Ricer240sx

iTrader: (3)

yeah, so i will soon be upgrading my turbo and plan to run around 20 psi!! on the site there is a dyno sheet for a FC running 416 hp on 19 psi but im sure that motor is ported, mine wont be for a while so i figure ill be sittin around 400 or so....but what injectors should i run, right now i have 550 p and 720s so which i think is not enough....so i was gunna pop for a pair of 1000cc's to put in the sec. and swap the 720's to the primarys would that be sufficient enough?? or should i go bigger somewhere??

thanx for any input!!

Juiceh

iTrader: (4)

720/1000 may be cutting it a little too close.
According to http://rx7.com/cgi-local/2ndgencalc.cgi with that combo you would be at 396HP with an 80% injector duty cycle.

I'd go for 850/1680 it will give you much more overhead and plenty of room to grow. You could do 850/1000 or 720/1300 or 850/1300 as well.

ENZO182007

720 1600 ssems cheapest since u allredy got the 720;s

F1blueRx7

iTrader: (5)

Just to give you an Idea there was a fellow that posted up some tuning results from a dyno session. 437rwhp @16psi w/ 90% inj duty on 4x720's. Thats incredibly dangerous, just to give you some real world results to gauge yourself off of.

Ricer240sx

iTrader: (3)

i c...so 850/1600 is probably what ill end up with then....rather be safe than sorry!!!!

chuck8313BTSDS

Ricer,
The dyno on cheapturbo was done with four 680 at 100% duty with fuel pressure at 43psi at idle. Hit 100% DC at 6500rpms. The motor was not ported, it was a 87 n/a motor with 9.4 rotors. It was a 1st gen that went 11.7 at 124mph. Also ran water/air intercooler.
just to give first hand information.
chuck

upatnight

heres a good link for you http://rx7.com/cgi-local/2ndgencalc.cgi. i was going to use 550s and 1000s to get to 350hp. im useing 550s and 720s and i'll add injectors as needed. good luck.

Ricer240sx

iTrader: (3)

yeah thats the chart i was looking at.....so what kinda results would i see with that turbo.......?

also on nopistons they were telling me to go with 550 and 1680s...i like that cause ill be able to start her right up with the plug and play and low rpm street driving will be the same but then the transition would be kinda harsh into the secondaries wouldnt it?? idk, im still learning so shoot some info at me!! they were also telling me to go with a diff turbo, a streight t4 not a hybrid t3 t4, responce is important to me so any help there would be appreciated as well!!!!

thanx again all!!
Chuck

Ricer240sx

iTrader: (3)

also, whats a good rule of thumb for safe duty cycle maximum setting?? 85% or is that too high??

F1blueRx7

iTrader: (5)

80% is right on the money. Beyond that injectors are more prone to failure.

I'd say ask whoever is going to tune your car about the trade off between 550's and 720's as your primaries. Some of them have tricks to smoothing out your transitions or fixing a rich bottom end.

patman

iTrader: (3)

what ecu are you running? depending on the ecu, it might not be a problem to run 550/1680s. thats what I run, and i have no transition problems on the microtech. that combo is good for way more power than youre planning to make.

if anyone is interested, the way to calculate injector requirements is by using the BSFC (brake specific fuel consumption, in lbs per horsepower-hour) of a rotary. for a NA rotary, you can consider this to be about .55; for low boost turbo, about .6, and for high boost as much as .65. for a small inefficient turbo like you are running (no offense), i'd say .62 or so is a good number. If you're shooting for 400 hp, then you need 400*.62= 248 lbs/hour of fuel. if youre running 80% duty cycle, then you need to divide that by .8=248/.8=310 lbs/hour. this means that at whatever pressure the injectors are rated at, you need 310lbs/hour of total injector flow. to get cc/min, multiply by 10.5 =3255 cc/min. so if you have 2*550 + 2*1680, that totals 4460, or about 40% more than you need for 400hp. in fact, you'd be fine with 2 550s and 2 1260s, but the big ones are similarly priced, so why not get the 1680s and have room to expand. just for reference, 4 720s is only 2880, so that wont do it. you can dick around with the combinations any way you want, as long as you end up with more than 3255, youre ok.

pat

Ricer240sx

iTrader: (3)

i will be runing the Plug an d Play Megasquirt unit for sale in the Group Buy section so i will be runing a stand alone!!

and thanx for that equasion!!!

o and no offence taken im not sure anymore if thats the turbo ill be running, i might have to step it up a bit....

patman

iTrader: (3)

i believe the megasquirt has injector staging controls, so you should be fine with any combo

Ricer240sx

iTrader: (3)

cool thanx, then i guess ill stay with the 550 primarys and get some 1680 sec. or maybe even bump it up to 1800.......

patman

iTrader: (3)

if you read what i just told you, that means that a 550/1680 combination is good for 550 hp. to get that you would need a giant turbo, a totally new fuel system, a super good tune, and you'd still almost definately blow a dowel pin. so basically, they are more than good enough.

The Griffin

Unless you already have the turbo, you would want a T4 footprint.Don't waste your time using a T3 on a rotary.