1990 Throttle hesistation

[XfireZ51]

Can't tell much of anything w/o the datalog. It seems to be running rich is about all I could make out, then goes lean a bit. You cranked in a awful lot of throttle change.

[Schrade]

I only screwed in the bolt to 2.7% TO.

That's where it smooths back out. Perfect from 0 - 1.6%, shaky from 1.6 - 2.4, then flat again. (which Marc said ALL stockers do)

Gotta' be room for improvement...

[Schrade]

... and I keep thinkin' here Dom ...

You say that as engine comes OFF of idle, control of one of the parameters is passed from 'X', to 'Y'.

Let's say for a moment here, that that is NOT how it works.

Let' say that as rev's increase, EVERY parameter increases linearly (or exponentially) - and that no 'handoffs' occur.

If that were the case, then it would be easy to see a glitch in any one parameter's increase, that allows the rough spot from 1.6%TO, to 2.4%TO (that Marc says is normal).

Stay with me here now...

But since one parameter is interrupted by a handoff, what is the 'buffer', that ensures that the ball doesn't get dropped? Because it DOES get dropped, when the dependency changes.

Is there no dedicated overlapping / buffer parameter? Besides all of the others, of course, that have their own job to do???

If 10 guys are totin' a girder, and 1 guy gets someone to take his place, he's gonna' have to bribe at least 1 of the 9 to do double duty while the swap takes place.

ECM needs coding to make one parameter to compensate - like double fuel, for a moment, to simplify the example here.

[scottfab]

Originally Posted by XfireZ51

Can't tell much of anything w/o the datalog. It seems to be running rich is about all I could make out, then goes lean a bit. You cranked in a awful lot of throttle change.

Exactly right. It'd be hard enough diagnosing a stock set-up without that data but a modified one? Oh boy.

[XfireZ51]

Based on what Marc has said, there's nothing to see here, move along.

[Schrade]

Originally Posted by XfireZ51

Based on what Marc has said, there's nothing to see here, move along.

I 'moved along' road test, and it spun up smooth as silk. 28.3 MPG's steady @ 59 on the flat (remember I have the 4L60e). Once I get a 3.07 in the back, with headers + Jeff's [Shrek's] pipes, that should bring it up close to 30+. I had my '94 LT1 just under 33 @ 65 with the turtle gear 2.73, after top end re-work.

Still not happy with the glitch at 1.6 - 2.4%TO, which is noticeable when it shifts light throttle.

Restrictor gasket is still in place as well...............................

Where's Franke here - how do I check 02's for proper reading?

[Franke]

Originally Posted by Schrade

I 'moved along' road test, and it spun up smooth as silk. 28.3 MPG's steady @ 59 on the flat (remember I have the 4L60e). Once I get a 3.07 in the back, with headers + Jeff's [Shrek's] pipes, that should bring it up close to 30+. I had my '94 LT1 just under 33 @ 65 with the turtle gear 2.73, after top end re-work.

Still not happy with the glitch at 1.6 - 2.4%TO, which is noticeable when it shifts light throttle.

Restrictor gasket is still in place as well...............................

Where's Franke here - how do I check 02's for proper reading?

Schrade,
O2 volts-
is the measured voltage (in Millivolts, mV) generated by the O2 (Oxygen) sensor. Will typically range from 100 mV (lean) to 900 mV(rich). For SFI systems, this is divided into left and right side values in Datamaster.
Forget what I said that about your O2's as I went back and looked at the vid again. They are varying as they should be. What I was looking at is the Right side LT count staying at 115 (rich) even thought the ST counts were going lean 130-134 as you increased throttle.

There are guys on this forum much smarter than I am in this arena and maybe they can jump in here but I am curious as to why your LT count on the right side shows to be rich fairly constantly when the left side seems to be about right (126-130) counts. Since this vid is at idle in CL, I think the LT/ST should be about 128 or so to maintain correct AFR.

I am comparing your DM readings to mine. When I had a bad injector on my left bank my INT/BLM histogram showed the LT fuel trim to be constantly rich at 115. After I replaced my fuel injectors both of my LT and ST readings are right around 126 to 130 counts at idle and respond equally when I goose it. Yours doesn't seem to do that in that video.

[XfireZ51]

Just as an FYI, It's not unusual to have a 20 point discrepancy for BLMs between
Left and right banks. You may want to read a bit of my thread on Injector Offset.
Idle presents itself as having the widest gap. Cruise reduces the diff between the 2 banks. Having the correct offsets in the cal also makes a difference here.

[Franke]

Originally Posted by XfireZ51

Just as an FYI, It's not unusual to have a 20 point discrepancy for BLMs between
Left and right banks. You may want to read a bit of my thread on Injector Offset.
Idle presents itself as having the widest gap. Cruise reduces the diff between the 2 banks. Having the correct offsets in the cal also makes a difference here.

Xfire, I did read all of that when you and another gentleman were discussing the offset for the injectors. You know a lot more about it than I do and I was really intrigued to see the depth you guys went to. I have to say I had exactly the same LT condition that Schrade has in DM and when I replaced that bad injector it was gone. I watched as the BLM and fuel cell changes were better and so I figured that the bad injector was causing the ECM indigestion. Am I wrong on this?

[XfireZ51]

Originally Posted by Franke

Xfire, I did read all of that when you and another gentleman were discussing the offset for the injectors. You know a lot more about it than I do and I was really intrigued to see the depth you guys went to. I have to say I had exactly the same LT condition that Schrade has in DM and when I replaced that bad injector it was gone. I watched as the BLM and fuel cell changes were better and so I figured that the bad injector was causing the ECM indigestion. Am I wrong on this?

Franke,

All I advocate for is gathering information to make a good diagnosis. I couldn't tell much from viewing Schrade's vid so that's what I said. The disparity in BLMs between L/R banks isn't unusual. The area that Schrade is focusing on, just off idle, is a transition point especially since he has gone to eliminating the secondaries. There's quite a bit in the calibration that could be causing the off idle hesitation. Marc has stated that what Chuck is describing appears to be standard behavior for the LT-5. Is it possible that it's a bad injector? Imagine it is, but how has that been indicated so far? Without getting my hands on it, I can only say I need more data.