Tuning/Idle Issues
11-09-2015, 08:58 AM
#1
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Tuning/Idle Issues
Recently had my Z06 in for worked 243 heads, Fast 102 Intake and TB and Tune. Car has BTR cam, underdrive pulley, 42# injectors. Car made solid numbers for HP (465) and TQ (455) on a Dynoject but I have 3 concerns:
1. After you drive the car at normal speeds, it idles at 2000 RPM's for awhile (45 seconds or longer) before it will try to find an idle speed of 950 or 1000 RPM. On occasions, it will idle up and down from 1500 to 1900 RPM for no reason. Is the 102 intake allowing more air into engine and now needs more fuel?
2. Car seems sluggish or soft below 3200 RPM and before the recent the last set of mods, before the mods the car was much more throttle responsive.
3. AFR was 13.44, which seems lean from what I have read, where should the AFR be on the H/C/I car?
Any ideas or suggestions on where to start?
Thanks
1. After you drive the car at normal speeds, it idles at 2000 RPM's for awhile (45 seconds or longer) before it will try to find an idle speed of 950 or 1000 RPM. On occasions, it will idle up and down from 1500 to 1900 RPM for no reason. Is the 102 intake allowing more air into engine and now needs more fuel?
2. Car seems sluggish or soft below 3200 RPM and before the recent the last set of mods, before the mods the car was much more throttle responsive.
3. AFR was 13.44, which seems lean from what I have read, where should the AFR be on the H/C/I car?
Any ideas or suggestions on where to start?
Thanks
11-10-2015, 07:59 AM
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Recently had my Z06 in for worked 243 heads, Fast 102 Intake and TB and Tune. Car has BTR cam, underdrive pulley, 42# injectors. Car made solid numbers for HP (465) and TQ (455) on a Dynoject but I have 3 concerns:
1. After you drive the car at normal speeds, it idles at 2000 RPM's for awhile (45 seconds or longer) before it will try to find an idle speed of 950 or 1000 RPM. On occasions, it will idle up and down from 1500 to 1900 RPM for no reason. Is the 102 intake allowing more air into engine and now needs more fuel?
2. Car seems sluggish or soft below 3200 RPM and before the recent the last set of mods, before the mods the car was much more throttle responsive.
3. AFR was 13.44, which seems lean from what I have read, where should the AFR be on the H/C/I car?
Any ideas or suggestions on where to start?
Thanks
1. After you drive the car at normal speeds, it idles at 2000 RPM's for awhile (45 seconds or longer) before it will try to find an idle speed of 950 or 1000 RPM. On occasions, it will idle up and down from 1500 to 1900 RPM for no reason. Is the 102 intake allowing more air into engine and now needs more fuel?
2. Car seems sluggish or soft below 3200 RPM and before the recent the last set of mods, before the mods the car was much more throttle responsive.
3. AFR was 13.44, which seems lean from what I have read, where should the AFR be on the H/C/I car?
Any ideas or suggestions on where to start?
Thanks
The new intake and TB definitely need tuning especially if the TB is larger. There is an ETC scalar which is used to convert mm2 to TP% opening. Stock is .0255 and a 90mm is .0192. For a 102 it is around .0120 iirc. When this is changed, the minimum idle aie (Idle desired air) and several other idle control tables will need to be canged as well as the throttle Cracker and Follower. Also make sure the intake was installed with the correct valley plate button bolts. If not, then when being torqued down, it will crack and generate a vacumn leak. That being said the FAST 102 having a 3 piece design, does have a tendency to leak at times so check it out with a smoker. You can google smoking an engine and find a driveway trick with a soda bottle and a cigarette.
The lack of low end response could be associated with a vacuum leak as well or the tuner didn't tweak the VE which is the alternate air table to the MAF used to "fill in" when non-steady stae conditions occur like acceleration.
Lastly, 13.44 AFR at WOT is definitely too lean. Should be in the 12.5 to 12.8 area for my liking.
Ed M
Last edited by mowton; 11-10-2015 at 08:08 AM.
11-10-2015, 09:01 AM
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Having trouble ramping down to idle is a good indication you may have too much air, either by the tune or a vacumn leak. Per you question, I am assuming the cam and other mods had already been installed and tune and were ok.
The new intake and TB definitely need tuning especially if the TB is larger. There is an ETC scalar which is used to convert mm2 to TP% opening. Stock is .0255 and a 90mm is .0192. For a 102 it is around .0120 iirc. When this is changed, the minimum idle aie (Idle desired air) and several other idle control tables will need to be canged as well as the throttle Cracker and Follower. Also make sure the intake was installed with the correct valley plate button bolts. If not, then when being torqued down, it will crack and generate a vacumn leak. That being said the FAST 102 having a 3 piece design, does have a tendency to leak at times so check it out with a smoker. You can google smoking an engine and find a driveway trick with a soda bottle and a cigarette.
