I am currently running 24#/hr Ford Racing injectors in my NA 395. The PW at idle is about 2.1msec. Also, at WOT I am almost running out of fuel (DC 90%).

Do you think that I can install 42#/hr injectors and be OK at idle?

Also, with my TTA fuel pump at 236#/hr (144 liters/hr), will I need to upgrade the fuel pump also? I have half a notion to install a supercharger.

Any suggestions?

 

I run the SVO 30# in my Formula(including new 383) and have no idle issues.

Grumpy and I both run the 65# Inj. on our boosted 6's and have no idle issues, other than playing around like any other setup :-)

TTA pump is not that great(was by factory standards), if you intend to boost a 396 you definitely would want more for insurance and I would step up to a walbro 340.

later
Jeremy

 

Well, that is what I was thinking about the TTA fuel pump. Its barely pumping enough now. With 42#/hr injectors times 8 inj gets me 336#/hr and the TTA pump is rated at 236#/hr,,, just wont cut it.

I was trying to estimate the idle PW with 42#/hr injectors, and its appears that the PW would be around 1.0msec or even higher. So, I should be OK here.

Do I need anything special to use 42#/hr injectors? Will the run off of my 165ECM? (with an appropriate inj constant, of course)

 

I would not call 1.0 ms OK in any way (on saturation injectors), unless you had a good quasi-async (or single fire) mode. Injectors are usually sized to the horsepower output requirements (and BSFC, and target max duty cycle). Depending on the BSFC (or efficiency of making horsepower from a certain amount of fuel, in lay terms) 8x42's can support from 520 hp (at BSFC of .55) to 635 hp (at BSFC of .45) with a max DC of 85%.

I ran your setup through my "stuff" and using 450 hp, and 450 ft-lbs of torque (and BSFC of .45), and it says 30 pph is Good, but 42's will also work OK. The cam used will play the biggest role in the idle PW's though. Lopey cams are poor air pumps at low RPMs and this requires less fuel per intake stroke, and is hard to estimate what it'll need, and whether you'll be idling closed loop, or just running it open loop at whatever A/F it takes to keep it smooth. I don't know your setup though, so interpret this how you want to.
With a supercharger, the power range of the engine is extended beyond the typical range and it means the typical injector and injection modes may not be easily capable of supplying consistant idle fuel with enough high hp fuel - one of the inherent beauties of sequential and either peak and hold injectors or newer quick opening injectors.

 

I'm running 42#/hr peak and hold injectors on my stock 305, so you should easily be able to use 42#/hr injectors on a big inch small block. Just swap over to an aftermarket or modded 749 ecm if you plan on a blower. As both computers will control the larger injectors and read positive manifold pressure.

 

I have been searching for injector PW stuff for the 749 ECM and came across this thread. What you say does not make sense at all.

The 730 ECM reports the PW for the current mode and the mode that it is in. As an example, if the PWs cause the 730 ECM to enter 'single fire' mode, then it reports the single fire injector PW and that it is in 'single fire' mode. If in double fire mode it reports how long it squirted the injector and also that it is in double fire mode (squirted twice).

Where you just referring to the 749 ECM and assuming that it always reports as it is in 'double fire' mode? This 749 ECM is confusing the heck out of me so far. My next step is to find ALDL def. file for it to see exactly what it reports....maybe it does report different fueling modes.
Of all the threads I have been reading lead me to believe that there is a lot of confusion about how the thing works......still looking for a good hac of the $58 code. I came across one that is a good start.

Also, the quasi mode seems strange in that it fires the injectors once for every two reference periods (not DRPs). At 750 rpm, it is firing the injectors once every .320 seconds. Seems like a long time between fuel..pretty course. I think I am getting curious enough to through an ECM on the bench to see how the thing really works.

 

Yeah, that was assuming the possibility that maybe the datastream was reporting the effective pw, not actual. It was just a prod to get the person to look into the actual injector pw for himself (since 1.0 ms is too short to get hardly any fuel out, even if the turn on time was not in there). Saturated injectors (when using an oscilloscope to see the voltage trace) should be kept above 2.0 ms actual. Sure there's exceptions, just stating a generalization. The main reason is that the injector flow does not follow the duty cycle at low PWs.

 

Sounds good. I just wanted to double check.
Since I don't have an o-scope handy right now I am going to use the digital control to the injector driver to see if the reported PW includes the turn-on and turn-off time. I am guessing that it doesn't because how would have GM really known this value.
My guess is that my current idle PWs of 1.7ms are actual 'fully open' time. The digital signal will look something like 1.7ms + 1ms_opentime = 2.7ms.

