Fazz73jr

iTrader: (3)

Im looking to replace my svo 30# injectors (type 2 bosch) with some 42# injectors. 30# where already at ~93-96% duty cycle with the current setup. Im just not sure which type to get. I think I read some where the type 3 atomize fuel better.

I have narrowed it down to either FIC blue demon type 2 42#or FIC blue demon type 3 which are avialible from 33-48#. Which would you get and why? If the type 3s would you keep em at 42#the or just get the 48#? Type 3s from FIC also have an $80 core charge type 2 no core charge. Both are same price otherwise.

Engine is the 383 lt1 in my sig but swaping out the xfi280 cam for an LE 242/248 custom grind and swaping stock fuel pump for a hotwired walbro 255. Everything else is the same as sig.

96capricemgr

iTrader: (1)

I would wait and see if you need more injector.

You duty cycle is NOT a concern, I know ignorant folks like to freak out over anything over 80-85% but that is because they are ignorant not because it is an actual problem with modern injectors.

You know how silly it is you want to worry about spray pattern but then want to put in a 40% larger injectors that is MUCH more than you need?

speed_demon24

iTrader: (6)

I hope you plan on doing gears with that cam.

F0x Slaughter

I still don't believe people that its okay to be over 90% is okay. They say over 85% the pintle or discs are "floating" because its trying to open and close so fast. To each his own.

Also flow rates are done at 100% static. The injector is kept fully open, its not trying to close and open.

96capricemgr

iTrader: (1)

Talk to some real racers and see what they say about injector sizing, they tend to run as small as possible and have a few reasons for doing so like a fine mist for a long time atomizes better than a big squirt for a short time.

I would be more concerned with if the engine is lean than the duty cycle.

FormulaJoe

iTrader: (5)

While I have read a bunch of stuff agreeing with what you (caprice) are saying, just stating this is better because "it's what real racers do so go talk to some" is probably not going to help the OP out much. The OP is looking for quick answers with some type of evidence.. Not trying to come across as a dick, just saying....

To the OP here's a start...
https://ls1tech.com/forums/lt1-lt4-m...injectors.html
Read thoroughly everything GIZMO and Bowtienut are saying in this thread. They are both smart people who know their racing stuff.

Another good place to check out..
http://www.corvetteinjectors.com/videos.html
There's videos on why the 3s are a bit superior then the 2s. Most of the videos on that page you should check out.

I went with the 30lb Bosch 3s for my build because of the videos on the site and everyone says they work great that I have talked to.

F0x Slaughter

Ask companies that make injectors.

Alex94TAGT

Our site sponsor, Racetronix, recommends staying below 80% duty cycle for stable injector operation. (link 1, link 2) Are you claiming that they are ignorant?

1. Please provide third-party evidence to support your claim that a 30# Type-2 injector at a higher duty-cycle atomizes finer than a 42# Type-3 injector at a lower duty-cycle.

2. Who are some of these anonymous "real racers" intentionally running near 100% DC instead of stepping up to a larger injector? Can you provide their names and/or email addresses, so that we might verify the claims you're attributing to them?

I'm sure that such a non-ignorant, smart-guy such as yourself has well-documented evidence to support all of his unverifiable anecdotal claims. I'm quite ignorant, you see -- being a lowly electrical engineer, I know next to nothing about heat generated in solenoids and control limitations of pulse-width modulation at various frequencies, so I'm just trying to learn from the experts like you.

F0x Slaughter

Oh come on Alex we all know things are engineered to run at 100%. Look at power plants, they run 100% output all the time right? Look at generators, they run 100% and its fine.

When things get to their 100% cycle first as Alex said heat becomes an issue. Things can run to 100% but for protection nothing runs at 100% because its dumb to. Thats the items design limit. Why would you want to come near to the design limit of something?

Thanks Alex for finding some good reading material. Not based on people who go "well I put these smaller injectors in my car and it made it faster, wheres my spittoon"

Fazz73jr

iTrader: (3)

Ok I got some reading up to do, thanks guys. And sorry didnt mean to open up a can of worms lol.

And yes Speed demon I plan on swapping out the POS 10 bolt. I dont want to waste my time or money changing gears in the 10 bolt. So it will stay as is with street tires untill i can afford a 12 bolt, S60, or 9inch whichever I can find the best deal on.

Thanks guys

F0x Slaughter

12 bolt works great for autos. Seen people grenade them with a M6.

I would go either 9" or S60.
9" raises the car roughly an 1".
S60 pretty much no way you can break it.
I don't like Ford, they did design a great rearend but I prefer Dana.

Before someone says going "Moser and blah blah makes 9" rears" its a Ford Designed Product and Dana designed the Dana 60 (Strange calls it the S60).

