My car does not like coasting. Help!
09-19-2005, 05:57 PM
#1
My car does not like coasting. Help! Starting to get to the end of things to try out.
Mods in signature.
When cruising at lower rpm, I get driveline shake when I let off the gas. Basically, between 900-1300 rpm, my car will not decel or coast smoothly. It will shake. It will pull from 700 rpm on up if it has 2% TPS or greater, but between 0-1% TPS is where I'm getting the shakes.
I've got my VE tables nailed (less than 2% ST Trims).
Idle spark and base spark both match at 34 degrees at this rpm and load range.
Makes no difference whether I'm in speed density or MAF mode.
MAF airflow, Dynamic Airflow and Idle Airflow all match.
Trimming back the throttle cracker seems to help, but it hasn't eliminated it. Haven't fooled with DFCO, but should I?
In a nutshell, my car has no driveline shake (kinda like it's on/off the throttle) as long as it has 2% TPS or greater, but at or near 0% TPS, it wants to shake. Any ideas on where else to look? FWIW, I'm an EFI Live newbie (V 7.3), but an HP Tuners (v 1.6) veteran.
Mods in signature.
When cruising at lower rpm, I get driveline shake when I let off the gas. Basically, between 900-1300 rpm, my car will not decel or coast smoothly. It will shake. It will pull from 700 rpm on up if it has 2% TPS or greater, but between 0-1% TPS is where I'm getting the shakes.
I've got my VE tables nailed (less than 2% ST Trims).
Idle spark and base spark both match at 34 degrees at this rpm and load range.
Makes no difference whether I'm in speed density or MAF mode.
MAF airflow, Dynamic Airflow and Idle Airflow all match.
Trimming back the throttle cracker seems to help, but it hasn't eliminated it. Haven't fooled with DFCO, but should I?
In a nutshell, my car has no driveline shake (kinda like it's on/off the throttle) as long as it has 2% TPS or greater, but at or near 0% TPS, it wants to shake. Any ideas on where else to look? FWIW, I'm an EFI Live newbie (V 7.3), but an HP Tuners (v 1.6) veteran.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
09-20-2005, 08:28 AM
#2
1. If you are tuning your VE table off of your STFTs with LT headers, that is going to pose a problem. With LTs, your narrow band O2 sensors just aren't accurate anymore, ESPECIALLY under low throttle conditions.
2. Are you running a MAF as well (e.g. no full-time SD mode)?
To give you an idea, when I tune my car in Open Loop SD, my A/F ratio (as shown by my wideband O2 sensor) is dead nuts on 14.63 across the board. I re-enable closed loop, and my A/F ratio jumps right to 15.3:1 cruising, 15.8:1 at idle. This is because my O2s are a little sleepy with my Kooks headers.
2. Are you running a MAF as well (e.g. no full-time SD mode)?
To give you an idea, when I tune my car in Open Loop SD, my A/F ratio (as shown by my wideband O2 sensor) is dead nuts on 14.63 across the board. I re-enable closed loop, and my A/F ratio jumps right to 15.3:1 cruising, 15.8:1 at idle. This is because my O2s are a little sleepy with my Kooks headers.
09-20-2005, 11:24 AM
#5
Push clutch in, problem solved..... lol
You have the stick shift bucking at low RPM's, all sticks do that at times, hell even my completely stock 2002 S-10 Extended cab 4cyl 5 speed does that some times at 1,100 RPMs.
If I read it right, it's the nature of the beast and since you have a good size cam, it will be worse.
You have the stick shift bucking at low RPM's, all sticks do that at times, hell even my completely stock 2002 S-10 Extended cab 4cyl 5 speed does that some times at 1,100 RPMs.
If I read it right, it's the nature of the beast and since you have a good size cam, it will be worse.
09-20-2005, 11:40 AM
#6
Originally Posted by MeentSS02
Oh, and take a log under those conditions, and see how the logged numbers compare to your DFCO entry/exit conditions (normal, not clutch transition).
09-20-2005, 11:48 AM
#7
Originally Posted by MeentSS02
1. If you are tuning your VE table off of your STFTs with LT headers, that is going to pose a problem. With LTs, your narrow band O2 sensors just aren't accurate anymore, ESPECIALLY under low throttle conditions.
2. Are you running a MAF as well (e.g. no full-time SD mode)?
To give you an idea, when I tune my car in Open Loop SD, my A/F ratio (as shown by my wideband O2 sensor) is dead nuts on 14.63 across the board. I re-enable closed loop, and my A/F ratio jumps right to 15.3:1 cruising, 15.8:1 at idle. This is because my O2s are a little sleepy with my Kooks headers.
2. Are you running a MAF as well (e.g. no full-time SD mode)?
To give you an idea, when I tune my car in Open Loop SD, my A/F ratio (as shown by my wideband O2 sensor) is dead nuts on 14.63 across the board. I re-enable closed loop, and my A/F ratio jumps right to 15.3:1 cruising, 15.8:1 at idle. This is because my O2s are a little sleepy with my Kooks headers.
The biggest problem I have is driving through school zones. My car will not stay smooth at a constant 20 mph. It bucks and shakes even though my ST Trims are less than 5% + or - and my timing at 0% TPS and 4% TPS is still around 34 degrees. Basically, the VEs seem very close and the timing seems to be pretty consistent. I know some people say it's something I have to live with, but I've seen others tune T-Rex cars to run super smooth at these lower rpm. I just need to know the areas where I need to continue to fine tune.
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09-20-2005, 12:13 PM
#8
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Did you tune/adjust your idle tables? The desired vs actuals and such that were discussed on here quite a bit a few months ago may be a good source of information...especially if you drilled or adjusted your throttle body.
09-20-2005, 12:50 PM
#9
Originally Posted by SSpdDmon
Did you tune/adjust your idle tables? The desired vs actuals and such that were discussed on here quite a bit a few months ago may be a good source of information...especially if you drilled or adjusted your throttle body.
09-20-2005, 06:56 PM
#12
Originally Posted by SSpdDmon
What about your throttle cracker and throttle follower tables?
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
09-20-2005, 11:51 PM
#13
FormerVendor
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wow i have a 2000 s-10 same bucking !!! I would hate to see it if I modded it !! thats funny seriosly its not the " NORMAL' driving condition anyway, arent we all Mario Andretti!!
Originally Posted by Billiumss
Push clutch in, problem solved..... lol
You have the stick shift bucking at low RPM's, all sticks do that at times, hell even my completely stock 2002 S-10 Extended cab 4cyl 5 speed does that some times at 1,100 RPMs.
If I read it right, it's the nature of the beast and since you have a good size cam, it will be worse.
You have the stick shift bucking at low RPM's, all sticks do that at times, hell even my completely stock 2002 S-10 Extended cab 4cyl 5 speed does that some times at 1,100 RPMs.
If I read it right, it's the nature of the beast and since you have a good size cam, it will be worse.
