Would you anticipate any unusual O2 sensor readings by welding

[Evo160K]

18 mm, 27719-07, narrowband sensors (in the h-d evolution stock location) on Hooker's 2 into 2 Tuned Flow exhaust system headers?    These Hooker headers are stepped and have a metallic ceramic coating for heat control and increased exhaust gas velocity.  I'm thinking the step in the pipe might necessitate a sensor location change, but have no idea how to know before welding them in place.  How would you deal with that and any other issues you would anticipate?  Thanks very much.

[Steve Cole]

Before doing any welding in the stock location make sure that the sensor install into the pipe meets the BOSCH specification as HD did not and you will have more trouble getting them to work in an aftermarket pipe to begin with due to the lower backpressure and size of the exhaust.

[Pirsch Fire Wagon]

 

And - where possible, locate as close to flange within BOSH guidelines - Both should be as identical in location as possible by measurement and true right-angle

[Evo160K]

Steve, Whitetmw,
Thank you for the headsup, I appreciate it very much.

I've read pages D4 and D5 in the Bosch O2 sensor publication.  What other than the requirement for a minimum of 10 degrees from horizontal for drainage do you question about Harley's placement of their sensors?  I think I'm going to have a challenge finding a proper location for the bungs on my 1990 softail, particularly at a right angle. 

Steve, about your comment on backpressure and stepped pipe size , the headpipe diameter is the same as stock (the step up is about 10" from the head) and the mufflers are tuneable for backpressure, so I'm hoping I can meet the requirements.  Well it's an interesting winter project.  Thank you for any suggestions.
Thank you very much for your help.

[Steve Cole]

If you are not worried about hiding the sensor like HD was there are plenty of places that you can move them to meet the requirements. Just remember flow just after a short turn side radius is sometimes blocked. Another words there is little to no flow in that area. So the sensor if positioned in the "dead" area will not give good readings. Look around on your application and see what may work for you but it doesn't have to be just like HD's position to work properly. On the front cylinder see about moving around the pipe closer to the front frame tube and on the rear cylinder a lot of times you can come in from above the pipe and angle up toward the seat for a good position.

[Evo160K]

Steve,
Thank you for those suggestions.  If I weren't so hung up on the looks, I would drill through those, Hooker heatshields and put them where you suggest.  So far I can't do it.

Would you please take a look at the pictures of the sensor/bungs I'm using?  If I put them in/near Harley's location, would it be a mistake to trim the bungs to get an additional 1/8" or so of sensor exposure?  Thank you very much, Steve.

[attachment removed after 60 days by system]

[Steve Cole]

What you have in those pictures is never going to work properly. Lower RPM's are going to be really tough to get to work at all. You need to remember the Bosch specifications and follow them as close as possible if you are looking to be successful.

[Hilly13]

Evo this is what mine looked like for an example.

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[Hilly13]

Protrusion looked like this



[attachment removed after 60 days by system]

[Evo160K]

Hilly13,
Thanks for the pictures.  What model bike are those pipes on?

[Hilly13]

06 Dyna Evo, the positioning isnt perfect but it is way better than stock and seems to be ok for my needs......so far.

[Evo160K]

Hilly13, the sensor in the picture looks like it's in a straight bung.  Is that correct?  What are your needs, how do you use it?

[Hilly13]

Yes the bungs are straight, 90* to the pipe, the position they are in is not perfect for drainage nor the most optimum for the gas flow but as I stated before its way better than it was, the mufflers are SEII's with no wadding, the sensors as they were before simply were not sampling very well and hardly at all at low revs, my tune kept wandering and getting overly rich in the lower part of the map, this I overcame by reloading the cal every couple of weeks, it is now stable and have not had to reload since doing the bungs, however it does need vtuning again to fine tune the cal and I will get to it eventually.....one day.

[Evo160K]

Thanks for that, Hilly.  Just reinforces what Steve Cole has been saying about poor bung/sensor placement creating problems.