# Required fuel settings...

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**1**Slowest Progress Ever

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**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?

To figure there out, do I just use the required fuel calculator? If so, what do I type in for air-fuel ratio?

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**2**To figure there out, do I just use the required fuel calculator? If so, what do I type in for air-fuel ratio?

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**3**Boost Pope

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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

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

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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...

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**6**Boost Pope

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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.

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.

Should I use the calculator and enter 460cc's in the injector part, and 12:1 in the AFR part?

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**7**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.

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.

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.

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**10****Boost Czar**

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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.

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.

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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.

Correct me if I'm wrong.

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**13**Boost Pope

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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.

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**14**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.

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

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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.

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**18**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!!