Injector Sizing

[Waggy]

Hi guys - I'm currently gathering parts for my B16A all-motor build, and i've been researching injectors and their types and sizing.

I've seen that there are Peak and Hold and Saturated types. My car is an EM1 (OBD2) and from what I've gathered I have to use the saturated type. My question is, what size?

My car will be using CTR pistons with a fully worked head and Skunk2 Stage 1 cams. I was thinking 440cc? Any input?

[Slow96GSR]

Try finding a calculator. 440's seem a little big. Also don't forget about the other parts of the fuel system, regulator, filters, rail, lines, and pump.

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

[barefootbonzai]

You're definitely over killing bro. For NA application, 99% of the time your stock injectors will hold fine.

[barefootbonzai]

that's interesting. according to the person that tunes my car, his never seen an NA car his tunned to need injector size increase.

I'm still using my stock injectors on my setup as well, no issues.

[Slow96GSR]

It also depends on what else you have done to the fuel system. If you decrease the flow restriction of the fuel system, it will work at a higher efficiency. You can run stock injectors but with the increase of air in to the block with the pistons and built head you’re going to want more fuel. This is why you need to calculate everything. Too much fuel and you’ll wash the cylinders and have to redo the bottom end as nothing will seal right. 440's are too big but 290-310 should be plenty but you'll want a pressure regulator, rail, and maybe a pump.

[Waggy]

Interesting input here guys - thanks very much. I thought 440cc were slightly too big, but I am getting an FPR, Fuel Rail and Walbro Pump, so I thought that with these it would be ok, though, I've also heard that running injectors at 50% load or less is bad.

I know who tunes your car Barefoot and I trust him based on what I've read, so that was good info - thanks bro.

[TEGNO1]

Hi mate how are ya.... do you know what power your hoping to make, what fuel pressure your going to run, and what ecu are you running, provide that info here and maybe someone can give you the right injectors for your application, also what duty cycle do you want to run them at, i provided some rough formulas in my injectors for sale thread, but you can also try websites such as RC injectors website etc, do your research otherwise you'll end up buying twice if you know what i mean, later.

[saxman]

why on earth are people suggesting to change fuel rails? The stock one will flow WAY more than you're going to ever see if you're questioning the need to upgrade the injectors.

[Perry]

ummm interesting like barefoot said. I'm also running stock injectors aswell and still no issue with the setup I got, but it would be interesting if I get bigger injectors will it make a difference.

[EG5[KRT]]

so how does an adj fuel reg make power ??

increasing fuel pressure to atomise better ??

how do u find out how much duty cycle your injectors r using ??

[Limo]

yeh 440cc sound way too big, im using 440cc's from a GTR on my boosted crx, an they work real good.. tho will need to upgrade soon when i get more work done.

if your looking for something close to 300cc try looking at some of the nissans like i know the C18/RB20/RB26 an EVO's all use top feed, low impendence injectors which are the same as the B series engines and you can usually pick them up pretty cheap.. BUT dont use SR20 or RB25 ones as they wont work. a bigger spacer on the rail and its good to go.

OR another option is to hi-flow them.. havent heard much about it tho.. but once its done, you cant return them to stock.

[EfiOz]

This is a fairly lengthy answer. There is one way to calculate injector size. It goes like this.

1. Make a REALISTIC assumption of how much power your going to make at the flywheel. In this case we'll say 190HP as a maximum (stock 160HP plus some bits).

2. Get an idea of what sort of Brake Specific Fuel Consumption (BSFC) the engine has. For an NA Honda that number will be around 0.4 lb/HP/hour

3. Select a maximum amount of duty cyle to run the injector at. You don't want to go much above 80-85%. How low can you go? We try to run them at 50-60% mainly because it's useless having a fully sequential injection system when the injectors are on for 85% of the time. Your injection phasing (or timing) then becomes soemthing that really matters as you are moving the injection event around.

3. The formula then goes ((Horsepower X BSFC)/number of injectors) / 80%

This will give you a ball park figure for what you need. Putting our "back of the beer coaster" figures in we end up with 23.75 lb/hr of fuel flow or 242cc/min. So yes, the stock injectors are pretty marginal if they are only 240cc/min. You can probably bluff that for a street engine but it wouldn't last 4 laps in a track engine. Running 100% duty cycle on injectors makes them overheat and they become very erratic in operation.

