Like what the title says. I was told by someone that 550's are good enough for 18psi (atleast). But on the other hand...Steve (SGT) said 550's are too small. Now...is 550 too small to boost 18~20psi or it's well enough?

Jeff-

 

you can manage about 15-17lbs with the right fuel pressure, but of course it's going to depend on the size turbo you are running, bore size, cylinder head work, compression ratio, etc.

 

think of the injectors in horsepower, rather then boost.. 550's are good for 350whp, 400 but youll be running higher fuel pressures..

 

I agree with DIRep972, I only know the basics about fuel injectors, but I did come across a formula that calculates the max amount of HP a injector size will take.

JUST A WORD OF WARNING, the HP numbers I listed is IF the injector was running at 100% duty cycle. So subtract about 20-30HP from my numbers listed just to be safe. No one has been able to confirm these numbers though so I'll let everyone decide.

I quote BlueShadow (hey thats me)
270cc = 187 HP
310cc = 214 HP
320cc = 220 HP
370cc = 256 HP
400cc = 277 HP
440cc = 304 HP
450cc = 311 HP
500cc = 346 HP
550cc = 380 HP
600cc = 415 HP
650cc = 450 HP
800cc = 554 HP
880cc = 609 HP

If your selecting injectors and say for example your goal is 300 HP don't get the 440cc go with the next size injector like 550cc so that you have room for future upgrades and so you have a safety margin. (you don't wan't to max out the injectors capabilities.

here is the calculations:
CC = [(expected BHP x 0.55) / number of injectors] * 10.5
so to figure out the HP limit of a 550cc injector,

550 = [(HP x 0.55) / 4] * 10.5

550 / 10.5 = 52.38
52.38 * 4 = 209.52
209.52 / 0.55 = 380.95 HP

so a 4 550cc injectors will be good for about 380 HP AT 100% DUTY CYCLE
so I'd say about 350-360 HP is a safe number for the 550cc, the extra 20-30 HP gives you room for adjustability.
http://www.preludeonline.com/showthr...threadid=37508

 

well, i have t3/t4 turbo and built motor...and 18~20psi should be around 350whp right? what if I get 60-1 turbo instead? what size should i get?

Jeff-

 

So a 440cc would be safe up to about 275whp. Excellent, it would take a lot for me to hit that in my D16Y8.

 

That's my current setup (440's in my D16Y8)

 

I run Hondata. I have a standard Drag Gen 3 with 440's and I forget my fuel pressure but up to 8100 rpm my max duty cycle is 81-83%. I produced the power listed in my signature with 93 oct + NOS race formula and VP 103 octane.

I didn't have that resistor pack in time for my dyno session so I used 440s and kept things safe. A/F ratio was around 12-12.5:1 at WOT.


[Modified by sleepy, 8:13 AM 1/14/2002]


[Modified by sleepy, 8:13 AM 1/14/2002]

 

Awesome, how do you like it? You run 10Psi right? How does it feel when it first hits 10Psi in second gear? I bet it is bad-***. Thanks.

 

It's an experience Can't wait to get a new exahust setup though. Breathing out of the stock GReddy DP (which is straw sized), stock cat and stock catback certainly can't help. I'm going with a 2.5" DP, and 3" TP-back asap.. can't wait to feel the top end pull with that bastard!!!

 

Yeah, I bet the difference in top end will be immense!! I plan to have a 2.5" Dp with a 3" Thermal and test pipe/cat. The less backpressure the better!! Hehe

 

I assume these #s are crank hp?

 

GOOD QUESTION!!!

 

I would assume that those numbers are WHP.

Stock tegs use 240cc injectors... and an ITR makes 195 crank HP....

If those numbers were for crank HP, the ITRs injectors would be too small for stock output.

I'm thinking 310 or 370 cc injectors for my JRSCed teg at 9 pounds.

 

[QUOTEI assume these #s are crank hp?[/QUOTE]

I'm almost certain they are wheel numbers. If you follow the linke to po.com you can see PureLudes post, he said that at 250 HP his 440's were at 70% so he figured they would be good for 300 HP (at 100% duty cycle)

If you want I can ask him just to be safe.

 

upon furthur thought, whp sounds about right.
but they should be moved up one level to say each is good to that
# at 80% duty.

 

Yeah, whp seems more accurate.

 

If you go standalone I would go 720;s and up. Personally I am a big fan of the 310's and 370's for a daily driver that still wants to get decent gas mileage.
EVIL

 

so 550's should be good for me to go 350whp till I crave for more power right?

Jeff-

 

well... to let you all know. I laid down 293 to the wheel on STOCK injectors with a Vortec 12:1 FMU and a little Bosh inline fuel pump. Its a t3/t4 turbo as well. Scratch your heads all you want, but it happened.

 

Oh great! And I thought these damn 440's could carry my D16 past the 300whp mark

 

well yes, but we're talking properly tuned, and with fuel pressures that don't kill fuel pumps. I'd love to see your dyno chart with that setup, including the air/fuel. 5 bucks says it's nowhere near 12:1 in the powerband

 

You are right... It was dangerously lean from 6k RPM to 8k. It was only that one run and that was what I netted. I HIGHLY dont recommend trying to get those numbers that I did with stock injectors!

 

I thought so. I appreciate your honesty.

 

everyone has their own "theories", but alot of us run 440's with 350 hsp to the wheel. yeah there maxed out but whatever. it works and it lasts. i know a guy thats run that for almost 3 years now with NO problems. i ran it for a year, and many other people i know have too.