Well as the tittle says, ive been looking for answer everywhere but i dont get the right ones so...... here is what i mean now
ok on the supercharger reflash the injectors are 310cc right thats what they are at 43psi
on the stock 2.4 injectors these are 252cc at 43psi
when we turbo our cars using ford brown tops we turn the pressure down because the car wont idle for the big injectors cause the computer was not set to run them so when we run these on 28-30 psi fuel pressure these injectors become now 279cc wich is a little rich but the car will idle and drives great.
now on the supercharger reflash the computer gets set so that it can run 310cc injectors at 43psi.
so now here is where it doesnt make sense, if the car is flashed to run 310cc injectors at 43-45psi wich these are like 29-30 pound injectors, why couldnt i run 440s and turn the pressure to 22psi wich will make these run at 29pound or 310cc.
I already asked shifted and all he said was HPtuners, i know alot of you like the program, its nice and all but why would i spend 700 dollars to be able to adjust my fuel just to run the 440s. I know all you can do with hp tuners i look at the site every night, and so far i dont like the fact that for 700 dollars your car still dont read boost, i dont really care for the FAKE 2 bar if they were going to make a program to tune a vehicle they could of at least given an option were to choose and map setting from 1bar 2bar and 3bar also an option for fuel pump to tell the computer that you have a 255 liter pump and one for what injectors you have, etc..........
reason i say all of this is because AEM ems has all these options plus more for only a couple hundred dollars more than hp tuners.
I dont want to sound like a di#@ about all of this but damn im just irritated with some of GM desicions like not building a car already turbo with potential in the mid to late 90s it would of made our lives alot easier, now we got to spend 700 dollars on a program to tune our cars then we got to get a( wide band ) wich is not a bad idea at all ,then we got to go to the dyno and then we have to spend more money because we werent happy with some results etc ect......... so now you are atleast between 1300 to 1700 dollars in just tuning your car just so you can make 250 to a little over 300 hp. I looked at the list of boosted cars here and a very little amount of them are over 300whp. My turbo kit was a 1200 dollars on my turbo kit and this include the fuel pump, ford brown tops, regulator and 12:1 FMU, my car put down to the wheels 245 hp reading 1355 on my EGT gauge at wot. My egt gauge is right on the manifold also. I didnt use anything to tune my car and i drove my car for 2 years like that till i desided to build the motor cause my tranny went out.
Im sorry that i snapped like this, i had a bad day today sorry for taking it out on you guys.
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the problem with dropping fuel pressure down so much, is the risk you take it not being able to atomize the fuel sufficiently at idle.
If it is not atomizing properly, there's a possibility of an erratic idle, or a surging idle. (too lean, too rich, too lean, too rich)
and I think the AEM is pretty good, but the big block guys are using something else (Big Stuff 3, IIRC)
the AEM is good for us rice burners though.
Don't go with the Holly Commander, I wish I never did.
I would not throw the HPT idea out just yet. There are ALOT of other things you can change that you may be very interested in. I mean sure you can use an afpr and an fmu but all you are doing is trying to bypass what the computer is doing. Doesn't it just make more sense to change the computer which is at the root of the problem. If you modify the gm reflash HPT reads boost. Sure you can do all that plus a litle like you mentioned with AEM ems but that is a full standalone.
FORGET GIRLS GONE WILD WE HAVE GOVERNMENT SPENDING GONE WILD!
I guess I didn't explain it very well...
Ok, you have 310cc injectors rated at 45psi right? 45 psi is WOT, at idle you are probably running 150cc injectors due to the lower fuel pressure.
When you adjust your idle fuel pressure down to, lets say 23psi for math's sake, you're 440's are running at 220cc's. Still 50% more fuel than stock even though you've turned the fuel pressure down more than half way. At 23 PSI you are going to be running into fuel atomization issues, puddling, etc. You're car will throw a rich code because it can't turn the fuel down enough (by cutting the pulsewidth) to compensate. I'm not saying you're car won't physically idle, but you'll have some code issues and at the very least, poor warm starts, black smoke, and stalling.
4cyltuner.com - Information Source For 4 Cylinder Tuners
Buy stuff from CarCustoms Ebay! Won't be disappointed!
having said that, I am idling 720's at 22psi fine, but am running a Holly Commander.
Shifted wrote:I guess I didn't explain it very well...
Ok, you have 310cc injectors rated at 45psi right? 45 psi is WOT, at idle you are probably running 150cc injectors due to the lower fuel pressure.
no, you are idling on 310 injectors. The regulator keeps the pressure difference between the pressure at the injector's inlet and outlet the same.
