With my combo (check sig.). I will be going DFI to squeeze the most out my setup. Right now, I'm looking into ACCEL and Holley. Any comments or suggestions? Is anyone outhere using a Digital Fuel Injection setup on a LTR style Chevy small block? I've been talking to a reputable speed shop / performance tuning shop and they said I should have no problem squeezing 400+HP to the REAR with my combo and a DFI setup. Man....I cant wait till I have the dough to go digital!


Mike (1bad91Z)

 

Double post....

See aftermarket review

 

I know that I double posted, I thought I may have better luck in the DFI section! I havent run across anyone with DFI yet!!! Maybe soon!

 

It's easy to talk yourself into more than you really need.

Fact is that a factory ECM is a good choice, if you will learn how to burn chips.

However, even that isn't free, and by time you buy everything, you are in the price range of a Accel Gen 6, and close to half the cost of a Gen 7 Accel.

Since you appear to be the type that will always want more power, the Gen 7 is an excellent choice. Above that would be the Electromotive TEC II and then for all out blown, NOS and staged injectors, the TEC3.

 

I think that I've narrowed it down to the F.A.S.T. DFI bank to bank setup with the wide band o2 and Ccom software. All the speed shops down here recommend it over any other DFI setup.

 

you already have a bank to bank digital fuel injection controller under your hood. i would suggest looking at using the factory ecm. it might sound wierd but it will work just fine with about as much hp as you can throw at it. i have used fast and its a big pita. to setup. all the wiring and other nosnes. use what you already have.

 

Maybe you know something that the rest of us don't, but I've yet to see someone running an older GM ECM (like 165, 730, 749, 748...) successfully with larger then 36# injectors. It just won't control them accurately enough to idle right.

If you know how I'm all ears, I've got a set of 77# high Z injectors waiting for my car and I would kill to do something as simple as repin for a 730 and run Sy/Ty code (or repin for a 749 and modify the syty code for 8 injectors), but I don't think it will happen. I have had exactly those injectors idling well with both an Electromotive TECII and Haltech F9 (I really only need mid 50’s to 60's, but I've got the 77's)...

 

The GN guys can use around 50 lb/hr injectors on the factory ecm's, can't they? Of course, those are SFI ecm's so maybe that's why. If that's the case, an 8051 ecm from a LT1 would work. However, that means getting a 8051 and an opti spark and then adapting the opti to a conventional SBC distributor. Before long you are at the price range of an aftermarket EFI, although not a SFI one, or has the driveability of a factory ecm. But, if you get the opti working with a 8051 then you can add the LS1 coils for like another $600. Pretty nice set-up for around $1200, depending on how much machine work is.

 

ok ill look for the schematic for the off board driver. basically with injector that large you are simply drawing more current than the ecm has avaiable in such a short bursts. i have never even attepmted to use 77# inj. to be honest even the aftermarket systems wil struggle with injector this big. let me see what i can dig up. what you need is a higer gian transistor with a more powerful output. sort of non exsistant. so and off board rvier is a better choice. ill see what i can find.accel makes a box for this BTW.give me a week ill have to redo the schematic i did for the last one i built. held onto 45lbs fine dont know about higher than that thought?? wasnt stressing or anything.

 

yep, that and I’ve never heard of anyone adapting one to another application.

Hum, the funny thing is that I’ve already had that idea a bunch of times. To add to that I’ve got a ’95 LT1 ECM and an optispark that I can tinker with, and it doesn’t look too hard to adapt the opti to a distributor (I’ve seen pictures of it done also).

The biggest question is what do I do for a harness and is it worth the effort (would I have been better off going aftermarket by then)?

 

OK, this is something else that I keep hearing that doesn’t make much sense to me. Why would larger injectors draw more current? Yea, I can see if you need a larger/heavier pintle, but the fact is that the ‘valve’ part of injectors flows much more then what the injector flows, and the flow is just cut down using a metering plate. 77# injectors are 36’s with a modified metering plate….

Hum, unless you’re getting at that you need to supply the current the injector would draw faster to make it work right (to put it in fluid terms, you don’t need more capacity, but you need a bigger pipe/valve to get the capacity that you’re using there fast enough)?

 

I think he didn't read the part that those injectors are high impedance, not low impedance (peak & hold). That's what the offboard driver is for, to take the brunt of P&H inj's. It still wouldn't do anything for idle issues with high imp inj's since the injector wouldn't run at the required pw.

Now the LT1 stuff has issues I know but not bad ones. The harness needs to be aquired from a totaled car. I'm, sure a junkyard somewhere has one for a reasonable price. If not, what you need is the connectors with at least a foot of wire on them and then add your existing harness to it and make the rest up. I believe the connectors are available aftermarket. Whether it's worth the effort is up to you. I know I can't guarantee that it'll drive 77 lb inj's correctly but I know this for sure: that ecm is more advanced than anything the aftermarket has to offer and driveability is great.

