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Old 06-11-2007, 02:03 AM   #1
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Default I broke ohms law

and ohm won.

So I went ahead and borrowed a friends car (and took a week off) while I started to make major progress on squirtsville. Shipped the supercharger off to get rebuilt, got my 440cc injectors back from the cleaner, finished the PWM mod, WI circuit, got knocksenseMS wired up, used Al Hounos's map as a base, and got the car running great (alot better than attempt number 1)

Attempt number 1 was roughly 2 months ago..

followed directions blindly (didn't think about it) and put the TPS vref on the same wire as the signal. This caused the stock ECU to think it was tipping in and made the idle (still controlled by stock) terrible. Killed the TPS too... had switch back to the stock ECU for fuel and raise the idle to 2000 to keep from stalling at decel. ( I reset it back to 850 before starting the megasquirt install this weekend). AND I had the injectors batched at 1&3, 2&4 but on INJ1 and INJ2, not INJ2 INJ1 as it is now (and seems to be much happier that way)..

Supercharger didn't get back till Saturday so I didn't get a chance to start tuning till this weekend. I'm much happier now that it appears to be working so I can start playing whackamole on individual issues rather than pulling my hair out going ITS ALL BROKEN WAAAAH.

So - current issues (literally).

I'm trying to keep the stock ECU in the car so I can pass smog, using a switchbox similar to cjernigan's for switching idle/spark/fuel back and forth. Now that I've installed the 440cc's I'm past the point of no return. Much of the wiring harness is shared sensor-wise. Trying to tune idle, we turn the car off and hear the radiator overflow burbling. I thought I might've screwed up easytherm, or blown a fuse (I had a few fuses pop installing the aquamist pump.. long story) or relay somewhere. After doing end to end ohm checks, everythings fine. Finally realize that HEY YOU CAN'T SHARE THE CLT CABLES FROM MEGASQUIRT AND THE STOCK ECU. (now where's that head banging into wall emote).

So - before I go about adding the GM coolant sensor into the heater core hose (which will be a pita since the JSRC takes up alot of that space) anyone know what I can cut to get the vref power off the megasquirt? both the stock ECU and megasquirt appear to use 5v..

second question - PWM circuit seems to be almost completely unresponsive at any frequency setting. Diode is soldered across the iac. I disabled all warmup enrichments, etc - but idle seems to want to jump up to around 2k and stay there when I turn idle control to the megasquirt. I'm going to go back and doublecheck the circuit, but does anyone have a hint?

third question - I am running low impedance injectors, I believe I've got them tuned correctly according to the megamanual. In case I want to add ballast resistors (after I get idle working on MS and try to retune them..) where would be the best point? Can I add them on the wiring harness on the MS side, or do they need to go on the fuel injector wiring harness?

last question - is there a major difference between a 1n4002 and a 1n4003 diode for use in a pull up circuit (in my case, for the water injection output).
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Old 06-11-2007, 02:36 AM   #2
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Didn't you challenge murphys law instead :gay: i see the electrical pun but hey **** happens. GL man
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Old 06-11-2007, 03:11 AM   #3
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The people i know that have tried to use low imp have wired in resistors because they had problems with them otherwise. Might want to add the resistors to take that possible problem out of the loop.
Are you sure you wired the diode into the PWM loop correctly, if backwards it could be blocking all signal.
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Old 06-11-2007, 03:35 AM   #4
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Pretty sure I wired the IAC correctly... wonder if that oscilloscope I got from the HAM fest for free a few years back works..

I can't find where I found it, but this is the picture I referenced putting the diode in. - I just noticed the TPS looks like it's from a 1.6l though...



And I've been lurking and reading lots for awhile - I remember people having troubles with low impedance, partially why I want to wire some in...

so - MS or injector side? 1 ballast of sufficient ohmage per injector, or 1 per batch on the MS side (4 ballast resistors vs. 2)

I swear when I finish this project I'm going to make a writeup of how not to do things...

forgot to mention - i've tried using aussiejim's and MSPNP values for the IAC, but no effect... gotta be something in the circuit methinks... or that picture is wrong - white band to white/red.
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Old 06-11-2007, 01:57 PM   #5
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whoa, i forgot i posted that picture. i guess the diode is right, it's worked... although i forget where i read which way to orient it.

i used a DSM resistor pack that i got with my injectors... it has a 12v in to 4 resistors which goes to the 12v side of the injectors. the control wires from the ms are directly connected to the injectors.
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Old 06-13-2007, 08:38 PM   #6
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there's my MS layout - i doublechecked the TIP120 and it appears to be wired correctly. Can somoene give it a looksee and see if anything is obvious?
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Old 06-17-2007, 04:15 AM   #7
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So I finally got the water injection and knocksenseMS wired up properly today, and decided to turn over spark control to megasquirt. Coil packs didn't get hot, however, the engine immediately died. I'd get a few ignites during cranking but for the most part, nothing is right.

So I'm laying in bed now with plans to go over my spark settings tomorrow, when suddenly I have to wonder...

Can I have the IAC output from spark control wired up to the IAC, and the IAC PWM wired up to my coil pack?

Is anyone willing to admit this having made this mistake?

First thing I have to check tomorrow...

Also - for anyone with knocksense - Mine seems to be overly sensitive. Following their directions (run at idle, rotate till knock is indicated, rotate 15 degrees away) I get knock showing at 4k rpm and up. Do I need to trim it out any more, or is this somewhat normal and I need to lower the ignore knock threshold in MS? FYI, it's mounted with the flyin'miata mount on the flyin'miata recommended motor mount.
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Old 06-17-2007, 06:10 AM   #8
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Quote:
Originally Posted by bittetech View Post
Also - for anyone with knocksense - Mine seems to be overly sensitive. Following their directions (run at idle, rotate till knock is indicated, rotate 15 degrees away) I get knock showing at 4k rpm and up. Do I need to trim it out any more, or is this somewhat normal and I need to lower the ignore knock threshold in MS? FYI, it's mounted with the flyin'miata mount on the flyin'miata recommended motor mount.
I got the same, I had to crank it way more than 15deg to read properly above 4k... I'd be interested to hear other peoples experiences too!
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