Required fuel settings...
 

So I still have my stock injectors in there. My required fuel is 13.2. If this isn't correct, what should it be for using stock injectors? I am probably going to swap in my 460's within a week. What is the required fuel setting for 460's?
To figure there out, do I just use the required fuel calculator? If so, what do I type in for air-fuel ratio?

I use the calculator. For AFR, I type 12:1 or 12.5:1. No idea what AFR I should enter there. Might look that up. :)

13.2 is about right for the default DIY maps on stock injectors.

Is your VE table is tuned reasonably well with the stock injectors presently? If so, frack the calculator. You've got 240cc injectors, and you're moving up to 440s. 240/440 = 0.54, so 0.54 * 13.2 = 7.2

So I should have my 460's back from the injector place by Friday. My current required fuel with my stock injectors is 13.2. What are you guys who are running 460's using? Should I use the calculator and enter 460cc's in the injector part, and 12:1 in the AFR part? Why 12:1? What is the significance with that magic number? I just want to swap these in there and enter a number that works, and drive this thing...

No BOOOOM!

3.5ms.

But I'm cheating. The native resolution of MSNS-HR is 35 microseconds, so within my VE table, every increment of 1 is exactly equal to the minimum step size of the fuel calculation. Just had to scale my VE table up a bit.


I'm going to say this one last time. The ReqFuel calculator is intended to give you a rough starting value the very first time, before you begin tuning your VE table. Once your VE table is tuned, if you change injectors, just manually scale the ReqFuel value by the proportional difference between the injectors.

Interesting, i need to go do this then. I just installed my 550s last night and simply used the calculator. I'd imagine that when I through the turbo on this weekend (hopefully) i need to do change to 12.0 instead of the 14.7 thats in there right now.

Also to the OP, I dont know about your 460s, but my 550s are much louder then my stock injectors. I can hear thim in the cabin at idle...pretty weird. So dont be too surprised initially when they seem way louder than you're used to...I thought something was wrong til I read about it.

You rock Joe.

You're missing the point of how the calculator works.

Probably, this is the first time i've even messed with it. But VE is not tuned for anything boosted yet. Does this not make a difference?

all the AFR number does is add a mulitpler to the REQ_FUEL calculation.

you could run 13 req-fuel and still run 550cc injectors, so long as you scale your ve table correctly.

the best way to change injectors is to forgo the calculator and simply multiply the current req_fuel value by the % difference of the two injectors.

if you map was scaled at 13.5 afr, and you went to 550s and used 12.5 afr, the math is now wrong for your req_fuel value.

So stock injectors in my 99 are 240cc? Since I am going to 460cc's I need to do the math like this: 240/460 = 0.52, so 0.52 * 13.2 = 6.887...therefore I should use 6.9 as the required fuel?
Correct me if I'm wrong.

sounds correct to me.

Sorry for being curt earlier. Here's the deal.

I know that your boosted cells are not tuned right now, but I'm assuming your non-boosted cells are.

If you re-run the calc with different AFR targets, you're going to screw up the part of the VE table that you've already tuned.

If you change Req_Fuel manually by multiplying the current Req_Fuel against the size difference between the old and new injectors then the portion of the VE table you've already used will still be usable.

Its all good, reading comprehension > me...especially when I just wake up.

Anyway, I did the math for 550s and what I got with the calculator is just fine...its stayng.

So I installed a 460cc injector and 36-1 trigger wheel. Now I have to run my car down to req fuel 2ms. That seems to be very low. Please help. I will post tune and log in 24 hours

I see in your signature that you're running rx8 460's. What do these injectors look like/ what is the part number? I think you mean either rx7 460's or rx8 425's.

I mean rx8 425. I will change that

Necro much?

Let's take some of the mystery out. "Req. Fuel" is just a number. Don't get too hung up on it. The fuel injected into your engine is:

"Req Fuel" x VE Table Lookup x Applicable Enrichments

You would like to have a "Req Fuel" that allows the numbers in your VE Table to get relatively large while still staying comfortably below the maximum (255). That way you get the most fueling resolution possible out of your MS. If starting from an untuned state:

1. Take whatever "Req Fuel" that MS's calculator gives you. Don't sweat the details. It will be conservative. I've usually found that this calculated value ends up giving maximums in the low 100s after I've tuned my VE table.

2. Tune away. VEAL is awesome.

3. Take a look at the tuned values in your VE table. You would like the highest values to be in the low 200s. To get this, do the following:

"New Req Fuel" = "Old Req Fuel" x "Largest Old VE Table Value" / 200
"New VE Table" = "Old VE Table" x 200 / "Largest Old VE Table Value"

4. Now go do some more tuning to further refine. You'll end up with a car that runs a bit better from finer fuel control.

5. Win at life!!

here's what you should have done:

old injector / new injector * req_fuel

Thanks for the help. My car needed more tuning. Also my VE map needed some interpretation. I didn't realize how important that is. it is much smoother now. happy Thanksgiving

..

what does that mean?

Nothing. Just wrote something that I later thought wasn't correct.

So,

(Red top nb1) 240cc / 1000cc * 12.7 (from base map) = 3 (3.04) new req_fuel?

old injector / new injector * req_fuel

Existing req_fuel = 12.7
old = 240
new = 1000
old/new = 0.24
0.24 * 12.7 = 3.048 or 3.05.

So, yes. 3.05 for your req_fuel.
This will leave your existing VE table "close" with the new injectors.

I'm guessing you'll want to VEAL for a bit again, though I've never sized up injectors with an aftermarket ECU before.

The above gets you going with new injectors. After you've tuned a bit, you can follow my procedure to find a better "Req Fuel" and get more resolution out of your VE table.

If you know the dead time for the new injectors, key that in as well. If these are ID injectors, I understand they are supplied with low pulse corrections. That's the least important, but you can research that if you do have the information.

I just redid my VE tables, following Hornet's advice and wow... between that and switching over to sequential injection, the car car feels much smoother now.

Time to go VEAL for a bit and take more advantage of this!

I know this is an old thread and sorry if this is frowned upon but I had a question about the calculation. I too have moved to 1000cc injectors but do you do the calculation with the nb fuel pressure. What I mean is that I bought fuel injector clinic 1000cc injectors that are actually tested at about 969 at 3 bar. At 4 bar which I believe the nb fuel pressure is it shows the flow is 1118 so based on the megasquirt base map do I do old injector/ new injector flow rate at 4 bar and then times it by my base map requires fuel or just use the size flow at 3 bar which is 969?

use the flow rates at 60psi.