Well I soldered new fets in my ecm and installed a set of 8 lowz 35lb/hr injectors from a tbird turbo. I took it for a spin around town and it runs great and the ecm stayed nice and cool. My only question is when I wired it up like the turbo sunbird with the injector jumpers it wouldn't fire, so I wired it up like a sy/ty with the injector grounds and it fired right up. My question is how do I know my ecm is peaking and then holding the injectors? Anyone with knowledge on wiring up P&H injectors tell me if I did it right.

 

o-scope the sense resistor getting feedback and going to the p/h driver chip. see if its actually producing a p/h signal. wont do any good to o-scope the injector switching itself. the inductive kick back makes it look very odd.

 

Sounds like you are making great progress. Good job!!

 

None EE alert,
As I understand the wiring, if you have it wired like a Sy then you have the sense resistor for the P+H bypassed. It's the jumper that enabled by changing the ground that inserts the sense resistor into the system

I've been running my P+Hs, in the none P+H mode, thou with the driver change. Only 6.

 

The strange thing was the car wouldn't start at all wired like a turbo sunbird, but when I grounded my injector ground wires to the door jam it would. The car ran really rought though and wouldn't rev very well. I think I'll look over all of my ground wires to make sure everything looks good.
Grumpy am I understanding you right that my computer is basically running my P&H injectors like sat. injectors wired up like a sy/ty. And I need to jumper the ground pins like the turbo sunbird to get a true peak & hold?

 

Thats my understanding too..

SyTy wiring is for SAT injectors and uses one driver.

Sunbird wiring is for P/H injectors, adds the second driver.

I've had it running on my bench that way, but have not switched the Malibu yet.

 

Yeah I'm running both drivers, but instead of using the jumpers I grounded them.

 

The jumpers are what put the sensing resistors into play, as I see it. The Sunbird is P+H and uses the jumpers to set the sense resistors. Unless wired as the Sunbird, then your in the Syclone strategy, which is saturated.

 

the driver chip in the 749 is basically a custom version of the lm1949. once you get your injectors running on the bench like i siad oscope the sense resistor and see what the current looks like. could be that the sense resisitor could need ot be changed out for it to have enough peak time to switch the injectors on. with the bigger fets the driver chip might be comming up short on maz peak time and thats why the injectors wont open. try it first with a few 4 - 6 p/h's and see what you get. either way the sense resistor could very well be the culprit. either that or its detecting so much current from the intial switch on its immediately going to hold. at any rate sense resistros might need changing. if you need info on calculating the change in resistor values check out the LM1949 pdf at the national semi website.

good luck.


ps if you have a hard time finding the proper sense resistor let me know ive got some laying around.

 

Ok I'll try 4 and 6 injectors and see what it does. Just for refrance I'm using fairchild semi pn NDP6060L fets.

 

According to the national semi lm1949 pdf it looks like I need .1 ohm sense resistor for 4amp peak 1amp hold. I'll see what the current resistors are in the ecm. Thanks for the link to the pdf.

 

Well I tried it with 4 injectors and it fires them great, when I add 2 more it will barely fire them and 8 is no go. So as I understand it I need to put a sense resistor with a lower resitance on the injector controller to kick up the amperage. My only problem is I can't find it by tracing the etching in the pcb, since it is multi-layered. Does anyone have a schematic of a 749 pcb layout? Or can someone point me to a source? I see that the diy-efi site has been down for awhile.

 

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

R76 and R93 .103 1% 2W.

courtesy of Ludis..

BW

 

the trace will come from drain. you would actually need a higher resistance i think. you want the driver chip to see less current not more.if its see less current it will try to drive it harder. i dont really know exactly how adjustable all of this is. i dont think you could change the resistor that designates the peak time becuase i think GM had all that put on board. so thats a no go. but changing the snes to a higher resistance would help. also you have to enable the sense resistor VIA jumpers. id trace back from the pins for the jumpers and see where they go. a depopulated ECM would go miles to acheiving this. wish i could find mine. anyways my understanding is that the junpers that enable P/H actually are the sense resistors.

good luck.

 

You'll want a .05 ohm resistor to provide 8 amps peak. This part should be sized as a 5W power resistor. Bear in mind that once you get down to that low of a resistance, connector and wire losses become a big part of that. You may want to hardwire the jumpers by soldering them in the ECM underneath the pins where they would be jumped. This will get rid of the wire loops and connector resistance and provide a full 8 amp capability. Hope that helps.

 

Thanks for the information guys. I found the schematic and will make a trip to radio shack to see if I can find some .05 ohm 5W resistors. I'll let everyone know how it works, once it's completed.

 

Or just ignore the P+H setup entirely, and just some some large MOSFETs.

I've run the low resistance injectors in none P+H designs for hours without a problem on the bench, trying to break them.

