Injector Sizes versus power

[Bass Junky]

Hey guys.

I'm looking at new injectors soon and I had a hunt for a bit of a power/injector sizes thread but couldn't find one.

I'm not exactly sure how to do the workings out so I thought I might ask somebody to put together a little table.

Criteria:

powers of say 200, 220, 240, 260, 280, 300, and so on up to say 500 rwkW

Injector sizes to suit.

I guess you could have the graph in both stock fuel pressure and a resonably raised fuel raril pressure.

Injector duty should not exceed 90% for safety.

So, who can do the math?

BASS OUT

[Steve]

http://www.rceng.com/technical.htm#WORKSHEET

how about you do the math

[Bass Junky]

Cool.

I will do.

550 cc injectors, is that rated at 550cc per minute/hour what?

550 horsepower I got 8cc per minute. is that about right? makes 480 cc per hour.

[midnight]

lol its cc per minute

somethings wrong with ur calculations methinks

[Bass Junky]

Have a look at the link, tell me where I'm going wrong, because it did sound a little strange.

What is the Standard Fuel rail pressure of a Skyline, and what is a resonable pressure for raising too to keep safe on all types of injectors?

[Bass Junky]

Steve.

Using that calculator, I use the following figures

Desired Horsepower = 422

Number of Injectors = 6

Brake Specific = 0.65

Max Injector Duty = 0.90

System Fuel Pressure = 40 psi

I get 557 cc per minute for like 200 rwkW (460 hp at fly)......

Is this right, doesn't sound it.

Please explain where I'm going wrong.

[Steve]

try using 0.60 BSFC, also fuel pressure you are showing is a bit low.

Base pressure at atmo for nissan OEM regulators is 3.05kg, if you are running 1 bar boost to achieve 422hp, the pressure will then be 4.05kg, or (multiply 14.5 x 4.05) 58.7psi = 427cc injectors required.

If you were using 1.4 bar boost, 63.8psi - 409cc injectors required.

There is also a calculation on that site to work out extra fuel flow for given injectors when you change the rail pressure.

btw, for a 6 cyl turbo engine, the 'approx' rule of thumb is what ever the bhp you are after, get the same size in injectors

[Bass Junky]

So it's a little harder than just a straight chart.

Boost pressure and the like also comes in.

Bugger.

[Steve]

Oh, and be aware that different injectors are rated at different pressures, SARD and HKS rate their injectors at 3kg (at idle) vs stock 2.55kg at idle.

Also, Sard and more so HKS seem to under rate their injectors that I have seen.

I was putting down 320+rwkw with sard 550cc injectors with OEM fpr, and never saw 80% duty cycle - this was running around 1.4 bar boost. Sard rate their 550cc injectors at 510cc with oem fuel pressure.

[Steve]

if you want rough figures, just use the bhp approx equals injector cc theory and you should be right.

400bhp = 400cc

550bhp = 550cc

etc

[Abo Bob]

I have found my Nismo 480cc injectors don't flow the full 480cc at stock pressure and I've heard this from someone else too.

[Steve]

What did they flow? do you know what pressure they were tested at?

[R31Nismoid]

Pete, just stick 740cc Nismo's in there.

The PowerFC controlls them fine and you'll have no issues.

I certainly have not.

$900-$950 from nengun

[Richard Bell]

Nismo only do 480cc direct fit for the Neo though!

[Bullant47]

Nismo only do 480cc direct fit for the Neo though!

I was under the impression tha Nismo, HKS and others (not Sard or PE) were made by Denso in Japan...Am I wrong?

[Bass Junky]

Yeah, I'm going to put in either some 550s or 720s but I'm just curios about how all the calcs work.

[R31Nismoid]

fark the calc

just get 7xxcc and plug it in baby

[lwells]

if you want rough figures, just use the bhp approx equals injector cc theory and you should be right.

400bhp = 400cc

550bhp = 550cc  

etc

Then times by 0.85 (i.e. for 85% max injector rate).

Lucien.

[Steve]

I was under the impression tha Nismo, HKS and others (not Sard or PE) were made by Denso in Japan...Am I wrong?

My sards are made by denso, I was under the impression that they made most, if not all injectors in Japan.

Just like NGK make all their iridium plugs - greddy, hks, nismo etc

[Bass Junky]

yeah, but people only have one size for the R34 GTT. That's 480cc