injector flow CALCULATION

[CEF11E]

I am going to get my ECU rechipped again and i need a little help to make sure i am not going to run 100% duty cycle.

I am running a set of denso 270cc injectors(stk rb20) they have been rebuilt i will be installing them like:

cyl1-270

cyl2-270

cyl3-272

cyl4-272

cyl5-276

cly6-276

keeping cyl 5 and 6 richer for safety.

car and engine specs are

rb20det 100.000ks

rb25 hi flowed and has produced 226rwkw @ 1bar on rb22 hybrid engine

walbro 255lt fuel pump

turbo back 3" with almost no bends and the biggest hi flo cat possible

GTR sized FMIC with waterspray kit on 5psi hobbs switch

oil catch can

EBC single stage

standard AFM

the car will be tuned with a professional wide band air/fuel meter that logs data. and cross referenced on the dyno. it will be tuned for 98ron.

what is the safest/best performance a/f ratio?

how many rwkw can i expect while keeping a safe duty cycle?

what is the theoretical hp per injector rating?

I want to do this properly and do not want a dodgy half assed tune that will lean out and go bang!

[Sydneykid]

In a 6 cylinder, 270 cc's = 270 bhp

Divided by 1.34 to get KW= 202 kw

Take away 50 kw for losses = 152 rwkw

Around 12 on the A/F ratio

That's about it.

[CEF11E]

In a 6 cylinder, 270 cc's = 270 bhp

Divided by 1.34 to get KW= 202 kw

Take away 50 kw for losses = 152 rwkw

Around 12 on the A/F ratio

That's about it.

ok now i am scared... my last dyno produced 215rwhp with current tune.

but since then i have added

FMIC

dump pipe

hi flowed turbo

and my a/f is around 12.

does this mean i am already running 100%?

I was under the impression i could get close to 200rwkw from these injectors going from a lot of the posts on the internet and these forums,

however i take your opinion as i know you have experience...

so no point having my ECU tuned again?

[Evo_Lee]

You won't get 200rwkw...my calculations aren't too far from SK's calculations.

Given you run close to 90% duty = 291.6ps = 214kw, minus drivetrain loss = 164.4rwkw.

[blind_elk]

You can get a bit of leeway on the duty cycle by increasing the fuel pressure behind the injector, up to around 4 bar (58psi). Use something like a Malpasssi adjustable FPR to achieve this.

The flow , therefore hp, will be modified by SQRT(New Pressure / Current Pressure)

[CEF11E]

how come there are so many rb20s doing this with stock injectors, are they all going to go bang?

"quote"

I made 200rwkw (268rwhp) with the stock injectors and 0.9bar boost, so talking to Shaun at Boostworx, who will be tuning it, he reckons around 18psi or there abouts should see if make some really good power, and there is no reason why is shouldn't be able to run this boost, as the RB20 has lowish comp. ratio and it has a nice fuel setup now, so all the key factors are there to produce good power

"end quote"

[Sydneykid]

how come there are so many rb20s doing this with stock injectors, are they all going to go bang?

"quote"

I made 200rwkw (268rwhp) with the stock injectors and 0.9bar boost, so talking to Shaun at Boostworx, who will be tuning it, he reckons around 18psi or there abouts should see if make some really good power, and there is no reason why is shouldn't be able to run this boost, as the RB20 has lowish comp. ratio and it has a nice fuel setup now, so all the key factors are there to produce good power

"end quote"

No Problem with the 18psi, RB20DET will handle that easily as long as the tuning is good, of course.

I have yet to see an RB20DET make 200 rwkw on standard injectors. I have a Nismo adjustable fuel pressure regulator and a GTR pump on ours and the best I could get out of the standard injectors was 180 rwkw and it was at 100% duty cycle over 7,000 rpm. It has a set of S5RX7T 550cc's in it now and it has more than enough fuel for 225 rwkw.

RB25DET's have 340 cc injectors and they run out of flow at ~210 rwkw. Some people think RB20's can do the same, but forget that you have to rev them higher to make the same power so there is less time for the injectors to be open.

The most common upgrade for RB20's are the 444 cc GTR injectors, with the GTR resistor pack to match the impedance, they are a good choice at realtively low cost as there are many around.

[CEF11E]

thanks heaps for the reply i apperciate the advice...

[SeriesIIGTST]

Hijacking thread but still on injectors...

Sydneykid - had my RB25DET dyno'd yesterday and was hitting 96% injector duty, perfect 12:1 AFR's at almost 12psi for a total of 295rwhp. Does this seem right given i'm on stock injectors, 45psi base fuel pressure (when no boost line to reg connected). How do these people get 400rwhp out of stock injectors? I've got 450HP fuel pump so i'm somewhat confused.

