Has anyone bypassed their heater core in an effort to either:

1) decrease warmup time (and maybe increase mpg)

or

2) increase effectiveness of air conditioning?

How did you do it? Was it worth it?

On a CarTalk forum someone said that they did it to increase A/C effectiveness:

By using thermocouples and an IR thermometer I had found that at 75F with the A/C off the incoming air will eventually climb to 116F. So the evaporator has to deal with this heat leak plus the outside air temperature. When the outside temperature climbs above 85F the A/C becomes worthless in CA. By installing a bypass valve for the heater core from an older Camry ($75 for a $5 valve) the heat leak is stopped and the A/C is quite acceptable except on the hottest of days in the sun.

noo i enjoy my heater in my car!!for gods sake its a scion not a race car.

he never said he was making race car he was making his cooling more efficient

I have never heard of doing that to make the a/c more efficient. Any well designed heating/cooling system will have the ability to isolate the heater core from the incoming air completely. Hell my '62 Comet can do it. So if the air out of the vents is getting up to 116deg when set to full cool that guy had something wrong with his car (sticking cable, bad seal, etc.)
The fact his A/C won't work above 85deg is further proof of something being wrong with his car. My A/C has worked on days well up over 100deg and humid. Even when it has struggled to keep the car cool the air out of the vents was cold enough to give me a headache, it was just that the heat was leeching into the car faster than the A/C could displace it.

So in conclusion, it sounds like someone had something wrong with his car, and rather than fix it right he found a cheap hack of a way to avoid the real problem.

i posted that because i allways hear everyone saying take it out for this reason that reason,bypass the throttle body so it stays colder etc..as stated its pretty much a new car why would you even want to try it?good luck with water all over your floor board