crainholio

iTrader: (2)

Your point on the error that some "tuners" commit is a good one...they just bump the Injector Flow Rate table and then wonder why the things aren't behaving properly.

However, at some point in your education (and we're all learning) you'll discover that injector flow characteristics have nothing to do with an engine's volumetric efficiency as configured in a powertrain control system.

Until then, stay away from my lawnmower.

VE tweaking when only the injectors have been changed is a band-aid, and a poor one at that. Fooling the PCM into flowing more or less fuel at a given VE coordinate may get things working reasonably well but it's a bad approach.

The real mojo that amateur tuners miss is in the Injector Offset table as well as an accurate (not algebraic based on the old injector flow rates and percentage increase for the new injectors) Injector Flow Rate table. Short Pulse Adder is also a game-changer when running injectors that have a 2-slope flow rate...one for pulse widths > their defined flow rate breakpoint and a different slope for pulse widths < their breakpoint.

You seem to know enough about engine controls that a read of Greg Banish's (AKA turbolx) other published works on engine control systems would be a big help...you're probably just a short jump away from fully understanding how the PCM manages fuel delivery.

Everything I just regurgitated above is from Banish's other article linked below, along with my own experience tuning a few injector swaps after having read his two books and his DVD: (yes, I'm a fan...they cost $$ but not as much as paying a professional tuner to do it right)

http://www.calibratedsuccess.com/***...%20Article.pdf

eb02z06

iTrader: (18)

Dude, do you even know who Don Kinder(Slowhawk)is? He's probably one of the first guys to dial in low impedance injectors the hard way-and of course he attacked flow rate, offset and adders and got 95lb & 120lb injectors to idle like a kitten. Way before the days Greg started to publish his DVDs-all of which I have bought and watched.

Have you ever plugged in injector data on BS3 or Haltech or FAST?

crainholio

iTrader: (2)

I don't know who he is, but advocating use of VE table variables to compensate for fuel injector swaps seems like very weak sauce. I can see where it's possible using WB-02 to watch the exhaust stream and nailing the PCM into open loop during tuning, but still a band-aid fix versus correct injector characterization.

Maybe I misunderstood what he was saying? Because anybody that thinks injectors affect an engine's volumetric efficiency clearly does not understand the calculus...it's all based on airflow and cylinder filling.

Greg B's documented experience developing injector calibration data for OEMs speaks well to his capability and understanding of powertrain controls. I have no reason to doubt the accuracy of his information.

To answer your question, no experience on any of those 3 systems. I learned what I know about fuel delivery and engine setup during high school and college working on an offshore powerboat racing program and a Late Model asphalt racing team, as well as OMC outboard motor school. Carburetors. If you understand carb principles, fuel injector behavior makes perfect sense, no?

Slowhawk

iTrader: (12)

Come on eb02z06. LOL

I like getting schooled by new tuners..LOL

Some of these new tuners need to start like we did. LS1 edit and a shitty scanner. No schools, no books, no video's out to teach you anything.

I fully understand injectors,tuning. Scaling,pulsewidths,timing ect ,ect. You do not have to get technical with me.

crainholio

iTrader: (2)

Define "new."

LS1Edit, AutoTap, and MS Excel here, since 2003. Before that was crappy DOS-based software and Tuned Port Injection chip burning since 1997. Before that was metering jets, power valves, and accelerator pump cams since 1988. And not a single blown or damaged engine.

Set up a pair of V8 engines to run from Miami to Bimini and back at WOT, lifting throttle only for wave jumps. It's a little more involved than a few seconds at a time on a dragstrip.

NicD

iTrader: (7)

It amazes me that people need things handed to them on a silver platter and can't figure this stuff out. Offsets and low pulse width settings are things that tuners have had to back calculate as unknown variables way before injector companies starting giving it out and it's really not that difficult on known fully tuned configurations with the only thing being an injector change. Now I know I'm not selling DVDs or injectors priced at twice the price but this is pretty simple **** for any professional tuner worth their salt who has put in the research and done their homework.

