3800 Back to the 3.4".....

AutoDummy

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Nov 26, 2008
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I put headers on a few weeks ago, and I finally got some time to scan with the 3.25 pulley. I was disappointed to see a max of 5.7 degrees of knock. I was running the 3.25 for a while after my rocker install, but once I got a scanner it became clear that I was doing more harm then good. So the 3.4 went back on. I figured that once I put headers on, I wouldn't have any problem with the 3.25. Yeah I was wrong.

I scanned a run from 25 mph to 110. For what the 02 values are worth, they peaked at .965 (which is up from .925-.940 before headers). Coolant temps were constant at 177.6. IATs were steady at 35 degrees on a 37 degree day. I'm sure this is actual knock, as the numbers increase with speed. First gear I was seeing 0-2 degrees; 2nd gear showed knock up to 3.5 degrees; and third showed up to 5.7. These weren't spikes of KR; the numbers would gradually rise from zero up to the numbers mentioned above. Over the entire run my KR average was 1.67. I put the 3.4 back on last night, but didn't have a chance to scan.

I'm bringing this to you guys hoping you'll have some advice as to how I can improve and tune my car better. I know that you guys will need more info before you can even begin to figure out what is going on in my engine. Just tell me what ya need. Any help with this is GREATLY appreciated!!!!!
 
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imported_Ron Vogel

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About a year ago when Alex put on his headers he was seeing 1.0 volt readings. On clubGP there has been a slough of these lately. Seems like the egr tube is fragile and can develop hairline cracks. The diluted air is messing with the 02's. If you just tested after install, wait a week or two for the computer to learn out the headers. Then go back and retest. I remember that the car is pretty well maintained, but I'd start with the basics first. Look for vac leaks around the TB, EGR, and PCV. If you recently changed the 02 sensor you will need to set a new baseline for that sensor, since the readings change when you replace them.
When it's all square with the KR, I wouldn't think running a 3.0" would be out of the question. I've got less done than you and plan on putting one on soon. When you do your testing, do it from a dead stop. Transitions from cruise to WOT will always spike KR.
 

AutoDummy

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Nov 26, 2008
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I've got ZZPs EGR sim. I've checked the block-off plates for leaks and all seems good. The headers have been on for a month, and the front 02 sensor is about a year old; I've got the 02 sim on the rear. I'll check around the TB and the PCV for leaks. I'll also scan from a stop as soon as I get the chance. I forgot to list my mods in my first post, so here they are:

TOGs, 1.9 RAs, MandS 3" d/p w/ cat into Borla, DHP, CAI, 3.4-3.0, RV TB, ZZP EGR sim

I've been thinking about picking up a Mini-AFC; but it seems more like a band-aid...I'd like to figure out what exactly is causing the problem. Worst part is: I'm short on knowledge when it comes to the tech side of engines. I just haven't been exposed to it so I haven't had the chance to learn.....besides trial and error. LOL.
 
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imported_Ron Vogel

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The mini-afc is a great little unit. It doesn't really bandaid, it's actually pretty useful. I can run a street setting and a track setting. Since I ported your TB there are a few new things I've learned about recurving the mechanical signal on the MAF. I'd be more than happy to drop in the insert and ramp for free. It'll only help, it pulls the maf up a bit and you get more flow too. BTW, I haven't really announced it yet but beta's for the fully CNC ported tb's with the bigger bore will be hitting the streets in a couple of weeks!
 

AutoDummy

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Nov 26, 2008
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What's the deal with the new TB? Instead of you putting the ramp in mine, maybe I'll just upgrade. Will you just be CNCing the core TB? What is the target price for these? I'm very interested...

I'll pick up the mini-afc and do some tuning; hopefully I'll be able to quench some of this damn KR. Hey thanks for your time Ron. Let me know about the TB.
 
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imported_Ron Vogel

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Pricing is a little up in the air. I'm shooting for a target of $200 on a '99+. One of the reasons is that the first run is basically gonna kill me on set-up costs, and at this point about 5 people involved in the process of getting it out the door. As long as the front end is done, the bore and new plate shouldn't be any big deal, but I have to get the beta's out of the way before I start boring out the first ones. It'll most probably be under $100 for an upgrade. Wait till you see my new house's garage, way better set-up and lot's more room. That place in Naperville was a freakin' dungeon.
 
What are your LTFT's looking like, I was getting crazy KR 6+ on my 3.2 before my IC install and I am rather heavily mod'd. I had never paid much attention to LTFT's, but as mine were -16% I was running silly stupid rich. Maybe you are too, worth checking. I thought it rather funny running rich caused KR, but it DEFINITLY did. leaned it out and all was perfect pulled much harder too.

Just a thought hope it helps
 

AutoDummy

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Nov 26, 2008
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When were you seeing -16%? WOT? I haven't checked my LTs at WOT since headers and the EGR sim. At idle I see a max of 11.7%; which is down from the 13-14% I was seeing before the mentioned mods. I bought a Mini-Afc to do some testing, but haven't had time to use it. I'll post once I have some results. Thanks for the suggestion!
 
