It sounds to me like he made you a custom "VAFC", which is not a "chip" as such, but rather a "piggy back" ECU. Since the Vortech "timing box" can modify the timing on an S2000 to a slight amount, this is believable. The Vortech box is also a sort of "piggy back". You should try to pull the code when the CEL comes on just so you know which system is being adversely affected. There may be a better connection to be made to do what is intended. Knowing the code may help to figure this out.
Leaning out the A/F on an S2000 is a known way to produce some gains (VAFC) and pulling timing (Vortech) is another way to run the engine safer, but not necessarily a better way to produce gains. Perhaps your add-on prevents timing from being pulled.
In any case, what you have described is perfectly believable. It was just the terminology that you originally used that was a bit confusing. No biggie.

 

[QUOTE=Wisconsin S2k,Apr 18 2005, 11:01 PM]I'd get it removed.

 

Xviper, I spoke with my Son again and he said that he came off the Intake Temperature Contol Sensor and used an empty fuse location for power. I reset the CEL and have not had a problem since. I love my Son, but sometimes he can drive me crazy. Just to let you guys know he had 5 tours of combat in Afganistan and Iraq. His plane was the 2nd or 3rd to land in Bagdad Airport when we took it over. His unit comes in just after Special Ops have done their job. I think it is wonderful what he and all the other young men and woman of the military are doing, but as a parent I am extremely worried when he is deployed.
Thanks,
JimmyB

 

I'm still unclear on what it is your son installed? When playing around with a $30k car, particularly one that has a twitchy ECU when it comes to things such as your son installed, I'd be concerned. As great as your son sounds, and as good intentioned as I'm sure he was, that's a scary variable to have on your car, particularly considering it caused a CEL.

 

I believe he installed a home made version of what is being discussed here:
https://www.s2ki.com/forums/index.php?showtopic=284455

There have also been other threads here about these little resisters being sold on ebay for a couple of bucks each. They're all the same principle. The only difference is in the "packaging" and hence why one is 2 bucks and another is 50 bucks. The idea is to fool the ECU into not seeing hot intake temps so it doesn't pull timing. This can result in a miniscule gain but not entirely safe for the car. The ECU needs to know the intake temps for a reason. The problem with such devices is that you don't know just how much you are fooling the ECU and it may not do what it needs to do when it needs to do it to keep the engine safe. In theory, this is an interesting idea and for some other cars, it may very well be of benefit. However, for an engine like ours where the ECU controls almost every aspect of the engine's functions, fooling it isn't always a good idea unless you can do dynos and diagnostics to confirm what's going on. Our engines are already running on the edge of a high state of tune. Unknowingly messing with it might not be such a good idea.

 

It's pretty much a resistor that fools the PCM into running richer because of a false Coolant temp reading.

I'd also remove the resistor. Depending how they wired it, the temp gauge will not function either.