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View Full Version : b20a/a20a intake, fuel rail, injectors etc



Versanick
10-05-2003, 11:47 PM
This is continued from another thread, where, upon this post, I started to get real technical (so I moved it here)...

http://www.3geez.com/showthread.php?s=&threadid=24663

I'll probably wind up with an 88-89 manifold and get it ported out where it meets the head, to some extent.

It's my understanding of injectors that most Honda injectors, as long as they're peak-and-hold style, will fit and work. My question is more related to the fuel rail, but I can actually assume that that will be the same too. I suppose the whole thread was in regards to it, and I wound up logically answering my own inquiry.

I suppose that I'd like to throw it in the direction of performance fuel injection upgrading without breaking the bank.

My direction, again, was a h22a1 fuel rail and fuel injector setup. If my source is correct, these injectors are much more free-flowing than most other Honda injectors (most are in the neighborhood of 240cc/min, like the factory b20a injectors)...

The h22a1's are said to be 345cc/min (huge for honda motors around its size/power, but makes sense in the horsepower formula for injectors).

(injector size) x (.8 duty cycle)
-------------------------------------
(.50 brake specific fuel consumption, slightly higher w/forced induction)

(multiply formula times four, for 4 injectors)

If you input a 240cc injector, 80% duty cycle (.8), and .5 (assuming an average naturally-aspirated motor), times 4 injectors

You can reach an average rich-running horsepower rating. For the factory b20a injectors, this winds up being 145.5hp, with the fuel pressure at the rail being 43.5 psi.

By getting a bigger fuel pump, or fuel pressure riser, you can move your fuel pressure to 50 psi, and make 157 rich-running hp. You're still running relatively lean with the 160hp b20a.

Thus the problem. Now let's put 270cc injectors in. We can now have 163.5 rich-running bhp at the fly without changing the fuel pressure.

Now we encounter another problem. The 270cc injectors will probably run you over $300 new from RC. Since you didn't increase your pressure any, but released some more by increasing cc/min, your peak torque may drop its occurrence in RPM (even if it's higher), and you won't be able to make much of any power past the factory redline.

Now you're in my shoes.
Ported head, bullfrog cams, 3-angle valve job, header to muffler exhaust, AEM external intake... and a factory 86 intake restricting air flow.

Definitely way more than 160hp, with 240cc injectors. And restrictive intake. Running lean? Definitely. What's the problem? The intake is quite restrictive to be running lean. Not that running lean is good.

The intake needs to be replaced to free up air flow (as well as porting or at least cleaning the throttle body), and WAY bigger injectors need apply.

If h22a1 injectors are only 310cc (which I've read somewhere less reliable), I could raise my fuel pressure (to let's say 55 psig at the rail), and now the formula shows that 365cc/min injectors will run me plenty rich. If my brake specific is less than .5 (which it very well may be), 335-350cc/min injectors would be perfect.

That brings me to the other source, ACCEL's web site, which says that the h22a1 (and none of the other h-series motors) use injectors that flow 345cc/min. This will help accounting for the fact that it has a lot more power than the h-series motors around it, without changing much else about the motor.

This would make 93-96 Prelude Si VTEC injectors optimal for my setup, and definitely an excellent option for anyone else with an a20/b20 who wants to run a bit richer.

Looking to use a small amount of nitrous (25-shot) later on, I might want to be running a little rich myself. Taking all into account, I could very well be doing that after raising the pressure and using h22 injectors, as long as they fit.

Does anyone think I'm absolutely insane and out of my gord, or am I being somewhat reasonable?

I love my car and want to do what's right. Will the h22 stuff fit on an 88-89 intake or am I smoking crack?

haha
thanks
paul

Versanick
10-06-2003, 08:32 PM
Anyone have an extra crack stem? Cuz I'm goin to town. I guess.

Versanick
10-06-2003, 08:50 PM
While, I'm on the topic, and everyone's paying attention, here's a GREAT technical link involving fuel injectoion.

http://www.weebls-stuff.com/data/toons/badger.swf

I might as well have written the lyrics to this song in the first post...

lol

you know I'm just kidding around
I love you guys

paul

Gregg86DX
10-21-2003, 06:58 AM
This part confuses me:

"If you input a 240cc injector, 80% duty cycle (.8), and .5 (assuming an average naturally-aspirated motor), times 4 injectors

You can reach an average rich-running horsepower rating. For the factory b20a injectors, this winds up being 145.5hp, with the fuel pressure at the rail being 43.5 psi.

By getting a bigger fuel pump, or fuel pressure riser, you can move your fuel pressure to 50 psi, and make 157 rich-running hp. You're still running relatively lean with the 160hp b20a."



If I am understanding you, then the factory B20A injectors should barely work. Why would the factory injectors on a 160hp motor be so undersized? I see you chose 80% duty cycle, any reason why you are stopping there? How do things look if you push that up to 90%+?

Also, I am curious what kind of fuel control computer you are planning to use. I just picked up a B20A for my '86DX and I am still trying to figure out what path to go for the fuel system. My motor came with all the FI stuff, but no ECU.

Gregg

Versanick
10-23-2003, 09:36 PM
The ECU is from the original motor. I think the fuel map was re-done. Runs crazy amounts of rich.

I really don't know how to push up the duty cycle. I know the fuel pressure is supposed to rise with RPM anyway, so the injectors really put out more or less than 240cc/min anyway (given)

I was just using a formula I found on rc's website. The injectors are probably sized to keep the car relatively lean anyway. All hondas run pretty lean from factory.... just not this one lol.

I maybe should just get a stillen fuel riser, that can go up to 60psi... and raise the total fuel pressure at high revs by 10 pounds... maybe if it maxes at 40, to max it at 50, to make power through 7500...

right now the torque drops off huge after 6300-6400...

you can tell me I'm wrong... but you didn't answer my question I don't think lol... right? I have no idea.

this is all theoretical to me. I'm asking for someone to tell me how it is.

thanks dude
peace

Gregg86DX
10-23-2003, 10:16 PM
Lol, well, the main question I read was:

"Does anyone think I'm absolutely insane and out of my gord, or am I being somewhat reasonable?"

And I am hesitant to answer that.
:tongue:

But I think you are on the right track. There is no question you'll need bigger injectors as the HP climbs. I am a bit ignorant on how the Honda FI systems work. I have played around a bit with Ford EFI and they use a Mass Air Sensor and a computer calibrated to the size of the injector to manage the fuel curve. All the domestic stuff is measured in lbs/hour, however and I don't know the formula to convert.
I need to get more educated on the Honda FI system to really talk intelligently about this topic. The biggest concern I have seen when changing fuel injectors is making sure the computer can figure out the correct pulse width for firing the injector. On the Fords, if you just slap a bigger injector in there, you run way rich since the computer is firing the injector too long with the higher fuel flow.
I'm not sure how the Honda's determine how long to fire the injector, but if it is similar, then you'll need to take that into account.

Gregg