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1fast72nova
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 Posted: Tue Nov 03, 2009 1:28 pm Post subject: |
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no, no MSD, but as you stated earlier a couple of large transistors should do the trick to fire most anything I want...
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dieselgeek
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| Posted: Tue Nov 03, 2009 1:34 pm Post subject: |
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| 1fast72nova wrote: | | no, no MSD, but as you stated earlier a couple of large transistors should do the trick to fire most anything I want... |
Have you priced transistors that'll support your current needs at the frequency you'll require? It might save us all a lot of wasted time. If you can find them, they're going to be a lot more expensive than a whole megasquirt.
Which again begs the question "why do it this way"
For me, I'm just curious to see the attempt. I already know the outcome. |
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1fast72nova
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| Posted: Tue Nov 03, 2009 2:28 pm Post subject: |
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hahaha, then give me some pointers on this big cap HEI to TBI cpu....
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dieselgeek
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| Posted: Tue Nov 03, 2009 4:24 pm Post subject: |
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| 1fast72nova wrote: | | hahaha, then give me some pointers on this big cap HEI to TBI cpu.... |
which HEI module do you have? (how many pins)
All you need to feed the GM computer is a square wave signal that has as many complete cycles per engine cycle (2 revs) as a there are cylinders on the engine. Or, a less confusing way of saying that is: "any standard square wave tach signal"
You can make it run off an MSD (or any other) tach output. Or any signal that would drive a normal tachometer. A points output (within reason; you might need a current limiting resistor in this case). A pertronix module would work great. You get the idea. Your problem isn't the tach drive.
have you figured out how to monitor if you have the computer "alive" yet?
Here's a revised set of suggestions - let's break it down into the simplest of steps:
(1) Give all the grounds on the computer, a good ground.
(2) Give any/all power inputs, 12v. Don't accidentally put 12v onto the 5v outputs that go to MAP sensors and TPS, though.
Every time you connect up the power, the Fuel Pump relay control should trigger for 2 seconds. If it's a ground trigger, use a test light connected to 12v. If it's a 12v trigger, use a test light connected to ground. It should light up for 2 seconds, because the fuel pump primes for 2 seconds every time you key on the ignition.
I would get this going first before you worry about anything else. Once you have that working, then it's time for the next step. Does this seem reasonable?? |
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1fast72nova
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| Posted: Tue Nov 03, 2009 5:54 pm Post subject: |
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yes, and what I've been trying to do. Well for a bit anyways and gave up, pulled the chip and sold it. So next I make it to the salvage I'll grab another cpu.
back to the signal, I was thinking just hook the tach wire off the HEI to the cpu, problem is.. the cpu asks for a high and low reference... so I would assume i need a resistor on the low side.. but, lol... i'm stepping into an area I know little about here..
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dieselgeek
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| Posted: Tue Nov 03, 2009 7:35 pm Post subject: |
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| 1fast72nova wrote: | yes, and what I've been trying to do. Well for a bit anyways and gave up, pulled the chip and sold it. So next I make it to the salvage I'll grab another cpu.
back to the signal, I was thinking just hook the tach wire off the HEI to the cpu, problem is.. the cpu asks for a high and low reference... so I would assume i need a resistor on the low side.. but, lol... i'm stepping into an area I know little about here.. |
High and Low reference means '12v and ground' - the Ref pin on an HEI module is usually what you want, BUT - if it's driving another device already (another CPU, or ignition) then it might not be happy with the extra load of the new ECU you are attaching to it.
Are you any good with an oscilloscope? even the cheapest scope will work here (think 'classroom' or 'entry level, training scope'). You are probably going to need one if this project moves forward anyways... I use the "Parallax USB Oscilloscope" which was $125 when I bought it... you can make a home made one for next to nothing, using your PC's soundcard also... it would come in REAL handy here soon. |
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1fast72nova
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| Posted: Tue Nov 03, 2009 7:50 pm Post subject: |
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oh, lol.. so then I need to have the jumper wire from the dizzy to the coil installed and powered up?? 
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dieselgeek
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| Posted: Tue Nov 03, 2009 8:06 pm Post subject: |
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| 1fast72nova wrote: | | oh, lol.. so then I need to have the jumper wire from the dizzy to the coil installed and powered up?? |
Can you dig up an original wiring diagram? where did the Ref Lo and Ref Hi originally go to? I looked again at your diagram, you want to make sure ALL your ECU grounds are grounded - they're segmented in an OEM computer to keep noise out of certain circuits.