The lack of low end response could be associated with a vacuum leak as well or the tuner didn't tweak the VE which is the alternate air table to the MAF used to "fill in" when non-steady stae conditions occur like acceleration.
Lastly, 13.44 AFR at WOT is definitely too lean. Should be in the 12.5 to 12.8 area for my liking.
Ed M
The new intake and TB definitely need tuning especially if the TB is larger. There is an ETC scalar which is used to convert mm2 to TP% opening. Stock is .0255 and a 90mm is .0192. For a 102 it is around .0120 iirc. When this is changed, the minimum idle aie (Idle desired air) and several other idle control tables will need to be canged as well as the throttle Cracker and Follower. Also make sure the intake was installed with the correct valley plate button bolts. If not, then when being torqued down, it will crack and generate a vacumn leak. That being said the FAST 102 having a 3 piece design, does have a tendency to leak at times so check it out with a smoker. You can google smoking an engine and find a driveway trick with a soda bottle and a cigarette.
The lack of low end response could be associated with a vacuum leak as well or the tuner didn't tweak the VE which is the alternate air table to the MAF used to "fill in" when non-steady stae conditions occur like acceleration.
Lastly, 13.44 AFR at WOT is definitely too lean. Should be in the 12.5 to 12.8 area for my liking.
Ed M
The car pulls hard on big end, but i agree is seems like a vacuum leak or as you say it has so much more air flow with intake and heads it is trying to find a good idle speed. It will finally come down and idle at 1000 RPM after a 45-60 period of idling at 2000 so not sure if vacuum leak or other is causing this as it finds idle later, much later.
I think it is a combo of Fast & TB and tune needs tweaking ( I hope). I am not a tuner and have to rely on the experts to tune.
I will take your comments and see if I can find a crack or leak around intake. Thanks again
11-13-2015, 10:34 PM
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St. Jude Donor '13-'14-'15
So many mods all at once makes it difficult to narrow down exactly where the issue lies--
1st of all you must be sure your tuner inputted the correct IFR table for your 42 lb injectors---and remember that most injectors are rated at 3 bar where a C5 is rated at 4 bar-this can make a huge mismatch
2nd all your other mods can create tuning issues just one at a time -but all at once it makes it difficult to diagnose
If all tolled you have ended up with a high idle or a high idle surge regardless which mod caused it you seem to have too much idle air in gear which causes an idle hanging-- To correct this you need to remove a % of desired idle in gear--I would start with 10-15%
THEN with a cam you should have raised the "base idle timing" at leas by 3-4* this will prevent idle hunting or surge---
And finally the 13.44 AFR---Is that AFR during P/T or at WOT ?
At P/T throttle this would be a RICH condition as the AFR should be 14.68
But if the 13.44 is at WOT then the AFR is extremely LEAN where a safe WOT AFR should be between 12.50 and 12.90---
Chances are your VE table is way off if tour tuner did not do any VE tuning--If you checked the WOT fuel with a wideband and it is in fact a real 13.44 Then most likely your injectors flow rate needs an adjustment as well as your VE table---
As a start to make the WOT fuel richer ---I would add 20% to your VE table from 2000 RPM on up---then again check the AFR if still lean I would LOWER the IFR only at WOT by 10% and check it again-A lower IFR rate makes the fueling richer--
1st of all you must be sure your tuner inputted the correct IFR table for your 42 lb injectors---and remember that most injectors are rated at 3 bar where a C5 is rated at 4 bar-this can make a huge mismatch
2nd all your other mods can create tuning issues just one at a time -but all at once it makes it difficult to diagnose
If all tolled you have ended up with a high idle or a high idle surge regardless which mod caused it you seem to have too much idle air in gear which causes an idle hanging-- To correct this you need to remove a % of desired idle in gear--I would start with 10-15%
THEN with a cam you should have raised the "base idle timing" at leas by 3-4* this will prevent idle hunting or surge---
And finally the 13.44 AFR---Is that AFR during P/T or at WOT ?
At P/T throttle this would be a RICH condition as the AFR should be 14.68
But if the 13.44 is at WOT then the AFR is extremely LEAN where a safe WOT AFR should be between 12.50 and 12.90---
Chances are your VE table is way off if tour tuner did not do any VE tuning--If you checked the WOT fuel with a wideband and it is in fact a real 13.44 Then most likely your injectors flow rate needs an adjustment as well as your VE table---
As a start to make the WOT fuel richer ---I would add 20% to your VE table from 2000 RPM on up---then again check the AFR if still lean I would LOWER the IFR only at WOT by 10% and check it again-A lower IFR rate makes the fueling richer--
11-14-2015, 05:16 AM
#5
Safety Car
I agree with Ed.
