LTFT's won't come down....not making sense
08-08-2003, 04:50 PM
#1
TECH Junkie
Thread Starter
iTrader: (71)
Join Date: Mar 2002
Location: East Brady, Pa
Posts: 3,703
Likes: 0
Received 0 Likes
on
0 Posts
LTFT's won't come down....not making sense Here's what I have. 36lb SVO injectors on a 422 stroker. I've changed my injector scale from 3.18 clear up to 5.52(for the first cell) The lowest I can get my LTFT's is 13 while at part throttle. If I give it alot of throttle they max out at 25. Now when I adjusted them down to 3.18 the car would barely start and threw lean codes which doesn't make sense because I thought it would be running pig rich that low. On the 5.52 scale I couldn't get off of +25 but at least the car runs. The only time I got readings lower then 25 was on a scale starting with 4.42. Do I have an exhaust or intake leak possibly. I've went all around my sheetmetal intake with a propane torch but didn't find anything. I had my header collectors welded and the very insides aren't sealed 100% but they're slipped over. Thanks for any help. I don't know what to do. Nothing is making sense.
08-08-2003, 05:15 PM
#2
Re: LTFT's won't come down....not making sense Are you on the Injector Flow Table or the Injector Offset Table.
Check your injectors. It sounds like you may be getting poor fuel atomization. Are they aligned properly?? Any problems when you were putting them in.
Try slapping the stockers back in there a running the car up to rule out anything mechanically wrong.
Check your injectors. It sounds like you may be getting poor fuel atomization. Are they aligned properly?? Any problems when you were putting them in.
Try slapping the stockers back in there a running the car up to rule out anything mechanically wrong.
08-08-2003, 06:00 PM
#3
TECH Junkie
Thread Starter
iTrader: (71)
Join Date: Mar 2002
Location: East Brady, Pa
Posts: 3,703
Likes: 0
Received 0 Likes
on
0 Posts
Re: LTFT's won't come down....not making sense I am using the injector flow rate table. The injectors seemed to go in pretty simple. I'll double check the alignment to be sure. I no longer have my stockers. Thanks for the reply.
08-08-2003, 06:42 PM
#4
TECH Resident
Join Date: Jan 2002
Location: USA
Posts: 754
Likes: 0
Received 0 Likes
on
0 Posts
Re: LTFT's won't come down....not making sense If the bottom O rings of injectors are leaking you would not see any fuel but you would have vaccum leaks.
Also as you mentioned exhaust leaks could be the issue but your O2s values should give you a clue on that.
Other then that what stands out is those mucked up MAF and TB, they can cause hugh positive LTFTs values on decel cells while STFTs stay close to zero ( if tuned correctly)
Being your tuning the PCM calibration space you clearly do not need those mucked up parts to get correct AFR so I would go back to stock ones they can support a lot of HP as is and assures the adaptive stratagy progam in PCM is matched to G.M's MAF table.
Also as you mentioned exhaust leaks could be the issue but your O2s values should give you a clue on that.
Other then that what stands out is those mucked up MAF and TB, they can cause hugh positive LTFTs values on decel cells while STFTs stay close to zero ( if tuned correctly)
Being your tuning the PCM calibration space you clearly do not need those mucked up parts to get correct AFR so I would go back to stock ones they can support a lot of HP as is and assures the adaptive stratagy progam in PCM is matched to G.M's MAF table.
08-08-2003, 10:20 PM
#5
TECH Junkie
Thread Starter
iTrader: (71)
Join Date: Mar 2002
Location: East Brady, Pa
Posts: 3,703
Likes: 0
Received 0 Likes
on
0 Posts
Re: LTFT's won't come down....not making sense My sig needs updated. I'm running a stock MAF...not even desceened and a shaner TB. Once I get things straightened out I plan to try the other parts and go from there. Should I monitor my O2's or STFT's for more information?
08-09-2003, 12:02 AM
#6
Re: LTFT's won't come down....not making sense The ONLY time that I ever saw this problem was on one of the race cars that we tuned. I'll describe the problem that we had, and maybe you can relate to it. I'm a little suspicious, because you have a sheetmetal intake.
We ran a NOS nozzle kit on the car. The kit consists of 8 specialty rings that fit on the end of the injectors to inject nitrous into the same port as the injector. With the stock injectors the car ran fine. We switched to 42 lb injectors. All of the sudden the car ran like total crap and was not tunable. We had the exact same symptoms that you were having. It took us about 2 weeks (believe me I worked on that damn thing nightly) to figure out what was going on.
