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Old 07-27-2008, 12:46 AM   #1
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Default I got boost! and some questions.

First of all let me mention on the first time driving the car I had a civic pull a u-turn to come back and stare at the intercooler

I only ventured very lightly into boost territory as I'm super nervous still. Also I have a clanking rattle sound coming off idle and a decent amount of vibration in the car. Of course my first thought was oh **** I've got knock and I already broke the damn car. Second thought was how the **** is that possible to only hear that coming off idle at 2500rpms Like I said, I'm nervous. This leads me to believe either the downpipe or exhaust is hitting somewhere on the body or subframe. Revved the throttle idling I hear a rattle from inside the car, rev it from the engine bay and I hear nothing, so I'm pretty sure it's the exhaust. I'm also hella rich all over the place so it's unlikely that I got any detonation at the ~4 psi I reached. My idle sucks because I'm using the same VE table as cueball, I'll work on that (thanks btw cueball).

One issue which I do have is with the LC1. I've used the LM programmer to set both outputs to 0-5V 10-20 AFR but the gauge is reading outside that range and so doesn't match what the gauge in megatune says. For some reason the gauge output seems to be stuck with the default setting even though if I open the programmer it says their both at 10-20. WTF? Anyone had this issue? Here's the log of my first time out. Everything look kosher? What's the range of the throttle position in the log? 0-100 or something else?

edit: my boost gauge is also reading about 6 inches of vacuum when the car is not running. I assume this is a bad thing, and that it should be reading zero, right?

P.S. I've got to say a big thanks to the people on this site in general. This is the first car I've ever worked on and two years ago I never would have thought I'd get this far (though I'm still a big noob), and I wouldn't have without the help and info this site and its members offer.

P.P.S No pics or vids because the girlfriends out of town with the camera. Sorry.
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Last edited by johndoe; 07-27-2008 at 01:01 AM.
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Old 07-27-2008, 10:25 AM   #2
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If your boost gauge is zeroed out at -6, then aren't you at 10psi when your gauge reads +4psi?
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Old 07-27-2008, 11:06 AM   #3
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vacuum and boost scales are different so he won't be at 10psi when his faulty gauge shows 4psi. 6in/hg doesn't = -6psi. look at a boost vacuum gauge and you will see the ratio is about 2:1. meaning x degrees of sweep on the vacuum scale is 2x as many units as x degrees of sweep on the boost scale.

convert to kpa and we get

6inHg = about 80kpa
so he is off by about 20kpa
20kpa = about 3psi
so when his gauge says 4psi he is really at about 7psi.
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Old 07-27-2008, 11:10 AM   #4
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Old 07-27-2008, 11:39 AM   #5
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My estimate on how much boost I was making actually came from the MAP reading in the log, I ignored the gauge.
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Old 07-28-2008, 10:48 AM   #6
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got some help over at the innovative forum about my gauge problem and thought I'd leave it here in case another noob has issues. Whatever output you use for the gauge must be set to 0=7.35 5=22.39 AFR. You then set the output to megasquirt to 0=10 5=20 AFR. The gauges will then match in their readings.
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