 

I’m not sure if this is what you’re saying, but if it is, this is something else that I’m finding to be a fairly common answer that as far as I know is not true. The idea that a large high Z injector just won’t open and close fast enough to idle. To be blunt, that’s a load of crap. I know of a bunch of cars that run these and are fine with an aftermarket ECM. I’ve got experience with 2 specifically, one running a Haltec and the second Electromotive that both idle under 1000rpm (I believe both are actually under 800, but I know for sure that they both idle at lea tuner the 1000) and pass emissions (one the treadmill test in MD) with these injectors. Drivability is indistinguishable then when they were running smaller injectors with the same computers.

Based on that, the answer “it can’t be the injector driver since it’s switching is done solid state, it’s very fast. It has to be the injector” is just not true.

 

That’s somewhat the reason that I’m looking at it. The fact is that it is probably more advanced then most of the rest of what’s out there, and there are a bunch of 700+hp cars still running them. The other fact is that the drivability and other goodies are obviously much superior to what you’ll find in an aftermarket ecm.

What I would like firm answers on before I would consider spending time and money going this way:
- Why do people seem to go aftermarket at some point anyway? What is the limitation of this PCM?
- Will the MAF survive a blow through application? I’m going with twin turbos and that appears to be the only good way to deal with that. I’m positive that I’m not going to mess with the wiring/electronics/packaging issues of trying to run 2 mafs on the car.
- What is so special about the optispark signal? I’m not sure why the pulses it supplies are that different from the other triggers used in distributors, crank triggers…, but almost anyone that knows something about the thing insist that the LT1 setup has to be triggered off an optispark sensor.

 

no the problem with the older injector driver in the P4 C3 ecms is they dont have enough dwell time to open a larger high impendce injector fast enough. the driver will actaully pulse down quite low. the problem is really that the collecter in the transistor cant store enough current for such a short pulse. nor does it switch well down at that small time interval. so its hardware not software thats the issue. so really what you need is a higher currnet driver. and remeber that a high impedndce injector actually require more current to fire than a lowZ injecotor. the thing you wont get is the inductance current issues. still ill dig for a injector drive board and ill get some realy large injectors. also if this was true wouldnt the 65lb per hour low impenece 747 TBI setups have trouble ?

 

I really don't see the need to change to an aftermarket ECM at your level of HP. Get yourself the equipment to burn your own proms and go at it.

 

double post.

 

hmmm hardware is correct, but is it due to the driver circuit, or the type of injector?

Let take a look at some waveforms and find out.

First a Ford saturated injector.



If you look closely you will see where the injector opens, where the waveform "knees".

Lets measure the time it takes to "open" the injector.



1.456 mS to open,



with a total pulse width of 3.6 mS.


Now lets look at a GM TBI P/H injector.




The "knee" is less prominent than the Saturated injector.



and it takes .8 mS to open.



with a total of 1.6 mS pulsewidth.

Now your results may very, these are not my waveforms but the theory of operation holds true. Since a Saturated injector needs + 1 mS to open, you can see why high lb, high Z injectors have problems at idle. You can't trim them down enough to limit fuel without surpassing the physical limits of the design. Smaller lb injectors work fine at idle since the pulsewidth is longer for a given amount of fuel. BTW all info taken from http://www.cnnw.net/~fourty/injector.htm

Crossfire, I think this will also answer your questions too, bet this is the reason why the 165,730/749 have problems with >36 lb injectors at idle. cheers, Bob

 

Damn Bob, that's what I wanted to say but didn't have the nice charts to point it out. You da man!

 

Can't give a firm answer but probably most people that went aftermarket didn't know the factory ecm was hacked and could be played with. The others just didn't want the hassle of dealing with all the factory tables and didn't care about driveability and the "easier to tune" aftermarket ecm was better in their mind. And I'm sure more than a few people wanted to get rid of the opti so ditching the factory stuff was the way to go. Then of course some people just needed an aftermarket ecm and it's flexibility with hardware and software as cost was not an issue when they had already spent $10K on an engine.

I know of one person that puts 20+ psi through an LS1 MAF. It's a "Black Car", as he calls it.

This I can answer with all certainty. The opti sends out two signals. A high resolution for crank reference (lots of little windows) and a low resolution (only eight windows) for cylinder reference for the SFI. This is why you can use an opti to trigger the LS1 coils! You said you have one so take a look for yourself. Now, to overcome this would mean to completely rewrite the code in the ecm to see whatever type of cam and crank reference you want it to see.

 

My consern isn't boost, for that matter I'm not sure how boost would damage it. What I'm worried about is the fine coat of oil that the intake on turbo cars inevitably gets.

Thanks for the rest of the information.

