Any cure for surging/jerking effect when cruising at low RPMs/steady speed?
10-24-2003, 06:39 AM
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Any cure for surging/jerking effect when cruising at low RPMs/steady speed? Hi everybody - I'm hoping that somebody can point me in the right direction to solve a nagging tuning issue.
I recently installed a TR224/224 112 cam and PP S2 5.3L heads and have resolved most of my tuning issues, with the exception of a surging/jerking effect when cruising at a steady speed at low RPMs (approx 1500-2000). The effect would be similar to something you'd get if cruising at a steady speed and quickly pushing up and down slightly on the throttle...
Current Edit settings:
- Throttle body butterfly was drilled an additional 1/16"
- Main VE table scaled 80% from 400-1200 RPMs
- Idle set to 800 RPMs
- IFR scaled 90%
- IAC Park Position and Idle Air Tables * 120%
- Added a few degrees of timing to both the Base Spark in Drive/Park tables
- Installed mods are in my sig
The engine starts fine both when hot and cold, with little-to-no startup surging and idles great.
I'm hoping somebody could point me in the right direction...
TIA!
Scott
I recently installed a TR224/224 112 cam and PP S2 5.3L heads and have resolved most of my tuning issues, with the exception of a surging/jerking effect when cruising at a steady speed at low RPMs (approx 1500-2000). The effect would be similar to something you'd get if cruising at a steady speed and quickly pushing up and down slightly on the throttle...
Current Edit settings:
- Throttle body butterfly was drilled an additional 1/16"
- Main VE table scaled 80% from 400-1200 RPMs
- Idle set to 800 RPMs
- IFR scaled 90%
- IAC Park Position and Idle Air Tables * 120%
- Added a few degrees of timing to both the Base Spark in Drive/Park tables
- Installed mods are in my sig
The engine starts fine both when hot and cold, with little-to-no startup surging and idles great.
I'm hoping somebody could point me in the right direction...
TIA!
Scott
10-24-2003, 01:17 PM
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Surging is often related to a lean mixture, are your low
RPM cruise LTFTs showing any issue?
Basically a little fuel more or less doesn't affect a fat
mix as much as a lean one, if you look at the power vs
mixture curves. A starving dog will take your hand along
with the hamburger.
RPM cruise LTFTs showing any issue?
Basically a little fuel more or less doesn't affect a fat
mix as much as a lean one, if you look at the power vs
mixture curves. A starving dog will take your hand along
with the hamburger.
01-28-2004, 02:07 PM
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I've been having the same problem after replacing a bad O2 sensor. Anyone else have any suggestions.
BTW, my engine is internally stock with Jet Hot LTs.
Car accelerates fine and idles fine, but cruising at the same speed is horrible and eventually, the car goes into limp mode.
I hope someone can offer me some help on this one.
thanks, Brit
BTW, my engine is internally stock with Jet Hot LTs.
Car accelerates fine and idles fine, but cruising at the same speed is horrible and eventually, the car goes into limp mode.
I hope someone can offer me some help on this one.
thanks, Brit
01-31-2004, 01:38 PM
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Play around with the tune.. I was able to COMPLETELY eliminate all cam surge in my car by adding some fuel down low.. I can cruise @ 1200 RPM in 6th gear (roughly 40 MPH with 4.11 gear) without any surge whatsoever.. Just add a few percent to the main VE table around the RPMs in question and go from there. You can play with timing as well.
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02-01-2004, 10:14 PM
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We just fixed that same problem on a C5 with the TR224. It is often the case that a cam with more dwell will add too much fuel down low. We increased the RAF values by .10 across the table, to get more air in. We did not use a % since that would increase the lower temperature values too much.
On my car I used the stock Z06 IAC and RAF tables for kicks and it runs perfectly. I was surprised, but if you look at the files the big difference is in the Z06 RAF table having larger values.
On my car I used the stock Z06 IAC and RAF tables for kicks and it runs perfectly. I was surprised, but if you look at the files the big difference is in the Z06 RAF table having larger values.
02-02-2004, 12:22 PM
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my problem ended up being the O2s, I ended up replacing both of them with the Bosch 13444 and I haven't any problems since I replaced them and reset my computer. Just an update for some of you guys who are curious.
I suppose I'm going to be one of the Guinea pigs around here, 101K miles on an 01 Z28.
I suppose I'm going to be one of the Guinea pigs around here, 101K miles on an 01 Z28.
02-06-2004, 08:10 PM
#17
Alot of surging can be fixed by adjusting the timing as well.
Usually an adjustment to the High Octane table or the VE table at that specific point will eliminate the surging.
Both fixes you have to log data to ensure that you make a correction at the proper point.
Usually an adjustment to the High Octane table or the VE table at that specific point will eliminate the surging.
Both fixes you have to log data to ensure that you make a correction at the proper point.
