Question about idle after new exhaust

[CARGUY40]

I got a straight pipe exhaust done on my car and I noticed on cold starts as my car starts warming up the idle is lower then it was before but once I start driving the car and it warms up more the idle goes back to where it use to be? Can this be from removing the catalytic converter?

 

[Jetronic]

your high idle is lower than it used to be? or the high idle is lower than the hot idle?

 

[OneEyeJack]

Cars are becoming a package deal. No mods, no adjustments. Don't touch. Today mods can cause problems by not running correctly. Soon there will be other consequences. You will be watched. It's for your own good. People that know will guide you.

 

[andyd]

No worries. All you need to do is to retro-fit a Holley 4 barrel with a manual choke.

 

[WANG]

A catless downpipe without a new tune seems quite likely to introduce some unique operating characteristics.

 

[horse123]

Did you tune it too? The ECU needs to be readjusted when you make a change that big.

 

[WANG]

Originally Posted By: OneEyeJack
Cars are becoming a package deal. No mods, no adjustments. Don't touch. Today mods can cause problems by not running correctly.


This has always been true. The only thing that has changed is the methodology used to compensate for said modifications. Ones and zeroes are responsible for fuel curve as opposed to machined brass. Ones and zeros handle the ignition curve instead of springs and weights. Ones and zeros handle all of the fuel air spark calibration. Ones and zeros can still be manipulated to suit our desires, and the execution of that manipulation is much simpler and more precise than what was available in the past. Today is a fantastic time to be alive for a motorsports enthusiast.

 

[CARGUY40]

Tune it? its a 1988 nissan 200sx 3.0 v6 bone stock besides the exhaust change.

 

[Clevy]

So it's a speed density fuel injection system. Or is it mass air.

Either way you'll see no power gain.

 

[SteveSRT8]

^^^Right, but a LOT more noise! And likely lower torque as well until the revs come up.

But regardless, the engine will need tuning if you want any real gains...

 

[Olas]

Originally Posted By: boostedtsiawd
I got a straight pipe exhaust done on my car and I noticed on cold starts as my car starts warming up the idle is lower then it was before but once I start driving the car and it warms up more the idle goes back to where it use to be? Can this be from removing the catalytic converter?


Where in the system did they place the straight pipe?

Does it replace the cat or any silencers?

Do you have one or two O2 sensors?

All those factors will make a difference to noise and drivability, it's probably best to rolling road and live map to suit the new characteristics to your prefrence.

 

[CARGUY40]

The catalytic converter was removed in place of a straight pipe and the o2 sensor is still there.

 

[surfstar]

How fast does it sound now?

and how bad does it smell at stop lights/signs?

talk about a win/win!!!

 

[threeputtpar]

If you want your idle speeds to go back to where they were, you'll need to add enough go-fast stickers to the windows to counteract the new exhaust