Injector settings
Melting Slicks
Joined: Feb 2006
Posts: 2,163
Likes: 5
From: Houston
Absolutely. I'll go a step further and admit that my VE table is very choppy in places b/c that is what it took to get the AFR dead on. Log the AFR error and make that change to the VE table to dial it in.
Pro
Joined: Feb 2003
Posts: 745
Likes: 136
From: Detroit MI
Injector Short Pulse Adder is not something that you are going to easily solve for in the vehicle. This is data that needs to be derived offline directly from raw injector flow tests to get right. Basically, you have one equation and three unknowns in your case. With only one equation, how do you know if you have error in offset, flow rate, or short pulse adjustment down low? This gets complicated one step further if the rest of the engine isn't completely stock, as both the MAF and VE values would also need to be adjusted to match the new hardware and pumping efficiency. If you're using AFR error to edit VE, then any errors in injector data (short pulse, offset, flow rate) result in errors in VE and vice-versa.
Melting Slicks
Joined: Jul 2008
Posts: 3,002
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From: Houston Texas
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I have a stock LS1, meaning stock cam, heads, rockers, rotating assembly etc. It does have a twin turbo kit, LS6 intake, 1:1 regulator, and return style fuel system.
I am using hptuners with a 3 bar SD OS and ID1000 injectors. I have input the correct short pulse, offset, flow rate, etc., from Injector Dynamics.
Now let's only discuss idle and low speed part throttle conditions. From an airflow standpoint, it should be relatively close to stock, but I have adjusted the VE table based on the AFR error histogram and there isn't a stock value in my entire map now.
Greg, would you say this makes sense, or do I have errors somewhere else?
Is it correct to look at the VE table as a way to get your fueling dialed in instead of an airflow model? Basically I am treating the VE values as fuel required instead of theoretical airflow.
Melting Slicks
Joined: Apr 2005
Posts: 3,418
Likes: 1
From: Chicagoland Area IL
I posted this link yesterday but deleted it as I thought it would complicate things here… Not sure of data quality http://injector-rehab.com/shop/lag.html , you have 12 ohm injector. Offset is one of the variables contributing to your fueling error. NOTE results are in 3 bar, so scaling and interpolation will be required (no magic formula here that I know of, because injector construction comes into play - curve fitting/approximation is what I have done). Your offset vs voltage vs kPa will still be off, but less off.
I personally think this needs to be tackled, even if not perfect, because C5/6 can see large voltage fluctuations and also get a decent base offset… This can be frustrating first time around, so you decide.
Short pulse adder is last step IMO.
I personally think this needs to be tackled, even if not perfect, because C5/6 can see large voltage fluctuations and also get a decent base offset… This can be frustrating first time around, so you decide.
Short pulse adder is last step IMO.
Thread Starter
Racer
Joined: Jun 2012
Posts: 492
Likes: 1
I just got this back from RC:
"rated at 750cc ( 71.4 lbs/hr) at 43 psi. The maximum fuel pressure is up to 70 psi. The injector will continue to sustain operation beyond 70 psi, but you will not see an increase in flow. The injectors require a 1 amp signal and should be fine with the drivers used in the factory ECU.
Here are the injector latency values for the SH4-750:
10v 1.36ms
11 1.12
12 0.92
13 0.76
14 0.63
15 0.50"
I don't have my laptop with me, but where would latency values be entered at? Sorry if thats a dumb question with an obvious answer.
They match your linked chart as well.
"rated at 750cc ( 71.4 lbs/hr) at 43 psi. The maximum fuel pressure is up to 70 psi. The injector will continue to sustain operation beyond 70 psi, but you will not see an increase in flow. The injectors require a 1 amp signal and should be fine with the drivers used in the factory ECU.
Here are the injector latency values for the SH4-750:
10v 1.36ms
11 1.12
12 0.92
13 0.76
14 0.63
15 0.50"
I don't have my laptop with me, but where would latency values be entered at? Sorry if thats a dumb question with an obvious answer.