The stock fuel rail has plenty of flow in it.

[Waggy]

Yes we all know D.Dave tunes your car...
Every tuning conversation I have with dave often comes back to Injectors, specifically importance of sizing and maintenance so I know what's up!

you probably have a close to stock engine, so leaning the fuel is what makes power... not rocket science.

Waggy, you will need larger injectors.
If Dave ever visited this place, he'd confirm what both myself and SlowGSR have said.

Ok mate - I trust your judgement and I will most likely be buying slightly bigger injectors anyway, just to be safe (300cc ones by the looks).

I'm not new to techical workings of an engine, however I'm no where near an expert which is why I'm asking. With that said, I don't understand in Barefoot's case how leaning out the fuel can increase the power? I think (and Barefoot, feel free to butt in mate if I'm wrong) he runs a stock-ish B18CR engine (maybe cams only) with ITBs.

I'm aiming for 120-130kw atw.

[EfiOz]

I'm not new to techical workings of an engine, however I'm no where near an expert which is why I'm asking. With that said, I don't understand in Barefoot's case how leaning out the fuel can increase the power? I think (and Barefoot, feel free to butt in mate if I'm wrong) he runs a stock-ish B18CR engine (maybe cams only) with ITBs.

I'm not sure either. I don't how far he's taling about leaning it out. Does he mean leaning it out compared to a standard factory tune? Then he's probably right.

Most Honda's (and anything of a modern engine design) will tolerate running quite lean and still make good power.

AFR by itself is not where the power is. AFR mostly keeps the engine alive and manages the heat inside the chamber.

I'll stand back now and watch the fur fly!

[Slow96GSR]

why on earth are people suggesting to change fuel rails? The stock one will flow WAY more than you're going to ever see if you're questioning the need to upgrade the injectors.

You swap to a bigger bore rail to cut down on turbulence. It isn't something that adds power, just makes things run and flow better which means the pump doesn't have to work as hard. It's a easy thing to bolt on and has little to no drain on the wallet, they run for $50-100USD.

[barefootbonzai]

Yes we all know D.Dave tunes your car...
Every tuning conversation I have with dave often comes back to Injectors, specifically importance of sizing and maintenance so I know what's up!

you probably have a close to stock engine, so leaning the fuel is what makes power... not rocket science.



ummm interesting like barefoot said. I'm also running stock injectors aswell and still no issue with the setup I got, but it would be interesting if I get bigger injectors will it make a difference.

that's another interesting fact there. yes i have a close to standard engine, but perry has a fully built engine from Toda...

yes we all know you know what's up, but you always think people are out to get you, you should really claim the f down. I was just sharing what Dave told me.

[EfiOz]

Yeah, that's what I figured. Every factory Honda tune I see has a big dark stain around the exhaust pipe. :-)

[Perry]

[quote=ProECU;1028878]i wasn't fired up at all. and i'm prefectly calm. Not my problem people read too far into things.

EfiOz - yes, I was referring to a stock factory tune. They're always rich, considering that these motors like to make power anywhere between 12.8 - 13.5.

Barefoot - If Perry has a fully built motor from TODA, then why is he questioning his fuelling requirements? He should just let Adrian take care of it all.

I wasn't really questioning my fuel requirements just curious. Adrian has taken care of my setup very well, with my stock injectors wasnt even maxed out yet.

[Micko]

would there be any difference putting some vtir prelude 290cc ones onto stock b16 engine with just i/h/e & fpr ? or not really until you started doing some internal work?

[MaskedAP1]

try this
http://www.robietherobot.com/storm/fuelinjectorguide.htm

[Micko]

oh your a champ cheers! :D

[Waggy]

Nice !!! +rep for you MaskedAP1!

[ProECU]

a quick search...

http://rywire.com/store/faqdesk_info.php?faqPath=4&faqdesk_id=12&osCsid=7b30a56fcee05b5dec6e410182f6c602

[EfiOz]

try this
http://www.robietherobot.com/storm/fuelinjectorguide.htm

A quick word of warning. The formula's used in this page rely on two figures which are not accurate nor advisable for a Honda application. They assume 90% duty cycle which is really too much for long term injector health and they also assume a 0.5 BSFC which is way too high for a Honda.

