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??

 

[JusMX141]

What purpose will the AFC2 serve? It's main function is to tune for larger injectors.

 

[JFatch1890]

well, the question of whats the max boost on stock injectors is a good question

 

[JoEgsX90]

its purpose is to run the safc2 on these injectors untill i get bigger ones.....Why would you be able to tune my 190 pump with my stock injectors with my safc

 

[DSM1G90]

Factory boost was up to 14lbs/sq/in max using 450's with a 14B turbo. Obviously, with a larger turbo, there could be some more added head room for boost until you get the larger injectors. After that, you're on the road to major power which even the 14B turbo can easily muster over 300hp with much larger injectors.

 

[JusMX141]

I'll ask again, what are you tuning with the AFC if you're using stock injectors? By having a pump that flows more than stock you're simply increasing the volume of fuel available for the injectors to use....otherwise it will make no noticeable change in the car's performance. The ECU's stock fuel curve controls 450's just fine.

If you do install the AFC, leave the thing zero'd out unless you have a logger or some way to monitor what's going on....and even with a logger you can't monitor injector duty on a 2G, so you'll still have no idea when you're overrunning your 450's.

I'll say a safe boost level for 450's on a 16G is 12psi.

 

[1qkfwd]

Its not really the amount of boost you should be worrying about. It should be how much HP those injectors are good for. On my mild setup I have pushed 23Lbs through them. With the car making an estimate HP from here Simple Horsepower Calculator I am making 240hp-233hp and the injectors are anywhere between 76-78% duty cycle as per pocketlogger.

 

[JoEgsX90]

Yea well im going to leave it zeroed out untill i get my 660's or 550's. Im going to use a digital A/F gauge tapped into the 02 sensor to monitor the ratio. If you guys get a chance look at my setup and let me know wuts thje best injecitors to run. Running this as a daily driver also. untill it breaks down time to time..

 

[1qkfwd]

You will have beter luck with the 550cc. If you go with the 650s or bigger you will run into more problems tuning because you will have to lean it out more than the 550s and that will cause the ECU to run more timing.

 

[JoEgsX90]

Ok well what about the evo's injectors i think there 560's would that be good??

 

[JusMX141]

Excellent choice. You can normally find them at a reasonable price from Evo owners who are upgrading.

 

[boostzilla]

I just recently bought a 98 tsi and the guy who had it before me put on a EVO III 16g turbo...i have the biggest feeling the car had way to much boost. I tried turning it down but it seems like it hasnt done squat. Every time i get on it anything over 4000 rpm the car bogs out. i have a feeling its not gettin enough fuel...it has a 255 fuel pump but stock injectors and stock internals. how much boost can i run on the stuck injectors?

 

[kevingst]

On the 95 gst I had, with a 14b and safc2, I ran 18psi with no issues. At 20psi on cold days I'd get massive fuel cut. Ran it like this for at least a year with no apparent problems, but back then I had nothing to log with... so who knows what was really going on.

 

[JusMX141]

On the 95 gst I had, with a 14b and safc2, I ran 18psi with no issues. At 20psi on cold days I'd get massive fuel cut. Ran it like this for at least a year with no apparent problems, but back then I had nothing to log with... so who knows what was really going on.

Ummmm, that was your car's friendly way of telling you it was too lean...sort-of like when your dog starts with dry heaves shortly before it hurls a pile of Kibbles N' Bits on your kitchen floor. You simply avoided cleaning up a huge mess.

 

[z24frank]

So whats the answer to his question minus the afc part?

 

[cheap90gsx]

isn't the recommended max. 16 psi for 450's.

 

[airmail96]

Right around there, more then that and you risk killing the injectors due to having them maxed out all the time (if your flooring it that is)

 

[RayBan GST]

15 PSI is THE MAX on the stock injectors ( do not even think about going beyond this number) 15 PSI is the limit of the 450 injectors or u will hit a fuel cut and u know how nasty is a fuel cut



change them to EVo injectors 550 or a bit bigger and u can reach up to 20 psi with no issues if u have the supporting mods

good luck

 

[habitatguy187]

15 PSI is THE MAX on the stock injectors ( do not even think about going beyond this number) 15 PSI is the limit of the 450 injectors or u will hit a fuel cut and u know how nasty is a fuel cut QUOTE]

This isn't necessarily true. The ecu is what causes fuel cut and that happens at 16psi, but you're right, the reason is because it predicts the injectors to be at 100% duty cycle. But as noted above, many people have ran a higher psi on them, I read that someone did a test and just by upgrading their fuel lines the injectors flowed like 15% better. Not sure how that works but that's what it said.

 

[habitatguy187]

Here's the post I was talking about, it's under an ebay fmic thread.

Bryan Wheat - "I have used a couple ebay intercoolers, the onle one that i have experienced with alot of power is my friends (i do all the work on his car, he is loaded) 92 tsi fwd with a 60 trim t-4. We were running 25 psi on 450's, i repeat 450's, walbro 255, afpr, full 3 inch exhaust, no cat, 2.5 inch intercooler tubing, the intercooler is 3x12x20 or something close to that. We got the boost set at a constant 25 psi running the injectors under 90% with absolutly no knock whatsoever. Just zeroed out the maft and adjusted the idt, base and idle trims, and left the mid and wot alone. No knock, still running rich untill 4th gear it starts overrunning the injectors. He needs to buy some 720's i tell him, (the car is not driven very often) but i would say that this is a pretty good proof that the ebay intercoolers are pretty god shit. I think that 450's have a little more potential in them than everyone gives them credit for. I think that stock fuel system (lines, filter banjo bolt) is very very restrictive, i once read of a group of guys flow benching a stock fuel pump with -8an braided steel line, and it was outflowing a walbro 190 with the stock lines. That to me is pretty good evedence that just a fuel pump upgrade is not good enough, that you should be able to get more fuel to the injectors and run a lower duty cycle and run the 450's for more power.

 

[1qkfwd]

I can't find the link anymore but I have the paper in front of me. The 450CC injector was good for 275HP @ 80% duty cycle and 342hp @ 100% duty cycle. So you can make that power with 10lbs of boost or 25lbs. I have ran my 16G up to 23-24lbs on my 450's and it was under the 100% mark. There is no set boost limit for a set of injectors.


Oh and the 560s are a great cheap upgrade for our cars I have ran those before. You should be good with those for what the 16G will make for power.

 

[turbo90gsx]

Just for somthing to compare to. I have a re-wired stock fuel pump and thats it and at 14-15 psi with the 14b I'm at 90% duty cycle. I would not run 450's past the 90% cycle unless your using race gas and have a 1:1 regulator.

 

[kevingst]

Ummmm, that was your car's friendly way of telling you it was too lean...sort-of like when your dog starts with dry heaves shortly before it hurls a pile of Kibbles N' Bits on your kitchen floor. You simply avoided cleaning up a huge mess.

First, let me clear something up... I ran it at 18psi with no problems for over a year... not at the 20psi. Also, that was on a rewired 190 with 93 octane.

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.

 

[habitatguy187]

Vfaq says that the stock injectors are maxed out at 18-20psi. This is with 93 octane. If you're running lower then it says that you'll need 550s. THERE! Your question is answered .

 

[the_mork]

275HP @ 80% duty cycle and 342hp @ 100% duty cycle. So you can make that power with 10lbs of boost or 25lbs. I have ran my 16G up to 23-24lbs on my 450's and it was under the 100% mark. There is no set boost limit for a set of injectors

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, VE, 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, this is why you read my whole post isn't it?