VF40-18g .... injectors .... benefits?

[Nickz31se-r]

Here we go again right? At the very least this thread should pop up next time some one searches vf40-18g.

Real quick question to throw out there. While a pump is advised and injectors are not needed, are any ponies being left on the table by not upgrading injectors?

 

The only reason I ask, is b/c I purchased some injectors simply to have for my next turbo upgrade:eek:. Yes, I know this turbo will be too small for me in the long run, but I work every other week(7 on 7 off) and enjoy working on my car, so labor is my hobby and both my perrin tmic and turbo were purchased used for a combined tolal of 1100 dollars.

 

I say next upgrade as I still have yet to install my fuel pump, aem intake (yes not needed I know), vf40-18g, and prodrive solenoid. If the reasoning to not upgrade injectors is due to cost (actual injector and dyno tune), I may use them now regardless if some power can be added. I say this b/c I have already paid for the injectors and was planning on getting the car dynoed with a tdc map and then possibly tweeked by a local subie shop.

 

At the very least I will be getting the car dynoed in its current stage2 w/tmic then going back to see the gains withe the hybrid.

 

I opened this thread as ..."real quick question".

[ejoy1220]

I always thought that with the VF40-18g the injectors were more of a peace of mind thing. From what I've seen and heard the stock injectors should flow enough for 300whp +/- (where they are pretty much at their limit in most cases), and going with bigger injectors will drop IDCs from being so high, so you don't have to worry about it.

[urfsin]

If you push it (tune wise or track), plan on injectors and a pump.

[boostsr20]

Targeting 11 as an A/F ratio in upper RPM's I ended up hitting 101 IDC max. The turbo might have had a little left in it with more tuning but I didn't push it simply because I was out of fuel. I'd say get the injectors especially if you plan to see 100% IDC on the stockers regularly.

 

I was thinking about our injectors today actually. If Stage 2 Sti's get away with running them, what kind of IDC's are they seeing? Any sort of increased failure rate on any engine components?

[LittleBlueGT]

I always thought that with the VF40-18g the injectors were more of a peace of mind thing. From what I've seen and heard the stock injectors should flow enough for 300whp +/- (where they are pretty much at their limit in most cases), and going with bigger injectors will drop IDCs from being so high, so you don't have to worry about it.

 

I can only get about 15 or 16 psi out of my stock injectors (at 6700 rpm or so), before I am consistently over 100%.

 

300 whp out of stock injectors would be on a generous dyno IMO. I can hit about 280 whp at 95% IDC. I am using PDX's mustang dyno as a reference. My road logging software is very close to their mustang numbers.

[LittleBlueGT]

I was thinking about our injectors today actually. If Stage 2 Sti's get away with running them, what kind of IDC's are they seeing? Any sort of increased failure rate on any engine components?

 

Todays modern fuel injectors are cooled by the fuel that they inject, running at 100% IDC should not overheat them. (unlike the old "rule of thumb" that says 85% IDC max which is more based on older injectors, but some doggedly stick to, even though there is no evidence to support this on our injectors) I have searched high and low to find any evidence of injector failures or uncontrolled fueling on stage2 STis, and found absolutely nothing.

 

That being said; if their is any reasonably possibility of your car overboosting, being driven at a lower altitude then it was tuned, seeing colder air then it was tuned for, etc..... and you are already pushing the edge, you are asking for trouble.

 

You also have to consider your fail-safe fuel map. If your ECU tuning switches to the fail-safe map at the same IAM as it turns off anything above WG boost, then that map is likely fine with stock injectors.............providing you are not running a WG actuator that is already running a strong spring.

 

ie: you have a WG actuator that is set at 17 psi. For some reason (bad gas maybe) your ECU switches to failsafe map, and essentially turns off the EBCS, now your IDCs are gonna go from 105% to 116% (assuming 10% richer AFR), that may pose a problem.

 

You have to consider all possibilities.

[ScoopMan]

Still wondering why most folks replace their pump before their injectors. Our pump is theoretically capable of supporting 645 cc/min injectors, while our injectors are 520, 550 or even 565 cc/min, depending what you read.

 

My feeble understanding of this is that our ecu is scaled to read our injectors as 520's when they are really 550's, which results in falsely higher IDC's. Someone who actually knows something, help...

[LittleBlueGT]

Still wondering why most folks replace their pump before their injectors. Our pump is theoretically capable of supporting 645 cc/min injectors, while our injectors are 520, 550 or even 565 cc/min, depending what you read.

 

My feeble understanding of this is that our ecu is scaled to read our injectors as 520's when they are really 550's, which results in falsely higher IDC's. Someone who actually knows something, help...

 

I don't know why either, Edmundu did some research about two years ago that indicates that our fuel pump is about 10l/hr higher then an STis. I ran 100% IDC on stock injectors and stock pump w/o any indication of a problem at all. I believe Edmundu also ran stock pump and stock injectors for a while w/o any problem on the part of the pump.

 

In fact seeing as our pump runs a loop to the front of the car (excess fuel gets returned) the pump is running at 100% at anything above medium throttle inputs. It is no harder on the pump at all.