20 inhg manifold/29psi rail and 0 inhg man/39 rail is 39psi difference in both cases.
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^ Injectors are rated at a particular pressure, with atmosphere on the nozzle side. Decreasing the pressure in the rail effectively decreases the size of the fuel injectors, proportional to the following formula:
F2 = (P2 * F1) / P1
F2 = Flow (in lbs/hr or CC/Min) at the new PSI
P2 = Desired fuel pressure
F1 = Fuel injector flow at the rated PSI (P1)
P1 = Rated fuel injector PSI
So, having 310cc injectors, 45PSI in the rail at WOT, and 39 PSI in the rail at idle, gives:
F2 = (39 * 310) / 45
F2 = 268.6cc
4cyltuner.com - Information Source For 4 Cylinder Tuners
Buy stuff from CarCustoms Ebay! Won't be disappointed!
Just to mention....you can not run a stand alone unit if you live in an OBD II state if you want to keep your car legal, so HPT also has that going for it.
Adjusting fuel pressure alone is not enough to throw a set of larger injectors in, but you might also have the option just to have your car tuned by a shop that uses HPT, instead of throwing down the $650 for your own.....just a suggestion
Shifted wrote:I guess I didn't explain it very well...
Ok, you have 310cc injectors rated at 45psi right? 45 psi is WOT, at idle you are probably running 150cc injectors due to the lower fuel pressure.
When you adjust your idle fuel pressure down to, lets say 23psi for math's sake, you're 440's are running at 220cc's. Still 50% more fuel than stock even though you've turned the fuel pressure down more than half way. At 23 PSI you are going to be running into fuel atomization issues, puddling, etc. You're car will throw a rich code because it can't turn the fuel down enough (by cutting the pulsewidth) to compensate. I'm not saying you're car won't physically idle, but you'll have some code issues and at the very least, poor warm starts, black smoke, and stalling.
Ok now im more confused, i thought that the 43psi was for idle, how can it be 43-45 all the way the thru the RPM band at WOT.
Another thing, doesnt the gm reflash change the constance for the new injectors so that it can idle at 43psi with the 310cc injectors?
I know you guys are trying to help but i just want clear answers, i do admit tho im not a tuner, but i can build the crap out of any motor but my weakness is tuning so... i know there are alot of you here that are very smart in that department so, thats why im asking about all this info but at least im not asking stupied questions.
I thank all of you that are trying to help, thank you much.
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Quote:
I dont want to sound like a di#@ about all of this but damn im just irritated with some of GM desicions like not building a car already turbo with potential in the mid to late 90s it would of made our lives alot easier, now we got to spend 700 dollars on a program to tune our cars then we got to get a( wide band ) wich is not a bad idea at all ,then we got to go to the dyno and then we have to spend more money because we werent happy with some results etc ect......... so now you are atleast between 1300 to 1700 dollars in just tuning your car just so you can make 250 to a little over 300 hp.
so just out of curiosity... why did you goto the dyno with no way to tune your car...?
I sympathize with your frustration, but your I'm sorry to say.. its your own fault.
why spend the money on the parts but not on the electronics to run them?
so just out of curiosity... why did you goto the dyno with no way to tune your car...?
I sympathize with your frustration, but your I'm sorry to say.. its your own fault.
why spend the money on the parts but not on the electronics to run them?
dyno was free i dont have to pay for it, just want it to see numbers, afr 11.9 also, now as for me asking questions about all of this is for me not to buy something im not going to be happy with, im not saying that i will not be but i like to know as much as possible about the things i buy so i know i spent my money wisely.
money is no issue but i would like to do atleast 98 percent of my cars work my self including the tuning, but biggest thing is to know everything about everything thats in my car and what it does other than just say what its got and not know what it does.
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Shifted wrote:^ Injectors are rated at a particular pressure, with atmosphere on the nozzle side. Decreasing the pressure in the rail effectively decreases the size of the fuel injectors,
Decreasing the pressure in the while decreasing the pressure at the nozzle the same amount =
the same flow rating
You said:
Quote:
Ok, you have 310cc injectors rated at 45psi right? 45 psi is WOT, at idle you are probably running 150cc injectors due to the lower fuel pressure.
and the reduced fuel pressure you incorrectly say is reducing the flow rating is reduced because the pressure at the nozzle is reduced... aka manifold vacuum at idle. The injector flow stays at 310cc in your example. The pressure differential stays the same.
a 310 cc injector rated at 45 psi is 310 cc if pressure is set to 45 psi at WOT and still remains 310cc when the pressure is dropped by a vacuum referenced regulator. But, if you drop the WOT pressure setting, the injector flow will be reduced overall.
