FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: jgkurz on October 15, 2017, 11:44:36 AM
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Hi folks, I have been doing some AFR testing on my stroker side-oiler with a Ford 2x4 MR intake and QuickFuel 4160 carbs. The jets are identical on all corners. The engine runs very well, but at WOT bank 1-4 is always 1pt leaner than bank 5-8. I have had three different headers on the engine without a significant AFR change so I don't think headers are the cause. I believe the Ford 2x4 is to blame. I am not aware of any common plenum in the 2x4 intake stream. All venturi's seem to be independent to each cylinder.
Do you agree that my 2x4 MR intake is likely to blame? I would like to equalize AFR's across all cylinders. To do this I could jet down the mains on the venturi's that serve bank 5-8.
I know I am chasing a small change but I see no harm in trying to make the engine more efficient.
Thoughts?
Thank you,
John
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Is this a tunnel wedge or dual plane ?
Have you switched oxygen sensors side to side to make sure it’s not equipment error ?
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The intake is the Ford 2x4 MR Dual Plane. Here's a pic before I installed on the engine.
(https://farm5.staticflickr.com/4469/23861566228_365b7d5bcb_n.jpg)
I have confirmed the results on both a SuperFlow engine dyno and a DynoJet chassis dyno. The results were unchanged even when sensors were swapped.
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Pretty much normal. Open spacers will often smooth them out a bit side to side...
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Pretty much normal. Open spacers will often smooth them out a bit side to side...
Thanks Barry. I don't have room to add an open spacer under the carbs, The Mach1 hood provides for very little clearance. Do you think a jet change on the venturi's that feed 5-8 would even out AFR's?
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I believe the Ford 2x4 is to blame. I am not aware of any common plenum in the 2x4 intake stream. All venturi's seem to be independent to each cylinder.
It's a dual plane intake.... doesn't work in the 1-4 5-8 dynamic, nor does each venturi feed one cylinder, two venturi per carb feed one plane.
I'd suspect it is an exhaust issue, or a sensor issue.
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Switch sensors and test again. Joe-JDC
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Switch sensors and test again. Joe-JDC
I have switched sensors four times on two different dynos. The results match every time.
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I believe the Ford 2x4 is to blame. I am not aware of any common plenum in the 2x4 intake stream. All venturi's seem to be independent to each cylinder.
It's a dual plane intake.... doesn't work in the 1-4 5-8 dynamic, nor does each venturi feed one cylinder, two venturi per carb feed one plane.
I'd suspect it is an exhaust issue, or a sensor issue.
Thanks Drew. I wasn't sure how the dual plane ports work. I wish I would have figured out the port-to-plane-to-venturi correlation before I installed the intake.
How could it be a sensor or exhaust issue if the readings stay consistent across different headers and sensors? I respect the opinions on this forum given I am new to FE's but I can't understand how the sensors or exhaust could still be a factor.
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We respect you too.... but understand this has been an issue for you for some time, whereas I just heard about it an hour ago, so I, like many others here are simply throwing out ideas, and ruling things out. No offense meant to you.
Well in a dual plane intake like the 2x4, one plane is what, cylinders 1, 4, 6, 7 and one plane is 2, 3, 5, 8, right?
If your issue followed that I would look into a carburetor issue, staggering jetting, making certain no trash is in a bleed or restriction, etc. Or a manifold distribution issue.
So my logic points to things that are specific to one head or bank only. That is why I'd not waste much time on the carb, but would focus more on the sensor (which it appears you have) or the exhaust (which it appears you have).
Now, O2 sensors are funky things. Are they both grounded in the same place? (it matters)
Do the heads have an exhaust crossover that could skew readings?
Are the headers on both banks perfectly sealed?
Are the welds perfect for the o2 bungs?
Was silicone used for the header gasket? if so, is it safe for sensors? (not all are)
How do the plugs look? One cylinder misfiring or one weak plug or wire can toss the readings for the whole bank.
next line of thought.....
If it runs well and none of the cylinders are dangerously lean, well..... rock and roll :P Stop looking at the gauges, heh. I know, not totally helpful, but the nature of the beast sometimes.
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Not unusual to see a dual plane intake cause different A/F numbers from side to side. The Sidewinder intake is really bad in that respect...
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Drew and Jay, Thank you for taking the time to respond. I will check the items suggested but I suspect it's just the way the intake flows.
-John