Is there a way to determine if you need bigger injectors without being able to log IDC? Logging afr and finding out you are running too lean in the upper rpms isn't a very good option. There is no PID for IDC for 2013-2014 GT500s.
Is there a way to determine if you need bigger injectors without being able to log IDC? Logging afr and finding out you are running too lean in the upper rpms isn't a very good option. There is no PID for IDC for 2013-2014 GT500s.
I had the same Problem. VCM-Scanner can't logg duty-cycles of injectors(not only for Fords, Dodge Ram is similar). I solved this Problem by calculating the time the injector needs to spray the amount mass of fuel at the rev-limit. It's a little work with all Parameters (Flow rate low/high, Breakpoint, Offset time, injection begins with the breakpoint time at Flow Rate High, after this time it sprays with Flow Rate Low plus the Offset time at the beginning of the cycle with no flow). E.g. at 6400 rpm the 4 stroke cycle is 18.75 ms (1/(6400rpm/2/60). The fuel is sprayed only on a closed valve, therefore the fuel must be sprayed in a maximum of 3/4 of this time (14.0625 ms). If the Injectors can deliver this amount mass of fuel at this time, then they are big enough. The amount of fuel for one HP for (N/A) is approximately 0.55*1lb at high revs (0.65-0.7 lb for forced air GT500). If your engine should have 400 HP it needs 0.55 lb/h * 400HP=165 lb/h. Devided by number of Zylinders (8) and (6400 rpm/2)*60 you know the amount of fuel that is to be injected per injector per cycle. 165LB/h/8 = 20.625 lb/h, 20.625 lb/h/ (6400/2)*60 = 1.07421875*10^-4 lb per injection. (I know your engine has more Power, calculate yourself please)
This is the reason, why Diesel engines don't rev like gas engines. The time to inject the amount of Diesel is so short and the injectors are to slow (even with high pressure common rail) to spray the needed amount of Diesel in time before self-ignition.
Hope this helps.
My 2013 GT500 dynode 707 hp. I have the factory injectors.
I'll have to study your calculations and see what I can come up with. Thanks!
If you send me your calibration-file or the datas of Fuel/General Injector Control Flow Rate and Fuel System/General/Fuel Pump for the pressure at the fuel rail, I will calculate. I need also the rpm the engine makes at HP-Peak 707.
E.g. 707 HP/6000 RPM, 0.65 lb/HP/h needs 0,000319132 lb fuel per injector per cycle (4-stroke). The injector time is added from Offset-time (ca. 1 ms), Breakpoint-time (ca. 0.73 ms) and time of Flow Rate High. A 2011 5.4 Shelby would need 24.565 ms to inject a mass of 0.000319132 lb per cycle/injector at 707 HP/6000 rpm. The cycle-time at 6000 rpm is 20 ms total. This shows, that a duty-time of 100 % would not be enough for 707 HP at reference fuel pressure!
An exact calculation for your engine is only possible with the datas from your calibration-file.
Thanks! Here's my file. 707 occurs at 6500 rpm.Originally Posted by RVMustang
At 6500 rpm cycle time is 18,46154 ms. The injector needs 15,5045 MS for 0,000294583 lb-fuel/cycle at 0.65 lb/HP/h. The duty time is 84%. Perfect for this application.
So my factory 2013 GT500 injectors are adequate for 707 hp! That's great and I really appreciate your info and calculations!
Bit of a leap. So we cannot spay fuel while the intake valve is open for what reason?
You can spray on an open valve, you can spray all time, but the fuel mixture (carbutation) will be bad. A part of the fuel will not vaporate, the mix with air will be inhomogen, because a part of the fuel will be sprayed direct in the combustion chamber and cylinder without proper mixing fuel with air. Some zones would be richer and other leaner and the combustion would be inefficient or knocking. Another issue is, that fuel can be sprayed at the backside of the valve and deviate to the spark plug zone. The spark plug can foul and ignition efficient would be bad. The Pro on spraying on hot, closed valves is the good vaporation of the fuel.
