Interesting article on AFR 165 heads

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Interesting article on AFR 165 heads

Reply #15 – November 09, 2006, 04:06:33 PM

Quote from: JeremyB;112535

Scientific Method. I shouldn't have put into acronym form.

Thanks for the tip, I use SM in my job.

I am able to get the information I need out of this test despite the lack of SM. Every instance you sited as error has a rationalization to me that still makes the test valid.

Interesting article on AFR 165 heads

Reply #16 – November 09, 2006, 04:20:02 PM

Testing Hi-Po parts is tough path to walk... Sure you can slap a set of AFR(or any other mfgr) heads, and not make any other changes, but why??? The stock Stang headers/exaust system chokes out approx 20 hp. and probably 50-60 of what the AFRs could delever. I'd say 99.9% of the buyers of such heads probably already have a modified exaust or are doing so with the head install... Same deal on the top end, most guys buy all the smaller priced goodies, before they spring for that "good" set of heads...

Just for a figure, without any other mods I'd say the average "good" heads would give 25-30hp...

Interesting article on AFR 165 heads

Reply #17 – November 09, 2006, 06:58:12 PM

Quote

You'd need a bigger pump though. The SO pump is rated in at 65 LPH and is pretty much maxed out at the stock fuel pressure with the 14 pounders.

Don't HOs use the same 39psi setting? People who have done the stock HO conversion have used the stock pump no problem right? Just making sure:cool:

Interesting article on AFR 165 heads

Reply #18 – November 09, 2006, 07:33:30 PM

The stock fuel pressure is the same, yes but as you increase pressure injectors flow at a higher rate (see attached chart).

Keep in mind that as you increase line pressure making injectors act larger it has the reverse effect on a pump. Tht is the pump will flow less. All flow ratings are calculated at about 2 bar above atmospheric pressure or around 40 psi.

Eight 14 pound injectors will require a pump that flows a minimum of 112 pounds per hour (higher if you increase fuel pressure). The stock 65 LPH pump converts to 17.105 gallons per hour. A gallon of gas weighs 6.3 pounds so you're talking 107 pounds per hour. This number is very close and is good for the 14 pounders because they will never see full duty cycle on a bone stock SO, but any increase over say 5 psi pressure on the stock 14's or ANY injector upgrade will require a larger pump.

Interesting article on AFR 165 heads

Reply #19 – November 09, 2006, 07:41:15 PM

So since I'm droping a SD 5.0 HO into my car in the spring I'm going to need a new fuel pump? I though I could just use the stocker since I wasn't really going to have any mods besides GT-40 iron heads. Or will I be ok? CoolCats dosen't mention anything about having to change the pump if you already have a 5.0 car. If I do need a new one what is one that works with the tank so I can get all the fuel out. I know people have some problems with Mustang ones because the tank is differnt (ie they can't go below 1/2 tank because the pump cant pick up the gas).

Interesting article on AFR 165 heads

Reply #20 – November 09, 2006, 07:55:51 PM

You're gonna need a bigger pump, especially if you're gonna go with GT-40 heads that flow better and hence will most likely need more fuel to operate to their full potential.

Interesting article on AFR 165 heads

Reply #21 – November 09, 2006, 09:29:53 PM

Nuts. I swore that people were running HO converted cars with the stock pump. Oh well.

Interesting article on AFR 165 heads

Reply #22 – November 09, 2006, 09:31:26 PM

Quote from: Paul Flockhart;112582

The stock fuel pressure is the same, yes but as you increase pressure injectors flow at a higher rate (see attached chart).

Erm, not that I want to sound like a total doofus, but I can't seem to find any attachment....

Interesting article on AFR 165 heads

Reply #23 – November 10, 2006, 05:20:20 PM

You're not the doofus, I am.....totally forgot to add it.....Here goes:

Interesting article on AFR 165 heads

Reply #24 – November 11, 2006, 12:29:16 PM

Interesting. So it looks like the size change of the injector is directly proportional to the amount of power supported... ie: double the injector size = double the power supported.

Pressure, on the other hand, not quite the same. It appears that doubling the pressure increases the power supported by the square root of 2, with some slight variations... basing on the 40 vs 80 PSI numbers, as well as looking at 50 vs 100 PSI, it comes to anywhere form 1.407 to 1.416. Square root of 2 seems a good general rule.

But, given that 14 divided by 19 equals .73684, we can pretty much take the first column and multiply by that factor to figure out what the stockers would support at various pressures.

Thus, by my math, using the 19lb numbers as a basis:

Code: [Select]


[B]Fuel PSI[/B]    [B]14 lb[/B]
40 psi      210 hp
50 psi      234 hp
60 psi      256 hp
70 psi      276 hp
80 psi      295 hp
90 psi      313 hp
100 psi     330 hp

Hm . . even at stock pressure of 40 psi (er, *is* that the stock pressure?), the little 14 pounders can handle a reasonable amount of power.

I assume the numbers from the chart you posted are assuming 8 injectors?

Interesting article on AFR 165 heads

Reply #25 – November 11, 2006, 01:21:42 PM

The chart does assume 8 injectors.

Interesting article on AFR 165 heads

Reply #26 – November 11, 2006, 02:31:37 PM

Hmm so according to the chart I should be fine at the stock fuel pressure of 40 lbs/hr. My combo should make about 240 hp.