Max Power Out Of Standard Gtr Fuel Setup?

[Duncan]

imacul8 all gtr injectors are rated at 440cc/min, in practice I had trouble finding any flowing more than 420 even after serious cleaning

[Beer Baron]

bugger, i was hoping to get 270-280rwkw's from mine! With a FPR!

there is no reason you cant get that. dont forget the injectors dont know what power you are making, they just meter out fuel. duty cycle depends on the tune too. so with a leaner tune i could make more power, and have less duty at the same time. but it's around that mark that you will be pushing them. if 270-280 is all you want to make then fine, but if you may be after more power down the track skip the 440s and go for something bigger.

[mr_rbman]

there is no reason you cant get that. dont forget the injectors dont know what power you are making, they just meter out fuel. duty cycle depends on the tune too. so with a leaner tune i could make more power, and have less duty at the same time. but it's around that mark that you will be pushing them. if 270-280 is all you want to make then fine, but if you may be after more power down the track skip the 440s and go for something bigger.

well should have my new valve springs and fpr installed in a month or so and i'll let you know the results!

[Omurru]

Just for reference I am currentley making a bit over 400hp on a stock fuel system, and thats the fuel system limiting the power not the engine set-up, it's been tuned so it's 'safe' but I need to put in a fpr just for the extra saftey net and will need to upgrade injectors and pump before I can make anymore power.

Thats all on a 33 though so not sure if it's exactly the same as the 32????

[mr_rbman]

just saw a 32 gtr today make 295rwkw's on standard fuel system!

[Sydneykid]

just saw a 32 gtr today make 295rwkw's on standard fuel system!

Repeat after me ............happy dyno..............

295 + 75 X 1.34 = 495 bhp

I don't think so Tim

cheers

[Cubes]

Yes 295rwkw on std fuel system I believe they are not telling you something or they don't know.

People like to gloat and make them selves feel important.

[Lukus]

Would 600cc injectors be ok if i wanted to push for 350kw? Or would 700cc's be a better choice? They are roughly the same sort of price? I'd prefer to run my injectors at around 80% duty so at a guess 700cc's would be right. Anything over that can cause them to jam open, or worse, jam closed which is not cool. Guy, don't push a stock fuel system that far. Anything over 90% is really asking for trouble.

The Nismo pump is rated at 25% bigger than a factory pump. Would a 040 be a better choice? These pretty much drop in and would appear to flow more?

[Sydneykid]

Would 600cc injectors be ok if i wanted to push for 350kw? Or would 700cc's be a better choice? They are roughly the same sort of price? I'd prefer to run my injectors at around 80% duty so at a guess 700cc's would be right. Anything over that can cause them to jam open, or worse, jam closed which is not cool. Guy, don't push a stock fuel system that far. Anything over 90% is really asking for trouble.

The Nismo pump is rated at 25% bigger than a factory pump. Would a 040 be a better choice? These pretty much drop in and would appear to flow more?

It's just simple numbers, follow the Sydneykid rule of thumb

1 cc of injector = 1 bhp in a 6 cylinder engine

That's already allowing for 85% duty cycle (so don't take it away again later)

700 cc = 700 bhp

700 bhp = 522 kw

522 kw - 75 kw = 447 rwkw

600 cc = 600 bhp

600 bhp = 448 kw

448 kw - 75 kw = 373 rwkw

700 cc per minute = 42 litres per hour

42 litres per hour X 6 injectors = 240 litres per hour

That's at 100% duty cycle (so don't add 15%)

A standard R33GTR pump is 210 litres per hour at 12 volts and around 245 litres per hour at 13. 8 volts

If the Nismo pump flows 25% more, that's 263 litres per hour at 12 volts and 306 litres per hour at 13.8 volts.

There you go, your answer is in the numbers.

cheers

PS; I could have simply said 600 cc injectors and the Nismo pump will be fine, but now you know how to do the numbers yourself. As a smart guy once said, "give a guy a fish and you feed him for a day, teach him how to fish and you feed him for life".

[mr_rbman]

Repeat after me ............happy dyno..............

295 + 75 X 1.34 = 495 bhp

I don't think so Tim

cheers

Well my car went on the dyno the car before this GTR and only made 214rwkw's compared to a few weeks ago making 228rwkw's on the BOOSTWORX dyno that is renownd for being pretty accurate or even perhaps a little low and i have made absolutely no changes since then!

This GTR had an R34 engine with the N1 turbos with a 3.5" exhaust and 19psi, that was the only mods!

I guess he could've been lying about his mods but i looked over the car very carefully for a long time with him and it looked pretty damn stock and definitely didn't have an aftermarket comp.

(Joel, my car wasn't showing any signs of valve float and we revved the car up to 6500rpm! And it was making max power before 6500rpm. This is leading me to think that the valve float isn't causing me to not make the power i should be! I'm thinking it could be something else but i can't for the life of me think what it is!)

[saliya]

It's just simple numbers, follow the Sydneykid rule of thumb

1 cc of injector = 1 bhp in a 6 cylinder engine

That's already allowing for 85% duty cycle (so don't take it away again later)

Hi Gary,

As always, some insightful comments

Why would we not allow for 100% duty when trying to calculate a theoretical maximum?

For example, do injectors get hot or damaged by being on for more than n% of the time?

Is it to do with timing of fuel pulses? Do they wear out faster? So in real life, we do not

run 100% therefore not in the formula either?

