Silvia Club of NSW

Heya,

Since I cant get an answer from ns without getting into the theory of the EFI system I'm going to post this here.


I'm looking at getting the most power out of my redtop sr20 with 480cc injectors, t28, z32 afm, fmic, walbro pump, nistune ecu

I need a tune so am also looking at getting an adjustable fuel reg

Anyone know what the stock fuel pressure is and the max fuel pressure I can safely run without affecting spray pattern, injector life or anything else

cheers
Kirk

Are your current injectors maxing out as the setup is now? upping the pressure is a band-aid solution,and only gives a marginal increase in flow,for a reduction in reliability.


Justin...

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STI - Made in Texas,not Japan.

stock base pressure is about 2.5bar with no vacuum connected.

480's will see you a safe 200ish rwkw with a bit of headroom, say around 85% duty at peak power with stock pressure. With an uncammed red top that's about what i'd expect peak.

I'm not 100% how well the walbro's cope with increased fuel pressure. The only way to be certain is to hook up a flow tester and jack up the pressure by .5-1 bar to see if the pump is up to it.

Not an ideal solution as fergo has stated but as you are really not looking for a significant flow increase over what they'd normally handle it will do the job fine.

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meh

No they arent currently maxing out as its tuned rich, 180rwkw. I plan on getting the tune tweaked a bit and want approx 200kw as on boost the AFRs are stupid rich, something like 9.5 - 10.

I'm pretty sure the fuel pump will be up for providing the required flow, its just the injectors im worried about, someone mentioned that spray pattern might be afftected if base pressure is increased, can anyone confirm?

I'm not looking at getting huge amounts of power out of it with an increase, I just want to give it a bit of a safety margin in case I go to the track on a hot summer day, and I don’t like running injectors close to their max duty cycle. The next step up is 550cc which might be a waste as I will need a complete re-tune instead of just a tweak, same goes for the 740cc injectors, not sure if it warrants a retune + cost of injectors since Im not chasing much more that 200 - 210 rwkw

There will be minimal effect on the spray pattern of a 4 hole injector with a small increase in pressure

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meh

I personally don't like adjustable FPR, just run base pressure. If you fuelling demands exceeds the hardware, upgrade.

btw, S15 injectors are 450cc at base pressure, no idea why everyone quotes them at 480cc

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Guide: RB20DET -> S13 Wiring Diagram

Isnt it something to do with what pressure the flow is tested at? If I remember correctly there was a standard pressure used when testing s13 injectors ie 370cc. A new standard in testing pressure was introduced by the time S15 injectors were released (tested at a higher pressure) hense the 480cc result. Apparently if you test the flow rate of S15 injectors at the same pressure that S13 injectors are tested at then you will get 450cc.

Now the question needs to be asked about Nismo Injectors, which pressure were they tested at? I don’t think the increase in cost for 550cc injectors is worth it from a jump up from 480cc (if they were tested at this pressure) but if they were tested at the same pressure as s13 injectors then it might be worth the extra $$ for a bit more headroom eg. Jump from 450cc to 550cc

The info I has puts Apexi (and probably Nismo) 550cc injectors at 600cc at the "new" pressure (3.05bar - which is what many pressure regs run at with atmospheric pressure reference)
Standard "370cc" injectors flow 410cc at this pressure, and S15s 490 apparently.

The "old" pressure is 2.55bar, which is about standard fuel rail pressure at idle.


So, from the information I have, all at the "old" 2.55bar pressure:

S13/14: 370cc
S15: 450cc
Apexi 550s: 540cc
Sard 550s: 510cc
Apexi 740s: 675cc

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The Engine Whisperer - fixer of things

Awesome, thatnks for the info, I found a cheap set of 740cc so that should definitely be enough if the s15 injectors max out