Some have suggested, that it's no big deal driving an injector either way. While the P+H saves a lil electricity, the only thing you can see is that the injector takes a couple usec longer to shut off.

 

Grumpy, thats how I am running it right now. I soldered in some higher output fets and am running them in on/off switch mode. I would just like to run them in p&h mode and see if it makes any changes to my idle stability at low pulse widths.

 

I'd recommend that you parallel the current .1 ohm resistors with another .1 ohm. This will double the PnH currents. You should also use 1% 2W resistors which you won't find at RatShack. Try Digikey.

Don't worry about adding other wiring jumpers and such as they are not in the measurement path.

RBob.

 

Well it worked! My car is running P&H injectors like they should be. My battery was dead in my laptop, so I couldn't datalog. But I drove it around town and it runs just as good as it did before with one exception (it purrs like a kitten now at idle).

Thanks for the help guys.

 

How about a final write up with exactly how you did things?.
Maybe a pic?.

 

I don't have a website to post a pic. But all I basically did was replace R76 & R93 with .050 1% 5W resistors. They are located really close to the injector drivers. You'll be able to see the numbers silkscreened underneath them (hard to see). For your application though you'll most likely need a .070 resistor for the V6.

 

Glad you got it sorted out.

BTW you can attach a pic directly to thirdgen. No need to host for a single pic.

Bob

 

Ok I have a pic. How does one go about putting it in a message?

 

In reply, below it, see where it says attach file.

click browse, find pic on puter and load.

note you may have to resize it so its under 102500 bytes.

 

Ok here is a pic. You'll notice the 2 resistors next to the left heatsink. Those are the new ones and they are much larger than the originals.

 

i am in the middle of my supercharger project, and found this post. I am using a holley 4bbl tbi and 749 ECM in P&H mode, and found that my 749 will not drive four P&H injectors.

Contrary to what I have read :-(

I have all of the parts for an injector driver board sitting on my desk as we speak. Would you recomend I go ahead and build it or take the bigger transistors and solder them into my ECM? The driver board schematic i have uses darlington NPN 100V 8A transistors and shows that .05 ohm current sensing resistors should be used for two injectors per driver as you posted. I currently have them wired in series and it works, but not well. I also noticed that when operating only two injectors they seem to operate with authority(a sharp sounding clicking) and right now, in series, they are rather quiet. The resistors i ordered are of the .1 variety since i was going to use this on a 747 ecm--dont ask me why :-(
Also, if you think i should solder the transistors in, would these be suitable?
thanks

lou

1989 2wd short box s10
355/700r4/B&M144/4BBL TBI/Syclone ECM
http://home.epix.net/~lout/divxS101.avi
http://www.v8s10.org/gallery/view_al...umName=album19

 

The 749 will work with 4 Port type P+Hs. They are 2.4 ohms as compared to the TBI P+Hs that are 1.2 ohms.

I see the external driver board as a better option. While it raises the level of complexity, it means less likely hood of a ruining an ecm. If you didn't already have the board, I'd say keep the saving towards getting a spare ecm to keep with you.

Injectors are voltage sensitive. Running them in series drops their operating voltage is half. Yes, their clicking gets muffled at the lower voltages.

 

wow...that was a FAST reply

I havent measured the resistance on the holley injectors yet, but what you are saying is that the injectors I am using should be 1.2 ohms each and the GM TBI injectors are 2.4? I guess I have/had something else wrong with my setup then. Could low battery voltage to the injectors, or too small of a wire for the injectors be a problem too? It looks like #18 wire and there is only 1 for the B+. You are extremely well versed with GM FI from the posts and stickys that i have found on the net. I saw the post or sticky about 4 P&H's and the 749 and went with it. That is why i was kinda suprised that it didnt work for me. I must have something wired up wrong or undersized.

good deal

thanks

1989 2wd short box s10
355/700r4/B&M144/4BBL TBI/Syclone ECM
http://home.epix.net/~lout/divxS101.avi
http://www.v8s10.org/gallery/view_a...bumName=album19

 

TBI Injectors are 1.2 ohms, and are, Peak + Hold

PORT Injectors which can be, Peak + Holds, are 2.4 ohms.


In the Sunbird Applications the 749 was used to fire 4, PORT, Peak and Hold Injectors. In the Syclone application the pinout was different and it was used with 6 saturated injectors. Satuarted being 12+ ohms.

 

can anyone speak on the advantages of running the ECU peek and hold vs. saturated on a set of (6) 75lb low z injectors?

all i did was swap the injector drivers, installed the (6) 75lb PTE injectors and went with it. (tuned till i was blue in the face) things seem to be great like i have them, just curious if theres a worthwhile advantage to going to the sunbird wiring.

e