Fuel Injector Duty Cycle Vs Rwkw?

[R33GOD]

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

[MANWHORE]

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.

[Trooper]

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

[benl1981]

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

[Beer Baron]

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...

[Trooper]

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?

[Warpspeed]

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

[Beer Baron]

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...

[1400r]

think he was talking about s15 injectors in a 25 mate

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

[STATUS]

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.

[Trooper]

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.

[Cubes]

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)

[fEkuaR]

So really what everyone is saying is you dun want to see this....oh 11psi and yes it's tuned

p.s. new fuel system is on it way

who the hell tuned that? 50+knock and 100% duty cycle...

[Trooper]

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.

[Cubes]

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.

[zertek]

270rwkw with stock injectors!!!?!?!? whaaaaaaaaaaaat

[rob82]

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.

[Lunatikk]

*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.........

[Cubes]

From memory.

GTR injectors.

36psi - 440cc

40psi - 480cc

46psi - 520cc

I may have the fuel pressure's off a little.

My own flowed 480cc at 40psi I know that for sure.

[Brockas]

511rwhp on stock injectors.

it's all about the batch fire....