The 42lb injectors that we had purchased had a different spray pattern. The spray pattern was very wide and conicle (like an obtuse triangle). As a result the fuel spray was impinging on the NOS nozzle kit fittings on the end of the injectors.
To fix this problem we had to switch to a pintle type injector (FYI all SVO injectors are pintle type). The SVO spray pattern is more like a lazer (much like the stock) rather than a wide conicle spray like the 42lb's. We ran many tests with the injector system benched outside the car. With the narrower spray pattern the fuel would not impinge at all and the car ran fine. With the 42's the fuel would hit the side of the NOS fittings and was dripping into the chamber.
The dripping fuel does not mix with the air. As a result, the more fuel we added, the more the fuel would drip, the less it would mix with the air, and our LTerms would actually peg at 25% and the car would barely run. The only way I could get the car to run was to implement an obscenely high IFR table value (very very lean). The car would run, but there would be absolutely NO throttle response.
Just for ***** and giggles, you may want to try swapping the sheetmetal intake off and putting the stocker back on. If the sheetmetal intake does not have adequate space for the fuel to disperse and mix with the air before it goes into the chamber, then this could very well be your problem.
Just a suggestion.
Good Luck
We ran a NOS nozzle kit on the car. The kit consists of 8 specialty rings that fit on the end of the injectors to inject nitrous into the same port as the injector. With the stock injectors the car ran fine. We switched to 42 lb injectors. All of the sudden the car ran like total crap and was not tunable. We had the exact same symptoms that you were having. It took us about 2 weeks (believe me I worked on that damn thing nightly) to figure out what was going on.
The 42lb injectors that we had purchased had a different spray pattern. The spray pattern was very wide and conicle (like an obtuse triangle). As a result the fuel spray was impinging on the NOS nozzle kit fittings on the end of the injectors.
To fix this problem we had to switch to a pintle type injector (FYI all SVO injectors are pintle type). The SVO spray pattern is more like a lazer (much like the stock) rather than a wide conicle spray like the 42lb's. We ran many tests with the injector system benched outside the car. With the narrower spray pattern the fuel would not impinge at all and the car ran fine. With the 42's the fuel would hit the side of the NOS fittings and was dripping into the chamber.
The dripping fuel does not mix with the air. As a result, the more fuel we added, the more the fuel would drip, the less it would mix with the air, and our LTerms would actually peg at 25% and the car would barely run. The only way I could get the car to run was to implement an obscenely high IFR table value (very very lean). The car would run, but there would be absolutely NO throttle response.
Just for ***** and giggles, you may want to try swapping the sheetmetal intake off and putting the stocker back on. If the sheetmetal intake does not have adequate space for the fuel to disperse and mix with the air before it goes into the chamber, then this could very well be your problem.
Just a suggestion.
Good Luck
08-09-2003, 11:12 AM
#7
TECH Resident
Join Date: Jan 2002
Location: USA
Posts: 754
Likes: 0
Received 0 Likes
on
0 Posts
Re: LTFT's won't come down....not making sense I did miss in your sig that you also have a metal intake.
With the cars that I have tuned that had metal ones the vaccum has changed and causing PCM to run at different fuel trims such as when at normal idle with A/C off, instead of being in cell 19 it would be in cell 17 (AC idle) and the tune from idle to mid range had to be tuned totally differently due to the intake which at times because of the trim cell shift would be in fuel learn when it should not be and or the reverse.
With the cars that I have tuned that had metal ones the vaccum has changed and causing PCM to run at different fuel trims such as when at normal idle with A/C off, instead of being in cell 19 it would be in cell 17 (AC idle) and the tune from idle to mid range had to be tuned totally differently due to the intake which at times because of the trim cell shift would be in fuel learn when it should not be and or the reverse.
Trending Topics
08-09-2003, 01:41 PM
#8
TECH Junkie
Thread Starter
iTrader: (71)
Join Date: Mar 2002
Location: East Brady, Pa
Posts: 3,703
Likes: 0
Received 0 Likes
on
0 Posts
Re: LTFT's won't come down....not making sense Sounds like the intake may have something to do with that. I'm actually in the process of trading my intake for an LS6 with direct port so I'll just wait a couple days for it to get here and see what happens. Thanks for all the input. You guys never sease to amaze me.
