Since I dont' have a Apex Power FC or Hondata, I'm trying to calculate what injector size would be optimum for my setup. With my new set up I should easily put down 205. Right now I"m running on stockers at 48-50psi. My hunch is that I'm at the limits of the injector cycle. The only way I can verify this is by doing this:
BTW I'm using a 80% injector duty cycle for peak power.

CALCULATING INJECTOR SIZE

(BHP X BSFC)
---------------------
NO of injectors x 0.8


I'm assuming BSFC or Brake Specific Fuel Consumption to be at 0.49

Plugging that into my formula I come up with this:


(205x 0.49)
______________ = 31.3 lbs/hr or roughly a 310cc/min injector

(4 x 0.8)

The only way to know for sure is to know your engine airflow but since I do not know that or have no way of finding that out, this is the only way I can figure this out. Does anyone else have any other suggestions for finding this out?

I have a skunk ecu with a VAFC by the way. TIA

 

nobody can help me out, come on!!! I can get a deal on some 310 injectors. Experts please give me your opinions.

 

RC has a calculation page on their site, and there is one here too: http://www.smokemup.com/utilities/ca...l_injector.cfm
I am running 370s on 45 PSI for 200 whp and 137.9 ft-lbs. I choose the 370s so I would have some growing room...


Jason

 

thanks looks like a 310 would work in my application. guess i'll have to buy a set and check em out. My plugs are can you say white! that's with a 50 psi fp, a skunk ecu and vafc leaning out -10% all the way with -8% up top at 8 and 9k.

skunk ecu i believe is about a 30% richer program from stock.

the funny thing is when i raise fuel pressure the car doesn't like it. it responds better to me adding fuel with the vafc.

I'm wondering if running a bigger injector say a 310 at normal fuel pressure would be better than what i have right now. The way its running now is really good, but i'm sure its on the lean side. Especially now that its colder out. hrmmm

that page was pretty useful but they calculate the injector duty cycle at 100%.

 

I was under the impression that you can only remove fuel with a vafc, not add it?

 

Will you need to reprogram the stock ECU after you change to RC 310cc injectors? Or some tuning with FPR and VAFC on a dyno will do the job?

Well, for sure you can add fuel with the VAFC, I have to add 10-15% fuel with the VAFC on my car to have it run right. That why I am thinking about a larger injectors. Try to decide between the Prelude one or the RC 310cc one.


[Modified by mafay2, 9:12 AM 11/17/2001]

 

We use 310's on all our 230+ all motor cars.

according to my hondata, i have TONS of duration left on the 310's on all our fully built B20 Vtecs with even Toda Spec C cams.

Tried and tested.

Jeff

 

Jeff,

Have you used an upgraded fuel pump (like a Bosch or Walbro) with 270's (upping the FP to 55 psi get the same flow as the 310's)? Wouldn't that combination work as well as a stock fuel pump and 310's?

 

I might upgrade the fuel pump just for insurance. yea and 270's with upped fuel press would essentially be the same as a 310.

as far as remapping the ecu i won't have to do that. The vafc can add fuel by means of making the pulse width longer. I think what i'm gonna do is run a 270 and add fuel with the vafc.

I'm contemplating going to a Hondata, this would be nice since I could monitor all the functions and see if i'm maxing out the injectors. Then i'd have to sell my vafc and skunk program. heard a lot of good things about the hondata so i may do it.

car runs strong as a horse but my plugs are white and that frankly concerns me.

 

You will have to run 57.34 PSI on 270s to get them to equate to a 310 injector. A 310 from RC is rated at 43.5 PSI.
It would make sense to me to buy 310s, and not buy 270 AND a fuel pump that you can depend on at 57+ PSI of fuel pressure. I know my ITR pump was giving out on me at a little over 60 PSI...


Jason

 

Im about 50 PSI with the 310's.

With the 270's its well over 60 PSI and thats too much.

I only use 1 kind of fuel pump. The best kind.

NOS. Most reliable fuel pump I have ever seen. That Bosch is pricey and the NOS is better.

You dont have to modify the NOS pump either. Its convienent, cheap and can supports HUGE boost for a turbo car.

Shoot, you can buy 2 NOS pumps for the cost of 1 Bosch pump, and the bosch pump wont even fit, you have to modify it.

Its no contest. Walbro I have, its good, but pricey. I am using it on 1 B20 right now, the rest NOS. We all run 310 injectors, from 45 PSi to 50 PSI it seems on all my motors. We all have SX Fuel regulators too...so that helps...that B&M has such a small PSI range.

Jeff

 

I agree Jeff.
I choose the AEM, works just fine, but the B&M just does not have the range needed for these applications. Not dissing the SX, I choose AEM since I deal their products...
I have never tired the NOS pump, but I am using the Walbro 255 high pressure. Other options are the Supra TT pump (pricey too) and the 93+ RX-7 TT pump. Both of those are in tank pumps and should drop in just fine. I think, if I remember correctly, the Supra is rated in the 260 range and the RX-7 in the 230 range...

Jason

 

the reason I ask : I already have a Bosch fuel pump (got it at a pretty good price used) and have 270 injectors. I really don't want to spend the cash for 310's, if I don't have to.

If I run 60 psi FP I think the Bosch can handle it. What do you guys think?

Never thought about the NOS fuel pumps. Are they rebranded from another manufacturer? ...eg. Granatelli and Holley are Walbros.

BTW I use an AEM FPR and chucked my B&M.


[Modified by Michael Delaney, 3:16 PM 11/17/2001]

 

FAST94GSR:

I'd get the 310's with a stock fuel pump, if I did not already have 270's and a Bosch pump (not installed yet). Also consider that the Skunk2 ECU must be configured for the 310 injectors...I suggest calling them and making sure they are programming based on your engine package.

cheers



[Modified by Michael Delaney, 3:28 PM 11/17/2001]

 

damn, I'd have to reconfigure my ecu if I went to 310's. ay yay yay.

Maybe I'll just sell my vafc and skunk ecu, and have this guy I know burn me a hondata chip.

 

I'd call Dave Hsu at Skunk2 and ask for their advice. The hondata.com website says in their tech FAQ that the stock ECU is able to adjust for up to a max. injector size of 310 cc/min.

It all depends on what the Skunk2 guys did with their ECU and what the maps are configured for. I just thought that if you just placed the order you can call and tell them that you will get the bigger injector size so they can configure the program properly.

The VAFC should help you adjust the fuel with the skunk2 ecu even if the ecu was configured for 240's. It just is not as optimal.

give Skunk2 a call...seriously...