Has anybody seen or tried this?

[Erics51chevy]

https://sites.google.com/site/sloppy...fuel-injectors

Decapping an ls injector. Changes the flow rate from 24 pounds to upwards of 78 pounds by taking the flow restrictor off.

Might give this a go on my project. Only because i have 8 stock injectors to spare

[joedoh]

you will spend a lot of time tuning, and I say this because there are two states of tune, open loop and closed loop. in open loop (engine warm) the tune uses AFR feedback from the O2 sensors, in closed loop (engine cold, other conditions) the feedback circuit is ignored, and runs on preprogrammed tune only. so if you have a preprogrammed tune that thinks the stock 24lb injectors are installed, the tune will send PWM signals to the injector that corresponds to the warmup fuel required. if the flow is 3x, you will soak your spark plugs and belch black smoke until the O2 sensors come online.

this is why most guys will just run a rising rate fuel pressure regulator on turbos, when you are on boost it raises the fuel pressure, increasing flow, and the O2 dials in the AFR. when you are cold, and you almost never go full boost right after starting, the factory fuel pressure and cold start tune work just fine.

looks like a neat trick, though. keep in mind that very few EFI systems are sequential injection (valve open, injector fires), and those that are sequential switch to batch injection (correct amount injected with valve open or closed) after a certain rpm because a) its hard to get all that fuel in one squirt and b) as the rpm goes up the valve open duration window is infinitesimally small to squirt fuel through. I bring this up because the pintle is there not only for regulation but also atomizing the fuel to mix better with the air. At high rpm fuel in a batch fired injector can drip or pool in the intake and cause running problems, fire hazards, even quench the cylinder.

[HUSSEY]

Personally, I don’t think it would be worth the time even to play around with it. As joedoh noted, you’ll need to retune to account for the significantly larger flow rate. I don’t know the stats off the top of my head but I believe those motors made in the 200hp range on 25 lb/hr injectors. Doing a quick linear scale; 78 lb/hr injectors would be suited for a motor making 800+ hp. Also, the author noted that you may experience injector flow variations, which I think is an understatement.

I watched an episode of Hot Rod Garage where they did a cheap turbo on a 5.3 and they used the 42 lb/hr “Green Giant” Bosch injectors. You can find Chinese knockoffs of these for $10 a piece on eBay. I don’t know what pressure that flow is rated at but you can approximate the flow at your regulated pressure by taking 42 times the square root of the ratio of your pressure to the rated pressure.

[Coupeguy2001]

Everybody is going to chime in on my comment, and that's fine. Just understand that my comments come from experience, not just someone else's entries.


not to be difficult, but open loop is cold, and closed loop is warmed up. Since 2000, almost all engines use sequential fuel injection due to emissions standards and more precise fuel metering.
A 1989 chevy corvette 350 uses 24 lb injectors, an 85, with less sophistication uses 26. Corvettes of that era use TPI. The mass air flow sensors of that era were 500CFM, as that only one cylinder can use the intake air at a time, and 500 cfm is good for a 383. Throttle bodies were 600 CFM. Those engines were batch fire.
Those engines used the distributor for timing and crank position.

Today's engines use a cam sensor, a crank sensor, map and maf sensors, and independent cylinder coils for ignition, with higher energy spark per plug. The coolant temp sensor is used for cold and hot engine fuel metering, and compares it's value through the computer with an outside air temp sensor. The oxygen sensors are the feedback to the computer to tell it how well it did on the last burn cycle. Then there is the engine inlet temp sensor. all three make the fine adjustments for fuel mixture for ambient temp.

