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Old 05-13-2009, 11:30 AM   #1
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Default Just got a UEGO, Begi-S AFR tuning?

My intent (once funds become available) is to have Brain build a Megasquirt for the car.

For now, I'm running the BEGI-S with the BEGI FPR at 5 lbs boost, no IC.

I'm using a BIPES to pull off a bunch of timing under boost.

I just installed a UEGO wide band, and I've got a couple of n00b questions:

1. My AFR's cruising at 70 mph tend to run around 13.5-14.00. This sounds like it's on target, right?

2. WOT at full 5psi boost is around 12.1. This also seems OK.

3. Partial throttle without entering into boost can run as rich as 10.1. This seems too rich, but I'm not sure how you would adjust this with the FPR. Any comments or thoughts?

I pulled the plugs and they look black and sooty - not oily, but as if I'm generally running too rich.

Final note, I'm getting a CEL after running for about 20 minutes or so. The codes its throwing indicate the O2 sensor is out of whack. I've swapped O2's but the behavior remains the same.

Thanks for any feedback.
Jim
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Old 05-13-2009, 11:47 AM   #2
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Partial throttle without boost being 10.1 is a bit strange. The FPR should only function when going into boost, so you shouldnt be that rich.

You are getting CEL's because the computer is getting screwy data when it compares throttle position, MAF, and the AFR.

Check engine lights will stop with a proper ECU.
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Old 05-13-2009, 11:50 AM   #3
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Default Can I ignore the CEL until I megasquirt?

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Originally Posted by Saml01 View Post
Partial throttle without boost being 10.1 is a bit strange. The FPR should only function when going into boost, so you shouldnt be that rich.

You are getting CEL's because the computer is getting screwy data when it compares throttle position, MAF, and the AFR.

Check engine lights will stop with a proper ECU.
Or should I be checking something else?
Thanks Sam,

Jim
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Old 05-13-2009, 12:13 PM   #4
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I also think 13.5-14.00 is a tad too rich while cruising at 70mph. I run around 15.3-15.5 during cruise.
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Old 05-13-2009, 01:39 PM   #5
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Originally Posted by jbresee View Post
Final note, I'm getting a CEL after running for about 20 minutes or so. The codes its throwing indicate the O2 sensor is out of whack. I've swapped O2's but the behavior remains the same.
I was getting O2 codes for a while accompanied by a loss in power. I could get it to clear and run properly if I left it in gear and coasted down a few thousand rpm's.

I tightened all of the bolts on the exhaust side and the intake plumbing and it cured it completely. This was of course after I wasted money on a replacement O2 sensor like yourself.
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Old 05-13-2009, 02:38 PM   #6
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Default could it be the downpipe?

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I was getting O2 codes for a while accompanied by a loss in power. I could get it to clear and run properly if I left it in gear and coasted down a few thousand rpm's.

I tightened all of the bolts on the exhaust side and the intake plumbing and it cured it completely. This was of course after I wasted money on a replacement O2 sensor like yourself.
I suspect my down pipe joint is leaking. That dam long bolt is too difficult to tighten.

Thanks for the suggestion. I'll take a crack at it and see if it makes a difference.


Jim
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Old 05-29-2009, 12:14 PM   #7
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I suspect my down pipe joint is leaking. That dam long bolt is too difficult to tighten.

Thanks for the suggestion. I'll take a crack at it and see if it makes a difference.


Jim
Did this fix your issue?
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Old 05-29-2009, 04:04 PM   #8
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Default Nope.

I can't find any leaks, but I still think I'm running a bit rich.

The narrow band O2 is throwing a CEL every now and then, and the Uego reads richer than I need.

I may dial back the begi FPR a bit and see if that changes things.
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Old 05-29-2009, 04:07 PM   #9
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Almost makes you wish you didn't have it so you could be back to driving in ignorant bliss, eh?

I'd dial it back just a little. Shoot for cruise up to the high 14's. it will also help the low RPM. In boost it will go up a bit, but at 5 PSI if you are even in the 12.6-12.7 range you will be fine.
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Old 05-31-2009, 07:56 PM   #10
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I think I will back it down. I think the fact that the plugs are sooty supports that the Uego readings are correct, and I am running a tad rich.
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Old 06-04-2009, 03:32 PM   #11
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Default Well... now I'm confused.

I didn't find any obvious exhaust leaks, so I checked my fuel pressure.

When I remove the vacuum signal line to the BEGI fuel pressure regulator, I see about 52lbs. I backed off the adjuster to 48lbs at atmospheric pressure.

I'm still seeing cruise AFR's on my Uego bouncing between 12.5-13.1.

When I'm on partial throttle, it can get as rich as 10.1.

I pulled the plugs and looked that them, and the are black with soot, so I think I really am running rich.

Possible diagnosis:

1. The fuel pressure gauge is reading wrong, and I'm still pushing too much fuel at the engine.

2. I have a massive leak somewhere.. although, I don't understand why a leak would result in a rich condition. I would have expected the opposite.

I'm open to suggestions. Should I buy another fuel pressure gauge? Should I dial back the pressure further? Go hunting for more leaks in the exhaust?

Thanks for your suggestions.
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Old 06-04-2009, 05:57 PM   #12
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jbresee:
honestly, i think what you are seeing is normal. my afr values would range from 13.5ish to 15.5ish in cruise. in medium load situations (0-10 inch/vac) the oe ecu would dump fuel simlar to yours (approx 10 afr) until i jumped back up over 10 inch/vac. i don't know why it does it........it just does. get an MS.....problem solved.
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Old 06-04-2009, 06:07 PM   #13
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Default Ms is on the wish list.

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jbresee:
honestly, i think what you are seeing is normal. my afr values would range from 13.5ish to 15.5ish in cruise. in medium load situations (0-10 inch/vac) the oe ecu would dump fuel simlar to yours (approx 10 afr) until i jumped back up over 10 inch/vac. i don't know why it does it........it just does. get an MS.....problem solved.
That's sound advice. I want to get a brain-squirter as soon as I can get the cash free.

$50k a year tuition bills are seriously crimping my car budget.
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Old 06-04-2009, 06:57 PM   #14
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Did you get the restrictor thing for the FPR? It is a little plastic thing that you put inside of the vacuum line. Just a thought.
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Old 06-21-2009, 12:09 AM   #15
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you know i just read an old thread about this and he found his stock o2 sensor was bad. The stock ecu wasn't gettin any signal and put itself into safe-mode and dumped lots of fuel. He was runnin 12.1 at cruisin speeds also. May want to look into it. Just disconnect the stock O2 sensor and see what that does for the afr's
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