
>I've heard the Buick GN guys shoot for something just under 800 mV
>reading on the O2 sensors for max performance, but I don't know of
>any data to back up that when the O2 sensor reads 800 mV, the cats
>are hot enough.  Same for an Air/Fuel sensor - you can shoot for a
>certain ratio, but does anyone have any ideas if the cats are
>getting enough fuel to protect them?
>

You cannot use a standard O2 sensor to judge your mixture...  800mv in one
car may be 12.5:1 and it may be 13.9:1 in another...
an EGT guage or a wideband (A/F meter) sensor is the real "safe" ways.

>Stock, the ZR-1 O2 sensors run about 900 mV at WOT.


My 170HP 3800 Series I V6 does the same... 900-910mV

>Agreed.  On V8 cars sold today, headers are probably the easiest and
>biggest bang for the effort and dollar spent, but then you are no
>longer street legal.


Why wouldn't you be street legal?
If you still have the bungs for the O2 sensors and if their is AIR injection
and the headers have the AIR injection ports, then they will still be street
legal.  The exhaust manifolds aren't considered part of the emissions
equipment unless the O2 sensor mounts in them or they have the AIR fittings.