I was all set in terms of what i planned to use for my EFI swap for my twin turbo project but now it seems things may upset the plans.

I've been told that the 749's injector drivers are just not really capable of handling an injector of about 50lbs that i'll need to support the twin turbo project. I can get away with 42s but i want the larger ones just in case i decide to step up the boost.

What are you guys running? Are there idle problems?

THanks,
Jay

 

Stock the 749 can handle 8 high imp injectors at racetronix they have 57lbs high imp injectors. If you want to run low imp inj you must change injector drivers.

http://www.syty.net/phpBB2/viewtopic...429p3&start=15

/N.

 

i've just been told that even if you keep the high imp injectors, it can't handle larger than about 32s.

Anyone have any info on this?

I'm reading around the sy/ty boards and they seem to throw 50 lbs in like its nothing. i'm not sure if they are modding the computer or not though.

 

strange.... never heard of it before...Hopefully Grumpy adds info about the subject..

 

I've ran 55 PPH Peak and Hold injectors in a modified 1227749.

And I've run 60 PPH staturated injectors in a stock 1227749.

The oddity with most the info about the Sy code is that the injector constant doesn't work. You have to use the BPC vs EGR to adjust the injector size. If you don't know that, then yes, things just don't make sense.

 

Grumpy, where did you find 60pph saturated injectors?

I'm assuming that these were all 6 cylinders?

 

PT+E, Racetronix, and FullSpeed.com, all carry them.
Yep, one 60 PPH injector per cylinder.
The first two places want to sell flow matched sets, I don't know about Mike at Fullspeed. But, the 60s are out of some really high rent boat applications, and according to the manufacurer specs are really close. The guys selling flow work all seem to think they all need flowed. I'll leave the decision to you about if it's necessary or not.

 

I take it that you're referring to the 57lb/hr siemens injectors, or is it some even stranger oddball injectors?

Flowing... well, I'll do it myself.

WRT to running big injectors with this setup, you and I have gotten into this before. What you're doing with 6 cylinders doesn't translate to what some of us want to do with 8.

Here is the problem as I see it. Stock these things are working 6x 12-15ohm injectors. That means that the 2 drivers are basically pushing 6 watts total stock. Now give it something like 8 SVO 36's (about 11.5ohm) and you're making it switch as much as 21 watts. This makes the stock driver's unhappy and the injectors slow and not wanting to idle, but if you remove 2 injectors it's fine again. You add the 27 or 30 watt Mosfets that a lot of the sy/ty guys are running. This lets you run 6 low impedance injectors well, 8 of some low impedance injectors, but you still end up with some weirdness with 8 big high impedance injectors (the reason has something to do with the current limiting protection "stuff" built into the connector part of the ecm board, what are all those little surface mounts anyway, they look to be resistors, but I'm almost wondering if they're little diodes or something?). Anyway, assuming some 2ohm injectors your 6cyl setup is now pulling 45watts through all the stock wiring (well, in your case I'm guessing it's mostly custom, but for most people running this setup), add 2 more cylinders and you're pulling 60watts and again, making drivers unhappy and injectors slow to act.

I guess that someone has found some 44 watt mosfets, but the next question is at what point do those 4 little connector pins, the board traces and 18ga or so wiring, all designed for 6watts become liability?

Having said all that, I wish I did have all the programming stuff I need to play with this, since I do have some ideas on how to make it work right with some really big saturated injectors (50lb/hr and larger, I'd probably test it with some home made 77's), but of course, since I don't have the chip burning goodies I haven't done it.

 

Nothing oddball about them, and they are 60's.

Really?. OK, guess we'll leave it at that then.

:lala: :lala:

 

I don't come up with the same answers as you do. I'll just run the numbers for the first calc.

13.8 volts (nominal vehicle voltage)
12 ohms per injector (worst case)
6 injectors

I = E / R
W = E * I

13.8 volts / 12 ohms = 1.15 amps
1.15 amps * 6 injectors = 6.9 amps

6.9 amps * 13.8 volts = 95.22 watts.

Or 47.61 watts per driver.

RBob.

 

http://www.cruzers.com/~ludis/1227749schematic.html

Seems to me that the stock FETs should be able to handle this job if they're effectively heat sinked.

