How Do 550cc Injectors Make 300rwkw On An Rb25det?

[Harey]

can anyone answer where base pressue is measured from... idle? of 0 manifold pressure

My car at idle is 2kg/cm2 fuel pressure... at 0 on the boost gauge... around 2.4kg/cm2

Seems abit off 3 bar?

No we are talking about fuel pressure here. You are talking about air pressure. Base fuel pressure is measured at zero vacuum (0 on your boost guage, can be tested by disconnecting a vacuum hose).

[Harey]

Using 555cc injectors, my car makes 250 rwkw at 72% inj duty.

Here is a great example, another 8% of injector duty comes up to 270rwkw. Still a lot short of 300rwkw and especially 340rwkw as you mentioned R31Nismoid.

[Harey]

My 550's are hiting 85% duty and making 340rwhp... however, the current tune is apparently somewhere around 10:1 af's

That equates to 261rwkw. Yes there is more to gain from raising the afrs up to 12 but I doubt it would get to 300rwkw, plus the injectors are already running at 85% duty cycle.

[Harey]

The facts.

1. 550's will support 300rwkw.

2. Factory reg is all you need.

If these "sites" say you can only get 250rwkw from 550's... then how is it possible that with 370cc injectors people are making 200-220rwkw???

*think for a second*

Exactly, it wouldn't be possible. To back this up look @ the RB25 dyno results thread every single car with a factory turbo making 190-200rwkw is using factory injectors.

Whatever site you are getting your calc's from - are wrong. OR you are inputting information wrong.

We are the people here that have experience and knowledge of this specific application. Not some "cater for all" website calcuator without any idea.

Injector calcuators are the same as ET/Drag calculators, most of them are absolute rubbish.

Great to hear, this is what I want to hear.

I didnt know the size of standard injectors, thanks for that. Mine makes 190rwkw on standard injectors

I am trying to call on your experience and knowledge to better understand this. There just seems to be a wide range of power figures being tossed around on here, from 260rwkw to 340rwkw. I thought the idea was to share information to make sure people do things once and do it right.

Unfortunately on the neo engine the injector range is quite limited so I dont have the luxury of just getting oversized injectors and being done with it. Also, I would love the option to have some space to run E85 one day.

[nizmokid]

555 nismo injectors on my car with standard reg and i made 301rwkw ......have tweeked the boost a little now to make the standard bottom end last and the car is now pushing out 270rwkw.....plenty for the street.

[Granthem]

No we are talking about fuel pressure here. You are talking about air pressure. Base fuel pressure is measured at zero vacuum (0 on your boost guage, can be tested by disconnecting a vacuum hose).

No im talking about fuel pressure... of my fuel pressure gauge Its measured in kg/cm2 of whatever is is, pretty much BAR.

[Harey]

No im talking about fuel pressure... of my fuel pressure gauge Its measured in kg/cm2 of whatever is is, pretty much BAR.

Hahaha no prob, I thought you were saying why is my car not boosting to 3 bar hahaha

[Harey]

555 nismo injectors on my car with standard reg and i made 301rwkw ......have tweeked the boost a little now to make the standard bottom end last and the car is now pushing out 270rwkw.....plenty for the street.

Thanks for the info! Any idea what duty cycle they were running at on the two different power levels?

[Granthem]

Hahaha no prob, I thought you were saying why is my car not boosting to 3 bar hahaha

Haha no spikes to 1.3 bar are enough for me thanks! (boost that is)

[Duncan]

mine makes over 300 (just) on 550s.

[joeyjoejoejuniorshabadoo]

oh for fucks sake....

my car makes 285 rwkw on pulp and 323rwkw on e85 (which requires 30% MORE fuel than 98)

I run nismo 555cc injectors, STOCK NISSAN fpr and a nismo intank pump. that is all

duty cycles are perfectly fine.

bombtrack's car is the same, as with MANY MANY MANY others on here...

go look at the rb25 dyno results thread that is stickied at the top

nismoid IS correct on this

[paulr33]

550cc's x 6 to make 300rwkw is a piece of piss

i think from memory some magic guy in perth made 300rwkw on stock 370cc injectors with a mega FPR hack, but then it blew up hahah

550cc's is plenty of headroom

[rob82]

Change you cals by using a BSFC = 0.54 for pump 98Oct and BSFC=0.6 for E85 - this is closer to the money for most 4vavle RB's. BSFC=0.6 on pump98 is like V6 two valve donkey motor efficiency!!!

[mattymagoo22]

Even if duty cycle is at 99% it still has time to turn off and on again so there shouldn't be a problem(correct me if you think i'm wrong) more than that its time for an upgrade, FPR's are band-aids in my opinion. People getting 300rwkw out of standard injectors though, then blowing them up after 500 ks of driving makes me laugh! Just like saying you had sex with Miranda Kerr, only you blew after you put it in! You're going to leave that out of the story when you tell your friends huh!

How do you guys figure that 38psi of fuel pressure + 20psi boost = 58psi total fuel pressure? Your turbo doesn't pressurise your fuel lines. In most cases the max fuel pressure is 40psi thats with the reg at atmospheric pressure.

