Air fuel ratio question

Bobby Fazio · 07-10-2017, 09:04 AM

Addicted to finding that perfect tune..I picked up a 4 channel wideband and put them in the right bank and also put a 5th sensor in that collector. The header sensors are all located 10 inches downstream. Made a run and The collector sensor reads 1 unit leaner than the header sensors. Just wondering if that's normal, is that fuel still burning on its way down the header? I wouldn't think fresh air is making its way in the collector at WOT.

Ed Wright · 07-10-2017, 09:35 AM

Bobby, you would expect all widebands systems would report the same air/fuel ratio in the same engine, same run. Would certainly be nice. But, they do not. All we can do is find what numbers, with what we have, that makes our car fastest. Even different sensors often give a little different data, same car, same location. I buy an extra sensor for mine before it is needed.

west coast · 07-10-2017, 10:47 AM

Hey Bobby i just use the # as reference and move your target richer or leaner and go off the time slip at what it likes. I tell people how lean i run my car and cant believe i don't have holes in the pistons. ever sensor is different.

Signman · 07-10-2017, 01:50 PM

Bobby
Would think that either and both can be happening.
If your rich fuel can be burning in the primary tube making the O2 see lean. Even at wide open throttle fresh air can get sucked in the collector.
Another variable in addition to the difference in each O2 sensor you're using a 4 channel WB assume it is a stand alone device, the 5th is being monitored by a separate device WB or EFI can also add to the variable.

randy wilson · 07-12-2017, 09:39 AM

Quote:

Originally Posted by west coast

Hey Bobby i just use the # as reference and move your target richer or leaner and go off the time slip at what it likes. I tell people how lean i run my car and cant believe i don't have holes in the pistons. ever sensor is different.

I agree with your theory. However lately, like the last 12 years, all 3 engines we ran locally are 3 size jets larger then when just off the dyno. Plugs look almost black, but cars are quicker. One size bigger, we slow down, one size smaller, we slow down. Looks way rich, but quicker by enough to warrant the change.

Ben Holt · 07-12-2017, 11:23 AM

To answer the OP's question, yes, that is correct. I have found that the farther away from the exhaust port the leaner the number reads. I have seen it to be somewhere between .6 to 1.0 on the AFR ratio. The 02 closer to the port is what I believe to be a more accurate number of what the engine is running, but the collector is a good number to have a reference to make sure the two banks are running fairly balanced to each other

Ed Wright · 07-12-2017, 12:28 PM

"Closer to the port", in a primary tube you are only seeing that one cylinder. If you have not tested with 8 widebands, you might be surprised at different the others could be.

Ben Holt · 07-12-2017, 07:00 PM

Yea, I have tuned quite a few engines with 8 o2's, and it is quite the eye opener to see what each individual hole does. But once you get them fairly balanced, then see those collector numbers come into balance as well, it's amazing how well the engine runs, especially up top

Ed Wright · 07-12-2017, 10:16 PM

If you use a FAST XFI system, you can use a distributor with a cam position sensor & put it in Sequential mode, and adjust each cylinder's air/fuel & timing. There is some power there. Could be suprising the difference in air/fuel ratio you see between cylinders. Change intake manifolds, you get to do it all over again. With my Hogan, I had less variation than with the single plane & elbow. More difference between the 2 tune ups than just that.
And, I saw VERY little difference between my air/fuel ratio in the primary tube O2s, and in the collectors. I must be doing something wrong. LOL

Ben Holt · 07-13-2017, 10:03 AM

I didn't say that......I just said I have seen somewhere between .6 an 1.0 difference between the port and collector o2. Every combo is different. The OP just asked if the variation between the two is common. My answer is yes, it is common. But from what I've seen, once you get all 4 holes in the bank balanced out nice, the collector number starts to come around, as well, like you have found

The sequential EFI stuff is really neat to fine tune the individual holes. I have really enjoyed messing with that, sounds like you have, too!

