How much boost with stock Injectors???

[JoEgsX90]

Running a 190 fuel pump with stock injectors othe mods on my profile....Im getting a SAFC2 and wondering how much boost can i run with the stock 450's??

 

[JoEgsX90]

thanks man u deff clreared alot upp.....Yea i know wideband is the best to go with i was just curious about the af gauge the DiGITAL one that displays number not the light show and tap it into the o2 sensor just because i have one lying around... But im guessing it would be inaccurate.

 

[habitatguy187]

This thread is full of misinformation.

The first place to start is with the safc and stock injectors. You can use a safc with stock injectors to increase horsepower and create smoother power delivery, the stock tune is not set up for the most possible power available, it is a canned and conservative tune designed to give the most power available that will consistently be reliable even in a badly maintained car. There is definitely room for improvement.

This idea of running injectors up to 100% duty cycles is completely ridiculous and stupid! 100% duty cycle means that the injector NEVER closes so at a maximum you should really only run up to about 80%.

The idea of injectors sizing based on horsepower is also pretty silly. By the time you factor in drivetrain losses and the huge difference in horsepower based on environmental factors this is just a silly number with no real world correlation when we try to use it as a constant measure.

Fuel cut and injector sizing should be (and are) controlled by airflow which is correlated to boost pressure as a function of VE.

The point ends up being that the maximum boost anyone would ever want to run if they didn't have a logger under any conditions is 15lbs (if you have a rewired fuel pump!). This coincidentally is also the number that anyone who is sane will use as their maximum boost pressure with stock injectors unless they CONSTANTLY log what is going on in their engines because environmental factors will change both the airflow curve(AITs, atmospheric pressure, atmospheric composition, etc) and the timing curve (AITs). This is because boost is not a good measure of airflow.

Finally, do not even bother having one of those blinky light A/F gauges since they are completely useless. If you want to know what is going on in your engine get a wbo2 setup and be done with it.

Edit:

Lets add some fuel pump information!

Fuel pumps are another misunderstood subject. A fuel pump such as a 190lph pump will not let you run any higher boost than a rewired pump will, what it will allow you to do is supply larger injectors with enough fuel to work properly. Don't fall into the trap of thinking that your motor can take it, if you can't invest enough to get larger injectors you can't afford a new motor so don't do it.

A 255lph HP pump would allow you to run a higher boost setting because you will overrun the stock fuel pressure regulator and have a higher fuel pressure which will make the injectors flow SLIGHTLY more but you have the downside of a potentially unreliable tune and reduced fuel pressure at higher IDCs.

The better way to make stock injectors flow more is to get a AFPR which will allow you raise the fuel pressure consistently and run slightly higher boost without danger. Finally a workable solution without bigger injectors :thumbsup: , this is why you read my whole post isn't it?

Yeah he's right, vfaq is obviously wrong, like always.....

 

[1qkfwd]

This thread is full of misinformation.

The first place to start is with the safc..........

I hope you are not referring to me on this. I am in know way a no-ob to tuning. Those numbers are for our cars and are real numbers provided by old school dsmers. Not just some calculated numbers blah blah. HP is how you find the injector you need. So when you upgrade your injectors, do you call and say hey I am going to be running 25lbs of boost on my talon what do you have that will work? On my stock talon with just a 16G and a rewired 190lph I am pushing 17lbs on 91oct and 23-24 on 100oct with the stock 450cc injectors. At that boost level the car only sees 88-89 IDC. I chip my own ECUs tune the chip and all that. So saying that 15lbs is the limit of the 450cc injectors is misinformation. That is the limit when you reach fuel cut with a 16G turbo or a turbo with equivalent air flow ratings.

 

[JusMX141]

Second, not trying to be rude, but don't give me or someone like me a newb 101 explanation to fuel cut... I didn't ask for it and I didn't need.

I wasn't trying to corner your tuning intelligence....your previous post just made it seem that if you routinely ran your car as close to fuel cut as you did without any type of logger or monitoring then you either had no clue what you were doing or you enjoyed kicking your car in the balls on a daily basis.

It's all good.

 

[gsxeclipse97]

Well I don't see how you were able to run your car at 18psi without hitting fuel cut. On a cool night at 15psi i hit fuel cut. but that may also be because i have a 1g head instead of a 2g, but not sure though if that would make a difference as far as the amount of boost goes.