Jumping up to 78 Lbs per hour is too rich for a 5.3 or a 5.7 or a 6.1. especially with 55-60 PSI fuel pressure instead of the old 45 PSI. The fuel pressure regulator has a vacuum hose on it to lower the fuel pressure, but to increase the fuel pressure 5-7 PSI during acceleration to spray the fuel pattern from the injector a little differently, and to atomize the squirt so that in decreased combustion cycles, the fuel lights off quicker to eliminate a slight hesitation. This is accomplished when the vacuum goes away on acceleration.
If you jumped up 5 LB, it would be controllable. at 78 lb per hour, three times the needed fuel for a 350, You are going to drive your O2 sensors nuts and trip the check engine light which will put the limp home mode in play. That is a preprogrammed fuel schedule and timing rate based on the sensors that are correct.

78? don't think that it is a good idea.
Remember, there is a team of engineers that figure out all the engine run parameters, another team designing injectors, another team designing electronics, another team designing sensors, another team testing, and then there is the sensor and electronics refinement, then the programmers map fuel schedules, timing schedule maps, and then more testing.
Then the whole team get together with vehicle weight, gear ratios in the trans, final drive ratio, tire size, and the power curves are scheduled in.
If you don;t have a team designing, testing and refining, I would leave the backyard tech to carburetors.

[Erics51chevy]

I agree with you all and am not ignoring any of this information but after doing this with a turbo i would obviously get a custom tune by a guy i trust on a dyno. But fluctuation would be a concern.

[joedoh]

Originally Posted by Coupeguy2001

Everybody is going to chime in on my comment, and that's fine. Just understand that my comments come from experience, not just someone else's entries.


not to be difficult, but open loop is cold, and closed loop is warmed up. Since 2000, almost all engines use sequential fuel injection due to emissions standards and more precise fuel metering.

oops that was me that got open v closed backwards. rookie mistake. I even proof read it before I posted. you are right.

sequential systems switch to batch over about 2500 rpm even on the most powerful processing, most detailed input systems. there just isnt enough window at that rpm to inject all that fuel in that short amount of time, even the delay of the solenoid opening has to be accounted for. The performance difference at that rpm is nonexistent with a properly designed system. Some manufacturers use sequential only for idle and warmup, when emissions are measured for credit, and switch to batch almost instantly when driving. Why try to get it all in 200 degrees (of cam) when you can get it in the 720 (of crank).

I built a fuel injection system from scratch for my engineering senior project, the high requirements for sequential injection (injector size, processor power, extra sensors) dont really help beyond a certain rpm, even though common thinking would want to believe that injecting fuel only when the valve is open is the correct way.

There is a sequential system that can work at high rpm, that can inject a large amount of fuel in a very short window, it is direct injection, and runs over 2000 psi on injectors that are as long as a ruler and inject directly to the combustion chamber. The diesel guys have been using them for years and you can have a very lean AFR without knock.

your other points are exactly correct, lots of tuning!

[Softpatch]

sorry for my question..
I'm still stuck in the "70's"
.(carb guy)
.
I was schooled that most US domestic cars Chevy/ford/Chrysler were Batch fired + means one fire all fire
Europe (german/Sweidish/GB/Italian) were sequentual fire Means specific injector fires during combustion stroke
.'
.

[joedoh]

Originally Posted by Softpatch

sorry for my question..
I'm still stuck in the "70's"
.(carb guy)
.
I was schooled that most US domestic cars Chevy/ford/Chrysler were Batch fired + means one fire all fire
Europe (german/Sweidish/GB/Italian) were sequentual fire Means specific injector fires during combustion stroke
.'
.

no, batch v sequential was always a processing power problem. the best Bosch EFI systems from the 80s and 90s (flapper AFM before MAF) were batch and its been theorized that GM borrowed heavily from this system in their original efforts.

Batch systems usually work in banks, so on a V8 2 batches of 4, a V6 2 batches of 6. Like I said, common sense would dictate that it shouldnt work efficiently that way, but it does, because the time between valve opening events at higher rpm is about 100 milliseconds and sometimes much much less. Air bounces in the intake as it waits for the valve to open, its never really stationary, so the fuel stays atomized and waits for the valve to open.