[tinkerbell]

FWIW - i am using H22A P&H 340cc injectors on my B20VTEC and run at about 70% duty with ~40psi base fuel pressure...

i could have stuck with the 240cc ones, but at >65psi base fuel pressure and higher duty cycle (which would have strained the fuel system over time)...

BTW - it made the same power on both types of injectors, it is kinda reliability concern in some cases...


EfiOz - what is a BSFC of a honda B series?

[EfiOz]

Down around 0.4, maybe a little higher. Some of the Endyne engines were down around 0.37 at max torque.

[MaskedAP1]

Nice !!! +rep for you MaskedAP1!
thanks:thumbsup:
this one might be help as well



-In order to select the correct size injector for your application, you might wish to use one of the following formulas.
In most cases a naturally aspirated engine will have a B.S.F.C of .50. This means that the engine will use .50 lbs. of fuel per hour for each horsepower it produces. Turbocharged engines will want to be at .60 lbs. per hour or higher.

-Using these numbers as a guideline, you can select the approximate injector size in the following formula for a four cylinder, naturally aspirated engine at 200 bhp.

-Most injectors will max out at 80% duty cycle and this is the accepted industry standard.

-B.S.F.C is brake specific fuel consumption - How much fuel you are using per horsepower per hour


http://www.interestcars.com/masked/files/injector1.gif
The proper injector for this application would be 31 lbs. / hr. or 330 cc / min

To find the HP value of the of the above mentioned injectors use this formula:
http://www.interestcars.com/masked/files/injector2.gif

To find the new FUEL FLOW rate after a fuel pressure change:
http://www.interestcars.com/masked/files/injector3.gif


here is two examples
Example 1
If a 240 CC injector tested at 43.5 PSI is run at 50 PSI. The result would be
http://www.interestcars.com/masked/files/injector4.gif
Example 2
The horsepower value of this injector would increase by the same rate
(X 1.0721), if all other engine management systems remain unchanged
-Flow rate at old pressure
240 cc/Min divided by 10.5 = 22.86 Lb/Hr
-Flow rate at new pressure
257 cc/Min divided by 10.5 = 24.48 Lb/Hr
http://www.interestcars.com/masked/files/injector5.gif
240 cc/Min X 1.0721 = 257 cc/Min
22.86 Lb/Hr X 1.0721 = 24.51 Lb/Hr
36.58 Hp X 1.0721 = 39.22 Hp



note:
To convert cc / min to lbs. / hr. - Divide by 10.5
To convert lbs. / hr to gal. / hr - Divide by 6
To convert cc / min to gal. / hr. - Multiply by .015873

[ProECU]

its ENDYN.

have you had experience with Larry's engines here in Oz or are you quoting some of him engine dyno sheets?

[Slow96GSR]

MaskedAP1, that's the one I posted in a link in my first post. Nice repost! Lol! It's ok, the more we tell people it's there, the more likely they'll remember it.

[MaskedAP1]

MaskedAP1, that's the one I posted in a link in my first post. Nice repost! Lol! It's ok, the more we tell people it's there, the more likely they'll remember it.

my bad man, didnt read the whole thread carefully :o

[tinkerbell]

MaskedAP1, that's the one I posted in a link in my first post.

no, it is not!!!

he is quoting and linking to pics on another site that ripped off the original site link that you posted!!!!

[Slow96GSR]

Well then they should be shot for taking it! No one steals stuff on the internet! Lol!

[EfiOz]

its ENDYN.

have you had experience with Larry's engines here in Oz or are you quoting some of him engine dyno sheets?

I had experience of them in the States. Ben has done a lot of work with him and used to rave about his pistons endlessly.

[EfiOz]

Ben Strader, sole founder and overlord of EFI University (www.efi101.com)

We also saw similar numbers out of the F3 engines from Neil Brown Engineering.

[EfiOz]

His pistons are very nice indeed. Especially for the price.

No, not name dropping, just answering a question is all. I've been work for Ben down here doing his courses for the last couple of years now.

[aus91integra]

EfiOz ... are you Pat by any chance..

[EfiOz]

Yes, I would be.

[aus91integra]

awesome :thumbsup: you have PM