Low Z noise problems

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Low Z noise problems

Postby Keithg » Sun Apr 20, 2008 7:01 pm

There are a number of people running Lo-Z injectors with MS2 chips that have had noise issues. A fix is well summarized on msefi.

http://www.msefi.com/viewtopic.php?f=30 ... &start=120

I do not know how to point to a particular post, but it is on page 7 by jormos90. Nicely detailed fix.

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Re: Low Z noise problems

Postby youask » Sun May 18, 2008 4:18 pm

i got the same problem , lost sync when i ran my injectors as low-Z
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Re: Low Z noise problems

Postby UnaClocker » Fri May 30, 2008 9:31 pm

Sounds like the P&H board solves the problem quite nicely too.
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Re: Low Z noise problems

Postby Keithg » Sat May 31, 2008 6:16 am

UnaClocker wrote:Sounds like the P&H board solves the problem quite nicely too.


very true, but the P&H costs more and you have to add another card as well as order a board and the components. Very nice fix, but maybe not for everyone.

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Re: Low Z noise problems

Postby UnaClocker » Sat May 31, 2008 9:05 am

Heh.. Yeah.. V4 PCB should just include a P&H type setup.. Maybe have a header on the board that you just park a P&H daughterboard down onto, or 2 or 3, depending on how many injectors you need. More of a modular setup..
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Re: Low Z noise problems

Postby SimonKho79 » Sat Jun 07, 2008 6:35 am

Hi,

I am using Low-Z injectors, and has added a resistor to it. The stumbles problem also occurs for me.

Previously I was using High-Z injectors, and this problem never occurred.

However, I have read the solutions in the links provided in this page.

One quick question. Because I am tapping the wires from MS2 to my stock ECU wiring harness. And I notice there are 2 battery supplies line on the stock ECU wiring harness. Is it okay for me to reroute the middle leg of the transistor to the second battery supply? I made a check with my multimeter, however, the 2 battery supply line on the stock ECU wiring harness is connected together.

Just wondering if this will work, so that I no need to pull a long wire all the way out to engine compartment and wiring it to injectors +ve line.

Thanks.

Cheers,
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Re: Low Z noise problems

Postby PhoB » Tue Jun 10, 2008 4:13 pm

Hello,

i have strange noise problems with low-Z injectors. I must made the "pure 12V voltage" trick, until that, i has noise on voltage signal and sometimes RPM drop outs occurs. But i still have huge noise on EGT logging signal - it shows me over 1000celsius on WOT(when i stepping on gas, temperature jumps by over 100cel).
Now iam testing High-Z injectors and its absolutely fine. No noise, sharp EGT line.
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Re: Low Z noise problems

Postby Serj » Mon Jul 28, 2008 3:27 am

Problem as above. i have lost sync problem with LowZ. modified middle leg of Q9 Q12. Solved Lost Sync problem, BUT Batt PW still have huge noize on it. stuck with it. guys where to move ??

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Re: Low Z noise problems

Postby Keithg » Mon Jul 28, 2008 4:26 am

Serj wrote:Problem as above. i have lost sync problem with LowZ. modified middle leg of Q9 Q12. Solved Lost Sync problem, BUT Batt PW still have huge noize on it. stuck with it. guys where to move ??

Serj


Could you post a log or a jpg of a log showing the noise?

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Re: Low Z noise problems

Postby Serj » Mon Jul 28, 2008 4:41 am

Will do that. it looks like bat jumping from 8 to 15 V while engine run + plyaing with thrott

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Re: Low Z noise problems

Postby Serj » Mon Jul 28, 2008 2:01 pm

here is log
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Re: Low Z noise problems

Postby Keithg » Mon Jul 28, 2008 3:53 pm

Serj wrote:here is log


Where is it grounded? (answer: to the head with a big ground wire from megasquirt)
Does the new power supply for the Low Z injectors pull from a different place than the supply for the MS? (answer: Yes, you need 2 - 12V supply lines with Low Z. One switched and the other can be +12 always on, or from pin 87 of the relay that powers the injectors to the 'flyback' transistors.)