Imagine it as a prison break where the escapees are jumping through a turning fan with 4 blades. does it make sense for them all to rush for only one opening of the fan blades and simultaneously jump together? or to utilize all spaces between the blades? lets say that 4 can jump through simultaneously, even if the same number gets through the fan on every revolution using one per opening, which takes more planning and careful timing? Either way, 4 get through every revolution.
Now say you need more than 4 to get through every revolution, would you rather get four through every opening or try to get 16 through the one? this is the same problem with injector sizing for "one shot" sequential systems, you quickly overcome the ability of the injector to get enough fuel in the same window.
Now double the speed of the fan. Now quadruple it.

[akdg87]

i wouldn't advise it, you also need to have them bench tested to see the flow rates. if you follow the Sloppy Mechanics FB page you will see the flow rates can vary wildly (IIRC there was a variation of up to 20 LBS/HR between injectors).

[1project2many]

Without substantially more research I would avoid disassembling the injector or taking the pintle caps off. I looked for, and did not see, a report from Witch Hunter describing the spray pattern of the injectors after the modification. There is a *bunch* of engineering and precision manufacturing involved in creating the right pattern for a particular engine. What typically happens with a home-grown modification is that the engine runs after the changes but performance can be inconsistent. Non-emissions vehicles like ours don't have any legal troubles if the exhaust smells rich or if the engine runs a little funny at idle but imo what is the point of working to put in EFI if you're only going to downgrade the system so it cannot be it's best? As you're looking for an economical way to fuel your turbo engine I'd say you should do your homework. Find some of the more popular EFI sites and look at what guys are saying about this modification. You might even try sending a note to Witch Hunter with a link to the video asking if they have any comment on how they believe these injectors will perform.

[quote]the best Bosch EFI systems from the 80s and 90s (flapper AFM before MAF) were batch and its been theorized that GM borrowed heavily from this system in their original efforts.
[/qote] I've been into the code used in GM computers and I've been working with GM EFI since it's early days in production cars. I would argue some about GM "borrowing" heavily from Bosch. There are only so many ways to put fuel into an engine and there are only so many ways to accurately measure air and fuel. Much of the strategy used by GM was patented before Bosch built their analogue D-Jetronic systems (the flapper-sensor K-Jetronic is a continuous flow system unlike today's EFI). Bendix should really be credited with much of the groundwork for many of today's systems beginning with the Electrojector. And it has been determined that Motorola was heavily responsible for many of the control circuits and accompanying code used in many of the early GM / Delco systems.

[joedoh]

Originally Posted by 1project2many

I've been into the code used in GM computers and I've been working with GM EFI since it's early days in production cars. I would argue some about GM "borrowing" heavily from Bosch. There are only so many ways to put fuel into an engine and there are only so many ways to accurately measure air and fuel. Much of the strategy used by GM was patented before Bosch built their analogue D-Jetronic systems (the flapper-sensor K-Jetronic is a continuous flow system unlike today's EFI). Bendix should really be credited with much of the groundwork for many of today's systems beginning with the Electrojector. And it has been determined that Motorola was heavily responsible for many of the control circuits and accompanying code used in many of the early GM / Delco systems.

The Kjet was CIS but the Ljet was indeed batch with multiple injectors and a flapper AFM. Bosch Motoronic switched to a MAF. The earliest GM EFI was TBI, and it was terrible, putting two of them on a corvette didnt make it any better. The similarities between Bosch and GM were in the mid 80s, the batch mpfi systems on the V6 cars. some ran alpha n (throttle angle/rpm, the fiero had this) and others that werent as performance oriented used hot wire MAF.

edit: I have owned and worked on so many of the cars we are talking about, I love EFI and like I said, I built one! I have had k-jet volkswagens and bmws, l-jet bmws (done the flapper spring mod on the AFM!), motronic mercedes, an alpha n fiero, several 3800 series, TBIs, MPFIs, sequentials, and most recently a direct injected 2.3 mazda. I even had a mechanically fuel injected BMW 2002tii, the kugelfischer system operated at almost 300psi, no dirty injectors there.