When were you seeing -16%? WOT? I haven't checked my LTs at WOT since headers and the EGR sim. At idle I see a max of 11.7%; which is down from the 13-14% I was seeing before the mentioned mods. I bought a Mini-Afc to do some testing, but haven't had time to use it. I'll post once I have some results. Thanks for the suggestion!

YES WOT, but I don't think they vary between idle and WOT as much as other parameters, but if you are still +11-12% you are running way lean. LTFT should be as close to zero as possible. You DEFINITLY need to get that mini AFC on and do some tuning. I was rich because I was running at 100% on my AFC and I have the LS1 TB and LS6 Maf. with all my mods in 70* weather I am almost perfectly tuned with my AFC set at 94% so you can see 100 would be silly stupid rich

I would start with 103% and go from their if your running that lean
 

rob

TCG Elite Member
Dec 28, 2008
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-16% wow......Good info hear Jeff......You'd traditionally wouldnt think the richness would add to the KR but the unexpended fuel is detonating under pressure.....You concluded that it was a mod related problem.....You fixed it with the mini-a/f...might not be a bad idea to try a wide ban...to double check....Just a suggestion. :) Are you using a a-tap Jeff?????
 
You concluded that it was a mod related problem.....You fixed it with the mini-a/f...might not be a bad idea to try a wide ban...to double check....Just a suggestion.  Are you using a a-tap Jeff?????
Yes, it finally came to me I was ignoring the fact I was running a MAF designed for a V8 and that running it at 100% might be a tad EXCESSIVE. Yes I use A-Tap I couldn't begin to tune this car with all the mods I have without it.

I have thought of getting a Wide band 02 sensor to monitor but don't have the money right now.
 

rob

TCG Elite Member
Dec 28, 2008
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Good deal-glad you got it tuned-AT is a nice economical non-bio solution comletely nessessary to mod these cars-its not like changing jets and metering rods anymore....The wide band is a good idea...PCM tells you what it computes(gross) to obtain 14.7:1 but this may not accually be(net) the out of pipe a/f ratio. Miker's PCM told his his a/f was normal and when he ran an WB02 he found it to be 16:1.

What type of devises are you looking at.....how much...? Have a link?

I may get some crap for sating this but what you said about the LARGE V8 TB's is why I dont have one......Sure your getting more air in the engine....But if you have to detune you Hz's because the MAF's are off the PCM's tables you engine isnt utillizing the increased airflow. Can the PCM's MAF tables be expanded to better suit the V8 TB's.

What is he max potential Hz produced by the V8 TB and what is the highest on the PCM's tables..? If your tuning a little you may the gains(tad) but too much will put you towards a higher stock range. This is pretty much a theory to me.
Im not discrediting the larger TB's or anyones mod-can You help me with this delema? :)
 
Yes I have the LS6 MAF on mine. and it definitly isn't running lean at 100% Yes you can get Charles to put LS6 MAF tables in to properly use the MAF, but either way the car is using the added air flow. It may not measure it right, and you may have to spoof it with the AFC, but you cant stop it from using the air that comes in...does that make sense???
 

AutoDummy

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Nov 26, 2008
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I did some scanning yesterday. Without the AFC my LTs at idle ranged from 3.47 thru 11.xx, and held steady during WOT at 10.94%. I installed the AFC and set it to 103% as Jeff suggested. Idle was -0.78 thru -3.68. Anything over 30% throttle would bring me back to positive numbers. I was surprised to see that the LTs during WOT were still holding at 10.94%. Can anyone explain this? KR is down significantly; nothing over 1 degree until I started to let off the throttle around 100 mph; where I got a spike of 3.47 degrees. My 02s maxed out at 1010mv during WOT.
 
Long Term Fuel Trim (both banks) - remember a few weeks ago when I said the O2 sensors provide the feedback for the computer to fine-tune the air/fuel mixture? This reading tells you exactly what "correction factor" is being applied. If this hits +/- 25% a code will be set. In my experience, it's usually less than 10% If you see numbers over 10% I'd be suspicious that something is out of whack, or on its way out. Note - don't worry so much about this number at idle, check it during normal driving conditions.

I took this from Mike farion's Auto-tap weekly email Hope it helps with the LTFT issue
 

AutoDummy

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Nov 26, 2008
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Excuse my ignorance, but what can I do to fine tune and get the 02s down?

I'm a bit confused at my LTs being the exact same at WOT before and after the AFC. I'm going to set the AFC at 104 and scan again. If my LTs remain at 10.94% during WOT, but my KR is gone, should I be ok? If LTs are supposed to be as close to 0 as possible during WOT, but I can't get them down from 10.94% with the AFC, is there anything I can do?

Thanks!
 
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