Running very rich (exhaust)

[viperkd77]

So lost. Here are 2 logs. One for cruise or closed loop. One for wot of open loop. I put on a 3inch catless xhaust in the fall. Got 20mpg before and now like 10mpg.

Previous mods were kn filter, custom intake pipe, mbc at 14psi, dump tube cut, bcs restrictor removal (before mbc).

since exhaust, in research of my problem ive replaced the 2g tb with a 1g tb and eliminates all boost leaks and have also got dsmlink (b/c i wanted it originally and...) to help see and eliminate this problem.

I've been advised that the exhaust is not causing this problem, but it is infact something else possibly. I actually lacked ground straps on the new exhaust that were on the stock exhaust. I replaced the one near the rear 02 (frame to clamp) just bc ive heard they were necessary (97 gsx a/t).

I am stumped. At wot, it seems more powerful with the exhaust. However, even if i let off the gas ever so slightly in cruise it runs awful (black smoke ,slow, boggy, eats gas). I was told that my fuel trims are decent at wot, but very rich at cruise and idle. I have no idea how an exhaust install can lead to this chaos. Maybe something happened in coincidence. Please help........

 

[SpeedAddict62]

What do you mean "dump tube cut"?

The reason I ask is if you are talking about cutting the BOV dump tube and no longer recirculating back into the intake, that could very well be causing your problem. For example, you let off the gas, the BOV opens allowing air to escape that otherwise would still be in the intake and that the engine still thinks is there. It injects enough fuel based on the signal from the MAF and you have a lot of fuel and not much air, and a very rich mixture. My friends and I tried this just for shits and giggles, and it would barely idle, bog down, run rich, etc. exactly like you describe.

So if you are dumping the BOV to atmosphere, recirculate it like it should be, and see if that solves the problem.

 

[viperkd77]

. i know that. The dump tube cut is something else. I am still recirculating....

 

[EclipseRacing99]

well if you are running rich at cruise and at idle is would look like you need to tune your car at cruise and at idle. adjust your fuel maps at cruise and at idle.

do you have a wide band o2?

 

[viperkd77]

how am i supposed to adjust my fuel maps at cruise and idle. DSmlink is only for openloop operation. No i dont have a wideband..

 

[EclipseRacing99]

your idle and cruise is your global scale. move it based on your stft and your ltft.

also try posting this on the dsmlink forums.

 

[viperkd77]

Maybe this will help, hvent look at this thread in a week or so, but ive established that my timing isnt off... Also. here are some new logs on the highway. Im still only getting like 13mpg on the ighway. It seems sometimes the car is smooth and clean exhaust smoke, but others it bogs and is horribly black, slow, etc. These two modes sortof kick in and kick out...??? This is basically how it has been since the ehxaust install. please help...

 

[EclipseRacing99]

you need to read the dsm link wiki on how to set your fuel trims. and post this on dsmlink to get advices on your logs.