Injector Duty Cycle
10-09-2006, 11:52 AM
#1
TECH Fanatic
Thread Starter
iTrader: (5)
Join Date: Oct 2004
Location: DFW
Posts: 1,173
Likes: 0
Received 0 Likes
on
0 Posts
Injector Duty Cycle I went out and did a log (HPT) on my bolt on, cam car, and it keeps showing that my injector duty cycle is like 120%. So of course, my first thought is that I need bigger injectors. But is there anything in the tune that would cause it to show that big? I have the 26# injectors, and I know too many people with more hp than me who don't have duty cycles like this... so I don't want to go out and buy bigger injectors if that's not my problem.
10-09-2006, 12:40 PM
#5
TECH Senior Member
iTrader: (23)
Join Date: Aug 2005
Location: Watertown, NY
Posts: 8,797
Likes: 0
Received 0 Likes
on
0 Posts
I have you at needing at least 32lb injectors. That is assuming 470 Crank Hp, which if you use 15% drive loss is 400RWHP. I also put in .5 BSFC and not to exceed 80% injector duty cycle. You should just get some 42lb injectors, they are cheap and work well.
http://www.rceng.com/technical.htm
http://www.rceng.com/technical.htm
10-09-2006, 12:59 PM
#6
TECH Fanatic
Thread Starter
iTrader: (5)
Join Date: Oct 2004
Location: DFW
Posts: 1,173
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by brad8266
I have you at needing at least 32lb injectors. That is assuming 470 Crank Hp, which if you use 15% drive loss is 400RWHP. I also put in .5 BSFC and not to exceed 80% injector duty cycle. You should just get some 42lb injectors, they are cheap and work well.
http://www.rceng.com/technical.htm
http://www.rceng.com/technical.htm
10-09-2006, 03:34 PM
#7
Originally Posted by monicaz28
Yeah, I really thought I needed some bigger injectors, but our other car, which has the 90/90 (vs. my Ls6) and a TRex cam does not even come close to maxxing out the 28# injectors, with more power. I can't understand why that car wouldn't need bigger injectors as well.
Trending Topics
10-09-2006, 04:38 PM
#8
TECH Fanatic
Thread Starter
iTrader: (5)
Join Date: Oct 2004
Location: DFW
Posts: 1,173
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by greatwhitess
Sounds like the tune is off on the T-Rex vehicle if it is running fine on 28#ers. The 28 are barely good enough for mild bolt-on cars let alone a big cam.
10-09-2006, 05:18 PM
#10
T-REX Vehicle---The injectors only put out as much fuel as commanded in the VE tables(hp tuners) so if your timing and fuel are still set to stock like values then your duty cyle would be fine still. Once you start adding the fuel and spark needed to make more power then your duty cycle will go up. YOur AF can be spot on but you can still not be even close to the correct fueling and timing needed to get the most out of the combo.
The vehicle with 120% duty cycle is probably closer to where it needs to be with fueling.
Have you hooked a wideband up and checked your AF error?
What AF are you commanding at WOT?
What is the timing at WOT?
The vehicle with 120% duty cycle is probably closer to where it needs to be with fueling.
Have you hooked a wideband up and checked your AF error?
What AF are you commanding at WOT?
What is the timing at WOT?
10-09-2006, 05:38 PM
#11
TECH Senior Member
iTrader: (23)
Join Date: Aug 2005
Location: Watertown, NY
Posts: 8,797
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by greatwhitess
T-REX Vehicle---The injectors only put out as much fuel as commanded in the VE tables(hp tuners) so if your timing and fuel are still set to stock like values then your duty cyle would be fine still. Once you start adding the fuel and spark needed to make more power then your duty cycle will go up. YOur AF can be spot on but you can still not be even close to the correct fueling and timing needed to get the most out of the combo.
The vehicle with 120% duty cycle is probably closer to where it needs to be with fueling.
Have you hooked a wideband up and checked your AF error?
What AF are you commanding at WOT?
What is the timing at WOT?
The vehicle with 120% duty cycle is probably closer to where it needs to be with fueling.
Have you hooked a wideband up and checked your AF error?
What AF are you commanding at WOT?
What is the timing at WOT?
Your ideas are valid in a PCM with LTFT's disabled because then the PCM will only fuel for what is in the tables, no learning allowed.
10-10-2006, 10:20 AM
#12
Originally Posted by brad8266
Im gonna disagree with you about your thoughts on the TRex car. Even if the stock fuel tables are there the LTFT's will go way up to compensate for the added airflow. The PCM will not only inject fuel as per the VE table, especially if the car is using the MAF. It will go by MAF table values plus the positive LTFT's. This will cause duty cycles to go up.
Your ideas are valid in a PCM with LTFT's disabled because then the PCM will only fuel for what is in the tables, no learning allowed.
