RomRaider

welcome to the world of "guys with utecs that log unclamped MAP sensor voltage from their oem ecus."

it's a pretty exclusive club.

Wonder if I should put that one my resume, followed by "You probably wouldn't understand."

You'll run into the same issues with logging for sure. I ran my car with my Utec logging software logging boost from the Utec, ignoring the modified ECU map signal. I just wanted to ensure that since I was tuning mostly from my ECU, that the ECU was getting proper data for the wastegate integral tables etc. Just as a note, my car ran pretty well with the unmodified Utec. So, meh

If your max WGDC is pretty close, then it won't be a big deal of course. The ECU will just keep trying to add WGDC in order to get the boost up until it is maxed out. However, if your max WGDC is well above what it needs to be to hit your boost target, then I think you would get some pretty bad overboosting going on. I didn't try it that way though.

I tee'd off the map sensor to the ECU this morning. Logs perfect now!

The switch *is* useful. Remember, the UTEC was available before you could flash the ECU yourself.


The FCD switch has two positions, "enable" and "disable". The terminology is misleading.

When the FCD switch is set to "enable", the UTEC "moves" the factory fuel cut from ~17psi to ~20psi. It does this by capping the MAP signal to the ECU at ~12psi, unless you *actually* run >20psi.

When the FCD switch is set to "disable", the UTEC *always* caps the MAP signal to ECU at ~12psi. If you plan on running >20psi, you need to set the switch this way.

Along with the hardware FCD, the UTEC added software-based limits when Open Loop Fueling was released.

I did this trick and it log better but stop logging after 18psi( on both UTEC and ECU) when my boost gauge was reading 25psi. I am going to try to put a diode on the "t" and see how it works

Does the UTEC map clamp affect the load the ecu sees?

Do not clamp or bridge. Just switch the FC off on the UTEC. I already lost a piston because it does not read proper psi when bridged(18psi max when real 27psi) and it keep raising the wg values.

^^ above two posts:

Read x99percent's post dated Fri Jun 08, 2007 9:59 am.

I saw that post. So that means since load is proportional to MAP and other variables then it would be affected. Hmmm, so if I am going to retune my map after 11-12 psi if I ever do the MAP wire modification you guys are talking about because my engine loads will be higher...?

In the stock MAF-based ECU, load is NOT calculated by looking at manifold pressure.

Engine load is
(mass airflow g/s / RPM) * 60

HOWEVER, the problem is the ECU no longer sees your actual boost. You cannot use the stock ECU to control boost because it will never see more than ~12.5 psi. So the PID controller will always think you are undershooting boost when your target is more than 12.5 psi.

oh, thats weird. I think I remember having a problem like this. I switched the FCD to the opposite position I think to fix it. I use the stock ecu to control my boost up to 24 psi with no more than 1 psi overshoot on a GM BCS. The UTEC only controls fueling and timing at WOT.

Yep he's right. I logged my manifold pressure with the map sensor out of the car by applying air pressure(with air compressor) and with the utec fc swith up the ecu could not read more than 12.5-14. With fc swith down read all the way to 27psi and with the ecu/utec cable bridge no more than 18.7(appliying 28psi). This test readings were the same on the utec(it could not read more than 18psi so the wg values ramp up to 99 if boost desired was more than 19psi) and the ecu when bridge. So do not bridge if your going to tune ecu or utec for more than 18psi, and if you do and break i got 3 sti pistons in good shape.