In the near future I'm going to begin building a b18a block/b20 head for turbo. This is my first turbo project so I'm taking things slow and asking some elementary questions.

Is there a formula or straightforward method for determining what size injectors to use? The whole fuel management aspect of engine building is new to me and a little overwhelming at times.



[Modified by leifintegra, 4:45 AM 12/20/2001]

 

http://www.hondata.com/techinjector.html http://www.rceng.com

art

 

depends how much power you wanna lay down and what type of fuel management your going with either standalone or FMU. Check this site out: http://www.rceng.com/technical.htm

 

Wether I use a standalone or FMU is still undecided. If I replace my ecu w/ a hondata does that do everything that a FMU would do? So I don't need an FMU at all? The Hondata sounds like a wonderful investment and if it will "simplify" things I might go for it. However, my hp goals are quite timid compared to most people on here. I plan on building a beefy engine but will most likely not push its limits. I'd like to lay down 300fwhp max, 220 to 250 fwhp for daily use, possibly less. I don't need auto-x everywhere I drive you know This is a non-vtec application.

I can get some RC 310cc saturated injectors for a good price. I just need to determine if that will be sufficient for my goals. I'm checking out those web-sites currently. I'll probably call RC tomorrow to get some concrete answers.

Will a stock ecu w/ FMU and 310cc injectors be sufficient? Could I run this set-up and then upgrade to a hondata in the future?

Thanks,

Leif

 

you can run the 310's/FMU setup but might as well do everything right to begin with. Go with larger injectors and a standalone, you'll thank yourself. Hondata will definitely simply things for you and then some.

 

Sup everybody,

I was trying to figure out how to select a properly sized injector and I came across some formulas. Anyone can feel free to correct me if I'm wrong.

Finding injector size in CC for XXX amount of horsepower

[(expected BHP x 0.55) / number of injectors] * 10.5 = injector size in CC's

EXAMPLE: [(280 x 0.55) / 4] * 10.5 = 404CC
so you will need at least 440's for 280HP

finding out how much HP an injector is good for

[(CC / 10.5) x number of injectors] / 0.55 = HP

EXAMPLE: [(550 / 10.5) x 4] / 0.55 = 380 HP
so a set of 550CC injectors will be good for at least 380 HP.
BUT the injector duty cycle will be at 100% and I believe the fuel pump would be operating at about 40-50 PSI.

I believe the injector cycle should be kept at a lower % duty cycle, maybe around 75-80%, that way you have room for adjusting the fuel.

So 550's @ 70-80% duty cycle will probably be good for about 330 HP

I did up a chart of all the HP limits of injectors but remember these are at 100% duty cycle. Another thing to remember is that you can also get more fuel by raising the fuel pressure. But I have heard from others one of the reasons to go with a standalone is so you can get ride of those high fuel pressures. Another rule of thumb you should use is if you use the above calculations and come to the conclusion that XXX injector is good for your application then go one size bigger, that gives you room for improvement in the future.

270cc = 187 HP
290cc = 200 HP (5G Lude Saturated)
310cc = 214 HP
320cc = 220 HP (4G Lude Peak-and-Hold)
370cc = 256 HP
400cc = 277 HP
440cc = 304 HP
450cc = 311 HP
500cc = 346 HP
550cc = 380 HP
600cc = 415 HP
650cc = 450 HP
800cc = 554 HP
880cc = 609 HP