They match your linked chart as well.
Melting Slicks
Joined: Apr 2005
Posts: 3,418
Likes: 1
From: Chicagoland Area IL
ttz/OP, I don’t do this on a daily basis, so don’t have complete table names memorized… Think the table for your model year will likely be something like “Injector Offset vs Battery Voltage vs Vacuum kPa”. Offset is latency, or dead time, semantics I guess.
Google “Data Fit” as I think they still have 30 day free trial (select 3rd order polynomial for regression method), this will build curve fitting equation for you. NOTE with only 6 data points (10-15V) anything outside this range will be error prone. You need Microsoft Excel. This will help extrapolate offset vs voltage outside supplied data.
If you are comfortable to this point, shoot me a PM and I’ll help with the rest. Again will not be dead on, but better than where you are now.
Google “Data Fit” as I think they still have 30 day free trial (select 3rd order polynomial for regression method), this will build curve fitting equation for you. NOTE with only 6 data points (10-15V) anything outside this range will be error prone. You need Microsoft Excel. This will help extrapolate offset vs voltage outside supplied data.
If you are comfortable to this point, shoot me a PM and I’ll help with the rest. Again will not be dead on, but better than where you are now.
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We have in stock if necessary. RC's are out dated and do not include all the data necessary as I said earlier in this post.
Pro
Joined: Feb 2003
Posts: 745
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From: Detroit MI
I have a stock LS1, meaning stock cam, heads, rockers, rotating assembly etc. It does have a twin turbo kit, LS6 intake, 1:1 regulator, and return style fuel system.
...but I have adjusted the VE table based on the AFR error histogram and there isn't a stock value in my entire map now.
Greg, would you say this makes sense, or do I have errors somewhere else?
...but I have adjusted the VE table based on the AFR error histogram and there isn't a stock value in my entire map now.
Greg, would you say this makes sense, or do I have errors somewhere else?
Also, I see a lot of confusion between "offset" and "deadtime" or "latency". They are NOT the same. When properly used, injector offset includes both the opening delay and the closing delay, showing a net value to adjust the final pulsewidth. A lot of aftermarket injector warehouses miss this because they seem to have no clue about the engineering that goes into the product they are selling. Unfortunately, if they give you a big ol' pile of steaming crap for data and some fast talk about latency, most consumers don't know the difference. There is a short list of companies that are selling injectors and actually understand them and how they should be characterized in your corvette. Injector Dynamics happens to be one of those, and I trust the data coming from Paul Yaw because we've had lengthy discussions about how it's generated.
Melting Slicks
Joined: Apr 2005
Posts: 3,418
Likes: 1
From: Chicagoland Area IL
I do own one of your books and have watched some of your youtube promos in the past and that is where I equated offset = latency...
Did a quick search and http://www.youtube.com/watch?v=kBk0K...endscreen&NR=1 at about 4:15 appears to say same thing.
I have no dog in this fight, so I’m out.
Last edited by Skunkworks; Oct 10, 2012 at 12:49 PM.
Pro
Joined: Feb 2003
Posts: 745
Likes: 136
From: Detroit MI
As mentioned, for me this is a hobby but enjoy learning.
I do own one of your books and have watched some of your youtube promos in the past and that is where I equated offset = latency...
Did a quick search and http://www.youtube.com/watch?v=kBk0K...endscreen&NR=1 at about 4:15 appears to say same thing.
I do own one of your books and have watched some of your youtube promos in the past and that is where I equated offset = latency...
Did a quick search and http://www.youtube.com/watch?v=kBk0K...endscreen&NR=1 at about 4:15 appears to say same thing.
The gap you see is mostly deadtime or latency, but that's what it takes to get over to the physical mass vs time curve/line. Closing delay is hard to visualize in that graph, but it's there in the form of mass that is added at the end of the pulse. All we really care about is total milliseconds of activation time and total milligrams of fuel mass, so using a single value for "offset" does it very cleanly in this case.I'm glad people are actually paying attention and starting to ask more intelligent questions about this. It will force the injector suppliers to raise their game. As the consumers, you guys ultimately benefit.
