Is this not going open loop?
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Race Director
Joined: May 2001
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Is this not going open loop?
I was just looking over my website and came across the dyno graph for my friend's 95 Z-28. It has over 100k miles on it and runs perfectly. The motor doesn't look healthy as the previous owner did it no favors using dino oil and not changing that frequently. In any case it dyno's fine, the torque seems to fall off faster than most I've seen, I think possibly because of worn out valve springs.
What gets me is the A/F ratio. LT1's I've seen will go rich at WOT. This one doesn't even begin to move towards rich until 4500 RPMs. Does this thing have a lazy TPS so it's not going into open loop? Weak fuel pump, clogged fuel filter? There's probably little more power to be had in there.
What gets me is the A/F ratio. LT1's I've seen will go rich at WOT. This one doesn't even begin to move towards rich until 4500 RPMs. Does this thing have a lazy TPS so it's not going into open loop? Weak fuel pump, clogged fuel filter? There's probably little more power to be had in there.
Team Owner
Joined: Dec 2000
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From: SE NY
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Re: Is this not going open loop? (Nathan Plemons)
That is strange.
When you hammer the accelerator the TPS goes to full value immediately so shouldn't be the problem.
As RPM climbs pulse width is increased requiring more fuel so not likely a fuel filter or pump issue.
If he puts a scan tool on an OBD-I he can see when it goes open loop. The BLM cell number will go to #15 and it's value will go to 128 as will the Integrator value.
He can also monitor the O2 sensor readings; though not accurate at WOT they will give some indication as to the trend of A/F. For example, with my ram-air setup, my O2 readings go to about 940mV at WOT and drop to 920mV by the 1/4mi traps indicating a slight leaning due to increased relative air flow.
When you hammer the accelerator the TPS goes to full value immediately so shouldn't be the problem.
As RPM climbs pulse width is increased requiring more fuel so not likely a fuel filter or pump issue.
If he puts a scan tool on an OBD-I he can see when it goes open loop. The BLM cell number will go to #15 and it's value will go to 128 as will the Integrator value.
He can also monitor the O2 sensor readings; though not accurate at WOT they will give some indication as to the trend of A/F. For example, with my ram-air setup, my O2 readings go to about 940mV at WOT and drop to 920mV by the 1/4mi traps indicating a slight leaning due to increased relative air flow.
Thread Starter
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Re: Is this not going open loop? (65Z01)
I've driven the car many times and it feels fine for a stocker. We've managed to coax a 13.9 out of it and it has a sorry excuse for a clutch. Maybe the A/F on the dyno was just acting up?
