shep28

iTrader: (4)

I have a 99' z and need to scale my HP IFR table for scoggins svo 30lb. red top injectors. The 99s have 26pounders.

So far, I have been given the full spectrum of scaling figures from tuners on various sites.

Which one is the correct scaling figure for my application?

139%

123%

115%

135%

138%

I have no idea at this point and am totally confused

John_D.

iTrader: (2)

Here's how I'd go about it...

First get both injectors at the same psi rating.
The ls1 injectors are rated at 4 bar, the SVO are rated at 3 bar.
4 bar is 4x14.5= 58.0psi.
3 bar is 3x14.5= 43.5psi.

The formula to convert ratings for pressure is:
sqrt(new psi / old psi) x old rate = new rate

Bring the 4 bar rating down to a 3 bar rating:
sqrt(43.5 / 58) x 26 = 22.51 for the ls1 injectors, rated the same as everybody else.

Ok, we're in the home stretch now....

A 30lb injector is 7.48 bigger than a 22.51. (30 - 22.51 = 7.48)

7.48/22.51 = .33

So the 30's are 33% bigger than the 22.51's

Based on that, I'd bump the ifr tables by 33%.

shep28

iTrader: (4)

thnx.

John_D.

iTrader: (2)

As if you needed a 6th number to go with the 5 you already had...

But maybe seeing the math helps.

pkincy

iTrader: (1)

The math is good and the scaling factor should be 1.33 to 1.35 based on the data that is discussed here.

However I don't agree with the common notion that the SVOs are rated at 3 bar. I believe they are rated at 39 psi which would give them a 32 # flow rate at 3 bar and a 37 at 4 bar....which would make the scalar a 1.42 factor.

BTW, either number will get you close enough for your initial tune, so don't be confused by the small difference.

First, the common notion that most injectors are rated at 3 bar is very incorrect.

The vast majority of injectors are rated at many different pressures. Most of Ford's OEM injectors are rated at between 30 and 39 psi not 43.5 psi.

Several years ago the accepted notion was that the Ford injectors were rated at 39 lbs. Thus most of us old timers have the SVO 30# injectors entered as 32 # flows in our LT1 pcms (GM does use 3 bar as a rating pressure in the LT1 injectors and presumably others).

My other computer has a link in it to a compendium of OEM injectors (the link is http://users.erols.com/srweiss/tableifc.htm) (hundreds of variations) from all manufacturers with their part nos, their flow rate and the pressures at which that flow rate is rated. And less than 5% of the injectors are rated at 3 bar. Unfortunately the SVO brand of Ford injectors are not listed and hence no rating pressure is available for them from that link. Do look at it however as you will be amazed by the variety of rating pressures within the same manufacture. For instance the Ford had 2 different part nos for the injectos in the 3.8L supercharged SC motor. One part nos was rated at 39.15 psi and the other at 43.5. The 30# Ford injectos in the 2.3 L turbo motor were rated at 37#s.

A tuning fact is that you start your scaling by some reasonable factor but use the LTFTs, (STFTs for those that are really good as well as somewhat impatient) and wide band readings to finalize the injector flow rate.

If anyone really knows what pressure the SVO injectors are rated at please let me know.

Perry

tici

iTrader: (1)

Why not make a nice long scan, record where you are, then install the injectors and adjust them th have the same result?
The calculation stuff worked fine for me but I went from 28 to 36 Bosch: same pressure rating, same product.

WAHUSKER

iTrader: (4)

James @ RWTD told me SVO 30s run at 36lbs on our cars, while Accel 30s run at 34.5lbs. If that is correct (& it worked for my Accels) then 1.35% is correct. (36 / 26.6 = 1.353)

pkincy

iTrader: (1)

I appreciate that information. The Accels are clearly rated at 3 bar. And this tends to support my feeling (from several years ago) that the SVOs are really rated at 39 psi not 43.5 psi.

Perry

John_D.

iTrader: (2)

Interesting stuff...

I didn't know about all the different variations in test pressures.