Any reason not to use nismo 740s?

[Murray_Calavera]

Hi all,

I'm about to put a set of injectors in and I can't seem to look past just throwing in a set of nismo 740s. I'm only looking to make around 300kw on flex, so I can't see a reason to use anything else. Doing a top feed conversion just seems like more work and cost for no real gain. 

I assume I'm correct in that the nismo 740s will idle fine, run e85 fine and cope with 300kw? So is there any real world advantage to using a modern injector, say ID1050X? 

Cheers!

[Dose Pipe Sutututu]

For the price you pay, a little more gets you stainless top feeds - also you'll find the Nismo 740s don't really like low pulsewidths but if you're running E85 then you won't really get that problem as you need generally close to 40% more fuel.

Also modern top feeds, you can push more fuel pressure without sacrificing spray pattern and operation at lower PWs. A S15 I tuned recently has a set of Bosch Seadoo injectors that I cranked up to 4bar base pressure, and at full tilt gets about close to 6bar worth of fuel pressure.

Car idles better than stock

Here's a rather shitty guide I wrote a while back going top feeds:

www.trak-life.com/diy-converting-top-feed-injectors-r33-gts-t-skyline-rb25det/  

 

[GTSBoy]

I'm with him ^.

[Murray_Calavera]

I appreciate that modern injectors are a better thing, but will I benefit from it if I'm only making 300kw?

I can't see that I'd ever need more then base fuel pressure

Edited October 19, 2018 by Murray_Calavera

[iruvyouskyrine]

The newer injectors whilst being excellent at high RPM really do shine at idle/low load, which is what these guys are trying to say. If you pick the nismos up for 1/2 the cost of new injectors then it might be viable, otherwise Bosch/ID would be best.

[Murray_Calavera]

So if we had 2 identical cars, one running 740s and the other running top feed, the top feed car would have a noticeably better idle?

I've never been in a skyline with 740s but I'm guessing they idle fine? I just don't want to pay more for say a 5% improvement in idle quality

[r32-25t]

Have you also considered that yes you want 300 now but that always ends up now I just want 350 and then 400 and etc, swapping to a newer style injector now could end up cheaper in the long run

[Murray_Calavera]

Yep have thought long and hard about that before I started my build, it's all been setup with 300kw in mind. If I want more, I'll build a turbo k swapped mx5 and the skyline will stay at 300kw. 

[GTSBoy]

Quality of life.  It's not just how good the idle is, which hardly matters unless you spend hours at traffic lights.  But better spraying injectors give better fuel economy, better throttle transition, lower emissions, bigger genitalia, the whole lot.

[admS15]

I have nismo 740's on mine. Idle on 98 is horrible, e85 is fine. Im making just over 300 rwkw on e85 and they get above 90% duty cycle at times. Go the modern injectors is my advice. The only good thing about nismos is that they drop in with no mods.

[Dose Pipe Sutututu]

"if" you do go with the Nismo 740s, I still recommend changing the OEM fuel regulator, especially with bigger pumps.

Yes all of SAU and others will say "the OEM FPR will work and flow xyz blah blah blah" but when you log the fuel pressure data you'll understand what I mean. You get these nasy spikes between transient events.

If you do go down the path of Nismo 740s with an aftermarket FPR, steer clear from the SARD bullshit - they're horrendous, get at the very least a FPR800 or FPR1200 Turbosmart unit.

[Murray_Calavera]

Thanks heaps for all the feedback everyone. Will be going with the ID1050X's setup for sure. 

[LWO]

Sensible discussion with lots of freely given hard learned info.  Didn't know Sau still had it in it?  Hat tipped good sirs.

[Pattey21]

Glad this topic came up I'm in the same boat currently. 

 

Kudos Motorsports and golbeyautoparts to kits but I'm yet to contact them if the will be bolt in jobs that fit under stock plenum 

 

Waiting for a reply from Scotty 

[Dose Pipe Sutututu]

35 minutes ago, LWO said:

Sensible discussion with lots of freely given hard learned info.  Didn't know Sau still had it in it?  Hat tipped good sirs.

I'm happy to assist when someone asks a genuine question and actually have done their part in research.