Just outta curiosity, how are you planning to get 400pph worth of injectors to idle when off boost?

 

BINGO

that's exactly the problem. Stock drivers just can't open and close the injectors fast enough to allow it to idle properly

 

DING DING DING DING!!! We have a winner… somebody get GoSlash27 a cookie.

FWIW, I was playing with a 165 and an O-scope last night and saw exactly the problem… now if only I could figure out how they got a mosfet controlled circuit to go that slow…

I also had sorta a wacky idea (and my EE friend seemed to like it so we may try it)… do use a smallish car audio amp as an external injector driver box. Think about it, you've got a regulated power supply circuit, driver circuit designed to drive an inductive load, usually a good size heat sink… (sorry… some of my out of the box thinking… I'll put it away now )

Back to my original rut… if I had some chip burning crap I would try this on an actual car…

 

so where's my cookie?? I like pepperidge farm
(edit) the problem ain't so much the drivers, it's the application and the injectors themselves.
Even peak and hold injectors probably won't idle properly in this application.

 

the driver output speed at that load is the problem. It actually doesn't appear to be an isolated GM ECM problem either, last night nightrider87 was pointing out that some of the megasquirt documentation lists it as having the same problem with more then 6 injectors (or was it 4… I can't remember now).

FWIW, I was testing this with SVO 36pph injectors (a little under 12ohms each) last night with the scope.

FWIW, does anyone have any pulswidth times for injectors at idle (just post what engine and what the injector flow is, and the driver used (which ecm…))? It would be interesting to compare dwell times with different drivers/injectors (the more examples that we could get the more useful the information would be).

At what point does the code/ecm go into quasi? Is this a 749 thing, a code thing or what? Does a 165 does it also?

 

BTW, GoSlash27, thanks for the link… I know that I should have looked there for it, but I didn't and those schematics should prove very helpful.

 

Nightrider,
I think if you run something like this:
http://www.overboost.com/obs/product.asp?pid=2628
You'll be able to keep it fed with alot less injector.
How much boost are you planning on running?

 

750 RPM, in gear, all day every day.

The drivers are fine, it's the inertia of the sealing elements of the injector and coil design that have the problems.

 

My 60 PPH injectors in batch fire mode, have a 1.8 msec on time at idle. 12277148, and is about the same with the 1227749.

Swing by, I'll show you how well the car idles, and runs. Really, it runs just fine.

Quasi has nothing to do with it. Or do you mean Asych?, but that would only apply if the on time was less then the min setting in the code.

 

Not hardly *alot less*. I have yet to see a FMU, or raising rate regulator work out well. And with some injectors they alledgely lock up at relatively low pressures, ie 70 PSI.

This fear of using large injectors is just unfounded. It started with the chip sellers just doing static chips, and not being able to understand what, and how to calibrate things for larger injectors. Or with guys not wanting to, or knowing how to get things right, IMO.

There are even some lil 231 Buicks, aka 89 TTA motored cars running 72 PPH injectors (P+H), with stock drivers (1227148), that have passed the IM 240 Emissions tests.

 

Isn't most of our preceived problem stemming from the addition of 2 injectors though.

You cite V6s that work, but are there any V8s using this converted code that can run the large injectors?

 

I'm running 42lb/hr peak & hold injectors on my stock 305. The 749 runs them no problem, you just need to work on the tune a lot the more you deviate from the stock setup.

 

Who's precieved problems?. So far it's just imaginary, Saturn 5 to name one guy on the TGO list runs his twin paxton setup on one just fine.

What converted code are you talking about?. The topic so far has been about alledged injector drivers problems.

Saturated injectors on the 749 aren't a problem, v6 or v8. If you want to run P+Hs then you need to do the mod drivers and sense resistors as outlined in the DIY Prom Board.

 

Well, Saturn5 is running twin M90's on his 305 and as far as I know he's only run the 749 with 22pph TPI injectors and 35pph peak and hold injectors (t-bird brown tops I'd imagine) (though I am curious how that's working and if he's got something similar going to the sunbird wiring or if the driver's are just dealing with it). In neither case should he have any problem with idle.

