crewchief264

I was sitting here drinking a beer and watching king of hill thinking of injectors and thinking that maybe my ideas were wrong? So here it is will a 370cc injector flow the same rate as the stock injector, at say idle all the way thru the normal easy driving range? I was just thinking that maybe throwing the 370cc's on would be like changing to a 4 barrel carb, say I had 350 with a 2 barrel and decided to go to a 600 cfm edelbrock,is this the same? let me know what you think? I personally think that putting 370 injectors on my 10psi (soon to be front mount intercooled) max is a waste, i don't see the need, because my a/f ratio gauge always reads rich- no pinging, so why change my holley (mustang) 255lph intank pump to the walbro pump that requires an adjustable regulator and the apexi set up with 370cc's. I see at wot 70 psi maybe, max and have had no problems and performance is great. Why do you guys run that 90psi plus++++ psi and then you have to reduce the baseline psi so it idles right?? I don't understande why you want such high fuel psi othe than to maybe maximize the stock injectors flow rate by maybe over pressurizing them??

nateplaysbass

What exactly are you asking?... I'm not sure, but as far as reasons to use the 370cc injectors, it's so that you don't have to run such high fuel pressure. in order to get enough fuel on stock injectors one must raise the FP.

As far as comparing carbs to fuel injection, please don't... It's a completely different ball game. Carbs use venturi's, and they can pretty much dump fuel all the time, Injectors have a duty cycle: how much of the time the injectors are open vs closed. when duty reaches 100% you cannot get more fuel... You're boosted, when swapping a carb, you're just allowing more air into the engine by having more barrels for the air to go through. you get power from a carb because of airflow, not because it dumps more fuel or anything. Fuel injection is much more picky, more acurate, but more picky.

I don't know if this helps at all, If it doesn't help, then I don't know what you're asking... I'm not trying to flame or anything, just trying to help a fellow max

IceY2K1

iTrader: (3)

Inorder to get 240cc(stock) injectors to flow the same amount of fuel as 370cc injectors, you'd have to increase fuel pressure to ~104psi, which isn't safe.

To put it another way, using a "safe" recommended 80% duty cycle and BSFC of 0.55 for SCers, your 240cc injectors at 70psi are good for 253bhp(215whp). So, you're ABOVE the recommended "safe" duty cycle. Just for reference at 100% duty cycle, you're max supportable is 316bhp(268.6whp).

With 370cc injectors, at:
80% DC ~390bhp(332whp)
100% DC ~487bhp(414whp)

BSFC and your Air/Fuel Ratio are related, but BSFC of 0.55 is recommended for rich tuned cars on pump gas to keep detonation at bay. Your AFR could make those numbers higher/lower, so give yourself some room or use your dynos to approximate better. Here are some useful calculators you can use: http://www.rceng.com/technical.htm

370cc injectors allow people to A)run more boost at the same fuel pressure or B)keep injectors in the "safe" range withOUT having to run sky-high fuel pressure.

Your choice, but for <$300, it's well worth it to keep those injectors safe/happy at lower duty cycle/fuel pressure PLUS if you want more boost, plenty of growing room.

crewchief264

The carb thing was a bad example---sorry. So for instance, I currently running the stock injectors and 10 psi boost with an holley pump that see's 70psi at wot. Am I maximing out the injectors, and am I right near the theoretical detonation edge? Also, if I were to put in the 370's is that all that is needed? No fuel psi regulator--no apexi, no new fmu disc? correct me if I am wrong.

SonicDust187

iTrader: (11)

If you install 370 injectors all you have to do is set base fuel pressure to 27psi at idle.

Stephen Max

iTrader: (59)

At 10 psi you are running your injectors at 100% duty cycle. That's why you need the fuel pressure bumped up to 70 psi to give you the additional fuel you need. My experience with boosting at 10 psi is that I needed more than 70 psi fuel pressure to keep from detonating with the oem injectors.

If you go with the 370's, you need an adjustable fpr, maybe a fmu with a 3 or 4:1 disk for coarse tuning, and a SAFC for fine tuning. Pretty much the same as with the oem injectors, but you will be able to deliver more fuel at a safer pressure.

Nealoc187

iTrader: (23)

wait so I can use 370cc injectors and a stock ECU and all I have to do is drop the base FP to 27psi at idle and I will be recieving all the benefits of using 370cc injectors (by that I mean I will be able to run the higher HP levels that 370cc injectors allow?)

crewchief264

so if i install the 370's all i need to do is install a fpr on the fuel rail and set base psi at 27psi. thats all?? also what is a good fpr to run and where to get? how does the stock regulator come off?

SonicDust187

iTrader: (11)

I am saying that with stock maf and no ecu upgrade, to get the car to idle properly you will need to lower the idle fp to 27psi and you will have the benefit of running bigger injectors.

Prodeje79

I got my sard from Jay25 and the off fittings from sx7r.com.

If you hurry, Jaime may have one left!

JAY25

iTrader: (38)

I dont have any SARDS for sale. Sold them all.



Neal you can run 370s with stock ECU, all you have to do is lower your Base FP with a FP regulator and remove your stock FP regulator and replace it w/that fitting SX7R sells. Thats it. I am using my stock MAF and ECU for now until I can upgrade to a Z32 MAF and what ever I decide to do.

SonicDust187

iTrader: (11)

Anyone have instructions on how to replace the stock FPR, I currently have non high pressure walbro pump and my idle fp went up to 37psi.