07-10-2017, 09:04 AM	#1
Bobby Fazio VIP Member Join Date: Nov 2009 Location: Egg Harbor Township, NJ Posts: 1,467 Likes: 1,444 Liked 4,365 Times in 501 Posts	Air fuel ratio question Addicted to finding that perfect tune..I picked up a 4 channel wideband and put them in the right bank and also put a 5th sensor in that collector. The header sensors are all located 10 inches downstream. Made a run and The collector sensor reads 1 unit leaner than the header sensors. Just wondering if that's normal, is that fuel still burning on its way down the header? I wouldn't think fresh air is making its way in the collector at WOT. __________________ '65 Mustang SS/L & L/SA DriverInterviews.com \| App.DragInsights.com

07-10-2017, 09:35 AM	#2
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: Air fuel ratio question Bobby, you would expect all widebands systems would report the same air/fuel ratio in the same engine, same run. Would certainly be nice. But, they do not. All we can do is find what numbers, with what we have, that makes our car fastest. Even different sensors often give a little different data, same car, same location. I buy an extra sensor for mine before it is needed. __________________ Ed Wright 4156 SS/JA

07-10-2017, 10:47 AM	#3
west coast Senior Member Join Date: Dec 2008 Location: Rainy Washington Posts: 609 Likes: 12 Liked 222 Times in 72 Posts	Re: Air fuel ratio question Hey Bobby i just use the # as reference and move your target richer or leaner and go off the time slip at what it likes. I tell people how lean i run my car and cant believe i don't have holes in the pistons. ever sensor is different. __________________ James Boyce 6052 K/SA Stock National record holder 2015,2018,2 times in 2022,2023

07-10-2017, 01:50 PM	#4
Signman Senior Member Join Date: Oct 2003 Location: Lower Slower Delaware Posts: 535 Likes: 22 Liked 269 Times in 99 Posts	Re: Air fuel ratio question Bobby Would think that either and both can be happening. If your rich fuel can be burning in the primary tube making the O2 see lean. Even at wide open throttle fresh air can get sucked in the collector. Another variable in addition to the difference in each O2 sensor you're using a 4 channel WB assume it is a stand alone device, the 5th is being monitored by a separate device WB or EFI can also add to the variable. __________________ Frank Ferrucci I/SA 1271 "Be Thankful for the Gifts You are Given"

07-12-2017, 11:23 AM	#6
Ben Holt Member Join Date: Sep 2008 Posts: 142 Likes: 3 Liked 112 Times in 40 Posts	Re: Air fuel ratio question To answer the OP's question, yes, that is correct. I have found that the farther away from the exhaust port the leaner the number reads. I have seen it to be somewhere between .6 to 1.0 on the AFR ratio. The 02 closer to the port is what I believe to be a more accurate number of what the engine is running, but the collector is a good number to have a reference to make sure the two banks are running fairly balanced to each other

07-12-2017, 12:28 PM	#7
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: Air fuel ratio question "Closer to the port", in a primary tube you are only seeing that one cylinder. If you have not tested with 8 widebands, you might be surprised at different the others could be. __________________ Ed Wright 4156 SS/JA

07-12-2017, 07:00 PM	#8
Ben Holt Member Join Date: Sep 2008 Posts: 142 Likes: 3 Liked 112 Times in 40 Posts	Re: Air fuel ratio question Yea, I have tuned quite a few engines with 8 o2's, and it is quite the eye opener to see what each individual hole does. But once you get them fairly balanced, then see those collector numbers come into balance as well, it's amazing how well the engine runs, especially up top

07-12-2017, 10:16 PM	#9
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: Air fuel ratio question If you use a FAST XFI system, you can use a distributor with a cam position sensor & put it in Sequential mode, and adjust each cylinder's air/fuel & timing. There is some power there. Could be suprising the difference in air/fuel ratio you see between cylinders. Change intake manifolds, you get to do it all over again. With my Hogan, I had less variation than with the single plane & elbow. More difference between the 2 tune ups than just that. And, I saw VERY little difference between my air/fuel ratio in the primary tube O2s, and in the collectors. I must be doing something wrong. LOL __________________ Ed Wright 4156 SS/JA

07-13-2017, 10:03 AM	#10
Ben Holt Member Join Date: Sep 2008 Posts: 142 Likes: 3 Liked 112 Times in 40 Posts	Re: Air fuel ratio question I didn't say that......I just said I have seen somewhere between .6 an 1.0 difference between the port and collector o2. Every combo is different. The OP just asked if the variation between the two is common. My answer is yes, it is common. But from what I've seen, once you get all 4 holes in the bank balanced out nice, the collector number starts to come around, as well, like you have found The sequential EFI stuff is really neat to fine tune the individual holes. I have really enjoyed messing with that, sounds like you have, too!