I recorded a 1/4 mile pass with my Hondata this weekend and noticed that at the top of 2nd and 3rd gear, the injector duty cycle was at 100%. Does this mean I need to move up to the next size injectors? (running stock now - 240).

A friend of mine told me to raise the fuel pressure but this doesn't seem logical.

Thanks!
Raul

 

Can some one confirm this?

 

Come on guys!

 

You shouldn't go over 85% duty cycle on the injectors.

Raising the fuel pressure may help a bit.

 

most likely it is new injectors you need,the next step up would be 310's.Fuel pressure will only help a little.

 

Bump the fuel pressure up to 55 psi and it should help more than a little.

 

You really can do it either way, injectors or fuel pressure. The only downside I can see by increasing pressure is more stress on the pump and the fuel line seals - but I have heard that older injectors tend to have a more difficult time negotiating super high fuel pressures. I wouldn't go higher than 50 psi in fuel pressure for a daily driver.

Also, keep in mind that there are guys out there that have used FMU turbo setups for a couple years daily driven, those things usually get up to 75 psi in fuel pressure.

Take it as you will. Either way will work.

 

um, i was told by a former skunk2 employee that is currently employed at dynamics that fuel pressure can go all the way up to about 85-95 PSI on stock injectors, after that there is too much pressure and the injectors cant close.

BTW, on my old motor I was running about 56PSI on my b20vtec setup and jeff at importbuilders.com is the one that tuned and put the fuel pressure there.

basicly with more fuel pressure, think of it like water pressure and a valve... when the valve is open and there is 35 PSI of water pressure, X amount of water can go through, now at 55PSI of water pressure, you open the valve and alot more water is going to come out. Same theory applies with higher fuel pressure. More fuel is able to come out of the fuel injector because of the increased pressure

 

you can up the pressure but you will have to rescale the fuel map to compensate... if the pump you have will support it honda injectors are fine to about as much as you want.... but keep in mind the stock fuel pump cant take much more than 55psi..... what setup do you have and what kind of power are you expecting to put down..?

 

B16a/Y1 cable trans, JE SRP 10.5:1 pistons, p/p and 3 angle by Alaniz Technologies, Erick's 70mm throttle, type r intake p/p DPR Racing, CTR cams, ANR 4-1 equal lenght header with 2.5 exhaust, Arospeed front bumper mount air filter (ramair), Hondata stage 4b. 170hp.

I have a set of 440 injectors I was saving for when I go turbo. Can I use these or should I bump up the pressure?

 

There is good tech info about fuel pressures and injector sizing here:

http://hondata.com/techfuelpump.html

i'd try higher fp first. you can recalibrate the map for the higher pressure to lower the duty cycle.

it wouldn't be too much of a pain to throw the 440's in there and recalibrate the map for them since you have stage 4 and see how it works

you have a lot of flexibilty since you can tune it yourself.. see what works better for you.

the calculator on rc engineering's site comes in handy for calculating a good injector size:

http://www.rceng.com/technical.htm#WORKSHEET

say you're targeting 200 crank hp. Using .5 bsfc, 50psi at the rail, and 80% duty cycle, the calc cranks out 306cc per minute. So 310cc injectors would seem close to ideal if you run 50psi and don't want to exceed 80% duty cycle.

hope this helps..

 

Excellent info! Thanks!

 

anytime..

i'm sure you figured it out but you can also use the calculator (or formula) to figure out what psi you would need to run to get to 80-85% duty cycle with your stock 240's.

when you run higher pressures it's nice to be able to make sure the pump isn't crapping out with a good electrical fp guage. when i was breaking in my b20 i was running stock injectors on a stock pump with higher pressures. the fuel pump was taking a crap on me and i knew it right away by glancing at the guage.

 

Good point...can I buy the gauge at my local Pep Boys?

 

not sure if you can get it through pep boys. i have the autometer 2 1/16" full sweep electrical.. part# ATM-3363 at summitracing.com

it's not cheap but an electrical guage is the only way to go b/c you don't want to be running a fuel line into the interior.

it's not absolutely necessary but nice to have. if you're running larger injectors at low(er) pressure you really don't have to worry about the fuel pump working too hard