Quote:
So, having 310cc injectors, 45PSI in the rail at WOT, and 39 PSI in the rail at idle, gives:
F2 = (39 * 310) / 45
F2 = 268.6cc
would only be correct if the injector was spraying into the manifold of a diesel engine that does not create manifold vacuum.
Remember the key you are missing here is
DIFFERENTIAL PRESSURE, not static pressure
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Battle of the j-body gods.
jon turbo grand am wrote:so just out of curiosity... why did you goto the dyno with no way to tune your car...?
I sympathize with your frustration, but your I'm sorry to say.. its your own fault.
why spend the money on the parts but not on the electronics to run them?
dyno was free i dont have to pay for it, just want it to see numbers, afr 11.9 also, now as for me asking questions about all of this is for me not to buy something im not going to be happy with, im not saying that i will not be but i like to know as much as possible about the things i buy so i know i spent my money wisely.
money is no issue but i would like to do atleast 98 percent of my cars work my self including the tuning, but biggest thing is to know everything about everything thats in my car and what it does other than just say what its got and not know what it does.
if you want stand-alone level control with low cost and legality I suggest looking into megasquirt
you can set it up to control just your injectors and fix your idle problem and run whatever size injectors and whatever AFR and whatever boost you want (i think they support 5 bar MAP sensors now)
you'd have to re-tune.. the only downside. you'd also be able to eliminate the FMU
stevefire wrote:This link helped me a lot to figure out injector sizing, pressures, and horsepower capabilities.
http://www.rceng.com/technical.htm
ok well i still get the same even using the formulas that RC is giving me wich this is one of them
so this is what he chart told me to do so i did this 22new pressure / by old pressure 43= 0.5116 then i found the sqrt of 0.5116=0.7152 x 440cc injectors=314cc
no matter what calculator i use i always get the same numbers so the question is why wouldnt this work since the injector constance will change after the GMSR to run 310cc injectors.
i thought if i remember correctly that the pressure goes up when vaccume and rpms rise.
i dont get what shifted is saying here below:
Ok, you have 310cc injectors rated at 45psi right? 45 psi is WOT, at idle you are probably running 150cc injectors due to the lower fuel pressure.
When you adjust your idle fuel pressure down to, lets say 23psi for math's sake, you're 440's are running at 220cc's. Still 50% more fuel than stock even though you've turned the fuel pressure down more than half way. At 23 PSI you are going to be running into fuel atomization issues, puddling, etc. You're car will throw a rich code because it can't turn the fuel down enough (by cutting the pulsewidth) to compensate. I'm not saying you're car won't physically idle, but you'll have some code issues and at the very least, poor warm starts, black smoke, and stalling.
http://a709.ac-images.myspacecdn.com/images01/85/l_c45bfa9c54e0aebaf0fbf6bf67c30a74.jpg
jon turbo grand am wrote: no matter what calculator i use i always get the same numbers so the question is why wouldnt this work since the injector constance will change after the GMSR to run 310cc injectors.
Some of your statements are confusing the issue.
Basically you are saying you want 440 injectors to run like 310... a fair enough request, but overall unnecessary as stated.
If you really want to lower pressure just to make 440s run like 310s then the answer is use 310s and forget about it.
But what I hope you are trying to do is use an FMU to set WOT fueling under boost bigger injectors while pulling them back to act like stockers under non boost operation.
Yes it is somewhat possible to do successfully. No it isn't the best way to go. But then again, HPTuners is necessarily better either.
The 1st question is do you need 440s? You can also run the 310s set at 45 with the FMU boosting pressure to 80 which makes them flow like 415s.
When changing pressure to change injector flow, the injector is more consistent as pressure goes up then when pressure goes down.
The formulas are for general ballpark ideas and not totally accurate. If you were to graph any injectors flow v. pressure you will see it is not a perfectly linear graph. But the graph from the area around the rated pressure and up will be far more linear the the reat below the rated pressure.
Heading the other direction, using 440s and dropping pressure, will work ok if pressure isn't dropped much. Dropping below 29 static (which will be below 20 at idle) will begin to lead to things like fuel dribbling and such that will make it run poorly anyway.
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