The Bosch-fible "Kraftfahrzeugtechnisches Taschenbuch" s.561/561 illustrates this process very good (ISBN 978-3-8348-1440-1). But it is written in german language (I'm from Germany).
A process, that sprayes on closed and open valves,too, is called "sequential injection". The Induktion System is matching with this methode for injection. The fuel will be shot in multiple injections. HPBooks "Performance Fuel Injection Systems" by Matt Cramer/Jerry Hoffmann describes this on page 18. There is a gain of 3-4 HP on a 500 HP-engine with this methode. but the inlet-intake and cylinder-head must match. Most stock ECU's do not support this.
That is what I understand the Mustang PCM does so why assume it does not for your calculations? If the PCM does this then the duty cycle is not 3/4 of the process you need to include the open valve time as well.
My calculation for user 8850 based only on datas of the injectors and the powerlevel of his car. Not on parts of cycles or so. At 6500 rpm cycle time is 18,46154 ms. For every 4-stroke engine, at every HP-Level. The calculated injection-time of 15,5045 ms is the result of the datas for offsettime, breakpoint(mass/time) and flow rate low and flow rate high, the datas for only this calibration. It is not based on parts any cycle.
General must the injection-time be shorter than the cycle time of the 4-stroke. If not, then the injector will fail (overheat,etc.). General the maximum of duty should not be more then 85%. And this depends on the time for the actaul rpm. the higher the rpm, the shorter the cycle-times. At user 8850's engine, the maximum at 85% duty cycle is 0.85*18.46145 ms=15.6923 ms. OK?
What did I mean with 3/4? OK: 1/4 Intake-stroke, 1/4 compression stroke, 1/4 power-stroke, 1/4 exhaust-stroke = 4/4 cycle-time. Think only a moment, that you should not inject at the intake-stroke (->intake-valve open!), then the result is, that you can only inject fuel at 3/4 of the 4-stroke-cycle-time. So, if your injectors can not inject the amount of fuel, that's necessary for the wanted powerlevel in this time, then they are not big enough.
I hope, this a clearer to understand. I understand, that you have another opinion or education about inject fuel on open valves. OK, I accept your opinion, but I don't think so.
No responsibility for translation errors.
If this was true then that would be OK, it is theory that is not happening with these engines. Go and get the actual injector pulse width (you can get it with SCT and soon with HP Tuners) and this is just not happening. Also you would need your intake cam with less than 180 degrees duration.
Duty cycle is a myth, you need to actually understand how much time is available for the injector. If you check Injector Dynamics they have their ID injector showing it can flow at a linear rate for 9.5ms out of 10 ms (100Hz cycle). What this tells us is that the recovery time for the injector is under 0.5ms and that the injector can flow for approximately 8.5ms when we have the offset around 1ms. So at 6000rpm we have 20ms - 0.5ms - 1ms = 18.5ms, or approximately 17.5 ms of actual flow.
As for:
At what rail pressure was this calculated (looks like just under 4 bar to me so a boost of just under 1.3bar). That engine with that boost will make a lot more than 700hp!
I don't check with injectors from other cars or manufactors. I have used the Injector-Datas, that are used in user 8850's engine. And I used the datas that are used by user 8850's calibration file. I use no datas from whatever. The calibration use offsettime, breakpoint(mass/time) and flow rate low and flow rate high. The reference for this datas can you find there, too. I calculate with standard datas for voltage and pressure. User 8850 wrote nothing about differences that Ford or he did in his car. So I think his electrical power System is stock, so I use standard system voltage. About fuel pressure, fuel rail pressure and boost. Ford programmed the PCM. User 8850 wrote nothing about changes or the use of an aftermarket PCM. This means, that the PCM regulates the fuel pressure. The PCM knows the boost level, temperatur of fuel, Environment and intake, air pressure and so on. The PCM regulates the rail pressure. If boost raises, the rail fuel pressure raises in the fuel rail. But that means not automatically, that the difference pressure between boost pressure in the intake manifold and the fuel rail raises. It is only necessary to raise the fuel pressure to the Level, that the difference pressure between boosted air in the manifold and the fuel rail holds the effective pressure with that the fuel is flowing through the injectors. It is not necessary to raise the effective fuel pressure on boosted engine. On N/A-engines it's the same. Of course it is possible, that the manufactur uses the methode to raise the effective fuel rail pressure. In this case the injectors can deliver more fuel in shorter times. But User 8850 did only want to know: Are the injectors big enought for his engine. And they are. At standart fuel pressure (effective (difference-pressure) in his case at his powerlevel their maximum duty is 84%.
user8850discus.jpg
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I bought the car used but to my knowledge the voltage, pressures and PCM are all stock. And it came with all the mods to make the power it's making as I have not added anything. Thanks again for all the great info!
