What's going to top out first?

[Nismo180]

Okay, this is getting frusterating I tried searching, tried online fuel injector calculators and I'm getting different answers everywhere. Here is my planned mods:

GT2871R .64 trim
555cc injectors
Nismo FPR
Z32 MAF
JWT ECU

Turbo rated to 385hp but it's a Garrett rating so I'm sure it can get that to the ground on a proper engine, anyway, which will top out first the turbo or my injectors? If anyone has hard evidence taht the injectors will indeed top out before my turbo runs out of air I'll spring for the 720s, but this is a daily driven car so I'd really preffer the smaller ones.... I'm so torn.

[NemeGuero]

Isn't Z MAF only good to 350hp?
And are the 550s drop in to stock KA rail? If so, I'll take 'em.

[codyace]

Z MAF I believe is ok up to around 500 hp IIRC

2871r .64 (like I have), with correct mods could squeeze out 385whp I believe at 20/21 psi and correct mods

555cc would be at 100 percent probably around 375/380ish???


I'd say at 20 psi your turbo and injectors would probably be on the verge of maxed out...

[Nismo180]

Isn't Z MAF only good to 350hp?
And are the 550s drop in to stock KA rail? If so, I'll take 'em.

Dunno if they'll drop right in but I know they make two kinds one size might fit :shrug:

Hmmm, wonder if with the FPR and the Nismo injectors tendancy to flow on teh high side of their rating I can get away with it...

[NemeGuero]

Yah you can flow them on the high side.. but you'll just burn them out quicker.

[Nizzan4u2nv]

Run the 4 bar program and run 4 bar fuel pressure. The turbo will top out first at around 20psi. Its not very effiecient after that. Your fuel setup will support more then 500whp if you run 4bar. Dont forget a good fuel pump.

[nissanguy13]

tell me if im wrong, but isnt the z32 na mafs max out at 350hp and the mafs for the turbo version max out at 500hp?

[harlockssx]

Your injectors are too small for 385 rwhp. A 2871R .64 AR isn't going to get you 385...POSSIBLY 385 FLYWHEEL Hp, but I doubt it. Most guys are lucky to get 350 out of it. It does spool fairly well though. I'm kind of biased now though, I'm turning away from T2 flanged turbos entirely...I've used stock S13, S15, 2871 & GT25R .86 AR...the GT25R got me to 390 at 1.4 boost with cams, intake, ex. manifold, Q45 TB, crank & underdrive pulleys, 850cc Sards, electric fans & blow through Z32 mass air sensor.

[Nismo180]

Your injectors are too small for 385 rwhp. A 2871R .64 AR isn't going to get you 385...POSSIBLY 385 FLYWHEEL Hp, but I doubt it. Most guys are lucky to get 350 out of it. It does spool fairly well though. I'm kind of biased now though, I'm turning away from T2 flanged turbos entirely...I've used stock S13, S15, 2871 & GT25R .86 AR...the GT25R got me to 390 at 1.4 boost with cams, intake, ex. manifold, Q45 TB, crank & underdrive pulleys, 850cc Sards, electric fans & blow through Z32 mass air sensor.


Fine by me, I'm not going for a number I'm going for a setup. It will probably never see a dyno they, lie. Maybe just some time with a wideband and the S-AFC over and above the JWT ECU. The turbo is a good match for the motor and from there I want the smallest injectors I can get away with.

BTW what duty cycle are your 850s at for that HP level? I know your setup it's in almost everyone of your posts so far.

[harlockssx]

Fine by me, I'm not going for a number I'm going for a setup. It will probably never see a dyno they, lie. Maybe just some time with a wideband and the S-AFC over and above the JWT ECU. The turbo is a good match for the motor and from there I want the smallest injectors I can get away with.

BTW what duty cycle are your 850s at for that HP level? I know your setup it's in almost everyone of your posts so far.

Not sure of the duty cycle, will have to take a look but I think it was in the 60 percent range...my mass air meter will probably top out before they do though. I'm in the middle of upgrading right now, building an all forged internal motor with ported head, solid lifters & BIG turbo. I will have to ad another fuel pump though, a single Walbro 255L isn't going to be enough. I'm shooting for 500 WRHP at 21 PSI...I think this turbo should do it http://www.full-race.com/catalog/product_info.php?cPath=214_551&products_id=857

I'm still new on this forum, so most people here don't know me yet. I'm usually on Zeroyon.com , but want to swap info with more stateside guys as I will be coming back within the next year or so.

[codyace]

Your injectors are too small for 385 rwhp. A 2871R .64 AR isn't going to get you 385...POSSIBLY 385 FLYWHEEL Hp, but I doubt it. Most guys are lucky to get 350 out of it.


Not sure whre you get that from...thre are 2 or 3 setups that are over 360whp at 18psi with mods....so like I said before, at higher boost levels it should increase to the verge of 400whp

[NemeGuero]

Yah, 555s will kinda be sweating for 385rwhp.

Formula: (expected hp x 0.55)/#of injectors = lbs of fuel per hour
and
(cc/min) = (lbs/hr x 10.5)

so, 550cc/10.2= 53.92 lbs/hr

53.92 x 4 = 215.68

215.68/.55= 392.14 hp and thats at 100% duty cyle. I wouldn't go over 95% duty cycle.

Here's a helpful chart http://www.megasquirt.info/manual/minj.htm

[Nismo180]

Hmm, according to that calculator I could pull it off with the 4 bar pressure maps, but if down the road I get some cams, and get a little carried away with the high octane maps and my profec-B something is going to go boom and it's gonna be expensive. Guess I'll just give in and get the 740s Anyone know which model fits the SR fuel rail? The ones for the early 300ZX or the later model ones?

[hellion240sx]

ok one question i have i worked out the formula, plugged in numbers wirked out. dont reaally understand it yet but i worked it out. trying to learn the injector language. well taken from the injector group bub by DeatschWerks

550cc up to about 360whp
650cc up to about 430whp
750cc up to about 500whp
850cc up to about 550whp

so what if your calculations hit you up at 600cc do you get 550cc's or 650cc's? and your at 375-385 hp

[NemeGuero]

If you're in the 600 range.. play it safe and get 650ccs.
that formula I posted was from another thread on "injector size vs hp"