Long tubes and O2 sensor placement

[BlackVert]

one thing i have heard about long tubes is that there is some question (or concern) that the O2 sensors might end up being far enough away from the engine that they might not get hot enough to consistently provide correct data. or that at stoplights, they might cool off enough to where they don't behave as expected.

i don't know whether this is a valid concern or a real problem or not, but i have heard people talking about it, so i figured i'd open the discussion up so that people who have more experience with long tubes than i have can weigh in with their thoughts and musings.

even though i had kooks long tubes on my 410 for a few months, i didn't get far enough in my tuning to be able to come to an informed opinion on the subject.

 

[Bosko5.0]

you have to adjust the exhuast pulse delay, it will fix the problem of them reading when they get cold.

 

[Stanger007]

I increase the exhaust pulse delay about 20% or so at the lower parts of the table to allow for the longer travel of reading of the exhaust pulse.

I haven't noticed the fuel trims drift much across quite a few cars I've tuned with longtubes. Your other option is to forced an open loop condition at idle if it comes to that but I wouldn't think so.

Also don't get confused with a cam with overlap, that can also throw you at idle as some fresh air goes in the cylinder and leaves with the exhaust charge.

Wes

 

[Pokageek]

Subscribing

 

[final5-0]

I increase the exhaust pulse delay about 20% or so at the lower parts of the table to allow for the longer travel of reading of the exhaust pulse.

I haven't noticed the fuel trims drift much across quite a few cars I've tuned with longtubes. Your other option is to forced an open loop condition at idle if it comes to that but I wouldn't think so.

Also don't get confused with a cam with overlap, that can also throw you at idle as some fresh air goes in the cylinder and leaves with the exhaust charge.

Wes

Yes ... Yes ... Yes ... What Wes said

and ... I'll add a thought or two

Before I go very far ... My cam is rather narrow at 109 lsa

I suspect that has a lot to do
with some of the things I've seen from fooling around with my little GT

I played around with that exhaust pulse delay and found NOTHING I did
with it made any difference ... I could notice

I will say I got my nb O2's in the default location
and
I got a bung for my wb O2 in each collector as well

I did see my O2's cooling a bit at long stop lights
but
From talking to other self tuners with LT's

Some had no issues
and
Some had the prob much worse than I did

Why ... I can't be certain

I did not notice it for a long time if the truth be made known

It was when I got down to ... REALLY ... fine tuning drivability issues ...
That was when I noticed it happening

Over a long period of time ... the tune at idle would drift a bit
so
I finally forced Open Loop at idle to make things stabilize

anyway ... there you go

Grady