10 minutes ago, Pattey21 said:

Kudos Motorsports and golbeyautoparts to kits but I'm yet to contact them if the will be bolt in jobs that fit under stock plenum 

Most aftermarket rails will fit with 1/2 height injectors (~38mm o-ring to o-ring).

On my R34 NEO motor, using a R33 plenum (long story) I've got Bosch 1550cc 1/2 height injectors with a run of the mill Plazmaman fuel rail.

Do not use 3/4 height injectors, you will need to grind down parts of your stock plenum to fit on R33 stock plenums.

 

Now onto R34 NEO motors.

Do not use 1/2 height injectors OR 1/2 height injectors (supply side) with the extenders to make them 3/4 height. They will not work, nor will they fit - regardless of what "shops" or "online retailers" say, you need proper 3/4 height injectors from the get-go. I put together a massive post somewhere on SAU about this. The only 1/2 height that will fit are those with the extended nozzle, where you can add a bottom sleeve (nozzle side) to make them 3/4 height. They're commonly advertised as Bosch 1250cc.

 

 

[Pattey21]

15 hours ago, Dose Pipe Sutututu said:

I'm happy to assist when someone asks a genuine question and actually have done their part in research.

Most aftermarket rails will fit with 1/2 height injectors (~38mm o-ring to o-ring).

On my R34 NEO motor, using a R33 plenum (long story) I've got Bosch 1550cc 1/2 height injectors with a run of the mill Plazmaman fuel rail.

Do not use 3/4 height injectors, you will need to grind down parts of your stock plenum to fit on R33 stock plenums.

 

Now onto R34 NEO motors.

Do not use 1/2 height injectors OR 1/2 height injectors (supply side) with the extenders to make them 3/4 height. They will not work, nor will they fit - regardless of what "shops" or "online retailers" say, you need proper 3/4 height injectors from the get-go. I put together a massive post somewhere on SAU about this. The only 1/2 height that will fit are those with the extended nozzle, where you can add a bottom sleeve (nozzle side) to make them 3/4 height. They're commonly advertised as Bosch 1250cc.

 

 

Okay cool,

 

So to be clear half height for rb25det r33, which is what i have

 

3/4 height for rb25det neo r34

[Dose Pipe Sutututu]

^  correct

 

[Pattey21]

1 hour ago, Dose Pipe Sutututu said:

^  correct

 

The setup for mine is really only going to make 230-250kw max. Setup will be hypergear 21u g2 (not g3) 350hp turbo,z32 afm and nistune and will only be running 98. Its purely a daily hence turbo choice. 

 

I was looking at xpurt 525cc or Bosch 550cc shorties as I feel anything larger is overkill and I don't want to sacrifice low/partial throttle driving and fuel economy.

 

With the better technology in top feeds would there be much difference in economy, idle and off boost performance between 500-550cc top feeds vs 1000's.

I appreciate going bigger allows for more headroom but i won't be going any bigger...famous last words I know

 

[Dose Pipe Sutututu]

35 minutes ago, Pattey21 said:

The setup for mine is really only going to make 230-250kw max. Setup will be hypergear 21u g2 (not g3) 350hp turbo,z32 afm and nistune and will only be running 98. Its purely a daily hence turbo choice. 

I was looking at xpurt 525cc or Bosch 550cc shorties as I feel anything larger is overkill and I don't want to sacrifice low/partial throttle driving and fuel economy.

With the better technology in top feeds would there be much difference in economy, idle and off boost performance between 500-550cc top feeds vs 1000's.

I appreciate going bigger allows for more headroom but i won't be going any bigger...famous last words I know

During my yesteryears with my old 372kW R33 motor setup, I ran 875cc Siemen DEKA V shorties (aka 80lb). It idled dead on stoich at 14.7 AFR on 98RON.

Nismo 740cc would have not been able to do so and fart/pop.

[BakemonoRicer]

I'm using a radium fuel rail which fits under the stock plenum and has -8an ports.

That'd be the go for an R33 as well. And Bosch 1650cc stainless injectors ftw. The injectors pop right into the rail no need for adapters.

Look at this, DONE!

http://www.radiumauto.com/Top-Feed-Fuel-Rail-Conversion-Kit-Nissan-RB25DET-P1038.aspx