Just a guess.

 

The added 1ms would need to be built into the code I'd think.
I haven't verified this, but I think the 8D aldl reports the acutal register value for the inj pw. Also, some bins have an injector bias which I think might be your 1ms time addition also. Not sure.
So many things to research.
I know a couple of people that were working on the $58 hac.
Actually, I think it had $59 as the ID. Only the cal section was done. Very little of the code section.
I think they gave up and switched to the $60.
I look forward to your results for when I start my Turbo build in a year or so.

 

What you wrote about the injector bias makes sense becuase I see no other reason for it when doing the inject PW calculation.
I will have to look at that table again and see if it is inline with an injector opening time. I found on the web that the saturated injectors look like there are a 3.5mH inductor.

The project has been good so far. As usual, some things take way longer than originally planned. You wouldn't believe how much time I have into bending sheetmetal just for the cold air boxes. Turbos are cheap horsepower if you figure out how much it costs do to it N/A. Yeah, some say it is cheating, but every time I drive a dump truck and the turbo spools ya know that it would be a lot of fun in a car.

I came across a couple threads about the $60 code but it didn't look like a production piece. It looked like something Grumpy made himself and is not public domain. So I figured that I would start from scratch with the $58 code. I haven't checked out the Syclone group yet to get some more info. Just been too busy grinding and welding. I wanted to order the injectors this week so I started to look into what I should get. It is more involved that I had figured, but I want to get some that I won't be swapping out in a year.

I should have some info on the PWs around the end of the month.

 

Lets just say if you opened the $58 & $60 asm files side by side. You'd close the $58 first....
Unless you'd like to comment ~200 pages of code.....
Bruce did a great job of getting it into a form so that you can do whatever you want with it. I lack the attention span to do what he did.

I read a post on turbo's to the effect that a DIY effort will take years off your life. Luckily I read it after I'd starting buying parts.

 

The turbo project is a good project. It does take a bit of time but I think it is worth it.

I searched for the $60 code but didn't find out much about it. It wasn't listed at the diy-efi site. Some good Sunbird schematics were though. Showed the jumper wires for the peak-and-holds.

I looked at the 730 code and the 'low pulsewidth' injector offsets. I think it proves you are correct about what you wrote. I think the ALDL reports the calculated PW that includes this value. So the ALDL reports the PW for the entire injector turn-on to turn-off time. Seems strange though. My current idle PWs are 1.7 with saturated injectors. That would mean they are open for less than 1ms.

J

 

You'll have to bug the author to get a copy of the $60.

Low PW offset- I knew I'd seen something in there. Thanks
I plan on saturated 60's, 730-$60 & a T70.

 

It sounds like the $60 is good. I will have to ask Grumpy if he is willing to hand it out.

Not sure how the $58 handles low PWs exactly right now. But the 730 does it using the bias and going to single fire mode.

I first thought of using staturated 60s but then figured that 72 P+H would be nice because I would never have to upgrade again. Of course, this puts me in a bind because they are too big....but hopefully I can correct for them with the ECM. I went with a couple of T3 60 trim units. It is a junkyard setup so it is nothing fancy. They will blow for more horsepower than the block can handle but the adjustability is nice. A T70 sounds good. How is the availability on used stuff that big? I looked at some big truck turbos, but decided to stay away becuase when it comes down to it I really don't know what I am doing when dealing with boosted stuff.

 

I don't remember the offset so add it to the address.
Try tables at 4E2, 619, 62A.
I think I remember Rbob talking about one of them in relation to idle and injectors.

An HX55 comes on Cummins engines and looks similar in size to a T70. Have to dig around on TM for a HP number.
A new T70 is in the low $800 range.

 

I ran the numbers again for the 72#/hr P+H and it is too close to the hairy edge for my setup. I decided to get some Ford 42#/hr injectors for the time being. They will meet my initial horsepower goal for now. I need to spend some time learning the basic turbo tuning stuff so I figured it was better to go this route. If all goes well I can get the bigger injectors next year.

I asked about the $60 code but it sounds like it is a dead project and he recommended a $58 hac that someone started. I have read through it and I am currently removing a lot of the comments because they are incorrect. It is a great start though. I am splitting time between that and plumbing lines. I hope to fire it up in a month or so.

J