Before everybody jumps my **** I guess I should add that yes I understand it's nice for new people who are learning to tune to have some instruction and it's nice to have data for injectors as it saves time but let's not pretend you can't tune a car and not get damn close on those settings by doing your own research and testing... and when I say close I mean within a couple percent fuel trims of where they should be.

turbolx

This alone is a very good point that perhaps I have not made well enough myself.

We often have TWO complex models (each with varying degrees of freedom) that require adjustment. Even worse, the measurements for each is partially dependent upon the other. All we really want is the correct AFR delivery (all of the time!), but this changes with either airflow estimate or fuel flow characterization.

Ideally, we would only change one of these at a time. It's always easier to take a car with stock injectors and tune for a new camshaft or light-pressure supercharger as long as the OE injectors can keep up. This lets us concentrate on the VE and MAF tables without much concern for fuel delivery. Alternatively, we can change injectors on a stock airpath engine (or one that has previously been correctly mapped for VE and MAF) and assume that the errors must be in the fuel delivery side.

The rub comes when a customer has us tune something where both airflow and injectors have been physically changed. It's possible to come up with multiple sets of solutions that combine some change to injector data and some other change to airflow modeling that happen to work out today. Only one of these sets of solutions however will continue to work as the conditions change for temp, baro, fuel quality, etc. This is why starting with some good reference point goes so far toward minimizing the guesswork for the calibrator. If we know that the injector data is right, we can concentrate on airflow modeling.

Conversely, if you're lucky enough to have a flow bench sufficient to measure the entire range of the MAF (and the entire inlet plumbing path!) then you could generate "THE" MAF curve and never touch it again like GM does.

Fundamentally, these aren't that different. They're just simpler in that they make no corrections for short pulse phenomena. Any short pulse errors get "baked in" to the base VE table. Luckily that resulting skewing of the VE and airflow estimate don't mess up closed loop idle airflow corrections or knock routines, or torque models like they can in newer OEM ECUs.

Ack! Those were the days. I don't miss that. I still remember some of my earliest discussions with OEM calibrators and how violently the light bulb lit up over my head when I realized how these systems were really working versus how the mIRC channel "experts" were claiming they worked. I guess we all have to learn the hard way a bit at the beginning.

LSxPwrDZ

iTrader: (4)

Another note on the aftermarket controllers is they have much better injector circuits than an OEM GM ECM/PCM. IMO that alone changes the short pulse and voltage offsets because they normally supply much more current to the coil to get the injector open.

That is another variable that test equipment can't even take into consideration unless you physically use the PCM or ECM as the injector controller as the test means.

turbolx

I think you may be confusing the difference between saturated vs peak and hold driver circuits rather than OE vs aftermarket. There have been plenty of OE systems that use peak and hold drivers (almost every direct injection system does this now).

The current supplied to the coil in a saturated driver is largely just a function of V=IR, meaning that for a constant supply voltage and fixed impedance injector coil (which only changes a small amount with temperature) the current is also constant during the length of the "on time". You can see this if you put a scope on the wires. There is a little bit of change in flyback voltage between drivers since they may have varying zener clip diodes in the circuit to limit field collapse in the coil, but mostly affects a very short closing time anyway. Opening time is almost exclusively a function of supply voltage and injector design. Short pulse behavior is part opening time and part dynamic flow through the orifice plate (which is a HUGE part of injector tip design).

ZL1Killa

iTrader: (17)

Nice info.

LSxPwrDZ

iTrader: (4)

Interesting! So the grounding circuit within the PCM that has to carry that current wouldn't cause any variation in how the injector opens and how quickly it opens?

It is just very odd that high impedence saturated injectors seem to have much better control over lower pulsewidths than a factory PCM does. I had alway's assumed it was from the beefier drivers within aftermarket ECU's.