The rest of my setup should be good for around 350rwhp but it seems I can't get past my injector duties. 12psi on an HKS turbo is relatively low so i'm hoping to wind some more boost in but don't want to at the expense of my engine!

[Sydneykid]

Sydneykid - had my RB25DET dyno'd yesterday and was hitting 96% injector duty, perfect 12:1 AFR's at almost 12psi for a total of 295rwhp. Does this seem right given i'm on stock injectors, 45psi base fuel pressure (when no boost line to reg connected). How do these people get 400rwhp out of stock injectors? I've got 450HP fuel pump so i'm somewhat confused.

You and me both, I have no idea. I certainly can't get there, but I am not a very good tuner.

[Cubes]

All this talk about rwkw injector limits has got me interested why my RB20DET was running in to the 10's on 1bar and making ~150rwkw with only a bosch fuel pump?!?!

Leaning the car out to high 11's ended up making 164rwkw.

My injectors are different to any other RB20DET I have seen.

They are a clear top with a red dot on them & silver body.

The ECU doesn't appear to be chipped (that I can tell), I was thinking maybe they were CA18DET's as that is what they look like.

[Sydneykid]

All this talk about rwkw injector limits has got me interested why my RB20DET was running in to the 10's on 1bar and making ~150rwkw with only a bosch fuel pump?!?!

 

Leaning the car out to high 11's ended up making 164rwkw.

 

My injectors are different to any other RB20DET I have seen.

They are a clear top with a red dot on them & silver body.

 

The ECU doesn't appear to be chipped (that I can tell), I was thinking maybe they were CA18DET's as that is what they look like.

CA18DET Injectors are 340 cc's so it would be virtually impossible for the engine to run well on them without some form of tuning.

[Cubes]

When I get home I'll post up a pic just for arguments sake.

[Cubes]

Here's a pic of the injectors.

[Chris32]

No Problem with the 18psi, RB20DET will handle that easily as long as the tuning is good, of course.

I have yet to see an RB20DET make 200 rwkw on standard injectors.  I have a Nismo adjustable fuel pressure regulator and a GTR pump on ours and the best I could get out of the standard injectors was 180 rwkw and it was at 100% duty cycle over 7,000 rpm.  It has a set of S5RX7T 550cc's in it now and it has more than enough fuel for 225 rwkw.

RB25DET's have 340 cc injectors and they run out of flow at ~210 rwkw.  Some people think RB20's can do the same, but forget that you have to rev them higher to make the same power so there is less time for the injectors to be open.

The most common upgrade for RB20's are the 444 cc GTR injectors, with the GTR resistor pack to match the impedance, they are a good choice at realtively low cost as there are many around.

Mine has made 200rwkw (197,200,200 on three seperate dyno's) on standard injectors. I must admit though, the tune was quite lean. It has got a Bosch 040 in tank pump, and no form of fuel pressure adjustment apart from what the pump delivers. Dunno how, as your calculations seem to point to them being un-able to make that sort of power?

P.S -thats my qoute about the 18psi

Chris

[Cubes]

Chris do your 32 injectors look like mine?

[Chris32]

Chris do your 32 injectors look like mine?

Nah, not really Joel, mine are a really deep yellow

Chances are yours are stock injectors, and maybe in your cars past life it has had the bonnet of for a extended period out in the sun, as red plastic fades quite fast when exposed to alot of UV, it will go almost white quite quick

Faliing that I have 12 spare RB20 injectors, more than welcome to take one if you want to have a go at testing the flow between the 2?

P.S - have you done your R33 brake upgrade yet? I posted a message on your DIY thread, as I want to do the same, but I am unsure if I need to change anything other than the calipers and rotors?

Chris

[Cubes]

No... Brakes are not done yet.

I've only recently got the rb30 finished..

In the pic it makes the injectors look yellowish but really they are a clear top with a red painted dot on them. But yer they would be stockers. I find it interesting as I have never seen injectors of the same colour in a RB20DET before.

[Chris32]

No... Brakes are not done yet.

I've only recently got the rb30 finished..

 

In the pic it makes the injectors look yellowish but really they are a clear top with a red painted dot on them. But yer they would be stockers. I find it interesting as I have never seen injectors of the same colour in a RB20DET before.

Hmm, it could be they simply ran out if red plastic and cast them with clear and put a red dot on them so the people building the engines could work it out??

One of lifes little mysteries

Chris

[Cubes]

lol

Interesting theory..