I'd like to see where GM sends the Ref Lo and Ref high in the OEM application, then I can help you figure out where to put them,
Oh, and that "Clint" guy who you're making e-love to on Speedtalk.com? I wonder if he's ever tuned an EFI engine. He just admitted that his "injection timing theory" was, at best, good for zero HP.
thanks,
-Scott |
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1fast72nova
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| Posted: Tue Nov 03, 2009 9:20 pm Post subject: |
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as far as a diagram, this is a GM tbi.. should be the same for most any GM tbi until 95 and even some of the batch fire MPFI
as far as e-love is concerned... I just said "thank you  " .. not like i gave him a reach around, did you get one b/c he was sure sticking it to ya 
lol, kidding aside, I'll see what I can find on the harness....
found this..
http://www.ih8mud.com/tech/tbi350.php
and of course, the dizzy needs to see a positive voltage from the coil or it won't fire the injectors as a safety precaution....
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Last edited by 1fast72nova on Tue Nov 03, 2009 9:31 pm; edited 1 time in total |
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dieselgeek
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| Posted: Tue Nov 03, 2009 9:30 pm Post subject: |
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| 1fast72nova wrote: | as far as a diagram, this is a GM tbi.. should be the same for most any GM tbi until 95 and even some of the batch fire MPFI
as far as e-love is concerned... I just said "thank you " .. not like i gave him a reach around, did you get one b/c he was sure sticking it to ya
lol, kidding aside, I'll see what I can find on the harness.... |
If you can get me a harness diagram I think I can give you better advice.
As far as Clint - he's definitely not sticking it to me... I am calling major BS on the "make more power with injectors timed with IVO" idea. I already know why the OEMs do it... and how. and what he's talking about, if there IS a benefit, is not measurable on a typical engine dyno. He even admitted that himself!
I've tested it myself on a number of engines. I called out the last "big name tuner" who claimed a big increase in power (.07%) by doing that. I'm ready for him to school me if I am missing something, but I already know what happens when you run injectors that are 3x too large for an engine. He's in there implying to "young guys" (tuning/EFI noobs) that they should oversize their injectors, put them away from the intake valve, and other EFI myths started by guys who saw the Youtube video of a 10-year-old Formula One engine on a dyno.
I'm curious how many EFI engines a guy like that has tuned. Little old me, I'm only up to about 400 of them. So many guys on that forum are bullshitting so bad - it frustrates the hell out of me that some people go there to get guidance on things like EFI tuning.  |
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1fast72nova
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| Posted: Wed Nov 04, 2009 6:25 am Post subject: |
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from the link above..
http://www.ih8mud.com/tech/ecmpin1227747/747ecm6.jpg
but unless you know how the ign module works (which I don't) I'm not sure how much it will help.. but i do see that I need to power the ignition module also..... which is probably why I wasn't getting fire (I did try to run a hot to simulate the coil but not the ground)
I say this b/c surely they figured if the coil was burnt there was no need to fire the injectors???
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dieselgeek
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| Posted: Wed Nov 04, 2009 9:19 am Post subject: |
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the link isn't working for me "remote linking forbidden"
AS for the coil, I am sure there's not that much logic in a mid 90s TBI computer to determine if the coil's bad, and not fire the injectors...
the module would need power, and ground, and everything else it needs in the car (except the coil, really) so that it can output a square wave and get a tach signal into the computer. Another reason a 'scope is super handy. You can look at the module's output, then work downstream from that. |
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dieselgeek
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| Posted: Wed Nov 04, 2009 9:21 am Post subject: |
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| OK I got the link to work. As soon as I get a minute, I'll try to figure out where the ref hi and lo come from. |
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1fast72nova
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| Posted: Wed Nov 04, 2009 7:41 pm Post subject: |
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well that's probably a question for spidey...
but it would seem to me that it wouldn't have to be in the brain, only the module.... ie, if the module isn't getting 12v or sensing ground from the coil then no need to send a pulse to the cpu to fire the injectors and end up with a flooded motor...
BUT if you can figure out how to fire this thing from a big cap hei it doesn't matter...
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