Jump to content
SAU Community

Recommended Posts

im in the same position as most of you with pushing the injectors to their limits but for now im just winding the boost down 1 psi and wait for the 600cc injectors and f/pump when i get some more cash then = high psi :D

  • Replies 45
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

I'd do what your tuner is comfortable with doing. Heaps of people on the forums have made substantially more power than 225 rwkw on stock fuel injectors with a bit more rail pressure.

There's no problem bumping the rail pressure up a bit etc (it is suspected that s15s run higher pressure) than our cars. That's why the injectors flow 440 cc on r33s, but 480 on s15s.

I just wouldn't go running a million psi that's all.

  • 5 months later...
I'd do what your tuner is comfortable with doing. Heaps of people on the forums have made substantially more power than 225 rwkw on stock fuel injectors with a bit more rail pressure.

There's no problem bumping the rail pressure up a bit etc (it is suspected that s15s run higher pressure) than our cars. That's why the injectors flow 440 cc on r33s, but 480 on s15s.

I just wouldn't go running a million psi that's all.

I am making 270 rwkw with stock injectors and stock fuel pressure (and reg.) with no knock issues at all.

I do have very bad fuel economy though, could the stock injectors be contributing to this at all?

Cheers

I'd do what your tuner is comfortable with doing. Heaps of people on the forums have made substantially more power than 225 rwkw on stock fuel injectors with a bit more rail pressure.

There's no problem bumping the rail pressure up a bit etc (it is suspected that s15s run higher pressure) than our cars. That's why the injectors flow 440 cc on r33s, but 480 on s15s.

I just wouldn't go running a million psi that's all.

that's a fine theory except that 33 GTST don't have anywhere even near 440cc let alone 480cc injectors. they are 370cc...

This is not possible unless your fuel pressure reg is busted allowing huge line pressure or you have aftermarket injectors and don't know about it or the dyno setttings have been tweaked :(

Stock injectors and same figures on two different dynos (one being the PAC racing dyno)...

FPR may be busted? Would this be giving me bad fuel economy?

You guys can all laugh, but there IS a definite relationship.

Basically 6cc per minute per flywheel horsepower is a very close approximation of fuel flow at optimum air fuel ratio.

As you have six cylinders, and six injectors, that means max flywheel horsepower = Injector flow at 100 percent duty cycle.

So basically 550cc injectors would equal 550 flywheel horsepower absolutely flat out at full maximum duty cycle. But that is not real smart. You might want to limit it to 80% duty cycle maybe ? Which would be only 440 flywheel Hp.

But then there are drive train losses, typically only 85% of flywheel power makes it to the rear, so that comes to 374 Hp. Converted to Kw that is 275 RWKw.

Depending on the injectors you run, and assuming the fuel pump is up to the job you CAN figure out a reasonable RWKw versus injector size.

So absolutely balls to the wall with no margin might be injector size in cc x 0.85 x 0.746 = RWKw

Something safer and more reasonable might be injector size in cc x 0.8 x 0.85 x 0.746 = RWKw

yes, but that's a relationship between injector size and horsepower, not injector duty cycle and horsepower. duty cycle doesn't tell you anything except for how long in 1 cycle the injector is open for. I can have an injector duty cycle of 80% by I'll be getting very different amounts of fuel between a 300cc injector and an 800cc injector...

I am making 270 rwkw with stock injectors and stock fuel pressure (and reg.) with no knock issues at all.

I do have very bad fuel economy though, could the stock injectors be contributing to this at all?

Cheers

HAHHAHAHA what dyno....... i want to put mine on and im sure it will run 500rwkw if you ran 270rwkw.

HAHHAHAHA what dyno....... i want to put mine on and im sure it will run 500rwkw if you ran 270rwkw.

I told you what dyno. PAC racings dynapack hub dyno and also a dynodynamics roller dyno. Have you heard of the PAC boys before?

Well done if you have 500 rwkw, nice power.. I know its making 270rwkw, I am sure that the three tuners and two dynos I have used would not be out.

post-24130-1185956515_thumb.jpg

What ecu are you running?

Those out there who have fiddled with batch injection. Is it possible to get close to that figure with batch fire?

i.e 2 injector pulses per cycle vs the 1 pulse (sequential) the std ecu and pfc uses.

(remembers back to the 533rwhp on stock injectors thread) :huh:

What ecu are you running?

Those out there who have fiddled with batch injection. Is it possible to get close to that figure with batch fire?

i.e 2 injector pulses per cycle vs the 1 pulse (sequential) the std ecu and pfc uses.

