Safe Hp With Stock Injectors
 

All right forum guru's got a question for ya. just got off the phone with (PFS) and just wanted to make sure that I did not have to go into the program(PMS) and change the injector size for my new injectors 1200cc. now they are telling me stock injectors arre good up to 375HP granted you can reach that number but it cant be safely can it? they are swearing that stockers can even do 400HP tuned with stock injectors there is no way that this is safe... I have not yet been on a dyno but I know I am hitting about 355HP give or take to the wheels and I hit 92% on inj duty cycle(peak but comes down a little). there is no way that stock injectors can handle 375HP safely. I am a little bit rich but not that much. I guess I called the wrong place about RX-7 huh? I use to give credit to that place no I am wondering. anyhow anyone with a simial problem or anyone with upgraded injectors that have a PMS I really need your input here.

Thanx
-The Rikki
mods can be seen here
www.dontbearikki.com

go to www.rx7.com they have a injector / HP calculator that can give you an idea of how much HP they can handle and still be safe.

Are you running 1200 cc secondaries? or planning on running them?

Just curious, b/c I have a set that I have not installed due to problems tuning with the PMC, might swap my 850s into the primaries and the 1200 into the secondaries, but worried about idle quality.

thesaint

http://www.newwave.net/~flanham/wlan.../3modrule.html

mike
running 20b fc

hmm..my fd puts down 300 rwhp and i am seeing 93% duty cycle....thus i need to upgrade injectors.

Ok just went to the RX7.com fuel calculator.

I am kinda vague on how to use it.
So how you use it?? Do you just plug
the Max injector duty in its space and thats it?
and it tells you what you need like fuel pump and etc
and FLywheel horse power?


OK i got stock Injectors.
I got PFC, and some runs at WOT I see 96%
Injector duty cycles. I know thats bad.
and I got a upgraded FUEL PUMP on the way.

WILL a upgraded fuel pump lower my injector
duty cycle?? Or will I need to get new injectors?

What's your A/F ratio at? You're probably running real rich. What ECU are you running?

What their fuel calculator does is take your max fuel flow at the given injector duty, and devide it by a BSFC of .63.

I plan on running them just ordered...

i'm putting down 360 whp and i only have a fuel pump and my tuner removed something from the fuel rail. i still see rich even at red line in 4th. i used C16 when the car was doing 360 whp

yeah using c16 and other fuels make the car run richer so you do not have to use as much fuel as standard 93octane. when you dont use race fuel what hp numbers are you running safely??

i dont know the answer to your question. but ive heard that 1200s can be used with the PMS. i believe KDRotary tuned LUVMY94rx7's car for the 1200s with PMS.

I have a tuneing session with him on july 18th!! cant wait....

anyone know how much more fuel pressure you can hit the stock injectors with? i hear most will lock @90psi, but i know thats a real extreme and they aren't atomizing the fuel very well. probably spraying fuel like a garden hose. i hear the japanese love small injectors for that reason (better atomization), and prefer more small injectors over a larger one.

nope but stock level no mods on fuel system is 43psi or so...

My question is how does it run? There must be some compromise in my mind, because the primaries and secondaries will be firing together after a certain point at the same duty cycle, and you cannot control the secondaries by themselves. Thus your ratio of 550/850 is going to be thrown off.

I hope I am wrong and that the car can be tuned to run in a decent manner, but I am not installing them (my 1200s) at this point until i can get an answer.

I will have to call KD and ask a few questions, and or pm luvmy94rx7.

Thanks.

thesaint

kd
 

ask for dave.

cant wait to see dave.. better than peter at least he will talk to you on the phone...

and to my own stupiness I gave him over $20,000 dollars!!! thats a lot of cash

300whp at 10-11 psi. it also did 309 with C16.
the 360 whp was with 14-15 psi. on a hot day

if i am understanding this correctly...in order to increase fuel supply and lower injectory duty cycles you need both a fuel pump and an adjustable rising rate regualtor????
do i really need bigger secondaries if i run full exhaust, intake, powerfc, and M2 IC? I really do not want to upgrade the injectors.

matt

i don't think you need it if you added a fuel pump and removed the dampener. you can run about 12 psi and be happy on the street, and use C12 or C16 and run 14 psi on the track.

tell me more about this c12, c16

You dont need to upgrade your regulator if you upgrade your injectors. Most people upgrade the regualtor to run real high pressure, which in turn makes your injectors push more fuel than they are supposed to.

You can run high 300's rwhp (375-385ish) with the stock system but its WAY dangerous and thats one reason alot of motors pop. The old school ideal a/f was mid high 12's. Now people run mid high 11 a/f ratio and sometimes lower. Its less power but safer.

You probably have a a/f right now of around 10. If you were to fine tune it to an a/f of about 12.5 you make a ton of power till you blew up.

STEPHEN

Rikki,

"Safely" is a relative term, safety doesn't have as much to do with the duty cycle of your injectors as it does everything else like charge temp, a:f ratio, timing. PFS is right on this one, think of PFS whatever you want (good or bad, I couldn't care less) but an FD can certainly make 400 rwhp with the stock injectors, it has been done.


I'm not sure why so many people freak out about hitting high duty cycles with stock injectors. Here are some things to consider:

1) I don't know anyone who has had an injector failure from driving the stock ones at high duty cycles, and a lot of people have done this for YEARS

2) I DO know several people who had enlarged injectors fail

3) There is no reason why an injector should fail just because it is staying open instead of clicking on and off several times per second... someone explain to me their reasoning on this!

4) It is the fuel injection companies that are telling you that beyond 85% duty is a bad thing, big surprise

5) I think beyond 85% *IS* a bad thing in a sense because it leaves no more room for mods if your a:f is exactly where you want it, you could lose tuning flexibility... but I wouldn't freak out about thinking my engine would blow because my duty cycles are high

6) High duty cycles only occur right near redline anyway, we're talking about a second or two when raking through the gears unless you are going for a top speed run at Bonneville


My conclusion is there is no need to upgrade injectors until there is a NEED to upgrade injectors. I run 15psi of boost with stock injectors and pressure and have been hitting 100% duty for almost 4 years now. If one of my injectors fails I'll know it and I highly doubt I'll blow my engine because of it.

Wade