merc3065

I've got a few small issues with regards to tuning.

Im a little confused on how the computer works with fuel.

I've done tons of datalogging but never really understood the meaning of all the numbers.

I know what INT and BLM are, O2 cross counts, spark counts, base pulse width etc.

My biggest question is BLMs.

128 BLM is supposed to be the happy medium.
108 is the bottom of a 32B
165 is the top of a 32B

When tuning, I want to lean the car out some, do I need to adjust so that the O2 is reading lean? ie 130-135 or go rich to 120-126?
My last test I ran, I had set the BPW vs Load (32B chip) so that the BLM was around 135 for the test RPMs/load. It still smelled rich. Did I adjust the wrong way?

I am having troubles passing the local smog test and needed some ideas on how to tune. The sucker is dumping fuel like nobody's business.

I want to pass without an issue even on a roadside as I'm not overly concerned with performance as the car has more than enough.

Engine is a 350 L98 with aluminum heads, bigger runners, ported plenum, slightly larger than stock cam, 1.6 rrs, 24# injectors, cold air kit, airfoil etc.

pandin

What you are experiencing is a false O2 reading, due to extra oxygen being in the exhaust stream, it could be with or without extra unburnt fuel.

The ECM, when it see's the extra oxygen, adds more fuel. So if you were rich, you are really rich (smog should be reading high HC).

Do you have a heated O2 installed? This is important if headers are used.

merc3065

I've just got the bosch single wire O2 on my SLP headers.
It's currently hooked up to my inline AFR meter.

It enters closed loop pretty quick. And yes, the E-test is super high HCs. I corrected a NOx problem due to timing and the ARAP code's aggressive spark curve. Really messed with the NOx readings.

The system does not have the AIR pipes hooked up or the pump on it either. The cat is a non AIR one as well. I have the AIR system disabled in the code also and corrected the O2 table to compensate for it as well.

Could the extra O2 be from an exhaust leak at the heads?

I've had a problem in the past with the used SLP headers I have not mating properly to the heads even with thicker gaskets. I thought I had fixed it... Think they might be warped? Not sure. But could this be leading to a false O2 reading?

pandin

Yes it could, but what are your cam specs?

merc3065

Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 0.0 BTDC 34.0 ABDC 107 214 °
Exhaust 47.0 BBDC (7.0) BTDC 117 220 °

Lift: Intake @Cam 301 @Valve 452 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 310 @Valve 465
Rocker Arm Ratio 1.50

Its just a little one with a bit of improvement compared to stock.
As far as I can tell from the numbers I ran its about 7* overlap, which leads me to believe I shouldn't have to worry too much about it throwing the O2 off by sucking some fresh air out the exhaust. The bigger overlaps I know you need to muck with the O2 tables to get the right numbers.

Unless im off on my numbers, or that 7* should have some massaging of the O2 tables?

pandin

Depending on the ramps. That 7* is at .050 lift? What is the advertised duration and at what lift?


Timing At 0.006
Intake Valve Open 23 Close 55

Exhaust Valve Open 66 Close 18

Valve overlap 41

Intake CL 106 LSA 110

Duration @ .006 Intake 258 Exhaust 264
Duration @ .050 Intake 206 Exhaust 212

The O2 doesn't like this cam.

merc3065

Not 100% sure how to figure that out from reading the card listed on their website. I don't have the cam card anymore, or if I do, its buried in amongst 800 lbs of other stuff in the garage.

It's a crane cam powermax 2032

http://www.cranecams.com/?show=brows...tType=camshaft



Part Number: 104224 Grind Number: POWERMAX 2032 (FORMERLY COM
Engine Identification:
Start Yr. End Yr. Make Cyl Description
1987 1989 CHEVROLET 8 FOR 87-89 CORVETTES, CAMAROS AND FIREBIRDS FACTORY EQUIPPED W/350 TPI ENGINES. ADJ. FUEL PRESSURE REGULATOR (99470-1) IS RECOMMENDED FOR MAXIMUM PERFORMANCE. (50 STATE LEGAL FOR LISTED APPLICATIONS, C.A.R.B. E.O. D-225-22). BASIC RPM 2000-5500
Engine Size Configuration
305 C.I. V
Valve Setting: Intake .000 Exhaust .000 HOT
Lift: Intake @Cam 301 @Valve 452 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 310 @Valve 465
Rocker Arm Ratio 1.50
Cam Timing: -- @---
Lift: Opens Closes ADV Duration
Intake --- --- 270 °
Exhaust --- --- 276 °
Spring Requirements: Triple Dual Outer Inner
Part Number 96802
Loads Closed 107 LBS @ 1.800 or 1 13/16
Open 276 LBS @ 1.360

Recommended RPM range with matching components
Minimum RPM 1800
Maximum RPM 5800
Valve Float 6400
Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 0.0 BTDC 34.0 ABDC 107 214 °
Exhaust 47.0 BBDC (7.0) BTDC 117 220 °

If you can make sense of the numbers listed here, that would be appreciated

pandin

That cam "Its just a little one with a bit of improvement compared to stock." is a bit of an under statement.

At advertised 270-276 and the 1800-5800 rpm range, it is well into the revision range at any idle below 1000.

The cam I listed is a 1000-5000 rpm ranged cam and it is way rich (black plugs), O2 reading lean at a 750 rpm idle.

You are 800 rpm higher on the scale, so......It is my opinion that this cam is better suited for a stick shift or high stall TC (needs to idle at a higher speed).

My stall is 2000 rpm measured during data log, Motor spins to 2000 before tires move, at wot launch. Peak torque is at 3000 rpm.

To get past emissions and still be drivable, will take some serious under standing of ECM tuning.

It has been done by people on this board, but is beyond my level of understanding.

merc3065

Still helps Pandin

Thanks

Ive got a 2400-2600 stall converter on the tranny right now.

I didnt think the 2032 was that much of an improvement over stock really.
I'll start a new thread asking a little more about the cam and how to properly compensate for it.

Cheers