331 question

gtcobra302

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Sep 6, 2005

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Centra Florida

Apr 29, 2008

#1

• Apr 29, 2008

• #1

My buddy has a 331 in his 94 gt. he is running 30 lb injectors which sound big to me. I am running a 100 shot of nitrous and am only running 24 lb injectors. he is running rich. His car is NA, what do you think?

 

donkey_punch

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northern****ingjersey

Apr 29, 2008

#2

• Apr 29, 2008

• #2

check for codes thats the first thing to do, possible O2 sensors need to be replaced, check fuel pressure

 

95WhiteVenom

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#3

• Apr 29, 2008

• #3

Fuel Pressure?

 

gtcobra302

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Apr 29, 2008

#4

• Apr 29, 2008

• #4

Not sure of the fuel pressure, what should it be with the line off?

 

Grn92LX

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#5

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• #5

His injectors are NOT at all to big for a n/a 331. I run 30's on my n/a 347 and they're 100% MAXED out as shown by the duty cycle on my PMS.

How do you know he's running rich?

 

94GTLaserRC

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Apr 29, 2008

#6

• Apr 29, 2008

• #6

Grn92LX said:

His injectors are NOT at all to big for a n/a 331. I run 30's on my n/a 347 and they're 100% MAXED out as shown by the duty cycle on my PMS.

How do you know he's running rich?

Click to expand...

I may have some 36's for you if you want Anyway, I think 24's "can" work in a 331 depending on "supporting cast" and likewise with 30's
RC

 

BlackVert

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#7

• Apr 29, 2008

• #7

30# injectors are not at all too big for a 331. in fact, they may be too small, depending on the heads, cam, and intake. putting down 375 horses at the tires is not unheard of for a 331. at that level, i bet 36 or 42# injectors would be better

 

gtcobra302

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Sep 6, 2005

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Apr 29, 2008

#8

• Apr 29, 2008

• #8

hes got a cobra intake, 80mm mass air, short headers, gt40 iron heads, cold air intake, a receint tune up, msd cap, rotor and coil, ford racing wires, 70mm tbody and spacer. his tail pipes are black and he uses an inordinate amount of gas. he says it is a wolverine b cam, the guy he got it from was supposedly using a 200 shot of nitrous then he took it off when my buddy got it. It also seems to miss when it gets hot.

 

earleys94gt

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Aug 31, 2003

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Apr 29, 2008

#9

• Apr 29, 2008

• #9

The 30's should be okay.

Has he checked the timing on his car?

 

Black95GTS

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Apr 30, 2008

#10

• Apr 30, 2008

• #10

I think he needs to tune his car. 30 pound injectors will most likely be OK with that combo, though I would steup up to 36 pound injectors.

One thing you both need to realize is that the size of the injector has NOTHING to do with how lean or rich the car runs, its all in what the computer tells the injector to do.

Adam

 

5spd GT

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#11

• Apr 30, 2008

• #11

It all depends on the top-end pieces.

An N/A 347 could do fine with stock top-end pieces with a 19 lb. injectors and a 5,500 RPM shiftpoint.

Then, you could have issues with 42 lb injectors shifting at 7,500 RPM with a nice top-end.

The best one I have found to use is from FTI's website:

How to Calculate the Correct Injector Size:

IHP = Ideal Horsepower
NIJ = Number of Injectors Used
IDC = Injector Duty Cycle
BSFC = Brake Specific Fuel Consumption

Example:

300 HP / 8 cylinders = 37.5
37.5 X .50 BSFC = 18.75
18.75 / .80 Duty Cycle = 23.43 lb/hr injector (24 lb/hr is the closest).

This will vary per BSFC you want to run and injector duty cycle preferred.

 

Grn92LX

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#12

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• #12

94GTLaserRC said:

I may have some 36's for you if you want Anyway, I think 24's "can" work in a 331 depending on "supporting cast" and likewise with 30's
RC

Click to expand...

Thanks for the offer but I am going to go 42's when funds allow

 

94GTLaserRC

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#13

• Apr 30, 2008

• #13

Grn92LX said:

Thanks for the offer but I am going to go 42's when funds allow

Click to expand...

The funds may allow for my 36's...Im not going to be listing them for that much...Oh...and I may have a BBK 75mm TB too
RC