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crosstalking sensors

Fallguy

Fallguy

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Jun 15, 2015
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I have been looking around some different posts and there seems to be one particular fellow that goes by Doc that appears very adamant that there WILL be a sensor confusion and tuning will be a problem with a de-catted stock headpipe. I have a 2015 103 c.i.. that I put a de-catted headpipe in with Full Boar 3 1/2 slip-ons and the fl-vied's and a stage-1 air cleaner using stock a/c cover. So I rooted around in my headpipe I took off and it doesn't seem that the sensors are able to read the same head information because they are separated by the tubing for a few inches before they are in the common collector where the cat used to be located. From there it seems to be at least 8 inches further before the crossover pipe in which the larger portion of exhaust actually continues straight out into the muffler.
I switched to 2" baffles from the 2 1/2" baffles that I had ordered with the slip-ons (sounded awesome), but took away the bottom and mid quite noticeably.. I have my VIED's set at about 65% and have checked plugs after a couple long rides to see that they are no longer paper white, but a bit tan and gray now. It takes a bit longer for the back cylinder to cut out at lights and my low-midrange power feels considerably stronger than originally. The sound the pipes make is DEEP HARLEY and not sewing machine. lol
So the final comment on this new thread is I just don't feel or hear anything negative with the de-catted headpipe. If it was on a dyno with stock de-cat or true dual than maybe there is some small difference but I am pleased with it as it is. For now.
 
I was made aware of his information via this forum, too. I understand the idea and I'm not saying he isn't correct.... I do believe there is some cross talk, he says he has data to prove it.

I just received my de-catted head pipe from B & E Performance (Superflowmufflers.com) http://www.superflowmufflers.com/
and I'm hoping there won't be any major issues. Glad to know you are not having any.

As I was curious about your few inches of separation in the tubing before the collector, so I put a stylus pen in both O2 sensor holes to see just what was what.

No cat head pipe. Clearly seeing the separate tubes:
View attachment 7002

Stylus in Front cylinder O2 port - clearly inside the front tube:
View attachment 7003

Stylus in Rear cylinder O2 port- clearly outside the front tube:
View attachment 7004

As pictured, they are in separate tubes before the collector. So I wondered how long was the tube?
First: I stuck a tape measure down to the end of the front cylinder tube: 16 inches from the end of the head pipe.
Next: I stuck the tape measure down to the stylus in the front tube: 19.5 inches depending on how plumb my stylus was in the port.....
So..... the front O2 sensor is about 3.5 inches inside the tube.
Quite separated from the back cylinder O2 port, which is about 1 inch back from the front port.

See my pic with sharpie marks showing approx. length of the front tube from the front O2 sensor port center.... 3.5-4 inches, just to the seam.
View attachment 7005

As stated before, I do believe there is some crosstalk.... hopefully, it isn't bad enough to notice. Looks like you haven't. Sweet!

Since the O2 sensors actually measure temperature (if I remember correctly), I can see where their temperatures could be affected by the cat removal, but honestly, the distances haven't changed.. only the downstream cat is removed. Maybe the exhaust pulses cause some back draft down the separating tube????
 
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Your measuring was interesting to hear. If I had heard of this crosstalk thing before I did the install I would have looked through end with flashlight and a pencil sticking through each bunghole to see the placement but anyway, it seems like the cat just beyond the sensors would cause more pressures to bounce back at the sensors than the clear path for another foot or so into the new baffles in slip-ons. I hope your results are as positive as mine. It appears that tuning is important ( AFR & BAFFLES ) to have the correct exhaust velocity and no reversion or scavenging. Please post your progress as I look forward to hearing it.
p.s. I am looking at Wards Parts Works cylinder head fans for cooling now.
 
Fallguy said:
.......... it seems like the cat just beyond the sensors would cause more pressures to bounce back at the sensors than the clear path for another foot or so into the new baffles in slip-ons.

.
Click to expand...

My simple mind tends to agree with this........

I just bought his Max Performance 2 mufflers off eBay, tonight. Listening to them on youtube struck a nerve with me. And they're cheap. I used his "Best Offer" button to get them even cheaper!