 

The 749 can run 50lbs/hr injectors no problem. And a guy that calls himself the canadian on syty.net is changing out the factory injector drivers to run peak&hold injectors. They are running 70+lbs/hr injectors with the 749.

 

Found it....

http://syty.net/phpBB2/viewtopic.php...hold+injectors

Heh...figures, I just sold 4 low z 36 lb injectors and bought a set GN 30's for 50.. broke even anyways..

anyways looks like the SyTy guys have their act together on the 749. +70 lb injectors and 3 bar bins.. and looks like Promgrammer been upgraded. Least its only 10 bucks.


Life looks good... cheers, Bob

 

To all - I've played with Cal-Map and Ccom. Ccom (software for FAST DFI) is very user friendly, unlike burning a chip. I do not have the know-how nor equipment to burn my own prom's. Therefor unless someone here can burn a better chip than Ed Wright for a combo that is not in front of them on a scan-tool, then I cant see a better choice than going digital. Maybe someone here can prove me wrong!

Mike (1bad91Z)

 

739, 749 ECM, pulswidth, graphs, in other words,

"WHATCHA TALKIN' ABOUT WILLIS?"

 

get a eprom burner and a memcal adapter from www.moates.net i can help you via email. if you dont get started youll never get going. and the factory system really isnt so bad to tune.same learning curve as a aftermarket ecm. just no flash. if push came to shove get and emulator so you only have to burn chips when your happy with your tune.

 

Funstick - I am running a Custom PROM from Ed Wright (the chip was made for my combo in the Sig.). My question to you is what would I need (besides the EPROM burner) to send you data to show you what the car is doing? Do you use tunercat? What is the best software out there to do this? I hear that WinBin sucks and that Tunercat is the way to go. I have a laptop with Windows 98 on it. I can buy the cable (laptop to ALDL) pretty soon. I just need the best scan/calibration software that I can get. Could I actually copy the BIN from the Ed Wright chip, then make changes to that copy and burn a new and improved chip, or would I have to start from scratch?



Mike (1bad91Z)

 

Funstick - where ya at?

Anyone?

 

No you use programs like tunercat to modify the information on the chip. To see what your car is doing you will need a program like datamaster. You can get it with the cable for $219 or AKM cable sells it for a couple bucks cheaper. Yes you can take the data off of the Ed Wright chip and modify it for your car.

 

im am in baltimore MD. your in texas. first thing would be to get a good scaner ad see whats going on in there. second a good eprom programmer. as for tunning software i sort of have a fancy for tunercat (shameless plug huh??). there stuff works great everytime and there is no checkusm mess's or saving errors that ive ever noticed.

learning to tune the ecm via the eprom is not to hard. some hardware suggestions are a moates adapter(shameless plugs LOL) with a zif socket. 1-2 flash chips (makes tunning easier and you dont have to deal with an eraser)

playing with the spark fuel and other tables isnt that hard once you know where to hit it with a hammer. finish your new combo and get some scans. also start reading over at the diy prom board.

your program id for the eprom should be $8d. you should have a 1227730 ecm. your ecm uses 27c256 UV earase able or 29c256 flash chips

www.xtronics.com (pocket programmer is nice.)
www.ustr.net ( software hasnt cuaght up to the hardwre yet cant do the flash 29c256 chips yet but there gonna have it really soon cheaper than a pocketprogrammer.)

getting diacom might not be te best route as www.moates.net has some free software that comes in very handy. just take a bit of getting used to

www.akmcables.com makes a inexspensive aldl connecotr cable
that works with a few scaners out there.


thats my 2 cents on where to go to get what youd need. tuner cat should run you about $90 buck with the sofwtare liscnces and TDF file for your code.
just in case i forgot www.tunercat.com (duh more plugs LOL)
my email is

djfreggens@aol.com

drop me a line id be glad to help.oh and if you happen to email tunercat please drop my email addy in there ear let them know i sent you. Thanx as for me helpping you wit interpreting the scans that gonna take some dilegence on your part. once you get a grip on what happengin and how to afect change you will find youself going forward quiet easily. as for what i would need ?? ahh good notes

rpms with blm and map readings. what bin your starting with so when i open it in tunercat i can look at it and think about where a good change might be. tunning for wot via email will be tough but lets get the idle driveability and other things out of the way first. baby steps.by the time you get to workingon WOT you wont even need my help anymore.

 

Thanks!

So, what, I'm looking at a ~$300-$400 total investment?


Mike (1bad91Z)

 

yeah figure closer to $400.my current equipment outlay is significantly higher but then again i have alot of other goodies that you can live without. but $400 should be very doable and much cheaper an less messy then say a aftermarket ecm. as fr as i know the 122730 ecm should be able to support at least 500hp
without any driveability issue. welcome to the club.