69MyWay

iTrader: (2)

Ran the first dyno on this combination today and found a very lean condition.

See below for the results.

This is a 8.1 Vortec with a Comp HR270 cam, magnum tip rockers, long tube side mount headers with CAI mated to a Richmond six speed manual in a 69 Vette.

While warming up the combo the a/f was 18:1 - By 4,150 RPM it was around 17.

He shut down and talked me out of any more runs until this is resolved.

Fuel pressure comes from a 255 GPH in tank pump - routed through stock injectors. Stock these motors run 340 hp and 455 ft lbs at the crank.

billdk

not entering PE

69MyWay

iTrader: (2)

What is PE? Thanks!

69LT1Bird

iTrader: (1)

Power Enrichment.

Did you tune anything?

GMCtrk

iTrader: (23)

Even if you aren't entering PE (GM does tune in a 60 second PE delay on the HD trucks), you're AFR should still be 14.6:1, not 18:1. I'd check fuel pressure at the rail on the intake.

shoemike

iTrader: (25)

Explain the lean cold start.

Have you changed the tune at all?
It's a possibility that the WBO2 that was used is faulty.
If the WBO2 is legit you need a tune.

kjhallex

iTrader: (1)

Check FP at the rail then check your tune IMO.

JDMC5

iTrader: (3)

i agree

69MyWay

iTrader: (2)

I'll test the fuel pressure at the rail tonight. I figured since it was so lean at cruise and actually got richer during throttle that it wouldn't be a f/p issue.

I didn't tune it, but I'll be working with that. It is a mail order tune.

I'll post up the fp numbers tonight. I'll test that from idle, mid point, and WOT to see what kind of swing I see. It is a fixed regulator with a C5 fuel pressure reg/filter between the 255 pump and the rail.

69MyWay

iTrader: (2)

By the way...I can't independently verify the accuracy of the WBO2, but the owner of the dyno is a high profile place and he assures his equipment is proper. The WBO2 is a remote mount that uses a air feed from the outside as well. He ran the car up and warmed everything getting the dump of moisture build out before we set forward with the test, then has me hook up the air line and open the valve. I don't know how all that works, but on the stand, the WBO2 is mounted in/line to the sample feed that comes from the tube. He usually tunes Fords there and many supercharged/turbo cars. Because of all the boosted cars, he says that he has to make sure that sensor is accurate.

Can't rule it out...but for our discussion that is all I can add about that.

Also...the way the power curve shows a ribbon on (up down flutter) - this appeared to be the PCM taking timing out on knock retard during the run due to the lean condition - Has that been your experience when you see that?

69LT1Bird

iTrader: (1)

Why do you have a fixed regulator and a vette style filter/regulator? That does not make any sense.

Where is the fixed regulator located?

69MyWay

iTrader: (2)

This is a single line fuel rail like the 1999 and up Corvette.

It is running a 1999-2004 Corvette filter regulator.

The last LS build I did we ran it the same way on an LS2 in a 1985 Corvette.

There is no regulator on the fuel rail - it is a feed only.



It is right by the tank with a short return line:



It is being fed by an intank (custom fit) 255 GPH pump:

69LT1Bird

iTrader: (1)

Ok, it sounded like you had two different things going on.

Are you using a MAF?
Are the o2 sensors switching?
Where are the o2's located?

69MyWay

iTrader: (2)

MAF - yes

O2 switch - yes

They are located about 4" downstream on the collector where all the pipes come together at the 12 o'clock position.

These are Hooker side pipes - nowhere else to put the O2,

69LT1Bird

iTrader: (1)

Do you have tuning software? If so, post the tune and a log file.

edcmat-l1

iTrader: (10)

Sounds like a WB issue to me. You can have the best WB available, but if the pump is acting up, or the filters are stopped up, you'll get crazy lean readings.

You should be able to verify with your scan data, and NB O2 sensors. If it's that lean, the NBs should be flat lined near zero.

69MyWay

iTrader: (2)

Going to take it to straightline performance Friday. He had me weld another O2 bung in the header for his wide band.

I don't have tuning software - will learn more through this process.

I would think if it is that lean I'd have a lean trouble code popping up.