stock itr injectors = 240cc/min

stock prelude injectors = 290cc/min

celica gts injectors = 310cc/min

dsm injectors = 450cc/min (same harness as honda's)


Now it seems that many feel the stock fuel pump and bigger injectors is better than smaller injectors and pushing higher pressures..... (See hondata for more info on this.)

It seems that when tuning with a vafc, you can only add about 15% fuel before it won't accept a raise anymore..... You can add more on the screen, but you won't actually be raising it any more - simply because of the MAP sensor fooling and crap.

Well, I did some math and it looks like prelude injectors are 20% bigger than the itr injectors. 310's are 29% bigger, and 450's are 87.5% bigger.....

So if you are tuning with a vafc and need to raise to 20% on the wot settings, you could simply keep stock fuel pressure (and save the stock fuel pump) - and adding prelude injectors would enable you to put your vafc back at zero for those points where you needed to add 20% fuel..... Weird, huh?

 

Incorrect.

The AFC/SFCs are modifying percentage of map voltage not
fuel. So increasing 15% is increasing 15% of whatever the current
voltage is.

 

Interesting...just learned something new about how those little gadgets work.

 

I've always heard that it is better to run a little biger injector and have the vafc or what ever full controll system you are using to turn it down a little. But this might have been for fp, and not injector cycle... <shrug>

 

you can only reduce fuel so much because you are not affecting the fuel maps
at all. You are just telling the ecu to go to another part of the map.

 

Then what is the max % you can lean it out with the VAFC?

So the best would be use a FPR to adjust the fuel pressure, then use VAFC to fine tune it at different point.

 

max would be -50

that is the method i have been recommending all along.

 

Steve should I put in my 370cc in before hondata, or will my car run like crap? without the hondata tunning the Fuel?

 

.....thanks for the help earlier steve.

Now that basically brings me back to my intended question:

310's are the biggest that the stock ecu can reasonably handle - even with piggyback controls. 290's are bigger than stock too.

I'm wondering if somebody wanted to just slap them on and see what they'll do - what would the outcome be? (at stock fuel pressure, and then of course tuned for fuel psi, gear changes, vafc leaning, timing, etc...)

I'm guessing the 290's will richen up everything across the board. 310's more so, etc... A different route than raising fuel pressure... I guess I chose a bad example - but let's say at 45psi you're still lean with stock injectors. Dropping in 290's will have the same effect as raising fuel pressure by 20%, right? Still at 45psi.....

 

I actually called RC Engineering when I was deciding on injectors. They say that a Honda ECU can make a car idle (not smoothly) at 30% over stock.

Anything more, and you need some sort of regulator.

 

what about a aftermarket fuel pump, is that benifitial?

 

I wouldnt put those in without the hondata.

You probably wont need a new pump either unless yours is going bad.

 

.....which is 312cc/min. But who makes 312 injectors? So most settle for 310's on stock ecu.....

 

or you can look into some Accel injectors if you're on a budget.

They come in packs of 8 injectors(meant for V8), and they are available in hi or low impedance. OBD1 injector clips fit fine.

The 30lb/hr injector set sells for $249.99 at http://www.jegs.com
30lb/hr = 315cc

Other sizes they have are
32lb/hr = 336cc $282.99/pack
36lb/hr = 378cc $389.99/pack
40lb/hr = 420cc $419.99/pack

....just an option to consider. The 315cc ones end up costing $31.24 each.

 

Now THAT is what I was looking for!

ooh, I found a link:

http://www.jegs.com/cgi-bin/ncommerc...075&prmenbr=76

Now, where did I leave that formula to convert from lb/hr to cc/min..... *goes to search* .....just wondering what 26lb/hr is. Thanks Mike!

 

I found something else that answers a LOT of my questions lately:

http://www.3si.org/member-home/jluci...-fuel-flow.htm


It even gives you some cool calculators for proper injector sizing, etc.....

 

I just multiply the lb/hr by 10.5 and that's a good rough estimate.