Ok I posted that after my header installation I got slower. My exhaust is scavanging so much better now that my 24 lb/hr injectors are just not cutting it. I'm running very lean up top in the rpm range.

So I have to get new injectors and need to decide on what size I'm going to need. I was going to get either 30, 36, or 42 Ford SVO injectors. I have thier 24's and they are well priced and perform well too.

I currently have stock heads and I'm running 12 psi of boost. I am going to upgrade to AFR 190 heads soon. So I'd like to get either the 36's or the 42's but am worried that for right now that my car wont run right under normal driving conditions with my stock PROM. If there is going to be a problem I'll run the 30's for now till I get the new heads. Custom chip burns are too much money to get so I dont know about that option.

Any ideas or advice?

 

Well you've got a couple choices

An AFPR
Custom Chip either purchase, or head over to the DYI prom board and learn how to do it yourself (a lot cheaper)
A progammable computer, haltech makes one that is a direct plug in.

BTW at the stock fuel pressure the 24# fuel injectors should be good for 450 hp, so I doubt very much you need to upgrade injectors just yet. Once you get the afr's you'll need 'em but I'd go with 30# units. BTW when you get the afr's you may need to upgrade your supercharger to support the power your engine will be capable of.

 

Anything over 24lbs will need a new chip. I happen to be running 36lb SVOs.

You know Fords stock fuel pressure is 35lbs which is what the injectors are flow rated at. So your 24lb injectors at, our fuel pressure of 45lbs, is actually like a 26lb injector. 30s are like 33s and 36s are like 39s.

BTW I happen to have a set of 30lb SVOs for sale. I only used them for a couple of weeks. Check the classifieds.

 

I already have an AFPR but thought that when I put the blower on with the FMU the AFPR was pretty much voided out.

And I thought the 24's are only good to 350 hp. Cause I was approx 380hp before and am now proabbly over 400.

 

24lbs/hr * 8 injectors * .9 duty cycle is just under 173 lbs/hr of fuel. I often read that you assume a BSFC of .55 for a blown engine.

173/.55 = 315 Hp.

 

I didn't do the math, I just used the injector calculator function of turbocalc. But I do know that I've used 24#'s on a 400hp blown engine before with no problem.

 

This is a common misconception, which I myself used to perpetuate. It is absolutely true that GM and Ford vehicles use different pressures. The flow rate for injectors is determined at a specific BAR (psi) which I don’t believe is the pressure used by either manufacturer. This BAR that is used for specification purposes and testing is the mean pressure for the min and max operating capability of all injectors in this family line. This “testing pressure” is used regardless to the pressure that will be used on the injector when it reaches its final application. In other words the guys making the injectors had no complete knowledge of the actual specific pressure the injectors would finally be used at because they only build injectors not cars. I found this out after arguing this with my injector rep. he invited me to see GM and Ford 19# and 24# (yes there are GM 24# in addition to the 22#) injectors on his flow bench all hooked together. They all flowed 19# or 24# running off the same fuel rail into individual burette style fluid catchers. On another note, sadly to say that the Ford injectors are more closely flowed to each other than the GM ones were at the same exact pressure with exception of the newer Delphi (GM) which were way close. I guess this is why companies like Accel that sell injectors advertise the same injector for a 305 gm and a 302 ford (also 360 dodge).

 

At 90% duty cycle, you are basically fully flowing the injectors. So the math sould be

24 lb/hr * 8 injectors / 0.55 BSFC ~= 350 HP

 

You stated:"The flow rate for injectors is determined at a specific BAR (psi) which I don’t believe is the pressure used by either manufacturer."

What is the fuel presure, BAR (psi), which they use for the rating. Is it 43.5psi which I hear often?

 

43.5 psi is it. My memory of the exact amount may be off, I just know that the pressures used for the flow measurement is always the same , it is a SAE standard. If the SAE standard is 43.5 then that is it.

 

hehe look what I found on line.

 

just one quick question,
is there any problem using ford injectors in a gm?
a friend of mine has been a GM tech for about 30 years, and i trust him more than anyone else i know when it comes to cars, and he swears than running frod injectors in a chevy will EVENTUALLY cause problems... because he says you can just look at the way the tip of the injector is, and the ford is completely different, also the ford intakes have 3-4" of runners before it enters the chamber, while GM's basically spray immediatly before the chamber. so basically the nozzles are different and they atomize differently. i know tons of people have chevy motors with ford injectors and they are pushing some crazy #'s, and seem to be running fine, anyone know if there's any long term effects?

 

It's 3 bar, or 43.5psi, and fwiw, if you put some GM(usually lucas or Rochester) 24's or ford (usually bosch) 24's on a flow bench, you'll get a different spray pattern, but you'll get roughly the same flow.

FWIW, ford seems to be going away from the bosch style injectors and going with lucas style injectors, just like GM has for years.

Stock LT1, among others.

Are these new or old injectors? Typically, after a few hundred miles the ford ones get much more uneven where the GM ones stay good for longer. As far as I can tell the internal metering plates on the fords get clogged easily.

 

If you have proper a/f ratio across the rpm range, there will be no long term effects. The only caution is to use larger diameter o-rings (GM) in the stock TPI rails because they CAN LEAK if you dont. The ford solenoids have the same resistance as their GM counterpart, so there wont be any electrical issues.

The pattern and direction of the injector has a lot to do with emissions. For instance, spraying on a hot intake valve can lower emissions.

 

I don't know that I'd agree about the injector location… the only ford or chevy V8 that I can think of that comes anywhere close to spraying right at the back of the valves is the LS1, the rest are pretty much the same WRT to injector location.

The injectors do act differently, the GM has a more concentrated pattern, where the ford injectors have what most people think is a better, more fan like pattern. In practice, the GM pattern is probably superior, since the ford pattern usually requires more AE (basically, the ecm equivalent of accelerator pump) since the ford injectors tend to coat the walls of the ports and less fuel stays atomized when the throttle opens and the pressure rises… (how much you actually see depends on the actual injector location…)

 

Looking at BSFC is only part of what needs to be considered.

When in Accleration Enrichment mode the fuel for AE is time based, meaning it takes time for the injector to squirt enough fuel for the engine to acclerate. So while you can get by with small injectors, the worse your selection the more likely you'll have tip-in pre-ignition.

Also, if your running closed loop then the more drastic the changes are needed in BL to correct for any abnormalities.

If the BSFC number was the only concern then GM would be using much smaller injectors.

IMO, if you want to double the HP of an engine and use a stock ecm, then double the injector size.

 

accidental post

 

huh… in that case maybe I should just get some 96's for my "stock" L98

BTW, Bruce, you'll be happy to know that I finally ordered a prom burner today and am joining the dark side…