Last edited by 8850; 05-08-2015 at 02:33 PM.
Given the above pressure differences (yes I should have checked the pressure drop at high load is 56psi) then I think your calculations are slightly high. Just to check and for those interested in the calculation I getAs you say they are fine. It was interesting that a while ago the theory was that you should only inject when the intake valve was openCode:High Slope 88.38023468 lb/hr (Multiplier is 1.194475998) Low Slope 67.92889443 lb/hr (Multiplier is 1.194475998) Breakpoint 0.00001789 lb (Multiplier is 1.277831011) Breakpoint time = 0.728715 ms (Breakpoint/High Slope) So: 0.000294583 lb of fuel requires (0.000294583 - 0.00001789)/(67.92889443/3600) = 14.6638 ms + Breakpoint time = 15.3925 ms
Last edited by DarrylC; 05-09-2015 at 03:05 AM.
NO, I never meant you should only inject when the intake valve is open! The best vaporization is by injecting on the hot intake valve when it is closed ore just opening! See:
Matt Cramer and Jerry Hoffman in their Book “Performance fuel injection systems”, HPBooks, ISBN 978-1-55788-557-9, S. 18:
“Many systems do implement some form of timing, although it may be timed to spray onto the closed (and hot) valve to vaporize the fuel better, often just before the valve opens. Sometimes it continues to spray as the valve opens, but before the valve closes.”
This sentence lead me to the safe general expression about 3/4 of cycle time, not exactly at the decimal point, of course. In this safety margin of 10 % from 75% (-> 3/4!)to 85 % are dynamic influences like voltage or pressure changings, etc. included. Special race engines with big cames and maybe multiple injectors are another game.
My intention was to answer user 8850 question. I suggested a safe and easy methode to check this by calculating, because HPTuners cannot log this duty-times. To calculated this time is an easy way to check the times. If anybody needs the exact times under real time circumstances, then it’s necessary to messure the puls by a sampling oscilloscope or so, on the fly.
I suspect that sentence should be read in the context of fuel economy and emissions and not outright power. You have answered 8850 question but brining in your generalisation is off topic. Until HP Tuners gets the DMR function happening you will need to use SCT or an application like Torque to get the injector pulse (minus Offset).
This discussion is off topic, that's right. Then your replys are off topic, too, are they? Let's take your last contribution. You wrote "I suspect that sentence should be read in the context of fuel economy and emissions and not outright power." The Book is titled :"PERFORMANCE fuel injection systems". Did you read this book?
I did not put it in, you put it in as fact. I have never seen this and I was merely challenging your statement to get some actual engineering information around what you were saying.
What port injected engines do this in production?
Re:
“Many systems do implement some form of timing, although it may be timed to spray onto the closed (and hot) valve to vaporize the fuel better, often just before the valve opens. Sometimes it continues to spray as the valve opens, but before the valve closes.”
If you read what is written it talks about when fuel is injected in general and that many systems do implement some form of timing. Yes they do particularly around idle and low loads and it can be very helpful with wild cams but that is the opposite of what you suggest. Your conclusion of 75% is not supported by this statement at all.
As you claim 3-4 horsepower on 500HP engine which is < 1%, hopefully it repeatable and that the statistical error is significantly less than 1 % to draw this conclusion.
Yes I have read the book and I did not make the conclusions you did. It is also available on Google books and I though it was a good read but it was published in 2010 and I read it late 2011 so a while ago.
You did a good job and giving 8850 an IDEA of what the injectors would be.
Not interested in any more on this topic.
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