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Re: Low Z noise problems

Postby Serj » Wed Jul 30, 2008 12:57 am

KeithG,

Did like you said. Cut +12 from injectors, made separate +12 through relay. this relay supplies +12 to flay back trans and the injectors only. made only 1 +12 line ( but thick )

Still Batt like crazy.
BTW i got 1 farad cond next to accumulator. thought this would help but cant solve noisy batt

Exhausted (
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Re: Low Z noise problems

Postby automat » Sun Aug 10, 2008 5:45 pm

I switched to low impedance injectors because i couldn't find anything bigger that what I had. the noise problems made my LC-1 go nuts, it would jump all over the place, shut down by itself, and i couldn't communicate with it. I only made the +12V mod on the tip125 (actually I have tip127's) and ran the wire to the +12V feed of the injectors, I made no other mods, and I don't have a stereo noise filter, It appears to be ok now.
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Re: Low Z noise problems

Postby el bob » Sat Aug 23, 2008 6:56 pm

I had occasional voltage spikes that would make the engine cut out at unpredictable times. I did the Scosche audio filter mod on my injector FET's and now it's volt age spike problem free.
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Re: Low Z noise problems

Postby Black99rt » Fri Nov 28, 2008 3:24 pm

el bob, can you please write in detail the changes you made incorporating the filter?
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Re: Low Z noise problems

Postby Black99rt » Sat Dec 13, 2008 9:52 pm

I ran the center of the tip125s to inj12v on my relay board today. Datalogs show clean rpm and map signals now. Still have battery spikes to 18V, going to improve grounding, put a cap on my msd and potentially a power filter on the MS.

This fix needs to be severly emphasized in the manual, I went three months dealing with these symptoms and wasted hundreds of dollars on dynotime.
Last edited by Black99rt on Sun Dec 14, 2008 9:30 am, edited 1 time in total.
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Re: Low Z noise problems

Postby Keithg » Sat Dec 13, 2008 10:21 pm

I totally agree that it should be emphasized. I feel that it should be phased out and a new V3.1 board introduced with these fixes.

As for filtering, there is a thread in MS2 talking about this that shows cutting a trace on the board to re-source the 12V reference and add a small cap. I would not recommend going to a huge cap inline as this may not represent the change in voltage that the injectors see.

viewtopic.php?f=91&t=29669&start=80

This is a good thread where it is discussed.

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Re: Low Z noise problems

Postby el bob » Sun Mar 29, 2009 7:10 pm

Black99rt wrote:el bob, can you please write in detail the changes you made incorporating the filter?


Sorry, I havn't been on the boards in a while. Here are two pictures to give an overview. The detailed steps for modification are contained in the link above. It's not really all in one place unfortunately.

http://www.msefi.com/viewtopic.php?f=30 ... 1&start=80
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Re: Low Z noise problems

Postby Keithg » Mon Mar 30, 2009 9:31 am

This is required to get functionality of the PWM on a V3 board. To help it even more, I would suggest pulling the power ground for the injectors off the board as well. To do this, you will need to insulate both TP42s from the rail (nylon screws and mylar insulators), cut the center leg and solder a link from there to the one leg of R37 and R38 (also cut and not connected to board ground - it is easier if the current limiting is not installed). This pulls the injector power ground circuit completely off the board if you also pull the PWM power supply off as well.

I noted a significant improvement in noise before and after when I pulled the ground off the board. I run HiZ injectors. I did not do this complete mod to get the functionality as it is a lot of work, but pulled the drivers off the board to a daughter board when I went to sequential injection. An easier way, IMO, is to create a separate injector driver daughter card and keep the power ground off the board. I have a single 18 ga ground for the MS and a 12ga injector ground with 4 18 ga connections to the injectors.

Oh yeah, I almost forgot. Do *not* forget to pull your PWM idle ground off the board and route it to this same injector ground. It is also a contributor to noise.

You be the judge if this is important or not. Personally, I think this underscores the need for an improved V3 board...

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