[Nonecure]

I'm running the Fuel-it TBI and I am seeing high AFR's after lifting off the throttle. I can understand this if I was under boost and fuel was flowing, but this happens when just driving down the street. The Hobbs switch is set to 15 psi, so I should not be seeing any flow. I think I need to rig up something to check the pressure to activate the switch.

Any ideas?

http://www.datazap.me/u/nonecure/tbi...3&zoom=179-489

[Velocity26]

Please tell me that the Hobbs switch is mounted in the intake manifold , and not in the charge pipe.

[Nonecure]

Installed in a meth bung on my VSRF charge pipe. Just like in the Fuel-it instructions.

Is this wrong?

https://www.dropbox.com/s/c1sk9doa1t...stall.pdf?dl=0

[Nonecure]

The install, I will clean up the wires later.

[Velocity26]

When you initially close the throttle, the intake manifold goes to vacuum, but the pressure outside of the throttle body spikes up. At that point, the BOV should open and release the excess pressure. I have no idea how much pressure your BOV holds, but it may be enough to keep your Hobbs switch open for a brief time, while the pressure releases, and make your mixture very rich for that period of time.

How long after you close the throttle does your AFR stay rich? Just a second or two? Maybe you can wire a small test light into the Solenoid circuit (orr the Hobbs circuit) so that it lights up when the solenoid is energized and give you an idea if the problem is electrical or if the solenoid is sticking and hanging open. There are a few things that can cause a similar problem.

[Nonecure]

Yes, I probably need a test light. It looks like it stays a few seconds at 234.95 afr before dropping, which tells me that fuel must be flowing. The switch does say 15psi on the side, but it appears to be triggering much lower. I gave it a 1/2 turn clockwise and it did not seem to make a difference.

Between the first 2 AFR spikes I have a max of 0.8 psi. The longer spike was after hitting 4.4 psi. During all of this testing, I was trying to be soft on the pedal to keep boost down. I would expect this when boosting at the setpoint (~15 psi), but not what I am seeing.

[terryd5150]

This is just a question based on observation, I may be WAY off base as I have zero experience with Steve's TBI kit.

I understand why the meth bung appears after the BOV on that charge pipe; when running meth, it's not ideal to have meth venting to atmosphere.

However, if this exact same set-up were installed on a charge pipe where the bungs appear before the BOV, would the same components at these same settings still sense this "delay"?

Again, simply a question based on observation - zero data to confirm or refute.

For current state, have you tried different Hobbs set points or one step lighter BOV spring?