Front bank running lean on my 3.0 GTV. - Alfa Romeo Forum
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(Post Link) post #1 of 11 Old 17-07-12 Thread Starter
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Front bank running lean on my 3.0 GTV.

Any suggestions welcome.
And no itís not running lean when she boosts itís at idle and small throttle input. She will typically run lean on the bank when I am standing in traffic which is perfect for consumption but alarming for the rest.
Its a CF2 with oe management until the boost reach 0.1bar where 4 additional injectors can ad up to 1800cc additional fuel if needed.
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What inlet manifold & throttlebody are you using? All standard?
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Yes everything is oe apart from the 3.2 injectors instead of the old 3.0 injectors. But the injectors should influence both banks and not only the one.
I did change the Lambdas but no difference.
I even upped the fuel pressure to 4bar no difference.
It just keep leaning out number 4 5 &6.
I actually think the front bank looked lean compared to the rear when i removed the 3.2 as well.

List of changes from oe 3.0 cf2
1. 2.5 crank lowering the pistons in the sleeves resulting in 7.8 cr. I had to do this my 3.0 crank was damaged.
2. 3.2 injectors they are marginally smaller than the 3.0 units but they respond a lot bettor to pressure increases.
3. FPR on the rail with an additional pump pressure set at 0.4bar static. Not using the raising rate part since it’s not needed.
4. Standard plenum, runners, throttle and MAF (in front of turbo).
5. Standard outlet branches (lambdas on branch) with new collector to connect to turbo.
6. 76mm exhaust from turbo to back
7. Turbo and intercooler.
8. 4 x 450cc injectors mounted on boost pipe activated by independent management system (map, temp, rpm)

That’s it.

GTV V6 Turbo, Q2, Eibach, Koni, and lots more
916 2.0 Spider what have I done
Triumph Trophy 1200 to counter the fuel prices.
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Drive by wire or cable?
Older versions have separate fuel pressure regulators on both fuel rails
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Did you check you timing? Running lean on low rpm could be a inlet cam opening to early
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(Post Link) post #6 of 11 Old 17-07-12 Thread Starter
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Drive by wire

I connected the rear of the fuel rails in a attempt to stabilize fuel pressure between the two banks. The FPR sits behind the rails so pressure should be equal.
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Cam timing is spot on.
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Some thoughts:

Maybe it has adapted fueling for that bank because it saw it Rich a lot ...
Can you reset Adaption ? Fiat ECU-Scan or Alfadiag will do.

A Strange tought: It is quite common to go for a lean idle with Euro3-4-5 Cars,
maybe this was done intentionally on the front Bank only because it has a lot less thermal issues than the rear one
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(Post Link) post #9 of 11 Old 18-07-12 Thread Starter
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That's a interesting thought.
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Quote:
Originally Posted by turbonutters View Post
That's a interesting thought.
How do you actually know your front bank is lean ?
Did you plug a Wideband into both banks ?

Lean = Hot, Lambda 1.0 is reasonably cool, rich is even cooler, but i guess you surely know that...
Also most engines won't have a problem running lean if there is no load/slight load.
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I did not plug the wide band into each bank but the front branch is alarmingly light in color while the rear branch is sooty. The plugs confirmed this as well.
The wide band indicate that the motor leans out at idle and small throttle input.
The strangest part is that even if we unplug the lambdas and maf the ecu still leans the mixture out
Maybe I have a stubborn ecu adaptive learning that does not want to reset.
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