Yenko… 42 low Z… off of what? Are you still running the stock injector driver?

 

OK, this bugs me when people say things like this…

Manifold pressure referencing your fuel pressure only lets you keep the same pressure differential across the injector, if you didn't modify fuel pressure by the intake manifold pressure the stock code wouldn't work (yes, the stock FPR is refrenced)

 

83,
That type of regulator isn't the same thing as a normal regulator; It's nonlinear (rising rate as grumpy pointed out).
Read more about it in Maximum Boost- Corky Bell

Grumpy,
The problem isn't the ability to hit the minimum on-time, it's the lack of resolution you end up with.

 

Are you doing EPA, OEM level emissions work, and worring about CAFE numbers?.
Injectors at the lower PWs are crude anyway, look at some high speed photos, and you'll see how bad they are. At opening they just dribble fuel, and no sooner then the pattern really fans out, does it turn back into dribbles, as the injector shuts off. Not to mention there still is reversion, and some manifold wetting, and cross feeding of some of the fuel.
You can build an ecm that runs at 133 Mhz, and go to nanoseconds of resolution, but the engine is a slow erratic mess compared to code, and electron flow.

Not to mention even working a 90/256's % resolution on the VE table is more then the average tuner is going to do. Alot of guys only tune at 1% increments, and seem happy.

 

Grumpy,
Nah, just pointing out that running twice the injector on an application that's going to essentially have the same idle fuel requirement plays havoc with the ECU's ability to make fine adjustments.
I agree that all injectors become erratic at low duty cycles for the reasons you mentioned. So why force them to operate twice as far into this region?
So double size injectors=half the duty cycle (assuming same base pressure)=a 1% change causing twice as much effect on the AFR.
I'm not suggesting that a rising rate regulator is an acceptable substitute for chip burning, I'm just saying that running one in conjunction can allow you to do the same job with a smaller injector, which will help the motor behave in idle and cruise.
-John

 

Ran 30 lb SAT injectors (GN takeoffs) last summer, now running a modified 749 with different drivers and sense resistors with SVO brown tops.

FETS are HUFA76645P3 with the sense resistors doubled up stockers. (added an additional stock resistor to each driver circuit in parallel with the originals) which cuts the resistance in half as compared to stock (going from 2 injectors per driver to 4).

http://www.datasheetcatalog.com/data...A76645P3.shtml

So far.. (I just got the Malibu back together last night) all seems well, just need to work with the chip since I am using the bin from the 30's.)

The wiring is per the Sunbird diagrams. BW

 

Just discovered we may be pretty close to eachother. Check your PMs

 

That is not a rising rate regulator. It's an early 70's bosch FI regulator with the adjustment screw drilled to work as a vacuum/pressure nipple. Inside it only has a single diaphragm/piston, unlike a rising rate regulator/fmu. It works exactly the same way as a stock TPI or for that matter, most FI fuel pressure regulators.

 

It's by no means half. The opening and closing times take up most of the PW at idle.

Your worring about things that for other then CAFE numbers are mute. There is so much slop in the internals of the engine, that it really isn't that big of issue.

And the small ones, just can't do the same job when you get into Accleration Enrichment.

Why do you think GM oversizes the injectors so much?. If one was to use the .5 BMFC numbers they could get away with much smaller injectors. At 24 PPH, they should be making a min of 384 if not over 400 HP with them. Or are you going to say, the design teams at GM have it all wrong?.

 

The 42's are siemen deka injectors from mopar performance.

 

as far as i know there are people running every combination of injectors on this ECU with no problems....

it has become pretty normal to swap injector drivers and run 75lb or 84lb injectors on a syclone or typhoon with a 4.3l V6. the ECU has enought resolution to get a nice idle with huge injectors.

people have been running 8 high impedance injectors on this same ECU for a while now with no real issues.

recently there was a guy with a porsche on www.syty.net that was able to get his porsche V8 running with 8 low impedance injectors.

so whats the problem here? you can pretty much do anything you want to if you know what injector drivers to use...... guy with the porshe did mention something about haveing to use different resistors in the circuit as well, but it sounded pretty simple, and he claims to be building a website with pics that will show everyone how to do the same thing he has accomplished.

e