[MBS206]

Even if duty cycle is at 99% it still has time to turn off and on again so there shouldn't be a problem(correct me if you think i'm wrong) more than that its time for an upgrade, FPR's are band-aids in my opinion. People getting 300rwkw out of standard injectors though, then blowing them up after 500 ks of driving makes me laugh! Just like saying you had sex with Miranda Kerr, only you blew after you put it in! You're going to leave that out of the story when you tell your friends huh!

How do you guys figure that 38psi of fuel pressure + 20psi boost = 58psi total fuel pressure? Your turbo doesn't pressurise your fuel lines. In most cases the max fuel pressure is 40psi thats with the reg at atmospheric pressure.

1:1 rising rate fuel reg.

As they see boost on that small air pressure line, it starts equally increasing fuel pressure.

This is done for the same reason the line is there on NA cars, so that no matter what air pressure you're tuning at, the differential pressure from injector to motor is the same.

Hence, at 20PSi of boost, with base pressure of 38PSi, you're seeing 58PSi total boost pressure in the rail, but on a 38PSi differential from injector to motor.

[JonnoHR31]

actually it does. the vac line from the manifold to the reg keeps fuel pressure at ~40psi ABOVE manifold pressure. therefore its lower under vacuum and higher under boost. as said this is to achieve an even flow rate regardless of boost/vac

how much power you can get out of injectors also depends on how well your motor makes power. if you have a big exhaust restriction and your unable to run much timing under load then your not going to make much power relative to the amount of air and fuel your using. i have 555s running at over 80% for a 12:1 afr and i was making 250rwkw on 98 when ideally 80% would mean over 300rwkw.

[saliya]

Even if duty cycle is at 99% it still has time to turn off and on again so there shouldn't be a problem(correct me if you think i'm wrong) more than that its time for an upgrade, FPR's are band-aids in my opinion. People getting 300rwkw out of standard injectors though, then blowing them up after 500 ks of driving makes me laugh! Just like saying you had sex with Miranda Kerr, only you blew after you put it in! You're going to leave that out of the story when you tell your friends huh!

How do you guys figure that 38psi of fuel pressure + 20psi boost = 58psi total fuel pressure? Your turbo doesn't pressurise your fuel lines. In most cases the max fuel pressure is 40psi thats with the reg at atmospheric pressure.

Hey,

Stock, the Nissan turbo regulator applies a 1:1 change in fuel pressure along with manifold pressure.

Fuel pressure is negated by boost so the net effect is 43psi of fuel pressure regardless of boost/vac.

Some example figures (sorry about underscores):

base___manifold__fuel____net fuel___when

43psi__-7psi_____36psi___43psi_____idle (i.e. manifold vacuum)

43psi___0psi_____43psi___43psi_____no boost, no vac

43psi___20psi____63psi___43psi_____20psi boost

A rising-rate regulator does a different thing - changes fuel pressure by some multiplier other than 1 along with boost; both the rate and the threshold "it starts working at" may be adjustable.

Corky Bell claims to have brought the "original" rising-rate regulator to the market according to Corky's comments on FPR

Some of his regulators are designed to workalongside the existing regulator, some replace it completely.

For example, the rate might be set to 2:1 and the threshold, 0psi of boost. Then we have some example figures:

base___manifold__fuel____net fuel___when

43psi___-7psi____36psi___43psi____ idle (manifold vac, no regulator action)

43psi____0psi____43psi___43psi____no boost, no regulator action

43psi____1psi____45psi___44psi____1psi boost, +2psi fuel pressure, +1psi net extra fuel pressure

43psi____20psi___83psi___63psi____20psi boost, +40psi fuel pressure, +20psi extra fuel pressure

Cheers,

Saliya

[Harey]

Change you cals by using a BSFC = 0.54 for pump 98Oct and BSFC=0.6 for E85 - this is closer to the money for most 4vavle RB's. BSFC=0.6 on pump98 is like V6 two valve donkey motor efficiency!!!

And we have a winner! This is the answer to the thread!! Thanks Rob82!

[Harey]

Even if duty cycle is at 99% it still has time to turn off and on again so there shouldn't be a problem(correct me if you think i'm wrong) more than that its time for an upgrade, FPR's are band-aids in my opinion. People getting 300rwkw out of standard injectors though, then blowing them up after 500 ks of driving makes me laugh! Just like saying you had sex with Miranda Kerr, only you blew after you put it in! You're going to leave that out of the story when you tell your friends huh!

How do you guys figure that 38psi of fuel pressure + 20psi boost = 58psi total fuel pressure? Your turbo doesn't pressurise your fuel lines. In most cases the max fuel pressure is 40psi thats with the reg at atmospheric pressure.

Mate I think you should go have a read on how fuel systems work before you hand out advice. 80% duty cycle is preferred and its well documented why, fuel pressure regs do increase/decrease fuel pressure depending on the vacuum/boost in the manifold.

[paulr33]

are you here to challenge every response you get?

it seems you already know the answer - whats the point?

500cc's are fine 300rwkw

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