Rx7Ridah

iTrader: (8)

i am currently running a teamfc3s.org fcd and i am curious if racing beat's and hks's both lock the voltage the same, as in as soon as you turn the key on the computer thinks you have boost. i think that may be contributing to my overly rich idle. any ideas?

Turbonut

iTrader: (1)

When at idle, the gauge should register vacuum, not boost. Not sure where your FCD is placed as the RB is at the boost sensor, and some at the ecu, but I would suggest unplug the fcd and give it a try. That will tell you if it's the fcd.

Rx7Ridah

iTrader: (8)

i know that the gauge should register vacuum at idle when it has the stock setup, but i have a fcd. all that the fcd is, is a voltage clamp that clamps the signal going to the computer from the boost sensor so that the ecm doesnt see boost about 8.6 psi. now the question that i have is that with the fcd that i am currently running, which is a teamfc3s.org one that i built myself, it clamps the voltage signal as soon as you start the car, meaning that the boost gauge reads full boost, hence i assume that the ecm also reads full boost at idle, which would mean that the computer is increasing the injector pulse and/or turning on the secondarys to compensate for boost pressure that isnt actually there. i am curious if that also occurs with other fcd's such as hks or racing beat?

HAILERS

I don't know what your talking about. I built a series four homemade fuel cut defender and you set the clamping voltage around 3.65 vdc. The RacingBeat ones can be altered also. They have a pot also and you can scrape the goop off the screw head and adjust it where you want within reason. I found the RacingBeat one set at around 3.15 vdc which I found not to my liking and jacked the voltage up to the 3.60 range. I have both the RB and the homemade one. Two different cars. 90 bucks verses ...what? Five to seven bucks?

This is the one I was talking about. The one your talking about does not sound like this one http://www.teamfc3s.org/info/articles/fcd/diy_fcd.htm

And boost pressure can be read from vacuum to the place the clamp voltage has been set. So the gauge should be reading up to about 8psi at least (factory gauge). If you built the above FCD and the boost gauge does not read up to approx 8psi, then it's broken (the FCD).

Rx7Ridah

iTrader: (8)

well thats the fcd that i built with the assistance of my father (who is a licensed electrician) and as soon as you turn the key on the boost gauge just goes to full boost and stays there. which is what the clamp should do it is locking the voltage at max boost so the computer doesnt see more. my question is that when doing to the ecm always thinks that there is boost b/c that is what the boost sensor is sending(hence the fcd output signal). i just wanted to know if there is a fcd that doesnt lock the voltage until it sees that voltage so that the ecm would run standard maps until boost really arrives and then lock it at max.

HAILERS

*******well thats the fcd that i built with the assistance of my father (who is a licensed electrician) and as soon as you turn the key on the boost gauge just goes to full boost and stays there***********

Nope. It should not do that at all.

For setting the clamping voltage, I took a MITTYVAC and put it on my boost sensor. Then applied boost to the sensor with the MITTYVAC while watching the output of the sensor to the ECU. Turned the pot on the DIY til it showed a max output of 3.65volts.

With a digital meter backprobed into the ECU input from the boost sensor, I can watch the voltage rise as I boost til the max I ever see is the 3.65vdc.......but the boost keeps rising on my aftermarket boost gauge. The factory gauge starts out at a vacuum and tops out on the top of the gauge at full boost.

In other words, no, the gauge should not spike just because you turned the key to On or just started the engine.

Maybe the pot needs to be adjusted to something higher???? Yes.

Rx7Ridah

iTrader: (8)

ill give that a try. thanks.