how to size EFI injectors ??

Smaller is generally better. Better atomization for the amount of air used, especially at lower RPM. Too large of an injector can cause idle instability and other transition RPM issues.

Go 19.

My old 305 RWHP (est 360 FWHP) Chev 327 used 30# injectors and never ran out of fuel even at 7K RPM.

Doug

 

I have a set of new bosch 0 280 150 991 24lb injectors that I bought for my 308 before I planned the large supercharger. I bought them with the idea I could first run NA and then add a smaller Eaton SC but changed my mind. You can have them for $125, I will pay shipping.
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personally, id go with the larger injector. you can go bigger than 24lb if you want.
if you are looking toward future mods it is the smartest way to go.

you should also upgrade to an adjustable fuel pressure regulator & more powerful fuel pump(or booster pump) so you can accurately tune to your engines fuel requirements.

my Ferrari has 24lb units. its enough for now but keep in mind that if i tune to make more or less power, i can compensate the fuel requirements by increasing or decreasing pressure at the regulator, but more pressure means less volume and can still create lean conditions! this is where you'd need the extra fuel pumping power.

imagine adjusting the nozzle of your garden hose. completely open and you have no pressure and 100% of your spouts volume. but under pressure there is restriction, less volume passes and your water shoots farther.
-just keep in mind that i am speaking from my own experience with turbo charged vehicles and i dont know if you plan on extruding that kind of power from your car, but with EFI you'd be set up to make those kind of mods.

id rather have the bigger injector and tune it down than have the smaller one and push its limits. but its up to you.

5.0l mustangs came with 19lb injector and only made 225hp @ the crank. 36lb is a popular upgrade for those cars.

my grand national came with 28lb/hr injectors(245hp @ the crank, but only a 6 cylinder). it now has 42lb/hr injectors. there is no idle or driveability problems with the stock ecm and injector specific chip.

if the larger injector affected the street manners of your Ferrari, your EFI can compensate. my 328 idles better than any other 3x8 that ive ever heard(and at a lower rpm with 20lb of vaccuum). its not the injectors that improve idle, its the EFI.

just another reason why i love EFI so much!!

btw, my ferrari has the booster pump and my grand national actually has 2 fuel pumps both mounted in the tank.

 

oh yeah, i almost forgot.......

different sized injectors operate under different impedance.
in my grand national, i went with the 42lb injectors because at the time, they were the biggest i could run without changing the drivers in my stock ecm.
now Bosch makes 50lb injectors for the stock grand national application. i know people running the newer 50lb with no downside -on cars with less turbo than mine.

so make sure the injectors will be compatible with your EFI.

 

I pm'd you but I'll reitterate here ... I'm running 30# Bosch/Ford motorsport "red" tops or something like that.

Mke just used them on a bone stock motor I think ... maybe he can comment on how it idled and ran. No issues that I'm aware of and there's plenty more bandwidth available if you start playing with nitrous, alternative fuels, or just playing period .


cheers

 

The injectors look identical to what Bert posted, which is pretty much the standard Bosch style. I wanted flexibility with the bungs to be able to run just about any injector.

cheers

 

I am running 26 lb injectors on my euro 308 gts with TWM throttle bodies. they work great!
last dyno run was 220 RWHP

 

I don't know if you EFI guys are using O2's, but I came across what looks to be a very-cool gadget. It fine tunes your lambda feedback circuit to give your engine design the desired AFR. It's an O2 controller that goes between the exhaust and ECU. It's the LC-1 from Innovate motorsports. I HAVE NEVER USED ONE. I'm seriously considering one of these setups because this appears to be the best global approach to give you emissions, power, fuel economy, or whatever you program in (just obviously not all at once). You can't adjust it on-the-fly. You need to connect it to your windows driven laptop and make adjustments. If anyone has any feedback on this gizmo, I'd love to hear it.

I hope this isn't too far off topic and my input helps add to you bag of tools.