 

[1qkfwd]

Well I don't see how you were able to run your car at 18psi without hitting fuel cut. On a cool night at 15psi i hit fuel cut. but that may also be because i have a 1g head instead of a 2g, but not sure though if that would make a difference as far as the amount of boost goes.

I don't know if you are referring to me on this but if so it is because I chip my on ECUs and rid of fuel cut so the car will run how it was suppose to. Its not to hard to steer away from fuel cut. At least on a 1G. I am not to sure where the limit for fuel cut is on a 2G.

 

[z24frank]

So my question is still remaining,is there ap pre set number?or are there to many variables to do this?

 

[kevingst]

Too many variables. I also forgot to mention that the Gst had a 6 bolt swap in it... so maybe with the lower compression I was able to get away with it. At 18psi I never had any problems with drivability. z24frank, seeing as how you're in Cali, I'm assuming you can only get 91 octane at the pump... so that's another variable that you'll have to account for that I didn't have to deal with at the time.

 

[the_mork]

I hope you are not referring to me on this. I am in know way a no-ob to tuning. Those numbers are for our cars and are real numbers provided by old school dsmers. Not just some calculated numbers blah blah.

Every car is different, what worked on another car probably will not work on yours, as for you being a noob to tuning you may not be but when I see things like

HP is how you find the injector you need. So when you upgrade your injectors, do you call and say hey I am going to be running 25lbs of boost on my talon what do you have that will work?

then I assume I should step in and clarify. When you call to upgrade your injectors you usually tell the person you are ordering from which injector you want and at what flow rating, then if you are a serious racer you get them flow tested before putting them on your car because you already know what you need.

If you don't know what you need then the best possible information is to provide a flow rating in lbs/min. Did you miss where I said boost and horsepower are useless real world numbers? Plus if you are tuning with an EMS or dsmlink its all kind of moot for injector sizing anyways because you just get the biggest injectors (at a reasonable price) that you can find.

On my stock talon with just a 16G and a rewired 190lph I am pushing 17lbs on 91oct and 23-24 on 100oct with the stock 450cc injectors. At that boost level the car only sees 88-89 IDC. I chip my own ECUs tune the chip and all that. So saying that 15lbs is the limit of the 450cc injectors is misinformation. That is the limit when you reach fuel cut with a 16G turbo or a turbo with equivalent air flow ratings.

Just how stock is this talon? To be able to run those numbers and get away with it (you really aren't getting away with it at those duty cycles) you will need to have some sort of serious restrictions and high intake temperatures or low barometric pressure (what elevation are you at). Serious restrictions would involve a stock airbox, stock sidemount, stock exhaust, intake manifold, etc.

So you've found the magic key to having high boost and getting away with it which I also mentioned in my other post, run a stock setup which will have you running with a VE that is lower at 18psi on a 16g than most people manage at 14psi with a t25 with minor boltons. Don't try to run the same pressure closer to sea level or at lower temperatures.

The other thing to consider is at what point are you measuring your duty cyles? Was that a 3rd gear pull? Try doing a lonely highway pull to the top of 4th or through some of 5th since this is where you will really see your idcs peak.

 

[Calan]

HP is how you find the injector you need.

Huh?

Ok... I'm targeting 500hp for my current build (2.3L stroker). What size injectors do I need?

The idea of injectors sizing based on horsepower is also pretty silly.

Agreed. There are so many factors that govern the amount of fuel flow you need for a certain power level that it's impossible to pick an injector based on HP.

The most obvious variable that nobody mentioned is AFR. Running 10:1 requires different flow rates than 11.5:1. Not to mention different fuels: E85 for example requires 20-30% more fuel per given volume of air...so larger injectors are needed. Then there is the matter of base fuel pressure, etc etc etc.

No offense, but anyone that's "going to use a digital A/F gauge tapped into the 02 sensor to monitor the ratio" should do a bit more reserach before deciding on any fuel system upgrades.

 

[1qkfwd]

Every car is different, what worked on another car probably will not work on yours, as for you being a noob to tuning you may not be but when I see things like
then I assume I should step in and clarify. When you call to upgrade your injectors you usually tell the person you are ordering from which injector you want and at what flow rating, then if you are a serious racer you get them flow tested before putting them on your car because you already know what you need.