Your ideas are valid in a PCM with LTFT's disabled because then the PCM will only fuel for what is in the tables, no learning allowed.
Good Call. I have run SD so long I forgot I keep mine turned off.
Have you ever checked your AF with a wideband? I am curious to what is going on there?
BTW What is your duty cycle on the T-Rex car?
Are they hanging at a certain percentage and won't go any higher?
The car with the MS4 sounds normal. I would be cioncerned with the other one
10-10-2006, 10:32 AM
#13
TECH Fanatic
Thread Starter
iTrader: (5)
Join Date: Oct 2004
Location: DFW
Posts: 1,173
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by greatwhitess
Good Call. I have run SD so long I forgot I keep mine turned off.
Have you ever checked your AF with a wideband? I am curious to what is going on there?
BTW What is your duty cycle on the T-Rex car?
Are they hanging at a certain percentage and won't go any higher?
The car with the MS4 sounds normal. I would be cioncerned with the other one
Have you ever checked your AF with a wideband? I am curious to what is going on there?
BTW What is your duty cycle on the T-Rex car?
Are they hanging at a certain percentage and won't go any higher?
The car with the MS4 sounds normal. I would be cioncerned with the other one
10-10-2006, 11:06 AM
#15
12 Second Club
iTrader: (10)
Join Date: Sep 2005
Location: From Ohio now in that state up north
Posts: 948
Received 0 Likes
on
0 Posts
Yeah 60-70% is way low i see more than that on bolton cars with a 13.0 afr. I would think though that you are rich and your buddy is lean 120% duty cycle sounds like your commanding to much fuel i would get new injectors and then tune it with a wideband. Also what rpm are the cars being spun to?
Last edited by 98redorangeta; 10-10-2006 at 11:16 AM.
10-10-2006, 01:28 PM
#16
TECH Fanatic
Thread Starter
iTrader: (5)
Join Date: Oct 2004
Location: DFW
Posts: 1,173
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by 98redorangeta
Yeah 60-70% is way low i see more than that on bolton cars with a 13.0 afr. I would think though that you are rich and your buddy is lean 120% duty cycle sounds like your commanding to much fuel i would get new injectors and then tune it with a wideband. Also what rpm are the cars being spun to?
10-10-2006, 01:32 PM
#17
TECH Senior Member
iTrader: (23)
Join Date: Aug 2005
Location: Watertown, NY
Posts: 8,797
Likes: 0
Received 0 Likes
on
0 Posts
IMO if you are above 100% no matter what the tune is you need some new injectors. Your tune can not be that far off to make your car run that rich. If it was that rich it would probably barley run and spit black smoke out the tailpipe.
10-10-2006, 02:01 PM
#18
you really have to understand how does the IDC get values, cause 120% really makes no sense--you cannot make your injectors work harder than they're supposed to, they have their physical limitations.
IDC gets calculated as a ratio of two times: one is the time needed to inject the fuel, and the other being the maximum time in which you can do the injection. so the ridiculous IDC's happen when the time you need is extra long, or time you have to do it in is extra short. either way, aim it so you dont go over 80-85%
if you want to see what influences the duty cycles, read this, and use the calculator i created:
http://redhardsupra.blogspot.com/200...se-widths.html
IDC gets calculated as a ratio of two times: one is the time needed to inject the fuel, and the other being the maximum time in which you can do the injection. so the ridiculous IDC's happen when the time you need is extra long, or time you have to do it in is extra short. either way, aim it so you dont go over 80-85%
if you want to see what influences the duty cycles, read this, and use the calculator i created:
http://redhardsupra.blogspot.com/200...se-widths.html
10-10-2006, 02:20 PM
#19
TECH Fanatic
Thread Starter
iTrader: (5)
Join Date: Oct 2004
Location: DFW
Posts: 1,173
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by RedHardSupra
you really have to understand how does the IDC get values, cause 120% really makes no sense--you cannot make your injectors work harder than they're supposed to, they have their physical limitations.
IDC gets calculated as a ratio of two times: one is the time needed to inject the fuel, and the other being the maximum time in which you can do the injection. so the ridiculous IDC's happen when the time you need is extra long, or time you have to do it in is extra short. either way, aim it so you dont go over 80-85%
if you want to see what influences the duty cycles, read this, and use the calculator i created:
http://redhardsupra.blogspot.com/200...se-widths.html
IDC gets calculated as a ratio of two times: one is the time needed to inject the fuel, and the other being the maximum time in which you can do the injection. so the ridiculous IDC's happen when the time you need is extra long, or time you have to do it in is extra short. either way, aim it so you dont go over 80-85%
if you want to see what influences the duty cycles, read this, and use the calculator i created:
http://redhardsupra.blogspot.com/200...se-widths.html
