How much power are 36# injectors good for? Should I upgrade?

BlueOvalStangGT

Active Member

Oct 27, 2003

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Tampa Florida....USF!!!

Oct 26, 2005

#1

• Oct 26, 2005

• #1

I had a calculator for this type of thing before but I cant seem to find it. My fuels system consists of FRPP 36# injectors, a walboro GSS340 intank pump(255 lph) a Kirban AFPR and I guess ill throw in that I have a tweecer as well(I think you can do something injector wise with it, sorry for me being a newb). If I remember correctly, im gonna be maxing these things out soon. I have a Vortech S-trim putting out about 11 psi, Trickflow heads, trick flow stage 1 cam on a rebuilt stock shortblock. Im hoping for ~450 hp which shouldnt be a problem. Will my 36r's be good or should I upgrade? My freind is gonna be selling a Pro M 77 mm MAF and 42# injectors soon and I could probably get that for cheap and then sell my maf (75 MM Pro-M) and my injectors. How much power are the 42's good for? I think im done with the HP bug for a while now, unless I get a meth inj. kit. I need to start saving for a place to stay and then upgrade my tranny/suspension.

 

Joes95GT

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Jan 23, 2003

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Delaware

Oct 26, 2005

#2

• Oct 26, 2005

• #2

You're going to have an EASY 500-525 FWHP. This is where the power needs to be calculated since it's what the motor sees.

500 HP/8 cyl. = 62.5 HP/cyl. Take this number and multiply it by the BSFC that you want to run the injector at. Most say 0.5 is safe, some will say you can go up to 0.7. We'll say 0.5 because it seems to be the industry standard for the most part...

62.5 * 0.5 = 31.25 lbs/hr. This is assuming that you run the injector at 100% of it's duty cycle, which is never a good idea...

31.25 * 120% = 37.5 lbs/hr.. You'll be good with 500 horsepower, just turn the FP up a tad.

At 550 FWHP, you'll need the 42's (41.25). It probably wouldn't be a bad idea to buy the MAF and 42's from your buddy he sells them. Just the MAF swap would be worth a few more horsepower and the injectors would be a good back-up.

Joe

 

bjl95mustang

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Oct 26, 2005

#3

• Oct 26, 2005

• #3

I would get the 42's and maf.

 

20new5.0

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Sep 16, 2005

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Camarillo, CA

Oct 26, 2005

#4

• Oct 26, 2005

• #4

I would go with the injectors, your on the wire. you could problebly get away with 36's, but the rule of thumb for blowers is that you can just give them as much fuel as you can!

 

final5-0

Mustang Master

Apr 6, 2003

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DFW Texas

Oct 26, 2005

#5

• Oct 26, 2005

• #5

I'd go for the 42's and IMHO, his maf is better than your bullet.

Grady

 

WhiteDevil

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Feb 4, 2003

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Oct 26, 2005

#6

• Oct 26, 2005

• #6

BlueOvalStangGT said:

I have a tweecer as well(I think you can do something injector wise with it, sorry for me being a newb).

Click to expand...

Come on now we had talked about this a few times Injector slopes, MAF Curve, Stabiled_fuel_OL they are all for your fuel system.

 

Grn92LX

Fidanza Man!

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Oct 26, 2005

#7

• Oct 26, 2005

• #7

42's would be fine, 50's would be ideal.

 

BlueOvalStangGT

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Oct 27, 2003

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Tampa Florida....USF!!!

Oct 26, 2005

#8

• Oct 26, 2005

• #8

Grn92LX said:

42's would be fine, 50's would be ideal.

Click to expand...

Thats another thing ive been thinking of, upgrade for later use. But my block is gonna be on its limit soon so 50s probably arent neccesary until I do upgrade my block. I think im gonna do it just for the sake of his maf. Ive always heard bad things of the 75mm which is why I think my car runs so ****ty. Thanks guys, imma grab them from him now,

 

DarkProphet

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Aug 19, 2002

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Quakertown, PA

Oct 26, 2005

#9

• Oct 26, 2005

• #9

Not to highjack this thread, but im wondering the same thing. I know my 36's were fine with my stock heads an 9#s of boost, but will they be ok with the gt40x heads and b cam along with the boost? using the calculations I should be fine, though I have NO idea how much hp this combo should be good for.

 

4Jenna

Founding Member

Sep 12, 2001

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AZ

Oct 27, 2005

#10

• Oct 27, 2005

• #10

I went lean at 460rw on 36s

 

MattZ281LE

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Feb 6, 2000

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Purcellville, Va

Oct 30, 2005

#11

• Oct 30, 2005

• #11

I went 100% duty cycle and lean at 385 rwhp 5500 rpm. Best to go to 42# and lightning meter.

And remember its the HP the motor generates. This includes drivetrain,accessory and blower loss. It takes a good bit of energy to turn a blower on the top end and have heard 15-25% loss figures.

Somebody with more blower math experience could give you accurate #'s though.

I think its best to tune a slightly bigger injector down and ensure you can supply the fuel when you need it.

 

final5-0

Mustang Master

Apr 6, 2003

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DFW Texas

Oct 30, 2005

#12

• Oct 30, 2005

• #12

MattZ281LE said:

I went 100% duty cycle and lean at 385 rwhp 5500 rpm. Best to go to 42# and lightning meter.

And remember its the HP the motor generates. This includes drivetrain,accessory and blower loss. It takes a good bit of energy to turn a blower on the top end and have heard 15-25% loss figures.

Somebody with more blower math experience could give you accurate #'s though.

Click to expand...

You bring up some very good points!

I think its best to tune a slightly bigger injector down and ensure you can supply the fuel when you need it.

Click to expand...

I know ...... I think ...... like you think

Grady