If you don't know what you need then the best possible information is to provide a flow rating in lbs/min. Did you miss where I said boost and horsepower are useless real world numbers? Plus if you are tuning with an EMS or dsmlink its all kind of moot for injector sizing anyways because you just get the biggest injectors (at a reasonable price) that you can find.

Ok here I know all this you didnt catch the sarcasim with my statement. Yes I know that you find a flow rating when you call and order a set of injectors. That flow rating is based on a HP number that they will support. Example to run 500 Hp as long as the rest of the fuel system is up to par your injectors will have to have a certain flow to fuel that HP level. Then it goes on and on because things change up depening on what octane gas you are using. Pump gas cars, bigger injectors to compensate for lack of octane and high octane cars, allows us to use smaller injectors.

Just how stock is this talon? To be able to run those numbers and get away with it (you really aren't getting away with it at those duty cycles) you will need to have some sort of serious restrictions and high intake temperatures or low barometric pressure (what elevation are you at). Serious restrictions would involve a stock airbox, stock sidemount, stock exhaust, intake manifold, etc.

So you've found the magic key to having high boost and getting away with it which I also mentioned in my other post, run a stock setup which will have you running with a VE that is lower at 18psi on a 16g than most people manage at 14psi with a t25 with minor boltons. Don't try to run the same pressure closer to sea level or at lower temperatures.

The other thing to consider is at what point are you measuring your duty cyles? Was that a 3rd gear pull? Try doing a lonely highway pull to the top of 4th or through some of 5th since this is where you will really see your idcs peak.

The car is pretty much bone stock. You nailed it right on with the restrictions I am still running the full turbo back exhaust, intercooler system, and hacked air box. I am also at an elevation of 4800 FT. My engine also lack a ton of compression more like low 100s. So that there. Is one other reasons you cant just put a PSI number on a set of injectors. There are to many variables to just set that in stone. The O.P. needs to have a logger and tune the car properly add boost until he finds a safe threshold. That is really the only way to know how many lbs of boost his 450's will hold for boost.

Huh?

Ok... I'm targeting 500hp for my current build (2.3L stroker). What size injectors do I need?

Go to RC enginering's website or yahoo search fuel injector sizing and there are a bunch of calculators that will help you here. Again to many other variables to just throw an injector size. You need to now what octane fuel you need and a few other things.

 

[Calan]

Huh?

Ok... I'm targeting 500hp for my current build (2.3L stroker). What size injectors do I need?

Go to RC enginering's website or yahoo search fuel injector sizing and there are a bunch of calculators that will help you here. Again to many other variables to just throw an injector size. You need to now what octane fuel you need and a few other things.

You didn't catch my sarcasm

My point was that there is no way to recommend an injector based on HP. Read the second half of my post

To accurately calculate the required injector size, you would need to know (at a minimum):

1. target airflow
2. base fuel pressure
3. target IDC
4. fuel type
5. desired A/F ratio

Of course you also need to consider how you are going to tune them if you go bigger than 650's. But with something like DSM link, you can just go big and let the software do the math.

 

[the_mork]

Ok here I know all this you didnt catch the sarcasim with my statement. Yes I know that you find a flow rating when you call and order a set of injectors. That flow rating is based on a HP number that they will support. Example to run 500 Hp as long as the rest of the fuel system is up to par your injectors will have to have a certain flow to fuel that HP level. Then it goes on and on because things change up depening on what octane gas you are using. Pump gas cars, bigger injectors to compensate for lack of octane and high octane cars, allows us to use smaller injectors.

Nope this is wrong

The car is pretty much bone stock. You nailed it right on with the restrictions I am still running the full turbo back exhaust, intercooler system, and hacked air box. I am also at an elevation of 4800 FT. My engine also lack a ton of compression more like low 100s. So that there. Is one other reasons you cant just put a PSI number on a set of injectors. There are to many variables to just set that in stone. The O.P. needs to have a logger and tune the car properly add boost until he finds a safe threshold. That is really the only way to know how many lbs of boost his 450's will hold for boost.

