DArnit! Why the hesitation at 2000rpm now?

[Pokageek]

Could this be from long-tubes not being tuned quite right? I don't remember having this before. It is only at 2k-2500 rpm and cold or warm engine. It seems more since the weather is cooler now. I remember them taking some fuel out of the tune right where it hesitates now when they programmed the 306 I had in there before this engine. Could that be it? Thanks in advance for ideas..

 

[Stanger007]

If the transport delay is off you'll see the car start learning incorrectly as it samples the exhaust at the wrong time. Try clearing the KAM (unplug negative cable and hold brake for a few seconds) and see if it goes away or is greatly reduced.

Are you still running EGR or have it disabled in tune?

Wes

 

[Black95GTS]

Long tube headers will affect the tune as they relocate the stock O2 location. I predict that doing as Wes suggested will fix the problem for a while, then it will re-appear as the computer attempts to adapt again.

You may want to think about tuning for the new 02 location.

Adam

 

[Pokageek]

Awesome. I hopes thats it. I will try it and see. No, I have no egr and it is tuned out; checked all vacuum and intake bolts. All my parts are basically new. And yes, To me, it does seem like the car has "adapted" or adjusted incorrectly.

 

[Pokageek]

Well. I tried it and it workd for a few minutes and went back to poping or hesitating (slightly nothing dramatic..but. Its not real bad but you just notice a huge "WAKE UP!" HELLO! after 2500 that you can tell its bogging at 2000-2500. I am going to have to send the chip back. Damit.

 

[Zero_chance]

Forgive this novice question in the field of tuning, but you can tune for the location of the O2?

 

[BlackVert]

yep, there is a table called the hego delay table, and it basically says that for a given rpm and load, how long to wait before reading the voltage at the o2 sensor

 

[Zero_chance]

Not to hijack the thread, but what would be the difference say between having shorty headers and long tube headers? Would long tubes require more of a delay? Less? Or am I reading that wrong? THis is just to satisfy my own curiosity.

 

[Bosko5.0]

Not to hijack the thread, but what would be the difference say between having shorty headers and long tube headers? Would long tubes require more of a delay? Less? Or am I reading that wrong? THis is just to satisfy my own curiosity.

On Lt's the O2's are farther back So you would need more of a delay.

 

[Black95GTS]

Not to hijack the thread, but what would be the difference say between having shorty headers and long tube headers? Would long tubes require more of a delay? Less? Or am I reading that wrong? THis is just to satisfy my own curiosity.

Long tube headers place the O2 sensor in the collector. Obviously, long tube headers have longer tubes. This puts the O2 sensor further down the exhaust pathway.

What happens is that the O2 sensor doesn't stay warm enough for optimum operation. More importantly it also changes the exhaust pulse coming out of the cylinder which confuses the computer even more. The combination of these two events will slowly FUBAR your computers adaptive algorithm.

So what you have to do is increase the HEGO Delay value, telling the computer that it will take your exhaust pulses longer then the stock setting to hit your O2 sensors. What this value is I don't know, I never went long tubes.

Short tube headers should be fine. Your car already comes with short tube headers from the factory, so the O2 sensor location barely changes.

Adam

 

[Pokageek]

Thanks Adam. I told that to SGS before the last tune. I don't know if it was done.