 

I have the LC1 in my 308 - an excellent tool. you can program the output curve to sync up to the ecu in the car. i am running electromotive tec GT. i also have the digital gauge tied to my lamda sensor - so my ecu sees the A/F ratio along with the digital guage up in the cockpit. the best real time tuning device as far as i am concerned - like being on the dyno 100% of the time while driving.

 

There are several software tools out there to help size injectors- your ecu software might have such a tool. I am running a TEC3 Electromotive and using their configuration "wizard" for 260 Brake HP, it came up with 19lbs. I'm running 19lbs 302 Mustang injectors in my 308QV and the car runs great all the way to redline. It has also allowed me to omit the Idle Air Control Motor. (Setting up the IACM is a PITA). Buy the injectors that are sized for your current engine. If you change the engine specs, buy new injectors - they are only around $200 for a set.

 

The Innovate LC series works well for feedback and is programmable for output voltage vs AFR, so it will work with about any feedback capable ECU.

You are correct to be concerned about HC emissions.

Large injectors will often puddle fuel on the port walls/floor, causing a more fuel than needed to go into the cylinder during off idle acceleration for a brief time.

Some ECUs have a Tau function (possibly called something else, depending of who made it), that allows you to program in fuel reductions to account for this fuel as it gets atomized at some later time after being injected, but that seems like such a PITA to try and deal with.

And a lot simply depends on port volume, if you have high air flow, low port volume, you don't need to be worried as much about oversizing as compared to very large port, low air velocity at low speed that will puddle more.

As in carbs, bigger is not always better. Injectors are easy to change and not that expensive,and reprogramming to a larger injector is simple math batch function.

Doug

 

Thank you, and thank you Doug.

Could you tell me more of this cockpit gage? Is it offered by Innovate? Is is cheaper than the LC-1? Also where did you buy it? Did you use the cockpit gage to set the LC-1, or did you use an external gas analyzer?

 

I use the Innovate LC2, IIRC, it is basically the same without the cockpit readout and data logging, or maybe I have the LC1; anyway, I have the cheap one as I am only using it for ECU closed loop feedback.

I have a separate NGK AFX readout running off a different O2 sensor.

Now, that being said, I had the AFX first, but it doesn't have a programmable ECU output signal,a nd the ECU I used, has a different O2 sensor input requirement than the AFX put out. Had I not already had the AFX, I would have bought the Innovate LC with readout.

IIRC, the AFX puts out 0V at 8 AFR and 5V at 16 AFR (check the AFX website for verification), if your ECU will accept the AFX output, it is a nice readout /ECU signal, real easy recalibration as compared to the LC.

Now, if you buy the LC unit (or any unit), keep all the instructions and calibration **** they send with the unit, as you WILL need to recalibrate your O2 sensor after perhaps 2000-3000 miles, because if you don't, the O2 sensor will think the engine is leaner than it really is after the sensor is broken in,and cause you to run too rich. Recalibration is simple, hardest part is pulling the sensor and letting it dangle in free air for calibration.

Being the cheap bastard that I am, and wanting true sequential EFI, i used the Accel Thruster ECU module ( I paid about $1000),and dual sync distrib (another $300 or so) on my Chev. I would probably not use that particular brand on my Fcar if I ever go EFI on it, nothing wrong with the Accel unit, but others (Motec, FAST, others) would probably be a better choice because they have better options for a crank position signal, and would have some more nuanced programming parameters better suited for the 308 motor.

Good luck,

Doug

 

Actually, you CAN have it all at once.

You program your VE tables and spark curves for max power at WOT and max efficency at cruise.

You set up WOT at perhpas 12:1 AFR,a nd 40%-50% MAP cruise at around 15:1 or maybe even higher and adjust spark advance to take maximum advantage of part throttle MAP.

It will cost you 3-4 hours dyno time for a sharp tuner to maximize your program for max power and best economy.

I had my 427 CI small block Chev dyno tuned,and it can cruise at 55 MPH at 23 MPG (on a .43 Cd car) and still do the 1/4 mile at 11.5 seconds at almost 120 MPH, and it is as docile around town as a new Toyota Camry. Without the EFI programability, it would be a ratty car to drive on the street and have crappy fuel economy, and it runs clean, no part throttle unburned gas stink like you would normally get with an engine cammed like it is.