I absolutely agree with the fact that the OP needs a logger but until then 12-15psi is usually fairly safe depending on some other variables.
If you need another opinion RRE has a similar take on it. Road Race Engineering's Eclipse Fuel Delivery Upgrades

So now let me get this straight, you are using the absolute best circumstances for allowing high boost readings without damage (low VE, low compression, high altitude, and good gas) and then pushing that envelope? That's fine you'll probably get away with it. The important question is were you really telling the OP that it would be safe to tun his setup at the same settings? If so I think I just saved you some lost sleep over destroying someone's car, or maybe you just don't care.

Go to RC enginering's website or yahoo search fuel injector sizing and there are a bunch of calculators that will help you here. Again to many other variables to just throw an injector size. You need to now what octane fuel you need and a few other things.

Or you could just know about what you flow at a given time and throw an extra 15-20% buffer in their and size some injectors to make a good AF ratio.

 

[Moparbishi]

I have ran 18psi on a big 16g with the 450s, with just walbro 255. I have adjusted timing a little bit with dsmlink. I have no knock and running a 11.1 afr. I havent adjusted fuel at all. I havent logged my duty cycle yet. I will be putting in 650s this spring for more boost.

 

[1qkfwd]

Nope this is wrong

So you are saying that a 18lb/min will support 500hp? And that a 80lb/min injector would work good for a mild setup with a 16G front mount on a stock engine? Explain why this is wrong I believe this info is pretty accurate.

I absolutely agree with the fact that the OP needs a logger but until then 12-15psi is usually fairly safe depending on some other variables.
If you need another opinion RRE has a similar take on it. Road Race Engineering's Eclipse Fuel Delivery Upgrades

Agreed on this. My point was that there are to many people setting a certain boost level and saying that this is all you can on 450cc injectors. I was trying to emply that there is not a certain boost level for a set sized injector.

So now let me get this straight, you are using the absolute best circumstances for allowing high boost readings without damage (low VE, low compression, high altitude, and good gas) and then pushing that envelope? That's fine you'll probably get away with it. The important question is were you really telling the OP that it would be safe to tun his setup at the same settings? If so I think I just saved you some lost sleep over destroying someone's car, or maybe you just don't care.

I didnt tell him to run what boost settings I do. People where just throwing numbers out there saying that it will work. I stated that you can run more boost through a 450cc injector than what was claimed they are good for. I didnt want him to blow up his engine. It was quoted by another poster that the injectors are good for 15lbs. So what if O.P. turns up the boost to 15lbs and boom there goes his engine, because his setup made more power than the injectors where good for. His safety level may only be 12lbs. As I qouted before. The only way to know for sure on his setup how much boost he can run is to log turn the boost up little by little until he gets a slight bit of knock and turn the boost down a pound or so to be safe.

 

[GalantGreg]

Sorry to hijack, but this is interesting to me because it fits the plans for my modest build. My auto came with 390cc injectors. In my rebuild, I am only upgrading to 450cc I got from a 2g, a fresh rebuilt 16g turbo, and a 1g EPROM. I want to be able to at least make 300hp. Will I need a tune with the EPROM?

 

[the_mork]

So you are saying that a 18lb/min will support 500hp? And that a 80lb/min injector would work good for a mild setup with a 16G front mount on a stock engine? Explain why this is wrong I believe this info is pretty accurate.

The problem is your continued assumption that talking about horsepower relates to any part of an intelligent conversation about tuning. Horsepower is about the most subjective number we can calculate especially with your method of using trap speed and ETs. Even on a well calibrated dyno we wouldn't be able to get consistent numbers closer that about 5% and then you need to count in that particular dyno's inflation or deflation of the numbers and the car's tune and the unsprung weight not to mention drivetrain losses and combustion efficiency. Figure out the peak VE or a normal VE and add a bit more in lb/min or g/rev and you can figure out where you are going.

I didnt tell him to run what boost settings I do. People where just throwing numbers out there saying that it will work. I stated that you can run more boost through a 450cc injector than what was claimed they are good for. I didnt want him to blow up his engine. It was quoted by another poster that the injectors are good for 15lbs. So what if O.P. turns up the boost to 15lbs and boom there goes his engine, because his setup made more power than the injectors where good for. His safety level may only be 12lbs. As I qouted before. The only way to know for sure on his setup how much boost he can run is to log turn the boost up little by little until he gets a slight bit of knock and turn the boost down a pound or so to be safe.