I've heard the 'leave headroom for safety' argument; but I can't see how it applies. If

any one injector gets blocked then there's going to be a lean-out (because approx only

5/6 of the required fuel is going to be delivered, regardless of maximum duty).

Or is this simply to allow for the worst-case in a calculation sense - i.e. most injectors

cannot operate at their rated capacity and the 85% is a good approximation for the

condition of most injectors?

Regards,

Saliya

[Cubes]

(Joel, my car wasn't showing any signs of valve float and we revved the car up to 6500rpm! And it was making max power before 6500rpm. This is leading me to think that the valve float isn't causing me to not make the power i should be! I'm thinking it could be something else but i can't for the life of me think what it is!)

It needs more boost then.

No idea.. it may be floating a little causing torque to drop off a little early but not quite enough for the lifters to pump up so its not that noticable??

Up the fuel pressure push more boost in to it and see what happens, somethings not right through as its definitely not making the power it should.

The first sign I noticed saw when mine was floating was I had to pull timing out of the top end, considerable amounts of timing and there was one rpm point where it would ping no matter what ign value was in there.

Pull a psi or two out and it was able to run a full 20degree's ign timing vs 2psi more and only 5-6degree's with still slight ping.

I really wouldn't mind checking out what ign. values your running at wot some time, would be interesting if I can see the same trand as mine shows.

I've now got another set of lifters so I will be dropping them in as soon as I make up a little jig to fit the valve springs up.

[mr_rbman]

It needs more boost then.

No idea.. it may be floating a little causing torque to drop off a little early but not quite enough for the lifters to pump up so its not that noticable??

Up the fuel pressure push more boost in to it and see what happens, somethings not right through as its definitely not making the power it should.

The first sign I noticed saw when mine was floating was I had to pull timing out of the top end, considerable amounts of timing and there was one rpm point where it would ping no matter what ign value was in there.

Pull a psi or two out and it was able to run a full 20degree's ign timing vs 2psi more and only 5-6degree's with still slight ping.

I really wouldn't mind checking out what ign. values your running at wot some time, would be interesting if I can see the same trand as mine shows.

I've now got another set of lifters so I will be dropping them in as soon as I make up a little jig to fit the valve springs up.

I'm going up to my parents tomorrow so i can pop round if you like and you can check things out and i'll take you for a spin!

I don't really wanna run more than 15 psi though!

I'm getting my valve springs next weekend off sky30, maybe we could do it together one weekend?

I've been told to get a spark plug and drill the guts out and solder an air fitting on for some compressed air to make it easier to pop them out!

[Cubes]

I'm going up to my parents tomorrow so i can pop round if you like and you can check things out and i'll take you for a spin!

I don't really wanna run more than 15 psi though!

I'm getting my valve springs next weekend off sky30, maybe we could do it together one weekend?

I've been told to get a spark plug and drill the guts out and solder an air fitting on for some compressed air to make it easier to pop them out!

Tomorrow is fine.

Yep I think that sounds like a good idea.. your welding skills + my what ever lol and yer we should be able to get them done.

I've got a few pics of a spring compressor thats suitable for the rb det head.

[mr_rbman]

ok, i'll message u on yours and julie's phone to let you know when i'll be coming round! i'll post up my graph from yesterdays dyno day!

[Cubes]

Post away. or email a nice quality if u wish.

I have so many damn dyno graphs its not funny.

[mr_rbman]

Post away. or email a nice quality if u wish.

I have so many damn dyno graphs its not funny.

that oxygen sensor u gave me a while back! Do you remember if it was working perfectly? As you'll be able to see from my dyno graph it runs a bit rich to start with a shaun mentioned something about him thinking it was on its way out and the tuner said yesterday that when it was on the dyno to begin with it was running very rich but got better once it warmed up!

So if yours is ok i'll put that one on!

[mr_rbman]

as u can see the graph is really good which doesn't help me in finding why it isn't making the power it should. Its making awesome torque and the guy running the dyno was amazed at the torque the thing was pulling, on my first run it was slipping on the dyno so he had to strap it down even more!

1. i've checked everywhere for air/vacuum/boost leaks

2. thought the cam gear timing might be out but that would cause it to run rich/lean and it not

[Cubes]

My o2 sensor was fine as far as I know, it was returning really good fuel economy before the injectors went daggy.

So that was on Graham Wests Dyno.

What was yours on there for just a check up or?

Once when I was at Graham Wests he did mention that the dynologs read a little lower than the others.

The run was finished at 6500rpm, so it held that power perfectly to 6500rpm? Thats not to bad really..

As for the low power.. It doesn't make sense, even with the vg30 it was down on top end power.

One last.. what did Graham charge for a power run?

[mr_rbman]

it was just a dyno day that some car club organised and i thought i'd go on there to see if i could see valve float and just to compare it to another dyno! Ye it stopped at 6500rpm cause thats what i set the rev limiter to! And as you can see it pulled hard to there and held the power really well and didn't drop off till he backed off, he said its an awesome graph and hasn't seen anything like it since he had his xr6t on there, even the gtr whilst making more power the graph was nowhere near as good. he said i could bring it back this week and i could put it back on they dyno and he'd strap it down properly this time as he thinks its still slipping, (free of charge) which i'm thinking i might do and put that oxygen sensor in that you gave me to see if its all good!

Edited June 11, 2006 by mr_rbman