(remembers back to the 533rwhp on stock injectors thread) >_<

just the PFC. I have many people that can verify that its making the power I said and I know that injectors and FPR are standard, only fuel upgrade has been a bigger fuel pump.

ok.

Well as you can understand its definitely not possible to run such figures with stock fuel pressure and injectors.

Have a look at the std fpr and tell me if it looks as if some one has smacked its top in a tad. Its a crude method of upping fuel pressure.

Whats your tuner think is going on? He would obviously have some idea as the base map would be way off the mark if it were running higher fuel pressure and or highflowed injectors.

just the PFC. I have many people that can verify that its making the power I said and I know that injectors and FPR are standard, only fuel upgrade has been a bigger fuel pump.

Bet you have a blockage in the return line and or the pump they are using is massive ie too much flow for the standard reg to flow so you have higher pressure at lower duty cycles as the fuel is not being consumed. This would explain both the shite economy and the large power figure.

*DISCLAIMER*

The below is a loose quote of a conversation between a well-known "old school" Brisbane tuner & myself not long after I bought my GTR. I myself have not confirmed what he said to me & will therefore recommend you do your own research BEFORE attempting this at home.

This guy was involved with the build of my engine & was adamant that std Nissan injectors were considerably under-rated from the factory & I should have no problems flowing enough fuel to create 600bhp considering the hardware already attached. What rail pressure was required to do this was not discussed, but it would have to be a fair chunk higher than std which in itself is not really a good idea. Under bonnet fires fed by leaking fuel delivery systems get real nasty REAL fast......

I do intend to actually test the flow-rates of assorted std injectors vs rail pressure simply to answer the Q of whether this is in fact attainable but only in a test rig & even if it is doable, bigger injectors & lower psi is always going to be safer than smaller injectors & huge psi.

Food for thought.........

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • @Haggerty you still haven't answered my question.  Many things you are saying do not make sense for someone who can tune, yet I would not expect someone who cannot tune to be playing with the things in the ECU that you are.  This process would be a lot quicker to figure out if we can remove user error from the equation. 
    • If as it's stalling, the fuel pressure rises, it's saying there's less vacuum in the intake manifold. This is pretty typical of an engine that is slowing down.   While typically is agree it sounds fuel related, it really sounds fuel/air mixture related. Since the whole system has been refurbished, including injectors, pump, etc, it's likely we've altered how well the system is delivering fuel. If someone before you has messed with the IACV because it needed fiddling with as the fuel system was dieing out, we need to readjust it back. Getting things back to factory spec everywhere, is what's going to help the entire system. So if it idles at 400rpm with no IACV, that needs raising. Getting factory air flow back to normal will help us get everything back in spec, and likely help chase down any other issues. Back on IACV, if the base idle (no IACV plugged in) is too far out, it's a lot harder for the ECU to control idle. The IACV duty cycle causes non linear variations in reality. When I've tuned the idle valves in the past, you need to keep it in a relatively narrow window on aftermarket ecus to stop them doing wild dances. It also means if your base idle is too low, the valve needs to open too much, and then the smallest % change ends up being a huge variation.
    • I guess one thing that might be wrong is the manifold pressure.  It is a constant -5.9 and never moves even under 100% throttle and load.  I would expect it to atleast go to 0 correct?  It's doing this with the OEM MAP as well as the ECU vacuum sensor. When trying to tune the base map under load the crosshairs only climb vertically with RPM, but always in the -5.9 column.
    • AHHHH gotchaa, I'll do that once I am home again. I tried doing the harness with the multimeter but it seems the car needed a jump, there was no power when it was in the "ON" position. Not sure if I should use car battery jump starter or if its because the stuff that has been disconnect the car just does send power.
    • As far as I can tell I have everything properly set in the Haltech software for engine size, injector data, all sensors seem to be reporting proper numbers.  If I change any injector details it doesnt run right.    Changing the base map is having the biggest change in response, im not sure how people are saying it doesnt really matter.  I'm guessing under normal conditions the ECU is able to self adjust and keep everything smooth.   Right now my best performance is happening by lowering the base map just enough to where the ECU us doing short term cut of about 45% to reach the target Lambda of 14.7.  That way when I start putting load on it still has high enough fuel map to not be so lean.  After 2500 rpm I raised the base map to what would be really rich at no load, but still helps with the lean spots on load.  I figure I don't have much reason to be above 2500rpm with no load.  When watching other videos it seems their target is reached much faster than mine.  Mine takes forever to adjust and reach the target. My next few days will be spent making sure timing is good, it was running fine before doing the ECU and DBW swap, but want to verify.  I'll also probably swap in the new injectors I bought as well as a walbro 255 pump.  
×
×
  • Create New...