I read through your replies in the thread, it seemed pretty clear that you were implying a high boost is safe to run. Everyone else who presented low numbers were offering a safe upper limit, it goes without saying that if someone has a logger and some sort of tuning device that they can run more boost (if the logs support it) IF they know what they are looking for which someone who needs to ask the question does not.

 

[the_mork]

Sorry to hijack, but this is interesting to me because it fits the plans for my modest build. My auto came with 390cc injectors. In my rebuild, I am only upgrading to 450cc I got from a 2g, a fresh rebuilt 16g turbo, and a 1g EPROM. I want to be able to at least make 300hp. Will I need a tune with the EPROM?

You aren't going to make 300whp on 450cc injectors, you might just maybe manage something close to that at the crank but honestly the 16g is kind of pointless without larger injectors you might as well just get a cheaper 14b.

The eprom ecu is not any better than any other (same transmission) ecu. The only advantage to it if you are not using a chip is that it lets you run 450cc injectors assuming it is from a manual transmission car. The problem comes in that 450cc injectors are not all equal and the 450cc injectors from a 2g flow different than those from a 1g. It isn't much and in closed loop mode (partial throttle and cruising most of the time) the ecu will compensate based on feedback from the o2 sensor but at WOT the ecu just uses unmolested fuel maps and will run slightly rich because if I remember correctly 2g 450s flow slightly more.

All in all you will need a chip from someone or some other way to tune (dsmlink, safc, etc) but since you have the eprom you might as well use a chip (and maybe an safc for fine tuning). You will also need a fair amount of other parts to get to your 300whp mark.

 

[turbogst98]

Despite the rumors of fuel cut being caused by too low of fuel pressure, too small of injectors, high flowing exhaust, high flowing intake, or large turbos fuel cut is not directly caused by any of these. Fuel cut is actually caused by the ECU seeing more air entering the engine than it was originally programmed to use. This likely cooresponds with an injector duty cycle which is unsafe or unattainable. So basically fuel cut is caused by the MAF seeing too much air.
its different for every car so thats why some peopleget fuel cut and some people dont
its all about air
so if your mass air flow sensor is bad your going to get some bad fuel cut

 

[jerseydiver84]

if your worried you cant achieve your goals on stock injectors and stock fuel set up, then save up and get the afc then go get some 550s, a fpr and a 255 fuel pump, get a wideband a boost gauge and a mbc. lastly get a good tune.

 

[jerseydiver84]

i just saw your list of mods on your car and you might have the most mods without fuel upgrades then ive seen, once you get that fuel issue squared away you might wanna invest in a lsd and some drag radials, that right there will make a huge difference in your car.

 

[the_mork]

Despite the rumors of fuel cut being caused by too low of fuel pressure, too small of injectors, high flowing exhaust, high flowing intake, or large turbos fuel cut is not directly caused by any of these. Fuel cut is actually caused by the ECU seeing more air entering the engine than it was originally programmed to use. This likely cooresponds with an injector duty cycle which is unsafe or unattainable. So basically fuel cut is caused by the MAF seeing too much air.
its different for every car so thats why some peopleget fuel cut and some people dont
its all about air
so if your mass air flow sensor is bad your going to get some bad fuel cut

This is mostly correct but I also think it has already been brought up in this thread. Fuel cut does correspond to the point at which a factory car will reach about its maximum IDC.

 

[gsxeclipse97]

Well that answers my question. I'm here in Houston. And siting at sea level or slightly below. I cannot go above 15psi at all and as far as mods go I would say my car is still pretty stock also. So if the ecu is seeing to much air enter then couldn't you just upgrade your Maf to an evo or blow through set up and along with a better fuel system? Cause it seems to me you really just need a wayto trick the ecu to seeing less air than what is really comming in.

 

[1qkfwd]

The problem is your continued assumption that talking about horsepower relates to any part of an intelligent conversation about tuning. Horsepower is about the most subjective number we can calculate especially with your method of using trap speed and ETs. Even on a well calibrated dyno we wouldn't be able to get consistent numbers closer that about 5% and then you need to count in that particular dyno's inflation or deflation of the numbers and the car's tune and the unsprung weight not to mention drivetrain losses and combustion efficiency. Figure out the peak VE or a normal VE and add a bit more in lb/min or g/rev and you can figure out where you are going.