 

I think it is because the old Jon at TDC said so, and everyone believed him.

 

Regardless of what size our injectors are the reported IDC is the IDC they are at. Nothing at all to do with size. I will explain on my next post why we can get above 100% IDC.

[ScoopMan]

Thanks LBGT. I have been reading all that stuff. My understanding is also that STI's run stage 2 with no fuel upgrades, while having a bigger turbo and a smaller fuel pump than we have. So we should be able to run a vf 39-30-34 with no fuel upgrades, right? Of course, I remember your 'convince me I need 740's' thread.

 

Please promise us you will not blow up your engine again anymore (even tho you are convinced it was for other reasons than injectors)

 

I am just trying to educate myself before I take my first baby steps. Especially since mine is my dd, no backup.

[BDII]

I can only get about 15 or 16 psi out of my stock injectors (at 6700 rpm or so), before I am consistently over 100%.

 

300 whp out of stock injectors would be on a generous dyno IMO. I can hit about 280 whp at 95% IDC. I am using PDX's mustang dyno as a reference. My road logging software is very close to their mustang numbers.

 

oh rly?

 

I make 306WHP on 80% IDC's.

[ScoopMan]

:spin:O no, not again

 

 

 

 

 

 

 

[BDII]

seriously....

 

Misinformation.

 

before you know it we're gonna have hundreds of members grenading their stock turbo's with TORCO and people upgrading to 850cc injectors for an 18g

 

YOU DO NOT NEED INJECTORS TO HIT 300WHP SAFELY.

 

Save your $400 and go buy an RBS lip from Rommel. That's what I did

[BDII]

Still wondering why most folks replace their pump before their injectors. Our pump is theoretically capable of supporting 645 cc/min injectors, while our injectors are 520, 550 or even 565 cc/min, depending what you read.

 

My feeble understanding of this is that our ecu is scaled to read our injectors as 520's when they are really 550's, which results in falsely higher IDC's. Someone who actually knows something, help...

 

 

2 total different jobs.

 

The pump just sends fuel from the tank to the lines. It's a basic pump without much room for improvement.

 

The injectors however have more wiggle room. They can be pushed farther the pump can.

[LittleBlueGT]

In all honesty BDII does not know exactly what he is talking about. Kinda, yes, .........exactly NO!

 

What do you mean by wiggle room?

 

I blew up my engine because I was running the wrong mixture of alky and my AFR went to almost 13:1. IDC was at 87% and would have been at that exact IDC whether or not I had the proper alky mix in or not.

 

306 whp on whose dyno? ah, a generous dyno.....whatever. On an 05-06 LGT (not the new block which has more efficient heads) you will not hit 300 whp on a mustang dyno unless you have above 94 octane gas, and run a 11.6:1 AFR or richer, or you have meth injection, or torco, etc. On some dynos yes.

 

FWIW on the dyno I used a VF40-18g only hit about 265 whp. I am not sure exactly what a VF40-18g can do, but I am pretty sure you can run stock fuel system just fine.

 

 

Let's move on.

 

 

To explain the IDC thing (yes I didn't know how it worked before, but I figured it out with some help from rao and MickeyD2005):

 

If your IDC is 100%, then your injectors are open 100% of the time.

 

Why then can we run 110% or more IDC and see more fuel going in?

 

Let's look at an example:

 

-6000 rpm means we have 20 ms of time to inject fuel (at 7000 rpm it is 17.14 ms)

-if our IPW (Injector Pulse Width) is 20 ms then our IDC is 100%

-the thing is our injectors have a latency value, time it takes for an injector to open or close (I am not sure if it is assumed that the injector takes the same time to close as open, but the concept is the same)

-if our injector takes 1.5 ms to open (this latency value will change depending on voltage injector receives) and 1.5 ms to close, that means that the injector can only be fully open for 17 ms if it is at 100% IDC, the injector is open 100% of the time, but not injecting 100% of the fuel it is capable of

-in the above scenario what happens when the ECU calls for above 100% IDC? I am not sure of the specifics of the calculations, but from what I understand the ECU will start to open the injector before it has closed from the last opening, it may be fully open for 18 or 19 ms, and still not be at max flow, but the injectors are never actually closing

-that is how we can end up at over 100% IDC

-there is no set amount over we can go, ie: 110% 120%, it depdns on what rpm, on the latency of the injectors, and the voltage

 

Does that make sense now?

[2005garnetGT]

running injectors static isn't the greatest idea

[ScoopMan]

So at 100% IDC, 3/4 of the time raw fuel is sprayed at the back of a closed intake valve? I am amazed it can get atomized.

[boostsr20]

running injectors static isn't the greatest idea

 

So actually is "static" by subaru ECU terms? 100% or 120%? Is it intentionally skewed by subaru as a safety net or is it really spraying fuel past the stroke?

 

BDII- Your the one spreading misinformation. Your 80% IDC's are on race gas targeting 12:1 A/F. 90% of the people won't ever target that high of an A/F. So stop making the blanket statement that the stock injectors are good to 300whp. We all know they are with METH or RACE GAS. If your going to mention that possibility at least mention how your numbers were obtained.