Doug

 

You have an awsome system! You can control spark timing and mixture as a function of throttle position, and rev's etc. Very cool. I just want the lambda correction to remain spot on in the idle to 3,000 rev range (for now). Now I'm curious about this 3,000 mile re-calibration requirement. Does it go really rich when it loses calibration? Is it subtle, or are you driving along and suddenly get plumes of smoke? I'm trying for just some simple and VERY VERY reliable and consistent lambda controls.

Thanks!
Bruce

 

It goes rich, but not like someone turned a switch. You first notice that yes, WOT starts to put out a little black smoke if you let your first calibration go too long, especially since WOT is programmed rich for power to begin with. Go from 15:1 AFR to 14:1 AFR at cruise and you don't notice anything, go from 11.8:1 AFR to 10.5:1 AFR and it puts out black smoke

Recal is easy, you unscrew the O2 sensor from the bung, let it hang in free air,and follow the calibration instructions, takes about 5 minutes to recal, longest part is getting the sensor in and out of the exhaust header, so put it someplace that it is accessible.

Recal should be done every 5-7K miles after that on wideband sensors. It takes maybe 30 minutes from jacking up the car to taking it back down.

I finally reprogrammed mine so that closed loop feed back is only engaged at less than 75% MAP (Manifold Absolute Pressure), and it goes to open loop, program only at WOT for 1/4 mile use so I don't lose power due to O2 sensor inconsitencies. This of course only works if you don't change altitude.

Now one nice thing about closed loop feedback EFI is it will altitude compensate.

I live at about 1000 feet above sea level. I sometimes go to car shows that are at 7500 feet above sea level.

I simply reset the entire RPM/MAP (Manifold Absolute Pressure) range to go on closed loop 100%,and the EFI corrects the fuel to keep the same programmed AF ratio matrix. While every bodies carbed cars are running black smoke rich at that altitude, my car runs just fine. Reprogramming takes about 5-10 minutes when I do this.

Doug

 

It appears that too much emphasis is being given to the role of the O2. When you program your ECU, the O2 circuit is not engaged. You work the VE table to produce the desired effects throughout the MAP / RPM range. Only then do you close the O2 circuit in order to perform fine adjustments during transitions. Remember, the O2 is “downstream” and is reading the results of the burn - it is always playing “catch up” to what actually is happening in the engine. That is why you disengage the O2 circuit during WOT and upper RPM running – its input to the ECU is too late. (I’ve been told this is even more relevant when running a wide band sensor though I have no on hands knowledge on this point). The key to EFI is the initial parameters entered into the system then tuning the VE and ignition tables. Then work in the O2 and temp sensors. FWIW.

 

The wideband O2 feedback is what compensates for altitude change. If you live in Florida, it doesn't matter, if you live in CA, CO, AZ, etc where you can go from sea level to 8000 feet MSL in a 100 miles, it does.

At WOT, the feedback only deals with altitude change, at lower RPM, it greatly helps smooth out your idle,and transition to midrange if you have a cam of significant duration, as fuel puddling is variable and can't really be programmed into the parameters. That is whay I can cruise around at 1200-1500 RPM with a cam that wouldn't be happy under 2200 RPM if it had a carb. Open loop only is fine for 3000 RPM plus, closed loop is what makes the car very tame under 2200 RPM.

That being said, it is worth $400 or so to take your car to a tuner shop, and have it dyno tuned open loop to get it real close, then turn it over to closed loop either for part or all of the VE table. I like the closed loop AFR table as I can simply set whatever AFR numbers I want at certain RPM and throttle MAP, and that will be the dominant table when in closed loop.

AFR is easy to understand as their is no math conversions. ~12:1 is performance, ~15:1 is economy. If you find you have your AFR too high at say 1800 RPM or 1200 RPM, or whatever and you get bucking at a certain MAP, you can richen it up a bit in that range, or back off the timing a bit in that area.

Doug