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Discussion Starter #1
Hi everyone,

For reference I have a 2000 Regal GS, stock everything except for:

- 3" Downpipe without cat
- ZZP Stage 1 Throttle Body
- High Flow fuel filter
- Overkill PCM

Let's back up. Completely stock, I scanned for knock with an aeroforce gauge. at WOT I get about 8.6 degrees of KR.

Then, last week, I had the 3" Downpipe installed along with a high flow fuel filter and drove it home. On the drive home, knock was again at 8.6 at WOT.

I drove it home, installed the ZZP stage 1 TB and overkill PCM. I ordered the PCM with the following mods listed:
3" downpipe without cat, Stage 1 TB, and CAI. So the PCM was made with the stage 1 TB accounted for.

So after installing the PCM and TB, I drove it again and no change at all in knock. Next week the CAI goes in, but I'm guessing it won't make that HUGE of a difference.


Anyone have any suggestions as to what I should check next?

I have stock iridium plugs so I'm going to go with copper plugs a heat range colder (going with AutoLite 605s). Had the wires changed only 10,000 miles ago so that's not the issue.

Also going to get my hands on a fuel pressure gauge and check what PSI I'm running, but I'm not sure what numbers are normal for this car. What # should I be hoping for?

Anything else I should check?
 

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Either go up and pulley size or have your tuner pull timing in his tune. Be sure to let him know what kind of upstream o2 sensor voltage you are seeing under WOT. Needs to be over 900 mv's
 

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Discussion Starter #3
Either go up and pulley size or have your tuner pull timing in his tune. Be sure to let him know what kind of upstream o2 sensor voltage you are seeing under WOT. Needs to be over 900 mv's
Pulley is 3.8" (stock). I can go bigger than that?

And voltage in my front o2 is 850-950 mV when I'm at WOT.

He (the tuner) is actually is in the middle of moving and hasn't really replied to any of my questions in a while. Do you have an email that I can contact you at to get a custom tune?

Thanks for the quick reply btw.
 

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[email protected]


While Scanning KR I want you to scan timing as well.

Actual timing + Knock Retard = The commanded Timing in the PCM.

When are you seeing 850 mv's? In the higher rpm range? That is an indication that the car is loosing fuel pressure and leaning out as injector duty cycle increases.

I had three different 100,000 mile 3800's coming in for dyno work in June and all three of them ran out of fuel because of running a original fuel pump.

A 255 intake fuel pump should be the first modification to any higher mileage car that is going to be modified. Fuel pumps do not last forever.
 

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Discussion Starter #5 (Edited)
[email protected]


While Scanning KR I want you to scan commanded timing as well.

Actual timing + Knock Retard = The commanded Timing in the PCM.

When are you seeing 850 mv's? In the higher rpm range? That is an indication that the car is loosing fuel pressure and leaning out as injector duty cycle increases.

I had three different 100,000 mile 3800's coming in for dyno work in June and all three of them ran out of fuel because of running a original fuel pump.

A 255 intake fuel pump should be the first modification to any higher mileage car that is going to be modified. Fuel pumps do not last forever.
I'm going to go out right now and give you those numbers.

I'm at 76000 miles, running stock pump and haven't done a fuel pump rewire.

EDIT: And I'll check what my mV is at the higher RPM range just to make sure I'm telling you the right values.
 

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If the tuner loaded the correct MAF transfer function in for the ported tb housing you should never drop below 900 mv's under WOT. Either you are losing fuel pressure or your tune is not correct for the ported TB housing.

Commanded A/F would also be a good one to log as well. As long as the commanded is below 12.0:1 I would expect to see the 02 voltage above 920. A narrow band voltage of 850 is going to put you at an A/F above 13.0. Piston Popping Lean.
 

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Discussion Starter #7
If the tuner loaded the correct MAF transfer function in for the ported tb housing you should never drop below 900 mv's under WOT. Either you are losing fuel pressure or your tune is not correct for the ported TB housing.

Commanded A/F would also be a good one to log as well. As long as the commanded is below 12.0:1 I would expect to see the 02 voltage above 920. A narrow band voltage of 850 is going to put you at an A/F above 13.0. Piston Popping Lean.
Alright, here are some freeze frame values I recorded on my aeroforce.

When knock was at 8.6, ignition adv was at 7.0.
mV of the o2 never went past 850. Stayed around 800 most of the WOT run.
At one point it was at 805, CMD a/F was 10.9. O2 went down to 760 during the run, cmd a/f stayed at 10.9.

Right before a shift point, knock was at 8.6, ignition adv was at 6.5.

Sorry for the horrible formatting, I'm on my phone at the grocery store.

What do these numbers tell you? Could i have a lazy o2?
 

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In summary.

Car is knocking because it is VERY LEAN.

Last thing would be a freeze frame of MAF Freq vs MAF air flow in lbs/min.

This will give us an indication if the tune has the correct MAF Transfer Function.


These maf voltages are not even safe for a NA car. You now know what the commanded timing is in the car by adding the timing in the car plus the amount of knock.

8.6 degrees of Knock + 6.5 degrees of Advance = 15 degrees of desired timing which is plenty safe for your car providing the A/F is in check.

I would almost be willing to bet a $1,000.00 you are losing fuel pressure.

Then again your tune could be all wrong for the maf.
 

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Off to the Grocery Store. Will be back in about an hour to read up on your replies.
 

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Discussion Starter #10
Alright:

Starting out early RPM at WOT:

MAF lb/m: 11.73
MAF freq: 7196

Progressing further:

13.02
7383

Then

14.59
7667

Highest it got to was

21.61
8601

This was a short run at WOT from first to second gear. Wasn't able to go from 2nd to 3rd where I was this time.

Looking forward to hearing your reply once you're back.
 

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Survey Says.


MAF Transfer function is stock.

Your "Tooner" did not modify it for the ported throttle body.

So this is at least part of the problem.



This is based on looking at a stock tune file OS - 12223463 - 2002 Regal GS
 

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Discussion Starter #12
Survey Says.


MAF Transfer function is stock.

Your "Tooner" did not modify it for the ported throttle body.

So this is at least part of the problem.



This is based on looking at a stock tune file OS - 12223463 - 2002 Regal GS
:pissed:

Well that's awesome. Looks like I'll get a fuel pump and do the re-wire for thicker gauge wiring.

Can I email you to talk about sending you my PCM and paying you to get this sorted out?

My "tooner" hasn't replied in over 2 weeks to any of my emails so I'm kinda giving up on him.
 

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Discussion Starter #13 (Edited)
Just got to spend an hour with a fuel pressure gauge plugged in.

Fuel Pressure stayed at 60 PSI at WOT, up a hill, at 60-80 mph. Huh.

Also, got my hands on 94 octane, didn't know Chevron's where I lived carry it.

Knock was at 0 - 1.9 in first to second gear.

From 2nd to 3rd gear, KR jumped erratically up to 5.6*. Went up, down, up down, then peaked at 7 as I made the shift into 3rd.
 
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