hey guys...

just a reminder because ive been tuning a few evo's lately on our dyno...

check for exhaust leaks... i had one evo ix... that was down slightly on power... afr's were where i liked them.... no knock, 100% octane rating...22psi or so...

just down 10whp or so to the others...

car had a CEL for the secondary o2.... which i was planning on adding an extender....

got off the dyno.. up on the lift... and there was a leak at the flex joint section of the custom 3" downpipe, before the high flow cat and secondary o2....

after it was tack welded shut, the code is now gone... this was obviously throwing my exhaust tip wideband reading off on the dyno...

so, im going to retune it, see where the afr's sit... i think we will make the 10whp or so back.

just a friendly reminder...

check those exhaust fittings and do boost checks..

cheers

cb

 

You damn well better!!!

 

Is a OPEN dump considered an "exhaust leak?". It is way before the cat, and I have not noticed a drop in boost. Please clarify.

The dump is supposed to add HP? If I don't plug it, am I losing HP? Or boost? If you have an "off road" or cat delete pipe, isn't the 2nd O2 worthless/useless anyhow?

 

What he was referring to was that my little exhaust leak before the secondary O2 sensor was throwing off the A/FR's and that this was proven because the secondary O2 sensor was throwing a code saying something was wrong. That's all. Since the A/FR's were off he was probably getting lower readings than what there was and could have leaned my car out a bit more for a little more whp.

And Yes, an open dump is better as well but it isn't even close to being considered an exhaust leak. I'm not sure if your were serious with that statement or just being sarcastic...Being a member with over 5,000 post I would have thought you knew the answer to that.

 

Bump for a good reminder. When you have a boost leak you lose a ton of potential.

 

I didn't know the answer to that, I was serious. I know about the back pressure "needed", and since I saw NO gains with my dump on the dyno, I was wondering if this wasn't hurting my HP #'s, thats all. Relax Faust, just trying to learn something new every day, and thought this might be it.

 

Can we call an "exhaust leak" a BOOST leak? I don't think they are the same. Or do they give the same properties/characteristics.

 

I am confused. Are we talking a boost leak being the same as an exhaust leak? Or are we saying an exhaust leak will mess up the AFR's when tuning? This I know. *scratches head*. Title is confusing.

 

Nope, boost leak is different.

 

I have had both, and in my case, the boost leak was way more detrimental to performance than the exhaust leak.

 

Thank you grubiaco, that's what I thought!

 

he's saying that an exhaust leak during tuning with a tailpipe wideband will lose you power due to the wideband reading wrong and your tune being made richer to compensate. if you were already tuned and get an exhaust leak later, you won't lose any power. it just throws the wideband off during tuning and causes you to need an excessively rich tune, that's all.

 

My car has a vband clamp on the turbine to exhaust housing that doesn't sit quite right, it resulted in an exhaust that definitely affected my wideband readings a bit (even my narrowband readings are off slightly)

Definitely fix any leaks you can before you try to tune anything, it just adds to the headaches..

This is the reason why I haven't done any real tuning on my car, just enough to get the car running well enough to drive it for the time being. Once the weather gets a little milder out I'm going to pull my downpipe and radiator and get the sucker seated properly and sealed.

 

/\ I know the vband you are talking about....it took a friend pusing up on the downpipe and holding the clamp in place, and me tightening it from the top to get it perfect.....

I will never touch it again....hopefully

 

i am assuming you can hear or smell it right?