Can't keep 408 running
05-05-2007, 12:03 PM
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Can't keep 408 running
Maybe this should be in the tuning section, but not sure.
I fired up the 408 today and can't keep it running. I am using a 6.0 tune right now with the cylinder volume changed to reflect the new motor and the VE scaled up 3% like it was recommended to thunder550 when he did his 408. My cam is a 244/248 .612/.615 on a 112lsa
I drilled another small hole in the throttle body to get a bit more idle airflow and it didn't seem to help.
I fired up the 408 today and can't keep it running. I am using a 6.0 tune right now with the cylinder volume changed to reflect the new motor and the VE scaled up 3% like it was recommended to thunder550 when he did his 408. My cam is a 244/248 .612/.615 on a 112lsa
I drilled another small hole in the throttle body to get a bit more idle airflow and it didn't seem to help.
05-05-2007, 12:26 PM
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Use a scan tool to check the IAC counts. You want to see abot 30-40 counts when idling in park. You can use the tiny adjusting screw to adjust the throttle blade. Opening the blade will lower the IAC counts so for example if your IACs are over 100 turn the screw in to open the blade. If however your IAC counts are near or at zero then close the blade. I hate drilling holes unless there's no other choice.
What are the fuel trims at?
Richard
What are the fuel trims at?
Richard
05-05-2007, 01:10 PM
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the only way i can keep it running is to keep my foot on the gas and keep it at at least 2k so its kinda hard to see anything on the scanner.
05-05-2007, 01:19 PM
#4
If you have tuning software, post up your tune so some of the smart guys can look through it.
Will it start without giving it gas?
If it will, how long will it idle before it dies?
Maybe quick vid and a log would help us see the problem.
Will it start without giving it gas?
If it will, how long will it idle before it dies?
Maybe quick vid and a log would help us see the problem.
05-05-2007, 03:04 PM
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This sounds like a tuning issue.
You should probably *lower* the VE values in the idle cells. It's probably so rich it won't run.
I would say 60-80Kpa and the first 3 rows should be sufficent.
You should probably *lower* the VE values in the idle cells. It's probably so rich it won't run.
I would say 60-80Kpa and the first 3 rows should be sufficent.
05-05-2007, 04:21 PM
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Adam,
You did the right thing to change the cylinder volume. However, I'm wondering if you re-scaled your injector flow rate (IFR) for your 44 PPH injectors. If not, you're running way rich. Do you have a wide band AFR meter? I think that it's going to be pretty hard to set up your mixture without the ability to monitor and log the AFR via a wide band.
Your 2000 has a return type fuel system, so you will set the IFR to 44 PPH across the board (assuming your fuel pump pressure is still regulated at 4 bar (about 58 PSI). My LQ4 came with about 25.4 PPH injectors. When I changed them out to 30 PPH injectors, I had to change the IFR in EFI Live/FlashScan (see below).
Steve
You did the right thing to change the cylinder volume. However, I'm wondering if you re-scaled your injector flow rate (IFR) for your 44 PPH injectors. If not, you're running way rich. Do you have a wide band AFR meter? I think that it's going to be pretty hard to set up your mixture without the ability to monitor and log the AFR via a wide band.
Your 2000 has a return type fuel system, so you will set the IFR to 44 PPH across the board (assuming your fuel pump pressure is still regulated at 4 bar (about 58 PSI). My LQ4 came with about 25.4 PPH injectors. When I changed them out to 30 PPH injectors, I had to change the IFR in EFI Live/FlashScan (see below).
Steve
05-05-2007, 05:21 PM
#7
Originally Posted by Steve Bryant
Adam,
You did the right thing to change the cylinder volume. However, I'm wondering if you re-scaled your injector flow rate (IFR) for your 44 PPH injectors. If not, you're running way rich. Do you have a wide band AFR meter? I think that it's going to be pretty hard to set up your mixture without the ability to monitor and log the AFR via a wide band.