[LittleBlueGT]

So at 100% IDC, 3/4 of the time raw fuel is sprayed at the back of a closed intake valve? I am amazed it can get atomized.

 

Even 1000cc injectors running at 60% IDC are spraying on the back of a valve at times.

 

The air doesn't go in, the fuel doesn't either. Once the car is warmed up I am sure a hot valve helps with atomization.

[rc0032]

So the moral of the story is yes you need injectors

 

 

You people are hopeless and clueless

[LittleBlueGT]

So actually is "static" by subaru ECU terms? 100% or 120%? Is it intentionally skewed by subaru as a safety net or is it really spraying fuel past the stroke?

 

I don't think there is an official interpretation of it.

Anytime you are over 100% IDC the injectors are not fully closing, to me that is running static, even if there is more fuel to go.

 

running injectors static isn't the greatest idea

 

Likely not. I have done a bit of testing running mine up to 114% IDC and the fueling was very consistent, nothing to indicate "lack of control". I would never trust running that high personally, unless 114% was the worst case scenario.

 

By worst case scenario I mean:

-40F

-high baro pressure

-running at sea level

-going uphill in 5th gear WOT with a trailer behind

-the fuel targets were adjusted so that you had .3 or so AFR wiggle room.

 

I have thought about this too much!

[LittleBlueGT]

So the moral of the story is yes you need injectors

 

 

You people are hopeless and clueless

 

You are hopeless, give the man the info and let him decide.

 

Fact is STIs do it all day long, you show me them having problems running stage2. Then talk.

 

IME running alky is more dangerous then running injectors past 85% IDC. I have yet to find a scenario that would cause my small injectors to be the culprit for an engine failure, but it can happen with alky.

[BDII]

In all honesty BDII does not know exactly what he is talking about. Kinda, yes, .........exactly NO!

 

That's why my motor is still running strong I've given nothing bu straight forward answers, you on the other hand said that you need injector upgrades with the VF40/18g.

 

That sir, is 100% wrong.

What do you mean by wiggle room?

 

He obviously doesn't understand IDC's so why bother talking technicalities with him?

 

I blew up my engine because I was running the wrong mixture of alky and my AFR went to almost 13:1. IDC was at 87% and would have been at that exact IDC whether or not I had the proper alky mix in or not.

 

Yet i'm the idiot. 87% is not high. I call this one an Alky death

 

306 whp on whose dyno? ah, a generous dyno.....whatever. On an 05-06 LGT (not the new block which has more efficient heads) you will not hit 300 whp on a mustang dyno unless you have above 94 octane gas, and run a 11.6:1 AFR or richer, or you have meth injection, or torco, etc. On some dynos yes.

 

TDC's dyno which reads low, thank you:rolleyes: and yes it was on Torco.

 

FWIW on the dyno I used a VF40-18g only hit about 265 whp. I am not sure exactly what a VF40-18g can do, but I am pretty sure you can run stock fuel system just fine.

 

 

 

Then stay the **** out of the thread if you don't know what your talking about!!!

[BDII]

So actually is "static" by subaru ECU terms? 100% or 120%? Is it intentionally skewed by subaru as a safety net or is it really spraying fuel past the stroke?

 

BDII- Your the one spreading misinformation. Your 80% IDC's are on race gas targeting 12:1 A/F. 90% of the people won't ever target that high of an A/F. So stop making the blanket statement that the stock injectors are good to 300whp. We all know they are with METH or RACE GAS. If your going to mention that possibility at least mention how your numbers were obtained.

 

 

they are I hit 306 WHP on stock injectors with TORCO. Don't know how many times my dyno chart's been posted, or how many times i've mentioned it...

 

how is that misinformation? The guy wanted to know if he needed injectors for the VF40/18g. LBGT said yes becuase your IDC's woud be too high, I responded with my IDC # and WHP #.

 

You act as though TORCO is a once in a while thing. you can run it all day long and make 300+whp ALL DAY LONG.

 

Several members do

 

and as far as your comment about the IDC's.... no shit, sherlock.

 

 

A blanket statement would be saying that you need injectors with every turbo upgrade.

[rc0032]

Let me start with I know im a Dick

 

You are hopeless, give the man the info and let him decide.

He shouldn't his tuner should and this board is full of people that dont know shit.

Fact is STIs do it all day long, you show me them having problems running stage2. Then talk.

Who cares if STi's run high IDC its a bad idea

IME running alky is more dangerous then running injectors past 85% IDC. I have yet to find a scenario that would cause my small injectors to be the culprit for an engine failure, but it can happen with alky.

What motor are you on again?

 

You should NEVER be giving people fule advice. You are compensation for your lack of injectors with alky. And when you alky failed your motor blew.

 

 

To the OP ask your tuner

[BDII]

Let me start with I know im a Dick

 

I still you

 

 

 

 

 

To the OP ask your tuner

 

Why? there are soooooo many experts here