What say you, Graham?

[XfireZ51]

Here's a thread on the SPLIT BLM issue found in the LT1 if you are interested.
Note this solution works mainly for idle.

http://www.thirdgen.org/techboard/di...ghlight=ULTM8Z

[XfireZ51]

Well we have determined its NOT a case of leaking injectors. Plenum was off so Pete and I took advantage of that fact to verify injectors are good to go. These are Accels with probably 20k+ on them. Cool. More coming later. We'll be swapping out plugs and O2 sensors as part of the upgrade.

[Hib Halverson]

Originally Posted by rkreigh

(snip)

the chevy motors (especially BB chevy) have "good ports and bad ports" that flow pretty differently. (snip)

The Big-Block is the only Chevy engine like that, ie: "good" ports and "bad" ports with a significant difference between the two types.

[XfireZ51]

In the process of doing a bit of upgrading, I think we may have discovered the source of the wide BLM variance. Exhaust leak at the left side collector.
Some times it's a matter of Occam's Razor.

[tpepmeie]

Old thread. Dom, was your bank 2 leaner (ie, cyls 2, 4, 6, 8). I've got lab-grade O2s, and a custom fuel rail and regulator. Aftermarket ECU. Have a bank-to-bank lambda offset of .05-.1 Lambda.

[XfireZ51]

Hi Todd. Good to hear from you. Actually its the left bank(Driver) that is on the lean side. The discrepancy is greater between the two banks at slower engine speeds. At higher rpms, tends to straddle 128 BLM +-2-3 with copious tuning.

Earlier I had a real issue which turned out to be defective secondary injectors.
FIC quickly replaced them gratis. Switched those out along w a new set of coils.

[tpepmeie]

Ok. I agree at lower loads and engine speed the variance is greater. I?m running alpha-n right now. There?s something mechanically causing the variation. Have swapped sensors and same phenomenon. I?ve got the iac passage plugged and idling off the primary blade at the moment.


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[rkreigh]

Hi Todd,


if the injectors are all balanced and ignition / compression good it has to be in the intake not providing good balanced flow. Like you said, something mechanical here. I'd love to tune the car with a haltech or MS pro and see what's going on in each cyl and like Duttweiler says,



"give the engine what it wants and needs"


he does alot of tuning by individual cyl and picks up both efficiency and power

[Paul Workman]

Originally Posted by rkreigh

Hi Todd,


if the injectors are all balanced and ignition / compression good it has to be in the intake not providing good balanced flow. Like you said, something mechanical here. I'd love to tune the car with a haltech or MS pro and see what's going on in each cyl and like Duttweiler says,



"give the engine what it wants and needs"


he does alot of tuning by individual cyl and picks up both efficiency and power

Showing my ignorance here, but I'm intrigued: to tune individual cylinders (I assume) dwell and timing would have to be individually controlled. That would call for some pretty fancy mods to the ECM/DIS, wouldn't it? Please DO TELL. (Always looking for a good article for the HOTB!)

[rkreigh]

hi Paul,


Haltech, Motec, Holley and many others can control spark timing and fuel for each cyl



for my haltech I have EGT 8 channel so you can tune trying to get the egts relatively even regardless of AF which does ok.


more advanced systems now have a WB on each cyl to tune AF ratios to target for each


for the LS engines the #7 runs lean so we feed it more fuel