Even though it's been said there isn't a need for a tuner if you don't mess with the intake/air filter, I agree the loss of back pressure will rob me of some low end grunt (especially, now that I've de-catted AND increased muffler flow). Maybe a tune will richen it up a bit to negate some of the lost grunt?
I plan on keeping the intake/filter stock without a tune.
 
The EFI system on our bike's has the ability to learn it's called adaptive learning regardless of what exhaust mods you make after the 02 sensors or air cleaner mods you do before the throttle body the system will learn and compensate as needed for the engine to run within the spec's of the tune flashed in the ECM
Will the engine require more fuel when you install a hi flow air cleaner yes but the ECM will learn and adjust for that the same go's for exhaust mod's But the system has it's limitations it's window of adjustment is only so large witch means if you want to go beyond basic exhaust and air cleaner mods you must adjust the parameters of the tune to take into account the change's made to the engine
That being said will the bike run ok with a de-catted head pipe and a stage 1 air cleaner with out a tune YES
Will the bike run better with a better tune flashed into the ECM YES because there is more to a tune then just adding some extra fuel
Plus the stock tune your Harley has from the factory is a conservative tune that runs on the lean side right form the get go to meet EPA standards
and Harley left some HP on the table to start with why do you think you can go to your local dealer and get a stage 1 flash it's not because of the slip-on's or the new air cleaner you could install a stage 1 flash on an otherwise stock bike and gain HP from just a tune alone this is just my .02 cents for what it worth
 
Fluffy said:
The EFI system on our bike's has the ability to learn it's called adaptive learning regardless of what exhaust mods you make after the 02 sensors or air cleaner mods you do before the throttle body the system will learn and compensate as needed for the engine to run within the spec's of the tune flashed in the ECM
Will the engine require more fuel when you install a hi flow air cleaner yes but the ECM will learn and adjust for that the same go's for exhaust mod's But the system has it's limitations it's window of adjustment is only so large witch means if you want to go beyond basic exhaust and air cleaner mods you must adjust the parameters of the tune to take into account the change's made to the engine
That being said will the bike run ok with a de-catted head pipe and a stage 1 air cleaner with out a tune YES
Will the bike run better with a better tune flashed into the ECM YES because there is more to a tune then just adding some extra fuel
Plus the stock tune your Harley has from the factory is a conservative tune that runs on the lean side right form the get go to meet EPA standards
and Harley left some HP on the table to start with why do you think you can go to your local dealer and get a stage 1 flash it's not because of the slip-on's or the new air cleaner you could install a stage 1 flash on an otherwise stock bike and gain HP from just a tune alone this is just my .02 cents for what it worth
Click to expand...

Fluffy, I agree with your excellent thought provoking summation! You made Interesting points.
Awhile ago I read that the ECM has an adoptive learning feature of pus or minus 6% taking into consideration all engine management possibilities. If intake mods are done and are within the +- 6% realm of the flash contained in the ECM (not nessecarily the stock ECM flash) the bike should run fine. It could be pointed out that performance modifications to the intake system with the stock ECM settings will work but may push the system too far to the edge of the 6% parameter not allowing self adjustability after that. I agree that a simple stage 1 flash to a stock bike would be beneficial.
It's wonderful that there are so many tuning options for us as riders and so much information to be had regarding modification.


Blues
 
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BluesBelly said:
Www.docsperformancetuning.com
Click to expand...
Thanks for the site information as it may be needed at some point. I have thought of a stage-1 flash possibly just for that little mmffff that it might like having things advanced a little. it appears the FL-VIED's are adding a bit of gas where needed. Post your upgrade results if you would so to hear how yours is coming along. Thanks
 
I installed my B&E Performance Max 2 mufflers today. Only have 10 miles on them. Performed great for those ten miles. Going on a Pediatric Brain Tumor Foundation ride tomorrow morning. Will have some varied throttle positions while riding in a group. I'll report back any hiccups. Fingers crossed.:cool:
 
Well described Fluffy! Catless on a Harley is a wonderful thing!!
 
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