just curious how much power can stock 305 injectors, throttle body, computer, fuel pressure, and fuel pump support? Ive searched but havent found any answers

 

Stock stock? Completely stock? About 220 HP max'd out. About 188 HP keeping the injector DC% reasonable.

RBob.

 

is that 188 rwhp or fwhp?

 

I read a while back that its about 220fwhp with stock injectors at 15 psi.

 

With my only mods being14x3 breather, 15 lb fp, and no muffler I dynod 176rwhp.

 

i sprayed the ***** of my engine , stock EVERYTHING, cept for the 14x3 aircleaner, and the nitrous, and et' tells me somewhere in the 310hp range.

so id say north of 300hp if you went all out with the nitrous.

 

lo3? how did u get 15lbs fp?

 

I dont understand... What is there limiting the LO3 to such low HP numbers? I thought the stock TB could support like 300 HP or something? Is it just the injectors??

 

The problem is stock fueling. Stock fuel pressure is ~12 PSI. If you want any more than that you need to change the fuel pump. At that pressure the L03 injectors can't support much more than the stock 170hp. I run a bolt-on L05 with tuning and my fuel injectors are getting up over 95% duty cycle by about 4200 RPM on stock 12 PSI. It's really the fuel pressure that is limiting.

Its when you run fuel pressure up to between 15 and 20 PSI or more and/or run larger injectors that you can support 300 - maybe 400 horsepower with tuning.

 

68# police car injectors at 45 psi will support about 485 FWHP keeping the duty cycle at a reasonable 80%.

The stock throttle body flows reasonably well to 300 hp. With ultimate TBI mods and a pod spacer, it flows decently to about 320 FWHP. Above that a Bored out TBI or a 454 TBI is needed.

 

With an adjustable fuel pressure regulator.

 

That would be engine HP (fwhp). What I did was to take the 55 #/hr that the injectors flow (all stock), multiply by 2 for 2 injectors, then divide by 0.50 for the BSFC (or just multiply 55 * 4).

That gives 220 HP, flywheel.

Then to factor in the DC% at 85, multiply 220 by .85. That gives the 188 HP.

RBob.

 

check this out:

it takes into account DC, BSFC, FP, CID, inj size in lbs or grams and calc's BPW.

http://www.users.bigpond.net.au/ben_...ctorsizing.xls

 

do you have to get adjustable fpr or can u just put a different spring in the stock one for more pressure.

 

You can change the springs in the stock FPR for more pressure. Can also make it adjustable. Although a particular spring will only have a certain range of adjustability.

RBob.

 

I know it works in theory, and I also know you've done some pretty radical stuff with tbi. Whats the highest fwhp that has ever been proven with tbi?

 

443 RWHP.

 

Wow! Thats impressive, is that naturally aspirated?

 

were can u get these springs what ones do u recommend i would like to see 15psi outof the stock pump if possible

 

Top Down Solutions sells a spring one tick stronger. From there one needs a GM 7.4L TBI high pressure spring >20 lbs.

Stock pump may not be able to hold much more than 12 under load?

 

i seen that it says for vacuum adjustable fuel pressure regulator

 

It would work for that application too. I run a VAFPR but I am not using that feature(yet). I have the stronger spring of two in Aero unit set to 19 lbs. VAFPR offers max pressure at WOT and reduces the FP to improve the idle pulse width(larger pulse width).

 

Ok, so where do you find (or how do you make) a VAFPR?

 

Aeromotive sells a nice one

 

Bought a box-O-springs at Home Despot, or someplace. Played mix-N-match 'till I got a measured 25 PSI. Works great !
Needed a booster pump, as the stock pump contains a blow-off at about 14 PSI.

 

GM "used" to sell one. I hear it is discontinued? I bet they are available somewhere? Try Ebay. I have the part # at home. I would think any manufacturer sells their own aftermarket VAFPR. Mine is Aeromotive unit. Very nice but a bit costly. I chose it since it offers two springs 10-20 and 20-60.