You are taking this to level that is not necesssary. You don't need a Dyno to find injectors for a car, so you don't need to go into all this added discusstion about VE or drivetrain loss. Horsepower has everything to do with tuning. You don't get horsepower from nothing. You have to get a start from somewhere. So you are saying that this formula is useless in finding an injector in a close range:

Horsepower X B.S.F.C = LBS/hr (per injector)
----------------------------
No.of injectors X Desire duty cycle

-In most cases a naturally aspirated engine will have a B.S.F.C of .50. This means that the engine will use .50 lbs. of fuel per hour for each horsepower it produces. Turbocharged engines will want to be at .60 lbs. per hour or higher.

-Using these numbers as a guideline, you can select the approximate injector size in the following formula for a four cylinder, naturally aspirated engine at 200 bhp.

-Most injectors will max out at 80% duty cycle and this is the accepted industry standard.

-B.S.F.C is brake specific fuel consumption - How much fuel you are using per horsepower per hour

So I am going to run a GT14 turbo on my stock 2.0 engine with cams. How would you go about finding the right size injectors. I will be tuning with maf translator if that helps out any.

I read through your replies in the thread, it seemed pretty clear that you were implying a high boost is safe to run. Everyone else who presented low numbers were offering a safe upper limit, it goes without saying that if someone has a logger and some sort of tuning device that they can run more boost (if the logs support it) IF they know what they are looking for which someone who needs to ask the question does not.

Maybe I should clear this up here. I am saying that you can run a higher boost level on 450cc injectors than what some members on this topic are claiming. I should have pin-pointed who I was talking to but this was not for the O.P. If I was to comment on what would be a safe limit for just the O.P.s current setup, I would suggest leaving the boost alone until he gets a logger to make sure he is not going to pop his engine. You are not comprehending this the way I am intending it to sound.

This is mostly correct but I also think it has already been brought up in this thread. Fuel cut does correspond to the point at which a factory car will reach about its maximum IDC.

You might want ot recheck this. The ECU initiates fuel cut when the calculated airflow goes over a set value. It in no way correspond with maximum IDC. This has nothing to do with a certain boost level. If you have done any ECU tuning you would know this. Why do some hit fuel cut or not you ask with pretty much the same setups??? Say fuel cut is to iniate at 2000HZ. The first car with a leaky throttle body and a couple leaky vacuum lines, when it hits say 15 lbs of boost it has to draw more air through the MAS to compensate for the leaks just to hit that 15 lbs to make the wastegate happy. So it has a beter chance of hiting that 2000HZ the mas reads. Second car has zero leaks and a tight system. It hits 15lbs and will read a lower count of HZ because none of it is leaking out of the already counted for readings. This car will not hit fuel cut so soon so now you can run this at a higher level of boost before it does fuel cut. The IDC comes into play because it coresponds with the mas flow HZ through the ecu. You can hit fuel cut before you run out of injector on a 450cc. This on my part maybe a poor explination on this but it covers the basis.

 

[1qkfwd]

Well that answers my question. I'm here in Houston. And siting at sea level or slightly below. I cannot go above 15psi at all and as far as mods go I would say my car is still pretty stock also. So if the ecu is seeing to much air enter then couldn't you just upgrade your Maf to an evo or blow through set up and along with a better fuel system? Cause it seems to me you really just need a wayto trick the ecu to seeing less air than what is really comming in.

You can run a bigger injector then you would have to lean it out with some sort of piggyback thus tricking the ecu into seeing a lower airflow level. You could also run a bigger pump than required so you have to lean it out to get desired AFR. So running a 190lph pump with 450cc injectors is a plus. You will be able to get the most by keeping a low boost level and just leaning it out. If you upgrade to a different maf you will still need a piggyback to dial the new sensor in because it does flow at a different rate. The downside to running a piggy back to control bigger injectors though, when tricking the Ecu to a lower airflow level it then uses a lower section of the fuel and timing maps. In turn the ecu will provide higher timing numbers at WOT the more you lean it out. So you idealy want to run the smallest injector you can get away with for your particular setup. When you stepup to any sort of EMS, injector size is not that big of a deal because you have a way to control your fuel and timing separately.