Fazz73jr

iTrader: (3)

Cool thanks. I feel the same about ford. Lol people say I should swap my 8.5 10 bolt for a 9" in the nova, but the 8.5 is built and holding up just fine.

Also anyone use FIC injectors on an lt1? I see alot of people tuning here on LSx.

F0x Slaughter

The 8.5" 10 bolt and 7.5" 10 bolt are completely different animals.

speed_demon24

iTrader: (6)

The car is going to be a dog with that cam and stock gears, it wouldn't surprise me one bit if it ended up running slower than your old cam. I would put the $$ towards a rear end first before I even thought of a cam swap.

Longbob

I would be interested to know what fuel pressure you are running. Everyone has their own opinion, but I feel duty cycle is important and I like my duty cycles to stay somewhere between 70% and 75%.

That has been the sweet spot for both my stocker and super stocker. There must be something to it because I tuned an LS1 that won class at the Sports Nationals in Belle Rose this year applying the same parameters. The tune definitely picked the car up.

My car does not like the fuel pressure to be below 50 lbs. It is rare that I will go below 52 lbs. I am generally between 52 and 55 depending on the density altitude. I prefer the higher pressure so it snaps the injector closed between cycles.

Edited to add: I run the 30lb Ford Racing injectors. I have found these to be very consistent in flow when I have tested them after several passes and new out of the box. I would much rather run more fuel pressure than move to a larger injector if that would bring the duty cycle in line.

96capricemgr

iTrader: (1)

Fox, Alex look at the link FormulaJoe posted. You know, the one you ignored that he posted before you.

Then maybe try and find a link to support your opinion that is newer than 7 or 9 years old like the links you posted.

As is discussed in the thread FormulaJoe linked theory and the real world don't always go together. In the end each person has to decide what matters, document-able performance or theory. I am no engineer but I can see what works in the real world and identify who can help me make the most of what I have.

Far as duty cycles and such when we make a 1/4 mile run aren't we taking the engine to 100% DC or do you keep the pedal up a little off the floor?
Then far as the injector DC if a car is maxing out a 30lbs injectors it should be in the 10s, of that 10-11 seconds how much of that time is the injector at 100%?
How about the nice cooling fuel flowing through it.
Then let's consider 100%DC is not meant to say that it is all the injector can handle it is meant that the injector was held open usually for one full minute to test how much fuel flows through it.
I wonder just how many 10 second 1/4 mile passes an injector could make before it spends a minute total time at 100% DC?
If holding it open for 1 minute static on the flowbench doesn't kill it does it seem logical that little 1-2 second blips to 100% while racing are going to do harm? If it were so terrible for them they couldn't test them that way.

I know all that is disorganized but I kept thinking while I typed.

Racetronix

iTrader: (2)

Not running an injector above 80% DC is to ensure that it has adequate time to close and shut off fuel delivery between pulses. This is so it can meter the fuel properly. If injector DC is too high then it will operate erratically. 80% DC is a safe number. In some cases max DC may be higher or even lower depending on the operating environment. Design, voltage, temp, pressure, PCM driver-circuit, fuel viscosity, age etc all play a factor here so it is better to be safe than sorry.

Would you constantly over-rev a motor causing valve-float? Think about it...

F0x Slaughter

Words from the company.

Yeah but valve-float is fine in 1/4 mile. I mean you're only gonna float the valve for a less than 20 seconds right?

Haha.

Alex94TAGT

Sure thing, boss:

https://ls1tech.com/forums/16306655-post17.html

It's from today. Is that recent enough?

96capricemgr

iTrader: (1)

Depends what you mean by "float" there are cams designed to "loft" the lifter at medium to high rpm to gain extra lift fairly common and a proper valvetrain setup will be in control well after peak power so the power dropoff would have you shift anyway.

Far as word from Racetronix they certainly sell and make good products but their argument leans more towards theory than practice. There has already been a link about some very quick cars specifically using small injectors because they find improved time in it. How about someone disprove that?

Again if the AFR is fine how can you argue that the DC is a problem. From what Racetronix is saying those guys should be seeing erratic AFR readings and if they were they would be looking for the cause.

Maybe there is a middle ground here? Like say running in the 80-90% range at peak the AFR does get a little wonky BUT once you get up to 100% DC, they are more or less static and just spraying what the engine needs without trying to open and close????? Static would be the most consistent way to use an injector.

See what I am doing here? Instead of dwelling on theory I want to come up with an explanation for what happens in the REAL WORLD.


I know there are videos out on the web showing spray patterns and such, anyone seen one where modern injectors were run 80-90% and flow tested showing the metering to be less accurate?