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Old 05-25-2010, 12:47 AM   #1
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Default Tuning for Bigger Injectors, why?

When I installed my MSPNP I installed larger 320cc injectors. However I never changed the "req fuel" settings so it still thinks I have the stock ones in.

I've tuned my car pretty well and I'm happy with it now (other than the occasional adjustment to idle or cruise). I recently changed the req fuel to the correct number for my injectors and the car went very lean, undrivable. I also noticed that my req fuel for the stock ones is ~9.2 and for the 320cc's its 13.2. If I understand correctly and req fuel stands for "required fuel" wouldn't the larger injectors have a smaller number as they release more fuel?

So is there any advantages to changing my req fuel for the bigger injectors and starting over tuning my VE tables?

Thanks and sorry if my question is a bit confusing.
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Old 05-25-2010, 08:02 AM   #2
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You have the req_fuel number backwards, oem injectors are around 13, my 600cc injecors are around 5...
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Old 05-25-2010, 11:40 AM   #3
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yeah the bigger the injectors, the smaller the req fuel

the req fuel setting doesnt "really" matter, the idea is to allow scaleability of your maps if you change injector size. on the ms2 extra code the cranking settings are even scaled to the req fuel (they used to be straight up pw settings)
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Old 05-25-2010, 01:27 PM   #4
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Well I went ahead and set req_fuel at the proper number and did some street tuning this morning. I havent noticed any real difference other than not feeling like I've forgotten something.
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Old 05-25-2010, 02:16 PM   #5
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I am pretty sure it's just a scaling factor. If it was 10 and you set it to 1, you could multiply all of your VE values by 10 and get the same tune.
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Old 05-25-2010, 02:28 PM   #6
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Quote:
Originally Posted by kday View Post
I am pretty sure it's just a scaling factor. If it was 10 and you set it to 1, you could multiply all of your VE values by 10 and get the same tune.
Correct, but IIRC there is a limit. For some reason I have the number 255 sticking in my head.
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Old 05-25-2010, 02:30 PM   #7
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Quote:
Originally Posted by D.dutton9512 View Post
So is there any advantages to changing my req fuel for the bigger injectors and starting over tuning my VE tables?
No.

Req_Fuel is just a multiplier. You can just as easily go from one injector size to another by leaving it alone and re-scaling the whole VE table, which is essentially what you did.

The only real constraint is that the VE table has a maximum per-cell value (255) so if you find that you're approaching that value, you'll need to scale up Req_Fuel. Conversely, you don't want Req_Fuel to be so large that all of your VE values are very small- this sacrifices resolution.
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