Thread Starter
Racer
Joined: Jun 2012
Posts: 492
Likes: 1
I'm very close to getting the "offset vs. volts vs. vac" table all figured out (just need to find the appropriate excel sheet) thanks to Skunkworks helping me understand some things. You've all contributed in one way or another though as well. I'm starting to grasp this more and more. Still amazes me how complex it really is to change injectors properly.
Now I'm curious how one comes up with the "short pulse adder" and further more, why is that needed? I thought the "offest vs. volts vs. vac" table would take care off any offset/latency. No? Also wondering how one calculates the "short pulse limit" and "min injector pulse"?
Now I'm curious how one comes up with the "short pulse adder" and further more, why is that needed? I thought the "offest vs. volts vs. vac" table would take care off any offset/latency. No? Also wondering how one calculates the "short pulse limit" and "min injector pulse"?
Pro
Joined: Feb 2003
Posts: 745
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From: Detroit MI
The short pulse limit defines the area in which we apply the adder. It is usually just left to 4.0ms in GM calibrations, since we can always just add a zero if there is no change needed.
Min injector pulse is used to clip the bottom end to a value where we actually have repeatable control of delivered fuel mass during the commanded pulse width. There is a point where you just don't get consistent fuel delivery on the bottom end because you're not consistently opening the injector before you shut the field down. If it only opens part way, you have no clue how much fuel you've delivered (if any). Setting this to a reasonable minimum makes sure that if we fire the injector at all, we at least get something out of it.
Gee, how many other professional trainers or tooners do you see on here giving this info away for free? Do they even understand it themselves?
Melting Slicks
Joined: Apr 2005
Posts: 3,418
Likes: 1
From: Chicagoland Area IL
You'll notice in that example that I keep saying "offset" for a reason. The gap you see is mostly deadtime or latency, but that's what it takes to get over to the physical mass vs time curve/line. Closing delay is hard to visualize in that graph, but it's there in the form of mass that is added at the end of the pulse. All we really care about is total milliseconds of activation time and total milligrams of fuel mass, so using a single value for "offset" does it very cleanly in this case.
The gap you see is mostly deadtime or latency, but that's what it takes to get over to the physical mass vs time curve/line. Closing delay is hard to visualize in that graph, but it's there in the form of mass that is added at the end of the pulse. All we really care about is total milliseconds of activation time and total milligrams of fuel mass, so using a single value for "offset" does it very cleanly in this case.Quote - “The injector offset can be described as either the intercept of the high slope with zero fuel mass or as the point at which the injector really opens (where the low slope intercepts zero fuel mass). Similarly, GM also uses a short pulse adjustment to make up for the lack of a second injector slope at low masses. Both strategies get the same job done and allow the PCM to properly meter fuel at small pulses in the nonlinear flow region of the injector’s capacity.”
Not trying to be a jack azz, but there’s allot of contradiction here.
Again no dog in this fight, last post here.
Thread Starter
Racer
Joined: Jun 2012
Posts: 492
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I watched you video when it was posted. Deff informative even though it was a demo. I can only imagine what the full DVD has to offer. I'll prob look into purchasing it soon.
So how does one calculate what short pulse adder is needed and what the minimum injector pulse and default injector pulse are?
So how does one calculate what short pulse adder is needed and what the minimum injector pulse and default injector pulse are?
Platinum Supporting Vendor
Joined: Sep 2001
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I watched you video when it was posted. Deff informative even though it was a demo. I can only imagine what the full DVD has to offer. I'll prob look into purchasing it soon.
So how does one calculate what short pulse adder is needed and what the minimum injector pulse and default injector pulse are?
So how does one calculate what short pulse adder is needed and what the minimum injector pulse and default injector pulse are?
Justin