Too bad you didn't use the GM 90 TB. It's plenty large enough at that power level. And easier to tune.
Is this a speed density tune? Or is there a MAF?
Either way, there are a few " *****" a tuner can use to set WOT AFR.....but if the AFR doesn't follow the value commanded by the power enrichment table, the other ***** aren't adjusted properly.
At any rate, 13.4 is lean. Something is off in the calibration.
FWIW, it's not uncommon to see leaner numbers on the road than were seen on the dyno.
Ron
Too bad you didn't use the GM 90 TB. It's plenty large enough at that power level. And easier to tune.
Is this a speed density tune? Or is there a MAF?
Either way, there are a few " *****" a tuner can use to set WOT AFR.....but if the AFR doesn't follow the value commanded by the power enrichment table, the other ***** aren't adjusted properly.
At any rate, 13.4 is lean. Something is off in the calibration.
FWIW, it's not uncommon to see leaner numbers on the road than were seen on the dyno.
Ron
11-15-2015, 11:00 AM
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So many mods all at once makes it difficult to narrow down exactly where the issue lies--
1st of all you must be sure your tuner inputted the correct IFR table for your 42 lb injectors---and remember that most injectors are rated at 3 bar where a C5 is rated at 4 bar-this can make a huge mismatch
2nd all your other mods can create tuning issues just one at a time -but all at once it makes it difficult to diagnose
If all tolled you have ended up with a high idle or a high idle surge regardless which mod caused it you seem to have too much idle air in gear which causes an idle hanging-- To correct this you need to remove a % of desired idle in gear--I would start with 10-15%
THEN with a cam you should have raised the "base idle timing" at leas by 3-4* this will prevent idle hunting or surge---
And finally the 13.44 AFR---Is that AFR during P/T or at WOT ?
At P/T throttle this would be a RICH condition as the AFR should be 14.68
But if the 13.44 is at WOT then the AFR is extremely LEAN where a safe WOT AFR should be between 12.50 and 12.90---
Chances are your VE table is way off if tour tuner did not do any VE tuning--If you checked the WOT fuel with a wideband and it is in fact a real 13.44 Then most likely your injectors flow rate needs an adjustment as well as your VE table---
As a start to make the WOT fuel richer ---I would add 20% to your VE table from 2000 RPM on up---then again check the AFR if still lean I would LOWER the IFR only at WOT by 10% and check it again-A lower IFR rate makes the fueling richer--
1st of all you must be sure your tuner inputted the correct IFR table for your 42 lb injectors---and remember that most injectors are rated at 3 bar where a C5 is rated at 4 bar-this can make a huge mismatch
2nd all your other mods can create tuning issues just one at a time -but all at once it makes it difficult to diagnose
If all tolled you have ended up with a high idle or a high idle surge regardless which mod caused it you seem to have too much idle air in gear which causes an idle hanging-- To correct this you need to remove a % of desired idle in gear--I would start with 10-15%
THEN with a cam you should have raised the "base idle timing" at leas by 3-4* this will prevent idle hunting or surge---
And finally the 13.44 AFR---Is that AFR during P/T or at WOT ?
At P/T throttle this would be a RICH condition as the AFR should be 14.68
But if the 13.44 is at WOT then the AFR is extremely LEAN where a safe WOT AFR should be between 12.50 and 12.90---
Chances are your VE table is way off if tour tuner did not do any VE tuning--If you checked the WOT fuel with a wideband and it is in fact a real 13.44 Then most likely your injectors flow rate needs an adjustment as well as your VE table---
As a start to make the WOT fuel richer ---I would add 20% to your VE table from 2000 RPM on up---then again check the AFR if still lean I would LOWER the IFR only at WOT by 10% and check it again-A lower IFR rate makes the fueling richer--
Car was tuned with MAF not speed density.
It was recommended by tuner to use Fast 102 and TB after heads were installed.
I will be using another tuner here in Houston this week to see if they can tune the car and it get it straightened out and run properly. I hope the new tuner can tune with the Fast 102 &TB installed as it is an expensive bolt on.
Once car warms up the idling or lack there of becomes worse or higher, up to 2000 RPM.
Once it is warmed up i hear a whine from engine when driving low speeds or idling. I don't hear the whine when it is cold but after car warms up it is noticeable. It almost feels like there is a vacuum leak but haven't been able to track it down yet. car seems to run pretty well in upper RPM's but haven't pushed it as I don't trust tune or AFR readings. Thanks again for your comments, I will pass them along to tuner to see if this helps.
Mike
