VSS hookup question and MAP Fluctuations - Miata Turbo Forum - Boost cars, acquire cats.

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Old 04-27-2013, 07:30 PM   #1
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Default VSS hookup question and MAP Fluctuations

This is basically what I just sent to Jeremy @ FM, but I thought I'd post it here (and any responses of his):

Two quick questions:
1. My front harness and dash harness are out of a 93 CA car, so it has the VSS signal going into the ECU at 1M, which doesn't seem to be wired up to the Hydra. I see the VSS+ and VSS- marks on the Hydra harness. Do I need to do a pull-up off the 1M wire to VSS+, and then tag a ground to VSS-, or something like that?
2. I'm getting some pretty nasty MAP noise, which is similar to what I had with the AEM. On the AEM there was a MAP filter setting, but I can't find anything (or any internet mention of one) on the Hydra. Is there anything I'm missing or do I need to find some sort of physical solution (it's been suggested that I use a small lawnmower fuel filter on the vacuum line)?

Longer version:
Spent the week roughing in the fuel map, and got the car dynoed today. 308rwhp, a little down on where I was with the AEM, but I'm also using a much more restrictive intake than I was at that last dyno, so I'm okay with that for now. Time for a smaller SC pulley...

The power numbers were pretty uneven, so we didn't push timing a bunch. I'm guessing it has something to do with the noisy MAP signal, since the logged fuel was jumping around quite a bit:

These are 4 runs, after we nailed fuel down, adding 1 degree of timing per run (after the red run):
http://www.akilla.net/pics/miata/mia...0130427_sm.jpg

The average is pretty consistently going up, but it's hard to repro it to be very scientific with the power fluctuating like this, so we cut the session short until I can figure out what's up with the fluctuations.

Any other ideas for things to check causing this? The MAP signal is going +/- 2psi or so under WOT runs, so it's causing some pretty drastic shifts in fueling. I've locked the timing across the whole range it swings between, and the datalog shows consistent timing, but irregular fueling as a result of the MAP jumps, so I'm just assuming that's the issue right now.
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Old 04-29-2013, 09:10 PM   #2
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I use a line teed from the brake boost hose on the manifold than ran it to the hydra. Some guy keep it really short and go through the hole in the passenger side. Might be the connection? How is yours connected?

I have no idea on number 1..
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Old 04-29-2013, 11:03 PM   #3
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Fully custom intake manifold with a drilled and tapped line for it. It's straight out of the manifold, through the firewall, to the Hydra. I saw the same thing on the AEM, which had a much shorter run (to a GM MAP sensor clipped to the firewall).
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Old 05-01-2013, 03:07 PM   #4
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Can you add a log? (see attachments) rdf or csv with the wot pull?
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Old 05-01-2013, 03:09 PM   #5
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I'll have to take one on the street. I didn't save any datalogs from the dyno day, I was just doing a pull, uploading, checking, adjusting, clearing, repeat. Later this week I'll probably have a chance to drive the car.
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Old 06-15-2013, 01:36 AM   #6
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Finally drove the car for, literally, the first time in 6 weeks. Here's a datalog of driving around, the map I was using while doing it, and a screenshot of a short section of some WOT pulls.

Index of /pics/miata/20130614
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Old 06-16-2013, 04:39 AM   #7
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I noticed some noise with the a/c when it was hot. It was lowered when I added a ground that was otherwise being unused with the hydra GB12. I assume you got the email on the grounding issues. if not snip BC03 and ground elsewhere as they both go to the same chassis ground.
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Old 06-16-2013, 02:12 PM   #8
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Email about grounding issues? Please repost.
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Old 06-16-2013, 06:53 PM   #9
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It was on the missfire issues but i noticed map fluxuations as well.

copied below

...The changes I’ve implemented are highlighted in yellow- feel free to implement them to be on the safe side. Side note, next time you place an order I’d grab a few Hydra ECU terminal pins (07-40010) to have on hand for things such as this, or adding extra inputs / outputs to the system. If you do experience this issue please let me know- upon confirmation we’ll send you a couple pins to cover the mods.

We have also determined that if you are having the issue, simply rolling back to R68 firmware will stop it. This is how we can confirm if an issue is this issue. Therefore I have attached a copy of this revision, please save a copy on your tuning laptop just in case- it could save you some hassle in a pinch. If you have to roll back you’ll do the following:
Use the Hydra Firmware Upgrade Tool in your software package to flash the R68 firmware to your ECU

In your map go to Tuning maps -> idle speed control -> ISC error ignition trim. If you have values in this map you will have to reverse them. Or, if this is confusing, just zero out the whole map (Default is zeroed out.)



One last note, please know that I am currently up to my eyeballs in work. If you aren’t in a hurry you can email me with questions. If you need immediate assistance however it’s best to call. I apologize for any delays, our business is booming right now! The Open House should be great this year too, lots of big HP turbo cars & V8s are coming. J

The yellow highlight pins for your na miata would be GB12 (add pin) BC03 snip and reground elsewhere.
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Old 06-16-2013, 07:46 PM   #10
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Ah. I think I saw that email, or at least part of it. I've been using the ISC error ignition trim, it definitely helps keep my idle vaguely stable.
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