Your 2000 has a return type fuel system, so you will set the IFR to 44 PPH across the board (assuming your fuel pump pressure is still regulated at 4 bar (about 58 PSI). My LQ4 came with about 25.4 PPH injectors. When I changed them out to 30 PPH injectors, I had to change the IFR in EFI Live/FlashScan (see below).
You did the right thing to change the cylinder volume. However, I'm wondering if you re-scaled your injector flow rate (IFR) for your 44 PPH injectors. If not, you're running way rich. Do you have a wide band AFR meter? I think that it's going to be pretty hard to set up your mixture without the ability to monitor and log the AFR via a wide band.
Your 2000 has a return type fuel system, so you will set the IFR to 44 PPH across the board (assuming your fuel pump pressure is still regulated at 4 bar (about 58 PSI). My LQ4 came with about 25.4 PPH injectors. When I changed them out to 30 PPH injectors, I had to change the IFR in EFI Live/FlashScan (see below).
I ask this because it's the sole reason why I haven't installed my set yet.
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05-05-2007, 07:14 PM
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Mark,
I did quite a lot of research on this about three years ago and determined that the 8.1 L truck injectors (Delphi Multec II Mini Series) P/N: 17124531 or 17113714 are set up for 3.8 g/S or 30 PPH. I can't remember all the places that I looked to run this down, but that is what I have written down. When I switched out the injectors in my LQ4 from the stock (as I remember about 25 or 24.4 PPH/ 3.205 g/S flow rate to the 30 PPH/3.8 g/S rating, the truck immediately ran like a champ.
I also did a quick Google search and found good corroborating information here http://www.silveradoss.com/forums/in...showtopic=4241. You need to put the IFR rating for the injectors at 4 bar (58 PSI) regardless of the engine size. The displacement per cylinder and the IFR are factored together (along with some other things like air density and commanded AFR) to yield a duty cycle that is appropriate for your setup. The cylinder volume (displacement per cylinder) parameter is what allows the injector to work for a given engine. The IFR for any injector is dependent upon the input pressure regulator and it is set up for 58 PSI at WOT for the Gen III engines.
I hope that this helps!
Steve
I did quite a lot of research on this about three years ago and determined that the 8.1 L truck injectors (Delphi Multec II Mini Series) P/N: 17124531 or 17113714 are set up for 3.8 g/S or 30 PPH. I can't remember all the places that I looked to run this down, but that is what I have written down. When I switched out the injectors in my LQ4 from the stock (as I remember about 25 or 24.4 PPH/ 3.205 g/S flow rate to the 30 PPH/3.8 g/S rating, the truck immediately ran like a champ.
I also did a quick Google search and found good corroborating information here http://www.silveradoss.com/forums/in...showtopic=4241. You need to put the IFR rating for the injectors at 4 bar (58 PSI) regardless of the engine size. The displacement per cylinder and the IFR are factored together (along with some other things like air density and commanded AFR) to yield a duty cycle that is appropriate for your setup. The cylinder volume (displacement per cylinder) parameter is what allows the injector to work for a given engine. The IFR for any injector is dependent upon the input pressure regulator and it is set up for 58 PSI at WOT for the Gen III engines.
I hope that this helps!
Steve
05-05-2007, 08:10 PM
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thats the same cam i have, i have a good base tune in mine. i swapped over to SD and it idles right off the bat. when i had the maf on there it was rich as hell and just garbage, made soem changes and then ditched the maf and its a whole different ballgame as for idle, start up and non foulingof plugs
oncei get runnign fully ill do the rest but the first part of tune is good for now.
your setup isnt that far off from mine if i recall. i could help out some
oncei get runnign fully ill do the rest but the first part of tune is good for now.
your setup isnt that far off from mine if i recall. i could help out some
05-05-2007, 09:58 PM
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Here is the tune i have in it right now. I changed the idle to 1100rpm just to try to keep it running but it didn't help. I am going to have it dyno tuned once it and the clutch is broken in but i need to get it good enough to drive till then. Im very new to tuning and don't have much of a clue to tell you the truth lol.